| Abstract [eng] |
Considering the principles of sustainability, raspberry pomace was used during the research as a by-product of berry processing industry. In this study, ultrasound and bacteriocin-producing lactic acid bacteria (Lactobacillus reuteri 182 and Lactobacillus plantarum F1) were used to develop an unpasteurized fermented beverage. The technology allows preserving microorganisms beneficial to human health, such as lactic acid bacteria, and avoiding the use of chemical additives. A secondary product of berry processing, raspberry pomace, which has a high moisture content, can be used in the creation of a value-added product. Also, secondary plant products can be used as an alternative food source, thus considering the principles of sustainable development. Phytochemicals found in raspberry pomace can be used in the production of a functional unpasteurized beverage and as a means to ensure microbiological stability. During the research, a symbiotic culture of microorganisms Medusomyces gisevii was used in the fermentation process, consisting of bacteria and yeast, whose metabolic products determine the complex and consumer acceptable taste of the product. During the research, a metagenomic analysis of Medusomyces gisevii was performed, which identified 370 species of microorganisms and their functional properties. In order to increase the concentrations of phenolic compounds and anthocyanins in raspberry pomace, as well as the antioxidant activity, 37 kHz ultrasonic treatment of raspberry pomace was performed. After the use of different ultrasound intensities (40, 70, 100 and 120 %) and exposure durations (15, 30, 45 min), the optimal treatment parameters of raspberry pomace were selected – 70 % intensity and 45 min, and 120 % intensity and 30 min ultrasonic treatment. Ultrasonically treated raspberry pomace was used in the fermentation process with a culture of Medusomyces gisevii. In addition, lactic acid bacteria (Lactobacillus reuteri 182 and Lactobacillus plantarum F1) were used in effective concentrations, whose metabolic products ensure the microbiological stability and safety of the beverages for consumption. It was found that the ultrasonic pretreatment of raspberry pomace resulted in higher concentrations of phenolic compounds and anthocyanins in the samples of fermented beverages, and increased their antioxidant activity. In the samples with 70% intensity and raspberry pomace pretreated for 45 min, the concentration of phenolic compounds increased by 32,34 %, anthocyanins by 17,96 %, and antioxidant activity by 4,02 %. The concentration of phenolic compounds increased by 14,62 %, anthocyanins by 13,29 %, and antioxidant activity by 1,10 % in the samples with 120 % intensity and 30 min ultrasound pretreated raspberry pomace. Addition of raspberry pomace resulted in more microbiologically stable fermented beverage samples. The results of the study show that the by-product of the berry processing industry can be effectively used for the production of probiotic fermented beverages. |
