Study On Aroma Characteristic Of Apple Fruits During Storage

‘Gala’ and ‘Honeycrisp’ apple were used as experimental materials in this study, thechanges of aroma components emitted by apple fruits during storage at20oC were measuredusing gas chromatography-mass spectrometry (GC-MS) and electronic nose technology, theeffects of1-MCP treatment on the aroma components of apples were also studied, thephysiological quality changes of apple fruits were measured. The general goal of this studywas to study variation of aroma components emitted by apple fruits during storage and toexplore the accuracy and feasibility of electronic nose technology in discriminate apples fromdifferent storage time.Main research results are as follows:(1) Forty-four and Forty-eight varieties of aroma volatile components were detected in‘Gala’ and ‘Honeycrisp’ apples during storage, respectively. They were devived into the sixfollowing groups as alcohols, aldehydes, esters, ethers, ketones and α-farnesene. The varietiesand total contents of aroma components emitted by ‘Gala’ and ‘Honeycrisp’ apple bothincreased to a high value and then decreased during storage, they both reached the maximumat12and28days of storage respectively. The main volatile components emitted by ‘Gala’apples at harvest and during storage were respectively aldehydes and esters, while the‘Honeycrisp’ apples were esters. There were six kinds of character aroma components of‘Gala’ apple, respectively as hexanal,(E)-2-hexenal, hexyl acetate, butyl acetate, butyl acetateand2-methyl hexyl butyrate,while the characteristic aroma components of ‘Honeycrisp’ applewere hexanal,(E)-2-hexenal, hexyl acetate, butyl ethyl2-methylbutyrate,2-methyl hexylacetate.(2) Electronic nose could detect changes of volatile compounds emitted by ‘Gala’ and‘Honeycrisp’ apple during storage. Principal component analysis (PCA) could not distinguishapples from different storage time of ‘Gala’ and ‘Honeycrisp’ apple, respectively. It also couldnot distinguish the CK and1-MCP treated apple from the same storage time. Lineardiscriminant analysis (LDA) could distinguish apples from different storage time of ‘Gala’apple, and also could distinguish the CK and1-MCP treated apple from the same storage time.Linear discriminant analysis (LDA) could distinguish the CK and1-MCP treatment‘Honeycrisp’ apple from0~42days of storage, but could not completely distinguish CK and 1-MCP treated ‘Honeycrisp’ apple from the same storage time. It was indicated by loadingsanalysis that sensors W5S (sensitive to nitrogen-oxygen compounds) and W1W (sensitive tohydrogen sulfide and terpenes) played central roles in the classification of apple fromdifferent storage time.(3)1-MCP treatment significantly reduced the varieties and contents of total aromavolatile components released by ‘Gala’ apple, reduced the contents of alcohols, aldehydes,esters and ethers, the treatment completely inhibited the α-farnesene generation, but has littleeffect on ketones. In addition,1-MCP significantly inhibited the characteristic aromageneration of ‘Gala’ apple;1-MCP treatment reduced the content of aroma componentsreleased by ‘Honeycrisp’ apple during storage, but had little impact on the type of aromacomponents.1-MCP significantly reduced the content of esters, ketones and α-farnesene. Itdelayed the peak levels of ketones, but had little effect on alcohols, aldehydes and ethers.1-MCP treatment inhibited the formation of the acetates characteristic aroma of ‘Honeycrisp’apple during storage, but had little effects on the formation of ethyl butyrate, ethyl2-methylbutyrate and ethyl hexanoate.(4) The physiological quality of ‘Gala’ and ‘Honeycrisp’ apple declined during storage atroom temperature,1-MCP treatment significantly inhibited the release of ethylene andrespiration of ‘Gala’ apple, delaying the occurrence of ethylene and respiration peak of‘Honeycrisp’ apple, thus inhibiting the fruit ripening and senescence, and effectivelymaintaining the physiological quality of fruit during storage.