COURSE: CEREAL SCIENCE AND TECHNOLOGY

TITLE OF THE EXPERIMENT: DETECTION OF SORGHUM CONDENSED

TANNINS BY CLOROX BLEACH METHOD AND WET MILLING OF
CEREAL GRAINS (MAIZE)

NAME: LONE O MOGOMOTSI

STUDENT ID NO: 202000627

OBJECTIVES
- To identify condensed tannin containing sorghum cultivars by Clorox bleach method
INTRODUCTION
The determination of pigment in durum wheat and detection of sorghum containing condensed
tannins are crucial tasks in food analysis. Accurate analysis of pigments in durum wheat and the
detection of condensed tannins in sorghum can provide valuable information about the quality
and nutritional composition of these crops.
Pigments play a significant role in determining crop color and visual appeal and their nutritional
value. Understanding the pigment composition of durum wheat can help in assessing its potential
for use in various food products, such as pasta. In addition, the presence of condensed tannins in
sorghum is of interest due to their potential health benefits and impact on food processing.
Phenolic compounds, particularly tannins, can influence the pigmentation of the pericarp and
testa in sorghum grain (Sedghi et al., 2012). All mature sorghum seeds have a testa,however
certain cultivars lack a brown-pigmented inner integument layer. According to Kobue-Lekalake
et al. (2007) all sorghum cultivars were perceived as bitter and astringent. The pigmented
integument layer contains a high level of condensed tannins. Previous studies have highlighted
the high antioxidant activity of condensed tannins in sorghum, which are not common in other
major cereals such as wheat and rice (Shen et al., 2020). Dykes et al. attributed the higher
antioxidant activity of sorghum hybrids with a pigmented testa compared to other sorghum types
to the presence of condensed tannins.
On the clorox bleach method,those kernels with condensed tannins apper darkbrown or dark
black while sorghum kernels of without brown pigmented inner integument layer appear white
although some kernels might have some discolouration spots.
Starch from maize is obtained by the wet milling process. The process involves cleaning grains,
steeping, milling, separation of husk, germ, and gluten, and drying the product.Wet milling or the
classical milling process is the only process for making starch, universally in commercial use.
Starch manufactured by this process can be used by textiles, paper, and food industries. Starch
may be dry milled using screening and air - classification of particle size, but this process does
not separate oil, starch, and hull and can only be used by the food industry. Better separation is
obtained by wet - milling. To better understand the milling process, it is necessary to examine the
structure of the corn kernel (Taylor & Francis, 2002).
MATERIALS AND REAGENTS
a) For sorghum tannins
- Shaking water bath
- Glass beaker with screw lid
- Tea strainer
- Paper towel
- 5g Sodium hydroxide dissolved in 100ml of 3.5% sodium hypochlorite sodium
- Sodium hydroxide pellets
b) for wet milling
- Centrifuge
- Sieve
- Distilled water
- Beakers
- Potassium metabisulfite
- Maize grains

METHODS
A) For sorghum tannins
100 sorghum grains were put in a beaker and bleaching agent was added to cover the sorghum
grains and then the beaker was closed with a lid. The beaker was incubated at room
temperature(20-30°C) for 20 mins, swirling the contents at 5 minutes intervals. After 20 mins
elapsed, the contents in the beaker were emptied into a tea strainer, discarding the bleaching
reagents. The sorghum grains in the tea strainer were rinsed with tap water and the contents of
tea strainer were emptied onto a sheet of paper towel. The grains were spread out into a single
layer and were gently blotted dry with another piece of paper towel. The tannin sorghum grains
which were black over the entire surface of the grain were counted and the non-tannin sorghum
grains which were completely white or slightly yellow or coloured were also counted.
A) For wet milling
Maize steeped into distilled water was removed and grounded on a mortar by pestle. The mass
(500g) was dispersed in distilled water and the floating germ was removed after letting the
suspension stand for a while. The clear supernatant was decanted and the remaining mass wet
milled again. The suspension was filtered through a sieve and the throughs were collected and
centrifuged after transferring the glass into a large size centrifuge tube for 3-5 mins. The brown
protein layer was scarped carefully after centrifuging using a spatula. The white precipitate layer
was resuspended in distilled water, centrifuged and the brown layer was scarped off till it was all
removed. The starch granule mass was dried in an oven.

RESULTS
a) For sorghum tannins
Table1.number of sorghum kernels used
Duplicate 1 Duplicate 2
Sorghum kernels used 100 100
Tannin sorghum grains 0 0
Non- tannin sorghum grains 100 100
Tannin sorghum grains %= 0/100×100= 0%
Non-tannin sorghum grains %= 100/100×100= 100%
 The batch is non-tannin sorghum, contains ≥100% non-tannin sorghum
b) for wet milling
Fig1.maize steeped in distilled water

Fig2. dried starch granule from grounded maize

Mass of starch granule after drying= 105.10g

Yield percentage= 105.10g/500g×100= 21.02%

DISCUSSION
A) Discussion for sorghum tannins
The results obtained from the Clorox bleach method unequivocally show that the analyzed
sorghum batch, represented by both Duplicate 1 and Duplicate 2, consists entirely of non-tannin
sorghum grains. No traces of tannin-containing sorghum were detected in either sample.
According to Meena et al. (2022) this discovery has significant implications for a variety of uses
and industries that depend on sorghum with tannin properties. Because it does not contain
condensed tannins, which can affect things like color, flavor, and nutritional value, non-tannin
sorghum is frequently preferred. As a result, the batch examined in this experiment is suitable for
uses that favor sorghum free of tannins.
Even though the results show that there was no tannin-containing sorghum in the tested samples,
it is important to note that this conclusion relies on the Clorox bleach method's sensitivity and
accuracy within the detection limits. A bigger batch size or the requirement to assure uniformity
across a broader population of sorghum may call for additional testing and quality control
procedures (Awika et al., 2005).
B) discussion for wet milling
Figure 1 represents the initial step in wet milling, where maize kernels are immersed in distilled
water. The purpose of steeping in wet milling is to soften the kernels, hydrate them, and promote
the separation of various components, particularly starch, protein, and fiber.
In figure 2, the mass of starch that was obtained after drying was 105.10g, which is a success
because starch was extracted from the maize. According to Paraginski et al. (2014) starch is the
main constituent of maize kernels, about 72–73% of the total weight while in our experiment a
percentage of 21.02% was obtained from a divided portion of 500g of maize.

