The Study Of The Hypocholesterolemic Activity And Microencapsulation Of Wheyprotein Concentrate Hydrolysate

Whey protein concentrate hydrolysate(WPCH) was obtained by hydrolyzing whey protein concentrate(WPC)with protease. It was easily absorbed and had the physiological functions, such as antioxidant activity, antibacterial activity and antihypertensive activity. Study on the hypocholesterolemic activity of WPCH was scarce. One of aims of the paper was the preparation of WPCH with the hypocholesterolemic activity. But WPCH had serious bitterness, high hygroscopicity and poor bioavailability, which seriously affected the application of protein hydrolysates in food industry. The microcapsule technology had been widely used in the food industry. The application of microcapsule technology could solve problem of the limitation of food ingredients and additives application in food. Because it could control the flavor release and reduce the loss of volatile substances, moisture absorption and reaction in adverse environmental conditions. Microcapsule technology was expected to overcome the adverse properties of WPCH.WPCH was first prepared through biological enzyme technology, ultrafiltration and ion exchange chromatography. The microencapsulation of WPCH was prepared by spray drying method with the mixture of WPC and maltodextrin as wall material. Stability of WPCH and WPCH microcapsules in vitro were studied. The main research contents and results were as follows:Preparation of WPCH with the hypocholesterolemic activity: trypsin was chosen. The inhibition of cholesterol micellar solubility(ICMS) of WPCH was maximum after WPC was hydrolyzed for 8 h under the hydrolysis conditions: p H 8.0, temperature 45 ℃, enzyme/substrate ratio of 4%(E/S = 4%, w/w). The ICMS of WPCH was 17.26%. The ICMS of WPCH increased from 17.26% to 28.63% after ultrafiltration. The hypocholesterolemic activity of WPCH after desalting was 47.53% and salt emergence rate reached 93.14%. Therefore, WPCH with hypocholesterolemic activity could be obtained by hydrolyzing WPC with protease trypsin. Ultrafiltration and desalting treatment could be applied to preliminary separation and purification of WPCH to improve the hypocholesterolemic activity activity of WPCH.Preparation of microencapsulated WPCH:(1) the microencapsulation of WPCH was prepared by spray drying with WPC, heated WPC, mixture of WPC and maltdextrin, mixture of heated WPC and maltdextrin as wall material, respectively. The results showed that the encapsulation efficiency of WPCH with WPC and heated WPC were 41.4% and 45.81%, respectively. And the encapsulation efficiency of WPCH was up to 53.45% and 62.41% with mixture of WPC and maltdextrin, mixture of heated WPC and maltdextrin, respectively. The bitter of WPCH was evaluated by the flavor dilution analysis(TDA). The bitter extent of microencapsulated WPCH reduced to as 1/8 and 1/16 times as those with WPC, WPC and maltdextrin as wall material, respectively. The hygroscopicity of the sample reduced from 55.88 g 100g-1solid to 22 ~ 24 g 100g-1solid after the microencapsulation, while the Tg vaule of the sample increased from 64.17 ℃ to 73.63 ℃. Those indicated that the microencapsulation increased stability of samples. The microencapsulation of WPCH by spray drying did not alter the hypocholesterolemic activity.(2) The technological conditions of preparation of microencapsulated WPCH with mixture of heated WPC and maltdextrin as wall material were determined by single factor experiments and orthogonal experiments. The conditions of preparation of microencapsulated WPCH: 5:1(w/w) of wall and core materials, 1:1(w/w) of WPC/maltdextrin, 20% solids content, 180℃ the inlet air of spray drying. Encapsulation efficiency of the final product was 68.97%. The bitter significantly reduced to as 1/16 time as that of WPCH. The hygroscopicity of WPCH decreased from 55.88 100g-1solid to 19.63 g 100g-1solid. Tg value increased from 64.17 ℃ to 76.25 ℃. The stability of product increased.The results of stability in vitro showed: the hypocholesterolemic activity of WPCH decreased by 9% after the simulated gastrointestinal conditions. Microencapsulation had significantly protective effect on the hypocholesterolemic activity of WPCH.Conclusion: WPCH with the hypocholesterolemic activity was successfully prepared by hydrolyzing WPC with protease. The microencapsulation of WPCH with mixture of heated WPC and maltodextrin as the wall material by spray drying was obtained and weakened the bitter taste of WPCH, improved the stability and bioavailability.