The impact of lactic acid bacteria and yeasts ratio on fermentation and taste of kvass

A. Pisponen* and H. Andreson

Estonian University of Life Sciences, Institute of Veterinary Medicine and Animal Sciences, Chair of Food Science and Technology, Kreutzwaldi 56/5, EE51014 Tartu, Estonia
*Correspondence: anna.pisponen@emu.ee

Abstract:

Kvass, a non-alcoholic beverage derived from rye malt or special rye bread through natural fermentation, traditionally involves yeast in the production process. However, the introduction of various lactic acid bacteria (LAB) accelerates fermentation and imparts a distinctive taste and aroma to the kvass. This research aimed to optimize the ratios of LAB to baker’s yeast in kvass to enhance its fermentation, sensory qualities, and physicochemical properties, thereby improving its acidic flavour and overall acceptability. Baker’s yeast and three commercial LAB strains were used for fermenting the kvass wort made of dried rye bread. The experimental design focused on four distinct inoculation ratios: 100% LAB, 50% LAB:50% yeast, 80% LAB:20% yeast, and 100% yeast. Key parameters such as pH, dry matter content, and titratable acidity were monitored over 12, 14, and 16 hours of fermentation, with a detailed sensory analysis conducted on the 80:20 LAB to yeast ratio kvass samples that were fermented for 14 hours and then cooled. It was found that varying the ratios of LAB and yeast significantly affected the fermentation process. Extended fermentation times, particularly with higher LAB ratios, led to more pronounced acidity and sensory characteristics. Optimal microbial balances, notably the 80% LAB to 20% yeast ratio, enhanced kvass’s flavour profile and physicochemical properties, suggesting a tailored approach to fermentation can improve kvass’s quality and consumer acceptance. These variations, alongside significant strain- and species-related differences, highlight the importance of microbial balance in enhancing kvass’s acidic flavour and overall acceptability.

Key words:

lactic acid bacteria, non-alcoholic beverage, Saccharomyces cerevisiae, sour kvass

Effect of simultaneous inoculation of commercial yeast starter cultures on Kombucha fermentation

M. Abel and H. Andreson*

Abstract:

Kombucha – a spontaneously fermented tea beverage, produced by SCOBY (a symbiont of bacteria and yeasts), has become popular in recent years. Its functional properties and features for industrial production and treatment remain largely unknown, however. Our aim of using additional yeast cultures during the primary fermentation was to modify and ultimately improve the sensory properties of the kombucha beverage. During five fermentation experiments the total viable count (TVC) of microbes was determined both in Kombucha and SCOBY samples. The first four fermentation experiments were conducted to stabilize the growth of SCOBYs that were initially of different origin. The last (5^th) fermentation contained the simultaneous inoculation of three different active S. cerevisiae cultures into the sweetened black tea together with the SCOBY and was followed by a sensory analysis. Two samples remained as control samples without additional yeast starter culture. The yeast starter cultures affected the microbial counts of Kombucha, but the effect on the microbial count of SCOBY was not statistically significant (p >0.05). The Kombucha containing wine yeast culture had the lowest sensory quality, while Kombucha containing brewer’s yeast had the most pleasant flavour and aroma. In conclusion, the simultaneous fermentation with commercial yeast cultures had a minor effect on the microbial counts in SCOBY when compared to the fermentation time, but all added cultures clearly modified the taste and aroma properties of the Kombucha drinks.

Key words: