Fragmentation of oat and barley starch granules during heating

The structural differences between oat and barley starches were investigated by analysing starch polymers released from the granules and the granule residues during heating. When the temperature was increased from 85 to 97 °C the amount of leached carbohydrates increased from 6·1–8·7% to 36·1–37·4%. Concurrently, the lysophospholipid content of the granule residues decreased from 0·87–1·0% to 0·35–0·46%, indicating that lysophospholipids were also present in the solubilised fraction. Oat and barley starch dispersions preheated to 95 °C were further fractionated by sequential centrifugation. After the first centrifugation of both starches, 68–70% of the carbohydrate in the supernatant was amylose. After recentrifugation, an insoluble fraction with a high amylose to lipid ratio was obtained. Oat and barley starches showed similar fractionation behaviour, but the molecular weight of the solubilised oat starch was somewhat higher.