Acid gelation of low acyl gellan gum relevant to self-structuring in the human stomach
ABSTRACT 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 c2 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.
- Food Hydrocolloids 10/2014; 40:76–84. · 4.28 Impact Factor
- Food Hydrocolloids 05/2014; · 4.28 Impact Factor
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ABSTRACT: This study investigated the in vitro acid-induced gelation of mixed systems of two biopolymers; low acyl and high acyl gellan gum. Rheological and texture analysis showed that these mixed gels displayed textures that lay between the material properties exhibited for the low and high acyl variants. DSC analysis showed that mixtures of the low acyl and high acyl forms exhibit two separate conformational transitions at temperatures coincident with each of the individual biopolymers. Various metabolically relevant pH environments and hydrocolloid concentrations were investigated. These resulted in very different acid gelled structures, which were characterised by texture analysis. The structures of the acid gels were shown to depend upon the pH, hydrocolloid concentration and proportion of each biopolymer used during their production. A selection of these mixed gellan structures were assessed post-production in terms of their response to prolonged exposure to an acidic (pH 1), stomach-like, environment. This resulted in a significant increase in the gel strength, regardless of the biopolymer proportions. The high acyl gellan was less acid-sensitive, and subsequently no evidence of acid gelation was observed with high acyl gellan at a proportion greater than 60% of the total biopolymer. The findings presented here demonstrate that structuring as well as de-structuring of mixed gellan acid gels can be controlled in acidic environments similar to those that are present in the stomach after food consumption.Food Hydrocolloids 03/2014; 35(100):522-530. · 4.28 Impact Factor