CHAPTER II
REVIEW OF RELATED LITERATURE
Vinegar is a liquid processed from the fermentation of ethanol in a process
that yields its key ingredient, acetic acid, which may also come in diluted form.
Natural vinegars also contain small amounts of tartaric acid, citric acid and other
acids. Vinegar has a density of approximately 0.96 g per ml. Density level depends
on the acidity of the vinegar. Vinegar eels ( Turbatrix aceti ), a form of nematode,
may occur in some forms of vinegar. These feed on the microbial culture that is
used to create vinegar, ( called mother of vinegar ) and can occur in naturally
fermenting vinegar. Most manufacturers filter and pasteurize their product before
bottling to eleminate any potential adulteration (n.a., 2008).
Vinegar is an aqueous solution of acetic acid and trace chemicals that may
include flavorings. Vinegar typically contains 5–20% by volume acetic acid. Usually
the acetic acid is produced by the fermentation of ethanol or sugars by acetic acid
bacteria. Vinegar is now mainly used as a cooking ingredient, or in pickling. There
are many types of vinegar, depending upon the source materials.
As the most easily manufactured mild acid, it has historically had a wide variety of
industrial and domestic uses. Some of these are commonly practiced in the 21st
century, such as its use as a household cleaner (Nakayama T., 1959).
Apple (Malus domestica) is one of the most important temperate fruit crops
of the world and is used besides other in vinegar production. It is a sweet, edible
fruit produced by an apple tree (Malus pumila). Apple trees are cultivated
worldwide and are the most widely grown species in the genus Malus. The tree
originated in Central Asia, where its wild ancestor, Malus sieversii, is still found
today. Apples have been grown for thousands of years in Asia and Europe and were
brought to North America by European colonists. Apples have religious and
mythological significance in many cultures, including Norse, Greek and European
Christian traditions.
Apple trees are large if grown from seed. Generally, apple cultivars are
propagated by grafting onto rootstocks, which control the size of the resulting tree.
There are more than 7,500 known cultivars of apples, resulting in a range of
desired characteristics. Different cultivars are bred for various tastes and use,
including cooking, eating raw and cider production. Trees and fruit are prone to a
number of fungal, bacterial and pest problems, which can be controlled by a
number of organic and non-organic means. In 2010, the fruit's genome was
sequenced as part of research on disease control and selective breeding in apple
production (Dickson, 2014).
Commercially, apples can be stored for some months in controlled
atmosphere chambers to delay ethylene-induced ripening. Apples are commonly
stored in chambers with higher concentrations of carbon dioxide and high air
filtration. This prevents ethylene concentrations from rising to higher amounts and
preventing ripening from occurring too quickly.
For home storage, most cultivars of apple can be held for approximately two
weeks when kept at the coolest part of the refrigerator (i.e. below 5 °C). Some can
be stored up to a year without significant degradation. Some varieties of apples
(e.g. 'Granny Smith' and 'Fuji') have more than three times the storage life of
others (CSIRO, 2015).
Apples are the primary raw material used in cider making. Suitable apples
vary in size with diameters from about eight inches wide to less than two inches.
Nearly all of the characteristics of the final cider product depend on the quality of
the apples from which it is made. To produce the best cider, these apples must be
juicy, sweet, well ripened and have adequate levels of natural acids and tannins.
The skin of the apples contains many of the compounds that contribute to the taste
of the cider so apples are not peeled before being used for cider manufacturing. The
seeds are not removed either however, in typical milling machines, they are not
broken open, and do not significantly contribute to taste. It should be noted that
pears and sweet cherries are also occasionally used to make cider.
A full-bodied cider requires the use of several different types of apples to
give it a balanced flavor. This is because certain varieties of apples have flavor
characteristics that work well together. There are four different
Once the apples are harvested and washed, the fruit is crushed and pressed.
The remaining juice is fermented, creating cider.
