Stabilization mechanism of oil and water emulsions by powdered buttermilk

This study investigates the use of buttermilk powder to stabilize oil-in-water emulsions, focusing on casein as the stabilizer, the formation of Pickering particles at the oil-water interface, and the impact of heating on the size of stabilizing proteins. Emulsions were prepared with buttermilk powder dispersions, both before and after heating, and with isolated micellar casein powder. Analyses included surface characteristics, particle size, zeta potential, three-phase contact angle, rheological behavior, and macro and microscopic evaluations. The results showed that casein significantly reduces interfacial tension, playing a crucial role in emulsion stability. No significant increase in particle size was observed after heating, and zeta potential values remained constant (−25.2 mV for buttermilk and −23.2 mV for heated buttermilk), suggesting that heating does not affect particle charge. Stability was confirmed by the creaming index (CI) after seven days, with emulsions containing 5% buttermilk showing a CI of 7.62%, while emulsions with 1.28% micellar casein showed a CI of 8.61%, with no significant differences. Rheological analysis revealed a pseudoplastic behavior and an increase in the elastic modulus (G′) with stabilizer concentration. Microscopic analysis highlighted the importance of stabilizer concentration and demonstrated that the Pickering stabilization process is essential for the metastability of emulsions.