Chapter II

2. Literature Review
 Literature Value of Sweet Potatoes
 Health Benefits of Sweet Potatoes
 Uses of Sweet Potatoes
 Systematic Classification of Sweet Potato
 Orange fleshed sweet potato
 Purple Fleshed Sweet Potatoes
 Noodles
 Sweet Potatoes Noodles
 Sun Drying
 Oven Drying
 Microwave Drying
 Chemical composition of Sweet Potatoes
 Physico-Chemical Properties of Sweet Potatoes Flour
 Moisture Content
 Sugar Content
 Bulk Density
 Color Analysis
Literature Value Sweet Potatoes
The sweet potato (Ipomoea batatas) belongs to the Convolvulaceae or morning glory family and
is dicotyledonous. Typical of this family, the distinguishing characteristics of the sweet potato
include: the presence of latex in its sap, trailing stems (some species are erect, others climbing),
bicollateral vascular bundles, simple leaves arranged alternately around the stem, complete
flowers (superior pistil, five stamens, and a trumpet-shaped corolla), fruit which is a capsule and
seed containing an embryo with folded cotyledons.' The fleshy sweet potato storage root (not a
tuber) does not have eyes or scars as found on some other roots and tubers, but it does possess
the ability to develop adventitious buds on sprouts or vine cuttings which is advantageous in
reproducing the crop vegetatively. Sweet potato is not grown commercially from seed because it
cross pollinates readily and each seed from a single plant may be different from any other seed.
There are two important types of sweet potatoes grown commercially. When cooked, one has a
seemingly dry, mealy flesh; the other a flesh of a soft, moist, sugary consistency when cooked.
The latter are often sold as "yams", but the true yam is a monocotyledon of the genus Dioscorea.
Sweet potato (Ipomoea batatas) was the only food crop common to tropical America and
Polynesia before the discovery. As such, it has raised a long discussion on which of the two
regions is its place of origin and how its early dispersal occurred (Yen, 1974). The recent
discovery in coastal Peru of sweet potato tubers dating from 10,000 BC (Engel, 1970) settles the
question of the origin, as this date by far antedates any agricultural development in Polynesia.
However, it should be considered that, like all other plants cultivated in the coastal region of
Peru, sweet potato was introduced from elsewhere, possibly from the north, the coastal area of
Ecuador and Columbia, where close wild types have been found (Martin et al., 1974), or from
across the Andes, like Canna edulis and other crops. At the arrival of the Europeans, the sweet
potato was known in all Tropical America, with an important area of diversity around the
Caribbean. Oviedo, writing in 1530, reports that several varieties he had seen in the early days of
the Conquest were already disappearing. The spread of the sweet potato to the Old World was
quite rapid; it was introduced in Spain, after several failures, as living plants before 1550. It is
not known how it reached Africa, whether from Spain or from tropical America. A report that
sweet potato was grown in San Thome in 1520 seems doubtful (Mauny, 1953). More reliable
information shows that it was widely cultivated by the end of the seventeenth century in West
Africa, and a century later all over the tropical areas of the continent. The introduction to
Polynesia, as discussed above, has not been properly explained. It could have been accidentally
transported in one of the Peruvian rafts lost in the Central Pacific, which reached Polynesia
where the crop was established by Indo-Americans and developed later on by Polynesians. It has
been proposed also that the sweet potato may have been taken to Polynesia by one of the Spanish
expeditions that visited the area starting from Peru in the sixteenth century. It was taken to China
in 1594 and after a famine in Fukien, it later became an important crop. Sweet potato was
introduced early to Japan from Okinawa and cultivated and adopted in the southern region up to
37°N.
Sweet potatoes require at least 120 frost-free days for optimum growth and are of minimum
commercial importance where mean summer temperatures are lower that 20°C. They thrive in
hot weather, but little or nor growth occurs when soil or air temperatures are below 16°C.
Growth appears to be optimum when soil temperatures are near 20°C and air temperatures near
30°C. Sweet potatoes tolerate drought conditions, but produce best quality and yields when
moisture stress is minimal.
Sweet potato is a major world crop with over 135 million metric tons (t) produced annually
(Table 1). The annual U.S. production is 622 t, over half of which is produced in the states of
North Carolina and Louisiana. Sweet potatoes (and other root crops) are considered by many to
be inferior or "poverty food" but 17.6 million are produced annually in the "Developing World"
where its full potential is yet to be realized."
Sweet potato research and extension activities are major thrusts of the International Institute of
Tropical Agriculture (Nigeria), the Asian Vegetable Research and Development Center (Taiwan),
and more than a dozen Agricultural Experiment Stations in the U.S. Sweet potato improvement is
a major research activity since this crop mutates readily. New cultivars are released frequently to
satisfy specific needs. The U.S. markets generally prefer the moist- fleshed "yam-type" sweet
potato while many other areas of the world prefer the hard, dry, white-fleshed cultivars. Two
cultivars, Jewel and Centennial, currently dominate commercial production in the United States.
•A. E. Purcell, W. M. Walter, Jr., and L. G. Wilson,1989, Sweet Potatoes .
Sweet potato, with a global annual planting area of approximately 9 million ha, is the second
most important tropical root crop. It is widely adapted, being grown in more than 110 countries.
Early maturing varieties grow in 3-4 months. It is hardy and has multiple uses. Both roots and
foliage are edible and provide energy and nutrients in diets. Distinct quality types have different
uses, with orange-fleshed sweet potato being valued for its extremely high provitamin A content,
and other types used in varied fresh and processed forms. Sweet potato is easily bred, as true
seed is easily obtained and generation cycles are short. There are five objectives of this review.
The first objective is to briefly describe recent production and utilization trends by region; the
second is to review knowledge about the origin and genetic nature of swee tpotato; the third is to
review selected breeding objectives. The fourth objective is to review advances in understanding
of breeding methods, including: (i) generation of seed through polycross nurseries and controlled
cross breeding; (ii) a description of a new accelerated breeding ap- proach; (iii) recent efforts to
systematically exploit heterosis; and (iv) new approaches of genomic selection. The fifth
objective is to provide information about variety releases during the past 20 years in West, East
and Southern Africa, South Asia, East and South-east Asia, China and the Pacific.
Swee tpotato is used in a variety of ways for food, feed and processed products, with the
principal uses varying by region. The literature on nutritional value of cooked and fried sweet
potatoes as well as processing sweet potato into food products such as bread, ready-to-eat
breakfast, French fries, syrup, starch and beverages was comprehensively reviewed by Woolfe
(1992), Bovel- Benjamin (2007) and Padmaja (2009). In developing countries, the crop is mainly
grown for homestead food and feed use and to sell to local markets for fresh consumption. Use
of both vines and roots for pig feeding is important in China, Vietnam and Papua New Guinea
(Peters, 2004). Padmaja (2009) provides details on use of the crop for cattle, poultry and fish
feed.
All sweet potatoes used both as human food and as animal feed are called 'dual purpose' sweet
potatoes. Dual-purpose sweet- potatoes should have high foliage yields, because these are mainly
used for sweet potato-based silage and high-protein supplements (fodder) for livestock (Scott,
1991;8 Zhang et al., 1993; León-Velarde and de Mendiburu, 2007). However, there may be a
contradiction between the nutritional value for human food and the demand for extremely high
digestibility by the feed industry (Zhang et al., 1993), so that consideration should be given to
breeding varieties exclusively for animal feed for areas where that is its dominant use. In China,
much sweet potato is also used in starch noodle production, and use for production of distilled
spirits is common in East Asia. Purple-fleshed types, high in anthocyanin, are increasingly
popular in China and Japan, used fresh or in a variety of processed snacks and as a source of
natural food colouring (Timberlake and Henry, 1988; Gilbert, 2005; Liu, 2008; Ma, 2010).
Awareness of the high nutritional value of sweet potato is driving increasing consumer demand
for the crop among health- conscious consumers in the USA and Europe (USDA, 2015). Orange-
fleshed sweet potato (OFSP) can be used effectively to combat vitamin A deficiency (VAD)
among vulner able populations (Low et al., 2007; Hotz et al., 2012). The leaves of sweet potato
have nutritive values comparable to common dark-green leafy vegetables (Ishida et al., 2000;
Bovel-Benjamin, 2007) and leaves, including shoot tips and petioles, are an increasingly popular
green vegetable in some regions of China and important in parts of Africa. Ornamental sweet
potatoes with strikingly varied foliage are commercially popular in the USA (Barnes and
Sanders, 2012) and South Korea (Yeong-Sang Song, Korea, 2013. personal communication).
To our knowledge, there is no significant use of sweet potato starch in textile, paper, ply- wood
and pharmaceuticals. The crop was traditionally a food security crop (Jia, 2013). It retains this
role in many parts of the world, because it: (i) is high yielding: (ii) needs low amounts of water
per unit of food and energy (see section 'Drought and other abiotic stresses'); (iii) provides
relatively good yields under poor input and marginal soil conditions; and (iv) exhibits wide
adaptability to climates, farming systems and uses (Diop, 1998; Hijmans et al., 2002; Jiang et al.,
2004). All parts of the plant (roots, leaves and shoots) are edible. More over, the crop produces
more edible energy per unit area and time (194 MJ/ha/day) than any other major food and it can
support more people per hectare than any other crop (Norman et al., 1984; Woolfe, 1992). There
are efforts investigating the use of sweet potato in bioethanol production in the USA (Estes,
2006, 2009) and China (Liu et al., 2010; Wang et al., 2013). On the basis of cur rent technology,
1 t of bioethanol can be produced from approximately 8 t of fresh sweet potatoes (Qiu et al.,
2010).
Two major quality classes of sweet potato for fresh consumption are generally recognized
(Martin and Jones, 1986; Kays et al., 2005). The so-called 'dessert types' are high in B-carotene,
have relatively low dry matter content (<30%) and moist texture, with a high flavour impact due
to sweetness and aroma. 'Staple types' typically lack B-carotene, have relatively high dry matter
content (>30%) with drier texture, and have lower flavour impact due to lower sweetness and
aroma. A third quality class was recently coined by Tumwegamire et al (2011a), namely 'OFSP
dry and starchy' also called 'sabor simple in Latin America. These are OFSP varieties, high in ẞ-
carotene, but with staple attributes such as high dry matter. Nearly all new OFSP varieties bred in
SSA are 'OFSP dry and starchy' to meet adult taste preference in SSA. This new OFSP type
might also be attractive for markets in South America and South Asia. Sweet potato breed ing
and seed programmes are largely sup- ported through the public sector, driven to a varying extent
by policies and to a minor ex- tent by the needs of industry.
Currently significant investment in sweet potato breeding is directed towards the development of
adapted, high-yielding OFSP varieties to be used for combatting VAD among vulnerable
populations in SSA. These investments are additionally supported by 'going-to-scale'
disseminations of OFSP varieties in SSA. We assume that the OFSP fraction of the total swee
tpotato harvested area in Uganda is still low (around 5%), whereas the OFSP in Mozambique is
22% (ΤΙΑ, 2012) of total sweet potato production, so that in the medium term Mozambique
could be the first country in SSA with significantly lowered VAD prevalence due to consumption
of OFSPs. The general perception of sweet potato as a 'poor person's crop' is changing in SSA
towards a 'food security and health crop'. So far, there are no compar- able investments in sweet
potato breeding in South and South-east Asia, in spite of very high VAD prevalence in these
mgions (UN-SCN, 2004). An important factor underlying in- creased investment in sweet potato
breeding in SSA was the biofortification programme of Harvest Plus (Pfeiffer and McClafferty,
2007), which is linked to the Agro Salud and Biofort programmes in Latin America. However,
sweet potato is now of minor importance as a food crop in the Americas.
•Robert O. M. Mwanga,Maria I. Andrade,Edward E Carey and Jan Low , October 2017 ,
Sweetpotato (Ipomoea Batatas L.)

