Masters Theses

Date of Award

3-1972

Degree Type

Thesis

Degree Name

Master of Science

Major

Food Science and Technology

Major Professor

J.L. Collins

Committee Members

J. Owen Mundt, Ivan E. McCarty

Abstract

This study was designed to develop a shelf stable and acceptable intermediate moisture product using dry extruded textured vegetable protein chunks as the food base. The water activity of the protein chunks was adjusted to 0.85 and 0.80 by cooking in solutions of sorbitol, sodium chloride, propylene glycol, sucrose and potassium sorbate. The effects of calcium lactate and a lower pH on the properties of the protein product were determined. Products prepared at 0.85 Aw consisted of four treatments: 1) without calcium lactate, pH 7.0; 2) without calcium lactate, pH 5.5; 3) with calcium lactate, pH 7.0, and 4) with calcium lactate, pH 5.5. One the products at 0.80 Aw, only two treatments were tested: 1) without calcium lactate, pH 7.0 and 2) without calcium lactate, pH 5.5.

The samples were packed in sterile air-tight jars and held at 27.6o C for sixty days. Storage stability was studied by determining the microbial, physical, and chemical characteristics of the product at ten-day intervals. Overall acceptability was evaluated on the freshly prepared product by the hedonic-preference test. Samples were prepared at water activities of 0.80 and 0.70 and deep-fried before sensory evaluation. A difference-preference test was also conducted to evaluate sensory attributes on texture, moistness, and flavor.

Products at 0.85 Aw were susceptible to mold growth. The bacterial growth curve was fairly rapid during the early storage period and the microbial flora was predominantly Pseudomonas spp. When water activity was lowered to 0.80, mold growth was completely inhibited and bacterial growth was greatly hindered. Pseudomonas spp. was in the majority at the initial stage; however, members of the Family Achromobactereceae soon outgrew the Pseudomonas spp. and dominated throughout the remaining storage period.

Calcium lactate lowered significantly the water activity, moisture content and pH of the intermediate moisture product. No significant change in color was observed; however, there was an increase in firmness.

The lowering of pH to 5.5 caused a decrease in water activity and moisture content of the product with target Aw of 0.85. Shear resistance was significantly increased. Color of the protein chunks was lighter at pH 5.5 than at pH 7.0. Similar trends on water activity, moisture content, firmness and color were observed in products lowered to 0.80 Aw; however, no significant difference was established between the two pH levels.

There was an overall increase in water activity of the intermediate moisture product at both levels of water activity as storage time increased. However, moisture content decreased in products at 0.85 Aw while it increased at 0.80 Aw. In samples at 0.85 Aw, a gradual decrease in pH was observed during storage. The stored product had a slightly higher shear value than the fresh product while its color was not changed.

Results of the preference test indicated that deep-fried textured vegetable protein chunks were an acceptable product. It had a predominant sweet taste and a slightly detectable bitter and burning aftertaste; however, these effects were more pronounced in samples at Aw of 0.70 than at 0.80. Protein chunks at 0.80 Aw were rated slightly tougher and drier than those at 0.70 Aw.

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