Research And Application Of Yam Starch Quality Characteristics

As a major component of yam, starch has an important impact on the processing characteristics and nutritional quality. The author systematically analyzed the main component in the yam and observed granule characteristics such as the surface structure, particle size, and crystal structure. Starch fractions, the processing quality and gelatinized dynamics were further studied in this paper.Yam starch granule is mainly characterized as ellipsoidal or circular, whose surface would be adhered by some polysaccharide if the extraction was not completed. The particle size map showed that the average particle size of yam starch was 332.8 μm. The crystal structure of yam starch was pattern C according to XRD results. The amylose content in yam starch was 19.49% detected by capillary electrophoresis.To optimize extract process, this paper concluded the best conditions of extracting the amylose and amylopectin by univariate and orthogonal experiments as followings:alkali concentration was 0.5 mol/L, bath time was 20 min, volume ratio of n-butanol/isoamylol was 4:1, extract times were five times.According to the analysis, the blue value of amylose and iodine complex was 0.968 while that of amylopectin and iodine complex was 0.176; both are within the effective range. With the aid of high performance liquid chromatography, the molecular weight of amylopectin was about 60 thousand, and the chain length and degree of branching of amylopectin was 23 and 2.39 respectively. After purification and enzymolysis by isoamylase, amylopectin can be divided into three parts through gel-chromatography. The IR and NMR spectra showed that amylopectin was a polymer linked with a-glycoside bonds.Yam starch processing quality were studied at the same time, including solubility, swelling power, transparency, retro gradation properties, gel strength of starch paste, pasting temperature and so on. The study found that the solubility, the swelling power and the transparency of yam starch was 16.78%,33.55% and 23.2% respectively in 95 ℃. The retro gradation of yam starch paste would become stable after six hours in whether neutral, weak acid or weak base conditions. The water separated from starch paste was 48.2%. Yam starch had poor freeze -thaw stability under this condition. The gel strength of yam starch was 89.9 g. Pasting temperature of yam starch started from 60.4 ℃ and ended at 83.2 ℃ according to DSC results. At last, the pasting dynamics of yam starch was studied in this paper. The author concluded that the pasting procedure of yam starch was classified as the first-class pasting...