Effect of Delayed Icing on the Quality Changes in Brackish water Shrimp Penaeus
monodon During Ice Storage
Md. Nazrul Islam
The effect of delayed icing on the quality of ice-stored Brackish water shrimp (Penaeus monodon) was investigated by determining organoleptic, biochemical and bacteriological aspects. The live shrimp samples stored in ice immediately after harvest were organoleptically acceptable for 10 days while delay in icing for 4, 8 and 12 hrs shortened the shelf life to 7, 6 and 5 days, respectively. The initial pH of the live shrimp muscles was 6.63 which increased to 7.28 after 10 days of ice storage while in samples delayed in icing for 4, 8 and 12 h pH increased to 7.85, 7.93 and 7.95, respectively at the end of 10 days of ice storage. TVB-N value was increased from 5.88 to 32.76 mg/100g after 10 days of ice storage. The peroxide values in all the samples were lower than 8 meq/kg of oil upto 5 days of ice storage and then increased gradually with the lapse of storage period. The myofibrillar Ca2+-ATPase activity in presence of 0.5M KCl showed the maximum remaining activity of 0.52 μmol pi/min.mg in live samples stored in ice immediately after catch. The myofibrillar solubility of samples immediately after catch was 80%, which decreased around 50% during 10 days of storage. On the other hand, the solubility of the samples kept at room temperature for different periods prior to icing were around 70% which decreased considerably to about 40% during 10 days of storage. The aerobic plate count (APC) increased considerably in the samples kept at ambient temperature for longer period prior to icing. The composition of bacteria in samples was Coryneforms (8.33%), Bacillus (7.40%), Micrococcus (16.66%), Achromobacter (8.33%), Flavobacterium/Cytophaga (25%), Pseudomonus (25%) and Vibrio (8.33%). Shrimp samples iced at 4,8 and 12 hrs delay dominated mostly by Micrococcus with 60%, 57.14% and 46.66%, respectively. During subsequent storage for 7 days, Micrococcus and Achromobacter were dominant in all the samples. However, Enterobacteriaceae was found in samples delayed 8 and 12 hr prior to icing.
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