Formulation optimization and impact of environmental and storage conditions on physicochemical stability of pistachio milk

Abstract

Pistachio milk, as a non-dairy nutraceutical beverage, is a thermodynamically unstable colloidal system. So, this study aimed to optimize pistachio milk production in terms of pistachio slurry (20-40), emulsifier content (0.5-1), and ultrasonic power of 200-400 W as independent variables using response surface methodology based on particle size and polydispersity index (PDI) as responses. Moreover, the influence of environmental treatments (pH variation, freeze-thaw cycles, and different temperatures) and 28-day storage (at 4 and 20 degrees C) was evaluated on physicochemical properties of the optimum formula. The results showed an increment in pistachio slurry () had a positive relationship with particle size and its PDI, despite the emulsifier enhancement. The software, based on central composite design, selected the pistachio milk containing 28.5 pistachio slurry, 1 emulsifier produced by 200 w ultrasonic power as the best sample. It found that the acidic pH, continuous freeze-thaw cycles, and temperature increment decreased the particle charge and elevated the size and PDI of the sample leading to low colloidal stability. Furthermore, the storage data showed the colloidal and oxidative stability of the specimen reduced during the time, even though the samples stored at 4 degrees C were more stable.