Stability of tuna oil and tuna oil/peppermint oil blend microencapsulated using whey protein isolate in combination with carboxymethyl cellulose or pullulan

Abstract

Tuna oil is one of the richest sources of docosahexaenoic acid and is thus considered to offer beneficial health effects to humans. However, its susceptibility to oxidative degradation is an obstacle to its more widespread use in the food industry. The aim of this study was to evaluate the potential impact of peppermint (Mentha piperita) oil on the physicochemical characteristics and oxidative stability of tuna oil inside microcapsules formed using whey protein isolate (WPI) as emulsifier and carboxymethyl cellulose (CMC) or pullulan as stabilizers. The emulsions were characterized in terms of size distribution, zeta-potential, viscosity, surface tension and confocal laser scanning microscopy. Microcapsules obtained by spray drying were analyzed to determine microencapsulation efficiency, powder water activity, color, bulk density, flowability (Carr's index and Hausner ratio) and oxidative stability (peroxide value and headspace propanal) and were examined by scanning electron microscopy. All formulations yielded spherical microcapsules with a smooth surface except that some agglomeration was observed for the CMC formulation. Microencapsulation efficiency was above 90% for all microcapsules. Size distributions of the microcapsules were bimodal and became greater after storage. All microcapsules, especially tuna oil microcapsules with CMC or pullulan, became more yellow after storage. Mentha piperita oil was found to improve the oxidative stability of microencapsulated tuna oil, regardless of the presence of CMC or pullulan, thus suggesting its usefulness in functional food applications.