Nutritional, Bioactive and Quality Attributes of Almond-Based Fermented Beverage (Ayran-Type): Effects of Pasteurisation, Fermentation pH and Storage

Abstract The effects of pasteurisation temperature (70 and 85 °C) and fermentation end-point pH (4.4 and 4.6) on the physicochemical, microbiological, bioactive, and sensory properties of an almond-based fermented ayran-type beverage were evaluated during 21 days of refrigerated storage. Pasteurisation temperature was the main factor affecting product quality. Beverages pasteurised at 85 °C exhibited significantly higher dry matter, protein, and fat contents, higher viscosity, and markedly lower serum separation, than those pasteurised at 70 °C (p < 0.05), whereas 70 °C better preserved total phenolic content, CUPRAC, and FRAP values. Fermentation end-point pH had generally limited effects, with significant differences observed only for viscosity, serum separation (%) and FRAP values. During refrigerated storage, starter culture viability gradually declined, although Streptococcus thermophilus remained above 7 log CFU g-1. Concurrently, yeast populations increased and sensory quality progressively decreased. Overall, pasteurisation at 85 °C, particularly in combination with fermentation to pH 4.6, provided the most favourable balance between physical stability and sensory quality.