Prominent Strains of Kefir Grains in the Formation of Volatile Compound Profile in Milk Medium; the Role of Lactobacillus kefiranofaciens subsp. kefiranofaciens, Lentilactobacillus kefiri and Lentilactobacillus parakefiri

Abstract

This study aims to reveal the effect of each of prominent lactic acid bacteria (LAB) in the microbiota of kefir grain on the chemical and biochemical properties of kefir and especially, the formation of the volatile aroma compound (VAC) profile. Thus, fermented samples were produced in milk using single strains of Lactobacilluskefiranofaciens (LKF), Lentilactobacillusparakefiri (LP) and Lentilactobacilluskefiri (LK), as well as two control samples using kefir grain (TK) and commercial kefir culture (CK). In the samples, the change in LAB amounts, physicochemical (pH, titration acidity), rheological and chemical properties (organic acid, sugar and volatile flavour compound content) were investigated. The results showed no significant difference between LAB numbers and physicochemical properties of the samples. The LK, the LP and the LKF strains, respectively, were observed more activity in acetic acid production, citrate and lactose consumption. In VAC profiles, the LKF strain was associated with hexanol, 2-octanol, and octanal and LK with ethyl octanoate, ethyl hexanoate, acetaldehyde and geraniol. The LP strain was characterized by aldehydes including heptanal, nonanal and decanal. Thus, the L. parakefiri strain was highlighted in terms of the desired aroma profile. These results provide a clearer understanding of possible metabolic pathways and functions of the prominent strains in the kefir grain.