CONICET | Buscador de Institutos y Recursos Humanos

Kefir is a fermented beverage produced from kefir starter, by means of the milkfermentation with kefir grains. These grains are a protein and polysaccharide matrix thatcontains Lactic Acid Bacteria (LAB), Acetic Acid Bacteria (BAA) and yeasts. This studyaimed to assess the protective activity of the lyophilization process on the activity ofkefir grains by comparing their microbiological composition, sensory characteristics andantimicrobial effect on fermented products obtained either from lyophilized and freshkefir grains. Acidification kinetics and microbial counts were performed on fermentedmilks obtained from fresh or freeze-dried grains. Inhibitory activity tests againstEscherichia coli and Salmonella enterica serovar Enteritidis were carried out with differentdilutions of cell free supernatants from fermented milks. On the other hand, similarityand acceptability tests were performed to compare the sensory characteristics offermented milks obtained from fresh and freeze-dried grains. The microbiologicalcomposition and acidification capability of the freeze-dried grains were stable until 6months of storage at 4°C. Moreover, the minimum inhibitory concentration of fresh andfreeze-dried grains was similar (20% v/v) for both pathogens. Additionally, the sensorypanel did not detect differences between milk fermented with fresh or freeze-dried kefirgrains; the kefir beverage obtained from the freeze-dried kefir grains fermentationshowed a wide sensory acceptance among the population surveyed. We consideredthat lyophilization followed by the storage conditions applied were suitable for thesurvival of the kefir micro biota, the sensory characteristics and the antimicrobialcapability of the fermented beverage after an adequate reactivation process of thegrains. In conclusion, the reactivation process risk management is an important stage toensure a suitable carriage and therefore maximize the kefir grains for large scale use.