Microbiological quality of frozen precooked and peeled shrimp from South-East Asia and from the North Sea.

The microbiological quality of frozen precooked and peeled shrimp is largely dependent upon the method of processing. The investigations were carried out in order to study the difference between the microbiological quality of shrimp from South-East Asia and from the North Sea and to determine whether both can meet draft FAO/WHO and ICMSF-specifications; 100 samples of frozen precooked and peeled shrimp from South-East Asia and 50 samples of shrimp from the North Sea were examined. In 45% of the shrimp samples from South-East Asia and in 78% of the samples of North Sea shrimp the number of aerobic mesophiles was over 10(6) per g. The number of Staph. aureus was higher in the samples of shrimp from South-East Asia than in those from the North Sea: 34% of the samples from South-East Asia had over 2 x 10(3) Staph. aureus per g., whereas only 6% of the samples of North Sea shrimp exceeded this number. Gram-positive mesophilic cocci were predominant in shrimp from South-East Asia. Gram-negative psychrophilic bacteria were predominant in North Sea shrimp. This difference in bacterial flora is caused by a difference in processing. The number of Enterobacteriaceae was usually low (less than 2 x 10(2) per g) in both kinds of shrimp. In three lots of South-East Asian shrimp Salmonella was detected. Vibrio parahaemolyticus was not found. On the basis of draft FAO/WHO endproduct specifications all lots of both South-East Asian and North Sea shrimp would have been rejected. On the basis of ICMSF specifications the rejection amounted to 90 and 80% of the lots, for the two types of shrimp respectively. Preservatives were not detected in shrimp from South-East Asia, whereas benzoic acid was present in all samples of North Sea shrimp. It was concluded that the ammonia content is a valuable objective quality index only in case of North Sea shrimp.