Research On Lycium Barbarum Browning Reaction In Hot Air Drying Processing

Lycium barbarum as "Affinal Drug and Diet" has a history of three thousand years.It not only is rich in a variety of nutrients which was needed by human body but also has a variety of biological active ingredients.Lycium barbarum is popular among consumers,because it has many health care function,such as antioxidation,antitumor,regulating immunity,antilipemic activity.Lycium barbarum is mainly consumed as dry fruit because of its high nutrients and water content which makes it hard to store and deliver.Our country is the main planting and processing production Lycium barbarum area.Nearly 90%fresh Lycium barbarum was processed into dried fruit each year.The drying characteristics,the rule of quality change and browning reaction of Lycium barbarum were studied during the different hot wind drying processes.The results of the study were as follows.1.Falling rate drying stages dominated and the internal moisture of Lycium barbarum diffusion controlled the whole process of dried during hot air drying.Under the four drying temperature in 50,55,60,and 65?,effective moisture diffusivity of Lycium barbarum was 0.76 × 10-10?1.98 × 10-10,and dry Activation energy was 61.36 kJ/mol.2.Great changes have taken place on Lycium barbarum color,that it transformed fresh red to dark red.Both color value and color saturation of Lycium barbarum appeared declined dramatically.While the value of chromatism increase significantly.Therefore,browning reaction took place in Lycium barbarum in the process of drying.3.At the beginning of drying,PPO activity was high.PPO activity reduced almost to zero along with drying.Enzymatic Browning reaction which was the main reaction type occurred in the early stage of the drying process.The reaction substrates with PPO was preliminary judged to be chlorogenic acid.4.According to the characteristics of non enzymatic browning,we confirmed maillard reaction happened in Lycium barbarum on hot air drying later period.The change of the color difference and 5-HMF were given to verify the reaction in 65,70,65?,RH:65%.The higher the temperature is,the more conducive to the Maillard react,under the condition of the certain humidity.5.The optimum technology of extraction of browning black substance was obtained by the single factor test and MRS experiment:the ethanol concentration of 31%(v:v),the ratio of material to water 1:20(m:v),temperature of extraction solvent 46?,extraction time 1.4 hours.By using this technology,the chromatic value of Lycium barbarum extract was 6.82,and the black substance yield was 46.40%.6.LB-? and LB-? that has the different apparent state were isolated from the black substance.Because of LB-? has more antioxidant capacity than LB-?:LB-? was LB-?3.21,2.96 and 1.17 times in the total reducing power,DPPH radical scavenging capacity and hydroxyl radical scavenging activity,so LB-I is worthy of further research.