Structural characterization of an apple juice arabinogalactan-protein which aggregates following enzymic dearabinosylation

• Published in: Carbohydrate polymers 1996, Vol.29 (3), p.271-275
• Main Authors: Brillouet, Jean-Marc, Williams, Pascale, Will, Frank, Müller, Guy, Pellerina, Patrice
• Format: Article
• Language: English
• Subjects: apple juice; arabinose; Biological and medical sciences; carbohydrate composition; carbohydrate structure; Chemical Sciences; chemical structure; composition; Food industries; Fruit and vegetable industries; Fundamental and applied biological sciences. Psychology; galactans; isolation; molecular weight; Polymers; sugars
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/0144-8617(95)00152-2

An arabinogalactan-protein (AGP) was isolated from a cider apple juice and contained arabinose and galactose as the main sugars ( Ara Gal mol ratio 0.67), with some uronic acids (1.4%) and protein (1.7%). Its weight-average molecular weight ( M w ) was 80 kDa. Enzymatic dearabinosylation of AGP with a purified α- l-arabinofuranosidase released 95% of arabinose and left a galactan-protein GP 1. Enzymatic degalactosylation of GP 1 with a β- d-galactosidase released 42% of galactose giving GP 2. Methylation analysis of AGP, GP 1, and GP 2 revealed that AGP is built of inner chains of (1→3)-linked galactosyl residues 6-substituted by (1→6)-linked galactan outer chains 3-substituted by terminal arabinofuranosyl units. After dearabinosylation, β- d-galactosidase hydrolysed specifically 76% of (1→6)-linked galactan outer chains. Removal of arabinofuranosyl substituents led to partial aggregation of GP 1 upon freeze-drying, and further elimination of (1→6)-linked galactan outer chains by β- d-galactosidase did not alter the aggregation phenomenon. The formation of aggregates reveals the possibility that enzymatic degradation of AGPs can lead to haze formation in fruit juices.