Factors Associated With Microbial Growth in Ground Beef Extended With Varying Levels of Textured Soy Protein

Abstract

Three separate batches of ground beef containing 25% fat were extended to 0, 10, 20 and 30% by weight with rehydrated defatted textured soy protein (TSP). Five samples of each soy level were wrapped in a polyethylene oxygen-permeable film and stored at 5°C for 4 days. Samples were analyzed daily for changes in bacterial numbers (total plate counts and coliforms), pH, titratable acidity, proximate analysis, ninhydrin reactive material, carbohydrate content, and gas liquid chromatographic (GLC) analysis of individual amino acids to assess spoilage in TSP extended ground beef. Total bacterial numbers increased significantly as days of storage progressed and in proportion to added TSP. Coliforms increased during storage, but not proportional to increased levels of soy protein. Spoilage in soy extended samples, as determined by off-odors and bacterial numbers, was evident by day 4 as total bacterial counts approached 10" bacteria/g. The differences of pH were significant among soy levels, but did not change appreciably during storage. Titratable acidities were not significantly changed with increases in soy protein. As soy level increased, percentages of moisture and ash increased, but percent fat decreased. No differences were noted for percent protein. Total carbohydrate as determined by proximate analysis increased with TSP levels. Concentration values for carbohydrates were proportionately larger with added amounts of TSP, but varied little during 4 days of storage. Ninhydrin reactive material differed significantly among samples, but not proportionate to added TSP, and decreased in the 30% soy level between days 3 and 4. Decreases in individual amino acids could not be shown from the qualitative results obtained by GLC analysis. Further investigation is suggested using more definitive measuring techniques to determine the factor(s) causing accelerated spoilage in soy extended ground beef.

Effect of Defatted Melon (Citrullus Vulgaris Schrad.) Kernel Flour Supplementation on the Storage Stability and Microbiological Quality of Refrigerated Beef-Based Sausages

“…This may be attributed to increased availability of carbohydrate for lactic acid bacteria (particularly in weeks 1 and 2) in samples containing higher levels of melon. Similar results for soy extended ground beef were obtained by Keeton and Melton (1978). Variation in the bacterial growth between levels of extension and storage period could be attributed to the differences in pH and water‐holding capacity, both of which were affected by level of melon addition.…”

Soy Protein and Oil Effects on Chemical, Physical and Microbial Stability of Lean Ground Beef Patties

“…However, Foster et al (1978) showed no significant differences between soy extended ground beef and 100% ground beef for mesophillic, psychrotrophic, and coliform organisms. Keeton and Melton (1978) showed coliform counts were significantly higher in textured soy protein extended ground beef after one day of storage in comparison to the 100% ground beef. In our study, no differences (P~0.05) were found among ground beef pattie treatments for coliform, aerobic and psychrotrophic plate counts (data not shown).…”

Chemical, physical, microbiological and quality attributes studies on River Nile crayfish

“…The pH value was measured in samples according to the method described by Krilova and Liskovskaia (1961) using a Beckman pH meter with a combined electrode and acidity was determined according to Keeton and Melton (1978). …”