果胶凝胶机理及影响凝胶的因素

果胶物质广泛地分布于植物的果实、根、茎、叶中,是细脆壁的一种组成成份。存在于相邻细脆壁的中胶层中,起着将细胞粘连在一起的作用。它决定着菜果的硬度。果胶可作为果冻等食品,作果酱、巧克力,糖果的稳定剂,也能用来防止糕点的固化。     

改性果胶水凝胶的构建及应用研究进展

天然果胶多以高酯果胶形式存在,在形成水凝胶时需要强酸性环境和高浓度的糖,且形成的水凝胶属于物理交联水凝胶,在应用过程中存在强度弱、韧性和稳定较差等缺陷。因此针对天然果胶的结构进行一定的修饰,以改善其固有的凝胶性能,从而制备凝胶性能良好的改性果胶水凝胶,使其能够更好地应用于食品和药品领域成为了近年来的研究热点。该研究首先总结了果胶的改性方法及改性果胶水凝胶的构建方法;其次阐述了改性果胶水凝胶在食品及药品领域的应用现状;最后指出了果胶改性及改性果胶水凝胶构建和应用研究中存在的一些问题,并对未来的发展方向进行了展望,以期为实现果胶水凝胶的进一步开发和利用提供参考依据。     

不同工艺条件对桔皮果胶钙产量的影响

为提高桔皮果胶钙的产量,以桔皮为原料,用钙盐析法沉淀果胶,利用单因素和正交分析法,探讨pH、盐析时间、盐析温度、氯化钙添加量等因素对果胶钙产量的影响。结果表明,pH、盐析时间和温度对果胶钙产量影响显著,氯化钙添加量对果胶钙产量的影响不显著。生产果胶钙的最适宜条件为:pH10.00,温度40℃,时间6h,CaCl2用量为7.2gCaCl2/100g干桔皮,此条件下的桔皮果胶钙产量为19.67%。本研究为生产果胶钙提供了一定的参考。      

低甲氧基果胶凝胶特性的研究

以桥联作用为基础，研究了低甲氧基果胶与多价金属离子形成桥联时的数量关系，以及不同金属离子，ＰＨ值对ＬＭＰ凝胶速度，质地，稳定性的影响，为解决ＬＭＰ在应用中存在的脱水，凝胶不匀等现象提供了科学依据。     

酰胺化低酯果胶凝胶破碎强度的影响因素

酰胺化低酯果胶具有较普通低酯果胶更优越的胶凝性质,国外对其的研究已经不限于制备工艺,而更多在于其性质及新产品的应用开发,但国内的研究还几乎是空白.本文以柑橘酰胺化低酯果胶为研究对象,对其凝胶破碎强度的影响因素进行了研究.研究其形成凝胶时的影响因素:凝胶保存时间与温度、成胶条件(果胶浓度、体系pH、钙离子浓度、缓冲盐的种类及含量),并探讨了各因素对凝胶破碎强度影响的机理.此外,对比高酯果胶形成的凝胶,研究了酰胺化低酯果胶凝胶的热可逆性质.研究表明其成胶时主要受到凝胶保存的温度与时间、酰胺化低酯果胶含量、凝胶体系pH、钙离子浓度、蔗糖浓度、缓冲盐种类及添加量等因素的影响;其中缓冲盐的种类及含量对凝胶破碎强度有影响;并且,酰胺化低酯果胶的热可逆性也与缓冲盐有关.该结论为其作为胶凝剂在食品中的应用打下良好的理论基础.     

