Factor analysis of the effects of controlled freezing-point storage in combination with 1-MCP treatment on quality of ‘Yulu' juicy peaches during cold storage

Abstract: 【Objective】Juicy peach is one kind of important fruit in china, which are harvested in high temperature season and have a short harvest time. It would be easily becomes soft and putrid after harvest for 2 to 3 days. Therefore, it is an important issue to extending its preservation period and shelf-life. Controlled freezing-point storage is a new preservation technology by which the fruits were stored at a temperature that above the freezing temperatures but below 0 ℃, and it has been proved to be an effective method for pear, kiwifruit, and so on. However, there were few related studies for juice peach. In this article,the effects of controlled freezing-point storage to combination with 1-methylcyclopropene(1-MCP)treatment on quality of‘Yulu'juicy peaches during cold storage were investigated, and it would be useful to provide theoretical basis for applying new preservation technology to juicy peaches.【Methods】In the preparation stage of this research, the freezing point, single fruit weight, total soluble solid content(TSS)of thirty‘Yulu'juicy peaches were determined, and the temperature of controlled freezing-point storage and relationships between those parameters were identified. Considering the temperature fluctuation of the cold store and irregulary TSS content,-0.8 ℃ was the optimal temperature to preserve juicy peach.‘Yulu'juicy peaches fruit at commercial mature stage were divided into four groups, one group was fumigated with 0.5 μL·L^-1 1-MCP for 20 hours, and then stored for 40 d at(-0.8 ℃) and RH 95% after precooling, the other three groups were stored at-0.8 ℃, 3-4 ℃,-0.5-0.5 ℃, respectively after pre-cooling,all the peaches were packed by 0.02 mm PE films with 18 teeth per basket. The changes of flesh firmness,total soluble solids(TSS), titratable acidity(TA) and ascorbic acid, colouration(L*), relative conductivity,browning index and sensory evaluation were investigated at sampling date for 20, 30,(30+2), 40,(40+2) d.Factor analysis was used to evaluate the quality changes.【Results】The results showed that the freezing point of juicy peaches was negatively correlated with TSS, the freezing point of juicy peaches harvested at mature stage about-1.5 ℃, and the temperature of controlled freezing-point storage has been determined as-0.8 ℃. During storage, firmness, TA, vitamin C, L*, sensory evaluation values decreased, relative conductivity, browning index value increased, and TSS did not change significantly. Compared with 3-4 ℃,(0±0.5) ℃ temperature storage treatment, controlled freezing-point storage and controlled freezing-point storage in combination with 1-MCP treatment could keep higher contents of TA, vitamin C, slower the decline trend of firmness and L*values, and browning of peaches were restrained. 1-MCP treatment could keep better effect of storage, that could keep firmness and sensory evaluation values significantly. In 3-4 ℃ temperature storage, the commodity quality could be kept for only 30 days, and after then, rotting and flesh browning got severity, and in(0±0.5) ℃ temperature storage, 40 days was its limitation that peaches could stored. In factor analysis, two principal components were extracted to instead of original indexes,which could explain products overall quality difference of 89.576%. The quality of fresh-keeping were followed by controlled freezing-point storage in combination with 1-MCP treatment, controlled freezingpoint storage,(0±0.5) ℃ cold storage, 3-4 ℃ cold storage. Scores and rankings of‘Yulu'juicy peaches with different treatments during storage were listed at the same time.【Conclusion】It was proved that, controlled freezing-point storage could reduce chilling damages significantly, and the quality of‘Yulu'juicy peaches were kept well for 40 days that were treated by controlled freezing-point storage in combination with 1-MCP treatment. However, further work should be done to study the reasons why controlled freezing-point storage reduce chilling damages, which is helpful to clear the theory principle and improve the storage quality persistently.