Types of apple juices including aromatic, astringent, acid-tart, and neutral
tasting. Generally, sweet and tart apples are blended together to create a balanced
cider. A typical blend might include 50% neutral base, 20% tart, 20% aromatic,
and 10% astringent. In this cider, the flavor is a balance between tartness and
sweetness. Beyond apple blending, some cider producers may also improve flavor
by adding tannic, malic, and other natural acids. Tannins add a slight bitter taste
and astringency to cider. Malic, citric, and tartaric acid give a zesty tingle. They also
help to inhibit microbial contamination.
Producing a gallon of cider requires 11-14 lb (5-6.4 kg)of apples depending
on the juiciness of the fruit. Fresh cider will remain in its full-bodied state for
several weeks if it is refrigerated. After this time natural fermentation process
begins. If a non-alcoholic cider is desired, the juice may be pasteurized or
preserved by the addition of potassium sorbate. This material effectively kills
undesirable organisms. For some cider manufacturers, the alcoholic cider is
preferred. Alcoholic cider is made by either letting the inherent fermentation
process continue without the addition of any other ingredients, or by adding a
variety of ingredients, which give more controllable results.
Fermentation of apple cider is the process by which yeast converts the apple
sugars into ethyl alcohol and carbon dioxide. It occurs in two steps. First, yeast
converts the sugar to alcohol and then lactic acid bacteria convert the natural malic
acid into carbon dioxide. This hard cider contains 2-3% solids and 2-8% alcohol.
Fermentation aids include components such as sulfur dioxide, yeast, sugar, and
natural acids. Sulfur dioxide is typically added to the freshly pressed juice before
fermentation is allowed to begin. It has the effect of killing most of the bacteria and
yeasts present in the freshly squeezed juice, or must. Enough of the desirable yeast
survives the sulfur dioxide treatment and these organisms will go on to ferment the
sweet juice.
Natural yeasts are present in apples, but sometimes cider manufacturers add
their own yeast to ensure that a consistent fermentation will be achieved. Some of
these strains have been around for generations and they are repeatedly used to
produce a distinctive tasting cider. To help yeasts grow and speed up fermentation,
yeast nutrients such as ammonium sulfate and thiamine may also be added. For
similar reasons extra sugar, honey or other sweeteners may also be added to the
unfermented juice. This will improve fermentation and increase the alcohol content
of the final product (Advameg, Inc.,2019).
Dr Sarna says that the colour of apple cider vinegar can vary from lemon
yellow to brownish orange. The colour of the vinegar differs depending on the
colour of the apple peels it is made from. If the apple was pale pink in colour, the
vinegar will have a yellowish colour, whereas if the vinegar is made from dark red
apple, it will be darker. A few brands also sell bleached apple cider vinegar, which is
colourless or white in colour (Chavan, 2016).
Apple cider vinegar, or cider vinegar, is a vinegar made from fermented
apple juice, and used in salad dressings, marinades, vinaigrettes, food
preservatives, and chutneys. It is made by crushing apples, then squeezing out the
juice. Bacteria and yeast are added to the liquid to start the alcoholic fermentation
process, which converts the sugars to alcohol. In a second fermentation step, the
alcohol is converted into vinegar by acetic acid-forming bacteria (Acetobacter
species). Acetic acid and malic acid combine to give vinegar its sour taste (Ulbricht,
2010).
CONCEPTUAL FRAMEWORK
INPUT PROCESS OUTPUT
1.) The number of 1.) Gathering Data 1.) Concluding the
Apple (Malus experimentation
Domestica) that * Assessing the through the
will be utilized for number of Apple statistical
experimentation. (Malus Domestica) treatment
to be used in the
said
experimentation of
2.) The 2.) The odor,
the research.
measurement of color, and taste of
the amount of * Research the vinegar
water and sugar substrate
utilized in the * Quantify the
experiment. total amount of
time to ferment
the vinegar
substrate
3.) Materials that
are to be used in
the
experimentation 2.) Statistical
process. treatment
*Percentage
distribution
