Soybean protein isolate(SPI) was used to investigate the formation of edible protein films through an enzymatic cross-linking method with a purified microbial transglutaminse(MTG) produced and purified from a new effective strain Streptomyces sp.WZFF.L-M1 preserved in my laboratory,followed by the addition of glycerol and suitable heating and drying treatments.Cheaper partially-purified skimmed soybean protein powder(SSP) and whey protein isolates(WPI) were used as the substitutes partially replacing the expensive SPI products,and purified β-lactoglobulin was taken as the positive control of WPI.The effects of the concentrations of the three substitutes and their relative ratios have been compared with SPI as a control,and the methodologies of MTG treatment were examined.Attempts have also been approached for the films formation-enhancing substances such as glycerol.As the results,the three alternatives could also form high efficient edible films in the optimal operation conditions experimented.Those films made with SPI alternatives,thin around 50 μm,had the microscopic homogenous network structures,without any holes by naked eye.The tests for the properties of these films showed that they had high water-keeping capacity and strong elasticity,that the ultimate tensile sterength(TS)and the elongation at break(Eb) had been remarkably increased(TS>5 MPa,Eb>50%,respectively),and that the prevention rates against the permeability of water vapor and oxygen in air were also upgraded more than 85% and 70%,respectively.
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