Study On The Process Technique Of Whey Protein Based Films And Antimicrobia Properties Of The Composite Films

Food preservation is a hot topic in the research of food science and technology. For the development of bio-film with multifunctional of antimicrobial, healthy etc., the filming properties of six kinds of whey proteins were compared and suitable whey protein was selected as filming material in this study. Then, the effects of whey protein concentration, pH, time and temperature of denaturation on film properties were also studied and film process technique was optimized. Meanwhile, the antimicrobial properties of whey protein based film supplemented with clove essential oils and Nisin were studied. The results were summarized as below:Whey protein isolation (WPI) based film had the better mechanical properties with transparent appearance than whey protein concentrate (WPC) based films. WPC80-472 based film showed the best mechanical properties, least moisture penetrability among other WPC based films with pale yellow color, and was evaluated as suitable filming material.The WPC concentration, temperature, time and pH value of denaturation showed significant influence on the properties of WPC based film. With the single-factor test, the effects of WPC concentration (w/w), pH, temperature and time on properties of film were analyzed and thus the L9 (34) orthogonal experiment was designed. The results showed that: the film with optimal tensile strength (TS) was obtained from the WPC concentration of 12% (w/w) with denaturation temperature 80℃, time 10 min and pH 8; The film with optimal puncture strength (PS) was obtained from the WPC concentration of 12% with denaturation temperature 70℃, time 20 min and pH7; The film with optimal water vapor permeability (WVP) was obtained from the WPC concentration of 10% with denaturation temperature 80℃, time 20 min and pH9; The film with optimal water content (MC) was obtained from the WPC concentration of 12% with denaturation temperature 70℃, time 10 min and pH 7; The film with optimal solubility (So) was obtained from the WPC concentration of 12% with denaturation temperature 70℃, time 10 and pH 7. The films were then scored with weighted grade method from above properties (TS, PS, WVP, MC and So), the film with highest score was obtained from WPC concentration of 12%, denaturation temperature 80℃, time 15 min and pH 7.The results of antimicrobial test showed that: WPC based film with 200IU/ml Nisin had effective inhibition on the growth of Salmonella, Staphylococcus aureus, and Lactobacillus casei. However, the film with as high as of 200IU/ml Nisin showed no inhibition on the growth of Escherichia coli, Bacillus subtilis, yeast (Rhodotorula) and mold (Trichoderma spp., Aspergillus niger). The film with 0.125% clove essential oil (CEO) showed effective inhibition on the growth of Escherichia coli, Staphylococcus aureus, Salmonella, and Lactobacillus casei, however, Bacillus subtilis could be inhibited only when CEO concentration was above 0.25%, and yeast was inhibited when CEO concentration was above 1%. The better antimicrobial effect was observed when supplemented with both Nisin (500IU/ml) and CEO (1%).