Researchers: Dr. Vincent Yeung, Cal Poly SLO and Dr. Haotian Zheng, North Carolina State University

• Natural dairy ingredients derived from whey proteins can be used to replace synthetic emulsifiers in foods and beverages. These newly developed emulsifiers can assist with delivery of water-insoluble compounds (i.e., fat-soluble compounds) while boosting the total protein content of food.

• At present, the functionality of whey protein particle stabilized emulsions as delivery systems is not well understood. This study provided experimental data that demonstrated the functionality of a whey protein-based Pickering/Mickering emulsion in regulating lipid digestion dynamics and cellular delivery efficacy for curcumin, a water-insoluble compound with anti-inflammatory properties that comes from turmeric.

• Whey protein derived emulsions showed great potential for influencing lipid digestion, cellular uptake of curcumin, and end-product heat stability. This discovery shows promise for future innovations and applications focused on the delivery of water insoluble nutrients/bioactives/pharmaceuticals in a variety of formulas and beverages.

Oil-in-water Pickering/Mickering emulsions are different from conventional emulsions because they are stabilized by soft, solid particles. These emulsions have become a hot topic for the food and pharmaceutical industries because of their potential functions in regulating lipid digestion in the gastrointestinal tract and their carrying capacity for water-insoluble nutrients or pharmaceuticals. The objective of this study was to provide experimental data on the functionality of whey protein-based Pickering/Mickering emulsions. In this study, researchers manufactured three different whey protein aggregates and characterized their emulsion properties, measured their fat digestion kinetics, and investigated how each emulsion improved the bioavailability of curcumin, a water-insoluble compound with anti-inflammatory properties that comes from turmeric.

Three differently structured whey protein aggregates were manufactured for use as Pickering emulsifiers: fractal aggregates (FA), microgel particles (WPM), and spherical aggregates (SA). Non-heat treated emulsion samples were coded as WPI-E and FA-E, while heat treated samples are WPI-HE and FA-HE. Of these, FA particles had the smallest mean particle size, indicative of a relatively acceptable phase stability when presented in a dispersion system. To understand the stability of particle stabilized emulsion systems before and after heat treatment, the researchers prepared four emulsions samples using FA dispersion and whey protein isolate (WPI) solution.

Prior to heat treatment, WPI and FA stabilized emulsions showed no significant differences in lipid digestion dynamics as indicated by their free fatty acid release rate. Heat treatment did increase the fat digestion rates for both WPI and FA emulsions, but the lipolysis rate for FA-HE was lower than WPI-HE for the first half of the digestion period. The higher lipid digestion degree for FA-HE did not result in high cellular uptake of curcumin. Instead, the slow lipid digestion rate and relatively low degree of lipid digestion found in FA-E resulted in a relatively high bioaccessibility of encapsulated curcumin. The FA-E emulsion digesta samples were the only samples that had a micelle cubic structure. The presence of micelle cubic structures of FA-E could explain their relatively high cellular uptake of curcumin despite the relatively low degree of lipid digestion. This type of structure has an advantage in oral and transdermal drug delivery.

The results of this research contribute significant value to the food industry regarding the design of new formulas with improved heat stability and delivery of water-insoluble compounds. Experimental data from this study demonstrated the functionality of whey protein particle stabilized emulsions as delivery systems of water-insoluble compounds. Although the non-heat-treated FA-emulsion showed relatively slow lipid digestion, the sample resulted in relatively higher cellular uptake of curcumin as compared with the other emulsions that were tested. The phenomenon could be attributed to the formation of a unique structure (“micellar cubic”) of assemblies of digestive lipid products. Future research should focus on how to improve the absolute phase stability of FA emulsions, as they show great potential for future applications regarding innovative formulas and beverages with superior heat stability.