Study on the Processing Technology of Chinese Olive Concentrated Juice
|School||Fujian Agriculture and Forestry University|
|Course||Of Food Science|
|Keywords||Chinese olive juice enzymolysis browning Rheological property vacuumconcentration freeze concentration antioxidant activity|
Canarium album L.(Chinese Chinese olive or fuguo), fruit of canarium plant (Buseraceae), is famous in tropical and subtropical area and also know as special agricultural product in Fujian province. Chinese olive cloudy juice with certain flesh content will keep the unique flavor and quality of Chinese olive as current leading product. Abundant fiber and pectin content in Chinese olive flesh, as macromolecular substance, will make low juice yield and be suspended in Chinese olive juice, with juice being divided into layers and precipitate its stability getting worse. The juice will be easily to brown in processing and have its appearance and flavor affected, even causing its commodity value lost. How to break the processing technology barrier will be the key to the development of this industry. Key technology in Chinese olive juice concentrate processing is studied in this paper with results as follows:1. Optimal single-enzymolysis parameter of cellulose, acid protease and pectinase is obtained through studying effort on juice yield and suspension stability under different enzyme concentration, enzymolysis temperature and time. The testing result indicates that adding enzyme mentioned above respectively into Chinese olive pulp will increase juice yield and improve suspension stability in varying degree, while product rate obviously risen to70%by pectinase within the test range. Using mixture enzymes(pectinase and cellulase) will have better enzymolysis effect compared with using single enzyme. Through the orthogonal, the condition to achieve optimal juice yield and suspension stability is determined as:cellulase concentration:11250U/Kg pulp, pectinase concentration:35U/Kg pulp, reaction at4545℃,60min and pH4.5.2. Browning type in different processing stage and key factor to affect browning was judged by detecting the change of browning degree and also content of polyphenol oxidase, polyphenol,vitamin c and5-HMF in blanching, pulping, enzymolysis and concentrating process in Chinese olive juice concentrate production. The testing result indicates that juice browning is mainly non-enzymatic in whole juice processing process with oxidant browning of polyphenol not dominating and consistent oxidant browning of vitamin C. And there is Maillard reaction in blanching, enzymolysis and concentrating process. The anti-enzymatic browning activity of inhibitors (citiric acid, vitamin c and L-cysteine) is studied by adding them in different proportions to juice, finding browning inhibitors of three kind will have non-enzymatic browning of Chinese olive juice inhibited, making red-green value(a) decreases in varying degree, while changing trend of yellow-blue value (b) shows certain correlation with browning degree in changing inhibitor adding amount. Better non-enzymatic browning inhibitive effect is obtained by composite inhibitors of0.6%citiric acid,0.02%vitamin C and0.005%L-cysteine.3. Rheological property of Chinese olive juice concentrate and its kinetic model on concentration is determined by studying relationship between juice viscosity and its temperature, concentration and shear rate in juice concentrating process. The results show that, Chinese olive juice concentrate, as non-Newtonian pseudo-plastic fluids, will have its viscosity decreases with increasing temperature, while the viscosity increases with its concentration adding up. The juice viscosity will gradually decrease with the increasing shear rate, while shear-thinning appears.The modelη=-5.6597·exp(29.2317/RT-0.1803·C+0.0031·C2) reflected the combined effect of temperature and concentration, on viscosity of Chinese olive juice concentrate, with applicable range of20-60℃, and35-60°Brix concentration.4. The optimal technical parameters for vacuum concentrating of Chinese olive juice is obtained after studying as follows:70℃, vacuum degree:-0.095MPa, terminal point60°Brix. Also the juice is freeze concentrated to obtain its strinking point as25°Brix. Sensory index, browning degree, suspension stability and main component (total acidity, total sugar, vitamin c and polyphenol content) of Chinese olive raw juice and juice made by reconstituting concentrate(through vacuum, freezing and air) is compared with the listed result:The quality of juice making by air concentration is inferior to that concentrated by vacuum; Vacuum concentrating will have better suspension stability compared with freeze concentrating, while its capability to keep juice flavor, color and main component comparably worse. Due to the higher production cost and lower efficiency of freeze concentration, using vacuum method is relatively suitable for Chinese olive juice concentrate producing. Scavenging capacity to DPPH radical, hydroxyl radical and antioxidant ability of juice in varying concentration level is also studied, the results shows that concentration lever won’t cause obvious effect on DDPH radical scavenging ability, while hydroxyl-scavenging and total antioxidant ability of juice changes in varying concentration level, which is related with the content changing of vitamin C and polyphenols in concentrating process.