| In this paper water-extractable arabinoxylans (WE-AX) was fractionated from flour offour high-quality wheat varieties in Henan Province, and their extraction methods, basicstructure and effects on dough properties and Chinese mantou quality were studied.Fistly, the extracting conditions was optimized by single-factor experiments andResponse Surface Methodology. The results showed that the extraction conditions wereobtained as follows: extraction temperature46℃, extraction time103min, the ratio of waterto material1:9, and yield is0.689%.Proteins in the processing of extract were eliminated using two different methods,diatomite’s method and enzymolysis’s method respectively, and the effects were compared.The results showed that diatomite’s method was timesaving and simple to operate but had alow removal rate of protein, while enzymolysis’s method exhibited higher removal rate ofprotein but spend more time and power. The optimum conditions of enzymolysis’s methodwas confirmed using orthogonal test: adding0.06%(W/V) concentration of neutral proteasefor4h at50℃, and the removal rate of protein reached76.20%. The remove of protein in thewhole extract process was also investigated, and99.7%of protein was removed.The monosaccharide composition of WE-AX was determined by high performanceionexchange chromatography, The degree of branching (arabinose/xylose ratio) of WE-AXfrom different wheat varieties ranged between0.63and0.84, and the fractions precipitated byincreasing ethanol precipitation concentration also had varying A/X ratios, which ranged from0.50to1.20and increased with increasing ethanol concentration. The molecular weight ofWE-AX was determined by gel permeation chromatography, the results showed molecularweight of WE-AX from different wheat varieties was different. All five fractions precipitatedby increasing ethanol concentration contained components of the same molecular weight butthe relative proportion of these components differed among the isolated fractions. Thefraction precipitated at the highr ethanol concentration had a somewhat higher proportion oflow molecular weight components compared with the fraction precipitated at lower ethanolconcentration. These results also imply that an increase in the A/X ratio of arabinoxylanoccurs concomitant with a decrease of their molecular weight.The prepared WE-AX was added to wheat flour to conduct dough rheological test. Theresults of farinogramme test showed fortification of wheat flour with WE-AX can improve thewater absorption significantly, shorten the development time, and improve stability of the dough with appropriate addition quantity. Results of extensigraph test showed adding WE-AXincreased resistance to stretching, maximam resistance, extensibility and energy of the doughsignificantly. The improving effect of high molecular weight fractions of WE-AX on thequality of flour was greater than that of low molecular weight fractions.Sensory evaluation and texture analysis were used to assess the quality of Chinesemantou, the results showed addition of WE-AX with appropriate addition quantity incread thevolume and specific volume of Chinese mantou, improved the appearance and structure ofChinese mantou, decreased the hardness of Chinese mantou and increased the springiness,resilience and cohesiveness of Chinese mantou, but did not improve the color of Chinesemantou. The improving effect of high molecular weight fractions of WE-AX on the quality ofChinese mantou was greater than low molecular weight fractions.The aging of Chinese mantou mainly occured in the first24h of store time. The hardnessand chewiness increased and springiness, resilience and cohesiveness reduced significantlyduring the aging process of Chinese mantou. Addition of WE-AX could slow the the degreeof hardness increase, springiness decrease of Chinese mantou and hardness increase ofChinese mantou skin during the aging process of Chinese mantou. |
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