不同硬度棕榈油基人造奶油组成及结晶行为研究

对比分析了两个不同硬度棕榈油基人造奶油的甘三酯组成、结晶特性及微观结构,试验表明人造奶油B中饱和脂肪酸含量较高,SUS型甘三酯(POP,PLP)含量偏大,同时含有少量的中碳链甘三酯;X-衍射观察到两个样品中均含有β和β′晶型,但是样品B中β′晶型占主导;SEM图像显示硬度较小的样品显微结构更疏松多孔.     

棕榈油中间分提物在零/低反式脂肪酸人造奶油中的应用

为扩大棕榈油中间分提物(PMF)在零/低反式脂肪酸人造奶油中的应用,对PMF、棕榈油硬脂(PSt)和大豆油的甘三酯组成、结晶及熔化特性进行分析。结果表明:PMF的甘三酯主要由二饱和型及单饱和型甘三酯POP、PLP、POO组成;PSt的甘三酯主要由三饱和型及二饱和型甘三酯PPP、POP组成;大豆油主要由三不饱和型及二不饱和型甘三酯LLL、OLL、PLL等组成。以PMF为主,复配PSt和大豆油作为人造奶油的基料油,可使人造奶油以二饱和型POP等形成β'结晶倾向,一定量的三饱和型甘三酯PPP等提供人造奶油的骨架结构,三不饱和型甘三酯LLL、OLL等填充高熔点甘三酯形成的网格,提高人造奶油的营养特性。PMF、PSt和大豆油三者的质量比为50∶30∶20时表现出良好的相容特性,按照这一质量比制备的人造奶油中的晶型为β'和β共存,且以β'为主,符合人造奶油的结晶及熔化性能要求。     

甘三酯结晶特性的研究进展

油脂及富含油脂食品(巧克力、冰淇淋、人造奶油等)的加工和使用性能很大程度上取决于其所含甘三酯的结晶特性。对甘三酯的晶体结构、结晶行为和结晶特性的研究方法及进展进行了综述。着重介绍了基于同步辐射光源的超小角X-射线散射技术、同步辐射X-射线衍射技术、微光束同步辐射X-射线衍射技术以及同步辐射X-射线衍射与差示扫描量热法同步结合等先进的研究手段,并总结了甘三酯单体的结晶以及甘三酯混合物体系相行为的研究进展。从结晶、动力学以及表界面特性方面对甘三酯结晶特性研究的发展方向进行了展望。     

棕榈油与棕榈油中熔点分提产物相容性及结晶形态研究

利用等温相图和偏光显微技术研究了棕榈油(PO)与棕榈油中熔点分提产物(PMF)在混合体系中的相容性及晶体形态.结果表明:PO与PMF混合体系在0～40℃相容性良好,仅在桌些温度范围内存在轻微的共晶/偏晶现象;结晶形态研究表明甘三酯组成对混合体系晶形有显著影响.     

油脂结晶改良剂对底物油脂结晶行为的调控及其作用机制的研究进展

油脂及富含油脂食品(巧克力、冰淇淋、人造奶油等)的物理特性很大程度上取决于其脂肪的结晶状态。油脂结晶改良剂的添加可以影响底物油脂的结晶行为从而改变产品的质构,进而调控油脂结晶,使其应用于各种产品和工艺中。分别对单甘酯、甘二酯、甘三酯、蔗糖酯、聚甘油脂肪酸酯、磷脂、无机物等作为结晶改良剂对不同底物油脂的结晶调控效果进行综述,并对现阶段结晶改良剂的作用机制的研究成果进行了总结。结晶改良剂的种类和用量显著影响底物油脂的结晶行为,结晶改良剂与底物油脂中主要甘三酯的匹配性是调控底物油脂结晶的关键。要实现精准调控油脂结晶,仍有待更为深入的结晶机制研究。     

一级大豆油抗冻性研究

该文研究了市售4种一级大豆油的部分理化指标、脂肪酸组成、甘三酯组成、甘一酯、甘二酯以及甾醇含量对其低温下抗冻性的影响。通过自制实验装置对大豆油进行冷冻试验和对大豆油固体脂肪含量的测定结果表明,脂肪酸组成、甘三酯组成、酸值、碘值、过氧化值、甘一酯含量对4种一级大豆油的抗冻性没有直接影响,而甘二酯的含量对一级大豆油抗冻性有一定影响。     

