Starch from six cultivars of oat grains (grown under the same environmental conditions) was isolated and some of the characteristics determined. The yield of starch ranged from 30.9 to 32.3% on a whole grain basis. The shape of the granule ranged from irregular to polygonal in shape with an average granule diameter of 7.0-7.8 mum within a range of 3.8-10.5 mum. Lipids were extracted by acid hydrolysis and by selective solvent extraction with chloroform-methanol 2:1 v/v (CM) at ambient temperature followed by n-propanol-water 3:1 v/v (PW) at 90-100 degreesC. The acid hydrolyzed extracts, which represented the total starch lipids ranged from 0.85 to 1.31%. The free lipids in the CM extract ranged from 0.05 to 0.09%, whereas the free and bound lipids in the PW extracts ranged from 0.75 to 1.18%. The total amylose content ranged from 10.60 to 24.50%, of which 9.02-18.91% was complexed by native starch lipids. The X-ray diffraction pattern was of the 'A' type. The relative crystallinity (RC) ranged from 28.0 to 36.5%. The starches differed widely in the degree of granular swelling, extent of amylose leaching, paste viscosity, gelatinization transition temperatures, gelatinization enthalpy, susceptibility towards acid hydrolysis, and retrogradation characteristics. The results showed that the above differences were influenced by variations in bound lipid content, RC and antylopectin branch chain length. (C) 2002 Elsevier Science Ltd. All rights reserved.
