【作者】 牛猛；

【导师】 陈正行；

【作者基本信息】 江南大学 ， 食品科学， 2014， 博士

【摘要】 全谷物食品已成为目前流行的回归自然的健康食品。全麦食品是健康谷物食品中以全麦面粉为主要原料的食品。其中，全麦鲜湿面不仅迎合现代人的饮食需求，还能改善人们的膳食结构，增加营养物质的摄入。但是，褐变一直是影响全麦鲜湿面产业化生产的技术瓶颈。如何抑制全麦鲜湿面褐变的发生，对于提高全麦鲜湿面品质，延长货架期具有重要意义。同时，全麦鲜湿面中麦麸的存在，必然导致质构和感官品质的下降。因此，研究全麦鲜湿面质构和感官品质的改良技术，有利于增加消费者的喜爱程度和全麦鲜湿面的推广。本论文首先研究麦麸回添和整粒碾磨两种碾磨方式对全麦面粉性质和全麦鲜湿面品质的影响。结果表明，麦麸回添工艺中麦麸粒径的减小会增加多酚氧化酶(PPO)活性和面条的褐变，两者增长呈显著正相关(r=0.92)，但在贮藏期间内提高了全麦鲜湿面的亮度值，增加了面条的弹性和凝聚性；采用整粒碾磨的方式可以有效降低全麦面粉的平均粒径，最小可达到43μm，制成的鲜湿面在颜色、蒸煮品质、质构特性和微观结构品质等方面有所提高，但在碾磨过程中产生的过量破损淀粉（最多可达到26.03%）会带来对品质的干扰；两种全麦面粉碾磨方式相比，整粒碾磨方式的碾磨效率较高，但麦麸回添工艺能够更好的改善全麦鲜湿面的凝聚性和回复性等质构特性。研究全麦鲜湿面的褐变曲线以及温度、水分及pH对全麦鲜湿面褐变的影响，考查多酚氧化酶和麦麸中酚类物质对酶促褐变的影响，并对全麦鲜湿面非酶褐变机制进行初步探讨。结果显示，全麦鲜湿面在0-24h内的褐变曲线可以被分为三个阶段，Ⅰ阶段(0-0.5h)和Ⅲ阶段(4-24h)曲线可以用一次线性函数来表示，Ⅱ阶段(0.5-4h)曲线呈非线性指数变化趋势；在35-40℃范围内全麦鲜湿面的褐变程度最高，加水量的升高会增加全麦鲜湿面的酶促褐变，当pH为6时全麦鲜湿面的褐变程度最高，非酶褐变在pH低于5时显著降低；PPO是引起全麦鲜湿面褐变Ⅱ阶段和Ⅲ阶段的主要原因，游离态酚类占总酚比例的多少也是影响褐变程度的因素之一；全麦鲜湿面非酶褐变的反应速率与温度的关系曲线(InK-1/T)近似于一条直线，拟合趋势线的R2为0.89；在25℃下保存时，全麦鲜湿面中可以检测到两种美拉德中间产物-糠氨酸和羟甲基糠醛，说明在常温下贮藏时，全麦鲜湿面的非酶褐变中存在低温美拉德反应的发生；在PPO活性存在或者被抑制时，酪氨酸的加入都能增加Ⅱ阶段和Ⅲ阶段的褐变，表明酪氨酸与PPO或者活性氧簇作用所发生的氧化反应也可能是面条褐变的机制之一。采用超声波与抗氧化剂协同处理的技术降低全麦鲜湿面的酶促褐变，并通过改变体系中的pH和添加还原剂的方法抑制非酶褐变。利用超声波和抗氧化剂相结合的方法能够显著降低麦麸中PPO的酶活，其中超声波与抗坏血酸相结合的灭酶效果最佳，可使酶活残留降低到7.25%；经过超声波和抗氧化剂协同处理后面条褐变的程度明显减小，可以使褐变降低48%；经处理后麦麸中的部分游离酚类物质被萃取到溶液中，但对全麦面粉抗氧化性的影响较小，另外只有Zn2+的含量在超声波处理3min后显著减少；当面团中pH降低到2时，全麦鲜湿面中非酶褐变的抑制率可达到42%；当面团中亚硫酸根的浓度为0.125mol/L时，非酶褐变抑制率可达到50%左右。采用Mixolab研究全麦面团的热机械学性质，并通过加入酶制剂和乳化剂的方法改善全麦鲜湿面的质构和感官品质。结果表明，相对于普通面团，全麦面团的形成时间较短，弱化度较大；在三种酶制剂中，谷氨酰胺转移酶对全麦面团热机械学曲线影响显著，它能够延长全麦面团的形成时间，降低弱化度和淀粉凝胶的回生程度，对鲜湿面的质构特性、感官品质和微观结构的提高效果在三种酶制剂中最为显著；两种乳化剂中，添加硬脂酰乳酸钠后全麦面粉中淀粉的粘度值上升，面团的形成时间显著延长，弱化度减少，全麦鲜湿面的质构特征，感官评定指标和微观结构品质也得到提高。采用糯质全麦粉改变全麦面粉中直链/支链淀粉的比例，并考查其对全麦面团流变学性质、水分结合状态及全麦鲜湿面品质的影响。糯质全麦粉的加入显著增加了全麦面粉中支链淀粉的含量；流变学性质显示在0.1-10Hz扫描范围内储能模量和损耗模量在同一扫描频率下的大小顺序均为部分糯质组>对照组>全糯质组；部分糯质全麦粉加入后，面团T21阶段的峰值都向左偏移，表明部分糯质全麦粉能够增强面团对水分结合，全糯质全麦粉加入后各段的信号幅度都有所增加，但结合水占面团中总水分的比例并没有显著增加；全糯质全麦粉加入后，面条的质构特性显著下降，部分糯质全麦粉则提高了鲜湿面的弹性、凝聚性和回复性等质构品质。考查四种磷酸盐和两种食用胶体对全麦面粉热力学性质、糊化特性及全麦鲜湿面品质的改良作用。实验结果显示，添加磷酸盐后全麦面粉的热力学曲线向右偏移，糊化焓值升高，其中STPP和SHMP效果显著；磷酸盐的加入升高了淀粉的糊化粘度，其中DSP和TSP显著提高了全麦面粉的最高粘度和最终粘度；磷酸盐的加入抑制了面条的褐变，其中TSP效果最佳；STPP和SHMP能够显著降低全麦面条的蒸煮损失并提高了面条质构特性；综合分析得出STPP对全麦鲜湿面改良效果最佳；两种胶体中，阿拉伯胶和黄原胶分别降低和升高了淀粉的糊化粘度；阿拉伯胶的加入显著降低了面条的硬度，黄原胶的加入则显著提高了面条的硬度、凝聚性和回复性；相对于阿拉伯胶，微观结构分析显示黄原胶能够显著加强面条结构中淀粉颗粒和蛋白质网络结构的交联。更多还原

【Abstract】 Whole-grain food has been considered to be one of the popular, natural, and functionalfoods. Whole-wheat food is one kind of whole-grain food which is mostly made ofwhole-wheat flour. Whole-wheat fresh noodle (WWFN), as one of whole-wheat food, canmeet modern people’s requirement about food, and also lead to the improvement of people’sdietary pattern and the increase of functional materials intake. Darkening is always thetechnological difficulty in the production of WWFN, and the inhibition of darkening ofWWFN is of great value to improve the quality and prolong the shelf-life of WWFN; Theinclusion of wheat bran causes some adverse effects on the textural properties and sensoryqualities of whole-wheat food, the improvement technology of these properties is beneficial toincrease the popularity and extend the market of WWFN.The effects of two grinding techniques (bran-grinding and whole grain-grinding) on thecharacteristics of WWF and properties of WWFN were studied. As the results