Identification of gum Arabic in white wine based on colloid content, colloid composition and multi-element stable isotope analysis

Abstract

Gum Arabic (GA) is a popular wine additive. Due to its compositional and structural similarity to native grape cell wall arabinogalactans occurring in wine, the chemical proof of a GA addition is difficult. A method for its identification based on the colloid composition and multi-element (H, O and N, C) stable isotope analysis of the colloids was developed. For this purpose, the colloids from non-spiked, authentic (control) and spiked (300 mg l−1 GA) German white wines were isolated and analyzed for their monosaccharide composition. An addition of 300 mg l−1 GA changed the monomer sugar composition of the colloids. Particularly, l-arabinose, d-galactose, d-mannose and d-glucuronic acid were affected. Additionally, the oxygen stable isotope ratios of the isolated polysaccharides were shifted. Principle component analysis indicated the grouping of treated and untreated samples with 300 mg l−1 GA. The groupings were influenced by the content of l-arabinose and d-galactose, colloid content, monosaccharide content, monosaccharide composition and the δ18O values. It could also be concluded that a high content of l-arabinose and d-galactose was accompanied with a lower content of d-mannose. The control samples were only influenced by a significantly higher d-mannose content.