Effect of freeze-thawing treatment on the structural and physicochemical characteristics of starch isolated from Chinese yam

Freeze-thaw (F/T) is an effective physical method for modifying starch, improving its structures and physicochemical properties. This study investigated the effects of varying F/T cycles on the fine structure (molecular chain, short-range order, crystal, and particle structures) and physicochemical properties (solubility, swelling power, pasting and thermal properties, and digestibility) of Chinese yam starch (NCYS). The modified starches showed reduced amylose (19.11%–20.08%) and A chain content (9.71%–10.69%), while B3 chain content increased (49.07%–54.90%). Compared to NCYS, the modified starches exhibited a weaker short-range ordered structure, higher double helix content (58.76%–59.83%), and increased crystallinity (43.52%–46.98%). The modified starches showed higher pasting temperature (86.9–87.2 °C), lower breakdown viscosity (1432–1564 cP), and higher setback viscosity (1840–2033.5 cP) compared to NCYS. Additionally, the modified starches had higher T o (76.45–76.64 °C) and △H (9.93–10.92 J/g) than the native starch. Morphological analysis revealed surface roughening and loss of granule integrity. Enhanced anti-digestion properties were observed, with a reduction in rapidly digestible starch (1.49%–3.00%) and an increase in resistant starch (94.41%–96.76%). This study provides insights into the modifications of Chinese yam starch through F/T treatment, highlighting its promising applications in functional food development. • Freeze-thaw treatment enhances molecular structure of Chinese yam starch. • Modified starches show improved thermal stability and gel texture. • Rapidly digestible starch decreases while resistant starch increases after treatment. • Freeze-thaw treatment of Chinese yam starch suggests potential for functional food development.