Organic Acid Composition in the Pulp of Loquat (Eriobotrya japonica Lindl.) and Distribution in Fruits

Organic acids from the ripe pulp of 18 loquat(Eriobotrya japonica Lindl.)cultivars(‘Xiaomaopipa’,‘Jiajiao’,‘Zhuonan 1’,‘Jiefangzhong’,‘Fuyang’,‘Moriowase’,‘Huabao 2’,‘Xiangzhong 10’,‘Baihua’,'‘Toi’,‘Duobao 2’,‘Wugongbai’,‘Luoyangchin’,‘Mogi’,‘Zaozhong 6’,‘Baili’,‘Tantou 4’,‘Changhong 3’)and their distribution in the ripe fruit of 2 cultivars('Jiefangzhong' and 'Zaozhong 6')were determined by high-performance ion-exchange chromatography(HPIC).Eight organic acids(malic,quinic,citric,iso-citric,α-ketoglutaric,fumaric,oxaloacetic and tartaric acids)were identified in ripe pulp,while trace quantities of ferulic,cis-aconitic and β-coumaric acids were identified in several cultivars.The predominant organic acid of ripe pulp of most cultivars was malic acid,with an average content of 4 399 mg kg-1 FW for all cultivars,accounting for 62.7% of the total acids.Quinic acid was the second in abundance,with an average content of 2 042 mg kg-1 FW,accounting for 29.1% of the total acids.Other acids ranged from trace to 3.0% of the total acids.Considerable variations in titratable acidity and organic acid content exist among cultivars.Based on titratable acidity,18 cultivars could be separated into 5 groups by clustering analysis:very high acidity(‘Xiaomaopipa’),high acidity(‘Jiajiao','Zhuonan 1’,‘Jiefangzhong’ and‘Fuyang’),medium acidity(‘Moriowase’,‘Huabao 2’,‘Xiangzhong 10’,‘Baihua’,‘Toi’,‘Duobao 2’),low acidity(‘Wugongbai’,‘Luoyangchin’,‘Mogi’ and ‘Zaozhong 6’),and very low acidity(‘Baili’,‘Tantou 4’ and ‘Changhong 3’).No significant difference was found in the absolute amounts of total acids and titratable acidity between pulp and skins,while the amounts of total acids and titratable acidity in seeds was far lower than those in pulp and skins.The major organic acids identified in skins and seeds were malic and quinic acids.In skins,the content of malic acid was far higher than quinic acid,but in seeds it was slightly lower than quinic acid.In addition,malic acid and quinic acid content in seeds was far lower than those in pulp and skins.