Studies On The Decolorization Of Zein And Research In Application Of Film Forming

Zein , also called corn gliadin, is the main store protein of corn gluten meal. Due to its water resisting property, oxygen barrier and the easiness in the fabrication of large films, it is widely used in food, papermaking, printing, textile and medical and health and so on, especially in fruit and vegetable packaging. The present studies of home and broad focus on the techniques of zein extraction. The decolourization is one difficulty of the present studies, for the colour of zein restricts its wide use in industrial field. Besides, edible films made from zein are safe and environmental-friendly. Its slow release and preservation are also hotspots of studies. Therefore, the present study investigates the techniques of extracting and decolouring zein and releasing slowly and preserving the edible films. The results of the research are as follows:1．Regarding extraction rate of zein as the goal, choosing enthanol as solvent to extract zein and analyzing the best technical conditions. The result showed that the effects of main factors on zein extration were extracting temperature> the ratio of material and liquid > extracting time.Getting the best technical parameters of enthanol extracted zein: extracting time is 1．5 hour, the ratio of material and liquid 1:15, extracting temperature 50℃, and the highest extracting rate 48．65%.2．With the absorbance of yellow pigment from zein that has decolored as index, using activated carbon to decolouring zein and analyzing it's best technical conditions. The result showed that the effects of main factors on ein decolorization were ethanol content> the ratio of solid and liquid > pH value > decolouring time. Getting the best technical parameter of decolouring zein: the ratio of solid and liquid is 1．5: 100, the decolouring time 2．5 hours, the ethanol content 90%, and the pH value of liquid 7．0．The minimum absorbance of zein is 0．460 under the above condition. The effects of activated charcoal decolorization technology is obvious,can take off most of the yellow pigment.3．Useing zein as delayed-release skeleton material of nisin,After testing nisin activity released from complex film produced from zein and nisin, the following results are obtained: the thickness of activity that nisin releases in diluted hydrochloric acid increases with the increase of temperature. At the same temperature, the activity that nisin releases in diluted hydrochloric acid increases and then decreases with time changing.At 50℃, 36 hour, the max of activity that nisin releases in diluted hydrochloric acid is 390IU/mL. The zein film may control the nisin activity in 200～400 IU/mL in 15～50℃and 2～120h, may effectively prolong the action time of nisin.It can be used for film to delay release nisin.4．Based on the results of the weight loss ratio and deformation of cucumbers, effects of the ratio of material and liquid, the dosage of oleic acid, pH value and the dosage of glycerol factors on t the weight loss ratio and deformation of cucumbers were primarily investigated with one-factor-at-a-time technique method. Four factors, the ratio of material and liquid, the dosage of oleic acid, pH value and the dosage of glycerol, significantly improving the weight loss ratio and deformation of cucumbers, were screened for further investigation. By means of a three level Box-Behnken factorial design combining with response surface methodology (RSM), a mathematical model was developed to show the significant effect of each factor and their interactions on the weight loss ratio and deformation of cucumbers, and the optimum media composition for the weight loss ratio and deformation of cucumbers was : the ratio of material and liquid is 1．5:100g/mL, the dosage of oleic acid is 1g, pH is 8．5, and the dosage of glycerol is 3mL..Under above conditions, the lowest weight loss ratio of cucumbers was achieved at the level 6．89%, the lowest deformation of cucumbers was achieved at the level 2．30mm. The weight loss ratio and deformation decreased obviously, the weight loss ratio of cucumbers after coating can be reduce 48．45 %,the deformation of cucumbers after coating can be reduce 47．72%.The zein film has distinct preservativ effect.