Effects of Tremella fuciformis Mushroom Polysaccharides on Structure, Pasting, and Thermal Properties of Chinese Chestnuts (Castanea henryi) Starch Granules under Different Freeze-Thaw Cycles

The purpose of this study was to investigate the effect of Tremella fuciformis polysaccharides on the physicochemical properties of freeze-thawed cone chestnut starch. Various aspects, including water content, crystallinity, particle size, gelatinization, retrogradation, thermal properties, rheological properties, and texture, were examined. The results revealed that moderate freezing and thawing processes increased the retrogradation of starch; particle size, viscosity, shear type, hinning degree, and hardness decreased. After adding Tremella fuciformis polysaccharide, the particle size, relative crystallinity, and gelatinization temperature decreased, which showed solid characteristics. Consequently, the inclusion of Tremella fuciformis polysaccharide effectively countered dehydration caused by freezing and thawing, reduced viscosity, and prevented the retrogradation of frozen-thawed chestnut starch. Moreover, Tremella fuciformis polysaccharide played a significant role in enhancing the stability of the frozen-thawed chestnut starch. These findings highlight the potential benefits of incorporating Tremella fuciformis polysaccharides in starch-based products subjected to freeze-thaw cycles.

Physicochemical and retrogradation properties of modified chestnut starches

Physicochemical properties of acetylated (AC), cross-linked (CL), and hydroxypropylated (HP) chestnut starches were investigated. Modified chestnut starch showed low RS and amylose contents. AC revealed the highest solubility and HP showed the highest swelling power at 60 °C. CL showed the lowest solubility and swelling power at both 60 and 90 °C. AC and HP showed a lower pasting temperature and higher peak viscosity than native chestnut starch (NC). Modified chestnut starch formed gels at higher solid content than NC. CL had the lowest freeze-thaw stability, and AC and HP showed the strongest tolerance to freeze-thaw cycles. Amylopectin melting enthalpy of NC dramatically increased over the first 2 days and continued increasing gradually until day 24. On the other hand, all the modified chestnut starches showed a slight increase in amylopectin melting enthalpy, indicating retarded retrogradation. CL showed the lowest degree of retrogradation, followed by HP, AC, and NC.

Comparison of Physicochemical Properties of Starches from Nine Chinese Chestnut Varieties

Chestnut is a popular food in many countries and is also an important starch source. In previous studies, physicochemical properties of starches have been compared among different Chinese chestnut varieties growing under different conditions. In this study, nine Chinese chestnut varieties from the same farm were investigated for starch physicochemical properties to exclude the effects of growing conditions. The dry kernels had starch contents from 42.7 to 49.3%. Starches from different varieties had similar morphologies and exhibited round, oval, ellipsoidal, and polygonal shapes with a central hilum and smooth surface. Starch had bimodal size distribution and the volume-weighted mean diameter ranged from 7.2 to 8.2 μm among nine varieties. The starches had apparent amylose contents from 23.8 to 27.3% but exhibited the same C-type crystalline structure and similar relative crystallinity, ordered degree, and lamellar structure. The gelatinization onset, peak, and conclusion temperatures ranged from 60.4 to 63.9 °C, from 64.8 to 68.3 °C, and from 70.5 to 74.5 °C, respectively, among nine starches; and the peak, hot, breakdown, final, and setback viscosities ranged from 5524 to 6505 mPa s, from 3042 to 3616 mPa s, from 2205 to 2954 mPa s, from 4378 to 4942 mPa s, and from 1326 to 1788 mPa s, respectively. The rapidly digestible starch, slowly digestible starch, and resistant starch ranged from 2.6 to 3.7%, from 5.7 to 12.7%, and from 84.4 to 90.7%, respectively, for native starch, and from 79.6 to 89.5%, from 1.3 to 3.8%, and from 7.1 to 17.4%, respectively, for gelatinized starch.

Retrogradation kinetics of chestnut starches cultivated in three regions of Korea

Retrogradation kinetics of chestnut starches from three different regions of Korea were investigated during storage at 4 °C. The retrogradation properties were determined using four DSC characteristics: glass transition temperature ( T g ' ), ice melting enthalpy (ΔH_i), amylopectin melting enthalpy (∆H_r) and degree of retrogradation (DR). The Gongju (GJ) starch showed the highest gelatinization enthalpy (∆H_g) value, followed by Gwangyang (GY) and Hadong (HD). T g ' of all samples gradually increased with increasing storage time, while ∆H_i decreased as the storage time increased. ∆H_r of all samples significantly increased after 2 days of storage. DR, calculated based on ∆H_g and ∆H_r, showed a similar tendency with ∆H_r. The retrogradation rates of three chestnut starches were analyzed using the Avrami equation, and the time constants (1/k) were obtained. GY, GJ and HD showed the fastest retrogradation rate in T g ' , ∆H_i, and ∆H_r, respectively suggesting that each sample experienced different retrogradation kinetics in different region.