Health Benefits of Sweet Potatoes

Sweet potato benefits are derived from its high carbohydrate content, making it an excellent
energy source, as well as its high levels of fiber, B vitamins, vitamin A, vitamin C and minerals,
such as potassium and magnesium. It can prevent diabetes, cancer and heart attack, as well as
improve intestinal health and increase muscle mass.
Furthermore, sweet potatoes have a low fat content and are a great source of antioxidants, such
as beta- carotene and anthocyanins. These help to protect the body's cells against the effects of
free radicals, preventing premature aging.
Sweet potatoes vary in color and can be white, cream, orange or purple, all which contain
different flavors and nutritional composition. Purple sweet potatoes have a higher amount of
anthocyanin-type antioxidants and orange sweet potatoes have a higher level of beta-carotene,
for example. Sweet potatoes can be consumed boiled or roasted, but can also be used as a base
for mousses or turned into flour for breads and cookies.
•Tatiana Zanin, October 2023 ,9 Benefits of Sweet Potatoes (plus Nutritional Info & Recipes)
The main health benefits of sweet potatoes are:
1. Preventing premature aging
Sweet potatoes, especially the orange ones, have excellent amounts of beta-carotene, which are
converted in the body into vitamin A. Furthermore, as they are rich in vitamin C (a powerful
antioxidant that protects the body's cells against inflammation and free radicals), sweet potatoes
can promote firmer, wrinkle-free skin.
2. Maintaining gut health
Because it is rich in soluble and insoluble fiber, especially when cooked with the skin, sweet
potatoes help to add bulk to the stool and can stimulate bowel movements, combating
constipation. Check-out other high-fiber foods you can incorporate into your diet. Furthermore,
sweet potatoes function as a natural prebiotic, as they are a source of food for the beneficial
bacteria in the intestine. This helps to keep intestinal flora within normal levels, which can treat
and prevent constipation.
3. Preventing diabetes
Despite having good amounts of carbohydrates, sweet potatoes are also rich in fiber, which
means they end up having a low glycemic index. This can help to reduce the speed at which
sugar is absorbed after meals, preventing blood sugar spikes. This property of sweet potatoes is
essential for preventing diabetes, but it can also be recommended, in small quantities, for those
who already have the disease.
4. Promoting muscle mass gain
Sweet potatoes are a great source of energy and are therefore widely consumed by those who
exercise or physically exert themselves regularly Because of its high fiber contents, sweet potato
carbohydrates are released gradually, making it a great option for those who need energy for long
periods of physical activity.
5. Promoting weight loss
Sweet potatoes can help with weight loss, as they are high in fiber, which increases the time it
takes for food to digest. Food remains in the stomach for longer, keeping you fuller for longer
and reducing overeating.
6. Preventing heart disease
Sweet potatoes, especially purple ones, are rich in anthocyanins, a type of antioxidant that
improves blood vessel functioning. These can reduce the formation of fatty plaques in arteries
and reduce "bad" cholesterol levels in the blood, preventing diseases such as stroke, heart attack
and atherosclerosis. Furthermore, because of their high potassium levels, sweet potatoes also
help eliminate excess sodium from the body through urine, preventing high blood pressure.
7. Strengthening the immune system
Because it contains high amounts of vitamin C, beta-carotene and anthocyanins, sweet potatoes
have excellent antioxidant action in the body. This can boost immunity and prevent diseases such
as flu and colds, in addition to promote wound healing.
8. Preventing some types of cancer
Sweet potatoes have excellent amounts of fiber, which is important for strengthening the
beneficial bacteria in the intestine and maintaining the balance of the intestinal flora. This
balance of bacteria is one of the important mechanisms for preventing bowel cancer.
Furthermore, sweet potatoes help prevent other types of cancer, such as prostate and breast
cancer, as they are rich in antioxidants such as vitamin C, beta-carotene and anthocyanins that
protect cells against free radicals.
9. Promoting visual health
Sweet potatoes are rich in beta-carotene and anthocyanins, which are powerful antioxidant
compounds that work to prevent vision loss and help maintain eye health.
•Tatiana Zanin, October 2023 ,9 Benefits of Sweet Potatoes (plus Nutritional Info & Recipes)

Sweet potato may offer a variety of health benefits.

Here are some of the ways in which they may be beneficial to person's health:
• Improving digestion and regularity: The fiber content I sweet potatoes can help prevent
constipation and promote regularity for a healthy digestive tract.
• Protects Vision: Beta carotene, which is essential for eye health, is plenty in sweet potatoes.
Eating foods rich in beta-carotene, such as orange-fleshed sweet potatoes, may help prevent this
condition. Purple sweet potatoes also known to have vision benefits.
• Supports Cardio vascular health: The anthocyanins present in sweet potatoes are also associated
with anti-inflammatory effects that reduce the risk of heart disease. Additionally, the fiber in any
vegetable reduces cholesterol, while the high potassium levels of sweet potatoes keep blood
pressure down.
• Reduced oxidative damage and cancer risk: Diets rich in antioxidants, such as carotenoids, are
associated with a lower risk of stomach, kidney, and breast cancers. The sweet potatoes potent
antioxidants may reduce your risk of cancer. Purple sweet potatoes have the highest antioxidant
activity.
Sweet potatoes are rich source of vitamin A and potassium.
They also provide some calcium,iron and magnesium.
The health benefits of vitamin ad minerals present in sweet potatoes are as follows:
•Vitamin C : This antioxidants may decrease the duration of the common cold and improve skin
health.
•Potassium : Important for blood pressure control, this mineral may decrease risk of heart
disease.
•Vitamin E : This powerful fat-soluble antioxidant may help protect your body against oxidative
damage.
•Vitamin B5 : Also knows as pantothenic acid, this vitamin is found to some extent in nearly all
foods.
•Manganese : This trace mineral is important for growth, development, and metabolism.
•Fiber : Sweet potatoes are rich in fiber, a nutrient that bulks up food, keeping you full longer.
Fiber also keeps your bowels healthy and lowers cholesterol. A medium sweet potato baked in its
skin has 4 grams of fiber, more than a packet of instant oatmeal.
•Complex Carbohydrates : Sweet potatoes are made of complex carbohydrates (energy) that are
released at a steady pace for a constant source of vitality, so no sugar highs or lows to worry
about.
•Low in Calories : A medium sweet potato (2 inches in diameter and 5 inches in length) baked in
its skin is only 103 calories. It's the all-natural pack - managing your weight just got easier!
• Antioxidants: Sweet potatoes are high in antioxidants compared to other vegetables.
Antioxidants help reduce your risk of chronic disease such as cancer and cardiovascular disease.
• Healthy vision - sweet potato has vitamin A which helps us to have great vision.
• Immunity - it supports our immunity in providing growth to other bodily functions including
our communication.
• Reduce blood pressure and stroke risks - they contain potassium and magnesium which helps
with blood pressure support in reducing blood pressure and strokes.
• Lower LDL cholesterol - the sweet potato can help in reducing the bad LDL cholesterol as well
as decrease some heart disease, obesity and type 2 diabetes.
• Supports longevity - its orange colour and beta-carotene have antioxidants that defend against
free radicals that can damage cells.
Sweet potatoes are a low-glycemic food that is high in fiber and can absorb glucose in the
bloodstream slowly, preventing blood sugar increase. Did you know that boiled sweet potato has
the lowest glycemic index of 44 and if baked for 45 minutes the glycemic index rises to 94.
•Sonia Bhuyan , Siddhanta Mishra , June 22 , Sweet potato: It's Nutritional Factor and Health
Benefits
Sweet potato may offer a variety of health benefits. Here are some of the ways in which they
may benefit a person's health:Improving insulin sensitivity in diabetes: In one 2008 study Trusted
Source, researchers found that an extract of white skinned sweet potato improved insulin
sensitivity in people with type 2 diabetes. Earlier, in 2000, laboratory rats Trusted Source
consumed either white skinned sweet potato or an insulin sensitizer, called troglitazone, for 8
weeks. The levels of insulin resistance improved in those that consumed the sweet potato.
However, more studies in humans are necessary to confirm these benefits.
The fibre in sweet potatoes is also important. Studies have found Trusted Source that people who
consume more fibre appear to have a lower risk of developing type 2 diabetes.A 124 gram (g)
Trusted Source serving of mashed sweet potato, or around half a cup, will provide about 2.5 g of
fibre. The 2015-2020 Dietary Guidelines for Americans Trusted Source recommend that adults
aged 19 years and above consume 22.4 g to 33.6 g of fiber each day, depending on their age and
sex.
Maintaining healthful blood pressure levels: The American Heart Association Trusted Source
(AHA) encouraged people to avoid eating foods that contain high amounts of added salt, instead
of consume more potassium-rich foods to maintain a healthy cardiovascular system. A 124g
serving of mashed sweet potato provides 259 milligrams Trusted Source (mg) of potassium, or
around 5% of the daily require Reducing the risk of cancer.
Sweet potatoes are an excellent source of beta-carotene. This is a plant pigment that acts as a
powerful antioxidant in the body. Beta-carotene is also a pro-vitamin. The body converts it into
the active form of vitamin A.
Antioxidants may help reduce Trusted Source the risk of various types of cancer, including
prostate and lung cancer. Antioxidants such as beta-carotene can help prevent cellular damage
caused by unstable molecules called free radicals. If levels of free radicals in the body get too
high, cellular damage can occur, increasing the risk of some conditions. Obtaining antioxidants
from dietary sources may help prevent conditions such as cancer.
Improving digestion and regularity: The fibre content in sweet potatoes can help prevent
constipation and promote regularity for a healthy digestive tract. Also, multiple studies Trusted
Source have linked high dietary fibre intake with a reduced risk of colorectal cancers.
Protecting eye health: As mentioned above, sweet potatoes are a good source of pro vitamin A in
the form of beta-carotene. After the age of 18, the Dietary Guidelines recommend an intake of
700 mg of vitamin A per day for women and 900 mg per day for men. Vitamin A is important for
protecting eye health.
According to the Office of Dietary Supplements Trusted Source (ODS), a baked sweet potato in
its skin will provide around 1,403 mcg of vitamin A, or 561% of a person's daily requirement.
Vitamin A also acts as an antioxidant. Together with other antioxidants, it can help protect the
body from a variety of health conditions.
Boosting immunity: One 124g serving Trusted Source of sweet potato provides 12.8 mg of
vitamin C. Current guidelines recommend a daily intake of 75 mg of vitamin C for adult women
and 90 mg for adult men.
A person who consumes little or no vitamin C Trusted Source can develop scurvy. Many of the
symptoms of scurvy result from tissue problems due to impaired collagen production.
Vitamin C also supports the immune system and enhances iron absorption. A low vitamin C
intake may increase a person's risk of iron deficiency anaemia.
Reducing inflammation: A rodent study Trusted Source from 2017 suggested that an extract of
purple sweet potato colour may help reduce the risk of inflammation and obesity.
Sweet potatoes contain choline Trusted Source, a nutrient that helps with muscle movement,
learning, and memory. It also supports the nervous system. A 2010 study found that taking high
dose choline supplements helped manage inflammation in people with asthma.
However, this does not necessarily mean that choline from sweet potatoes will have the same
impact.
•Jajhatsabaila, Singheshwar, Madhepura and Bihar, 2022,
HEALTH BENEFITS OF SWEET POTATOES: A SCIENTIFIC REVIEW

