Comparative study of kefir grains activation at room temperature to produce fermented milk

Abstract

Kefir grains are composed of a natural polysaccharides’ matrix with a mixed microflora, composed of yeast and bacteria. The product from the fermentation promoted by kefir grains in milk is fermented milk. Because it is a product disseminated in an artisanal way, there are gaps in the literature regarding the best way of storage, the subculture of pre-existing grains, and whether they manage to maintain their probiotic potential. With that in mind, the process of activation and non-activation of the grains after subculture when stored at room temperature was evaluated. The grains were separated into two groups, GKA (activated) and GKNA (non-activated), where their metabolic activities and the enumeration of lactic acid bacteria and yeasts were evaluated for 28 days. The activated grains showed advantages in relation to the greater mass increase (25% for the GKA and 15% for the GKNA), the pH and °Brix values were slightly lower than those presented by the GKNA samples. On the other hand, the GKNA sample showed higher values of microorganisms than the GKA sample. In conclusion, the activation of the grains was not advantageous because it is a laborious process and has no effect on the multiplication of microorganisms.