HPAEC-PAD analysis of oligogalacturonic acids in strawberry juice

High performance anion-exchange chromatography (HPAEC), coupled with pulsed amperometric detection (PAD), was used to identify and quantify oligogalac turonic acids (OGAs) in strawberry juice. This method allowed good separati on and detection of OGAs with degree of polymerization (DP) < 20 units, and has proved to be a useful tool for the study of the chemical composition o f pectin breakdown products. However, the lack of availability of OGA stand ards above 3 DP units limited the quantification for these compounds. Treat ment of strawberry juice with seven commercial pectolytic enzymes was inves tigated. Glucuronic acid occurred in strawberry only in small amounts (12 /- 0.5 mg/l) and its concentration was not affected by the enzymatic treatm ent. Polygalacturonic acid can be hydrolyzed in several ways, yielding diff erent sets of oligomeric degradation products depending on the hydrolysis c onditions. The use of Rohament(R) MAX enzyme, for 2 h at 45 degrees C, prod uced juice with by far the highest concentration of OGAs. Moreover, treatme nt with Grindamyl Pectinase(TM) LM was also extended to 4 and 6 h to measur e the time course of pectinase activity and verify the stability of OGA. Th is enzyme generated high levels of pectin breakdown products proportionatel y with time (monitored up to 6 h) and increased the total level of OGAs wit h DP greater than or equal to 4 units from 78 to 771 mg/l. (C) 1999 Elsevie r Science Ltd. All rights reserved.