| Lotus root(Nelumbo nucifera Gairtn)is a kind of aquatic vegetable used both as medicine and food.Lotus root have high nutritional value,and its main component is starch.China is rich in lotus root resources,exhibit numerous varieties with different quality.In this paper,nine representative lotus roots were selected as experimental materials.Secondly,the starch characteristics and textures of different varieties of lotus root were analyzed and compared by optical microscopy,scanning electron microscopy,fourier transform infrared spectrometer,X-ray powder diffractometry,solid nuclear magnetism,differential scanning calorimetry.Finally,nine varieties of lotus root were processed,and the changes of texture,starch particle morphology,starch structure characteristics and starch thermal characteristics of different varieties of lotus root after boiling,frying and microwave were analyzed.The main research results are as follows:(1)Analysis of crisp and silty lotus root qualityIn this study,nine varieties(Suining white lotus root,Xinhe,Zaohua,Zhonghua,L0014,L0013,Cuiyu,L0011,Zhenzhu)of lotus root were taken as the research object.The differences in appearance,texture and nutrition of nine varieties of lotus root were compared.The results showed that pearl,Xinhe,L0013,crisp jade and Zhonghua lotus root were belonged to the crispy lotus root,their lotus root joints were round and full,the color were reddish,had high moisture,VC content,high sugar-acid ratio,crisp texture and sweet taste.L0011,L0014,Early flower,Suining white lotus root were belonged to the silty lotus root,which expressed hard texture,high viscosity,high starch,polyphenols,protein content,taste powder waxy and high nutritional value.(2)The characteristics of crisp and powdered lotus root starch.The starch properties of nine varieties of lotus root were studied by optical microscope,polarizing microscope,scanning electron microscope,weak total reflection fourier transform infrared spectroscopy,X-ray diffraction,solid state nuclear magnetic resonance,differential scanning calorimeter and texture analyzer.The starch granules of nine varieties of lotus root were elongated elliptic,and the particle size was in the range of 40～60μm.Starch granule of silty lotus root was obviously higher than that of crispy lotus root.The results of ATR-FTIR showed that the outer region of starch granules of nine vatieties of lotus root had highly ordered structure.Starch from eight varieties of lotus root belong to crystal A(Suining white,Xinhe,Zaohua,Zhonghua,L0014,L0013,Cuiyu,L0011),and Zhenzhu lotus root starch belong to CA crystal type through X-ray diffraction and nuclear magnetic resonance study.The crystallinity of silty lotus root were higher than crispy lotus roots,and also the gelatinization temperature,gelatinization enthalpy,expansion force,adhesiveness of starch,and their crystal structure were relatively perfect.The hardness and chewability of starch gel of crispy lotus root were obviously higher than that of silty lotus root.(3)Changes of texture and starch characteristics of nine varieties of lotus root after different processing methodsThe texture and starch characteristics of lotus root were determined after boiling,frying and microwave.The texture and masticability of lotus root were improved after frying and microwave.The starch granules of lotus root were destroyed in different degrees by hot processing,boiling>frying>microwave.The short-range order degree,crystallinity degree,gelatinization temperature and gelatinization enthalpy of starch of lotus root decreased after boiling and frying.Starch granules of silty lotus root had good heat resistance and stability.The short-range order degree,crystallinity degree,gelatinization temperature and gelatinization enthalpy of starch of nine varieties of lotus root increased in different degrees after microwave,and the heat resistance and stability of starch granules of crispy lotus root were improved under microwave. |
