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 oligogalacturonic acids (OGAs) in strawberry juice. This method allowed good separation 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 of pectin breakdown products. However, the lack of availability of OGA standards above 3 DP units limited the quantification for these compounds. Treatment of strawberry juice with seven commercial pectolytic enzymes was investigated. Glucuronic acid occurred in strawberry only in small amounts (12±0.5 mg/l) and its concentration was not affected by the enzymatic treatment. Polygalacturonic acid can be hydrolyzed in several ways, yielding different sets of oligomeric degradation products depending on the hydrolysis conditions. The use of Rohament® MAX enzyme, for 2 h at 45°C, produced juice with by far the highest concentration of OGAs. Moreover, treatment with Grindamyl Pectinase™ LM was also extended to 4 and 6 h to measure the time course of pectinase activity and verify the stability of OGA. This enzyme generated high levels of pectin breakdown products proportionately with time (monitored up to 6 h) and increased the total level of OGAs with DP ⩾4 units from 78 to 771 mg/l. ©