Uses of Sweet Potatoes

Sweet potato is used in the production of traditional noodles, vermicelli, thickening agents, or
converted intosugar syrups, which are used in malt processed food products. The sweet potato
starch and sugar are also utilized in the production of fuel , alcohol, monosodium glutamate,
microbial enzymes, citric acid , latic acid and other chemicals. In Japan the orange and purple
fleshed sweet potatoes have been used commercial products of nature beta-carotene and
anthocyanin pigments in beverages and other food products.
Sweet potato puree have also been used as ingredient in formulated fruit and vegetable juice.
However, heat treatment in sweet potato puree processing gelatonizes starch and produces thick
slurry with cooked flavor, which may not be preferred in several juicy products.
In large-scale production of French fries, partially fried products are frozen for distribution to
institutional and retailed consumers. Good quality fries could be produced by blanching the strips
in 60% sucrose solution for 4-5 minutes or 3 minutes in boiling water containing 0.25% sodium
acid pyrophosphate (SAPP)and 0.25% calcium chloride. Texture properties of the frozen French
fries are affected by root storage and the problem can be overcome by calcium treatment and
low-temperature blanching.
Sweet potato is utilized in a lot of uses in the household feeding and food industries. It is
considered as a resource of functional foods because of its high contents of physiologically
active compounds such as vitamin A,C,E, thiamin, riboflavin and niacin, as well as it contains a
good amount of minerals and essential amino acids and therefore it can be substituted for wheat
flour in the preparation of various bakery products. This help in increase the nutritive value of
product with lowering the gluten level, consequently prevent Celia disease in people who suffer
from allergies to gluten.
Several studies reported that sweet potato flour is an excellent source of phytochemical
constituents containing anthocyanin and phenolic acids (such as caffeic , chlorogenic ,
monocaffeoylquinic , dicaffeoylyuinic and tricaffeoylyuinic acids) and is superior to other
vegetables. These biologically active compounds possess multifaceted action including
antioxidation , antibacterial , antimutagenicity, anti-inflammation , anti-diabetes and
anticarcinogenesis.
.*G.Padmaja , January 2009 , Uses and Nutritional Data of Sweet potato , DOI : 10.1007/987-1-
4020-9475-0_11

Systematic Claassification of Sweet Potato

 Kingdom - Plantae
 Division - Angiosperms
 Clade - Asterids
 Order - Solanales
 Family - Convolvulaceae
 Genus - Ipomoea
 Species - batatas
 Botanical Name - Ipomoea batatas ( L. ) Lam.First
published in Tabl.Encycl.1:465(1793)
 Common Name - Sweet – potato (orange, purple)
 Myanmar Name - Kazun – u (ကန်စွန်းဥ)

Orange fleshed sweet potato

Orange fleshed sweet potato is now emerging as an important member of the tropical tuber
crops. It is having a great possibility for being adopted as regular diet of the consumer food chain
to tackle the problem of vitamin A deficiency. Apart from cheap source of energy, it is an
excellent source of the B-carotene (Low et al., 2007) and is generally well accepted by young
children (Wu et al., 2009 and Tumuhimbise et al., 2009) With the introduction of a large number
of orange fleshed varieties having high ẞ-carotene content ranging even up to 20-30mg per 100g
(Padmaja et al., 2012) [35] In addition to being rich in ẞ- carotene, orange fleshed sweet potato
contains significant amounts of protein, fat, carbohydrate, dietary fiber, zinc, potassium, sodium,
manganese, calcium, magnesium, iron and vitamin C and some phytonutrients (Anita et al., 2006
and Mills et al., 2009), A 100-150 g serving of boiled tubers of orange-fleshed sweet potato can
supply the daily requirement of vitamin A for young children which can protect them from
blindness (USAID, 2015)
It is also reported that one medium sized orange fleshed sweet potato can provide about twice the
B-carotene needed for the recommended daily requirement of vitamin A. The roots are usually
consumed after processing like boiling, baking or making fried chips (Vimla et al., 2011)
Because of their nutritional qualities, sweet potatoes were selected as one of the food tested for
long term space travel (Wilson et al., 1998). Therefore, orange fleshed sweet potato is a staple
food that can provide a supply of vitamin A and energy to people in both developing and
resource-poor developing countries (Low et al., 2009 and Mitra, 2012).
It is the most suiting as biofortified crop to combat malnutrition in small and marginal farming
community (Kidane, 2013) Orange fleshed sweet potato tubers are also a good source of energy,
easy to cultivate, vegetatively propagated, and fairly drought resistant (Hagenimana et al., 2001).
These characteristics make orange fleshed sweet potato an excellent food security crop. These
are less labor intensive than most other staple crops and can be planted over a broad range of
time without considerable yield loss (Woolfe, 1992).
Thus, there is a great possibility of this subsistence crop for being adopted as regular diet of the
consumer food chain to supplement as an alternative staple food source for the resource poor
farmers in the era of extensive population growth and nutrition crisis (Low et al., 2007). There
are a surprising number of nutrients responsible for the health benefits of orange fleshed sweet
potato tuber. Among these some are antioxidants, anti-inflammatory nutrients and blood sugar-
regulating nutrients (Whfoods, 2014). Being rich in ẞ-carotene, the orange fleshed sweet potato
is gaining importance as the cheapest source of antioxidant having several physiological
attributes like anti-oxidation, anti-cancer and may help in protection against liver injury and
coronary heart disease (Choi et al., 2009, Mei et al., 2010 and Grace et al., 2015).
Vitamin A deficiency is caused by a habitual diet that provides too little bio available vitamin A
to meet physiologic needs. Orange-Fleshed Sweet Potato is now emerging as an important
member of the tropical tuber crops having great possibility for being adopted as regular diet of
the consumer food chain to tackle the problem of vitamin A deficiency. Apart from cheap source
of energy, Orange-fleshed sweet potato is an excellent source of the B-carotene. This crop is also
gaining importance as the cheapest source of antioxidant having several physiological attributes
like anti-oxidation, anti-cancer and may help in protection against liver injury and coronary heart
disease. Orange fleshed sweet potato is the most suiting as biofortified crop to combat
micronutrient malnutrition in small and marginal farming community.
Gitanjali and Dr . Salar Lakhawat , December 2018,Review on orange fleshed sweet potato:
A miracle crop to reduce Vitamin A deficiency

