Study On Physicochemical Properties And Modification Of Tigernut Starch

Tigernut（Cyperus esculentus）,as a new crop,has been planted more and more widely in China,but at present,most of the studies on it focus on its cultivation techniques,oil extraction and nutrition analysis,while there are relatively few studies on its starch.In this study,with tigernut tube starch（TTS）as the research object,its physicochemical properties and effect on the quality of steamed bread were studied systematically.The effects of citric acid esterification on the digestion,physicochemical and functional properties of TTS were investigated,and the Pickering emulsion was constructed with the esterified tigernut starch with citric acid（ETSC）as emulsifier,and the microstructure and microrheological properties of the emulsion were also characterized.Finally,the cross-linked tigernut starch with sodium trimetaphosphate（CLTS）was prepared,and its physicochemical properties,microstructure and functional properties were studied.The obtained results can provide theoretical support for the study of tigernut starch,and prompt the application of tigernut starch.The main research conte TTS and related conclusions of this study are as follows:（1）The preparation,composition,granule morphology,crystal structure,pasting properties,functional properties,and gel properties of tigernut tuber starch（TTS）were systematically investigated.Its application in steamed bread production was also evaluated.It was found that TTS granules were spherical and oval with an average size of 18.53?±?0.61?μm.Although its amylose content and crystallinity were close to corn starch,it belonged to C-type starch.The final viscosity and setback viscosity of TTS were significantly superior to those of corn starch and potato starch,indicating its strong retrogradation tendency.The excellent freeze-thaw stability of TTS was also observed,which might be related to its outstanding gel properties.Although the addition of TTS reduced the color and volume of steamed bread,it could significantly enhance the chewiness and crumb structure of steamed bread when the addition amount was appropriate.（2）Citric acid esterified tigernut starch（ETSC）was prepared,and its structure,in vitro digestibility and Pickering emulsification ability were investigated.The formation of ETSC was confirmed by SEM（scanning electron microscopy）,XRD（X-ray diffraction）,FT-IR（Fourier transform infrared spectroscopy）and solid-state ¹³C-NMR（nuclear magnetic resonance）.The amount of citric acid in the preparation process was positively correlated with the degree of substitution（DS）of ETSC.With the increase of DS,the solubility and swelling power of ETSC decreased,the crystallinity decreased,and the proportion of resistant starch（RS）increased rapidly.The increase in DS could also improve the wettability of ETSC,thus increasing the Pickering emulsification capacity of ETSC.Higher ETSC concentration（c）and appropriate oil phase volume ratio（φ）were beneficial to the formation and stability of Pickering emulsion.In addition,the macroscopic viscosity index（MVI）and elastic index（EI）of emulsion were also positively correlated with the DS of ETSC.（3）Cross-linked tigernut starch（CLTS）was prepared with sodium trimetaphosphate as crosslinking agent.The effect of cross-linking on the structure and physicochemical properties of TTS bean was studied.FT-IR analysis confirmed the formation of CLTS.X-ray diffraction（XRD）results showed that cross-linking not only preserved the crystalline form（C type）of starch,but also enhanced the crystallinity.Compared with TTS,CLTS had lower solubility and swelling capacity,better aging resistance and freeze-thaw stability,and was easier to settle.The pasting temperature and peak viscosity of CLTS were better than that of TTS.It was easier to regenerate at low temperature,and the thermal stability was also significantly improved.