Shrimp quality and safety management along the supply chain in Benin

Abstract

This thesis focuses on quality and safety management of tropical shrimp (Penaeus spp.) using Benin (West Africa) as an example of a shrimp exporting country. The entire supply chain, from fishing areas (brackish waters) to shrimp processing plants, was investigated. The steps of the chain prior to shrimp processing at the freezer plants were critical for shrimp quality and safety because of prevailing temperature abuse and inappropriate hygienic conditions. Combining culture-dependent (plate counts) and culture independent (DGGE, clone libraries analysis) approaches, it was found that bacterial concentration in shrimps was higher than that of their surrounding water and sediment. Conversely, bacterial diversity was higher in water or sediment than in shrimps. At species level, distinct bacterial communities were associated with sediment, water or shrimp samples. Spoilage evaluation of shrimps showed that during storage at 0ºC, Pseudomonas spp. were dominant, whereas at 7ºC and 28ºC, H2S-producing bacteria were the dominant group of microorganisms. An empirical model predicting shrimp shelf-life as a function of constant storage temperature was developed. Isolates producing strong off-odor were identified by 16S rRNA sequencing as mainly lactic acid bacteria (LAB) and Enterobacteriaceae at 28ºC or 7ºC and Pseudomonas spp. and LAB (Carnobacterium maltaromaticum) at 0ºC. The fastest growing isolates namely, Pseudomonas psychrophila and C. maltaromaticum were selected for their spoilage activity and for modeling studies. P. psychrophila had a higher growth rate and a higher spoilage activity at 0 to 15ºC, while at 28ºC, C. maltaromaticum had a higher growth rate. Models predicting the growth of pseudomonads in shrimps as a function of temperature were constructed. These models were validated under dynamic storage temperatures simulating actual temperature fluctuation in the supply chain. Using different risk classification approaches, the main foodborne pathogen risks identified were Vibrio parahaemolyticus and Salmonella. The management of the risks posed by the main pathogens was addressed using different scenarios to meet the set food safety objectives. Based on quantitative and ecological studies, this thesis developed tools that can be used in decision-making regarding tropical shrimp quality and safety management.