Research On The New Technology In Organic Color Protection Of Konjac

Amorphophallus konjac is an herb of the Araceae,Amorphophallus,widely distributed in tropical and sub-tropical woodlands.It is a half heliophobous plant,usually grown in the scattered light and weak light,fearing glaring light.A.konjac has high medicinal and dietary values.Modern researches showed that A.konjac has anti-aging,reduction of blood lipids,blood-glucose activity,regulation of the gastrointestinal tract,weight reduction,anti-tumor activity and immunity effects,etc.As great importance is attached to the free sale of A.konjac in the world as a qualified food by United Nations Food Sanitation Organization,soon after the European market will also be open.In recent years,plant area of A.konjac in our country is enlarged yearly,and the yields in production are high,reaching 2000-2700kg per mu(up to 5000 per mu),making A.konjac processing a growth industry.But in our country,A.konjac industry still has certain problems.For example,A.konjac,when peeling off or slicing up,would be browned by PPO.In order to whiten the products in the initial process,it is necessary to protect color with SO2.However,SO2 endangers human health and is harmful to environment.In this research,A.konjac in Han Zhong was studied to evaluate the effects of pH values and temperature on polyphenol oxidases activity.Several safe and nontoxic single and composite color fixatives were selected to processing A.konjac before baking,taking into account the method of vapor inactivation and microwave treatment,and the best process conditions of the coupling experiment of organic color protection and microwave enzyme inactivation were found out,in order to get sulfur-free powder of A.konjac.The main results are as follows:(1)The influences of different temperatures and pH values on PPO of A.konjac were evaluated.The results were as follows:the optimum temperature of the polyphenol oxidase of A.konjac is about 35℃.The activity of A.konjac is decreased by 95.3%after incubation for 30 min above 98℃.The optimum pH value of the PPO is 5.5,nearly devitalized below 3 or above 8.(2)After adopting four single and combined organic color fixatives,such as,L-cysteine,phytic acid,citric acid,ascorbic acid,in orthogonal experiment,the results were as follows:When L-cysteine is 0.02%concentration,citric acid is 0.2%concentration,phytic acid is 0.2%concentration and ascorbic acid is 0.15%concentration,it can reach the best effect and do no harm on the KGM of A.konjac.(3)After orthogonal experiment,for the best conditions of microwave enzyme inactivation is that:The power is 700W,thickness of A.konjac is 1cm,time is 1.5min,yet loss of KGM would be bigger in microwave enzyme inactivation.(4)Box-Benhnken design method was employed to obtain quadratic polynomial regression equation forecasting model for the coupling experiment of organic color protection and microwave enzyme inactivation.The results were as follows:The thickness of A.konjac is 1cm,the time of combined organic color fixatives is 3min,and the time of microwave enzyme inactivation is 0.5min.This study find out a new technology in organic color protection of A.konjac,which is safe and non-toxic and can effectively prevent the browning of A.konjac.It would be of great significance for guiding the production and processing of A.konjac.