Processing stability of cross-linked starches in acid sauce applications and identification of some of the molecular factors involved

The thickening functionality of four acetylated di-starch adipates with variations in starch source and amylose and adipate contents was evaluated in a simplified small-scale model sauce system at fourteen processing conditions with variations in temperature, shear, and pH. A processing stability factor for a given starch was defined as a normalised standard deviation of model sauce viscosities calculated over all fourteen treatments. Adipate and acetate substituents were stable at all processing conditions. The processing stability of modified starches was found to decrease in the order waxy maize> amylopectin potato > normal potato. The release of solubles increased in that order and the solubles from the normal potato starches were enriched in amylose. Molar mass determinations of the soluble fraction before and after saponification of the cross-links revealed that processing at high temperature caused much more molecular degradation than at high shear and that in all cases the soluble fraction was only scarcely cross-linked. These results suggest that the negative effect of amylose on processing stability is due to its ineffective cross-linking in the intact starch. Distinct morphological changes were induced by processing: generally, swollen cross-linked starches respond to processing by the common swelling and leaching pattern, but amylopectin-starch granules subjected to high shear are disintegrated into tiny particles. Presumably, these morphological responses are related to the effectiveness of cross-linking in the processed starch granules.

Spider web plots for three starches showing the effect of processing on model sauce viscosity.Figure optionsDownload as PowerPoint slide