Study On Chilling Injury And Chang-temperature Treatments Of Postharvest "Dawuxing" Loquat Fruits

The research took the Sichuan specialities of "Dawuxing" loquat fruits as test materials, comparing the change of physiological and biochemical indexes in chilling injury temperature[(3±0.5)℃]and non-chilling injury temperature[(8±0.5)℃](which (8±0.5)℃as controls), and revealing the chilling injury and physiological characteristics. According to the serious chilling lignification of postharvest loquat, studied the control effect of Chilling program and Intermittent warming on chilling injury and revealed the possible mechanism. The main results were as following:It is proved that (3±0.5)±constant low temperature storage had low temperature coerce on "Dawuxing" loquat fruit.Fruits were observed chilling injury symptoms at ten days storage. With the prolonging of storage time, chilling injury became more serious. Chilling injury index came up to 39.25% after storage end.Chilling injury caused the respiratory metabolic abnormalities,the membrane permeability and the MDA content increase; prompted the active oxygen metabolism enzyme (SOD, CAT) and related lignification enzymes activitied(PAL, PPO, POD, CAD) increase, hardness and lignin content were increased and the degree of lignification of flesh were also increased. Chilling injury, meanwhill, decreased TSS, Vc, TA, SS and moisture content, maked SS/TA inbalance and nutrients severely reduces, so that affected the flavor of "Dawuxing" loquat fruit.The intermittent warmingⅠcould effectively reduce and delay the occurrence of chilling injury symptoms, alleviated the degree of flesh lignification, kept better storage and shelf life quality, maintained normal metabolicphysiology. At 48 days storage, fruit rot rate of the intermittent warming I was 15.83%, then was the chilling program of 20.83%, the intermittent warmingⅡof 21.67%, the contrast of 28.33%.In conclusion, the Intermittent warmingⅠwas the optimal variable temperature mode of "Dawuxing" loquat fruit.The possible mechanism of Intermittent warmingⅠwas that:by many times of short warming, the increased cell membrane permeability and MDA content were inhibited. The treatment inhibited the rising of PAL, POD, PPO, CAD activity and the increased lignin content. So that can keep higher SS and TA content and obtain better storage quality.The study of Frozen section microscopic structure indicated that the cellular structure of Intermittent warmingⅠwas lighter than the control and the Intermittent warmingⅠcould maintain the integrity of the cellular structure. The study of aroma compositions indicated that aroma compositions varieties and contents of Intermittent warmingⅠwere superior to that of the control fruit.