| Microorganisms were isolated and identified from spoiled shrimp by selective media. The bacteria consistently identified from shrimp that spoiled at 30°C were Enterobacter amnigenus, Providencia rettgeri, Serratia marcescens, Chryseomonas luteola, Aeromonas hydrophila, Proteus vulgaris, and Morganella morganii. The bacteria associated with shrimp that spoiled at 6°C (refrigerated conditions) were Chryseobacterium indologenes, Psychrobacter phenylpyruvicus, Aeromonas hydrophila, Pseudomonas mendocina, Moraxella lacunata, Pseudomonas fluorescens, Brevundimonas vesicularis, Chryseomonas luteola, Shewanella putrefaciens, and Providencia alcalifaciens . Inoculation of autoclaved fresh shrimp by individual microorganism species and subsequent sensory analysis of resultant spoiled shrimp indicated that Serratia marcescens and Chryseomonas luteola produced the most offensive odor at 30°C, while Pseudomonas fluorescens and Brevundimonas vesicularis produced foul odors at 6°C.; The key aroma-active components most responsible for spoiled shrimp odor (odor generated from processed shrimp inoculated with Serratia marcescens, Chryseomonas luteola, Pseudomonas fluorescens, and Brevundimonas vesicularis) were: trimethylamine, methanethiol, dimethyldisulfide, dimethyltrisulfide, butyric acid, and isovaleric acid.; Both trypsin and chymotrypsin significantly increased spoiled odor and odor intensity of shrimp that had been inoculated with Chryseomonas luteola. Trypsin increased unpleasantness by 44% (from 3.2 to 4.6 utilizing a 16 point scale) and odor intensity by 33% (from 14.1 to 18.7). Chymotrypsin exhibited similar results. There were no significant differences in the odors of shrimp treated with protease inhibitors and the control.; Ethyl butyrate (200 ppm), copper chlorophyllin (1%), and activated carbon (1%) significantly decreased spoiled shrimp odor intensity and/or odor perception. Activated carbon was most effective at lowering odor intensity (odor was reduced by 41%), and it was followed by copper chlorophyllin (26%) and kenaf (16%). Chitosan had no significant effect at lowering odor intensity. |
