Proteolysis of muscle sarcoplasmic proteins by lactic acid bacteria isolated from anchovy. Effect of sodium chloride

BELFIORE CAROLINA; FADDA SILVINA; VIGNOLO GRACIELA

Tucumán Argentina

Simposio; III Simposio Internacional de Bacterias Lácticas. Segundo encuentro Red Bal Argentina.; 2009

CERELA-CONICET-MINCYT

Anchovy (Engraulis anchovy), a pelagic species is usually salt-ripened during a slow process that takes 6-9 months to be completed. Ripening involves a series of complex biochemical processes transforming the raw material in a much appreciated gastronomical product with a pleasant texture, aroma and flavor. It is know that the ripening of salted anchovy take place via enzymatic pathways, the importance attributed to tissular enzymes versus microbial enzymes being controversial. The aim of the present work was to evaluate the ability of three strains of lactic acid bacteria (LAB) isolated from anchovies to degrade fish proteins during growth in an anchovy soluble extract with or without addition of NaCl. The assays were carried out in a sterile experimental muscle system obtained from macerated fresh anchovy containing 0 and 10% NaCl and incubated at 22ºC. The culture medium was independently inoculated with Lactobacillus sakei SACB704, Lactobacillus curvatus SACB03a and Leuconostoc mesenteroides SACB07 isolated from anchovies and the protein degradation as well as the amino acids content were determined by SDS-PAGE and OPA assay, respectively. A non-inoculated control medium was also included. In absence of NaCl, LAB showed a significant growth 106  to 1010 CFU ml-1 after 7 days, producing a pH decrease from 6.5 to 3.7; while in presence of 10% NaCl LAB strains remained viable along the studied period, the pH varying in a lesser extent (5.9 to 5.0-4.5). When fish muscle degradation was assayed, the net content of free amino acids at 7 days was higher in the presence of LAB strains when compared with the non-inoculated control media, this indicating the contribution of bacterial peptidases. The protein patterns resulting from the action of LAB strains analyzed by SDS-PAGE showed that the major changes in fish soluble proteins occurred when L. curvatus SACB03a was inoculated in absence of salt. The disappearance and/or decrease in intensity of protein bands from 66 to 14 kDa was evidenced from 24 h. However when this strain grew in presence of NaCl no proteolytic changes were observed. In constrast, in such condition (10% NaCl), L. sakei SACB704 and Leuc. mesenteroides SACB07 produced relatively higher changes on the protein profile than L. curvatus SACB03a. Even when the presence of 10% NaCl showed to affect protein degradation, these results indicate that both, endogenous enzymes and LAB contribute to fish protein degradation. This work constitutes an initial approach to elucidate fish protein degradation by LAB strains isolated from salted anchovies which may contribute to the release of peptide and amino acids with an impact in the flavour of final product.