Study On Properties Of Physicochemistry And Gelatinization Of Chestnut Starches From Anhui

In this paper, the composition, granule sizes, crystalloid, thermoproperties and processing of chestnut starch from Dahongpao and Mifengqiu chestnut of Anhui were studied by spectrophotometer, electric potential titrator, optical microscopy, X-ray diffraction, differential scanning calorimetry (DSC) and Ubbelohde viscometer, etc. The aim of this investigation would provide theory and technology for chestnut starch further developed. The results were as fellows:1 Potentiometric titration method was better than iodine colorimetry by the determination of the amylose content of chestnut starch. The result showed the amylose content of Dahongpao chestnut and Mifengqiu chestnut were 16.64% and 13.03%, respectively.2 The granule morphology of chestnut starches were analyzed by light microscopy. The result indicated that all granules of chestnut starches included oval, circle, and triangle. The gelatinization degree of chestnut starches increaced gradually with water content increaseed, and most of granules were swollen and broken when water content was more than 70%. The temperature and heating time could promote the swelling and break of starch granules, however, temperature compared with time had more effect on the granule morphological changes; higher alkalinity had stronger effect on the swelling of granules than neutral and acid condition under nomal temperature. Most of starch granules were swollen when pH value reached 13. Compared with Dahongpao, Mifengqiu was swollen easily under the same conditions. The swell test showed that the temperature and time of treatment were prolonged, power, solubility, supernatant and BV of chestnut starches increased, but the values of Mifengqiu were more than those of Dahongpao. However, the precipitation decreased, the value of Mifengqiu was less than that of Dahongpao.3 X-ray diffraction analysis indicated that both chestnut starch granules were belong to C-type crystal. The diffraction intensity of Dahongpao starch was stronger than that of Mifengqiu. When the starch paste with 30-70% water was heated at 100℃for 5 minutes, the starch was not completely gelatinized, X-diffraction showed that inter-granules exsited crystal structure. The starch was gelatinized completely when the water more than 80%, crystal structure disappear completely. The effect of water on subcrystal in pregelatinized starch was significant, the subcrystal degree increased at first and then decreased with water increased if the tempeture was not change. The peak area and crystal degree of diffraction of Mifengqiu starch were more than those of Dahongpao under the same condition.4 Gelatinization temperatures of Dahongpao starch and Mifengqiu starch were respectively 60.37℃,58.79℃after determined by DSC. The gelatinized temperature of Dahongpao starch was higher than that of Mifengqiu. Under 67% moisture,both Tg of chestnut starches were about 79℃; Under the moisture content of 15%, Tg of both starches increased, which were 88℃and 84℃, respectively.5 For both chestnut starche pastes, the transparency, and stability of freeze-thaw were better, and the coagulation was stronger. The transparency of chestnut starches were better than that of corn starch, but were worse than those of potato starch and Pueraria lobate starch; the freeze-thaw stability of chestnut starches were better than those of potato starch and Pueraria lobate starch, but not better than potato starch, and the coagulation of both chestnut starch pastes was more stronger on compared with others starch pastes. The transparency and freeze-thaw stability of Mifengqiu chestnut starch were better than those of Dahongpao, however, the coagulated curves of them were consistent, both the sediment volume reached 16 mL after rest.6 Intrinsic viscosity and rheological properties of the starches were studied by using Ubbelohde viscometer and digital viscometer. The results show chestnut starch was typic pseudoplastic fluid. Viscosity of the starch paste increased as the increasing of concentration and heating tempreture, while decreased as the increasing of shear rate. And it increased under strong acid and alkali.Viscosity of Dahongpao chestnut starch paste was higher than that of Mifengqiu.