Ultrastructural - Biochemical Changes and Sensory Correlations in Shrimp During Cold Storage.

Ultrastructural-biochemical changes and sensory correlations of penaeid shrimp during iced and frozen storage were analyzed. The aroma, color and acceptability of wild shrimp, P. setiferus from the Gulf of Mexico, were judged by six trained panelist to be superior to that of the pond-raised shrimp, P. stylirostris. However, P. stylirostris on the Master Mix Shrimp Diet has a slightly superior flavor than those fed with the Marine Ration 20 diet. Free amino acids, proline, glycine, taurine, and glutamic acid declined during the first 10 days of ice storage, and increased after 20 days. Leucine, and lysine increased linearly during ice storage (0-30 days). However, threonine, and arginine significantly (P \u3c 0.05) decreased from 0-20 days of ice storage with a concurrent increase in the amino acid reducing enzymes. The increased concentration of free amino acids, loss of materials of Z-lines and thin filaments caused textural changes during ice storage. In contrast, during frozen storage, denaturation of protein, broadening of Z-lines, the shortening of sarcomere lengths, and contraction of muscle resulted in hardening of shrimp myofibrillar proteins. During frozen storage, the percentage of saturated and monosaturated fatty acids decreased slightly after 2 months and increased after 6 months. Polyunsaturated fatty acids, C18:2, increased significantly (P \u3c 0.05) in 2 months and decreased significantly from 2 to 6 months during frozen storage. Generally, all of the free amino acids decreased during frozen storage regardless of the duration of icing prior to freezing. Similarly, the ice treatments (0, 10, 20 days) prior to freezing did not have a detrimental effect on fatty acids of the frozen shrimp. Practices are suggested that include freezing shrimp prior to 10 days icing and use of enzyme inhibitors to prolong shrimp quality during icing. In view of the increasing importance of aquaculture, modification of diets may be an important factor in improving ultimate shrimp flavor. Data from the present study showed correlations between shrimp flavor and ultimate potential monetary value of the shrimp product