| Ginkgo, which widely distributed in China, has been consumed as not only a nice food, but also an herbal medication. The yield of ginkgo in China is around 90 percent of the total yield in world, presents the place of number one. Most of ginkgo is only sold as dried fruits, not fully used at present. Developing some new products from ginkgo could take advantage of ginkgo resource and promotes both social and economic benefits. Ginkgo cloudy juice was one of the main products made from ginkgo seeds. However, it is very difficult to make the juice stable. Therefore, study of processing technology and stable mechanism of ginkgo cloudy juice has the deep significant both in theory and reality.This paper studied in the method of processing ginkgo cloudy juice by multiple enzymes, and the effect of different sterilized methods for ginkgo cloudy juice and their cloud stability, color stability and flavor.The conditions of gelatinization and processing of ginkgo soup were studied, the gelatinization temperature determined by DSC was 81.904℃. Then the research of the relationship between gelatinization temperature and time and particle distribution for quality of ginkgo cloudy juice was carried out, results showed that the gelatinization temperature and time were 90℃and 10 min, respectively. Homogeneous ginkgo soup was benefited for enzymatic hydrolysis.The influences of different enzymes for quality of ginkgo cloudy juice were investigated. The combination of amylase and proteinase had a desirable effect on the quality of ginkgo cloudy juice. An appropriate enzymatic formulation containing both mild temperaturesα- amylase and Alcalase proteinase could increase the juice yield and suspension stability, and improve quality of ginkgo cloudy juice.The optimal parameters of enzymatic reaction for ginkgo cloudy juice was determined. The single experiment and RSM experiment were designed to optimize hydrolysis conditions of middle temperatureα- amylase and Alcalase proteinase. The optimal processing conditions were obtained as follows: the ratio of raw and water was 1:5, initial pH was 7.0, reaction temperature was 60℃, amylase usage was 7.39 U /g pulp, Alcalase usage was 6.43 U/g pulp and hydrolysis time was 73 min. Components analysis indicated that ginkgo cloudy juice retained most of the nutritional components in fresh ginkgo kernel.Effects of inactivate microorganism in cloudy ginkgo juice by PEF treatment were investigated. The result showed that the higher the treatment time and electric fields strength, the greater microbial destruction. The optimal conditions were showed as follows: pulse duration of 3μs, electric field strength of 30kV/cm, treatment time of 520μs and the temperature of water bath of 15?C or 260μs at 40?C. PEF combination with mild thermal treatments enhanced microbial inactivation effectiveness. Heat, which is generated during the PEF processing, has a synergistic effect with PEF treatment.The shelf time of ginkgo cloudy juice by PEF treatment was studied. Survival numbers of microorganism was selected as evaluative index. The microbial shelf life of ginkgo juice by PEF treated at 520μs, 30kV/cm and 4?C was 18 days, 15 days at room temperature. The shelf life of ginkgo juice at 260μs, 30kV/cm and 4?C was 15 days, 6 days at room temperature. The results showed PEF processing could extend the shelf life of ginkgo cloudy juice.The sterilized method which suitable to ginkgo cloudy juice was determined. Ginkgo cloudy juice was treated by UHT at 140℃and kept for 5s, 10s and 15s, respectively. Ginkgo cloudy juice by UHT treatment reached commercially sterile requirements. The effects of 121℃treatment, UHT and PEF treatment for quality of ginkgo cloudy juice and sensory evaluation were investigated, and the best sterilized methods was decided as UHT treatment. The effects of enzymatic treatment on suspension stability of ginkgo cloudy juice were investigated. Starch molecules were treated byα- amylase to become dextrin and oligosaccharide, and protein treated by proteinase become peptides. Due to the effects of pliancy molecular chain of macromolecules dextrin or pectin, the steric repulsive effects were produced among suspended particles in ginkgo cloudy juice. Hydrolysis of protein by enzyme treatment and increasing of negative amino acid residues were not benefit to the attraction between protein and polysaccharide. And the increased zeta-potential of ginkgo cloudy juice also enhanced the exclusive effects of suspended particles. Therefore, the electrostatic repulsive effects were strengthened among suspended particles. Cloud stability of ginkgo cloudy juice mainly depended on the steric and electrostatic repulsive effects among suspended particles.Effects of ginkgo cloudy juice stability by sterilized methods were studied, and the effect of Zeta potential of suspended particle by sterilized methods was not significant. But sterilized methods could effects the particle size. The average particle size of suspended particle in ginkgo cloudy juice by PEF, UHT or 121℃treatment was 0.925μm, 1.333μm and 2.467μm, respectively. Comparison of cloud stability was PEF >UHT >121℃.Different hydrocolloids had different effects on cloud stability of ginkgo cloudy juice. Guar gum was the most thickening effect, and flaxseed gum possessed a little emulsification. By accelerated storage tests at 30, 35 and 40℃for ginkgo cloudy juice by UHT treatment, suspension stability was selected as evaluative index, the activation energies of the suspension stability was 70.44 kJ/mol. The shelf life of ginkgo cloudy juice was 388 days at 25℃.According to the results of the components of ginkgo cloudy juice and sedimentation, the mechanism of cloud stability of ginkgo cloudy juice was discussed. On one side, cloud stability of ginkgo cloudy juice mainly depended on the steric and electrostatic repulsive effects among suspended particles including macromolecular substances and suspended pulp substances. On the other side, during storage some macromolecular of dextrin occurred cross-linking with each other. Those macromolecular and some particles formed sedimentation due to the action of gravity. Macromolecular material, sugar-protein or protein-polyphenol compounds, fat-amylose complex and cell fragments were aggregated together and grown up to form more sediments.Different processing stage had different effects on non-enzymatic browning of ginkgo cloudy juice. Browning during enzymatic reaction was brought by Maillard reaction. Browning during high temperature sterilization may be caused by Maillard reaction and caramel reaction.Changes of color of ginkgo cloudy juice during storage were investigated. The result showed that the higher storage temperature or the longer storage time, the more seriously non-enzymatic browning. Maillard reaction was the most important cause resulting in non- enzymatic browning and non-enzymatic browning kinetics was preferred to zero order during ginkgo cloudy juice storage. Oxidation of polyphenols and Vitamin C were not main reason of browning.The volatile compounds of ginkgo cloudy juice were concentrated by SPME, separated and identified by GC-MS. 46 kinds of compounds were identified in volatile fraction of fresh ginkgo kernels, and the main components were terpene. 30, 49, 41, 57 and 53 kinds of compounds were identified in volatile fraction of gelatinized soup and those not sterilized, PEF treated, UHT treated and 121℃treated ginkgo cloudy juice. Volatile fraction of ginkgo cloudy juice by PEF, UHT and 121℃treatment compared with fresh ginkgo kernels retained 18, 18 and 12 kinds, respectively. The results indicated processing conditions had significant effect for volatile components, but ginkgo cloudy juice retained the main aroma components of fresh gingko kernels after processing. Some processing (such as enzymatic treatment) could improve flavor of ginkgo cloudy juice, however, another processing (such as heat treatment) made many of cooking aroma such as furfural, pyridine and furan.
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