Barley starch structure

This review has shown that most studies on barley starches have been focused on understanding the fine structures, particle size distribution, chemical composition, gelatinization properties and susceptibility towards enzyme hydrolysis. However, there is a dearth of information on the rheological and retrogradation characteristics of barley starches from different cultivars. Furthermore, the response of small and large barley starch granules towards physical and chemical modification needs investigation. Research in the above areas is underway in our laboratories. It is hoped that this study may improve the utilization of different types of barley starches for specific products within the food and paper industry. 

Branching isoenzymes from rice (21, 133), wheat (134, 135), and barley (136, 137) have also been characterized. The effects on starch structure in plants that have mutations in the starch-branching enzymes have been reviewed (2-4, 118, 124). 

The data19 summarized in Figure 1 show that the extent of the hydrolysis of soluble potato starch by barley beta amylase reaches a limit which is independent of the concentration of the amylase. The data are typical of the action of beta amylases on unfractionated starches, when the hydrolyses are carried out at or near pH 4.5.1 3 6 19 20 Under these conditions, the hydrolysis of unfractionated starches usually ceases when 60 to 64% of the maltose theoretically obtainable from the substrate has been formed. The exact value of the limit obviously will depend upon the concentration of amylopectin in the starch and upon its structure. 

Li, J.H., Vasanthan, T., Rossnagel, B. and Hoover, R. (2001) Starch from hull-less barley I. Granule morphology, composition and amylopectin structure. Food Chemistry 74, 395-405. 

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