show, thereduction of wheat bran particle size could increase the PPO activity of WWF and darkeningof WWFN, the growth of the two indicators were positively correlated with correlation indexof0.92, however, the reduction of particle size improved the lightness of WWFN duringstorage, and increase the springiness and cohesiveness of WWFN; The particle size of WWFcould be significantly reduced by the whole grain-grinding technique, the minimum of MZcould be43μm, the color, cooking properties, textural properties, and microstructure ofWWFN were also improved by the reduction of particle size of WWF, but the excessivestarch damage (the maximum was26.03%in the study) produced during the grinding processcould exert adverse effect on the quality of WWFN; Compared to the bran-grinding technique,whole grain-grinding technique was more effective in decreasing the particle size of WWF,however, the cohesiveness and resilience of WWFN were more enhanced by bran-grindingtechnique than by whole grain-grinding.The darkening process curve of WWFN and the effect of temperature, moisture, pH,PPO activity and free phenols content on the darkening of WWFN were studied; themechanism of non-enzymatic darkening of WWFN was also discussed. As the results show,the darkening process could be divided into three stages: stageⅠ(0-0.5h) and stage Ⅲ(4-24h) could be expressed by linear function, and stage Ⅱ(0.5-4h) could be expressed by aexponential function; When the temperature was between35℃and40℃, WWFN had themost discoloration, the growth of water addition level increased the enzymatic darkening; themost discoloration was caused when pH of whole-wheat dough was6, and when pH wasbelow5, the non-enzymatic darkening was significantly inhibited; PPO was the major reasonfor the stageⅡand stage Ⅲ of darkening in WWFN, the content of free phenols in wheatbran was one of the factors to affect the enzymatic darkening of WWFN; The relationshipcurve between the rate of non-enzymatic darkening and temperature was nearly a straight line,the R2of the fitting line was0.89; The furosine and HMF were detected in WWFN whenstored at around25℃, indicating that mailard reaction was a part of non-enzymatic darkening of WWFN; the addition of tyrosine increased the discoloration in stage Ⅱand stage Ⅲ withand without PPO activity in WWF, which demonstrated that the oxidation action of tyrosineinduced by PPO and ROS might be a part of the darkening mechanism in WWFN.The combination treatments of ultrasound and antioxidants were conducted to decreasethe enzymatic discoloration of WWFN, the non-enzymatic darkening of WWFN was alsosuppressed by changing the pH of dough and adding reducing agent. The PPO activity inwheat bran was significantly reduced by the combined treatment of ultrasound andantioxidants, the combination of ultrasound and ascorbic acid has been proved to be mosteffective, which decreased the PPO activity to be7.25%; the darkening of WWFN wassignificantly reduced after the treatments, which could be reduced by48%, some free phenolsin wheat bran were extracted by the treatment, but it had little effect on the antioxidantcapacity of WWF, only the content of Zn2+in WWF was affected when treated by ultrasoundfor3min; The inhibition ratio of non-enzymatic darkening reached42%and