Native and cross-linked modified Dioscorea trifida (cush-cush yam) starches as bio-matrices for edible films

Abstract

Native and modified starches from non-conventional sources could be used as raw materials that represent appropriate bio-matrices to support diverse bioactive substances when formulating composite edible films or foams. In order to be used as raw materials, the starch and the starch-based films or foams obtained have to be characterized. The goals of this study were first, to isolate the starch from the edible portion of Dioscorea trifida, a sub-utilized agricultural commodity of the Venezuelan Amazons; second, to modify by cross-linking the native starch already isolated with sodium trimetaphosphate; third, to produce edible films with both the native and modified starches; and finally to characterize both while comparing their functional properties and proposing them to be utilized to produce foams. The bio-matrices represented by native and modified starches were used to formulate films with 5% of D. trifida starch and 1.5% glycerol. A native D. trifida starch with high purity was obtained, as well as a cross-linked modified starch with a 0.002% of degree of substitution. Significant statistical differences in the film thickness, color profile, deformation, and stress to puncture were found in both types of films. The modified starch-based films exhibited higher width and opalescence than those formed with native starch. The water vapor permeability, water retention, and water solubility differed also between both bio-matrices. The results suggested, in spite of these differences, that both of them could be proposed for gasification in order to obtain foams.