A simplified method for the determination of total oxalate-soluble pectin content in Japanese pear

The oxalate-soluble pectin is related to fruit firmness with respect to the chelation of calcium ions with carboxyl groups of adjacent polyuronide cha ins. However, the accurate total oxalate-soluble pectin content is not easi ly attainable. Using the Japanese pear fruits (Pyrus serotina Rehder var. c ulta 'Housui') as our model, we proposed a simple method to define extracti on time of total oxalate-soluble pectin in fruit without repetition based o n half-extraction time which is the time when oxalate-soluble pectin was ex tracted up to 50%. There were two stages of extraction: primary- and second ary-extraction stages. The different picking dates did not affect the extra ction rates and the unaccomplished ratios in the primary stage in which hal f-extraction time embedded but did affect in the secondary stage (P < 0.01) . The extraction time of total oxalate-soluble pectin could also be estimat ed. The method recommended that the extraction should be done until half-ex traction time was reached and the total oxalate-soluble pectin could be est imated by multiplying the pectin content at half-extraction time by two. We also postulate that the method may prove useful for other fruit and vegeta bles as well. Half-extraction time of Japanese pear was 2.1 h. (C) 2001 Aca demic Press.