| Oriental sweet melon (Cucumis melo var. makuwa Makino)‘Yumeiren’ was used asmaterial in this paper. Harvested melons were firstly treated by ethanol vapor and ethanoldirectly injected into the cavity of fruit. During storage period, the quality attributes andrelated physiological parameters of melons were investigated in order to determine a betteralternative. After that, different concentration ethanol vapors were applied to oriental sweetmelon for a further study, and then ethanol treatment were optimized. Different approachesand concentrations of ethanol application were mainly considered in this thesis, and wediscussed about the efficiency of exogenous ethanol on the postharvest quality maintenance.The aim was to reveal the mechanism of ethanol on the enhancement of sensory quality andphysiological changes. The results were described as follow:1. Melons were treated with6mL/kg ethanol vapor and ethanol directly injected into thecavity of fruit, distilled water vapor treatment was used as control. Two differentexogenous ethanol applications both maintained firmness and soluble solid content (SSC),enhanced the contents of fructose, glucose and sucrose in oriental sweet melon, especiallythe main sugar, sucrose. Moreover, both of ethanol treatments significantly reducedinternal ethylene concentration (IEC) in cavity of melons, while there is no ethylene peakoccurred.2. The exogenous applications of ethanol vapor and ethanol injection were both significantlychanged the composition of aromatic volatiles in flesh and peel tissues of oriental sweetmelons. The changes mainly contained the synthesis of ethyl esters and a greatenhancement of its contents. Eight esters were newly detected in both ethanol-treatedmelons compared with the control. Besides, both exogenous ethanol treatments enhancedthe activity of AAT, while there was no significant influence on the activities of LOX andADH. Overall, ethanol injection was more efficient on the volatile aroma in stored melonsduring short period, while ethanol vapor was more exhibited in a long term.3. Melons were treated with different concentrations of ethanol vapors,0.05mL/kg and3mL/kg, distilled water vapor treatment was used as control. Both concentrations ofethanol vapor significantly enhanced firmness and water contents, and decreased the SSC.Meanwhile, exogenous ethanol vapor maintained the overall color of melons, delay degreening of the rind and the decay of fruit during storage period. The results showedthat0.05mL/kg was the optimized concentration of ethanol vapor treatment.4. Both of different concentration of ethanol vapor treatment improved the composition ofaromatic volatiles to a certain extent. The relative contents of total ethyl esters weresignificantly increased after ethanol vapor treatments, while which of total acetate estersand characteristic aroma compounds decreased.3mL/kg ethanol vapor also had a moresignificant influence on the contents of several main sensory characteristic esters,including ethyl acetate, ethyl butanoate, butyl acetate, ethyl hexanoate, hexyl acetate.However,0.05mL/kg ethanol vapor had no obvious enhancement on these esters. Moreover, both concentration of ethanol vapor enhanced the activity of AAT in melons, and itpeaked ahead of that in the control. The activity of ADH was also increased by ethanolvapor treatment, while0.05mL/kg ethanol vapor exhibited more markedly effective.5. Both concentrations of exogenous ethanol vapors significantly inhibited internal ethyleneconcentration in oriental sweet melon during storage, and without a distinct climactericpeak. Exogenous ethanol vapors influenced ethylene biosynthesis, and results a significantdecrease of ACC content and the activities of ACO and ACS in oriental sweet melonsduring storage.0.05mL/kg ethanol vapor more effectively inhibit ACC level and theactivities of elated enzymes of ethylene biosynthesis, ACS and ACO.6. Both concentrations of exogenous ethanol vapors influenced ethylene responsiveness, andit showed a significant inhibition of the relative expression quantities of CM-ACS1,CM-ACS2, CM-ACS3and CM-ACO1, CM-ACO2, CM-ACO3during the storage periodwhen IEC in melons peaked.0.05mL/kg ethanol vapor almost entirely inhibited theexpression of ethylene responsiveness related genes, CM-ACS and CM-ACO, and theefficiency of which is more notable than that of3mL/kg ethanol vapor. |
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