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)

To establish a simpler method instead of alcohol extraction for HPLC analys is of sugars in Satsuma mandarins, melons, strawberries, grapes and Japanes e pears, a method using squeezed fruit juice was studied. Sugar contents in each fruit juice which was analyzed immediately after squeezing showed hig h correlation with values achieved by ethanol extraction. Sugar composition of juice in Satsuma mandarin differed slightly from the data by ethanol ex traction, but this was due to differences between sugar compositions in jui ce and residue. Sugar composition of Satsuma mandarin differed slightly wit h squeezing rate, so the method of squeezing must be consistent between sam ples to produce accurate results. When squeezed juice or diluted and filter ed juices were placed at room temperature for 24 or 48 hours, respectively, sucrose degradation occurred in all samples except Satsuma mandarin. Micro wave healing was found to be effective in reducing sucrose degradation in e ach 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 sample s of fruits.