The Effect Of Thidiazuron On The Flavor Quality Of Oriental Melon

Melon(Cucumis melon L.)is a major horticultural crop occupied an important position in the production and consumption of fruits and vegetables in China.It is also an important seasonal fruit to increase the income of the farmer.With the development of mordern agriculture,the area of facility cultivation was accounted for 48%of the total melon cultivation area.Due to the complexity of the melon’s characteristics and the limit of the cultivation environment,the thidiazuron was widely used as a plant growth regulator to increase the fruit setting rate of melon.However,with the widespread use of plant growth regulators,the phenoment of less flavor and taste were occurred occasionally.Are the phenoments related to the use of thidiazuron?How dose it effect?And what are the possible mechanisms?It has become a problem that needs to be solved in the the melon industry.In this research,the oriental melon was chosen as the target,and the field trail of thidiazuron was designed and carried out on it in the greenhouse.The degradation and residual of thidiazuron were also studied.The half-life of thidiazuron on oriental melon was estimated 1.28-1.56 d in Beijing.The final residue levels were all lower than the maximum residue limits(MRLs)of thidiazuron in China.There is no safety affect by the use of thidiazuron at the recommended concentrations.Furthermore,a comprehensive analysis method was developed based on gas chromatography-mass spectrometry(GC-MS),gas chromatography-ion mobility spectrometry(GC-IMS),liquid chromatography-mass spectrometry(LC-MS),electronic nose,and electronic tongue sensor array.The effect of thidiazuron on the fruit quality(appearance,aroma and flavor)of melon was evaluated.It was found that thidiazuron can increase the growth rate of oriental melon during the first stage of melon growth,but it has little effect on the growth rate in the later stage of melon growth.Thidiazuron can also reduce the yellowness and brightness of melon fruit.Moreover,thidiazuron can increase the hardness of melon,and there was a significant relationship between the fruit hardness and the concentrations of thidiazuron.There was a significant difference in the volatile components of melon with the different concentrations of thidiazuron by using the electronic nose.With the increase of the concentration of thidiazuron,the distance from the control samples area was increased by the principal component analysis(PCA)of GC-MS data.It is suggested that the use of thidiazuron can impact the aroma composition and there was a certain relation between the concentrations of thidiazuron and the aroma.And 94 volatiles were identified by gas chromatography-tandem mass spectrometry(GC-MS/MS)in melon,mainly including esters,aldehydes and alcohols,and in which 68 volatiles contributed to the change of melon aroma.The similar results can be obtained by the ultra-fast gas-phase electronic nose analysis.13 volatiles were identified which were related to the change of aroma of melons.The profiles of the taste of the melon with the different thidiazuron were obtained using the electronic tongue detection.There was a significant difference occurred in the flavor composition of melon treated with different concentrations of thidiazuron.It was reduced the content of soluble solids of melons,but increased the content of fructose and raffinose by use of the low concentrations of thidiazuron(<5 mg/kg).When the high concentrations(6-8 mg/kg)of thidiazuron was used,the opposite phenomena were observed.It is should be noted that the content of vitamin C and citric acid in the melon was decreased by using the thidiazuron indicating that thidiazuron can adjust the metabolism of melon sugar.The change of the content of some of the important precursor of volatile amino acids substance can indirectly affect the melon flavor of melon.Based on the above results,the use of thidiazuron can affect the aroma composition and flavor components of oriental melon.And low concentration(4 mg/kg)of thidiazuron has little effect on it under the recommended dose.