Investigation of Physicochemical Properties and Microstructure of Enriched Yogurt with Nanoemulsion Based on Sesame and Sweet Almond Oil

In This study the qualitative properties of fortified yogurt produced with a sweet almond and sesame oil nanoemulsion (0.25-0.5% Span 80 and Tween 80) and homogenization time(5 and 10 min) by ultrasounic waves was investigated. In order to homogenize the emulsion particles, ultrasonic waves were used and the effect of homogenization time, oil concentration and emulsifier concentration on The pH, acidity, rheological properties,Apparent viscosity and textural properties of the fortified yogurt were studied for 10 days of storage at 4 °C. Fitting rheological models, the Herschel Bulkly model was the best model to study the fluid behavior of our samples. The flow behavior index in all treatments at 25 °C was less than 1. All of them had non-Newtonian (pseudoplastic) behavior, which was confirmed by increasing the shear rate, viscosity was reduced and weak gel behavior in all samples was confirmed. The results showed pH was reduced by incorporating sweet almond and sesame oil nanoemulsion, while the acidity was increased. The yogurt sample amplified in the absence of emulsifier has smaller casein micelles and more voids, which increases the product's leaching. It makes it more fragile. Also, by increasing pH, due to the dominance of hydrophobic bonds over the electrostatic force of the sample, it has shorter protrusions and a smoother and softer surface, so yogurt fortified with sesame oil with a concentration of 2% has more roughness than yogurt fortified with sweet almond oil. Overall, sesame oil with 0.25% of the emulsifier and 10 min of ultrasound is suggested for the production of fortified yogurt.