Effects Of Near Freezing Point And Controlled Atmosphere On Preservation Of ’Whangkeumbae’ Pears

’Whangkeumbae’pear (Pyrus pyrifolia Nakai) was bred by Korea pomologists, which was introduced into China in the last decade and planted in many areas because of its productivity and quality. However, its fruit is perishable during storage, and how to prolong its preservation is an important question for its development. In this work, the fruits of12cultivars (including’Whangkeumbae’) were firstly used to determinate the freezing point temperature (FPT), and study the relationship between the FPT and fruit volume, fruit weight, fruit density and total soluble sugars (TSS) by grey correlation degree analysis and SPSS13.0software. Secondly,’Whangkeumbae’ fruits picked about145days after full blooming were used to investigate the effects of near freezing point temperature (-1.0～0.0℃) on preservation. Lastly, the effects of3.0%O2with different CO2proportion (0.0%,0.5%,1.0%and3.0%) treatment on fruit quality and shelf-life were studied. The main results were showed as follows.1. The results indicated that the pear FPT was quite different between cultivars, where the highest was-1.9℃of ’Hosui’, while the lowest were-4.3℃and-4.5℃of ’Qiubai’and ’Nanguo’, respectively. The FPT in other nine cultivars (including ’Whangkeumbae’) were from-2℃to-3℃. The pear fruit density was around1.000g/cm3. The analysis with the grey correlative degree analysis (GCDA) showed that TSS was the main impact factor on the FPT, and then the fruit density. The fruit volume and fruit weight were the low impact factors on the FPT of pears. According to the measurements of TSS, the regression analysis of SPSS could be used to predict the FPT of the most cultivars of P. bretschneideri, P. communis and P. pyrifolia, but not P. ussriensis cultivar such as ’Nanguo’pear.2. It was found in this work with’Whangkeumbae’pear fruits that-1℃～0℃treatment maintained fresh-keeping index of fruit petiole, decreased decay index, maintained firmness, soluble solid and titratable acid, decreased ethanol production and MDA content, inhibited respiration and ethylene release, decreased the activity of PPO. Comparison of effects of different temperature treatments showed that’Whangkeumbae’ pear could be stored about100d under1.5℃and about160d under-1℃～0℃.3. The study indicated that the controlled atmosphere with0.5%CO2+3%O2or0.0%CO2+3%O2decreased the fruit decay index and core browning, maintained firmness, soluble solid and low relative conductivity, decreased ethanol production and MDA content, inhibited respiration and ethylene release, decreased the activity of PPO and cellulose. In the short term,3.0%CO2or1.0%CO2treatment maintained stem fresh-keeping and titratable acid better than other treatments (<120d). It was seemed that the fruit injury by high CO2was accumulated, and the quality of fruits stored at3.0%and1.0%CO2conditions was even worse than that of the control. Comparison of the effects of different CO2proportion treatments showed that’Whangkeumbae’pear storage at the condition of O23%and0℃, and the proportion of CO2shoud be no more than0.5%.