Comprehensive Evaluation Of Textual Quality And Analysis Of Internal Cause Of Texture Difference Of Oriental Melon Fruit

Oriental melon(Cucumis melo var.makuwa Makino)is the first kind of melon to be used as fruit in China.The textural quality is an important standard to evaluate the quality of oriental melon.However,there have significant differences of texture property among a wide range of varieties.So,establishing a comprehensive evaluation method of textural quality of oriental melon,and exploring the key stages and the deciding factors of textural difference formation during fruit development can provide a theoretical basis for improving the textural quality of oriental melon.In this study,Firstly,we took 10 varieties of oriental melon with different texture characteristics named ‘Hongdaobian',‘Hualeiwang',‘Caihongqihao',‘Yumeiren',‘Qianyu',‘Baitangguan',‘Yangjiaomi',‘Xiangshami',‘Hongpimian' as trial materiels,we have measured the textural indexes and texture related biochemical indexes.A comprehensive evaluation score model of textural quality of oriental melon was established by the factor analysis,and the oriental melon varieties with different texture characteristics were classified by the systematic cluster analysis.Then,four representative varieties are selected from above,they were ‘Hongdaobian' with crisp texture,‘Yumeiren' with tough-hard texture,‘Xiangshami' with sand-soft texture,‘Hongpipian' with sand-soft texture to conduct the lateral study.At the macro level,the texture difference of the fruit was compared and analyzed by the texture analyzer.At the micro level,the natural fracture surface and the cell morphology of the sarcocarp tissure were observed by scanning electron microscope and paraffin section technique respectively.The changes of cell wall material composition,starch,Brix(%),water content and cell wall metabolism-related enzyme activity in the process of fruit development were analyzed.The main results are as follows:1.The factor analysis induced the texture indexes of oriental melon fruit into three main factors,F1(tough-hard factor),the F2(adhesive-soft factor)and F3(cohesive factor).The results show that the higher the score of F1 and F3,the lower the score of F2,the better the textural quality.The comprehensive score model based on factor analysis can achieved the comprehensive evaluation of textural quality of oriental melon fruit.The result shows that the textual quality of ‘Yumeiren' and ‘Caihongqihao' are superior,‘Hongpimian' and ‘Xiangshami' are poor,while other varieties were in the middle.The systematic cluster analysis can realized the accurate cluster of texture characteristics based on the texture analyzer indexes and texture related biochemical indexes.2.The texture difference of the fruit of the oriental melon fruit can be fully reflected by the texture analyzer indexes.In mature stage,‘Hongdaobian' and ‘Yumeiren' have higher TPA hardness,springiness,gumminess,cohesiveness,chewiness and puncture hardness.‘Xiangshami' and ‘Hongpimian' have lower TPA hardness,springiness,gumminess,cohesiveness,chewiness and puncture hardness.‘Hongdaobian' has extremely lower adhesiveness,while ‘Hongpimian' is opposite to it.3.The natural fracture pattern and the cellular morphology of sarcocarp tissure were the important factors to determine the texture characteristic.In mature stage,the sarcocarp tissure natural fracture model of ‘Hongdaobian' shows cell broken and has smaller cell packed closely with circular shape;The sarcocarp tissure natural fracture model of ‘Xiangshami' and ‘Hongpimian' shows cell separation and has smaller cell with long shape,and with bigger intercellular space,the shape of cell tend to irregular;the sarcocarp tissure natural fracture model of ‘Yumeiren' shows cell separation,cell size in mid and with circular shape and packed relatively tightly.4.During the development of fruits,with the decrease of the content of the cell wall material(CWM),the ratio of the water soluble pectin(WSP)increased,the ratio of the covalently bounding pectin(CSP)and the ionic bounding pectin(ISP)decreased,the TPA hardness,springiness,gumminess,chewness and puncture hardness decreased gradually and the adhesiveness increased gradually.In mature stage,‘Hongpimian' and ‘Yumeiren' have higher total pectin content,while ‘Hongdaobian' and ‘Xiangshami' have lower total pectin content.‘Hongpimian' has higher cellulose and hemicellose content,‘Xiangshami' has lower hemicellose,‘Hongdaobian' and ‘Yumeiren' have higher soluble solid content and lower water content.5.The changes of Polygalacturonase(PG),?-Galactosidase(?-Gal),and Cellulase avtivity play a key role in the transformation of oriental melon fruit texture.The activity of PG was positively correlated with the adhesiveness(P <0.05),and there was a significant negative correlation with the cohesiveness(P <0.01).The activity of the enzyme-Gal was negatively correlated with the internal cohesion(P <0.05).The activity of Cellulase was negatively correlated with the TPA hardness,the springiness and the puncture hardness(P <0.05).