###### Abstract  
Metabolites play vital roles in shaping the quality of fresh fruit. In this study, Korla pear fruit harvested from twelve orchards in South Xinjiang, China, were ranked in sensory quality by fuzzy logic sensory evaluation for two consecutive seasons. Then, gas chromatography-mass spectrometry (GC-MS) was applied to determine the primary metabolites and volatile compounds. Sensory evaluation results showed that the panelists were more concerned about'mouth feel' and 'aroma' than about 'fruit size', 'fruit shape' and 'peel color'. In total, 20 primary metabolites and 100 volatiles were detected in the pear fruit. Hexanal, (_E_)-2-hexenal, nonanal, p-limonene, (_Z_)-3-hexen-1-yl acetate and hexyl acetate were identified as the major volatile compounds. Correlation analysis revealed that l-(+)-tartaric acid, hexanoic acid, trans-limonene oxide and 2,2,4-trimethyl-1,3-pentanediol diisobutyrate were negatively correlated with sensory scores. Furthermore, OPLS-DA results indicated that the fruit from three orchards with lower ranks in quality could be distinguished from other samples based on the contents of l-(+)-tartaric acid and other eight metabolites, which were all associated with'mouth feel' and 'aroma'. This study reveals the metabolites that might be closely associated with the sensory quality attributes of Korla pear, which may provide some clues for promoting the fruit quality in actual production.  
metabolites; Korla pear fruits; sensory evaluation; fuzzy logic model +
Footnote †: journal: molecules  
0000-0002-2520000/00000-00002-252000/  
Aroma and taste are important indicators of fruit quality, and are closely related to fruit metabolites due to the complex interactions between metabolites and human senses. Metabolites such as soluble sugars, organic acids and volatiles play important roles in fruit sensory quality. Although there has been extensive research on the metabolites in different pear cultivars [1; 2; 3; 4; 5; 6; 7], few studies were focused on the fruit sensory quality and relevant metabolites of Korla pear [8; 9; 10; 11]. In Korla pear, aldehydes and esters such as hexanal and hexyl acetate are dominant volatile compounds [8; 12; 13]; while fructose and malic acid are the major soluble sugar and organic acid, respectively [3; 5]. Compared with other pear cultivars, Korla pear has a higher sugar/acid ratio that contributes to its excellent taste [3].  
Sensory evaluation plays a vital role in the assessment of food preference. Combination of chemical and statistical analysis with sensory evaluation can well demonstrate the association between the sense and compounds in food. Since information acquired from human senses cannot enable precise quantitative assessment, fuzzy logic has been employed for more reasonable ranking of food samples [14; 15; 16]. It has become a commonly used method for the sensory evaluation of foods such as beverages and tea products [17; 18; 19]. Nevertheless, it has only been applied to the sensory evaluation of a limited number of fresh fruit varieties [20; 21; 22], and is more often used to explore the correlations between sensory evaluation results and food chemical compounds [23; 24; 25; 26]. In this study, we attempted to firstly evaluate the sensory quality attributes of Korla pear from 12 orchards, and then determined the primary and volatile metabolites. Finally, the pear fruit samples were ranked according to the sensory scores to determine whether the sensory quality attributes are related to the production areas and some key metabolites. The findings may help the regionalized planting of Korla pear in Xinjiang on the basis of fruit quality and sensory quality attributes, and provide theoretical support to promote and stabilize the fruit quality in actual production.