Date of Award

1994

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

School of Nutrition and Food Sciences

First Advisor

Douglas L. Marshall

Abstract

Impedance technology is currently used as a measurement of microbial activity. The purpose of the current study was to determine the feasibility of utilizing impedance technology to evaluate the quality of white shrimp (marine species) and channel catfish (freshwater species). Impedance analysis measurements (I-values) of raw shrimp increased for samples stored at 5, 25, and 35$\sp\circ$C; however, control samples stored at $-$20$\sp\circ$C displayed no significant changes in I-values. I-values from thermally processed shrimp had no direct relationship with odor scores, increased storage time, or increased storage temperature. It was concluded that while impedance measurements were able to indicate the degree of raw shrimp quality, they were ineffective for determining the quality of cooked shrimp. Methods currently utilized in this study to determine quality include degradation product measurement, odor analysis, psychrotrophic bacterial enumeration, and pH. Comparisons of raw shrimp I-values and odor scores demonstrated a strong relationship, particularly with increased storage time and temperature. Impedance analysis of channel catfish demonstrated no relationship with other quality indicators. Measurements of the nucleoside inosine correlated highly with odor scores, which demonstrated that inosine quantification has the potential for use as an indicator of catfish quality. The effect of rigor mortis on impedance measurements was also examined in this study. While rigor mortis occurred in catfish muscle within the first 5 hours postmortem, no relationship was established with impedance. This study demonstrated that impedance can measure shrimp quality, but not catfish quality, and that the nucleoside inosine could be a potential indicator of catfish quality.

Pages

136

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