New approach to assess lactic acid bacteria compatibility during cheese-making.

Compatibility tests constitute an effective way to assess interactions among lactic acid bacteria: (a) it is necessary to avoid strain combinations displaying mutually inhibitory properties; (b) it may be beneficial to combine strains based on their ability to coexist. To study the compatibility of starter cultures and adjunct cultures mixed to control the production of mozzarella cheese, a tube containing 10 ml of UHT milk was inoculated in triplicate with three different strains in pure and mixed culture: the size of the inoculum in the mixed culture was at the 5% level for the starter strain and at the 10% level for the adjunct strain. The cultures were incubated at 37°C and after 90 and 180 minutes were analysed. The pH was determined; effectively, any interaction occurring in mixed cultures is reflected by acid production. The acidification of growth medium in batch culture is a good reflection of bacterial growth, which is why pH measurement is sometimes used to track growth [1]. In addition, the antioxidant activity was also measured by analysing the radical scavenging activity using a spectrophotometric decolourization assay (ABTS) [2]. The preliminary results and the relevant related literature are discussed considering, above all, the advantages for dairy industry and the consequences for starter and adjunct culture selection deriving from the possibility to simply predict interaction among lactic acid bacteria during cheese-making.[1] Kimoto-Nira H et al. Interaction between Lactococcus lactis and Lactococcus raffinolactis during growth in milk: development of a new starter culture. J. Dairy Sci. 95, 2176-2185, 2012.[2] Virtanen T et al. (2007) Development of antioxidant activity in milk whey during fermentation with lactic acid bacteria. J. Appl. Microbiol. 102, 106-115, 2007.