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Food Structure

Abstract

The effect of heat treatment on the gel formation and microstructure of barley starch dispersions , hydrolyzed with I M HCI for 0.5, 1.0 and 4.0 hours , was studied by dynamic viscoelastic methods and by light microscopy . The effects of acid hydrolysis on the molecular weight of amylopectin and amylose were studied by high -performance liquid chromatography (HPLC) with post-column iodine staining.

Microstructural studies of 8% hydrolyzed barley starch dispersions heated to 90 0 C showed that even a short acid treatment induced considerable changes in the granule structure. The molecular weight of amylopectin decreased substantially. As the hydrolysis progressed , the gel network composed of both amylose and amylopectin and separation into amylopectin-rich and amyloserich domains took place. The gel formation of amylose weakened with increased hydrolysis time if heating was to 90 °C, mainly because the amount of amylopectin in the continuous phase increased.

Increasing the temperature from 90 to 98 °C induced dramatic changes in the structure of hydrolyzed starch pastes: most of the granules disintegrated . When the hydrolysis time was 0 .5- 1.0 hour, the starch paste assumed a phase-separated structure. The gels formed from the most extensively hydrolyzed barley starch sample had a dense network structure, with high storage modulus and low phase angle.

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