Physicochemical Properties And Applications Of Starches From Four Different Legumes In Gan-Su Provice

The legumes which have the characters of high protein, starch, low fat were distributedwidely in northwestern China. However, as main compositions, the researches about starchare much more backward than protein and other starches, it's necessary to make furtherresearches on starch with the purpose of providing foundations and guidance for thedevelopment and utilization of legume resources.This paper used four kinds of common legumes—pea (Pisum sativum L.), coloredpea(Pisum sativum L.), small white kidney bean(Phaseolus vulgaris L.), Lathyrumhirsativa(Lathyrus sativus L.) produced in Gansu province as raw materials, extractedstarches from raw materials by wet-grinding method. The properties of starch granule andpaste were systematacially analyzed and compared with the control sample--corn, potato andmung bean starches, the influences on properties of kidney bean paste and gel by differentprocessing medias and its gel aging crystallization process were studied, modified starches oflegume and its properties were also studied, such as small kidney bean resistant starchprepared via autoclaving treatments with the addition of pullulanase and Lathyrum hirsativaoxidized starch made by wet method,H2O2as oxidant and CuSO4as catalyst.The result showed that Four kinds of legumes starch granules were all kidney-shaped.Their birefringence were obvious and mostly showed X-shape and cross-shape, but part ofstarch granule presented more obvious umbilical points. The average size of starch particleswere roughly within21²9μm, and Lathyrum hirsativa starch particles is largest, coloredpea is smallest, which is between potato starch and corn starch. The crystallization type ofgranule was C, similar with mung bean starch. The amylose content of the Starch particleswere higher than corn starch and potato starch and the order of content from much to litterwas colored pea starch, white bean starch, pea starch, Lathyrum hirsativa starch; The swellingcapability and solubility of legume starch displayed an increase at a higher temperature,belonging to restricted type expansion starch. The starting pasting temperature of four legumestarches ranged from72.2～79℃, the legume starches were more easily gelatinized than corestarch and had good thermal stability and cold paste stability; Compared with the controlsample, most of legume starch paste 's transparency was higher but not stable,and theirfreeze-thaw stability was poorer. The properties of these four legume starches are similar tomung bean starch, and the starches could tolerate heat treatment, but are unfit for productionof frozen foods. For the pocessing medias, different concentration of salt, sucrose, acid, alkaliwill have different effects on the viscosity property of small white kidney bean starch pasteand texture property of its gel.The higher starch concentration, the harder starch gel. And the gel made by small whitekidney bean starch had the highest hardness when store at4℃. With the ten days' texture analysis, we can approximatively get the aging model of small white kidney bean starch gellike θ=1-exp(-0.569t^0.4178)on the condition of solid-liquid ratio1:5, the storage temperature4℃. If we analysed in two phases, at the beginning (within16h), the aging of gel mainly dueto the crystallization of amylase, and the second phase (>16h,<8d),the hardness of gelmainly come from the crystallization of amylopectin.The optimum conditions for preparing the resistant starch:5%small white kidney beanstarch is entirely gelatinized, the dosage of pullulanase is6PUN/g, reacted16h, and storageat4℃2days. After treatment, the native small white kidney bean starch with smoothkidney-shaped surface appearance changed into irregular crystal with varying sizes. onlyautoclaving treatments, the granule has the lower crystallinity. With the pullulanase, thegranule diffraction peak appears razor-edge, crystal type is B, and more difficult to digest,could play an more important role in glucose slow-release.The optimum catalysis conditions for preparing the oxidized starch: dosage of H2O2is25mL/10g, reaction temperature55℃, time4.0h, and pH7.0. Compared with the Lathyrumhirsativa starch, oxidized starch granules suffered from remarkable damages, butbirefringence was also obvious,the solubility of oxidized starch displayed an increase at ahigher temperature and were higher than native starch at different temperatures,but theswelling capability did not change significantly and generally lower than the native starch,while the transparency of paste is much higher than the native starch.In a word, the properties of legume starch generally fell in between potato and cornstarch, their granule all had smooth surface and crystal type was C, part of them presentedmore obvious umbilical points, the amylose content of their starch particles were higher thancorn and potato starch. They belonged to restricted type expansion starch and had goodthermal stability and cold paste stability, their freeze-thaw stability was poorer, the aging oflegume starch gel was faster, so the starches could tolerate heat treatment and suitable for gelproducts, but are unfit for production of frozen foods. In addition, different treatments wouldbring particular physical and digestible properties, such as oxidized starch, especiallyresistant starch.