Influence of different processing methods on quality and shelf life of dried shrimp.
P.S. JAYASINGHE*, J.M.P.K. JAYASINGHE AND C.P. GALAPPATHTHI
Marine shrimp fishery contributes around 55% to the small shrimp production Sri Lanka. In addition to the targeted large shrimp for the export market, small shrimp are marketed locally as value added dried products. This activity has been established as a cottage industry. Development of optimum control conditions of processing is very important for maintaining nutritional quality of the dried shrimp. Present study was conducted to evaluate the effect of different salt concentrations, cooking methods, drying time and drying temperature on sensory properties of processed whole and peeled shrimp with a view to develop improved processing methods. In addition, sensory properties, total volatile nitrogen (TVN) content, trimethylamine (TMA) content and total bacterial count (TBC) of the processed whole and peeled shrimp which had been stored under different packaging systems viz. polythene bags, Styrofoam boxes and open bulk packages were assessed weekly for six weeks to determine the shelf life of the processed shrimp. The results revealed that the whole shrimp salted at 5% (w/w), pressure cooked for 20 minutes, dried at 70 0C for 2 hours and the peeled shrimp treated under the same conditions and cooked only for 10 minutes gave the best quality dried shrimp. TVN contents (in mg/100g) in whole dried shrimp packed in Styrofoam box, polythene bags and under bulk packages were 25, 34.5 and 39.5 respectively at the end of six weeks. TMA contents (in mg/100g) in whole dried shrimp stored in three types of packing systems mentioned above were 16.8, 21, and 26.3 respectively whereas TBC values (in cfu /g) for dried whole shrimp were 1.08 x 106, 1.08 x 106 and 1.66x 106. TVN contents (in mg/100mg ) in the peeled dried shrimp packed in Styrofoam box, polythene bags and under bulk packages were 27, 16.8, and 21 respectively whereas the TMN contents (in mg/100g) were 16.8, 15 and 25.2 at the end of the six weeks. TBC values (in cfu /g) of these processed peeled shrimp packed in Styrofoam, polythene and bulk packages were 5.88x 104, 1.66x 105 and 3.33x 105 respectively. Styrofoam package was found to be the most effective packaging system for both processed whole and peeled dried shrimp.