Problem of Fish Fermentation at High Temperature for “Guedj” Production in Senegal and Potential by Bacteriocinogenic Lactic Acid Bacteria Strains Used as Starter Cultures on a Local Cereal-based Liquid Matrix to Control Spoilage Bacteria

Introduction: This study describes the conditions of fermentation in Senegal for production of fish guedj which is a popular condiment and animal protein source across the Sahel, and the capacity by two nisinogenic Lactococcus lactis subsp. lactis strains, used as starter cultures.

Purpose: To improve the control of spoilage bacteria.

Methods: Lactococcal strains have been qualitatively determined as suitable hurdle for use on fish within four bacteriocinogenic lactic acid bacteria, on the basis of their negative histidine and tyrosine decarboxylase activity. They growth well on a new-developed liquid matrix based on millet flour, a local cereal.

Results: Fish are transformed to guedj by spontaneous fermentation for 24 to 48h at ambient temperatures near 30°C followed by salting (with NaCl) and sun drying. Spontaneous fermentation of fish generally performed by its immersion in salted sea water led to the proliferation of enteric bacteria to 9 log CFU/g.

By immersion of two lean (Podamassys jubelini) and fat (Arius heudelottii) fish from artisanal production in the newly formulated substrate inoculated with 10^6-7 CFU/g of the pure starter cultures,  the pH was reduced and maintained below 4.5 for 48 h at 30°C sufficient to inhibit pathogenic and spoilage bacteria. When the fish starter culture fermentation is carried out in presence of a nisin sensitive pathogenic Listeria monocytogenes strain inoculated at 10⁵ CFU/g, the level of this indicator was reduced below 10² CFU/g while in control samples (fermented without LAB living culture addition), it reached 10⁸ CFU/g.

Significance: These results indicate that the new fish fermentation approach by treatment with the two nisin producers could enable improvement of guedj safety.