Sensory improvement of dry-fermented sausages by the addition of cell-free extracts from Debaryomyces hansenii and Lactobacillus sakei.

The effects of the addition of a combined cell-free extract from Lactobacillus sakei and Debaryomyces hansenii (D+L) or just a D. hansenii cell-free extract (D) to the initial formulation of a dry-fermented sausage were evaluated. The differences found among batches in the main microbial populations, pH, moisture content and global proteolytic and lipolytic indexes (total free amino acids, non protein nitrogen, acidity and tiobarbituric acid index) were not significant. Only, the acidity value of batch D was significantly higher (p<0.05) than that of batch D+L. Thus, cell-free extract from D. hansenii accelerated the lipolysis. Moreover, there were some significant differences (p<0.05) in the amino acid profile and, especially, in the aroma profile. The combination D+L and D promoted the generation of volatile compounds derived from lipid oxidation and carbohydrate fermentation. In batch D, the production of volatile compounds derived from amino acid catabolism and microbial fermentation was also enhanced. The overall quality was improved by both treatments (D+L, D) and also the aroma by addition of the combination of extracts (D+L). It is concluded that the addition of cell-free extracts from D. hansenii and, particularly, D. hansenii plus L. sakei could be useful to improve the final quality of fermented sausages.

Hydrolysis of pork muscle sarcoplasmic proteins by Debaryomyces hansenii.

Strains of Debaryomyces hansenii originally isolated from sausages were screened for proteinase and aminopeptidase activity towards synthetic substrates. On the basis of these results, D. hansenii CT12487 was selected for further assays. The activities of the whole cells (WC), cell-free extracts (CFE) and a combination of both from the selected strain on pork muscle sarcoplasmic protein extracts were determined by protein, peptide and free amino acid analyses. There was a pronounced hydrolysis of protein bands of 110 kDa and 27-64 kDa regardless the incorporation of WC, CFE or a combination of both. The proteolytic activity also resulted in the generation of polar and non-polar peptides showing noticeable differences depending on the addition of WC or CFE. Whole cells generated greater amounts of free amino acids than the cell-free extracts.