Abstract

Problems with the safety and shelf life of export hake have been raised by the Namibian fishing industry. This prompted an investigation into the factors that may have an impact on the microbiological quality and safety of processed hake. Samples were collected along the processing line; the general microbiological quality (mesophylic and psychrotrophic aerobic plate counts), total Vibrio species and common fish spoilage bacterial counts were performed. The results constantly showed relatively high counts for the psychrotrophic and spoilage bacteria, indicating that most of these bacteria already formed part of the incoming fish. Hake is headed and gutted on board of fishing vessels and delivered to the factory only after 7 – 8 days for final processing. It is likely that this practise of heading and gutting the hake may have a negative effect on microbiological quality of the final product. A sharp increase in the mesophilic and sucrose fermenting Vibrio species counts were observed after filleting. It has been suggested that this contamination could be due to biofilms present in the distribution system for the treated sea-water used during processing. Although, sea-water could be an alternative source of water for marine fish processing plants, the treatment and the quality of the water needs to be carefully managed.

Key words: Hake fish, aerobic plate counts, Vibrio species, mesophiles, psychrophiles, spoilage bacteria.

Abbreviation

Abbreviations: AA, Aeromonas agar; ABM-F, after filleting machine hake fillets washed with fresh water; ABM-S, after filleting machine hake fillets washed with sea-water; APW, alkaline peptone water pH 8.4; APHA, American Public HealthAssociation; BM, basal medium; CFC, cetrimide fusidin cephaloridin agar; EU,European Union; FP, hake fish finished products; H and G, headed and gutted hake fish; ICMSF, international commission on microbiological specifications for foods of the international association of microbiological societies; LFHF, laminated and folded hake fillets; PCA, plate count Agar; PW, peptone water; SWA, sea water agar; TVC, total viable counts; TCBS, thiosulphate citrate bile salts sucrose agar;VRBG, violet red bile glucose agar.