Study On The Encapsulation And Protection Of Vitamin E Based On Whey Protein Isolate Stabilized Emulsion System

In the recent years, ordinary food system cannot meet people’s needs with the continuously development of food industry and the attention to people’s health. Therefore, the development of functional food system incorporating bioactive components is necessary. However, many bioactive components have problems when applied in the food system owing to poor solubility, environmental sensitivity and low bioavailability. These factors extremely limit the development of functional food system with bioactive component. Thus, the key to solve such problems is to create a suitable edible carrier system to encapsulate and protect bioactive component from degradation so that they can be better applied in functional food system. Protein stabilized oil-in-water emulsions have been widely studied these years. They are proved to be effective carrier systems for hydrophobic bioactive compounds, to improve their solubility and stability in the aqueous solution. Becaue whey protein isolate is a food-grade protein with high nutritional value, emulsification and the ligand-binding property, it can be used to create edible carrier system and has broad application prospects in food.In this thesis, whey protein isolate(WPI) was chosen as emulsifier model to prepare various oil-in-water emulsion systems to encapsulate hydrophobic vitamin E and to reveal the characteristics of the emulsion systems used as a carrier of vitamin E. The data gathered here will help choose an emulsion systemwith better encapsulation efficiency and better protective effect for hydrophobic bioactive components like vitamin E.1. The oil-in-water emulsions were prepared by using whey protein isolate at various concentrations. Through the initial trials, the concentrations of whey protein isolate at 0.001%, 0.01%, 0.1% and 1% and storage up to 25 days were selected for further study. It was found that encapsulation efficiencyof vitamin E in the emulsion particles was dependent on WPI concentrations and was highest at 0.01% WPI and was lowest at 1% WPI. In general, the higher WPI concentration, the better was the protective effect against the decomposition of vitamin E. 1% WPI showed the best protective effect.2. The emulsions stabilized by WPI at 0.01%, which has best encapsulation efficiency but relative poor protective effect, were chose to study the influence of antioxidants on oxidation stability. Hydrophilic vitamin C and Amphiphilic resveratrol were chosen as model antioxidants. It was found that vitamin C at concentrations lower than 5 times that of WPI improved the stability of vitamin E encapsulated in WPI emulsions while vitamin C at higher concentrations accelerated the degradation of vitamin E and decreased the stability of the system. Addition of resveratrol enhanced the oxidation stability of vitamin E and the stability of the system.3. At the emulsifier concentration of 0.01%, the protective effect for vitamin E againt the degradation was investigated by using the emulsions stabilized by WPI and by Tween 80 or monoglyceride at various pH and temperature value. The results indicated that the emulsions stabilized by WPI showed the best protective effect both at 25°C and 45°C. The protective effects were in accordance with physical stability of the emulsions except the case of monoglyceride at various pH.4. The emulsions stabilized by WPI at 1%, which has best protective effect but relative poor encapsulation efficiency, were chose to enhance its encapsulation efficiency of vitamin E by addition of metal ions. Fe3+, Fe2+ and Ca2+ were chosen to study the influence of metal iron types and concentrations on the encapsulation and protection of vitamin E. The results showed that all of metal irons caused the aggregation of WPI emulsions, increased the content of WPI at the oil-water interface and the encapsulation efficiency of vitamin E in the oil phase. In general, the overal effects were more pronounced at the higher concentration of metal irons. However, all the samples were unstable when the concentrations of metal irons were 800 μM. High concentrations of Fe3+ accelerated the degradation of vitamin E, while the emulsions stabilized by WPI at 1% could effectively inhibit such phenomenon with iron added up to 200 μM. Fe2+ improved the oxidative stability of the emulsions, which increased as the Fe2+ concentration increased and was dependent on the time of storage. Ca2+ had no influence on the oxidative stability of 1% WPI emulsions.