Synthesis Fibrils Film Of Whey Protein Concentrate And Its Properties

Nanofibrils which are kinds of special self-assembled protein polymers, have caused extensive attention in recent years. However, most researches had been focused on the conditions and mechanism of fibrils formation at home and abroad, while few studies about functional properties and practical applications of fibrils have been reported. To broaden fibrils applications, whey protein concentrate(WPC) fibrils film were prepared from WPC nanofibrils in this paper. And the characteristics(solubility, oil machinery, electrical conductivity and resistance) of WPC fibril film were compared with that of WPC normal film. At the same time, to gain the optimal preparing conditions of conductive WPC fibril film, film-forming conditions(protein concentration, reheat time, p H and calcium ion strength) were changed. The results showed that WPC nanofibrils had the same film-forming abilities as the regular whey protein, and the characteristics of WPC fibril film are quite different from normal WPC film. Compared with the conventional WPC film, WPC fibril film possessed good electrical conductivity, oil resistance as well as resistance to mechanical tensile. And WPC fibril film still had well anti mechanical tensile properties, especially in the isoelectric point and after long time heating in high temperature. The unique performance of WPC fibril film plays an important role in development of the application of milk protein.The optimal preparation conditions of conductive WPC fibril film: based on the preliminary study, 3.0 wt % whey concentrated protein(WPC) were heated at pH2.0 and 90℃ for 10 h to obtain WPC fibrils raw material. Through comparing measurement indicators(solubility, mechanical properties and electrical conductivity) of WPC fibril film with that of regular WPC protein film, the optimum preparation conditions of conductive WPC fibril film were as follows: 6.0wt% WPC were heated at pH2.0 and 90℃ heating for 10 h, then calcium chloride(tendency for 100 mmol/L), gelatin(60wt% protein), glycerin(54wt% protein) were added under continuous stirring using a magnetic stirrer. Finally, the mixtures were heated at 90℃ for 30 min,after which they were cooled and poured onto glass plates.Solubility: Compared with the conventional WPC film, it was more easily to dissolve in water for WPC fibril film. However, the solubility of the WPC fibril film could be reduced significantly by improving the protein concentration, prolonging reheat time, and increasing calcium ion strength. The solubility of WPC fibril film was higher only 3.94% than that of conventional WPC film under 6wt% WPC concentration, p H2.0, reheat time for 10 h and 100mmol/L calcium ion strength.Mechanical properties: The mechanical properties of WPC fibril film are superior to that of conventional WPC film, and this was one of characteristics of conventional protein film did not possess. Compared with conventional WPC film, tensile strength(TS) and percent elongation at break(E) of WPC fibril film prepared near isoelectric point(p I) increase respectively by 64.53% and 43.82%;while the tensile strength and percent elongation at break of reheating WPC fibril film for 10 h at 90℃increase by 86.18% and 63.01%, respectively.Electro-conductibility: Electro-conductibility was the unique properties of WPC fibril film, which were closely related to the protein aggregation structure of nanafibrils, and electro-conductibility increased by 23.50% after fibril formation. The electro-conductibility of WPC fibril film could be improved by improving the protein concentration, prolonging reheat time, and increasing calcium ion strength. The results showed that the electro-conductibility increased 50.37% with the protein concentration increasing from 3% to 6%, electro-conductibility increased 24.09% with prolonging reheating time to 10 h and electro-conductibility increased 2.28 times with calcium ion strength reaching 100mmol/L.Oil-resisting: The Oil-resisting capacity of WPC fibril film was better than that of traditional WCP film. Compared with the Oil-resisting capacity of conventional WPC film, penetration rate of soybean oil for the WPC fibril film which was prepared at 6wt% protein concentration, p H2.0, 100mmol/L Calcium ion and heating 10 h was 49.43% of that of conventional WPC film. The unique properties of conductive WPC fibril film: Compared with conventional WPC film, electro-conductibility, mechanical properties, oil resistance of the conductive WPC fibril film were more excellent, but the solubility was similar. In particular, the solubility of WPC fibril film only higher 3.94% than conventional WPC film; and the tensile strength and percent elongation at break were respectively higher 78.09% and 62.83% than that of conventional WPC film, at the same time, electro-conductibility was 1.73 times that of the conventional film.