Use of ice teas formulated with black teas prepared with different infusion methods and grape juice in the production of water kefir beverages

Abstract

In this research, ice teas formulated with black teas prepared with cold and hot infusion methods and grape juice were subjected to fermentation with water kefir grains. The fermentation process lasted 48 h at 25 °C, followed by a 14-day storage period at 4 °C. As a result of fermentation with water kefir grains, a decrease in pH and total soluble solid content of ice teas and an increase in titratable acidity were detected. At the end of fermentation, the CO2 amount was determined to be 1.86 g/100 mL in teas prepared with a cold infusion and 2.23 g/100 mL in teas prepared with a hot infusion. Antioxidant activity and total phenolic content of ice teas prepared with the hot infusion method gave higher values. The duration of storage led to a decrease in the antioxidant activity and total phenolic content for both formulations. While the glucose, fructose, and sucrose values of teas prepared with the cold infusion method were 4.109%, 4.804%, and 2.312% at the end of fermentation, these values were found to be 4.649%, 5.528%, and 1.273% in the teas prepared with the hot infusion method. The analysis of the phenolic components showed that the main phenolic components were gallic acid, quercetin, epicatechin, and rosmarinic acid. It was found that the number of Lactobacillus spp. was 7.55 to 8.14, the number of Lactococcus spp. was 6.80 to 7.36, the total number of mesophilic and aerobic bacteria was 7.57 to 8.27, and the yeast count was 5.22 to 5.90 in ice teas made with different infusion methods and while they were stored. As a result of sensory analysis with produced water kefir beverages, panelists showed a significant preference for the hot infusion formulation. As a result, the produced ice tea formulations could be used as a fermentation medium by the microorganisms in water kefir grains, and ice teas with functional properties were produced.