羧甲基纤维素钠对低酯果胶凝胶流变特性及凝胶形成的影响

为探究羧甲基纤维素钠(sodiuncarboxy methyl cellulose,CMC)在低酯果胶凝胶形成过程中的作用,以低酯果胶为原料,在pH 5.5下加入不同用量的CMC,考察复配后果胶凝胶的流变学性能,并对其凝胶形成进行了动力学分析。结果表明,CMC/低酯果胶复配体系是典型的假塑性流体,随着CMC添加量的增大,CMC/低酯果胶复配体系的黏度系数K增大,流体系数n减小。CMC的加入还能提高凝胶体系的黏性与弹性,当CMC的添加量为0.8%时,果胶凝胶体系的假塑性最强。同时,CMC还能提高凝胶形成速度,CMC添加量为0.8%时,SDR曲线和G'曲线明显上升,表现出较快的凝胶速度和较强的凝胶强度,当添加量大于0.8%时,凝胶形成速度下降。     

黑加仑果胶凝胶特性的研究

以ＰＨ值、加糖量、温度等因素对黑加仑果胶凝胶作用的影响研究结果表明,制作黑加仑果冻以ＰＨ２．９～３．１,加糖量７０％～８０％,成品质量最佳。     

果胶在低糖条件下凝胶的初探

以低甲氧基果胶为例,研究了在低糖条件下,果胶浓度、钙试剂种类及使用量、溶液pH、溶液温度及加热时间不同对果胶凝胶的影响。通过单因子实验、正交实验、感官评定等方法得出最佳凝胶组合,目的在于开发低糖食品。      

果胶在低糖条件下凝胶的初探

以低甲氧基果胶为例,研究了在低糖条件下,果胶浓度、钙试剂种类及使用量、溶液pH、溶液温度及加热时间不同对果胶凝胶的影响。通过单因子实验、正交实验、感官评定等方法得出最佳凝胶组合,目的在于开发低糖食品。     

Effect of oxidised starch on calcium pectinate gels

Small-deformation oscillatory measurements have been used to study the effect of low-viscosity oxidised starch on the rheology of calcium pectinate gels formed by controlled cooling from the sol state at high temperature. Large reductions in modulus (G′; 0.5% strain; 10°C) were observed at starch concentrations below the minimum critical concentration for gelation of oxidised starch alone under the same conditions (32 wt%). This behaviour is tentatively ascribed to thermodynamic incompatibility between the two polymers causing incipient precipitation of calcium pectinate within the gel network.     

Optimization and release characteristics of catechin-loaded calcium pectinate beads by internal gelation

Food Science and Biotechnology - The aim of this study was to optimize the composition of catechin-loaded calcium pectinate gel (CPG) beads formed using internal gelation and to evaluate the...     

Factors influencing the formation and relative distribution of haloacetic acids and trihalomethanes in drinking water

Various water quality and treatment characteristics were evaluated under controlled chlorination conditions to determine their influences on the formation and distribution of nine haloacetic acids and four trihalomethanes in drinking water. Raw waters were sampled from five water utilities and were coagulated with alum and fractionated with XAD-8 resin. The resulting four fractions--raw and coagulated water and the hydrophobic and hydrophilic extracts--were then chlorinated at pH 6 and 8 and held at 20 degrees C for various contact times. The results show that increasing pH from 6 to 8 increased trihalomethane formation but decreased trihaloacetic acid formation, with little effect on dihaloacetic acid formation. More trihalomethanes were formed than haloacetic acids at pH 8, while the reverse was true at pH 6. Hydrophobic fractions always gave higher haloacetic acid and trihalomethane formation potentials than their corresponding hydrophilic fractions, but hydrophilic carbon also played an important role in disinfection byproduct formation for waters with low humic content. The bromine-containing species comprised a higher molar proportion of the trihalomethanes than of the haloacetic acids. The hydrophilic fractions were more reactive with bromine than their corresponding hydrophobic fractions. Coagulation generally removed more haloacetic acid precursors than trihalomethane precursors. Waters with higher specific ultraviolet absorbance values were more amenable to removal of organic material by coagulation than waters with low specific ultraviolet absorbance values. Experimental evidence suggests that haloacetic acid precursors have a higher aromatic content than trihalomethane precursors.     

