Effect of Process Conditions on Soymilk Storage Stability
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Date
2018-11
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Addis Ababa University
Abstract
Effect of process conditions such as soaking time (ST), germination time (GT) and grinding
cum blanching temperature (BT) on physicochemical characteristics, proximate composition,
microbial stability and sensory acceptability of soymilk was studied during 21 days of cold
storage (4ºC). Soymilk was prepared from soybean (Clark 63k) using a combination of
Cornel and Deodorization methods of soymilk processing. Sprouted and un-sprouted soybean
seeds were subjected to a combination of process conditions namely: soaking time (8h and
24h) and grinding cum blanching temperature (90°C and 100°C) used for soymilk
preparation. Soymilk prepared by traditional method and the reference of USDA nutrient
requirement were used as control. Soymilk from sprouted soybean seeds showed an increase
in protein content (wb) of 12%, a reduction in fat (wb) of 17% and phytate (db) of 15%.
Physicochemical characteristics, microbial load and proximate composition of soymilk
showed significant difference (P<0.05) between treatments and during storage time. Good
physical stability showed on soymilk prepared from sprouted soybean during 21 days of cold
storage. Response optimization result in optimal soymilk process conditions (ST= 24h,
GT=72 h and BT= 100°C), (ST= 8h, GT = 0h and BT= 100°C), (ST= 24h, GT= 0h and BT=
90°C) and (ST= 24h, GT= 72h and BT= 90°C) selected based on maximum value of viscosity
and colour (whiteness) value of soymilk samples. Soymilk samples were within allowable
microbial limit during 7 days of cold storage with comparable pH of fresh cow milk.
Validation of the optimal process from sensory panellist perspective indicated that there were
no significant (P>0.05) differences between samples on overall liking. Thus, soymilk from
sprouted soybean seed (ST=24h, GT=72h and BT=100°C) was selected as acceptable with
better storage stability, nutritional / anti-nutritional profile and physicochemical
characteristics as confirmed by sensory acceptance. The result clearly showed 70%
acceptance and 65% purchase intent of the soymilk. The improvement in proximate
composition was seen in soymilk from sprouted soybeans, showing that sprouting could be
beneficial for preparing soymilk with higher nutritional and lower anti-nutritional profile.
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Keywords
Physicochemical Stability, Process Conditions, Sensory Analysis, Soymilk, Soymilk Optimization, Storage Stability