Physical and Chemical Characteristics of Cow's Milk Extended With Soymilk
Wondafrash, Teshome
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Permalink
https://hdl.handle.net/2142/70070
Description
Title
Physical and Chemical Characteristics of Cow's Milk Extended With Soymilk
Author(s)
Wondafrash, Teshome
Issue Date
1982
Department of Study
Food Science
Discipline
Food Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Food Science and Technology
Abstract
Cow's milk products, nonfat dry milk or fresh skim milk, and specially prepared soymilk were separately standardized at 3.0% protein. Blends of cow's milk with 0-100% soymilk were made. Lipids with or without emulsifier and/or salts (all at 0.01M) of CaCl(,2); Na(,2)HPO(,4); CaCl(,2) with Na(,2)HPO(,4), and Ca(,3)(PO(,4))(,2) were used. The Na(,2)HPO(,4) and Ca(,3)(PO(,4))(,2) products were pasteurized at 80(DEGREES)C, or were Agitort sterilized at 121(DEGREES)C for 8 min. Samples were stored at 4 and 40(DEGREES)C for 0 to 60 days and pH, viscosity, solubility index, solids and nitrogen dispersibility index observations were made.
Physicochemical characteristics of pasteurized beverages varied depending on the ratio of cow's milk to soymilk as well as on addition of lipids, emulsifier and salts. In general, the 25 and 50% soymilk blends showed an increase in pH. The 75% and at times the 50% soymilk blends showed increases in viscosity and solubility index. Increase in soymilk concentrations decreased solids dispersibility index to a minimum at 75% soymilk levels. The blends were intermediate in nitrogen dispersibility index, whereas the cow's milk was the highest and soymilk the lowest.
The most critical factor, sterilization, decreased pH, increased viscosity and solubility index, decreased solids dispersibility index and increased the nitrogen dispersibility index.
Salts were the second most critical factor. CaCl(,2) decreased and Na(,2)HPO(,4) increased the pH. Salts alone or with lipids and emulsifiers increased viscosity, solubility index, solids dispersibility index, and decreased the nitrogen dispersibility index.
Storage at both low and high temperatures significantly affected the sterilized beverages. The pH for 40(DEGREES)C stored samples dropped. The viscosity of beverages increased with high temperature storage. The solubility index of the sterilized samples slightly increased after low or high temperature storage. The solids dispersibility index increased during storage. The nitrogen dispersibility index appeared to decrease more at high than at low storage temperature.
Cow's milk products may be extended with up to 50% soymilk and fortified with lipids and calcium for nutritional improvement. However, the method of preparing soymilk, the quality of the cow's milk product, thermal sterilization and the type of added calcium salt are factors of critical importance if desirable physicochemical characteristics in the blend are to be maintained.
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