【作者】 刘贺；

【导师】 过世东；

【作者基本信息】 江南大学 ， 食品科学， 2007， 博士

【摘要】 本文主要通过流变学方法研究桔皮果胶凝胶性质和凝胶机理,并利用果胶为原料开发一种脂肪替代品PFM,考察PFM在不同食品体系如低脂涂抹食品,低脂乳制品和低脂焙烤食品中的应用效果。通过对不同酯化度、酰氨化度低酯桔皮果胶凝胶体系的流变学分析,对于低酯果胶,探讨果胶浓度及钙离子浓度对凝胶弹性模量、粘性模量、tanδ在降温过程中变化的影响。结果表明较低的酯化度对于形成更多的“蛋盒”结构起促进作用,酰氨基团可能促使果胶链之间通过氢键作用从而提高凝胶强度,但酰氨化度较高的果胶凝胶结构具有相对的不稳定性。对于高酯果胶,探讨了蔗糖与果胶浓度对高酯果胶凝胶性质的影响,酯化度不同的高酯果胶其凝胶的速度不同,酯化度越高,在同等条件下其凝胶强度越大,而且凝胶也较稳定。就同一种高酯果胶来讲,果胶浓度及蔗糖浓度与其网络结构的紧密程度和稳定性呈正相关。综合分析,酯化度为34-40%、酰氨化度为12-16%的桔皮果胶SF530较适合作为脂肪替代品的原料。因此就其凝胶进行了分形及动力学分析以期为进一步利用其凝胶性质提供理论支持。在研究范围内,SF530凝胶的分形维数介于1.48至1.97之间,其微观结构可以通过数学的方式表达出来。凝胶动力学分析表明,SF530果胶浓度对凝胶在冷却中的弹性模量及凝胶形成速度有很大影响,果胶浓度越大,凝胶的弹性模量曲线越高,凝胶形成的速度越快。高浓度的果胶与相应的钙离子形成了更多的缔合区从而使凝胶结构更坚实。pH同样对凝胶体系冷却过程中弹性模量及凝胶形成速度有很大影响,在pH值为3.0左右凝胶体系比较坚实,凝胶形成速度比较快。凝胶活化能的影响条件比较复杂,而且在凝胶形成前后有两个温度区域供分析。只有在果胶链比较丰富的前提下,果胶浓度才会对凝胶形成的能量壁垒产生显著的影响。在低钙离子浓度条件下,果胶浓度对于Mc的影响不明显,当钙离子浓度较高时,果胶浓度越大,Mc越小,形成的网络结构更趋于复杂。探讨了高酯果胶与SF530果胶交互作用形成热不可逆凝胶的机理。通过响应面分析,得到可以预测高酯与低酯果胶混合凝胶持水性、硬度、粘附性、胶着性和咀嚼度的数学模型,为后续研究及工业化生产提供理论支持。通过岭迹分析,得到有利于进行微粒化处理的混合果胶凝胶组成:低酯与高酯果胶浓度比为2:1的混合果胶浓度为1.95%,钙离子浓度为20mMol/L,GDL添加量为1%。选择CMC作为混合凝胶微粒的保护性外相,能显著提高产品的稳定性,缓解产品脱水现象。通过已经申请发明专利的加工工艺,制得由SF530为主要成分,配以高酯果胶和CMC的脂肪替代品—PFM。该产品的粒径范围为:d32,46.883μm;d43,74.236μm;d0.5,57.517μm;d0.9,133.135μm。用储存试验针对粒径和流变性变化进行了分析,结果表明,PFM具有良好的稳定性。流变学、显微分析、感观评定等方法研究结果表明,PFM在蛋黄酱中一方面提供了类似油脂的感观性质,另一方面与蛋黄酱样品中其他成分相互作用,影响体系的结构,随储存时间其流变性质有一些变化。总体来看,PFM在蛋黄酱类产品具有应用潜力。以微粒化果胶凝胶、果胶弱凝胶、微粒化果胶-乳清分离蛋白凝胶作为脂肪模拟品应用于低脂蛋黄酱,对比这三种脂肪替代品的应用效果。结果表明,三种脂肪模拟品均对低脂蛋黄酱的质构有改善作用,以果胶弱凝胶的作用最为明显。感观分析表明微粒化果胶凝胶对低脂蛋黄酱感观方面贡献最大。但后续研究表明,添加果胶弱凝胶的低脂蛋黄酱在储存一周后会逐渐形成凝胶,不具有塑性,涂抹性变差;而以微粒化果胶凝胶作为模拟品的蛋黄酱在储存三周后容器底部有明显的水沉淀下来,而且蛋黄酱的质构变得粗糙,可能是凝胶微粒不稳定,在储存期再次聚集。通过比较四种以果胶为原料的脂肪替代品应用效果可知,将微粒化果胶凝胶添加惰性外相,是制备稳定PFM的关键。PFM在低脂干酪中的应用研究表明,脂肪含量的降低和水分含量的增加导致低脂模拟干酪微观结构松散,替代脂肪含量50%的低脂干酪具有较低的硬度、胶着性、咀嚼度和黏附性。添加PFM做为脂肪替代品使低脂产品更接近于高脂产品。PFM的添加降低了产品的融化焓。PFM在低脂重油蛋糕中的应用研究表明,PFM能够替代重油蛋糕中的脂肪归功于其具有维持面团结构的功能和模拟脂肪口感的特点。从质构分析和感观分析发现,脂肪替代量40%以下低脂蛋糕与传统高脂对照差别不大。研究结果表明,本研究制备的脂肪替代品在低脂涂抹食品、低脂乳制品及焙烤制品具有很大的应用潜力。更多还原