Purple Fleshed Sweet Potatoes

Purple sweet potato (Ipomoea batatas L.) is one of the varieties that has the characteristics of a
purple color on the tubers. The purple color of sweet potatoes appears caused anthocyanin
pigments which have antioxidant properties. Haedersyah et al stated that the carbohydrate source
in the form of oligosaccharides found in sweet potatoes is a carbohydrate beneficial for the
growth of probiotic bacteria. Arifin noted that LAB growth in purple sweet potato extract
medium had the highest total increase in LAB compared to white and yellow sweet potato
varieties. Arfiani stated that the inulin content of the purple sweet potato variety was 3.9% which
had a higher percentage compared to the yellow sweet potato variety at 3.6% and the white sweet
potato variety at 3.2%. Therefore, the function of probiotics will be more optimal through the
addition of prebiotics simultaneously to produce a product called synbiotic.
The addition of purple sweet potato with the proper concentration as a source of prebiotics is
expected to produce efficient fermentation products and improve feed quality, namely increasing
the protein content of fresh fish silage due to the good symbiotic relationship between lactic acid
bacteria and purple sweet potato, of science and technology in the field of animal husbandry.
•Muhammad Zulfikar Fikri¹, Zaenal Bachruddin", Asih Kurniawati¹ and Chusnul Hanim¹, 2021 ,
The Effect of the Purple Sweet Potato (Ipomoea Batatas L.) on the Fish Waste Silage
Composition
Purple sweet potato is a vine that grows a lot in Indonesia and is used in various local food
preparations because it contains high nutrients. Objective: to review the benefits of various
processed foods from purple sweet potatoes in increasing nutritional intake. Method: a literature
review of published articles from Science Direct, PubMed, Neliti, and Google Scholar, with 25
shortlisted articles. Purple sweet potatoes contain nutrients that can replenish daily energy
sources such as carbohydrates, fats, and proteins. Other ingredients include high anthocyanins,
fiber, vitamins A, B12, and C, and minerals; Ca, Fe, Mg, K, and Zn. Purple sweet potatoes are
used for traditional and modern food preparations. Some of these processed foods are biscuits,
sponges, brownies, snack bars, fit bars, noodles, waffles, flaky cracers, pasta, croquettes, and
MP-ASI. Conclusion: the benefits of processed purple sweet potato foods in various forms
contribute to adequate nutritional intake, the importance of a good processing process, because
the heat process will affect its nutritional content.
Purple sweet potato (PSP) (Ipomoea batatas L. Poir) is a vine that grows a lot in Indonesia. The
quality of sweetness is just right if it is harvested according to its timeliness. So it is widely used
in various preparations because it contains many nutrients. The diversity of local Indonesian food
is the gateway to a diverse diet. By eating a varied diet, people can get all the nutrients they need
and reduce the risk of stunting in children because their nutritional intake has been met. Local
food consumption supports biodiversity conservation by encouraging communities to protect
their food sources.
•Dina Rahmawati", Agussalim Bukhari, Andi Nilawati Usman', Veni Hadju³, Amir Mahmud
Hafsa, and Stang, 2024, The Benefits of Processed Purple Sweet Potato (Ipomoea batatas L.
poir) in Increasing Nutritional Intake
Purple sweet potato is a unique crop. With various health benefits and nutritional values, there
are still a lacks consumption of this crop among consumers, especially Malaysians. Besides high
in dietary fiber, it also has a low glycemic index, contain proteins, minerals, polyphenols, and
anthocyanin. Therefore, it could become an alternative crop for people who have less fiber intake
in dietary pattern. The crop also found as anti-oxidative, hepatoprotective, anti- inflammatory,
anti-tumor, anti-diabetic, anti-microbial, anti- obesity, and anti-ageing effects. Purple sweet
potato is an unpopular crop for Malaysians due to a lack of commercial food products based on
this crop. Normally, only a few types of Malaysian desserts and traditional snacks are produced
from purple sweet potato. Nevertheless, it is still neglected by Malaysian consumers. Without a
doubt, purple sweet potato can be commercialized globally due to its various health benefits and
nutritional values. To ensure the sustainability of Malaysia purple sweet potato, this local crop
needs to be developed and produced in various types of food products such as cracker, bread,
cakes and cookies to prolong its shelf life. Hence, it has good potential commercialization
purposes through the product development process on a big scale.•Rosmaliza Muhammad,MN
Md. Norazmir,Emmy Hainida Khairul Ikram and Shazali Mohd Shariff , August 2021, The
Sustainability of Malaysia Purple Sweet Potato and Its Nutritional Value: Product Development
Perspective
Purple sweet potato (Ipomoea batatas) skin and tuber flesh are dark purple-coloured. The purple
sweet potato contains anthocyanin colour pigments. Total purple sweet potato anthocyanin
content was 519 mg/100 g fresh weight. The purple pigment (anthocyanin) in purple sweet
potato is useful as an antioxidant because it can react with free radicals in the body cells to
reduce the capacity of free radicals that can cause damage in the body. According to the pigment
anthocyanin contained in purple sweet potato has a higher stability compared to other sources
such as anthocyanin in red cabbage, elderberries, blueberries and red corn. The stability of the
pigment anthocyanin is influenced by light, temperature, and pH (G ,Dwiyanti , 2018).
Given the many benefits contained in purple sweet potato, innovation and creation are needed to
process the purple sweet potato that has high antioxidant value. One way to process purple sweet
potato is to produce purple sweet potato juice as functional beverage. One of the step of
processing purple sweet potato into juice includes heating treatment. According to [8] the heating
process can affect the stability of anthocyanin contained in purple sweet potato. Therefore, this
study aims to determine the purple sweet potato processing which can produce purple sweet
potato juice with the best antioxidant activity and levels of anthocyanin.
Total Anthocyanin of Purple Sweet Potato Extract and Juice using Method of pH Difference
Purple colour of purple sweet potato indicated the presence of a natural dye contained in it which
is anthocyanin, a water-soluble pigment and is a secondary metabolite compound of the
flavonoid group that can act as an antioxidant in purple sweet potato.
•G Dwiyanti , W Siswaningsih and A Febrianti , 2018, Production of purple sweet potato
(Ipomoea batatas L.) juice having high anthocyanin content and antioxidant activity

Noodles
Noodles are a type of food made from unleavened dough which is either rolled flat and cut,
stretched, or extruded, into long strips or strings. Noodles are a staple food in many cultures (for
example, Chinese noodles, Filipino noodles, Indonesian noodles, Japanese noodles, Korean
noodles, Vietnamese noodles, and long and medium length Italian pasta) and made into a variety
of shapes. While long, thin strips may be the most common, many varieties of noodles are cut
into waves, helices, tubes, strings, or shells, or folded over, or cut into other shapes. Noodles are
usually cooked in boiling water, sometimes with cooking oil or salt added. They are often pan-
fried or deep-fried. Noodles are often served with an accompanying sauce or in a soup. Noodles
can be refrigerated for short-term storage or dried and stored for future use. •Justice Moe,
June 14 2023, Noodles
Noodles in various contents, formulations, and shapes have been the staple foods for many Asian
countries since ancient time. They can be made from wheat, rice, buckwheat, and starches
derived from potato, sweet potato, and pulses. Noodles based on wheat are prepared mainly from
three basic ingredients; flour, water, and salt. There exist two distinct types of wheat flour
noodles based on the presence and absence of alkaline salts, regular salted noodles, and alkaline
noodles. The basic process of dough mixing, sheet forming, compounding, sheeting/reduction,
and cutting are essentially constant for all machine-made noodles. Noodle strands coming out of
cutting rolls can be further processed to produce different types of noodles. This article analyzed
all the major processes involved from raw material to finished products in relation to noodle
processing properties and cooked noodle texture. Different ingredients and their functionality in
noodle processing were discussed as well. Guidelines were provided to select the right
ingredients to produce high quality noodle products.
Processing properties, appearance, and colour of noodles are the three key criteria used to judge
a process and raw material quality. High quality noodles should be bright in colour with very
slow discoloration, have an adequate shelf life without visible microbiological deterioration or
oxidative rancidity, and have appropriate flavour and textural characteristics which will vary
according to the noodle type and region. Flour plays a key role in all aspects of noodle quality.
Protein content is positively correlated with noodle firmness and sometimes negatively
correlated with elasticity. Therefore, a correct range of protein content is important for textural
characteristics. Adequate gluten strength and extensibility is required in all noodle flours. Noodle
dough must be strong enough to withstand sheeting, but not so strong as to cause tearing or
difficulty in sheet reduction. A good level of dough extensibility ensures that dough sheets do not
shrink back during successive roll passes. The importance of the pasting properties of starch to
the texture of cooked noodles has been well-documented. The required soft, smooth, and elastic
textural properties of certain types of white salted noodles can be best obtained from wheats with
high starch paste viscosity and high swelling starch properties. Alkaline noodles do not have the
same requirement for high starch swelling properties.
Noodles made from flour with high swelling starches have softer texture than those with low
swelling starch. Noodles should be bright and slow in discoloration with time after
manufacturing. For white salted noodles, a white or creamy white colour is desirable. The level
of natural yellow pigment levels (xanthophylls) in flour is highly correlated with noodle colour,
and this is wheat variety dependent. For yellow alkaline noodles, a bright yellow colour is
required, although the preference for the degree of colour development is regionally based.
Noodle darkening increases with the increases of flour extraction rate. This is due to the action of
polyphenol oxidase (PPO) enzymes which are largely located in the bran layer. Low flour
extraction and ash levels are preferred for the manufacture of noodles with a clean and bright
appearance. A relatively fine flour particle size enables even hydration during mixing and
optimum, uniform gluten development during sheeting. Increased starch damage, however, is
associated with poor noodle colour and undesirable high cooking loss and excessive surface
swelling.
•Bin Xiao Fu, November 2008,Asian noodles: History, classification, raw materials, and
processing
Asian noodles were invented more than 4000 years ago in China. They have evolved into many
types and forms and become a global food today. Asian noodles can be made from a variety of
raw materials such as wheat flour, rice flour, buckwheat flour, or starches derived from rice,
wheat, mung bean, tapioca, sweet potato, sago, or corn. Wheat flour noodles can be classified
based on the presence or absence of alkaline salts, type of flour used, noodle strand sizes, and
noodle processing technology. White salted noodles have simple formulations containing flour,
water, and sodium chloride, but they can be made into different marketing forms. Yellow alkaline
noodles contain kansui (a mixture of sodium and potassium carbonates) that modifies noodle
color and texture. Rice noodles are classified into two major groups, qiefen (cutting
pregelatinized starch sheet) and zhafen (extrusion of pregelatinized starch) based on the molding
methods, but the products have different shapes, dimensions, and moisture content. Other starch
noodles have also been widely available in Asia. Today, both wheat flour noodles and gluten-free
noodles have gained popularity worldwide.
•Gary G. Hou ,2020, Asian Noodles Manufacturing
Wheat flour noodles can be supplemented with a range of materials that can boost fiber, protein
etc.
Recently, food manufacturers have responded to consumer demands for foods with higher fiber
content by developing products in which high-fiber ingredients are used dietary fiber can also
impart some functional properties to foods, e.g. increase water holding capacity, oil holding
capacity, emulsification and/or gel formation. Traditionally, consumers have chosen foods such
as whole grains, fruits and vegetables as sources of dietary fiber. Flour of hard wheat
(Triticumaestivum L.) is the main primary ingredient which is usually used to make instant
noodles is low in fiber and protein contents but also poor in essential amino acid, lysine .
Noodles also can be made from other ours like rice, buckwheat, and starches derived from
potato, sweet potato, and pulses. Most of the essential nutrients are lack in traditional noodles
such as dietary fiber, vitamins and minerals, which are lost during wheat flour refinement. us,
noodle products which represent a major end-use of wheat, are suitable for enhancing health
after incorporating sources of fiber and essential nutrients. e essential amino acids are not present
in Instant noodles mainly consist of wheat our whose protein quality is not sufficient.
•Komal Pakhare,Iranna Udachan,January 2016,Studies on Preparation and Quality of Nutritious
Noodles by Incorporation of Defatted Rice Bran and Soy Flour

