Development of fermented beverage based on pistachio (Pistacia vera) extract: Effect of functional compounds on kefir growth and microbial metabolism

Abstract

The increasing interest in plant-based, functional, and probiotic-rich foods has driven the development of alternative dairy-free fermented beverages. This study aimed to formulate a vegan fermented beverage using a water-soluble pistachio extract (WSVP) as a substrate for water kefir grains, evaluating the effects of selected functional ingredients on microbial growth, fermentation performance, and the production of bioactive compounds. A Plackett-Burman experimental design assessed the impact of a sucrose/cocoa honey blend, calcium chloride, inulin, xanthan gum, matcha, and raw and roasted pumpkin seed protein on eight key fermentation parameters. The sucrose/cocoa honey blend and pumpkin seed protein had a significantly positive effect on kefir grain growth and metabolite production. At the same time, matcha exerted inhibitory effects due to its high catechin content. The optimized formulation resulted in a 309 % increase in kefir grain biomass, a lactic acid production of 0.96 g/100 mL, an ethanol content of 1.60 g/100 mL, and a final pH of 4.47 after 17 h of fermentation. Metabolomic profiling via ¹H NMR identified 23 metabolites, including organic acids, amino acids, and sugars, with an increase in bioactive compounds and antioxidant capacity following fermentation. In vitro, simulated digestion confirmed the survival of lactic acid bacteria and yeasts, and the fermented beverage maintained a significant level of antioxidant activity throughout the digestive process. These findings demonstrate the viability of WSVP as a fermentation medium for producing innovative, nutritionally enriched, plant-based functional beverages, contributing to diversification within the vegan product market and offering sustainable, health-promoting alternatives to traditional dairy-based fermented products.