Enhancement of antifungal and mycotoxin inhibitory activities of food-grade thyme oil nanoemulsions with natural emulsifiers

Thyme oil-in-water nanoemulsions stabilized by three different sources of natural emulsifiers (bovine serum albumin, quillaja saponins, and soy lysolecithin) were prepared as potential natural antifungal agents. The thyme oil nanoemulsion containing bovine serum albumin or quillaja saponins with mean particle diameters < 200 nm showed high physical stability during 28 days' storage. The antifungal and mycotoxin inhibitory activities of thyme oil nanoemulsions stabilized with three natural emulsifiers against Fusarium graminearum isolates were then investigated. Mycelial growth, spore germination, and mycotoxin production results indicated that the antifungal activity was mainly dominated by thyme oil rather than emulsifier to alter mycelial and spore cell membrane integrity. The mycotoxin inhibitory efficacy of thyme oil was enhanced considerably in nanoemulsion form as compared to bulk oil. Among the three natural emulsifiers, bovine serum albumin stabilized thyme oil nanoemulsion exhibited higher mycotoxin inhibitory activity due to a joint function of thyme oil and emulsifier.