| Castanopcis Sclerophylla starch(CaS),as a kind of new starch resource in Jiangxi Province,is non-polluting,unique taste and rich in nutritious.However,the properties associated with the products of CaS are still unclear,especially the retrogradation and in vitro digestibility of CaS,which restricted the development and utilization of Castanopcis Sclerophylla resource.Therefore,the main research contents are as follows:(1)physicochemical and in vitro digestibility properties of nature CaS;(2)retrogradation behavior and in vitro digestibility of retrograded CaS;(3)the effect of annealing treatment on the physicochemical properties and in vitro digestibility of CaS.The micro-structure of CaS granules are irregular spherical shape,with small particle size and C type crystal.The content of amylose is 31.11%,which was higher than that of other fagaceae fruit starches reported in the literature.The results of starch thermodynamics and rheological indicated that CaS has the higher setback value and lower gelatinization temperature compare with common corn starch(CS);CaS paste exhibited anti-thixotropy under the condition of external shearing,and new structural system can be formed in a short time to resist shearing;the G''and G'values of CaS determined by frequency scanning were significantly higher than those of CS,indicating that CaS gel had better viscoelasticity and stronger gel network structure.In addition,CaS paste was more likely to form gel with the largest gel strength compare with CS paste.The in vitro digestibility of native starches showed that CaS had the higher SDS content and GI value than those of CS.The short-term and long-term retrogradation behavior of CaS was analyzed by using rheometer,texture profile analysis(TPA),differential scanning calorimeter(DSC)and X-ray diffractometer(XRD).During dynamic time scanning for 4 h,the CaS paste always has higher G'values and lower tan?values than those of CS,which indicated that leached-out amylose from CaS granules were aggregation rapidly.During 14 days'storage,the hardness of CaS gels was increased with increasing storage time,whereas cohesiveness was decreased.The high degrees syneresis and poor refrigeration stability was found in CaS gel during refrigeration.With the extension of storage time,the retrogradation enthalpy(?H)of starch samples showed gradual increase.The CaS exhibited obviously higher crystallization rate constant(k)value of 0.81 than that of CS,which further proved that the CaS was more easily to retrogradated.The in vitro digestibility of retrograded starch showed that the aging has remarkably influence on the digestibility of CaS,along with the decrease in RSD content,k value and GI value,great increase in RS content.The effect of annealing treatment(ANN)on the physicochemical properties and in vitro digestibility characteristics of CaS were also investigated.The results show that ANN significantly decreased the setback value,swelling power and solubility and increased the gelatinization temperature of starch.The ANN has remarkable influence on gelatinisation characteristics of starch,showing an increase in T_o,T_c,T_p,decrease in the gelatinisation range(T_c-T_o),but either no change in gelatinisation enthalpy.After annealing,both the sample consistency coefficient and the fluid index decreased;the fluid index n of all starch pastes were less than 1,which indicated that they were typical pseudoplastic fluids.Compared with the native CaS,ANN treatment increased the crystallinity and had no significant effect on the digestibility of starch.By comparing the effects of one-step ANN and two-step ANN on physicochemical properties of CaS,it was found that the influence of two-step ANN on properties of CaS was due to the prolongation of ANN time rather than the increase in the times of ANN.This research provides a theoretical basis for the development and quality control of CaS products and promotes the development and utilization of CaS as a natural-green functional food resource. |
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