Contamination sources of coliforms in two different types of frozen ready-to-eat shrimps

The sources of coliform contamination were studied in two types of processed ready-to-eat (RTE) shrimp products: half-slitted cooked without head-on shrimp for topping on rice as sushi product and cooked peeled with head-on shrimp.The objective of this study was to determine the processing and environmental factors which contributed to the coliform contamination of these two product types. The samples from each step of the processing lines (5476 samples), finished products (1331 samples) and environment (3624 samples) were collected during January–December, 2006. The samples were then analyzed for presence of coliforms and the results were further analyzed using statistical methods. The results of samples from processing lines showed that cooked shrimps for sushi product were frequently contaminated during slitting step (15.05%) because of the improper design of the slitting equipment. 3.85% of the environmental swabs of slitting equipment were contaminated. In addition, rowing (7.23%), sizing (6.93%) and peeling (6.27%) also contributed to coliforms contamination in the product. In case of cooked peeled with head-on shrimp, the rowing step (8.43%) appeared to be the major contributor of contamination, whereas spraying with cooled water also played a considerably significant part as seen from the environmental swab results which showed 14.06% presence of coliforms at the spraying nozzles. In addition the result of workers’ gloves swab also revealed 7.20% of contamination. Using the Monte Carlo Simulation, the correlation of coliform prevalence of finished products, products from processing steps and environmental swab were obtained. The results of both products demonstrated that coliform prevalence of the total samples collected from processing steps and coliform prevalence from environmental swabs correlated with the coliform prevalence in finished products. Identifying these sources helped the plant manager to improve several procedures (such as personal hygiene, cleaning and temperature control including staff supervision) to minimize the coliform contamination in the final products.