Preparation Of Corn Zein And Application Of Zein Films

Zein is a mixture of alcohol soluble proteins that constitute 50%～60% of total endospermprotein. Zein is easy to come into being films. It can be used in food, medicine, printing, dyeingand paper making industries. Using zein films for food preservation and packaging has become thefocus of intensive researchThe methods of ultrasonic decolorization for corn gluten meal (CGM) and low velocityelectric distilling extraction were studied in the tests. Using absolute alcohol as solvent, the bestdecolorise conditions are that the optimum temperature was 60℃, ultrasonic work time was 25 minand CGM-to-solvent ratio(W/V) was 1:8.The optimization distilling conditions were that theoptimum temperature was 50℃, extracting time was 3h, CGM-to-solvent ratio(W/V) was 1:8 andusing 75% aqueous ethanol (V/V) as extraction solution. The ingredients of the product wereanalyzed and protein components were identified using SDS-PAGE. Using the method of salt out toprecipitate zein. The concentration of sodium chloride was 0.3%. Scan electric microscope wasused to observe the difference of CGM before and after decolorization. Many cavities were seen onthe surface of CGM after decolorization. Ultrasonic can make the coloring matters on and in thesurface of CGM out. Zein granule prepared of this study was 10 to 100μm in size, round in shapeapproximately and has many hollows in the surface as grape.The antioxidative effects of corn zein films for pork fat were studied in this test. Stored fatswere iodometrically titrated to determine peroxide value (POV). It was found that zein films canrestrain fat oxidation well and the content of zein has direct ratio to the antioxidative effects. Groupwith zein films and group without it have visible significant difference (p＜0.01). But three groupswith zein films did not have visible difference. Zein films containing a-tocopherol have betterantioxidative effects. The films added 1mga-tocopherol to lg zein have better antioxidative effectsthan zein films without a-tocopherol. The two groups have visible difference (p＜0.05).The antimicrobial effects of corn zein films for cooling fresh beef were studied in this test.The total bacteria number of stored beef were determined. The films whose concentration of filmsolution was 1: 4(g/mL) could restrain bacterial growth in fresh beef well. Group with films andgroup without films have visible significant difference (p＜0.01). Eugenia caryophyllata thumbcould help to restrain bacterial growth. The films that added 0.3mL Eugenia caryophyllata thumb tolg zein have better antimicrobial effects than contrast group. The two groups have visibledifference (p＜0.05).The concentration of film solution was 1:6(g/mL). Adding 0.05g glycerin to lg zein asplasticizer to store oranges. Some values were determined during the oranges store period, such as ratio of weight losing, ratio of rot, titrationable acidity, contents of vitamin C and soluble solidsubstance. Ratio of weight losing of the group with zein films was 5.7% lower than contrast groupaveragely and ratio of rot was 14.2% lower, loss of vitamin C was 2%～5% higher. Titrationableacidity of group with films was higher and loss of soluble solid substance was fewer than the groupwithout films (contrast group).