Alheira is a traditional Portuguese fermented sausage, produced without the aid of any starter culture. The objective of this study was to isolate lactic acid bacteria (LAB) naturally present in alheiras, and screen their potential for use as functional starter. Forty alheiras from 8 regional producers were analysed. A total of 335 LAB were isolated from MRS and M17 media and confirmed. Antimicrobial activity against Staphylococcus aureus and Salmonella spp. at 37°C and 10°C was evaluated by spot-on-lawn assay. Sixty-three strains were pre-selected, and their lactic acid production, acidification capacity and proteolytic activity determined. The suitability of the strains was assessed by adjusting two separate Principal Component Analyses (PCA) on MRS and M17 data.
Results showed acidification potential as the most determinant feature for strain differentiation across both media, followed by antimicrobial activity; while lactic acid production (LAC) and proteolytic activity (PAct) were the least contributing variables. For MRS strains, PC1 (38.9%) was positively correlated with the acidification capability of strains. PC2 (20.1%) positively correlated with LAC and negatively correlated with inhibition of both pathogens at 10°C and PAct, implying higher antimicrobial potential. Likewise, for M17 strains, PC1 (43.1%) and PC2 (16.7%) characterised higher acidification and greater antimicrobial potential, respectively.
The results differentiated 3 clusters of MRS strains, one with higher acidification capacity, related to greater S. aureus inhibition at 37°C; a second cluster with better overall antimicrobial activity and linked to higher proteolytic activity; and a third cluster of strains with more rapid production of lactic acid. One standalone MRS strain presented both greater acidification and antimicrobial potential. From M17 isolates, only two strains presented the highest acidification ability and pathogenic inhibition.
These results highlighted several strains with great potential for use as starter cultures in “Alheira”, which could confer protection against foodborne pathogens. In-situ essays are ongoing.