【作者】 李振宇；

【导师】 张凌；

【作者基本信息】 吉林大学 ， 食品科学与工程， 2021， 硕士

【摘要】 我国拥有丰富的魔芋资源,魔芋葡甘聚糖(konjac glucomannan,KGM)是其中最主要的功能因子,它具有优良的凝胶性、增稠性、成膜性等理化性质,以及降糖降脂、调节肠道、增强免疫力等功能作用,但存在纯度较低、完全溶解时间长、溶胀过程易出现包胶块等问题,导致其在食品工业中的应用受到限制。因此,提高KGM纯度,开发凝胶态产品至关重要。而单独的KGM凝胶缺乏疏水性、粘度较大、溶解度低、性质不稳定,天然亲水胶体复配是改善单一凝胶缺陷简单而有效的手段。本文以魔芋精粉为原料,首先采用超微联合辅助乙醇沉淀的方法对KGM进行纯化,然后将KGM与阿拉伯胶(Gum arabic,GA)共混改性,分析复合凝胶性质的变化以及KGM与GA之间的协同作用,进而研究β-环糊精(β-cyclodextrin,β-CD)对KGM/GA凝胶性能的影响,最终确定KGM/GA溶胶制备的最优工艺。试验主要研究内容和结果如下:(1)采用超微联合辅助乙醇沉淀的方法纯化KGM,通过单因素试验和响应面优化得到最优工艺参数为:乙醇浓度70%,料液比1:120,超声功率300 w,超声时间33 min,微波功率300 w,微波时间10 min。此条件下KGM的纯度可达96.87%。(2)制备KGM/GA复合凝胶,通过水溶性、吸水性、质构、流变、傅里叶红外和扫描电镜的分析结果发现:GA的加入可以提高凝胶的水溶性和吸水性;当GA浓度较低时(0～2.0%),随着GA的浓度增加,凝胶的硬度和弹性降低,内聚性增加,凝胶强度减弱,网络结构变得疏松;但当GA的浓度从2.0%增加至4.0%时,凝胶的硬度和弹性增加,内聚性减小,凝胶强度提高,网络结构更加致密;KGM/GA凝胶为物理凝胶,具有剪切稀化性,非共价交联主要涉及氢键和疏水相互作用,且以氢键为主。KGM与GA在低GA浓度时具有协同减效作用,高GA浓度时具有协同增效作用。(3)分析β-环糊精对KGM/GA凝胶性能的影响,通过水溶性、吸水性、质构、流变、傅里叶红外和扫描电镜的结果发现:β-CD增加,凝胶的水溶性和吸水性也增加;当β-CD的浓度从1.0%增加至2.0%时,凝胶的硬度和弹性逐渐增加,内聚性减小,但当β-CD的浓度从2.0%增加至3.0%时,变化趋势正好相反;β-CD能够使氢键和疏水相互作用增加,提高凝胶强度和网络密度,但未改变凝胶非牛顿假塑性流体和反触变性的流变学性质。适量的β-CD有助于提高KGM/GA凝胶的性能。(4)根据KGM与GA的协同作用制备KGM/GA溶胶,KGM的粘度与浓度呈指数关系,其与GA的协同减效作用在二者比例约7:3时最强;通过单因素试验和二次回归正交优化得到KGM/GA溶胶复配的最优工艺为:KGM浓度1.75%,GA浓度1.02%,β-CD浓度0.6%,搅拌时间50 min。此条件下溶胶粘度可以达到49.11 Pa·s。更多还原

【Abstract】 There are rich konjac resources in our country,in which konjac glucomannan is the main functional factor.It has excellent gelling,thickening,film-forming and other physicochemical properties as well as functional effects such as reducing blood glucose and lipid,regulating intestine and enhancing immunity.However,there exist some disadvantages that limit its applications in food industry,such as lower purity,long time of complete dissolving and easy occurrence of encapsulated block during swelling process.Therefore,it is important to improve the purity of KGM and develop gel products.Single KGM gel has some shortcomings,such as lack of hydrophobicity,high viscosity,low solubility and unstable property.Compounding of natural hydrocolloids is an easy and effective method for overcoming the deficiency of a single gel.In this study,KGM was purified with ethanol precipitation which was assisted by ultrasonic wave-microwave,using konjac flour as the raw material.Then,composite gel was prepared by KGM and GA.Changes of gel properties as well as the synergy between KGM and GA were analyzed.Further,the impact ofβ-cyclodextrin on KGM/GA composite gel was studied.Finally,the optimal process of KGM/GA sol was determined.The main contents and results of our experiment are as following:(1)KGM was purified by ethanol precipitation assisted by ultrasonic wave-microwave.The optimal process parameters which were determined by single factor test and response surface methodology are as following: ethanol concentration70%,material to liquid ratio 1: 120,ultrasonic power 300 w,ultrasonic time 33 min,microwave power 300 w,and microwave time 10 min.Under these conditions,KGM purity can reach 96.87%.(2)Composite gel was prepared by KGM and GA.The results of water solubility,water absorption,texture,rheology,Fourier transform infrared and scanning electron microscope are as following: The addition of GA can improve water solubility and water absorption of gels.When GA concentration is lower(0～2.0%),with the increase of GA,hardness and springiness of gels decline,but cohesiveness increases;gel strength decreases and network structures become looser.However,when GA increases from 2.0% to 4.0%,hardness and springiness increase,but cohesiveness decreases;gel strength increases and network structures become denser.KGM/GA composite gel is a physical gel,with shear thinning property.Non-covalent linkages mainly involve hydrogen bonding and hydrophobic interaction,in which hydrogen bonding is dominant.KGM and GA have antagonistic effect at low GA concentrations and synergistic effect at high GA concentrations.(3)The effect of β-cyclodextrin on KGM/GA gel was studied.The results of water solubility,water absorption,texture,rheology,Fourier transform infrared and scanning electron microscope are as following: Water solubility and water absorption of gels both increase with β-CD.When β-CD increases from 1.0% to 2.0%,hardness and springiness of gels increase,but cohesiveness decreases.When β-CD increases from 2.0% to 3.0%,the trends are opposite.β-CD can promote hydrogen bonding and hydrophobic interaction,resulting in higher gel strength and denser network structures.However,it does not alter the non-Newtonian pseudoplastic property and anti-thixotropy of gels.An appropriate amount of β-CD can improve properties of KGM/GA gel.(4)KGM/GA composite sol was prepared according to the interaction between KGM and GA.The viscosity of KGM is exponentially related to concentration.The antagonistic effect is strongest when the ratio of KGM to GA is about 7: 3.The optimal conditions of KGM/GA sol which were determined by single factor test and quadratic regression orthogonal experiment are as following: KGM concentration1.75%,GA concentration 1.02%,β-CD concentration 0.6% and stirring time 50 min.At this time,the sol viscosity can reach 49.11 Pa·s.更多还原