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The Effects Of Different Processing Techniques On The Organoleptic Quality Of Soy Milk
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Although the Chinese and Japanese have covered soybeans into a variety
of products most of these foods have little physical or flavour identity
with the original bean. Some people agree that green soybean are a
delicious dish when properly harvested and cooked but their sale and the
sale and the ale of mature beans for baking are extremely small.
Soybean products have problems related to their flavour and flavour
stability to their ruction in foods and to their physiological effects.
Despite these problems soybean oils have become a major material in our
food industry. Soybean now supply more than half of the total visible
fits and oils consumed in the U.S.A
Soybean composition (PREXIMATE),
commercial soybean constitute and 2% hypocotyls and phumule. Proximate
composition for whole beans and fractions are given in Table 1
1.2 PROXIMATE COMPOSITION OF SOYBEANS AND SEED PARTS
Fraction Protein (Nx 6.25) Fat % Carbohydrate % Ash %
Whole bean 40 21 34 4.9
Cotyledon 43 23 29 5.0
Hall 8.8 1 86 4.3
Hypocotyls 41 11 43 4.4
The
constituents of major interest oil and protein make-up about 60% of the
bean, but about one third consist of carbohydrates including
polysaccharides, stachyose (3.8%), raffinese 1.1% phosphatides, sterols,
ash and other minor constituents are also depend on variety, soil
fertility and weather conditions.
1.3 NUTRIENTIONAL PROPERTIES OF SOYBEAN
Over
50 years ago Osborne and Mendel (1980) found that rates grew poorly
when feed with raw soybean meal and that dry head did not improve the
nutritional value of the meal.
Rates grew normally, however when the
meal was cooked on a steam for 3hrs. In the past 50yrs a vast literature
was developed on the nutritive properties of soybean protein, but moist
heat is still used to improve the nutritional quality of soybean
protein product for foods and feeds.
The literature on this subject
is often confusing and contradictory ; two recent reviews gives concise
summaries of pertinent work for the last 30yrs. Alleged antinutritional
factors and protein quality therefore are discussed only briefly.
1.4 ANTINUTRITIONAL FACTORS
Since
moist heat readily inactivates the anti-growth factors raw soybean
meal, many workers believe that the factors are proteininhibitors and
hemagluthins, non protein components such as sapynins have b suggested
as anti-nutritional factors but recent work does not support this view.
1.5 TRYPSIN INHIBITORS
More
than five trysin inhibitors are reported for soybeans but only two-the
kenitz and the Bowman Birk inhibitors have been purified and studied in
details Kaw soybean meal contains 1.4% kunity inhibitor and 0.6^
Bowman-Birk inhibitor.
Although both inhibitors are active against
boline trypsin the kunity inhibitor has any how activity the esterase
activity of human trypsin. The activity of human trypsin however is
inhibited to a significant extent by kunity inhibition when case is sued
as a substrate to measure proteolytic activity. It is not known whether
ingestion of the inhibiters affects the presence in humans.From the
practical standpoint, Trypsin inhibitors do not appear to be a serious
problem in feeds and food since they are largely inactivated by moist
heat. Condition of heating time, temperature, moisture content and
particle size influence the rate and extent of trypsin inhibitors
inactivation for example, atmospheric steaming (1000C) inactivates more
than 95% of the trypsin inhibitor activity of raw, defatted soybean
flakes in 15mins. Protein efficiency shows an accompanying increase in
this same time and flakes of 19% moisture gave a higher protein
efficiency ratio than flakes of 5% moisture. In contrast, steaming whole
soybeans chips, or cotyledons for 20mins only partially inactivated
trypsin inhibitors apparently because of the large particle size.
Atmospheric steaming inactivates most of the trypsin inhibitor in whole
soybeans in 15mins. In initial moisture content is 20%. If the beans are
soaked in water overnight 60% moisture 25mins. In boiling water
sufficient to inactivate the inhibitors. Small bu
the measurable
trypsin inhibitors activity can often be deflected after heating the
known stability of Bowman-kirk inhibitor suggested that the residual
inhibitor may be of this types. Measurements of residual chymotrypsin
inhibitor activity would clarify this point because the Bowman-kirk
inhibitor is a strong inhibitor of chymotrtpsin.
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