only vegetable food that contains all eight essential A m
a . These are also excellent
sources of fiber, iron, calcium, zinc and B V
i
T .
23.3.2 Wheat
Based on solubility, the wheat p
R
t fractions are classified as, albumins (water soluble), globulins (dilute salt solutions soluble), gliadins (soluble in 70–90% ethanol,
glutenin (insoluble under all the previously mentioned conditions, comprise 34% of
total p
R
t ) and comprise 47% of the total p
R
t ). Gliadin (40 kDa) have four distinct
fractions, a single chain P E
pt , and containing intermolecular disulfide bonds. These
play an important role in strength, film formation, strength and elasticity. A mixture
of p
R
t , Glutenin, has a molecular weight distribution between 100 and 1000 kDa.
The strength of the p
R
t matrix determined by the disulfide bonds present in gliadin
and glutenin (Fig. 23.3).
23.3.3 Corn Zein
A class of prolamin p
R
t , Zein, found in maize (corn). It is a powder from corn gluten
meal, one of the best P
l
T p
R
t . Pure Zein is clear, tasteless, water-insoluble, odorless,
hard, and edible. High percentages of non-polar A m
a , like leucine (20%), glutamine
(26%), proline (10%) and also basic and acidic A m
a in low proportions contained by
Zein. Two major fractions of Zein are a-Zein, soluble in 95% ethanol and b-Zein
soluble in 60% ethanol. Commercially, it is used for coating of tablets and in
biodegradable packaging.
Fig. 23.3 Composition of wheat protein
23 Protein and Enzymes Isolated from Plant Sources …
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