The Effects Of CPPU And 1-MCP Treatments On Color And Aroma Of Kiwifruit During Cold Storage

kiwifruit(Actinidia deliciosa cv.Qinmei)with 1-MCP and CPPU treatments was studied during 0℃±0.5 ℃ storage.The effects of different treatments on respiratory rate,ethylene production rate,soluble solid content,firmness and aroma component were studied.In addition,the effect of 1-MCP treatment on chlorophyll,chlorophyll derivative,activities of chlorophylase and Mg-dechelatase were studied.Moreover,quality prediction of kiwifruit by electronic nose and the electronic nose combined with Gas Chromatography-Mass Spectrometer(GC-MS)in aroma quality evaluation of kiwifruit were studied.The main objective of this study was to provide theoretical basis for rapid evaluation of kiwifruit quality including SSC,titratable acid and aroma components and the color-preserving technology.The results were as follows:(1)5mg/L CPPU accelerated ethylene production rate,degradation of organic acids and the maturity of kiwifruit.CPPU treatment significantly promoted the reduction of firmness during 30 days of storage.The firmness of kiwifruit with CPPU gradually reduced at day 45 and showed no significant difference from control.1.0μL/L 1-MCP significantly inhibited time of respiration peak and ethylene production rate.1-MCP significantly slowed down flesh softening and the reduction of titratable acid.1-MCP delayed the maturity and senescence of kiwifruit.1-MCP and CPPU treatments had no effect on soluble solid content(SSC).The combination of 1-MCP and CPPU treatments were effective in retarding the reduction of firmness,postponing the time of respiration peak and reduction of titratable acid,and then slowered fruit ripening process.(2)1.0μL/L 1-MCP increased activity of peroxidase and delayed the maturity and senescence of kiwifruit.1-MCP inhibited activities of chlorophylase and Mg-dechelatase,slowered the degradation of chlorophyll.1-MCP restrained productions of chlorophyllide a,pheophorbide a,chlorophyll a,chlorophyll b,pheophytin a and pheophytin b,then delayed the maturity and senescence of kiwifruit.The main chlorophyll in fresh kiwifruit included chlorophyll a,chlorophyll b,little pheophytin a and pheophytin b.Chlorophyllide a,pheophorbide a and pheophytin a were the main chlorophyll derivative during storage.The relative content of chlorophyllide and pheophorbide increased in the first stage,and then decreased during storage.Chlorophyll and pheophytin gradully decreased.(3)The aroma components of kiwifruit were studied using electronic nose during cold storage.The principal component combined with radial basis function neural network(RBF),multilayer perceptron neural network(MLP),Fisher discriminant analysis were used to built models which were used to predicted the storage time of kiwifruit.The results showed that the correct discriminant rates of MLP,RBF and Fisher models were 96.8%,90.6%and 96.7%,so MLP model was superior to others.The partial least-squares regressions(PLS),multiple linear regression(MLR)and back-propagation(BP)network were applied to evaluate SSC,firmness and pH value of kiwifruit with CPPU treatment.The determination coefficient of models by the PLS method for SSC,firmness and pH value in test set were 0.88,0.86 and 0.85,respectively.The root mean square error of prediction(RMSEP)were 0.62,2.58 and 0.08,respectively.The determination coefficient of models by the MLR method for SSC,firmness and pH value in test set were 0.92,0.88 and 0.86,respectively.The RMSEP were 0.51,2.38 and 0.08,respectively.The determination coefficient of models by the BP network for SSC,firmness and pH value in test set were 0.93,0.90 and 0.90,respectively.The RMSEP were 0.48,2.15 and 0.08,respectively.The results indicated that BP network led to more precise predictions than MLR method,and MLR method was superior to PLS method.The MLP and RBF were applied to evaluate SSC,SSC/TA,firmness and titratable acid of kiwifruit.The determination coefficient of models by the MLP network for SSC,SSC/TA,firmness and titratable acid in test set were 0.91,0.90,0.85 and 0.84,respectively.The RMSEP were 0.55、0.56、4.61、0.05,respectively.The determination coefficient of models by the RBF network for SSC,SSC/TA,firmness and titratable acid in test set were0.90,0.88,0.85 and 0.84,respectively.The RMSEP were 0.60、0.58、4.76、0.06,respectively.The results indicated that MLP network led to more precise predictions than RBF network.In a word,the combination of electronic nose and stoichiometric methods can well predict storage time and quality of kiwifruit.It is possible to build model between signal of electronic nose and fruit quality using quantitative analysis method.In addition,it is possible to use this non-destructive technique for measuring quality characteristics of fruit.(4)The relative content of alcohols,aldehydes and ketones aroma components of kiwifruit during storage gradually increased,when the relative content of hydrocarbons aroma components of kiwifruit gradually reduced.The relative content of esters aroma components of kiwifruit increased in the first stage,and then decreased.when inhibited esters and ketones production rates,1-MCP treatment promoted alcohols,aldehydes and hydrocarbons production rates.whlie inhibited alcohols,aldehydes and hydrocarbons production rate,CPPU treatment accelerated esters and ketones production rate.1-MCP and CPPU treatments both had no effect on types of alcohols,aldehydes,ketones,esters and hydrocarbons aroma components of kiwifruit.Esters were the main characteristics compositions of kiwifruit aroma compounds.The relative content of esters at 30d was higer than other storage times,so aroma of kiwifruit was best at the moment.The aroma components of kiwifruit with different treatments were studied using electronic nose.The results showed that aromatic benzenes,alkanes and alcohols changed significantly during storage.Moreover,these compounds were the main characteristics compositions of kiwifruit aroma compounds.when 1-MCP accelerated alkanes and alcohols production rate,CCPU inhibited alkanes production rate.This was consistent with results by GC-MS analysis.In a word,the electronic nose can rapidly detect change of kiwifruit aroma components.