Profile of Aroma-related Volatile Compounds Isolated from Probiotic Dry-fermented Sausages Produced with Free or Immobilized L. Casei using SPME GC/MS Analysis

Dry fermented sausages are typical Mediterranean meat-products, the acceptability of which is strongly influenced by their quality. Probiotic lactic acid bacteria (LAB) play an important role in meat fermentation, as they induce flavour and texture changes, together with a preservative effect, resulting in an increase of the product's shelf life, while they may provide specific health benefits. To deliver the beneficial effects, probiotics need to contain an adequate amount of live bacteria (at least 106 cfu/g) at the time of consumption, able to survive the acidic conditions of the upper GI tract and proliferate in the intestine, a requirement that is not always fulfilled. Since it is well established that cell immobilization enhances the viability of cultures, the aim of the present study was to assess the volatile compounds in probiotic dry-fermented sausages produced with free or immobilized L. casei ATCC 393 on wheat. Of note, microbiological and molecular analysis confirmed that the levels of the adjunct strain in the new products after 66 days of ripening were above the minimum concentration for conferring the probiotic effect. SPME GC/MS analysis of volatiles suggested an improved profile of aroma-related compounds in sausages containing the immobilized cells. In total, 124 compounds were detected and the most important volatile by-products identified were esters, organic acids, alcohols, and carbonyl compounds. Principal Component Analysis of the semi-quantitative data revealed that the nature of the starter culture affected significantly the volatile composition. Finally, the overall high quality of the novel probiotic products was ascertained by the preliminary sensory test and an indication of increased shelf-life was evident, in contrast to sausages containing no starter culture. Our study demonstrated the application and efficacy of cell immobilization for the production of high quality novel probiotic products in meat industry.