Analytical, Nutritional and Clinical Methods Section HPAEC±PAD analysis of oligogalacturonic acids in strawberry juice A. Versari a, *, S. Biesenbruch b , D. Barbanti a , P.J. Farnell c , S. Galassi d a DIBIAGA, Universita Á di Ancona, Via Brecce Bianche, 60131, Ancona, Italy b Leatherhead Food Research Association, Randalls Road, Leatherhead, Surrey KT22 7RY, UK c Laboratory of the Government Chemist, Queens Road, Teddington, Middlesex TW11 0LY, UK d Istituto di Industrie Agrarie, Universita Á di Bologna, Via San Giacomo 7, 40126, Bologna, Italy Received 8 April 1998; accepted 14 December 1998 Abstract 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 quanti®cation for these com- pounds. Treatment of strawberry juice with seven commercial pectolytic enzymes was investigated. Glucuronic acid occurred in straw- berry only in small amounts (120.5 mg/l) and its concentration was not aected by the enzymatic treatment. Polygalacturonic acid can be hydrolyzed in several ways, yielding dierent sets of oligomeric degradation products depending on the hydrolysis conditions. The use of Rohament 1 MAX enzyme, for 2 h at 45  C, produced juice with by far the highest concentration of OGAs. Moreover, treatment with Grindamyl Pectinase 2 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 54 units from 78 to 771 mg/l. # 1999 Elsevier Science Ltd. All rights reserved. Keywords: Pectin; Oligogalacturonic acids, OGAs; Pectolytic enzymes; HPAEC±PAD; Fruit juice 1. Introduction Pectic substances, polysaccharides of high molecular weight located in the cell walls, are involved in the changes of ®rmness in fruits and vegetables during ripening (Hwang, Pyun, & Kokini, 1993). The proces- sing of fruits and vegetables modi®es the pectin compo- sition of food and derived beverages. In particular, the pectic enzymes, which degrade the pectic substances, play an important role in the food industry mainly because of their ability to increase the extraction yield in the preparation of fruit juices (Whitaker, 1984). In fact, during juice manufacturing, high amounts of pectin are released into the juice and lead to problems during ®ltra- tion and clari®cation (Voragen & Pilnik, 1989). More- over, the stabilization of cloudy orange juice has been attributed to the depolymerization of pectic substances into soluble low molecular weight pectates (Baker & Bruemmer, 1972). The production of oligogalacturonic acids (OGAs) during the pectolytic activity is also of great interest from a regulatory point of view. In fact, a high level of OGAs is indicative of addition of peel and pulpwash in enzymatically treated orange juice (Farnell, 1995). The addition of these products to pure orange juice is not allowed in the UE. There is an increasing interest in the metabolic bene®t of ®ber such as pectin for human health. Evidence sug- gests that dietary pectin may reduce the levels of serum total cholesterol and decrease low density lipoprotein cholesterol (Behall & Reiser, 1986). Strawberry is a soft fruit containing high levels of pectin in which the monomer units consist mainly of d-galacturonic acid linked with dierent neutral sugars (Legentil, Guichard, Piaut, & Haluk, 1995). However, information on OGA composition of soft fruit and juice is still limited. Both the neutral and acidic sugars are useful compounds for monitoring the pectolytic degradation but speci®c ana- lytical methods are required (De Vries, Den Uijl, Vora- gen, Rombouts, & Pilnik, 1983). The recent use of high Food Chemistry 66 (1999) 257±261 www.elsevier.com/locate/foodchem 0308-8146/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved. PII: S0308-8146(98)00264-7 * Corresponding author. Biotechnology Research Institute, National Research Council Canada, 6100 Royalmount Avenue, Montreal, QC, Canada H4P 2R2. Fax: +1-514-496-6144; e-mail: andrea.versari@nrc.ca