Acid gelation of low acyl gellan gum relevant to self-structuring in the human stomach

The aim of this study was to investigate the in vitro acid-induced gelation of low acyl gellan gum. Various metabolically relevant pH environments and hydrocolloid concentrations were investigated. These resulted in very different acid structures, which were characterised by texture analysis, with Young's and bulk moduli and work of failure being reported. The structures of the acid gels were shown to depend upon the pH and hydrocolloid concentration (c) used during their production, with a maximum in gel strength between pH 3 and 4. Both the Young's and bulk moduli data suggest that there is a critical concentration for gelation to occur, and both parameter values displayed a gradual increase (which appears to be lower than a c(2) dependency) as the gellan concentration was increased. Finally, these acid structures were also assessed post-production in terms of their response to prolonged exposure to an acidic (pH 1), stomach-like, environment. Exposure to the acid bath showed that the gel structure remains unaffected if it was originally produced at pH 3, but showed an increase in strength for those gels produced at pH 4 and pH 5 and a decrease for the gels initially produced at pH 2. Overall the findings presented here are promising as they clearly demonstrate that structuring as well as de-structuring of gellan acid gels can be controlled at acidic environments similar to those that are present in the stomach during and post-meal consumption. (C) 2010 Elsevier Ltd. All rights reserved.