Graduate Thesis Or Dissertation
 

Frozen shelf-life characteristics of condensed phosphate treated Pacific shrimp meat (Pandalus jordani)

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  • The effect of the application of condensed phosphate (Brifisol D-510, commercial mixture of sodium tripolylphosphate and sodium hexametaphosphate) to round shrimp on the yield and frozen shelf-life characteristics of cooked meat was investigated. Condensed phosphate retarded protein solubilization and increased the water-holding capacity of meat through steam precooking markedly improving yield. The effectiveness of condensed phosphate application was enhanced by the post-catch degradative changes occurring in the shrimp musculature proteins during ice storage. Cooked meat yields (wet wt.) for phosphate treated round shrimp after two, four and seven days ice storage were 30.70±0.51%, 31.22±0.03% and 29.21±0.23%, while the yields from control samples were 26.52±0.18%, 27.14±0.01% and 23.85±0.09%, respectively. The phosphorus contents of cooked meat from control shrimp were 842.54, 726.08 and 577.74 mg P₂O₅/100 gm (wet wt.) after 2, 4 and 7 days storage in ice. Phosphate treatment produced an increase of 91.20, 134.34 and 184.68 mg P₂O₅/100 gm (wet wt.) over respective control samples. The loss of solid material retarded by condensed phosphate pretreatment and increased as ice storage was extended was inversely proportional to the iron and copper contents in cooked shrimp meat. Initial levels of tyrosine, trimethylamine oxide, trimethylamine and dimethylamine in cooked meat reflected the quality of round shrimp as mediated by ice storage. Differences were related to drip loss and bacterial and enzymic degradation. The level of tyrosine in cooked shrimp meat did not significantly change with respect to frozen storage time. A higher level of trimethylamine oxide was retained in the meat from phosphate treated shrimp than respective control samples. trimethlyamine oxide decomposed during ice and frozen storage; decomposition with respect to frozen storage time followed an exponential function. Differences in initial levels of trimethylamine in cooked meat were presumably related to the bacterial load in round shrimp. Condensed phosphate treatment reduced the trimethylamine contents of cooked meat. Dimethylamine levels increased during ice storage of the raw shrimp and frozen storage of the cooked meat which supports the existence of a non-enzymatic mechanism, but did not rule out an enzymatic mechanism in the raw tissue. Dimethylamine was formed in cooked meat according to an exponential function; the rate if formation was inversely related to the magnitude of solids lost through precooking. Dimethylamine was formed more rapidly in frozen cooked meat from fresh and phosphate treated shrimp. Condensed phosphate had a significant effect on retarding toughening during frozen storage as measured by shear press. Shear press values were correlated with dimethylamine content which is co-produced with formaldehyde. In all sensory evaluations, phosphate treated shrimp yielded cooked meat that possessed a higher quality than respective control samples. Sensory quality of cooked meat was slightly different at two and four day ice storage, but flavor panels showed a significant degradation after seven days ice storage. Color, flavor and overall desirability scores from shrimp were not correlated with frozen storage. Texture and juiciness scores did not significantly change as frozen storage was extended. The frozen storage stability of cooked meat from condensed phosphate treated shrimp did not appear to differ from that of non-treated.
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file details CHUTIENIU1981.pdf 2017-08-15 Pubblico Scaricare