【Abstract】 Based on the studies of former researchers, the thesis discussed the properties and relative theories of pectin gelation process. Developing a new type fat replacer as pectin gel as the basic material, the author applied this fat replacer to reduce fat content of some food such as spreads, milk products and baking products to study the effects of it on the properties of such low fat food.Through study the rheological properties of different DM and DA citrus pectin gel. Discussing the effects of concentration of pectin and calcium ion on the elastic modulus and viscous modulus and tanδ.Concentration of sugar and pectin show little effects on the HM pectin. The SF530 showed the better gelation properties.Fractal analysis of the SF530 pectin gel showed that concentration of pectin acted improtant role during the gelation process. And the fractal dimension of different system were all lower than 2.0. The results should be understood better after more study.The results indicated that high concentration pectin promoted the formation of the pectin gel and increased the gelation speed of the pectin dispersions. The pectin concentration brought more effect to the gelation of the dispersion than the calcium ion.Only when pectin chain abundant, the difference of the structure of the pectin might effect the energy barrier in developing the pectin network. It was found that, at the fixed calcium ion content, the higher the pectin content, the lower the Mc in both two type pectin except when the calcium ion concentration was 6mMol/L.Through adding the calcium ion to the mixture of LM and HM pectin to induce heat irreversible gel. By study the WHC and texture of the mixture system of HM and LM pectin system based on the RSM analysis. Obained the regression model for forecasting some index of the gel. Select inertia polysaccharid as outer pahse to stabilize the PFM system. Optimized the process of preparation to get the appropriate product to imitate fat.Application of whey protein isolate and low-methoxy pectin based fat mimetics in mayonnaise was studied. Fat was partially substituted by different fat mimetics at levels of 50% respectively which the fat mimetics were referred to as PFM1 (mciropaticulate pectin gel), PFM2 (pectin weak-gel), and PFM3 (microparticulated combination of WPI and pectin). The full fat (Ff) (100% oil) mayonnaise without fat mimetic was used as a control experiment. Physicochemical, rheological, texture analysis, and sensory evaluation of the Ff and low fat (Lf) mayonnaises were performed. The results indicated that all Lf mayonnaises had significantly lower energy content, but higher water content than their Ff counterpart. In terms of texture, the formulation with pectin weak-gel as fat mimetic showed similar texture values as those of the Ff sample. Both Ff and Lf mayonnaises exhibited thixothopic shear thinning behaviour under steady shear tests and were rheologically classified as weak gels under small amplitude oscillatory shear tests. Sensory evaluation demonstrated that mayonnaises substituted with low methoxy pectin were acceptable. This study shows good potential for pectin weak-gel and microparticulated pectin gel to be used as a fat mimetic in mayonnaise. But the later study showed that the low fat mayonnaise with weak pectin gel as fat replacer became gel after one week storage. And there were water separated from the mayonnaise with microparticulated combination of WPI and pectin as fat replacer. The reason might be that the microparticle recongregate each other.Add outer phase to the above mciropaticulate pectin gel,and as fat replacer applied to the mayonnaise. Through rheology, microsturcture, sensory analysis study, it was found that PFM had the fat like sensory properties and might interact with other ingredients for the rheological properties varied during storage. And the PFM act good roles as fat replacer.Fat reduction in semi-solid cheese analogues and the use of pectin gel affected low-fat samples in different ways. Fat reduction and moisture augment caused the microstructure of low-fat cheese analogues obviously more loose. The low-fat samples showed lower hardness, gumminess, chewiness and adhesiveness and low-fat samples with pectin gel addition were more similar to the full-fat cheese analogues. Pectin gel addition showed that it can decrease the melt enthalpy of the samples which may be due to the conformation or structural change of pectin or pectin interacted with fat or protein to decrease the Delta H. The low-fat cheese analogue made with pectin gel addition was well received by the sensory panel. The properties of the low-fat cheese with pectin gel such as texture, microstructure and rheology were midst full-fat and low-fat without pectin gel addition samples. The results suggest that pectin gel may play the role of fat mimetic when added to cheese analogues.Functionality of fat mimetic from pectin on the low-fat high-ratio cakes might due to its ability to maintain the structure of the batters just as fat. In the same time the micro particles of the fat mimetic had the similar sensory properties as fat granules in the cakes. From the texture and evaluation analysis, it was found that when fat was 20, 40% replaced, the low-fat cakes were similar as the control sample.In conclusion,the PFM had the potential to applied in the low fat spreads, low fat milk products and low fat baking products.更多还原