Research On Browning Regularity And Browning Inhibition Technology Of Muskmelon During Explosion Puffing Drying Process

Cucumis melon L.belongs to the genus of cucumis and the family of cucurbitaceae,and it is a kind of thick skin melon,and its fruit is edible.Because of its mature fruit peel with reticular cracks on the surface,so it is called muskmelon,too.Because of its unique beauty of appearance and aromatic taste and excellent flavor,it is loved by consumers.Its fruit can be the product part,and its pedicel has medicinal value.Cucumis melon L.contains catechin,epicatechin,and other phenolic substances,and reducing sugars.During the processing steps,enzymatic browning and non-enzymatic Browning occurs easily,and seriously affect the quality of product,so the development of industrialization of cucumis melon L.industry is limited.This experiment studied the browning regularity of cucumis melon L.crisps during processing of explosion puffing drying,and optimized the technical parameters of explosion puffing drying,and providing the theoretical basis for the processing of cucumis melon L.Contents of this study includes two parts:the browning regularity of cucumis melon L.during the processing of explosion puffing drying,and the optimizing of technical parameters of explosion puffing drying for inhibiting browning of crisps.The second part includes several small parts:choosing the compound color fixatives,optimizing the pre-drying temperature,vacuum drying temperature and time.The first part mainly studied the browning regularity of melon crisps during the process of explosion puffing drying.The results showed that the non-enzymatic browning in melon during processing is the Maillard reaction.The processing steps could affect the Maillard reaction include color protection process,pre-dry process and puffing drying process.And the key factors include the type and concentration of color fixatives,pre-drying time,vacuum drying temperature and time,moisture content,pH value,and so on.Content of catechin and epicatechin are higher than other phenols content in cucumis melon L..So they are main phenolic compounds which participate in enzymatic browning reaction.During the process of explosion puffing drying,water loss of melon crisps mainly focuses on pre-drying and puffing steps.And the water loss rate of puffing process is higher than the pre-drying process.Non-enzymatic Browning mainly focuses on puffing process,and enzymatic browning occurs during the pre-drying process.Reducing the pH value could inhibit the activity of polyphenol oxidase,so that it could reducing enzymatic browning and non-enzymatic Browning in the meantime.The change of pH value in the Color protection process significantly influence the activity of polyphenol oxidase(PPO)and peroxidase(POD),and the decreasing in enzyme activity can reduce the enzymatic browning.For high-temperature,POD is more sensitive than PPO.And enzymatic browning mainly exists in the pre-drying process.POD and PPO activity in the softening and puffing process has been lost yet.Heating temperature and duration will significantly affect the rate of Maillard reaction.And with the increasing of moisture reduction and pH,non-enzymatic Browning will further enhance.So that we can know the non-enzymatic browning mainly exists in the later period of pre-drying and the entire puffing process.Decreasing of soluble protein content during puffing process mainly due to the occurring of non-enzymatic browning,and the heating temperature and duration would be significantly affect the rate of Maillard reaction.After the puffing process,content of 5-HMF accumulated the highest;in the color protection and softening processes,the accumulation of 5-HMF content is not significant.So,if we want to control the occurring of browning of melon crisps,we should try to avoid using the high-temperature process for a long time.The change of AE*in pre-drying and puffing processes is significant(p<0.05),and is not significant in the softening process.This showed that the technical parameters of pre-drying and puffing process is the key to control the browning of melon crisps.The second part filtering the compound color fixatives,and optimizing the technical parameters of explosion puffing drying.The results showed that:the compound color fixatives consisted of 0.6%sodium chloride,0.15%calcium chloride,0.1%L-Cys and 0.6%citric acid works better in the pre-drying process for inhibiting the browning.In the three factors of Pre-drying temperature,vacuum drying temperature and time,influence of vacuum drying temperature is the most,followed by the pre-drying temperature and vacuum drying time.The orthogonal experiment showed that the optimum level is:70? of pre-drying temperature,70? of vacuum drying temperature,150 min of vacuum drying time.