Research On Browning And The Change Of Main Active Substance Content During Lycium Barbarum Juice Making

Lycium Barbarum in ningxia is the most distinctive local specialty. It has a long cultivation history, large body, bright color and good quality. To research the process of Lycium Barbarum juice browning and the change of the main active substance content can provide gist for maintaining the good color, flavor and taste of Lycium Barbarum juice in the process of making juice. The research content has the following several aspects:1, The enzymatic browning in the process of making Lycium Barbarum juice. The polyphenol oxidase (PPO) of Lycium Barbarum is studied on the enzymatic properties. The results show that, PPO activity is affected by pH and temperature significantly. The optimal pH value is4.5, while acid condition is helpful for maintaining the highly active of PPO. The optimal temperature for PPO of Lycium Barbarum is36℃.Due to the great effect of pH and temperature on PPO activity, we can adjust pH and ues the high temperature to passivate enzyme activity to reduce the occurrence of browning. Short time heatting treatment can inhibit the PPO activity of Lycium Barbarum significantly. Inhibiting PPO activity time at75℃,85℃and95℃effectively needs for5min,2min andl min, respectively. Handling for5min at75℃the enzyme activity basically inactivates, and reduce the heat process of non-Enzymaticbrowning and the loss of nutrients. Citric acid, ascorbic acid and sodium bisulfite can effectively restrain the PPO activity of Lycium Barbarum.2, The non-enzymaticbrowning in the process of making Lycium Barbarum juice, Lycium Barbarum juice at60℃,70℃heating treatment temperature BD change accords with zero-order reaction kinetics model; BD change under80℃,90℃,100℃pseudo-first-order reaction kinetics model. Lycium Barbarum juice ascorbic acid content in the heat treatment process change pseudo-first-order reaction kinetics model, sugar content changes have no obvious regularity, total phenol content changes in the uncertain. Lycium Barbarum juice at60℃,70℃heat treatment temperature almost do not produce5-hydroxymethylfurfural(5-HMF), under80℃,90℃,90℃generated results5-HMF pseudo-first-order reaction kinetics model. Lycium Barbarum juice Browning reaction in the initial stage in the process of heat treatment can be caused by polyphenol polymerization, then the browning reaction by maillard reaction and ascorbic acid degradation of common decision.3, The change of main active substance content in the process of making Lycium Barbarum juice. Including LBP, carotenoids and flavonoids. No obvious law as a whole. Carotenoids in nature stability around70℃. Flavonoids content cannot be determined, LBP content has no obvious change rule. In C Lycium Barbarum hot working process, we should properly control the temperature of the hot working and conditions, and inhibit the occurrence of browning, and decrease the loss of Lycium Barbarum active substances as much as possible. It can be finished in a heat treatment process after adding the right amount of bioactive substances, and to ensure the nutritional value of products necessarily.