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<p>Crosslinking is widely employed to improve structural stability and functionality of starch-based systems. Purified starch modifications are commonly reported. Reports on modification of starchy flours are scarce. This study investigated the effects of variable (3–12%) sodium trimetaphosphate (STMP) crosslinking on the physicochemical, structural, thermal, rheological, digestive and bioactive properties of three pigmented <i>bao</i> rice flours, conferred by their starch as well as non-starch components. <i>Bao</i> is a group of submergence tolerant, flood-resistant rice types bearing economic significance. Infrared spectroscopy suggested successful crosslinking. Residual phosphorus content increased significantly (<i>p</i> &lt; 0.05) from 0.011 to 0.015% in native flours to 0.063–0.079% in the 12% crosslinked samples. Quantifiable amylose decreased by 17.9%-18.1%. Progressive granule aggregation and densification were observed under scanning electron microscope. Swelling power reduced from 2.43 to 2.67 to 1.92–2.18&#xa0;g/g and solubility from 2.17 to 2.67 to 0.34–0.67%. Peak viscosity of cooked gels ranged from 2880 to 3920 cP in native flours to 3860–4550 cP at 9% STMP. This was supported by increase in gelatinization temperatures and an overall decrease in gelatinization enthalpy. Reduced syneresis from native gels (15.1–18.9%) to 9% STMP (9.0–12.0%) were evidenced. Gel strengthening was also supported by rheometry. Increase in storage modulus coefficients (K′) from native gels (3.55–4.70&#xa0;Pa) to 9% crosslinking level (5.38–7.21&#xa0;Pa) were recorded. Additionally, enhanced retrograded hardness, apparent viscosity, consistency index, yield stress, and storage modulus (G′ &gt; G″; tan δ &lt; 1) indicated strong elastic gel formation. Digestibility shifted from rapidly digestible starch to increased slowly digestible and resistant fractions. Resistant starch increased from 8.8 to 9.0% in native flours to 23.4–30.0%. Antioxidant activity (DPPH radical scavenging) declined significantly from 84.9 to 87.3% to 8.9–10.4%. Overall, different levels of STMP crosslinking imparted distinct functional attributes, with 9% producing the most favorable balance of functional and rheological properties.</p>

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STMP Crosslinking of Pigmented Whole Bao Rice Flours: Effects on Structural, Rheological, Digestive, Bioactive and Gel-Forming Properties

  • 期刊论文

  • 发表日期：

    2026年7月22日

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  • Gunjana Deka,
  • Sayantan Chakraborty,
  • Ishita Chakraborty,
  • Nirmal Mazumder,
  • Sib Sankar Mal,
  • Manash Pratim Sarma,
  • Himjyoti Dutta

摘要

Crosslinking is widely employed to improve structural stability and functionality of starch-based systems. Purified starch modifications are commonly reported. Reports on modification of starchy flours are scarce. This study investigated the effects of variable (3–12%) sodium trimetaphosphate (STMP) crosslinking on the physicochemical, structural, thermal, rheological, digestive and bioactive properties of three pigmented bao rice flours, conferred by their starch as well as non-starch components. Bao is a group of submergence tolerant, flood-resistant rice types bearing economic significance. Infrared spectroscopy suggested successful crosslinking. Residual phosphorus content increased significantly (p < 0.05) from 0.011 to 0.015% in native flours to 0.063–0.079% in the 12% crosslinked samples. Quantifiable amylose decreased by 17.9%-18.1%. Progressive granule aggregation and densification were observed under scanning electron microscope. Swelling power reduced from 2.43 to 2.67 to 1.92–2.18 g/g and solubility from 2.17 to 2.67 to 0.34–0.67%. Peak viscosity of cooked gels ranged from 2880 to 3920 cP in native flours to 3860–4550 cP at 9% STMP. This was supported by increase in gelatinization temperatures and an overall decrease in gelatinization enthalpy. Reduced syneresis from native gels (15.1–18.9%) to 9% STMP (9.0–12.0%) were evidenced. Gel strengthening was also supported by rheometry. Increase in storage modulus coefficients (K′) from native gels (3.55–4.70 Pa) to 9% crosslinking level (5.38–7.21 Pa) were recorded. Additionally, enhanced retrograded hardness, apparent viscosity, consistency index, yield stress, and storage modulus (G′ > G″; tan δ < 1) indicated strong elastic gel formation. Digestibility shifted from rapidly digestible starch to increased slowly digestible and resistant fractions. Resistant starch increased from 8.8 to 9.0% in native flours to 23.4–30.0%. Antioxidant activity (DPPH radical scavenging) declined significantly from 84.9 to 87.3% to 8.9–10.4%. Overall, different levels of STMP crosslinking imparted distinct functional attributes, with 9% producing the most favorable balance of functional and rheological properties.