Measurement of the colour and transparency of gels: application to fruit gels

Colour measurement was studied in peach gels prepared with different amounts of peach pulp, using carrageenan or a mixture of carrageenan and locust bean gum as gelling agent. The colour was measured conventionally, in CIELAB terms, applying Kubelka—Munk criteria. The K/S parameter values in relation to lightness are a good representation of the sensory lightness of the samples, whereas the L^* values are not. In the case of colour intensity, both the Kubelka—Munk and CIELAB parameters are a good representation of the sensory colour intensity. The use of carrageenan on its own or in a mixture of carrageenan and locust bean gum does not produce differences in the visual appearance of these two types of gels. Finally, mathematical equations were developed that relate K/S to the fruit and sugar concentrations. It was found that fruit concentration has a greater effect than sugar concentration on the K/S values of these equations, which agrees with the sensory valuation of the appearance of these gels.     

On the preparation of calcium alginate isotropic gels using water-soluble calcium salts

The introduction of NaCl into the gel-forming system sodium alginate-CaCl₂-H₂O allows to obtain monolithic isotropic calcium alginate gels by use of the method of mechanical mixing of the reagent solutions. To reach the maximum firmness of the 1.5% gel the NaCl concentration of 0.1 M is necessary.     

大豆11S球蛋白凝胶形成的影响因素分析

以低温脱脂大豆粕为原料,采用等电点冷沉法浸提11S球蛋白。对11S球蛋白凝胶形成过程中影响凝胶质构的因素进行了分析,研究表明,11S球蛋白凝胶形成时蛋白浓度、加热温度、加热时间、蛋白溶液pH对凝胶质构均有一定的影响。采用正交实验设计,通过质构仪进行物性测定比较其凝胶性,大豆11S球蛋白浓度14%、加热温度90℃、溶液pH为7、加热时间60min条件下形成的凝胶强度最好,其凝胶面积410.30g·s,凝胶力117.9g。      

The formation and structure of milk protein gels

The formation of gels from milk proteins is irreversible. Most are not suitable for optical or rheological approaches.Various gels from milk products are discussed: those made by the action of rennet on whole milk, yoghurt, those from heated milk and by the storage of heated milk and gels made from whey protein of very high nutritional quality.     

Factors influencing dairy farmers' antibiotic use: An application of the COM-B model

In dairy farming, mastitis treatment is the most common reason for antimicrobial use. The overuse or misuse of antibiotics in agriculture has been associated with the development and spread of antimicrobial resistance (AMR). Traditionally, blanket dry cow therapy (BDCT), in which all cows receive antibiotic treatment, was used prophylactically to prevent and manage disease spread. In recent years, there has been a move toward selective dry cow therapy (SDCT), in which only clinically infected cows are treated with antibiotics. This study aimed to explore farmer attitudes toward antibiotic use (ABU), using the COM-B (Capability-Opportunity-Motivation-Behavior) model as a framework, to identify predictors of changing behavior toward SDCT and suggest interventions to encourage its uptake. Participant farmers (n = 240) were surveyed online between March and July 2021. Five items were found to be significant predictors of farmers having stopped BDCT: (1) having lower knowledge of AMR, (2) greater awareness of AMR and ABU (Capability), (3) feeling social pressure to reduce ABU (Opportunity), and (4) having greater professional identity, and (5) having positive emotions associated with stopping BDCT (Motivation). Direct logistic regression found that these 5 factors explained between 22 and 34.1% of the variance in making changes to BDCT practices. Additionally, objective knowledge was not correlated with current positive antibiotic practices, and farmers often perceived their antibiotic practices as more responsible than they actually were. A multifaceted approach, encompassing each of the predictors highlighted, should be taken to encourage farmer behavior change in relation to stopping BDCT. Additionally, as farmers' perceptions of their own behaviors may not align with their actual practices, awareness raising of what constitutes “responsible” behavior should be targeted at dairy farmers to motivate them to take action and adopt more responsible antibiotic practices.     

烟草科技成果转化的影响因素及对策建议

根据烟草企业科技成果转化现状问卷调查的有关数据,以描述性统计分析为主要依据,结合实地调研结果,得出了烟草科技成果转化的主要影响因素。构建了烟草科技成果转化对策模型,就加速行业科技成果转化提出了一系列有针对性的对策建议。