ศูนย์นวัตกรรมเทคโนโลยีหลังการเก็บเกี่ยว

The bacteriology of shrimp during frozen process

Aran Hanpongkittikun

Thesis (M.Sc. (Microbiology)), Department of Biology, Kasetsart University, 1975. 97 p.

1975

บทคัดย่อ

A bacteriological examination of the shrimp industry was conducted to investigate the condition associated with the production of frozen shrimp. Sample were collected from raw material , after beheading, after grading, before freezing, after freezing and during cold storage. Water andice used in the plant were also examined. Total viable counts and most probable number of coliform and the presence Escherichia coli, as well as Vibrioparahaemolyticus, were determined. In addition, the bacteria isolated from some samples during handling and processing were classified.

The results of this studies showed that tap water and ice could be the source of bacterial contamination to the shrimp. When chlorinated water was used, no bacteria were detected. However, when it was used to wash shrimp more than three times, the bacterial numbers were increased significantly. Plant ice contained smaller number of bacteria than market ice.

Bacterialnumbersofwhole shrimp first arrivalat the plant were ranged from 10⁶ to 10⁸ organism per gram. Shrimp beheadedimmediately after arriving reduced bacterial loadabout 45 % . Subsequent handing and processing were usually reduced bacterial load. However , insanitarypracticesduring processing increased the total bacterial numbers and the most probable numbers of shrimp were declinedslowly . After storage of 70 days at , -18⁰C, frozen shrimp contained 5.00x10⁵ to 1.00x10⁶ bacteria per gram.

At 370 C, incubation temperature bacterial flora of prefreezing shrimp were Micrococcus, Staphylococcus, Acinetobacter, Moraxella, Bacillus and coryneforms, after freezing

Micrococcus was found in large amout. At 20⁰CMoraxella, Acinetobacter, Micrococcus and coryneforms, as well as Flavobacterium – Cytophage were found throughout the process.The bacterial flora of frozenshrimp were similar to those of after freezing at both incubation temperature.

Vibrio parahaemolyticus was absent from shrimp during processing and frozen storage throughout the study. Coliforms and E.coli counts of shrimp were not correlated with each other. At raw material colifroms were found inshrimp more than 1100 colonies per gram. After beheading and washing , their count was decreased but before , the colifrom were again found in shrimp more than 1100 colinies per gram. After freezing colifroms were still found but in the lesser amount. However, the E.colicount was not greater than the standard requirement for frozen shrimp.