Determination of some properties of fermented almond beverage produced using yoghurt starter culture

The aim of this study is to produce an almond-based fermented beverage using a yogurt starter culture and to investigate the effects of production conditions on selected quality attributes of the product. For this purpose, blanched raw almonds were blended with water at a ratio of 1:6 (w/w), ground, filtered, and subsequently fermented. In the production of the almond-based fermented beverage, two different pasteurization temperatures (70 °C/60 s and 85 °C/60 s) and two different incubation termination pH values (pH 4.40 and 4.60) were applied. The chemical, physical, microbiological, bioactive, and sensory properties of the produced almond-based fermented beverage samples were evaluated during 21 days of storage at 4 °C. The results showed that samples pasteurized at 85 °C exhibited higher total solids, fat, and protein contents, as well as higher titratable acidity values, whereas ash content and pH values were higher in samples pasteurized at 70 °C. No pronounced effect of incubation termination pH or storage period on chemical properties was observed. Throughout the storage period, samples pasteurized at 85 °C showed higher viscosity and L* values, along with lower serum separation and b* values. The incubation termination pH had no significant effect on physical properties. Regarding microbiological characteristics, pasteurization temperature and storage time were found to be influential, with the highest viable microorganism counts detected in samples pasteurized at 70 °C. Bioactive compounds were affected by pasteurization temperature, whereas incubation termination pH had no effect. Total phenolic content and FRAP values were higher in samples pasteurized at 85 °C, while DPPH radical scavenging activity was higher in samples pasteurized at 70 °C. According to sensory evaluation results, the almond-based fermented beverage samples were generally accepted by the panelists, receiving mean scores between 6 and 8 on a 9-point hedonic scale. However, sensory scores decreased below 6 on the 21st day of storage. In conclusion, pasteurization of the raw material at 85 °C and storage of the product at 4 °C for up to 14 days were determined to be more suitable for the production of almond-based fermented beverages in terms of quality attributes.