Effect Of Lipid And Abscisic Acid Agent Treatment On Chilling Injury In Postharvest Green Peppers

Capsicum is a cold sensitive fruit,which is susceptible injury at a certain low temperature,and at this temperature its qualities would be deteriorated.The experiments were carried out with pepper?Capsicum annuum L.var.Longum Baiey?stored at low temperature or ambient temperature.The pepper were dipped by stigmasterol,abscisic acid?ABA?and linolenic acid?LNA?.Some qualities,like physiological and biochemical indexes during storage were determined.The spectral changes were studied by fluorescence spectrophotometer and fourier?transformation?near infrared spectroscopy?FT-NIR?.The changes of main fatty acids in membrane phospholipid were detected.It was expected to find new agents to improve the low temperature resistance ability for"Hangzhou pepper",and relieve the deterioration caused by low concentration.It was also expected that pepper could be stored and transported at a lower temperature in future,and chilling injury symptoms of pepper in winter could be mitigated.The main conclusions were as follows:?1?The chlorophyll fluorescence,sensory quality,weight loss rate and electrolyte leakage rate of pepper stored at different temperatures were measured.Results were as follows:chlorophyll fluorescence Fo value of pepper before storage could be used as a non-destructive indicator of pepper maturity,and provide a reference for the low temperature storage temperature of pepper.Peppers with larger Fo value have lower maturity and are safer to store at 8?.The smaller Fo value is,the higher the corresponding maturity,the longer the shelf life of the pepper fruit is,and the better the low temperature resistance is.Peppers with good low temperature resistance were stored at 4?,the storage period of pepper could reach18 d,the weight loss rate and electrolyte leakage rate could be delayed,and the fresh-keeping effect was better than 0?and 20?.?2?Peppers were stored at 4?,the quality of pepper fruits were measured,and fluorescence?near-infrared spectra were scanned during storage.Results were as follows:at4?,the changes in fluorescence intensity of Ex-254 nm and Em-418 nm were highly correlated with changes in quality and chilling injury-related indicators,and the fluorescence intensity was not detected at room temperature,so this fluorescence intensity can be used as detection indicators of pepper in cold damage.There was a close correlation between the absorption values at 5150 cm^-1,or 6875 cm^-1,or 8350cm^-1and the changes of senescence indexes?appearance quality,weight lose rate,chlorophyll,soluble protein content?at 4?.The absorption peak of 6875 cm^-1was greatly affected by the moisture content,and 5150 cm^-1absorption value had the best correlation with the senescence index of pepper at low temperatures,and this peak change can be used to analyze aging.?3?0.05-0.10 g/L Tween-20,Tween-80 and soy lecithin were used for the experiment.The sensory quality of pepper was evaluated,and the weight loss rate,cell membrane permeability and chlorophyll fluorescence parameters were measured.Results were as follows:it was most suitable to dissolve oil-based preservatives with Tween-20 treatment.Pepper suffered chilling injury at 0?and its shelf life was 3d.Soy lecithin treatment significantly maintained the sensory quality of pepper,prolonged life,reduced cell membrane permeability,reduced chilling injury,and was closed to control group on Y???and ETR.Low concentration of Tween-80 promoted weight loss of peppers,while high concentration showed the reverse effect.Tween-80 treatment significantly increased cell leakage,promoted chilling injury,and were closed to those of the control on Fv/Fm,Y?NO?.The appearance quality,cell leakage rate,and weight loss rate of the pepper treated with Tween-20 were approaching or equal to those of the control,and their effects on the fluorescence parameters Y???,ETR,and q N of pepper also approached to those of the control.Summarily,the minimal difference was between the Tween-20 treatment and the control.?4?0.050-0.500 g/L stigmasterol,0.050-0.500 g/L ABA and 0.015-0.300 g/L LNA were used for experiment.The sensory quality of pepper was evaluated,and the weight loss rate,cell membrane permeability and chlorophyll fluorescence parameters were measured.Results were as follows:to a certain extent,stigmasterol,high-concentration ABA and LNA could relieve chilling injury,but the low-concentration ABA treatment group reduced the sensory quality of pepper during storage.0.50 g/L stigmasterol,0.40 g/L ABA and 0.06 g/L LNA were found as the optimum treatment concentration.Both stigmasterol and ABA treatments could reduce weight loss and maintained the sensory quality of pepper,significantly reduced cell membrane permeability,significantly retarded chlorophyll fluorescence parameters Fv/Fm decrease,and reduced chilling injury.LNA treatment reduced weight loss,maintained the sensory quality of pepper and retarded Fv/Fm decrease,but promoted electrolyte leakage rate.?5?Pepper were dipped by 0.50 g/L stigmasterol,0.06 g/L LNA,0.40 g/L ABA for 20min,and then stored at 4?.The quality of pepper and antioxidant ability and major fatty acids content in membrane were determined,and fluorescence and near infrared absorption spectrawere were analysed during storage at ambient temperature.The results showed that both stigmasterol and ABA could improve the chilling resistance of postharvest peppers and extend the shelf life.ABA was effective in preventing the degradation of total fatty acids,and stigmasterol was effective in maintaining linolenic acid.All treatments could maintain their commercial value within 12 days.The control group rotted on the 18^thday,but all treatments did not rot on the 25^thday,which indicated that all treatments delayed the occurrence of rot,and the effects of both stigmasterol and ABA were better.All treatments inhibited the reduction of reduced ascorbic acid,promoted the activity of antioxidant enzymes,significantly reduced the rate of electrolyte leakage in the later period,and delayed the decrease of chlorophyll content in the middle and late periods.Both stigmasterol and ABA treatments could reduce weight loss and significantly reduce malondialdehyde in the early storage period MDA),which inhibited the degradation of soluble proteins and the chilling aging fluorescence in the middle and late stages.Among them,ABA treatment had the best effect.ABA promoted electrolyte extravasation and reduced ascorbic acid content during the early storage period,and had a good preservation effect,but the chili spoiled and rotted quickly in the later period.The hydrocarbon content decreased,and the fluorescence intensity of aging and chilling damage increased in 25 d,which suggested that ABA treatment may has side effects.The chili was refrigerated for 25 days,and the fatty acid decreased by about80%,which destroyed the cell membrane structure.Different effects of three preservatives on film composition.ABA treatment strongly prevented the total amount of fatty acids from decreasing,and stigmasterol and LNA treatments prevented the decline of unsaturated fatty acid ratios and increased the ratio of unsaturated and saturated fatty acids.However,LNA treatment did not have a significant preservation effect,and near-infrared spectroscopy showed that C-H compounds decreased the most.