around50%,respectively, when pH was2in whole-wheat dough and the concentration of sulfite was0.125mol/L.The thermal mechanical properties of whole-wheat dough were studied by using Mixolaband the effect of enzymes and emulsifiers on the textural properties and sensory qualities werealso investigated. The development time of whole-wheat dough was shorter and toleranceindex was larger than white dough; Among the three kinds of enzymes, the addition of TGhad significant effect on the curve of mixolab curve, it increased the development time anddecreased the tolerance index and setback value of the dough; It has been proved to mosteffective in increasing the hardness, springiness, cohesiveness and resilience values andimproving the sensory qualities and microstructure of WWFN; As for the two kinds ofemulsifiers, the addition of SSL increased the viscosity of WWF, it also increased thedevelopment time and decreased the tolerance index of whole-wheat dough, the texturalproperties, sensory qualities and microstructure were also improved by the addition of SSL.The waxy whole-wheat flour (WWWF) was included to alter the ratio ofamylase/amylopectin in WWF, and the effect of the addition of WWWF on the rheolgicalproperties, combination state of water in whole-wheat dough and quality of WWFN were alsoinvestigated. The inclusion of WWWF significantly increased the content of amylopectin;During the scanning range of0.1-10Hz, the decreasing rank of storage modulus and lossmodulus were partial-waxy wheat group, control, and whole-waxy wheat group; The T21shifted toward to the left after the addition of partial-waxy wheat flour, which indicated thatthe combination of dough with water was enhanced, signal amplitude of every stage increasedafter the inclusion of whole-waxy wheat flour, but the ratio of bond water was notsignificantly affected; The inclusion of whole-waxy wheat flour had adverse effect on thetextural properties of WWFN, however, the springiness, cohesiveness, and resilience ofWWFN were improved by the addition of partial-waxy wheat flour.The effect of flour kinds of phosphate and two kinds of gum on the thermal properties,pasting properties of WWF and the qualities of WWFN were studied. The thermal propertiescurve of starch in WWF was shifted to the right and the gelatinization enthalpy increased afterthe addition of phosphate, STPP and SHMP have been proved to be more effective; The pasting viscosity also increased after the inclusion of phosphate, in which the peak viscosityand final viscosity increased by DSP and TSP; TSP has been proved to be most effective ininhibiting the darkening of WWFN; The cooking loss of WWFN was declined by the additionof STPP and SHMP and the textural properties of WWFN were also increased by theinclusion of STPP and SHMP; It was concluded that STPP was most effective in improvingthe quality of WWFN; The pasting viscosity of starch in WWF decreased after the addition ofArabic gum, in contrast, the inclusion of xanthan increased the pasting viscosity of WWF;The hardness of WWFN increased by Arabic gum, while the addition of xanthan increased thehardness, cohesinveness, and resilience of WWFN; Compared with Arabic gum, thecross-linking between protein matrix and starch granules was significantly enhanced by theinclusion of xanthan.更多还原