Effects Of CO₂ Concentration In Modified Atmosphere Packaging On Postharvest Flavor Quality And Related Metabolism Of 'Lunnan' Apricot Fruits

'Lunnan' apricot is one of the most characteristic fresh apricot varieties in Xinjiang.Modified atmosphere packaging(MAP)is a kind of fresh-keeping method that has been developed and produced in recent years.It has a significant effect on the quality control of post-harvest storage and transportation of fruits and vegetables.In this study,the control conditions of CO2 accumulating MAP film materials were designed.After the packaging of fruits(acceptable maturity),the gas balance in the package was maintained until the O2 concentration(gas in volume fraction)was close to the atmospheric level,and the CO2 concentration was controlled to 1.50?2.00%,2.50?3.00%,and 3.50?4.00%three treatment levels,respectively.The changes of basic quality,respiration rate,ethylene and related metabolic products,metabolic enzyme activities,flavor species and content were recorded within 36 days after storage of the fruits.The changes of time series characteristics of related metabolic associations such as ethylene synthesis,polyamine,glycolysis and tricarboxylic acid cycle were analyzed.To explore the mechanism of different concentrations of CO2 affecting postharvest senescence metabolism in fruits,and provide theoretical basis for the regulation and technical optimization of postharvest quality maintenance.The following are main results.1.At the storage temperature of(1±1)?,there were significant differences in postharvest color and texture quality of MAP fruits.In the medium transmission packaged(2.50?3.00%CO2)apricot has the best fresh-keeping effect,inhibiting ethylene released from the fruit and the respiration rate of different paths,and maintaining the post-harvest quality of the fruit was relatively best.Compared with the control,the postharvest storage period of ' Lunnan'apricot fruits can be extended for 24 days.2.The concentration of CO2 in MAP can inhibit the conversion of sucrose in fruits and promote the accumulation of malic acid and citric acid.The regulation of CO2 concentration in medium transmission packaging was relatively good.Compared with the control,the sucrose content increased by an average of 0.47 times,and the malic acid and citric acid content increased by 0.12 and 0.42 times.The Embden-MeyerhofParnas pathway,methionine and cysteine metabolic pathway metabolism levels were relatively high in modified atmosphere packaged fruits,and the metabolite content and enzyme activity increased by 0.50?1.08 and 0.40?0.86 times.The concentration of CO2 in medium transmission packaging(2.50-3.00%)can promote the synthesis of polyamines to a greater extent in the 'Lunnan'apricot fruits,so as to better inhibit the release of ethylene and delay the post-harvest ripening process.3.During the storage process,the metabolic pathway of the control fruit is divided into three levels.At 0 days of storage,ethylene synthesis was promoted by Embden-Meyerhof-Parnas pathway and Tricarboxylic acid cycle;at 6?12 days,methionine synthesis promoted ethylene synthesis and peaked ethylene;at 18?36 days,cysteine synthesis and methionine synthesis together promotes the synthesis of polyamines.The regulation of CO2 concentration in high transmission packaging on fruit metabolism pathway is divided into two levels.At 0?6 days of storage,the synthesis of polyamines was promoted by Embden-Meyerhof-Parnas pathway,serine synthesis and cysteine synthesis;at 12?36 days,Tricarboxylic acid cycle and methionine synthesis promoted the synthesis of ethylene.The regulation of CO2 concentration in medium transmission packaging on fruit metabolism pathway is divided into three levels.At 0 days of storage,the Embden-MeyerhofParnas pathway was synchronous with ethylene synthesis;at 6?12 days,Tricarboxylic acid cycle and methionine synthesis promoted polyamine synthesis;at 18?36 days,cysteine synthesis promotes the synthesis of ethylene.The regulation of CO2 concentration in low transmission packaging on fruit metabolism pathway is divided into two levels.At 0?6 days of storage,Tricarboxylic acid cycle and ethylene synthesis responded synchronously;at 12?36 days,Embden-Meyerhof Parnas pathway combined with methionine synthesis promoted polyamine synthesis and cysteine synthesis promotes ethylene synthesis.During storage,the ethylene and polyamines of the high and medium transmission packaged fruits have an antagonistic effect.4.A total of 54 volatile substances were identified using Gas chromatography-ion mobility spectrometry(GC-IMS).Among them,2,3-pentanedione,(Z)-3-hexenol,3-methylbutanaland propionic acid are relatively high.The content of CO2 in MAP has increased the content of 14 substances of five flavors:green scent,fruity aroma,grass scent,licorice scent and sweet orange flavor;and the synthesis of amyl acetate and?-pinene with sweet fragrance and rosin flavor,reduced 2-hexanone synthesis.The flavor quality of medium transmission packaged(2.50?3.00%CO2)fruits was relatively good during storage.