Effect of octenylsuccinic anhydride modification on ß-amylolysis of starch.

The effects of octenylsuccinic anhydride (OSA) modification of waxy maize and sorghum starches on subsequent ß-amylolysis are examined. Hydrolysis with ß-amylase is a method by which OSA starches may be structurally modified for industrial purposes. The hydrolysis of both granular and gelatinised forms of both starches follows first-order kinetics regardless of the OSA used as a percent of starch mass (0-24%). The highest hydrolysis rate coefficients for granular starches are at modification with 6% OSA/starch. The largest molecular sizes of ß-amylase hydrolysed OSA-modified gelatinised starches are found at modification with 24% OSA/starch. The results suggest that octenylsuccinyl groups have an action-blocking effect on ß-amylolysis of gelatinised starch, but the effect of semi-crystalline granular structure is more pronounced than that of OSA modification. Hence ß-amylolysis can be used under appropriate conditions to modify the structure of gelatinised OSA-modified starches.

The importance of amylose and amylopectin fine structures for starch digestibility in cooked rice grains.

Statistically and causally meaningful relationships are established between starch molecular structures (obtained by size-exclusion chromatography, proton NMR and multiple-angle laser light scattering) and digestibility of cooked rice grains (measured by in vitro digestion). Significant correlations are observed between starch digestion rate and molecular structural characteristics, including fine structures of the distributions of branch (chain) lengths in both amylose and amylopectin. The in vitro digestion rate tends to increase with longer amylose branches and smaller ratios of long amylopectin and long amylose branches to short amylopectin branches, although the statistical analyses show that further data are needed to establish this unambiguously. These new relationships between fine starch structural features and digestibility of cooked rice grains are mechanistically reasonable, but suggestive rather than statistically definitive.

Structure and physicochemical properties of octenyl succinic anhydride modified starches: a review.

Starches modified with octenyl succinic anhydride (OSA) have been used in a range of industrial applications, particularly as a food additive, for more than half a century. Interest in these products has grown in recent years as a result of new methods and applications becoming available. Due to a combination of OSA's hydrophobic and steric contribution and starch's peculiar highly branched macromolecular structure, these starch derivatives display useful stabilizing, encapsulating, interfacial, thermal, nutritional and rheological properties. We review the synthesis procedures, structural characterization methods and physico-chemical properties, and the influences of the botanical origins and structural parameters of OSA starches on physico-chemical properties. A better understanding of these features has the potential to lead to products with targeted macromolecular structures and optimized properties for specific applications.

New (1)h NMR procedure for the characterization of native and modified food-grade starches.

A novel, fast, and straightforward procedure is presented for the characterization of starch (the largest energy component in food) and modified starches (such as octenyl succinic anhydride (OSA)-modified starches used as a dispersing agent in the food industry). The method uses (1)H NMR to measure the degree of branching and also, for modified starches, the degree of chemical substitution. The substrate is dissolved in dimethyl-d(6) sulfoxide; addition of a very low amount of deuterated trifluoroacetic acid (d(1)-TFA) to the medium gives rise to a shift to high frequency of the exchangeable protons of the starch hydroxyl groups, leading to a clear and well-defined (1)H NMR spectrum, which provides an improved way to determine the degrees of both branching and chemical substitution. Measurements of the size and molecular weight distributions by multiple-detector size exclusion chromatography show that degradation by TFA does not affect the accuracy of the method.