【作者】 杨贞；

【导师】 谢新华；

【作者基本信息】 河南农业大学 ， 食品工程（专业学位）， 2018， 硕士

【摘要】 淀粉是农产品的主要组分之一,被广泛应用于食品中,但糊化后的淀粉易发生老化,影响着淀粉质食品的发展。魔芋胶与淀粉复配可以有效改善淀粉的糊化特性,且在碱性条件下魔芋胶与淀粉能形成更稳定的凝胶。本文以魔芋胶为对象,主要研究魔芋胶在三种不同碱性环境中（Na₂CO₃、NaHCO₃、NaOH）对小麦淀粉的糊化特性、质构特性、流变特性及冻融稳定性的影响,为魔芋胶在淀粉质食品中的应用提供理论依据。用快速黏度分析仪和质构仪分别测定不同比例（5%、10%）的魔芋胶在（0.1%、0.2%）三种碱（Na₂CO₃、NaHCO₃、NaOH）性环境中对小麦淀粉糊化和质构特性的影响。结果显示,在小麦淀粉中加入（5%、10%）魔芋胶后,小麦淀粉的糊化温度降低,峰值黏度升高,最终黏度升高,但崩解值和回生值下降,小麦淀粉凝胶弹性和内聚性有所增加,硬度下降。在碱性环境中小麦淀粉的峰值粘度和最终黏度略有降低,且碱性越大黏度降低越明显。魔芋胶和碱以不同比例添加到小麦淀粉中,糊化后的小麦淀粉凝胶的流变性用流变仪测定,结果显示,魔芋胶的加入使小麦淀粉凝胶的滞后环面积明显变小,且魔芋胶添加量增大,滞后环面积减小更多。在添加碱后,小麦淀粉凝胶的滞后环面积降低得更明显,且碱性越大滞后环面积越小。添加NaOH的滞后环面积最小,碳酸钠次之,碳酸氢钠的滞后环面积最大。魔芋胶和碱以不同比例添加到小麦淀粉中,经糊化形成的凝胶经过反复冻融,测定小麦淀粉凝胶的结晶度和微观结构。结果表明,小麦淀粉中加入（5%、10%）魔芋胶后,小麦淀粉的结晶度增加,三种碱的加入使淀粉结晶度也都有所增加但不明显,这表明魔芋胶和碱对淀粉重结晶方面不能有效抑制;原小麦淀粉凝胶微观结构中片状基质较紧密且空腔大小均一完整,魔芋胶和碱的添加使得小麦淀粉凝胶微观结构的空腔明显变大,这表明魔芋胶和碱都不利于小麦淀粉凝胶的冻融稳定性的保持。更多还原

【Abstract】 Gelatinized starch tends to age during cold storage.It is well established that konjac gum can improve the properties of starch.In order to better understand the application of konjac gum in starch processing,we studied the effect of konjac gum and alkali on the pasting and texture properties of wheat starch.We investigated the effects of alkali（0.1%-0.2%）and konjac gum（5%-10%）on pasting properties and texture properties of wheat starch using Rapid Viscosity Analyzer（RVA）and Texture Profile Analyzer（TPA）.With the addition of konjac gum,the peak viscosity,final viscosity and Setback,breakdown decline,but the gelatinization temperature increased.Meanwhile,the hardness of starch gradually decreased,resulting in the increase of elasticity and cohesiveness.We also found that the peak viscosity and final viscosity declined with the addition of alkali,and the reduce degree is Na OH>Na₂CO₃>Na HCO₃.It is indicated that,the mixed system was pseudo-plastic fluid.The lag ring area of wheat starch decreased with the additation of konjac gum.And we further found that the lagging ring area depend strongly on the amount of konjac gum.It drasticly decreased with the increase of the konjac gum.After adding alkali,the area of the lagging ring decreased obviously.Wheat starch（WS）gels subjected to repeated freezing and thawing tend to decrease in quality.We investigate the effect of alkali and konjac gum（KGM）on crystallinity,microstructure and texture properties of wheat starch in order to improve the freeze-thaw stability of wheat starch gel,.Wheat starch gels containing alkali and konjac gum were treated to 7 freeze–thaw cycles.From the results of X-ray diffraction,we can conclude that the crystallinity of wheat starch gels increased with the addition of konjac gum.The crystallinity of wheat starch gels increased obviously with the addition of alkali.It indicated that the konjac gum and alkali cannot inhibited the recrystallization of the starch gel.As illustrated in the SEM images,the pore size of the freeze–thaw gels becomes bigger as the concentration of the konjac gum increased.Meanwhile,the surrounding matrix becomes weaker.Besides,we found that the matrix became thinner and crisper with the addition of alkali.The hardness of starch gradually decreased.It demonstrated that konjac gum was not an effective agent for preserving the quality of freeze–thawed wheat starch gels and inhibited the retrogradation of wheat starch gel.更多还原