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The Effect of Soybean Pretreatments on the Quality of Soymilk
Thesis Abstract:
The study sought to determine the effect of hulling, cooking time and fermentation time on the quality of soymilk.
Results showed that total protein content, amino acid nitrogen viscosity, pH of soymilk before and after processing and general acceptability of soymilk formulated with 20% fresh milk were higher for unhulled than for hulled soybeans. The same parameters for soymilk formulated with 20 ppm vanilla decreased at 10 to 20 minutes cooking but increased as heating continued to 30 minutes. Fermentation time had no significant effect on the above parameters for soymilk formulated with 20 ppm vanilla from both hulled and unhulled soybeans. The bitter taste of fermented soybean, however, decreased the general acceptability of the soymilk produced.
The highest total protein content was derived from uncooked hulled soybeans fermented for 72 hours and from uncooked unhulled soybeans fermented for 24 hours.
The highest water soluble protein content came from uncooked hulled soybeans fermented for 24 hours and the highest amino acid nitrogen, from unhulled soybeans cooked for 30 minutes and fermented for 72 hours.
Unhulled soybeans cooked for 30 minutes and fermented for 24 hours gave the highest viscosity, while unhulled soybeans cooked for 30 minutes and fermented for 72 hours produced the most suitable pH of soymilk.
Hulled soybeans cooked for 30 minutes without fermentation merited the highest general acceptability of soymilk formulated with 20% fresh milk. Unhulled soybeans cooked for 10 minutes without fermentation, and uncooked, unfermented hulled soybeans produced comparably acceptable soymilk.