Sweet Potatoes Noodles

The invention discloses a sweet potato noodle and the producing method. The mixing ratio of the
raw materials: sweet potato refined powder 40-55 weight shares, strong-muscle wheat flour 60-
45 weight shares; that of the assistant materials: the weights of agar is 0.5-3% of said raw
materials, instant bitter fleabane ash is 0.5-1% of said raw materials and salt being 0.3-1% of the
raw materials, respectively. The producing technique: mix the refined powder, the wheat flour
and the assistant materials together, blend evenly, and then use the producing technique of
ordinary noodles to make the sweet potato noodle. The sweet potato's use rate is high, and the
nutrient and medicinal value are high. It can widely be used as noodles, fine dried noodles,
instant noodles, etc, in the daily life.
Noodles made with sweet potato offers several nutritional benefits. The incorporation of sweet
potato flour and mash in specialty noodles enhances its nutritional composition and bioactive
potential [1]. Sweet potato noodles has low in-vitro starch digestibility, which aligns with current
dietary preferences [2]. The addition of sweet potato flour and mash improves the functional
properties of pasta [3]. Sweet potato noodles shows an increase in total phenols, flavonoids, β-
carotene content, and DPPH radical scavenging activity, indicating higher antioxidant properties
[4]. Composite noodles made with orange-fleshed sweet potato and maize flour is gluten-free
and nutritious, with higher antioxidant properties due to Maillard reaction and caramelization
products [5]. Substituting wheat flour with sweet potato flour in noodles increases water holding
capacity, cooked noodles water uptake, freeze-thaw stability, and decreases pasting viscosities
and cooked noodles hardness . Fortifying sweet potato noodles with gum sources reduces starch
digestibility and produces noodles with low starch digestibility, good swelling index, and textual
characteristics, making it suitable for diabetic and obese individuals .
•G Padmaja, November 18 2023,What are the nutritional benefits of noodles made with sweet
potato?
Noodles are widely consumed throughout the world and their global consumption is second only
to bread. As the world market is expanding, studies for the development and improvement of
noodles qualities satisfying consumer demands is of immense importance. Wheat flour is the
main ingredient used to make noodles is not only low in fibre and protein contents but also poor
in essential amino acid, lysine and therefore, characteristics of wheat flour are important for
noodle making.In recent years, the demand to use novel sources as substitute for wheat flour has
increased.
Now-a-days, in order to enrich the varieties of noodles, wheat noodles have been fortified with
various ingredients. So, as a part of replacement the sweet potato is being tried. As, flours from
alternative sources such as sweet potato, and other tubers are being used as potential wheat flour
substitutes for noodle making adding variety and functionality to the product. Tubers and roots
do not contain any gluten, and these are rich source of carbohydrates in the form of starch, which
plays important role in establishing the textural properties of products like noodles.
There is now a renewed effort to broaden the food base in developing countries by creating new
food products based on indigenous raw materials such as sweet potato, etc. Sweet potato
(Ipomoea batatas) is an important starch rich tuber crop which is available throughout the
country. Sweet potato flour is less expensive, nutritious and ordinarily harmless source of
carbohydrates, calories. 100g flesh of sweet potato contains 7 IU vitamin A which are about one
and half times more than daily requirement of Vitamin A for an adult.

Sweet potato is low in protein content, its lysine content (an essential amino acid limiting in
cereals) is higher than that of rice; hence when taken in combination with rice, it improves the
amino acid spectrum and hence the biological value of the diet. To reduce pressure on rice and
change food habits which involves the use of non-rice commodity for production of convenient
food products. Formulation of breads, biscuits, cakes, noodles etc. could be developed using
sweet potato flour mixed with wheat flour. This sweet potato-wheat flour blend could be a
valuable raw material to substitute for rice. Processing of sweet potato flour into value added
product like noodles have potential to increase income and improve livelihood of sweet potato
growers. Apart from value addition, through novel food products development there is also scope
for variety, convenience and cost efficiency. Most snack foods being cereal based are
monotonous in regard to their nutritional quality. •A Mithila , K Sowjanya, Blessy Sagar
Seelam, M Akhila, J Suma Madhuri,2021, Fiber enriched multi-millet noodles-incorporated with
sweet potato flour
Noodles, a staple food was produced from blends of sweet potato flour (Ipomea batatas) with
Wheat flour (Triticum aestivum) at different proportions. These formulated blends were used to
produce noodles and the noodles were subjected to proximate analysis and sensory evaluation.
Results from the proximate analysis revealed that fat, fiber and ash were higher in the formulated
blends than the control while Carbohydrate and BProtein decreased with increase in OFSP.
Moisture content of the control was higher and significantly different from other samples. The
result of the Sensory evaluation based on a nine-point hedonic scale showed that apart from the
control which was the most acceptable, noodles supplemented with OFSP up to 15% .
•Sunmonu Basirat Afolake, Agbaje Rafia, Ogunbule Moyosore Tobiloba, Adebayo Teslim
Kayode, Ogundele Gabriel Femi, December 2018, Quality Assessment of Noodles Produced
from Wheat (Triticum aestivum), Orange Fleshed Sweet Potato (Ipomea batatas) and Sesame
(Sesamum indicum) Blends

Sun Drying
Sun drying is one of the many methods of food dehydration. Dehydrating food before storing it
is one of the most effective ways to preserve it for the long-term. Food drying is a very simple,
ancient skill. It is one of the most accessible and hence the most widespread processing
technology. Sun drying of fruits and vegetables is still practised largely unchanged from ancient
times. Traditional sun drying takes place by storing the product under direct sunlight.
Sun drying is only possible in areas where, in an average year, the weather allows foods to be
dried immediately after harvest. The main advantages of sun drying are low capital and operating
costs and the fact that little expertise is required. The main disadvantages of this method are as
follows: contamination, theft or damage by birds, rats or insects; slow or intermittent drying and
no protection from rain or dew that wets the product, encourages mould growth and may result in
a relatively high final moisture content; low and variable quality of products due to over or
under-drying; large areas of land needed for the shallow layers of food; laborious since the crop
must be turned, moved if it rains; direct exposure to sunlight reduces the quality (colour and
vitamin content) of some fruits and vegetables. Moreover, since sun drying depends on
uncontrolled factors, production of uniform and standard products is not expected.
The quality of sun dried foods can be improved by reducing the size of pieces to achieve faster
drying and by drying on raised platforms, covered with cloth or netting to protect against insects
and animals.
Ref • Parvez Ali Ali , 2006 , SUN AND SOLAR DRYING, TECHNIQUES AND EQUIPMENT
I.
• This is the most fundamental method of drying for preservation purpose
• It is also know as natural drying
• Only uses direct sunlight and wind
• Mostly use by smallholders/farmers, managed by single family mostly
• Some estates/plantations still use this method, uses large land areas
• Suitable for areas that receive high rate of solar insolation and with longer daytime
Reference • April Lee , June 7 2023 , Sun Drying Food-How to Get Started
Oven Drying
Drying ovens are used for a number of reasons in laboratories, businesses, and homes. They can
perform simple tasks such as drying and sterilizing lab equipment like glassware. However,
industrial drying ovens can also be used for more challenging tasks that require controlled
heating, such as bonding. They are also ideal for preserving flowers and dehydrating foods to
increase their in-store shelf life.
A drying oven can estimate several samples' moisture content at the same time
Drying oven
• It can determine the water content of large sample volumes
• It has a simple procedure to perform
Quick measurement
• Portable
• The halogen moisture analyzer does not require any calculation, and its sampling is simple;
therefore,
the possibility of errors decreases.
Halogen moisture analyzer
The heating rate is fast; therefore, the halogen moisture analyzer can quickly reach its maximum
power
• The equipment is fully automated
• Needs a very small space
The oven-dry test, combined with the prong or stress test, is a very useful tool for the kiln
operator to have at his or her disposal. Often the kiln operator is asked to defend the accuracy of
moisture meter measurements or a customer simply does not believe moisture meter readings. In
other situations, the operator may want to verify meter readings for his own piece of mind. For
situations in which moisture meters will give the same information more quickly and with little
effort, then they are the tools of choice. However, it is important to always remember that the
oven-dry moisture content is what the meters are trying to estimate.
•Jim Reeb and Mike Milota, 2007 , MOISTURE CONTENT BY THE OVEN-DRY METHOD
FOR INDUSTRIAL TESTING

