| Aroma compounds analysis and variation, and physical and chemical characteristic index of eight pears cultivars were studied using high-resolution gas chromatography and the Solid-Phase Microextraction (SPME) method of gas chromatography/mass spectrometry (GC/MS) and High-Performance Liquid Chromatography (HPLC).SPME/GC/MS was used as principal method for aroma separation after comparing with other several four methods and many factors that affected pear fragrant compounds were discussed. The changes of aroma compounds and flavor components that connected with aroma compounds, such as, sugars content, organic acids content, pheonolic acids content, fatty acids content, amino acids content were studied. The aroma compounds of pear juice that was treated with high pressure and heated up were discussed, and the fragrant compounds of pear wine and pear distilled wine were first studied. Finally the comprehensive properties of freshed pear juice were described. The main results of this paper are as follows.The optimized SPME method was applied to investigate the qualitative aroma composition of the pear aroma after comparing with solvent extraction, vapour extraction, purging and trapping, simultaneous distilled extraction method.The optimum results were headspace extraction at 40 ℃ for 30 min after saturating the samples with 0.32g/mL sodium chloride salt. The order factors that effected on aroma extraction: temperature >time > NaCl based on orthogonal design data.The aroma composition and content differ from various pear cultivars. Moreover, the content of typical aroma component varies with the same cultivars from different producing- area. However , for all pear cultivars that was studied, the common aroma compounds was ethyl acetate; ethyl propanoate; butanoic acid, 2-methyl- ethyl ester; ethyl butyrate; butyl acetate; hexanol, hexanal; (E)-2-hexenal; ethyl hexanate; hexyl acetate; ethyl decanoate; ethyl octanoate; octyl acetate; 2,4-trans, cis-ethyl decadienoate.Aroma compounds of pear juice were effected by many factors, from our research that the fragrant composition and content was more in harvested late than in harvested early, and the optimum pH range for aroma formation is from 3 to 6. Additionally, oxygen and enzyme were all good for aroma formation. There was great difference in aroma composition between crashed and intact pear.Fructose was the dominant sugar in the eight pear varieties, followed by glucose and sucrose, while malic acid was the principal organic acid. The main pheonolic acid was chlorogenic acid. The C16:0, C18.0, C18.1, C18:2 and C18:3 fatty acids were clearly the most abundant fatty acids, and the C18 family comprised more than 70% of the total fatty acids content. Asparagine and Serine were the principal amino acids. The trace mineral compositions was identified in each of the eight pear that Potassium content was the highest, followed by Calcium, sodium and magnesium. The pear fruit composition differed according to variety.With increasing storage time, sucrose levels decreased, however fructose and glucose levels changed not remarkable. Some aroma components increased during storage especially the esters, such as, ethyl acetate, ethyl butyrate, hexyl acetate, ethyl hexanate and et al. while others decreased, The organic acids and phenolic acids and fatty acid and amino acids also changed. Yali pear flavor was affected by changes in the levels of volatile compounds, and chemical and physical properties, in conclusion, the cultivar retains good quality during storage.The optimum ultra high pressure condition was pressure 400Mpa, temperature 50°C, time lOmin, this condition can keep pear juice in good quality.The fresh pear juice was heated up from 50 to 120°C for5min, lOmin, 15min, 20min, 25min, 30min.The result was that ethyl octanoate and 2,4-trans,cis- ethyl decadienoate was not sensitive to time, and other esters were both sensitive to heat and time.The dominant compounds in pear wine was 1-butanol,3-methyl, ethyl acetate, 1-nonanol, 1-hexanol, 1 -propanol,2-methyl, formic...
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