| Adlay (with the latin name of Semen Coicis, with other names of Coix Seed、Job’s tears seed) has been recognized as a treasure of dietetic therapy with its nutrition and health care. The conten of starch in the adlay is about53.5%. Adlay starch falls into the category of granular starches with values of production and application.This article was started by the screening of extraction methods based on the raw material of adlay, and the final method was the way of alkaline assisted with ultrasonic wave, then the extraction methods were optimized and the protein residual adsorption was redused by the method of using papain. Secondly, the physical and chemical properties of purified adlay starch were analysed by different modern instruments on such factors as granular structure、state of crystallization and thermodynamics. The contents of amylose and amylopectin were also determined, then the separation of two starches was made and the degree of branching of amylopecin was determined. The comparison of gelatinization to two sarches such as maize starch and sticky rice starch which were choosed to explore the application of adlay starch. Thirdly, the modification of adlay starch was also studied by the enzymic method to produce micro-porous starch. Then the establishment of adlay micro-porous starch was studied by the modern instruments on such factors as granular structure、state of crystallization and thermodynamics.The adlay starch was extracted from adlay by the way of alkaline and ultrasonic wave, the purification of adlay starch was followed by the enzymic method. Combined with the response surface analysis, the optimum conditions of adlay starch extraction were discussed. The optimum conditions were:ratio of solid to liquid l:10、mass fraction of NaOH0.39%soaking temperature of NaOH32℃、soaking time of NaOH8.5h、power of ultrasonic wave60W、temperature of ultrasonic wave30℃、application time of ultrasonic wave27min. Under the conditions of papain addition, the protein residual adsorption was effectively reduced. The optimum process conditions were: ratio of solid to liquid1:5、papain addition20000U·kg-1enzymolysis temperature of papain55℃, pH’5.5, enzymolysis time of papain2.5h.The protein residual adsorption in the adlay starch was reduced to about0.5%, the starch yield was49.14%, and the starch extracting yield was91.82%.The content of amylose was5.584%by the standard curve of amylase. The degree value of polymerization of adlay starch was224.8, the degree of branching was1.538:1. The granular appearance of adlay starch was mainly multi-prismatic with a smooth surface by FESEM. The analysis of granularity of adlay starch showed that the granular size was3-14μm, with the average value of10.063μm, and the specific area was0.596m2/g. Adlay starch had A type of crystal. There were higher temperatures through the period of gelatinization by the table of DSC, the first gelatinization temperature of adlay was67.3℃, the peak temperature was73.7℃, the final gelatinization temperature was88.2℃, ΔH was15.2J/g. The first gelatinization temperature of adlay starch was67.3℃, which was between maize starch and sticky rice starch by BU values. It showed that it was high viscosity starch paste and it also had fine cool viscosity stability and bad thermal viscosity stability. All gelatinization values of adlay starch were between maize starch and sticky rice starch. The average value of transmittance was22.44%, it was unsuited to make freezing food because it had a normal freeze thawing stability. There was a good retrogradation for thickening. It had a bigger solubility and a smaller swelling degree. The ageing resistance and shearing resistance were good.The preparation of micro porous starch was made by a-amylase and saccharifying enzyme. And the optimum composition was the enzymolysis temperature of55℃, enzymolysis time of20h, enzymolysis pH of4.2, the dose of complexed enzymes of2.0%, at the same time, the hydrolysis ratio was47.68%and the oil-absorption was77.6%。 There were much difference between adlay starch and adlay micro-porous starch on the results of FESEM. The granular form was still mainly multi-prismatic, but the granular appearance was changed from smooth surface to besprinkled evenly with not of uniform size of micropore, and the porosity was about45%, the aperture of the micropore was from200nm to600nm.This different micropores had different depth into the granular inside showed that it was out of sync by the enzymolysis.The granular size was3～10μm, with the average value of9.614μm. Through the comparison of results of XRD, the20values and the degree of crystallinity were raised. There were higher To and lower Tc through the period of gelatinization by the data of DSC, which showed that the uniform of crystalline region and non-crystalline region had been raised and the enzymolisis was mainly happened in the non-crystalline region. The amylose content had a trend of increased firstly and then decreased, which also showed that the enzymolisis was mainly happened in the non-crystalline region. |
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