Influence of composition of edible films based on gellan polymers on l-(+)-ascorbic acid stability

Edible films made with gellan (deacylated) gum to carry l-(+)-ascorbic acid (AA) were formulated either in mixture with gellan acylated form or by addition of calcium ion. AA-stability and the subsequent non-enzymatic browning (NEB) development were evaluated during storage at 33.3%, 57.7% or 75.2% relative humidity and 25 °C. Presence of acyl-side chains in the gellan backbone led to a less rigid macromolecular network of the polymer mixture, which allowed lowering glycerol content, obtaining higher AA retention and lower NEB development with adequate mechanical characteristics of films. Otherwise, additional calcium presence in deacylated gellan film slowed down the browning development at the highest relative humidity of storage (75.2%). In general, it was observed an accelerating effect of local moisture mainly on non enzymic browning reactions, as well as the compromise of the film water content in plasticization of the polymeric networks when stored at 33.3% or 57.7% relative humidity.