Batchwise fermentation with Ca-alginate immobilized multistarter cells for kefir production

Abstract

Abstract In an attempt to replace kefir grains, experimental batchwise fermentations were carried out with cells of Lactobacillus kefir LB2, L. kefiranofaciens LK4, Lactococcus lactis subsp. lactis LS5, Enterococcus durans EG8, Saccharomyces unisporus SF2, S. italicus syn. cerevisiae SC1 immobilized separately in Ca-alginate. Using the different immobilized microorganisms and various amounts of beads containing some microorganisms under standard conditions (constant gel: UHT skim milk ratio of 1:5, fermentation for 10 h at 28°C), the production of cultured milk was standardized with respect to biomass type and concentration, as well as for values of lactic acid, CO 2 , ethanol, diacetyl and acetoin. The new cultured milk obtained using a well-defined immobilized Multistarter activity was then evaluated during 28 repeated batches and the composition compared to traditional kefir. During each batch trial, the activity of the immobilized cells was concomitant with a continuous inoculation of UHT skim milk with the cells released from the gel structure. This process guaranteed a useful supply of free-living cells for the beverage as well as control of the quality and quantity of the metabolites produced by a selected combination of immobilized microorganisms.