Microwave Drying
The microwave generator (magnetron) produced microwaves with varying power densities based
on the supplied power. The generated microwaves were guided using the waveguides into the
microwave cavity. Microwave drying uses electrical energy in the frequency range of 300 MHz
to 300 GHz. The most commonly used frequency is 2,450 MHz. Microwaves are generated
inside an oven. This is done with the help of the magnetron tube. Microwave drying offers to
shorten the drying time without degradation of final quality of the dried product.
The use of microwave energy for drying has been demonstrated to have moderately low energy
consumption. When the material couples with microwave energy, heat is generated within the
product through molecular excitation. The critical next step is to immediately remove the water
vapour. A simple technique for removing water is to pass air over the surface of the material
hence combining processes to form what is called "microwave convective drying".
•Rohini K Parit and Ms. Chatali S. Prabhu, January 2017, Microwave Fruit and Vegetables
Drying
The advantages of using the microwave as a drying tool have advantages including the heating
time for many foodstuffs using the microwave which is about a quarter of the time used in
conventional heating .
The fast- drying time is offset by the high microwave frequency. The high frequencies used in
microwaves allow fast energy transfer and high heating rates thus preserving the nutrient and
vitamin content as well as the taste, sensory characteristics, and colour of food.
Microwave heating is considered to be more energy efficient than conventional heating because
heat is generated in food . Microwave equipment is suitable for on-site cleaning systems, low-
cost system maintenance, and environmentally friendly processing because microwave
generation does not produce exhaust gases or toxic waste . The heating system of microwave can
be turned on or off instantly.
Microwave technology is now equipped with the use of an automatic heating system so that
control of use is easier and prevents overheating.
The use of microwaves also has some downsides. The main disadvantage in the microwave
heating process is the non-uniform temperature distribution. This results in hot and cold spots on
products that are heated by microwaves . The non-uniform temperature distribution in
microwave heating occurs mostly in solid foods and batch method in cavity ovens such as
grains . Some of the other disadvantages of the microwave are high initial costs, limited
penetration of microwaves, and decreased quality of heated food .The most important
disadvantage of this technology is the high investment costs and inefficiencies in the use of
energy and inappropriate methods can result in poor quality results such as discoloration, taste,
and reduced nutrition.
•Nihayatuzain Amanda", Nadilla Shintya Kusuma Wardhani and Anjar Ruspita Sari , 2021 ,
Characteristics of Several Foodstuff Drying by Microwave: A Review
Chemical composition of Sweet Potatoes
Dry Matter Sweet potatoes usually contain about 25% dry matter. The exact amount depends
upon genetic selection, water balance at harvest, condition and time of storage, and perhaps
undefined internal physiological factors. Analysis of 99 genetic selections in a root main- tenance
planting showed a range of dry matter from 17.9 to 49.3%. In another year, 16 cultivars suitable
for North Carolina growing conditions and quality demands were found to contain 23.7 to 28.6%
dry matter." Reports on the dry matter content of 13 high yielding clones in West New Guinea
listed dry matter from 22.8 to 30.79%. Dry matter in 6 selections of Ugandan sweet potatoes
ranged from 30.3 to 39.2%.3“ It has been demonstrated that soil moisture levels during the
growing season significantly influence root dry matter content. Available soil moisture levels
above 25% caused decreases in dry matter. The same study showed that nitrogen fertilization
rates from 0 to 90 lb per acre had no effect on dry matter content. Regardless of treatment, dry
matter was found to be the most variable quality attribute tested with variations of up to 5% from
1 year to another.
Climatic factors other than water availability may affect dry matter content but it is difficult to
separate such factors from age of the roots at the time of harvest. Roots which were harvested
102 days after planting had 27.3% dry matter while those harvested at 165 days had 25.7%.35
Dates of harvest were September 6 and November 8, thus the variable of harvest date was
superimposed on time after planting. Data from an experiment with staggered dates of planting
and multiple harvest permitted calculation of dry matter as a function of harvest date, and time
between planting and harvest. The data showed that the dry matter content increased from 26.7%
in August to 29.8% in November. These same data also show that dry matter content increased
from 29.0% 3 months after planting to 31.3% 6 months after planting. Apparently dry matter
increases with age of roots.
After harvest, sweet potato roots continue to respire, converting carbohydrates into carbon
dioxide and water. They also "sweat", i.e., give off water, thus changes of dry matter may be
expected during proper storage, however the ratio between dry matter and water remains nearly
constant during storage. Appleman concluded that sweet potatoes in storage may lose at least
38% of their original weight without any signifcant change in percent dry matter. 40 Others have
reached essentially the same conclusion.41.42 It is probable that roots harvested under water
stress would show changes toward equilibrium water content, i.e., high moisture roots would
lose water while low moisture roots would retain water.
2. Carbohydrates
Most of the dry matter of sweet potato is carbohydrate, 85 to 90%. Factors affecting the total
carbohydrate fraction are essentially the same as those that influence dry matter content. The
carbohydrate fraction consists of starch, sugars, pectins, cellulose, and probably hem-icellulose
and pentosans. Sweet potato starch, which contains 79 to 83% amylopectin, is the major
carbohydrate, and accounts for 65 to 80% of the total dry matter. 42-44 Although maltose has
been reported in raw Centennial sweet potatoes," others have demonstrated that maltose is not
present in raw tissue but is formed when roots are ground with hot solvent. McDonald and
Newson reported 0.33% glucose, 0.15% fructose, 3.47% sucrose, and 0.01% inositol in raw
Centennial roots. Sucrose is thus the most abundant sugar in the raw sweet potato, ranging from
2.5 to 5.2% in freshly harvested roots and increasing to 10% after storage. 45-47 Stone has also
reported that glucose and fructose are minor constituents of raw roots. After roots are harvested,
glucose levels continually increase during storage while sucrose levels increase only for the first
17 days after harvest. Sweet potato roots continue to respire after harvest.
Glucose is the most likely substrate for respiration. It can be postulated that starch is slowly
degraded to dextrins which are rapidly degraded to glucose, thus large amounts of dextrins do
not accumulate. Glucose is made on demand and furnishes energy for cellular metabolism, thus it
also does not accumulate in large amounts. It is probable that the amyloid carbohydrates are the
major source of biological caloric value of sweet potatoes, which is reported to be 4.11 Kcal/g
dry weight. Significant changes in amyloid carbohydrates occur during cooking or processing.
Duringheating up to 95% of the starch may be degraged to dextrins and maltose, 32.50-53 These
changes are attributed to the action of alpha and beta amylases which are naturally present in the
roots. These enzymes probably are involved in mobilizing carbohydrates for respiration during
storage but they evidently do not become fully active until starch is gelatin- ized. Both enzymes
seem to have appreciable tolerance to high temperature and remain active for several minutes at
temperatures which disrupt the starch granules. The amount of enzyme and consequently the
magnitude of carbohydrate conversion during cooking, varies according to cultivar and post
harvest treatment as well as conditions of cooking. 19 There appears to be no direct changes in
nutritional value due to carbohydrate conversion. Extensive carbohydrate conversion results in a
sweeter, more "moist" product.
Much less has been reported about the nonamyloid carbohydrates than the amyloids. Pectins are
the largest fraction of nonamyloid carbohydrates. The pectins are important in maintaining
wholeness and firmness of canned sweet potatoes. They have also been inves- tigated in an effort
to explain the different rheological properties of cooked roots of different cultivars and changes
of "moistness" caused by curing and storage.
The mean total pectic content of eight cultivars was 5.1% fresh weight, estimated to be about
20% dry weight at harvest. This value declined to 3.5% fresh weight after 6 months of storage.
Most of the decrease was due to changes in the hydrochloric acid soluble fraction, while the
ammonium oxalate soluable and water soluable fractions did not change significantly.
The degree of esterification decreased during storage. Baking and processing decreased the
amount of pectins and the degree of esterification. However, no direct relationship was found
which correlated rheological and sensory changes of baked sweet potatoes with changes in pectin
content or molecular size of the pectins. The fiber content of sweet potatoes has been reported to
range from 2.5 to 5% dry ba- sis. 57-59 The only report available lists cellulose content of sweet
potato at 2.69% dry basis. We believe the fiber fraction consists of the cellulose and possibly
hemicellulose and pentosans. Stringiness or fiberousness is a quality defect which occurs in some
sweet potatoes. 59 It appears that this defect is genetic and unrelated to dieting fiber. Of those
varieties most subject ot stringiness only about half of the roots manifest this defect. Sweet
potatoes are generally regarded as causing flatulence. Severity and frequency of the problem has
not been adequately documented but it appears that people who commonly eat sweet potatoes
recognize it. Flatulence has been attributed to oligosaccharides partic- ularly raffinose and
stachyose. Some workers feel that flatulence may be caused by un- digested starch reaching the
lower intestine. Unpublished research from our laboratory has indicated that two cultivars of
sweet potato, Jewel and Centennial, contain no stachyose.

