Simplified sample preparation for analysis of sugar concentration in squeezed fruit juice by high performance liquid chromatography (Studies on Analysis of Sugars in Fruits Part II)

摘要

To establish a simpler method instead of alcohol extraction for HPLC analysis of sugars in Satsuma mandarins, melons, strawberries, grapes and Japanese pears, a method using squeezed fruit juice was studied. Sugar contents in each fruit juice which was analyzed immediately after squeezing showed high correlation with values achieved by ethanol extraction. Sugar composition of juice in Satsuma mandarin differed slightly from the data by ethanol extraction, but this was due to differences between sugar compositions in juice and residue. Sugar composition of Satsuma mandarin differed slightly with squeezing rate, so the method of squeezing must be consistent between samples to produce accurate results. When squeezed juice or diluted and filtered juices were placed at room temperature for 24 or 48 hours, respectively, sucrose degradation occurred in all samples except Satsuma mandarin. Microwave heating was found to be effective in reducing sucrose degradation in each of the samples except for undiluted grape juice. For these reasons, it has been concluded that the HPLC analysis using squeezed juice with proper microwave heating could give accurate data on sugar contents in many samples of fruits.