Peroxidase is one of the most heat resistant enzymes and may cause undesirable quality changes in thermally processed foods. Peroxidase activity and its resistance to thermal inactivation in fresh and pasteurized lump, claw and flake meat of both male and female blue crabs was determined spectrophotometrically. Activity was greatest in the flake and least in the claw. Male crabs usually exhibited a greater initial activity (λ 0D 460/min) than did females of equal size. The larger the crab for a given sex, the greater the initial activity. Eight isozymes of peroxidase were detected in raw extracts of a 115 g female blue crab following starch gel electrophoresis and nine in a 116 g male. A smaller female crab (96 g) revealed seven bands which were less intense than those of larger females. By extending the time of electrophoresis, twelve bands were detected in the gel containing an extract from the 96 g female crab. The optimum thermal processing times needed to denature peroxidase and to prevent regeneration were studied. Heat inactivation curves indicated two straight line decreasing segments which varied by rate of descent. The first segment which decreased at a faster rate was considered due to heat-labile isozymes and the second segment which decreased at a slower rate due to heat stable isozymes. D values obtained for the enzyme based on the second straight line segment were D80=47 min, D110=18.2 min and D150=11.2 min. A "z" value of 92 F was also obtained for the enzyme. / Master of Science

This study was conducted to determine the quantities of Campylobacter jejuni, Campylobacter coli, Salmonella, fecal positive Klebsiella pneumoniae, and Escherichia coli 0157:H7 in fresh hand picked blue crab (Callinectes sapidus) meat. An attempt was made to correlate these selected pathogens and general microbial quality to processors Sanitation practices and facility size. Hand picked crabmeat samples from 12 blue crab processing facilities in the Chesapeake Bay region were collected and analyzed. Twenty samples from each of the different facilities were collected on different processing days. Facilities were chosen based on production levels and Virginia Department of Health inspection scores as an indicator of sanitation practices (excellent ≥ 94.5, acceptable < 94.5). All samples were tested between 16 h and 36 h after collection. Campylobacter jejuni was isolated from 36 (15%) of the 240 samples and Campylobacter coli was isolated from 14 (5.8%). Quantitative levels in all case were below limits of detection (<0.30 MPN/g). Klebsiella pneumoniae was isolated from a total of 51 (21%) samples. Counts ranged from less then 0.30 to 4.3 MPN/g. Aerobic plate counts ranged from 7.4x10³ to 4.6x10⁸ CFU/g with coliform counts ranging from <0.3 to 32.8 MPN/g. Fecal coliform levels were <0.3 to 2.26 MPN/g and Escherichia coli from <0.3 to 0.77 MPN/g. Salmonella and Escherichia coli 0157:H7 were not detected in any of the 240 samples analyzed. No significant differences (p<0.05) between size and inspection scores were observed for general microbial quality, the presence of Klebsiella pneumoniae, or Campylobacter species. / Master of Science