Degree Type

Dissertation

Date of Award

1981

Degree Name

Doctor of Philosophy

Department

Food Technology

Abstract

Various aspects of freezing preservation and packaging methods were studied for feasibility of use for beef and poultry in practical applications;Investigations on the effects of combining fresh and frozen beef in different proportions showed that a 50:50 ratio of fresh to frozen beef produced higher bacterial numbers than observed when other proportions were combined and held in frozen storage. No health hazard was evident from any of the different combinations of fresh or frozen beef or from liquid nitrogen or liquid CO(,2) freezing and frozen storage. Changes in bacterial flora as a result of freezing and frozen storage were studied by classifying the isolates into phenotypic groups with the help of replica plating and computerized cluster analysis. Reference cultures were used to identify the clusters. The Moraxella-Acinetobacter group increased considerably in percentage of total isolates after freezing, with a decline during frozen storage. A concomitant increase in the Pseudomonas group of organisms occurred during frozen storage. Certain characteristics of the bacterial flora that were related to spoilage of beef such as lipolysis of beef fat and proteolysis became more pronounced after frozen storage. These changes generally followed the pattern of alterations in the proportions of Pseudomonas to other groups;Studies on the effects of packaging materials and methods on shelf life of chicken showed that a high barrier (vacuum package) material provided greatest restriction of bacterial multiplication, a low barrier (vacuum package) was next effective and a stretch wrap in a tray (air pack) was least effective. Chlorine at a level of 20 ppm as a dip did not provide increased storage life compared with vacuum packaged chicken maintained in the dry state during storage at 5(DEGREES)C. All cut-up poultry spoiled faster than any of the whole birds. Cutting operations increased the incidence of Salmonella and coagulase positive staphylococci on chicken;Investigations on the effects of cryogenic and conventional freezing methods on factors related to quality of turkey meat indicated that all freezing methods caused an increase in Myofibril Fragmentation Index, a measure considered to be associated with tenderness of meat. Conventionally frozen turkey meat had higher fluid losses than meat frozen by liquid nitrogen.

DOI

https://doi.org/10.31274/rtd-180813-4637

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Kuruganti Venkatakrishna Reddy

Language

en

Proquest ID

AAI8122557

File Format

application/pdf

File Size

196 pages

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