Morphological, physicochemical and textural properties of starch separated from Chinese water chestnut.

摘要

Chinese water chestnut starch (CWCS) was isolated and its composition, morphological, physicochemical and textural properties investigated. Chinese water chestnut starch granules were round, oval and polyangular in shape, with volumetric mean diameter (D50) 8.46 m. CWCS had an A-type crystal pattern and an apparent amylose content of 32.1%. Compared with tapioca and maize starch, CWCS exhibited moderate swelling power and turbidity and high stability against freeze-thaw treatment. Chinese water chestnut starch showed the highest peak (7957 mPa s), breakdown (4169 mPa s) and final viscosity (4816 mPa s), intermediate setback viscosity (1028 mPa s) and pasting temperature (68.7 degrees C), and lowest enthalpy (10.8 J/g) of gelatinization of the three starches studied. The effect of food additives (NaCl, sucrose and glycerol monostearate) and heating processes (direct heating, steam heating, microwave heating and autoclaving) on the CWCS gel was determined by a texture analyzer. The CWCS gel hardness and gumminess proportionally increased with the concentration of starch gels, ranging from 6% to 16%, but gel springiness and cohesiveness changed indistinctively. CWCS gels with added NaCl gave inconsistent results, but for the most part, they showed similar or increased gel hardness and gumminess as compared with the control. CWCS gels with added glycerol monostearate had lower gel hardness and gumminess than the control. The addition of sucrose (<15%, w/v) resulted in increased gel hardness and gumminess, but 20% sucrose decreased these features. Both microwave and steam heating on the one hand and autoclaving and directly heating on the other gave rise to similar gel hardness and gumminess, the values of the two groups being significantly different from each other.