Date of Award

12-1980

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Human Ecology

Major Professor

Ada Marie Campbell

Committee Members

Marjorie P. Penfield. Frances E. Andrews, David W. Brown

Abstract

The substitution of soy protein concentrates for soy flour in a USDA formulation for corn-soy blend and fortification with four calcium salts were investigated by functional, nutritional and preliminary sensory evaluations. A model system was used in an investigation of water absorption and Brookfield consistency of 4 soy concentrates, 2 powders and 2 grits, in the presence of calcium carbonate, calcium phosphate dibasic, calcium phosphate tribasic and calcium lactate, at levels of 0, 400, 800 and 1200 mg calcium/23.4 g concentrate and at 0 0 ambient temperature (22-25° C) and 50° C. One powder and one grit concentrate were selected for use in a corn-soy cereal. Cereals representing all combinations of the 2 concentrates with the 4 calcium salts at levels of 0, 400, 800 and 1200 mg calcium/100 g cereal were evaluated at 50° C for water absorption and Brookfield consistency; the cereals also were evaluated for Bostwick and Brookfield consistency after cooking and cooling to 30° C. Cereals representing all combinations of the same concentrates and all 4 calcium salts at a calcium level of 540 mg/100 g diet were evaluated for nutritional quality by PER assay. One of the 2 concentrates, the powder, was tested in gruels containing all 4 calcium salts at a calcium level of 540 mg/100 g cereal. A panel of adults evaluated the gruel by the consumer texture profile technique and assessed the cereals' apparent acceptability when fed to infants.

The effects of soy concentrate were similar in the model system and the uncooked food system; grit concentrates and the uncooked cereal containing grit concentrate absorbed more water and had greater suspension consistency than counterpart powder concentrates and cereal containing powder concentrate. However, in the cooked food system, the gruel containing powder concentrate was more viscous than the gruel containing the grit concentrate. The effect of temperature on both water absorption and Brookfield consistency in the model system was evidenced by greater values at 50° C than at ambient temperature.

Calcium salts had a significant effect on both water absorption and Brookfield consistency in the model system, whereas this effect was evident only for water absorption in the uncooked food system and for Brookfield consistency of the cooked gruel. Concentrates in the model system tended to absorb the most water in the presence of calcium carbonate and calcium phosphate tribasic and their suspensions were most viscous in the presence of calcium phosphate tribasic. Cereals containing calcium carbonate absorbed the most water and were the most viscous when cooked. Calcium lactate had the same effect in both systems; the least water was absorbed and suspensions were the least viscous in the presence of this salt. Both water absorption and suspension consistency tended to decrease with increasing level of calcium in the model system but calcium level did not affect the food system.

The numerous interactions observed in the model system indicate that the relationships among the variables studied are complex. Some possible effects of the variables and interactions in the food system possibly were masked by the presence of pregelatinized corn meal in the cereal.

Nutritional quality of the cereals was not affected by soy concentrate or by calcium salt. PER values for soy concentrate-calcium salt diet combinations ranged from 2.24 to 2.34 (based on 2.5 for casein). Sensory properties of the gruel were somewhat affected by calcium salt.

It was concluded on the basis of consistency and PER that either the grit or powder soy protein concentrates could be used to replace the less refined and processed soy flour in USDA' s corn-soy blend. However, the calcium salt used for fortification needs to be selected with consideration of desired functional and sensory properties of the final product.

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