Barley starch retrogradation

Proteins, lipids and phosphorus are the minor non-carbohydrate components of barley starch. These components have been shown to influence hydration rates, thermal properties, retrogradation characteristics, rhelogical characteristics, susceptibility towards a-amylolysis and processing, and product qualities of starch hydrolysates. 

Table 16.7 Enthalpy of retrogradation (J/g amylopectin) of barley starches...

Figure 16.13 Retrogradation enthalpy of small and large granules of normal barley starch. (Adapted from reference 93 with permission)...

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. 

Although all amylose molecules were once considered to be linear, many amylose molecules cannot be completely hydrolyzed by (3-amylase. With a concurrent or mixed action of pullulanase and beta-amylase, however, amylose can be completely hydrolyzed to maltose.150,151 These results rule out the theory that the incomplete hydrolysis of amylose by (3-amylase is a result of retrogradation, i.e. junction zone formation. It is now clear that the incomplete hydrolysis of an amylose preparation by (3-amylase is due to branching of some molecules. The (3-amylolysis limit of amylose varies from 72% to 95%152,153 compared with 55-61% for amylopectin. Amylose of most cereal starches, such as maize,154 rice,155,156 wheat157 and barley,158 give >80% (3-amylolysis... 

Table 16.8 Effect of annealing on the resistant starch (RS3) content of dried retrograded high-amylose barley and amylomaize starch gels...

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