Research On Performance And Application Of Antibacterial Composite Protein Films

Degradable protein films receive great attention in recent years, because consumers, food processing and producers prefer fresher and minimally processed products. Protein films or coatings have been investigated, because they are able to retard moisture, oxygen, aromas, and solute transports. And they can maintain food quality and be able to extend the shelf life of food. Therefore, the new degradable protein films which can replace plastic packaging materials gradually became the food packaging industry development direction.1、Water adsorption characteristics,including adsorption kinetics and isothermal water adsorption curve of WPI-Na Cas composite protein films were studied at 5, 25 and 40℃ in this experiment.The results showed that relative humidity(RH) significantly affect the time when moisture of WPI-Na Cas composite protein films reaches balance.The lower RH,the shorter the moisture balance time,per contra,the longer.The isothermal water adsorption data are mathematically fitted to Peleg model.2、Antimicrobial effect of protein films incorporating garlic oil(GO), potassium sorbate(PS) and nisin(N) at various concentrations were discussed. This activity was tested against food pathogenic bacteria namely Escherichia coli(E.coli) and Staphylococcus aureus(S.aureus).Mechanical and physical properties were characterized. In the range of antimicrobial agents concentration studied, tensile strength(TS) and elongation at break(E) of functional protein films were changed by incorporating GO,PS and N. And the WVP value of functional protein films decreased as antimicrobial agents added. GO incorporated into protein films had no effect on E.coli, but incorporation of GO at 300μl had antimicrobial activity against S.aureus. Protein films incorporated with PS showed antimicrobial activity against S.aureus, but there was no effect on E.coli. Incorporation of N at the lowest level of 25,000 IU had antimicrobial activity against both E.coli and S.aureus.3、The protein film-forming materials contained 5% whey protein isolate(WPI), 2% sodium caseinate(Na Cas) and 50% glycerol,which was the optimal formula obtained by uniform design method of previous work. The antimicrobial activity and packaging performance of WPI-Na Cas degradable protein films were discussed by addition of nano-Ti O2 at different concentrations(0,0.05,0.10,0.15,0.20g?(200ml)-1) in film-forming solution.The results showed that nano-Ti O2 and protein films showed a certain degree of compatibility.Addition of nano-Ti O2 could improve tensile strength and elongation at break of the protein films and decrease WVP values of the films,but decrease light transmittance,increase haze of the protein films. The degradable protein films suited for using below150℃.And,nano-Ti O2 incorporated into protein films had antimicrobial activity against both E.coli and S.aureus.4、In order to extend the shelf life of beef, effects of the quality of beef by antimicrobial protein coating combined with modified atmosphere packaging were discussed in this paper. The aerobic plate count, p H value, total volatile basis nitrogen(TVB-N) value, drip loss,a* value, thiobarbituric acid(TBA) value and the percentage of high iron metmyoglobin(met Mb)% during storage were determined. The results showed that fresh beef which coated by 50 mg Nisin-antimicrobial protein films for 5min in MAP(45%O2/30%CO2/25%N2) could be preserved over 20 days at 4±1℃, and various kinds of beef quality indexes could satisfied the national standards of the first grade fresh meat.