Cell walls in plants are mainly composed of polysaccharides. Among them, pectin, cellulose and hemicellulose are composed of various sugars residues (acidic: galacturonic acid in pectins; or neutral: rhamnose, galactose, arabinose, xylose, glucose in cellulose, hemicellulose and pectic side chain). This fine composition affects the structure but also the behavior and mechanical properties of cell walls and consequently the textural properties of RTB foods. In raw products and/or after cooking some cell wall components are soluble (eg. some pectin). This procedure seeks to determine the galacturonic acid level extracted from pre-dried (dried or freeze-dried) RTBs. This method gives the galacturonic acid content of cell walls extracted with different solvents, independently of the neutral sugars content. Pectin are first extracted at intermediate temperature (55°C) to facilitate their extraction while limiting their chemical and enzymatic degradation and the extraction of starch (temperature below starch gelatinization). Extracted pectin are then hydrolyzed by hot sulphuric acid in order to obtain sugar residues and their furfural derivatives. Neutral sugars gave brown derivatives whereas free galacturonic acid is quantified by colorimetry after reaction with MHDP which produces a specific fuschia pink complex with a maximum absorption at 520 nm (Blumenkrantz and Asboe-Hansen, 1973). Galacturonic acid content is calculated after subtracting the brown colour (at 520 nm) generated by neutral sugar hydrolysis.