Identification of headspace volatile compounds from different pear (Pyrus communis L.) varieties

Eight pear varieties including 'Bartlett', 'Packham's Triumph', 'Anjou', 'Comice', 'Bosc', 'Seckel', 'Vicar of Winkfield' and 'Forelle' were ripened optimally and volatile compounds from dynamic headspace were collected and identified by GC/MS. Among 112 compounds identified from all varieties, 47 compounds are reported the first time in pears. The volatile profiles of these eight varieties are characterized by compounds in groups of esters, alcohols, hydrocarbons, aldehydes, and ketones. Esters of short to medium chain alcohols and their corresponding acids with or without some degree of unsaturation are always present as a major group of compounds in all varieties. Esters comprise 60 to 98% of total volatiles among the varieties. Hexyl acetate represents the major ester in all cultivars except 'Bosc' and 'Vicar of Winkfield' which produced butyl acetate as a major ester, and 'Seckel' produced ethyl 2,4 decadienoate as the major ester. Decadienoate esters were detected in all varieties, but varied in amount and isomerization characteristics. Straight-chain alcohols with 2 to 8 carbons are present as the second largest group in the profile. Two isomeric forms (E,E and E,Z) of the sesquiterpene hydrocarbon, alpha-farnesene, are always present in the profiles but vary considerably in amount. A small number of aldehydes and ketones are also found in some varieties but present in very small amounts. Among the varieties studied, 'Comice' had the highest rate of volatile production at 42 mu g/kg/100 l of air while 'Seckel' produced the lowest at 0.7 mu g/kg/100 l.