3. Proteins
Folklore and misinformation have decreed that sweet potatoes are a starchy food without
significant amounts of protein. A number of animal feeding studies have indicated that sweet
potatoes are nearly equal to corn on the dry weight basis. 64-68 The value of sweet potato has
also been recognized for human nutrition.Worldwide reports indicate that protein levels of sweet
potato range from 1.73 to 11.8% protein dry basis, 34.58.66.71.72 Cultivar or genetic selection is
a major factor influencing the amount of protein in the roots, The time between planting and
harvest has a minor influence on protein content.
Nitrogen and water balance influence protein content, 36.73 but the relationship is not fully
defined. 36 There are large unexplained differences in protein content due to location at which
the sweet potatoes are grown." Jewel sweet potatoes were found to produce 4.13% protein in one
location in North Carolina while the same cultivar produce 8.81% protein in a different location
in North Carolina in the same year. Centennial and Jewel sweet potatoes grown in North
Carolina had twice as much protein as the same cultivars from the same root mintenance
collection grown in Los Banos, Laguna, Philippines. 75 Differences of protein within a cultivar
may be a complex function of soil water and soil nitrogen levels. The amount of nitrogen applied
as fertilizer may account for about half of the observeddifference in protein content. 36.7%
Sulfer and potassium fertilization apparently have no effect on protein content although
potassium increases the yield in North Carolina soils.
Some protein is lost during storage but the rate of loss is less than the rate at which carbohydrates
are lost, thus the relative concentration of protein increases during storage." The limit to the
degree of concentration in storage is not known. In our laboratory we have measured stored roots
with 16% protein, which we estimate contained about 6% protein at harvest. However, these
roots were pithy, and microsopic examination showed a greatly decreased number of starch
grains all of which were very small. Appreciable amounts of nitrogen are found in the nonprotein
nitrogen (NPN) fraction. The NPN fraction is defined as nitrogen not precipitated by 12%
trichloroacetic acid and thus is of low molecular weight. Studies in our laboratory have shown 30
to 40% of the nitrogen in Jewel is in NPN." It is believed that most of the nitrogen is in
asparagine. Nearly all of the remainder of the nitrogen can be accounted for by other amino
acids. One must exercise caution in assigning protein nutritional value using Kjeldahl nitrogen
values alone. Although NPN is available for amino acid synthesis, it contributes very little to the
amounts of essential amino acids of sweet potato.
The protein of sweet potato is quite evenly distributed throughout the root. There is a small but
statistically significant concentration at the stem end." There is no statistically significant
circumferential or radial distribution. It would not be possible to prepare high protein products
by selectively cutting sweet potatoes. There is also no justification to the belief that peeling
removes the most nutritious part of the root. Sweet potato protein is of good quality and
compares favorably with the FAO reference.
4. Lipids and Fatty Acids
Lipids are a minor class of components in sweet potatoes, ranging from 29 to 2.7% dry basis.
34.43.81 Boggess studied changes in lipid composition during storage, 62.83 Short chain, C10-
C12, fatty acids decreased during storage. Changes were more rapid at low temperatures. The
amounts of other fatty acids increased in storage, suggesting fatty acid synthesis. Boggess
compared the lipids of nine varieties of sweet potatoes and found a range of total lipids from 1.24
to 2.50% dry basis.
The total lipids varied more than individual components. The means of lipid fractions were:
Nonphospholipids. 85.1%
Cephalin Lecithin. 9.6% 5.3%
Linoleic acid was the major fatty acid in all varieties, 47.8% of the total lipids and palmitic was
the next most abundant at 34.6%, followed by linolenic 7.1%, steric 6.1% and oleic 1.3%. Other
fatty acids were individually less than 1% of the total. Walter et al. studied the lipids of
Centennial by different methods. They found 42.1% neutral fats, 30.8% glycolipids, and 27.1%
phospholipids. Relative abundance of the major fatty acids was similar to the findings of
Boggess. Among the neutral lipids they found 2.8% hydrocarbons and 2.5% sterols. The major
sugar in the glycolipids was galactose. Small amounts of glucose were also found. Ethanolamine,
choline, and inositol were major components of the phospholipids. Carotenes account for about
2.3% of the lipids in Jewel and Centennial and would be found among the hydrocarbons.
Carotenes are, therefore, the major component of the hy- drocarbon fraction.
5. Carotenoids
Carotenoids in sweet potatoes are important both for color and nutrition. A recent consumer
survey indicated that U.S. consumers prefer the most orange internal color available. 22 This
does not seem to be related to a desire for vitamin A value because most consumers do not relate
color to nutritional value. The desire for deep orange color does not apply to everyone in the
U.S., nor does it apply in other nations. It seems to be common knowledge (not documented) that
Cuban and Puerto Rican immigrants prefer a white or pale yellow internal color for sweet
potatoes. Some older people in the U.S. fondly remember the Jersey which was pale yellow or
the Porto Rico of past years which was yellow to pale orange sweet potatoes. Miller and
Covington reported carotene contents of 15 mg% (mg/100g) wet basis, estimated to be about 60
mg% dry basis. 85 More recently some cultivars have been found to contain 72 mg% dry basis.
129 Beta-carotene is the major pignent of the orange flesh sweet potato which have been studied,
#5-#9 Two cultivars have been studed in detail and beta-carotene is the only significant source of
vitamin A value.
The carotenoid fraction of Goldrush contained 89.9% beta-carotene and 0.7% gamma-carotene.
The vitamin A isomers of Centennial included beta-carotene 86.4%, alpha-carotene 0.9%, and
gamma- carotene 0.8%.
In our laboratory we studied the carotenoids of an experimental selection, Julian 288-1 which
showed a noticeable range of flesh color from a single planting. Total carotenoids ranged from
5.6 to 32.0 mg% dry basis. The amount of epoxides and hydroxy carotenoids remained nearly
constant but the beta-carotene varied from nearly 0 to about 25 mg%. The non-beta-carotene
fraction appeared similar to that of Centennial, although some of the minor pigments found in
Centennial were not found. We were unable to find alpha and zeta- carotenes. This experience
serves as a warning that pale yellow flesh color may not nec- essarily indicate a significant
amount of vitamin A value.
Genetic selection of cultivars is the most important factor in determining the amount of
carotenoids in sweet potatoes, but other factors may significantly alter the amount. Exam- ination
of canned samples by the National Sweet Potato Collaborators Group has frequently shown that
some selections are orange at one reporting station and a pale yellow at others. It has been noted
that roots of a single cultivar at one station in Mississippi sometimes would have twice as much
carotene as from another station. No explanation for this variance was offered. However, flesh
color in the Centennial cultivar has been shown to be adversely affected by available soil
moisture levels above 25% and by nitrogen fertilization rates above 90 lb/acre.
Carotenoids change during storage. In some cultivars it appears that carotenoids increase storage
while in others the carotene decreases.
Processing, including baking or boiling, of sweet potatoes may cause minor changes in
carotenoid content (vitamin A value) due to heat mediated isomerization." Provitamin A has been
shown in many processing studies to be remarkably heat stable and to be only slightly affected
by cooking or processing. Consequently, losses of vitamin A value from sweet potatoes during
processing are minimal. Occasionally processing appears to increase the amount of carotenoids.
Most of the increase can be rationalized as loss of water content of leaching of water soluble dry
matter.
Carotenoids are readily susceptible to autoxidation, especially in a medium of low water activity.
93-95 It appears that conditions used for manufacture of precooked dehydrated sweet potato
flakes encapsulates most of the carotene in carbohydrates to prevent autoxidation, thus
carotenoids in this product are more stable than in dried products made by other means. 95 The
level of carotenoids in most orange fleshed sweet potatoes grown in the U.S. is sufficiently high
to provide a weeks supply of vitamin A with one generous serving. Vitamin A is one of the most
widespread vitamin deficiencies in the U.S. Thus, increased con- sumption of sweet potatoes
could serve to correct this situation. During World War II, most of the war-ravaged world
suffered widespread vitamin A deficiency. However, in Japan sweet potatoes were grown for
chemurgy and livestock feed. People were forced by cir- cumstances to eat sweet potatoes and as
a consequence, vitamin A deficiency was rare although the Japanese sweet potatoes did not have
as high a carotene content as those presently grown in the U.S. The high level of carotene in U.S.
sweet potatoes may cause hypercarotenosis if eaten daily with adequate fat to assure absorption.
Hypercarotenosis is not similar to hypervitaminosis A and is not considered particularly
detrimental although it does impart a yellow color to the skin of the patient. The mere
consumption of large amounts of sweet potatoes having an adequate level of beta-carotene does
not assure protection from vitamin A deficiency unless additional fats are included in the diet to
assure adsorption of the carotene."

6. Vitamins
Sweet potato apparently contains all of the vitamins needed to assure metabolism of its
carbohydrates. Before the various components of the B-complex were recognized it was reported
that sweet potato contained 0.7 IU B-vitamin per gram, i.e., 2.8 IU per gram of dry matter of per
4.11 K. Since then all of the B-complex except B₁₂ have been reported in sweet potatoes as
follows:
Vitamin. µg/g dr. Ref.
Thiamine. 5.6. 99
3.6. 100
Riboflavin. 1.2. 101
1.8. 99, 100
2.0. 100
Niacin. 45.3. 102
19.8. 101
22.4. 90
24.0. 100
Pantothenic. 28.0. 103
acid. 23.0. 101
44.0. 99
38.0. 100
Folic acid. 0.6. 104
0.2-0.8. 100
Pyridoxin. 12.8. 100
Biotin. 1.7. 100
Para amino. 100
Benzoic acid. 24-48
Choline. 14.0. 100
None of the vitamins decrease appreciably during processing. About 11% of the riboflavin and
28% of the pantothenic acid are lost during dehydration. Baking destroys 25% of the thiamine,
12% of the riboflavin, 15% of the niacin, and 23% of the panthothenic acid.
Boiling causes loss of 7 to 8% of the thiamine but other vitamins are essentially unaffected."
There are no data concerning stability of folic acid, pyridoxine, biotin, para aminobenzoic acid,
or choline. There are not sufficient data to determine differences in cultivatars or effects of
climatic and environmental conditions. Sweet potatoes are a good source of vitamin C (ascorbic
acid). As early as 1924, Pech reported that 10 g of sweet potat per day prevented scurvy in
Guinea pig.
Sweet potatoes contain 23.5 and 33.3 mg% fresh weight of vitamin C in Triumph and Nancy
Hall cultivars. 106 These values decreased 28 and 40% during 7 months of storage. During
cooking 69 to 83% of the vitamin C was retained. Others have confirmed the loss of vitamin C in
storage with values decreasing from 46 to 28 mg% in 4 months. 107 Crosby lists the value of
vitamin C at 22 mg%. 100 In conjunction with other work we have measured the vitamin C in
uncured Jewel roots after seven days in market channels, in roots cured for 4 days, then 7 days in
market channels and roots cured 7 days and 7 days in the market channels. Uncured roots
contained 25.0 mg%. It is obvious that vitamin C content does decline during storage. It is
probable that the vitamin C content will not drop below 15 mg% as long as the roots remain
healthy.
Variations in vitamin C content as related to cultivar and growing conditions have not been
reported. Losses during processing have been reported. Roots estimated to have con-tained
24.5% before canning contained 7 mg% after canning and 4 to 5 months of storage. However, a
significant part of the difference may have been due to leaching of the vitamin C into the syrup.
Dehydrated flakes contained 40 to 88 mg% with a mean of 65.6% for 17 samples. 108
Correcting for differences in dry matter it is estimated that the flakes would have contained about
17 mg% when reconstituted to the same dry matter as the canned sweet potatoes.
Baking or boiling causes decreases in ascorbic acid content depending upon whether the roots
are cooked immediately after harvest, approximately 20% loss, or after storage for 6 months,
approximately 40% loss. 109 Some novice nutritionists have expressed concern that many
processors use lye peeling to prepare sweet potatoes for canning They believe this practice
destroys the vitamin C. The lye-softened tissue probably has no vitamin C at all but there is no
evidence to suggest that the alkali has any effect upon vitamin C in tissues which have not been
penetrated and softened. The lowest levels of vitamin C are present in the outer 4 mm of tissue.
110 It is this layer which is removed by lye peeling, thus lye peeling does not destroy the tissues
having the highest concentration of Vitamin C. Except for beta-carotene, the fat soluble vitamins
have received little attention. One report cites the vitamin E level at 16 mg% dry basis. One
report gives the vitamin K value at 20 mg%.
7. Minerals
There are not sufficient data available to adequately describe ranges of mineral contents due to
cultivar or environment. Agricultural Handbook No. 456 provides some data on mineral values
as follows:
Element. Raw
Potassium. 59.49
Calcium. 78.6
Phosphorus. 115.4
Iron. 1.72
mg/100 g dry matter
•A. E. Purcell, W. M. Walter, Jr., and L. G. Wilson, 1989, Quality and Preservation of Vegetables

