Production of naturally flavoured and carbonated beverages using Williopsis saturnus yeast and cold fermentation process

This study was carried out to develop a new functional fermented beverage that combines both the functional composition of grape (Tarsus beyazi) juice and metabolic products of the yeast Williopsis saturnus. For this reason, two trials were conducted. First, the effect of different inoculation ratios and low fermentation temperatures at different times was examined. In naturally flavoured beverages, there was generally a decrease in total phenolic substance, antioxidant activity and total flavonoid amount with increasing fermentation time and inoculation ratio. The panellists chose b-15d (1 × 106 cells/mL W. saturnus yeast addition, 15 days fermentation) and then c-15d (1 × 107 cells/mL W. saturnus yeast addition, 15 days fermentation) the most out of different beverages produced. Fermentation performed with yeasts inoculated at the rate of 1 × 106 and 1 × 107 cells/mL for 15 days was selected for the second trials based on both general and sensory analyses. For this reason, these beverages, which were most preferred by the panellists, were re-manufactured and naturally flavoured carbonated beverages were produced by adding CO2 with the post-mix method. Brix, sucrose, glucose and fructose values were determined in lower amounts in natural flavoured carbonated beverages compared to grape juice, which is given importance by consumers. As in naturally flavoured beverages, carbonated beverages also decreased in total phenolic substance, antioxidant activity and total flavonoid amount with increasing fermentation time. In addition, the c-15d natural flavoured carbonated beverage (1 × 107 cells/mL W. saturnus yeast addition, 15 days fermentation) was more favoured by the panellists than the commercially purchased carbonated beverage. The results reported here are considered to be a good starting point for the development of new naturally flavoured and/or carbonated fermented beverages from the under-consumed grape.