Optimization of Ultrasound-Assisted Microwave Encapsulation of Peanut Oil in Protein-Polysaccharide Complex

Peanut oil (Arachis hypogaea L.) is a rich source of unsaturated fatty acids. Its consumption has been reported to have biological effects on human health. Unsaturated, especially polyunsaturated fatty acids (PUFA) found in peanut oil are highly susceptible to oxidation, leading to the formation of harmful compounds during processing and storage. The aim of this study is to prevent the oxidation of peanut oil PUFA by encapsulation in a protein-polysaccharide complex using microwave drying.

The combined effect of corn starch (CS) and whey protein isolate (WPI) was evaluated for ultrasound-assisted microwave encapsulation of peanut oil to prevent oxidative degradation. The effect of independent parameters, viz. CS:WPI mass ratio (1:1 to 5:1), lecithin mass fraction (0-5 %), ultrasonication time (0-10 min) and microwave power (150-750 W) on the encapsulation of peanut oil was evaluated using response surface methodology (RSM). The process responses, viz. viscosity and stability of the emulsion, encapsulation efficiency, peroxide value, antioxidant activity, free fatty acids (FFA), moisture, angle of repose and flowability (Hausner ratio (HR) and Carr's Index (CI)) were recorded and analysed to optimize the independent variables.

The viscosity of all emulsions prepared for encapsulation by ultrasonication ranged from 0.0069 to 0.0144 Pa·s and more than 90 % of prepared combinations were stable over 7 days. The observed encapsulation efficiency of peanut oil was 21.82-74.25 %. The encapsulation efficiency was significantly affected by the CS:WPI mass ratio and ultrasonication. The peroxide value, antioxidant activity and FFA ranged from 1.789 to 3.723 mg/kg oil, 19.81-72.62 % and 0.042-0.127 %, respectively. Physical properties such as moisture content, angle of repose, HR and CI were 1.94-8.70 %, 46.5-58.3°, 1.117-1.246 and 10.48-22.14 %, respectively. The physical properties were significantly affected by surface properties of the capsules. The higher efficiency (74.25 %) of peanut oil encapsulation was achieved under optimised conditions of CS:WPI mass ratio 1.25, 0.25 % lecithin, 9.99 min ultrasonication and 355.41 W microwave power.

The results of this work contribute to the fields of food science and technology by providing a practical approach to preserving the nutritional quality of peanut oil and improving its stability through encapsulation, thereby promoting its potential health benefits to consumers and applications in various industries such as dairy and bakery.