Effect of heat-moisture and acid treatment on physicochemical, pasting, thermal and morphological properties of Horse Chestnut (Aesculus indica) starch

• Untreated Horse Chestnut starch was modified by heat-moisture and acid treatments.
• The crystalline structure displayed a similar C-type profile for all the starches.
• Modification changed the pasting profile of native HCN starch.
• Morphology of starch granules was affected at higher levels of modification.
• Less setback viscosity makes modified starch suitable for use in frozen foods.

The present work was carried out to study the effect of heat-moisture and acid modification on the structural, physicochemical, pasting, gel texture, morphological and thermal properties of Indian Horse Chestnut (HCN) starch. Starch isolated from seeds of HCN was subjected to heat moisture treatment (HMT) at 20% (HMT-20), 25% (HMT-25) and 30% (HMT-30) moisture levels and acid treatment (AT) with hydrochloric acid (HCl) at three different concentrations of 0.25M (AT-1), 0.5M (AT-2) and 1M (AT-3), respectively. XRD results showed a similar X-ray pattern with increased relative crystallinity in acid modification and decreased crystallinity in heat-moisture treatment. The IR-spectra also showed a similar pattern in both the modifications with increase in intensities of the band at 1016 cm−1 in heat moisture treatment and decreased intensities of the band in acid treatment. HMT showed negligible effect on amylose content while acid treatment significantly decreased the amylose content. Both the modifications significantly decreased the swelling power of the starch. Moreover, the solubility of HMT was decreased and in acid was increased. HMT resulted in increased water binding and oil binding capacity while reverse was found in acid treatment. Pasting characteristics of native starch were largely affected by both the treatments with a significant reduction in peak viscosity. Moreover, the HMT showed no breakdown in the treatments with higher moisture content. The gel firmness of the starch was increased in heat moisture and decreased in acid treatment. HMT of native HCN starch at higher levels caused few dents or cracks on the granule surface while acid treated starch showed rough surface with cracks and cavities, respectively. DSC revealed that both the treatments increased the gelatinisation temperature with reduced gelatinisation enthalpy (ΔH) in heat moisture treated starch while increased ΔH of acid modified starch.

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