Physico-Chemical Properties of Sweet Potatoes Flour

Determination of Protein Content
The protein content was determined in all samples by micro Kjeldahl method using copper
sulphate sodium sulphate catalyst according to the official method of the AOAC (2003). 2 g of
sample was accurately weighed and transferred together with 4 g of Na₂SO of Kjeldahl catalysts
and 25 mL. of concentrated sulphuric acid into a Kjeldahl digestion flask. After that, the flask
was placed in a Kjeldahl digestion unit for about 2 hr until a colorless digest was obtained and
the flask was cooled to room temperature. The distillation of ammonia was carried out. Finally,
the distillate was titrated with standard solution of E 0.1N HCI in the presence of 2-3 drops of
bromocresol green methyl red as an indicator until a brown reddish color was observed. A blank
determination was carried out in similar manner using the same reagents without sample. The
result is shown in Table ( ).
Protein (%w/w) = (T-B)xN x 1.4007x6.3
W
Where,
N = exact normality of 0.1 N standard HCl solution
T = titrant volume for sample (mL)
B = titrant volume for blank (mL)
Determination of Ash Content
5 g of sample was weighed in a previously well-dried porcelain crucible The sample was then
placed inside the muffle furnace. Incineration was done at 575 + 250 °C for about (3) hr until ash
was obtained. After that, the crucible was placed in a desiccator and weighed. The total ash
percent of the sample was calculated as follows. (AOAC 2000). The result is shown in Table ( ).
Ash (%w/w) = W1 / W2 x 100
Where,
W1 = weight of ash, (g)
W2= weight of sample, (g)
Determination of Moisture Content
3 g of sample was placed into a dish which had previously been dried, placed in a desiccator and
accurately weighed. Then the dish with the sample was placed in an oven at 105°C and dried for
3 hr. Then they were removed from the oven, cooled in the desiccator and weighed. Heating,
cooling and weighing were repeated until constant weight was obtained. The moisture content
can be calculated as follow (AOAC 2000). The result is shown in Table ( ).
Moisture content (%) = W1-W2/ W2 x 100
Where,
W1 = weight of sample before drying, (g)
W2= weight of sample after drying, (g)
Determination of Fiber Content
The defatted samples were treated with 1.25% (w/v) of sulphuric acid and sodium hydroxide
solution. The digested matter was then filtered, washed with hot water and then ignited. Crude
fiber content was determined by calculation the loss in weight after ignition (AOAC 2000). The
result is shown in Table ( ).
Where,
W1 = initial weight, (g)
W2 = weight of sample after ignition, (g)
Determination of Carbohydrate
The carbohydrate content of sample was calculated as follows (AOAC 2000). The result is
shown in Table ( ).
Carbohydrate = 100-(Moisture+Ash+Protein+Fiber+Fat)
Determination of Total Solubility Content
2.5 g of the sweet potatoes flour was dissolved in 250 ml. of boiling water Then, the mixture was
stand for 5 min and it was poured through a dried, cleaned and weighed filter paper. After that,
the filter paper containing residue was washed with hot water. The residue was dried and cooled
down to room temperature and the insoluble matter was weighed. Drying, cooling and weighing
of insoluble matter were repeated until a constant weight was obtained. The total solubility
content of sweet potatoes flour was calculated according to the following equation. The results
are shown in Table ( ).
Percent solubility =
Weight of sweet potatoes flour-Weight of insoluble matter / Solution volume × 100 Solution
volume
Determination of pH
The pH value of sweet potatoes flour solution was determined by pH meter at room temperature
and the result are shown in Table ( ).
Determination of Water Absorption Index
A sample of dry flour 2.5 g was added to 30 mL of water at 30°C in a 50mL centrifuge tube, and
then centrifuged for 10 min. The supernatant was carefully poured into a tarred evaporating basin
for water solubility index determination. The remaining water absorbed flour was weighed and
the WAI was calculated as the weight of dry solid divided by the amount of dry sample.
Water absorption Index = weight of absorbed flour - weight of dry sample / weight of dry
sample
The results are shown in Table ( ).
Determination of Water Solubility Index
The supernatant liquid from the WAI study was dried at 70°C until constant weight was reached.
The amount of solid in the dried supernatant as a percentage of the total dry solids in original 2.5
g sample gave an indication of the WSI.
Water Solubility Index = weight of solids in supernatant / weight of dry sample x 100
The results are shown in Table ( ).
Determination of Starch Content
Moisture Content
Moisture content There are various methods to determine the moisture content such as drying
methods, distillation method and Kahr-Fischer titration method. The determination depends on
the following criteria:
a) the form in which water is present
b) nature of product analysed
c) rapidity of determination
d) accuracy desired e) availability and cost of equipment required.
In the drying method the amount of moisture in foods is the difference between the weight before
and after drying. It is simple and is used (as a standard method) for many kinds of foods. The
process of drying is caused by the difference of the relative humidity between a food and the
atmosphere, so that the higher the temperature, the faster the drying. Some fermented products
are unstable and decompose at high temperature. Such fermented products are dried at 40-70°
under vacuum. On the other hand cereals are stable at high temperature and are dried at 135°C
under normal atmosphere. Fish and fish products are normally dried at 100-110°C. Simple and
rapid drying methods by oven, infra-red balance and microwave moisture checker are used for
the drying of fish products.
•MC Ng Mui Chng, 1992, Determination of Moisture Content
Sugar Contet
Total soluble sugar content and composition was studied by high performance liquid
chromatography in four high dry-matter sweet potato cultivars at 3, 4, and 5 months maturity.
Total soluble sugar consisted of sucrose, glucose, and fructose, ranging from 4.10-10.82 g/100 g
(dry-weight basis). At harvest, there were significant differences in total soluble sugar due to
maturity (p < 0.001) and cultivar (p < 0.05). The highest total soluble sugar contents were in 5-
month samples at harvest (7.36-10.34 g/100 g) and 4-month samples after short-term storage
under tropical ambient conditions (8.66-10.82 g/100 g). Estimated amylase enzyme activity
varied significantly with harvest age (p < 0.05). Although reducing sugar contents were low,
fructose levels in 5-month samples increased considerably after storage.
The objective of this study was to assess free sugar contents in the roots of staple- type high dry-
matter sweet potato cultivars at different levels of maturity right after harvest and after 3 weeks
storage under ambient conditions. If sugar contents and composition of sweet potato cultivars
(and how these change during storage) are significantly affected by harvest age, then timing the
harvest appropriately would be a simple and effective means of controlling the eating quality and
processing characteristics of such cultivars. This could possibly be applied in targeting desired
sugar levels for specific end-uses, for instance, low sugar for staple food uses and high sugar for
industrial production of sweeteners from sweet potato.
•Evelyn Adu-Kwarteng, Esther Sakyi-Dawson,George S.Ayernor , V.D.Truong, October 2013,
Variability of Sugars in Staple-Type Sweet Potato ( Ipomoea batatas ) Cultivars: The Effects of
Harvest Time and Storage
Bulk Density
The method of Konak et al. was followed to determine the bulk density of the flour.
Approximately 50 g of sweet potatoes flour was weighed into a 100 ml graduated measuring
cylinder and the cylinder was gently tapped continuously until the contents were tightly packed.
The bulk density was calculated as weight of sweet potatoes flour (g) divided by NSP flour
volume (cm3).
•Khuthadzo Ngoma, Mpho E. Mashau, and Henry Silungwe , November 2019 ,
Physicochemical and Functional Properties of Chemically Pretreated Ndou Sweet Potato Flour
Color Analysis
The colour of sweet potatoes flour samples was measured using a Hunterlab LabScan XE
Spectrophotometer CIELAB. The black and white plates were used to calibrate the
spectrophotometer and zero calibration followed. The sweet potatoes flour was put in a glass cell
and placed above the light source of the instrument and colour coordinate values L*
(Lightness/darkness), a* (redness/green) and b*(yellowness/blue) were recorded .
•Khuthadzo Ngoma, Mpho E. Mashau, and Henry Silungwe , November 2019 ,
Physicochemical and Functional Properties of Chemically Pretreated Ndou Sweet Potato Flour