Loading natural emulsions with nutraceuticals using the pH-driven method: formation & stability of curcumin-loaded soybean oil bodies

Previous studies have shown that the pH-driven method can be used to load curcumin into a variety of colloidal particles, including micelles, liposomes, lipid droplets, and oil bodies. This method is based on the increase in hydrophobicity and a corresponding decrease in water-solubility of curcumin when the pH changes from highly alkaline to acidic. In this study, we examined the physical and chemical stability of curcumin-loaded soybean oil bodies prepared using the pH-driven method. First, the impact of pH (from 6.5 to 8) on the stability of curcumin-loaded soymilk during storage was investigated at 4 degrees C for 36 days. At this low storage temperature, more than 85% of the alkaline-sensitive curcumin was retained at all three pH values, without any evidence of color fading. The impact of holding temperature (4, 20, 37, and 55 degrees C) on the physicochemical stability of the curcumin-loaded soymilks was then measured during storage at pH 7 for 14 days. At 4 and 20 degrees C, the emulsions remained physically stable, most of the curcumin (>90%) was retained, and there was no evidence of color fading. At the higher temperatures, however, the rate of curcumin degradation increased. For instance, around 30% and 70% of curcumin was lost when the soymilks were stored at 37 and 55 degrees C, respectively. On the other hand, the soymilks remained physically stable throughout this period. This study provides valuable information about the loading of curcumin into pre-existing plant-based milks and creamers, which may be useful for developing a new category of functional foods and beverages.