| Phenolic compounds and antioxidant activity of Chinese bayberry fruit of differentvarieties, the inhibition effect of fruit extracts on the development of colon carcinogenesisin DMH induced rats, the effect of harvest maturity, storage temperature and high oxygentreatments on antioxidant activity and physiological changes, and the mechanisms involvedin fruit decay inhibition by high oxygen treatments on fruit decay were investigated. Theresults were as follows:The antioxidant activity was positively correlated with total anthoeyanin, total phenolicand total flavonoid content in Chinese bayberry fruit of different varieties, and theantioxidant activity was increased with the fruit color development. Phenolics compoundswere analyzed by HPLC-DAD-ESIMS and the major anthocyanin in bayberry fruit ofdifferent varieties was identified as cyanidin 3-hexose, which contributed to about 96% ofthe total pigment. Thephenolic compounds, were consisting of gallic acid, myricetinglycosides, quereetin glycosides and kaempferol glycosides, and the individual phenolicdiffered significantly in bayberry fruit among different varieties.Chinese bayberry fruit extracts inhibited the aberrant crypt foci (ACF) development inDMH induced rat colon mueosal, and the inhibition effect was enhanced with the increaseof bayberry fruit extract dose. Chinese bayberry fruit extract supplementation during theentire experimental period increased NOS activities and lowered the oxidant stress to liverand colon mucosal in DMH treated rats, thereby alleviating the toxicities of DMHmetabolic intermediates to the colon mucosal.Chinese bayberry fruit was harvested at at unripe, color turning, mature and full ripestages according to the fruit color, and stored at 20"C for 48 hours. Decreases of solublesugars and organic acids contents during storage period at each category indicate the qualitydeterioration of Chinese bayberry fruit after harvest. Chinese bayberry fruit reddened withanthoeyanin accumulation and PAL activity increase during storage, and a significantlypositive linear relationship was observed between the increase of PAL activity and theamount of anthocyanin accumulated. Total antocyanin, total phenolic contents and DPPHradical scavenging activity increased with advancing maturity, and the antioxidant activity of Chinese bayberry fruit enhanced with the increase of anthocyanin and phenolic contentsduring storage. There was a development in fruit color in unriped fruit after harvest, but theflavor and anti0xidant qualities did not reach to the levels of fully ripe fruit.Low temperature storage extended the storage life to 14 days at 1℃compared to the20℃of 60 hours. Fruit senescence developed quickly with the significantly increase ofrelative electrical conductivity and decay index, and the decrease of TSS, soluble sugarsand organic acids contents. Low temperature storage inhibited the respiratory rate andethylene production, maintained higher levels of membrane integrity and antioxidantenzyme activities, delayed the senescence process and reduced the textural and flavorqualities deterioration, thereby inhibited the decay incidence of Chinese bayberry. Highertemperature storage accelerated the increase of total anthocyanin, total phenolic content andDPPH radical scavenging activity during the initial storage period and the decrease of theseduring the remainder of the experiment. Refrigerated storage (at 1℃) inhibited the decreaseof antioxidants contents, and maintaine higher antioxidant activity in Chinese bayberryfruit.Quality parameters of total titratable acidity, total soluble solids, reducing sugar and pHvalue were only slightly affected by different superatmospheric O2 levels. While, treatmentswith 60％-100％O2 significantly inhibited fruit respiratory and decay incidence, and therewas a decrease in decay and respiration with an increase in oxygen concentration. The100％O2 treatment was the most effective in controlling fruit decay and maintaining thehighest vitamin C content. These results suggest that high oxygen atmosphere may providea potential alternative for postharvest decay control on Chinese bayberry fruit.Treatments with 80％and 100％O2 significantly inhibited vitamin C loss, maintainedlower levels of respiratory rate, ethylene production and MDA accumulation, inhibited thedecrease of SOD, CAT, APX and POD activities, delayed the senescence development andinhibited fruit decay incidence during storage. High oxygen treatments promoted theincrease of total anthocyanin, total phenolic contents and DPPH radical scavenging activityduring the initial storage period, and maintaine higher antioxidant activity during the wholestorage period, thereby enhanced the antioxidant activity of Chinese bayberry fruit.Exposure of Chinese bayberry to pure oxygen significantly prevented fruit decay. At theend of the storage period, the decay index of fruits exposed to pure oxygen was only 17％while that of control fruits reached 54％. Pure oxygen caused a significant increase inchitinase andβ-1,3-glucanase activities which reached a peak on the 6th day of storage. PAL and POD activities as well as total phenolic content increased more quickly and stayedat significantly higher levels in fruits exposed to pure oxygen during storage than thecontrol fruits. These results suggest, that the inhibition of postharvest fruit decay by highoxygen was related to the induction of defensive enzyme activities. The induced diseaseresistance may be involved in the mechanisms by which high oxygen treatment inhibitedfruit decay in Chinese bayberry.
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