The Research Of Protocatechuic Acid And Pullulan Compound Coating Antistaling Agent On Fresh-keeping Pepper Postharvest

Pepper is a vegetable with high nutrient,which is so extremely contaminated by microorganisms that be corrupted.Although the effect of traditional physical and chemical preservation technologies is fine,due to the complex physical equipment,higher cost,chemical preservation hidden such factors that harmful to human health and pollution of the environment and so on.Natural coating preservation technology with environmental protection and high security advantages,After coating antstaling agent treat to fruits and vegetables in the surface in form a layer of transparent protective film,Not only prevent the damage caused by microbial infection of fruits and vegetables,but also inhibit the exchange of inside and outside conditions of fruits and vegetables,delayed ripening.In this study,the pepper（Xiangyan NO.15）as the materials,using different concentrations of single film-former by soaking treatment,under the temperature of 20℃,85%humidity storage,determine the weight loss and rot rate of pepper regularly,screening out the best film former and its concentration;Compared with the effect of preservation of the compound coating antistaling agent and single antistaling agent.By single factor and response surface analysis to the rot rate and weightlessness rate as measurement indicators,Determine the the optimal combination of compound coating antistaling agent of the effect on the pepper（Xiangyan NO.15）.And test the change of the respiratory intensity,nutritional quality and enzyme activity,provide technical support for compound coating antistaling on the pepper postharvest fresh-keeping.The main results were as follows:1.Use the concentration of 1.0%,2.0%,3.0%pullulan,0.5%,1.0%,2.0%chitosan,0.5%,1.0%,1.5%konjac purified powder,1.5%,3.0%,4.5%potato modified starch four different concentrations of film-former to soak the pepper（Xiangyan NO.15）,storage it in the temperature of 20℃,humidity condition of 85%,after 15d storage,measure its weightlessness rate and rot rate.Different concentrations of four kinds of Film former with a fine concentration on fresh-keeping pepper,there were 1.0%pullulan,1.0%chitosan,1.0%konjac flour,3.0%potato modified starch.Especially,the best effect of preservation of pepper is1.0%pullulan film-former,compared with CK1（without any treatment）and water group,the weightlessness rate were respectively decreased by 42.34%and 35.20%,the rot rate were respectively decreased by 33.33%and 46.67%,with significant difference（P<0.05）.2.The above selected 1.0%pullulan were compounded with 125mg/L protocatechuic acid,125mg/L oleanolic acid（protocatechuic acid and oleanolic acid were the monomer composition that with better preservative effect of pepper by our laboratory researched on earlier stage,the best concentration of Protocatechuic acid is125mg/L,to keep consistency,set the concentration of oleanolic acid to 125 mg/L）,composed of three kinds of composite coating antistaling agent（125mg/L protocatechuic acid+1.0%pullulan,125mg/L oleanolic acid+1.0%pullulan,1.0%pullulan+125mg/L protocatechuic acid+125mg/L oleanolic acid）to soak the pepper（Xiangyan NO.15）,and then,compared to 1.0%pullulan,125mg/L protocatechuic acid,125mg/L oleanolic acid on chilli fresh preservation effect,set CK1（without any treatment）,CK2（500mL of water containing 2mL 50%alcohol and 0.02%Tween-20）as blank control group,after 15d storage,measure its weightlessness rate and rot rate.The fresh-keeping effect of 1.0%pullulan+125mg/L protocatechuic acid compound coating preservative is superior to other groups,compared to CK1 and CK2,the weightlessness rate were respectively decreased by 64.28%and 49.98%,the rot rate were respectively decreased by 48.15%and 53.20%,with significantly difference（P<0.05）.Therefore,selected 125mg/L protocatechuic acid+1.0%pullulan to the best composite coating antistaling agent on pepper.3.The pullulan composite protocatechuic acid on optimization study of preservation of the peppers:use the concentration of protocatechuic acid（the best concentration of protocatechuic acid is 125mg/L by our laboratory researched on earlier stage）,concentration of pullulan,soaking time and the concentration of calcium chloride four factors as the independent variable,used the response surface optimization software to rot rate and the weightlessness rate of comprehensive weighted index to Determine the optimal combination.The results showed that the concentration of protocatechuic acid is 123mg/L,pullulan concentration with 0.45%,CaCl₂ concentration with 1.1%,the soaking time of 2.5min achieved best effect of preservation on pepper when the weighted comprehensive index was 5.63.4.The compound preservative effect on physiological and biochemical of the pepper（Xiangyan NO.15）:After the optimization of composite coating film preservative treatment（protocatechuic acid concentration is 123mg/L,soaking time was 1.5min,pullulan polysaccharides concentration is 0.45%,CaCl₂ concentration is1.1%）,set CK1（without any treatment）,CK2（500mL of water containing 2mL 50%alcohol and 0.02%Tween-20）as blank control group,use 1g/L chlorine dioxide preservation solution as a positive control.After 15d storage,the optimal group compared with CK1,CK2 and positive group,the weightlessness rate were respectively decreased by 41.66%,51.19%（P<0.05）,6.89%（P>0.05）.The rot rate were respectively decreased by 71.80%,74.42%and 21.43%（P<0.05）.Compared with CK1 and CK2,respiration intensity respectively decreased by 28.29%and23.32%significantly（P<0.05）.Chlorophyll loss rate reduced by 14.45%,14.45%,with significant difference（P<0.05）;8.78%,5.94%higher than that of brightness,colour and lustre is higher than 1.02%,1.48%,4.29%,5.91%higher than that of color saturation,with significant difference（P<0.05）.Vc loss significantly decreased by19.58%,19.58%（P<0.05）;Soluble protein content to reduce loss of 12.22%and12.22%（P<0.05）.The soluble solids are significantly higher than that of 19.15%and14.89%（P<0.05）.The accumulation of MDA was reduced by 44.57%and 37.55%（P<0.05）.CAT activity was significantly higher than 37.78%and 36.02%（P<0.05）.POD activity decreased by 12.69%and 9.37%respectively（P<0.05）.And PPO activity was reduced by 12.69%and 9.37%respectively,with different significant difference（P<0.05）.PAL activity than decreased by 32.09%and 29.47%,significant difference（P<0.05）.And the change of the total phenol content and PAL,reduced by35.25%and 26.66%significantly（P<0.05）.There were no significant difference with positive group（P>0.05）.To further prove that after the optimization of pullulan polysaccharides and protocatechuic acid composite coating antistaling agent of the pepper（Xiangyan NO.15）with good preservation effect.