| Piteguo is one of the local varieties which belongs to Pyrus ussuriensis Maxim andgrows mainly in cold and semi humid areas of the southwest Gansu. It has the characteristicsof liking the dark and damp, enduting the cold, resisting the plant diseases and insect pests etc.The traditional curing method of Piteguo is used to stacking a layer of straw and pears, Andthe progress of ripening spends15-20days in natural conditions. Since the traditional ripeningis affected by climate, it takes too long time and cause the high rate of decaying. Therefore,how to select suitable ripening manner, shorten the curing time, reduce the influence ofnatural climatic conditions in order to improve the rate of juice yield and the flavor has beenattracted much attention. It is also the effective means to solve the juiing bottleneck. In thisstudy, firstly, the curing temperature and concertration of ethephon have been optimized bycomparing Piteguo quality changing in different concertration of ethephon (1mL/L,2mL/L,3mL/L) and different temperature (20℃,25℃,28℃). Secondly, Piteguo quality, relatedenzymes (PMG, PG, PME, Cx, PPO, POD) activity in different periods and ripening fruitflavor were studied in detail on the preferred ethephon addition (experimental group1), thesuitable temperature (experimental group2) and the traditional curing (control group). Theresults showed that Piteguo quality, enzyme activity and volatile components were differentfrom different ripening methods, and the best way of ripening was25℃treatment. Thirdly,the enzymolysis conditions of squeezing juice were optimized. The data showed that the juiceyield was78.0%, increased by13.0%by comparing with the traditional squeezing yield,when the enzyme quantity was0.4g/L (the pectinase:cellulase was3:1), temperature was55℃and pH was4.0.The specific results are as follows:1. Ethephon treatment on Piteguo ripening time of sequence:2mL/L>1mL/L>3mL/L>CK; the2mL/L ethephon treatment effect was best, it made CK, ethephon(1mL/L,3mL/L)ahead of time7.3%,0.87%;The firmness was lower than the CK at16.7%. Ethephon group(1mL/L,3mL/L) were higher than the CK at4.53%,4.53%;The soluble solids respectivelywere higher than the CK at4.49%,1.14%,0.30%;The titratable acid were lower than the CK,ethephon(1mL/L) treatment at16.3%,10%.and higher than the ethephon(3mL/L) at2.86%.The weight loss rate were lower than the CK at5.21%, and higher thanethephon(1mL/L,3mL/L) at1.94%,1.06%. The text results showed that: under the condition of ethephon(2mL/L) treatment the firmness, titratable acid, weight loss rate were lower thanthe CK.The soluble solids were higher than the other groups, and the time of ripening is theshortest.2. Temperature treatment on Piteguo ripening time sequence:25℃> CK>28℃>20℃.the25℃treatment effect was best, it made CK,28℃,20℃ahead of time2.08d,2.31d,2.56d;The firmness was lower than the other group at42.50%,44.50%,46.51%; The soluble solidsrespectively were higher than3.23%,4.21%,1.13%; The titratable acid were lower than theother group at16.28%,17.78%,2.70%; The weight loss rate were higher than CK and20℃at7.01%,11.48%, and lower than the28℃treatment at5.65%. The text results showed that:under the condition of25℃treatment the firmness and titratable acid were lower than othertest groups. the soluble solids was higher than other test groups. the time of ripening was theshortest.3.The ethephon(2mL/L) and25℃treatment effected the fruit quality and enzymeactivity (PME, PMG, PG, Cx, PPO, POD), results showed that:The respiration intensity was up to15.28CO2mg/(kg.h) under the ethephon(2mL/L)treatment conditions on the12th day. it was higher than the CK at41.35%. The ethylenereleasing rate reached134.03μL/(kg.h) on the4th day, it was higher than30.16%comparedwith CK. The firmness, chlorophyll and titratable acid were significantly (P<0.05) lower thanCK on the4th day. The reduction sugar were significantly higher than CK on the8to12days,it was significantly lower than CK on the16days. The content of Vc didn’t have significantlychanging with CK. The cell membrane integrity rate was significantly (P<0.05) higher thanCK at8.75%on the12th day. It was81.3%and significantly higher than CK at18.4%on the16th day. The weight loss rate hadn’t remarkable difference on the early ripening period; itwas higher than CK at0.47%on the12th day. Enzyme activity hadn’t significant differenceon the early ripening period (0-4d). Enzyme activity (Cx, PME, PMG, PG, PPO, POD) weresignificant higher than CK at19.06%,5.38%,7.74%,13.39%,13.92%,16.34%on theripening mid-period.The respiratory intensity was up to15.79CO2mg/(kg.h) and higher than CK at46.07%under the25℃treatment conditions on the12th day. The ethylene releasing rate was up to106.31μL/(kg.h) on the4th day, it was higher than CK at3.24%.The firmness, chlorophylland titratable acid were significantly (P<0.05) lower than CK on the4th day. The reducingsugar was significantly higher than CK on the8th-12th day. It was significantly lower thanCK on the16th day. The content of Vc had no significant diversification on the early days, it was significantly (P<0.05) higher than CK at11.3%on the4th day. The rate of weight losswas up to6.14%and had no significant diversification on the early days; it was higher thanCK at0.27%on the12th day. Enzyme activities were not significantly on the early days(0-4).Cx, PME, PMG, PG, PPO and POD activity were significantly higher than the CK14.91%,5.83%,16.16%,2.40%,20.34%,35.48%on the medium days(4-8). According to firmness,soluble solid content, chlorophyll, Vc, weight loss rate, titratable acid and content of reducingsugar changing,25℃treatment ripening effect was relatively well.4. There were71kinds of volatile components in the process of ripening. the content ofester compound had22.48%. The content of alcohols was15.11%; With the fruit browningthe relative content of ester compounds showed increasing trend. The relative content of estercompounds were36.6%in the browning period(5-8d). With the fruit softening and browningthe relative content of ester compounds were41.56%in the mature period (13-16d). Therelative content of ester compounds were57.78%higher than CK at28.44%under theethephon treatment conductions in the softening period (9-12d). The relative content of estercompounds raised from36.58%to63.84%in the period of browning (5-8d), then remainedstable and the relative content of ester compounds declined slightly in the mature period(13-16d) under25℃treatment conductions.5. The enzymolysis experiments of squeezing juice showed that: the juice yield was78.0%, increased by13.0%by comparing with the traditional squeezing yield, when theenzyme quantity was0.4g/L (the pectinase:cellulase was3:1), temperature was55℃and pHwas4.0. |
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