Starch from hull-less barley: II. Thermal, rheological and acid hydrolysischaracteristics

Gelatinization, granular swelling, amylose leaching, viscosity and acid sus ceptibility characteristics of starches isolated from 10 hull-less barley ( HB) genotypes [zero amylose (CDC Alamo), waxy (CDC candle, SB 94794, SB 949 12, and SB 94917), normal amylose (Phoenix, CDC Dawn, SR 93102, and SB 9486 0) and high amylose (SB 94893 and SB 94897)] were monitored by differential scanning calorimetry (DSC), swelling power (SP), solubility, Brabender vis coamylography, and reaction with 2.2 N HCl (at 35 degreesC), respectively. DSC data showed that T-o, T-p, T-c, T-c-T-o, and DeltaH ranged from 50.1-56 .1, 58.1-64.5 71.0-75.8, 17.9-24.0 degreesC and 9.6-14.2 J/g of amylopectin , respectively. In compound waxy (SB 94917) and compound normal (SR 93102 a nd SB 94860) starches, T-o and T-c-T-o, were lower and higher, respectively , than in the other starches. DeltaH followed the order: compound normal > waxy > normal, zero amylose > high amylose > compound waxy. The SP followed the order: zero amylose > waxy > compound normal > normal > high amylose. A rapid increase in solubility occurred at lower temperatures (< 70 degrees C) for zero amylose, HB starch, however, this increase was gradual for the other starches. At 90 degreesC, solubility followed the order: high amylose > compound normal > normal > waxy. Zero amylose and waxy HB starches exhib ited lower pasting temperatures, higher peak viscosities, and higher viscos ity breakdown than normal HB starches. The extent of acid hydrolysis follow ed the order: zero amylose > compound waxy > waxy > normal > compound norma l > high amylose. High correlations were observed between physicochemical p roperties and structural characteristics of HB starches. (C) 2001 Elsevier Science Ltd. All rights reserved.