Validation of a combined enzymatic and HPLC method for screening of pectins in fruits of Japanese quince (Chaenomeles japonica)

A combined enzymatic and HPLC method was validated for analysis of galacturonic acid (GalA) in (1) alcohol-insoluble solids (AIS), and in (2) pectins, extracted from fruits of Japanese quince (Chaenomeles japonica), by comparison with a standard colorimetric method (using metahydroxydiphenyl) for analysis of uronic acids (UA). For analysis of AIS, the results of the colorimetric mid lite enzymatic/HPLC methods were identical (UA and Gal,4 in average 20 g/100 g AIS dry weight), For analysis of pectins, the calorimetric method resulted in consistently higher estimates (UA in average 63 g/100 g pectins dry weight) compared to the enzymatic/HPLC method (GalA in average 57 g/100 g pectins dry weight). The enzymatic/HPLC method also proved to be useful as a simple and efficient screening method, since a very high Pearson correlation (R = 0.93) was obtained between GalA estimates of the homogenized fruit sample and the AIS content of acid-extracted pectins.