Identification Of Characteristic Aroma Compounds Of Corn-like Aroma Green Tea And Their Changes During Processing And Storage

Tea is popular beverage around the world for its various health benefits and unique flavor.Aroma is one of the most important factors affecting the characteristics and quality of tea.Chinese green tea,the most popular tea in China,presents different characteristic aroma types according it's sensory quality,such as chestnut-like,delicate floral aroma.Fangping green tea(FPGT),a Chinese green tea processed by Zhonghuang 1,was popular with consumers owing to its umami taste and typical cooked corn-like aroma.Therefore,this study aims to investigate the key odorants regarding cooked corn-like aroma tea by GC-MS,GC-O and aroma recombination,and compare the aroma contribution of individual components in a mixture by the value of ACI.And this study would provide modification of aroma-active compounds and the most important precursor of them in the green tea processing of Zhonghuang 1.In additional,this study aims to research the changes of aroma compounds and aroma sensory quality with time at different storage temperatures.It would be a clue for processing,quality control and storage of products.The main research contents and achievements are as follows:1.This study analyzed the aroma-active compounds of FPGT by GC-O,OAV and aroma recombination method.A total of 46 volatile compounds were detected by GC-MS,of which 9 compounds were OAV>10,including dimethyl sulfide,linalool,octanal,nonanal,?-ionone,pentanal,2-methylbutyraldehyde,benzaldehyde and ethyl acetate.19 active aroma compounds were detected by GC-O.Among them,the aroma intensities of dimethyl sulfide,hexanal,heptanal,benzaldehyde and ?-ionone were above 4.The OAV and ACI value of dimethyl sulfide were higher than other identified volatiles,which affected the aroma sensory performance of the tea.And aroma recombination could verify that dimethyl sulfide contributed the greatest to the characteristic cooked corn-like aroma of FPGT,while the other compounds provided the background of the aroma.2.To investigate the formation mechanism of the cooked corn-like aroma,fresh tea leaves of Zhonghuang 1(ZH)and Fudingdabai(CK)were applied to manufacturegreen tea under the same process conditions,respectively.Alcohols,aldehydes and esters accounted for a majority of the total content of aroma compounds in both of these two varieties,and the contents of aldehydes and esters in fresh leaves of ZH were 4.2times and half of fresh leaves of CK respectively.The loss of aroma compounds in ZH was more serious than that in CK during the process.DMS were not detected in fresh leaves and withered leaves,but it began to form after fixation and its content increased continuously during drying process.The increase rate of DMS in ZH was about 1.5times that of CK,which made the content of DMS in dried leaves of ZH significantly higher than that in dried leaves of CK.SMM contents presented a decrease during the process of green tea,especially after the roasting stage.The SMM contents in ZH were significantly higher than those in CK,which the main reason that the tea of ZH contains higher level of DMS.3.During the whole storage process,the total volatiles contents of tea samples decreased at first,then increased and then decreased.The contents of alcohols,aldehydes and sulfur compounds decreased on the whole,while ketones,nitrogen-containing compounds,alkenes and acids increased.Among them,acid compounds were only detected in the samples stored for 32 weeks.2,5-Dimethyl pyrazine,2-ethyl pyrazine,1-octen-3-one,safranal,(E,E)-2,4-heptadienal,?-ionone and dihydroactinidide were the main generated aroma compounds during storage.The contents of DMS,pentanal,hexanal,hexanol,cis-3-hexenol and 2-heptanone showed a downward trend during storage.The contents of octanal,nonanal,decanal,1-octene-3-ol,geraniol and linalool first increased with the increase of storage time,then decreased,and had the extreme value at 24 weeks.The contents of linalool oxide I,linalool oxide ?,methyl salicylate,1-ethyl-2-formylpyrrole,?-cyclocitral,benzaldehyde and ?-ionone increased with the increase of storage time.4.DMS content was significantly positively correlated with "corn-like" of corn-like aroma green tea.Therefore,taking DMS as the key factor of aroma change and shelf life prediction index of corn-like aroma green tea during storage to establish a kinetic model.Based on the Arrhenius equation,the shelf life prediction model of corn-like aroma green tea was established.The relative error between the predicted value and the measured value is less than 10%.It is clear that the model is reliable,which provides theoretical reference for predicting and monitoring the shelf life of corn-like aroma green tea during storage.