CONCLUSION
The experiments' findings demonstrate that the sorghum batch under evaluation only contains
non-tannin sorghum grains. The significance of the Clorox bleach method for easy and cheap
tannin detection in sorghum is demonstrated by this information, which is useful for companies
and applications that require sorghum properties. To guarantee the consistency and correctness
of this procedure in a larger context, additional study and validation may be required.
The results of wet milling, as presented in these figures, suggest that the process has been
successful in isolating starch from maize. Steeping the maize in distilled water and then drying
the starch granules have led to the separation and concentration of starch.

ANSWERS TO QUESTIONS( sorghum tannins)

1. processing techniques, maturity of wheat, storage conditions
2. -Excessive Heat: Elevated temperatures during any stage of processing, including drying
and storage, can lead to the destruction of yellow pigments. Careful control of
temperature is essential to prevent heat-related pigment damage.
-Excessive Moisture: High moisture levels can lead to enzymatic and chemical reactions that degrade
yellow pigments. Ensuring that wheat is properly dried and stored under controlled humidity conditions
is vital.

-Prolonged Storage: The duration and conditions of storage can influence pigment stability. Extended
storage periods under unfavorable conditions, such as high humidity or temperature fluctuations, can
result in pigment degradation.

-Exposure to Light: Light exposure, particularly UV light, can lead to the destruction of yellow pigments.
Proper packaging and storage in a dark environment are necessary to prevent light-induced pigment
degradation.

3. - Carotenoids and Vitamin A: Yellow pigments in pasta are frequently derived from
carotenoids, such as beta-carotene, which are natural plant pigments responsible for the
vibrant yellow and orange colors in various fruits and vegetables. Beta-carotene is a
precursor to vitamin A in the body. When we consume pasta enriched with carotenoids,
our bodies can convert these compounds into active vitamin A. Vitamin A is essential for
 maintaining healthy vision, supporting the immune system, and promoting proper cell
growth and differentiation.
- Dietary Fiber and Whole Grains: In many cases, yellow pasta is made from whole-grain
durum wheat, which retains the bran and germ layers in addition to the endosperm. These
whole grains provide dietary fiber, vitamins, minerals, and other health-promoting
compounds. The yellow pigmentation, often associated with whole-grain pasta, signifies
that pasta is a good source of dietary fiber. Dietary fiber is important for digestive health,
as it aids in regular bowel movements and can help prevent constipation
4.- Quality Control in Food Production: The presence of pigmented layers in sorghum can affect
the quality of products derived from sorghum, such as flour, food products, and beverages.
Identifying the brown pigmented inner integument layer can help producers and processors
ensure product quality and consistency. Different applications may require sorghum with specific
pigmentation attributes for optimal results.
5. no
6.- Improved Nutritional Value: Non-tannin sorghum grains tend to have a higher nutritional
value compared to their tannin-containing counterparts. The absence of condensed tannins means
that non-tannin sorghum can be more easily digested, allowing for better absorption of essential
nutrients, such as proteins and amino acids.
7. - Colorant and Aesthetic Value: The colored nature of non-tannin sorghum can provide
aesthetic value in food and beverage products. The naturally occurring colors can be used as
natural food colorants, reducing the need for artificial additives
ANSWERS TO QUESTIONS (WET MILLING)
1.- dry milling is aimed at separating grains into its anatomical parts while wet milling is aimed
to separate the grains into its chemical components(starch,proteins,oil,fiber)
- In wet milling, the grain is soaked or steeped in water or another liquid, which adds significant
moisture to the process while in dry milling the grain is processed without added moisture. The
method involves grinding the grains into a dry powder
2. -to break down disulfite bonds in maize proteins to make it easier to free starch granules
-prevents the growth of putrefying microorganisms
3.- centrifugation
Purpose: To separate components based on density.
Method: A high-speed centrifuge is employed to spin the mixture. This action separates the
components based on their varying densities. In wet milling, centrifugation is often used to
separate protein, germ, and starch.
- Filtration:
Purpose: To separate solids from liquids.
Method: A filter is used to separate the solid particles from the liquid. The filtered liquid can be
further processed or used as a byproduct, while the collected solids often contain starch or other
components.
4. The size of maize starch granules can vary, and they typically fall within a range of
approximately 2 to 30 micrometers in diameter. Maize starch granules are generally classified
into different size fractions, such as A-type, B-type, and C-type granules. The A-type granules
are the largest, often exceeding 20 micrometers, while the B and C-type granules are smaller,
with B-type granules typically ranging from 5 to 15 micrometers, and C-type granules being the
smallest, typically below 5 micrometers in diameter.
5. -Gelatinization and Structural Changes, color changes,flavour and aroma changes

6.
Figure 3. Diagram for corn wet-milling process flow to extract corn. . . (n.d.). ResearchGate.

https://www.researchgate.net/figure/Diagram-for-corn-wet-milling-process-flow-to-

extract-corn-starch-and-output-products_fig2_357401789

7.free from contaminants,uniformity and consistency,moisture content=14-16%

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