The effect of heat-moisture treatment on the structure and physicochemical properties of legume starches

Manuel, Heather J. (1996) The effect of heat-moisture treatment on the structure and physicochemical properties of legume starches. Masters thesis, Memorial University of Newfoundland.

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Abstract

Native Green Arrow pea, Eston lentil, Othello pinto bean, black bean and Express field pea starches were heat treated at 100°C for 16h at a moisture content of 30%. The heat treatment did not change granule size or shape. The surfaces of Green Arrow pea and Eston lentil starches were modified after heat treatment. Heat treatment decreased amylose leaching (Green Arrow pea>Express field~Eston Ientil>black bean~pinto bean) and the swelling factor (Eston lentil~Express field pea>Green Arrow pea>black bean~pinto bean). The X-ray diffraction intensities increased in Green Arrow pea starch, but decreased in the other starches (Express field pea>black bean>pinto bean>Eston lentil). However, the X-ray pattern of all starches remained unchanged after heat treatment. Differential scanning calorimetry of the heat treated samples showed broadening of the gelatinization temperature range and a shifting of the endothermal transition towards a higher temperature (Eston lentil~Express field pea>black bean~pinto bean). However, the gelatinization enthalpy (ΔH) of all starches remained unchanged. The susceptibility towards hydrolysis by porcine pancreatic α-amylase increased on heat treatment (black bean>Eston Ientil>Express field pea>pinto bean>Green Arrow pea). The action of α-amylase on the starches decreased ΔH in Eston lentil and Express field pea starches. However, ΔH decreased only marginally in pinto bean and black bean starches. Acid hydrolysis (2.2N HCl) increased on heat treatment (black bean>Express field pea~Eston lentil~pinto bean>Green Arrow pea). The results showed that bonding forces within the amorphous regions of the granule, crystallite orientation and the granule surface (in Green Arrow pea and Eston lentil) are altered during heat treatment. The magnitude of these changes being dependent upon the starch source.

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