Study of the Chemical and Microbiological Quality of Fresh and Cooked Dried White Shrimps (Penaeus notialis) Sold on the Dakar Market

Abstract

In Senegal, shrimp is a highly consumed fishery product, often sold through informal channels that escape health controls. Sodium metabisulfite (SO₂) is used as a preservative there, although its uncontrolled use poses health risks. This study assesses the hygienic and sanitary quality of fresh and dried-cooked shrimp sold in two markets in Dakar (Central Fish Market and Castor Market), compared to a control point (Food Technology Institute), through socio-economic surveys and laboratory analyses. Twenty vendors and ninety consumers were interviewed to determine the practices regarding the use of metabisulfite and perceptions about food safety. Surveys conducted with fishmongers reveal a non-standardized and untracked use of sodium metabisulfite, applied empirically without controlled dosage, in an informal context where 100% of the fishmongers are aware of its existence but only 40% claim to use it. At the same time, 64% of consumers are unaware of the existence of this additive in shrimp, although 60% express total trust in their quality, illustrating a concerning discrepancy between treatment practices and risk perception, justifying urgent awareness and regulatory actions. Six samples were analyzed according to ISO and national standards to assess SO₂ levels, total volatile basic nitrogen (TVB-N), and microbiological contamination. The results reveal concerning chemical contamination: the dried cooked shrimp have SO₂ levels significantly higher than the standard (up to 1165.98 ppm compared to a limit of 270 ppm), while fresh shrimp from the Central Market slightly exceed the limit (154.69 ppm against 150 ppm). Microbiologically, only one moderate case of E. coli contamination was detected. The TVB-N values indicate satisfactory freshness. Studies reveal a craft-like use of metabisulfite, without precise dosing, and low consumer awareness of the risks associated with additives. Despite an overall acceptable microbiological quality, the excess of sulfites poses a serious health risk. These results call for a strengthening of the regulatory framework, better control of the additives used, and targeted awareness campaigns to improve the health safety of fishery products sold in Senegal's informal markets.