Molecular bacterial characterization and free amino acids composition in Ivorian traditional fermented fish produced by two methods

The aim of this study was to show and compare the as yet unknown microbiological and biochemical composition of "adjuevan", an Ivorian traditional salted fermented fish that is produced by two main processing methods and consumed for its flavor. Method 1 uses the full fish and method 2 uses fish fillets. The pH was around 6 and the major organic acids were acetic and butyric acids in all adjuevan samples. The free amino acid profile varied according to the fermentation method, although the major free amino acids were valine, leucine, alanine, aspartic acid and glutamic acid, ranging in concentration from 101.7 to 745.4 mg/100 g, for both methods. Adjuevan produced using method 1 had the best composition of free amino acids. Lactic acid bacteria counts were between 6.0 × 104 and 2.6 × 105 cfu/g for method 1 and 5.9 × 103 and 2.1 × 104 cfu/g for method 2. Yeasts were detected in all samples. Microbial ecology analysis using PCR-denaturing gradient gel electrophoresis (DGGE) revealed the presence of more bacterial species than previously reported in fermented fish. Bacterial species varied according to fermentation method. Species such as Staphylococcus xylosus, S. lentus, S. saprophyticus, and Bacillus megaterium were found only in samples produced by method 1, while those of Staphylococcus piscifermentans, Bacillus mycoides, and Corynebacterium xerosis were found only in samples produced by method 2. Using specific primers, we detected several lactic acid bacteria (LAB), such as Lactobacillus, Pedicoccus, Lactcoccus, Streptococcus, and Leuconostoc species; the composition these bacteria in adjuevan samples varied according to the preparation method, but were not found to be dominant. We conclude that the molecular PCR-DGGE method can be used to differentiate fermentation methods by LAB profile analysis. A mixture of strains of S. xylosus, S. saprophyticus, S. cohnii, and S. piscifermentans were predominant, and LAB such as L. fermentum, L. lactis, L. pseudomesenteroides, L. raffinolactis, L. lactis subsp cremoris could be potentially beneficial for the specific flavor of each type of adjuevan to be selected as possible starter cultures for the development of a starter culture to improve adjuevan nutritional quality. (Résumé d'auteur)