棉籽油硬脂和全氢化棉籽油硬脂的组成、热性质和微观结构分析

为扩大棉籽油用途，提高其附加值，采用气相色谱、高效液相色谱、低场脉冲核磁共振分析仪、差示扫描量热仪、X-射线衍射仪和偏光显微镜分析了棉籽油改性后的产物棉籽油硬脂(COS)和全氢化棉籽油硬脂(FHCOS)的脂肪酸组成、甘三酯组成、SFC含量、热性质和微观结构。结果表明：COS主要由不饱和脂肪酸和非三饱和的甘三酯组成，FHCOS几乎全部由饱和脂肪酸和三饱和甘三酯组成；随温度升高，COS的SFC不断降低，FHCOS的SFC在温度高于35℃时开始降低，相同温度下FHCOS的固体脂肪含量(SFC)均高于COS的，COS在结晶和熔化过程中均有2个峰，FHCOS有1个峰，FHCOS的熔化和结晶温度均高于COS的；COS在15℃时无明确的晶型及稳定的结构，FHCOS为二倍链长堆积的β′晶型，结晶体为针状或棒状，结晶聚集体为类似玫瑰花状。因此，以COS和FHCOS代替棕榈油作为生产起酥油、人造奶油、黄油等的基料油具有一定的开发和应用前景。     

超高效液相色谱法测定油脂中甘三酯组成

采用超高效液相色谱-蒸发光散射检测器法(UPLC-ELSD)测定油脂中甘三酯组成.以双低菜籽油为研究对象,以丙酮-乙腈(体积比63.6:36.4)混合物为流动相,探讨了流速、柱温条件对双低菜籽油中不同等价碳数(ECN)甘三酯分离效果的影响.确定了以丙酮一乙腈(体积比63.6:36.4)混合物为流动相进行梯度洗脱,柱温为45℃,方法简单快速.以此法测定不同油脂样品的甘三酯组成,所得结果与理论计算值有较好的一致性,说明此法在甘三酯组成测定中具有可行性.     

酶促酯交换椰子油制备富含MCT油脂工艺研究与优化

对脂肪酶Lipozyme RM IM催化癸酸与椰子油酯交换制备富含MCT油脂的工艺条件进行研究。结果表明:在反应温度46℃,底物摩尔比8:1,加酶量6%,加水量15%,反应时间8 h的优化工艺条件下进行多次平行试验,酯交换产物甘三酯中癸酸和MCT质量分数分别达42.31%和50.85%,与原料油相比分别增长37.57%和35.87%。产物甘三酯脂肪酸组成和甘三酯结构分析结果表明,酯交换产物甘三酯中共含有9种MCT成分,主要成分及其在产物甘三酯中的质量分数分别为DLa D(23.57%)、DLa La(16.88%)和DDD(4.83%)等。     

乌桕类可可脂巧克力等温结晶动力学研究

通过差热扫描热分析法对乌桕类可可脂巧克力在不同温度下(28℃、30℃和32℃)等温结晶动力学进行了研究,结果表明晶型Ⅴ(β')向Ⅵ(β)的衍变在不同温度下具有相同的Avrami指数(n)值,说明Ⅴ(β')向Ⅵ(β)的衍变具有相同的机理,但其衍变速率常数(Kn)值,却随温度的升高而减少,半结晶时间(ti/2随等温结晶温度的升高而延长.     

智利Maricunga盐湖模拟卤水25℃等温蒸发实验研究

文章对智利Maricunga盐湖模拟卤水进行了25℃等温蒸发试验,参考KCl-CaCl2-MgCl2∥H2O 25℃四元水盐体系进行了相图理论分析,采用X射线衍射手段进行了析出矿物的物相分析,结合化学测试结果,研究了该卤水在等温蒸发过程盐类矿物的结晶路线和析出顺序,为Maricunga盐湖卤水的开发和综合利用提供了基础数据,将为我国现有氯化钙型含硼、含锂卤水的开发提供参考。     

Enrichment in unsaturated fatty acids and emulsion droplet size affect the crystallization behaviour of milk triacylglycerols upon storage at 4 °C

Increasing the unsaturated fatty acid (UFA) content in milk fat is of primary importance to improve the long-term health of consumers. However, such changes can affect the crystallization properties of milk triacylglycerols (TAG) and their functional properties. The objectives of this study were to investigate the crystallization properties of milk fat as a function of its FA composition and emulsion droplet size upon storage at refrigerated temperature. UFA-enriched TAG were obtained using cow diet supplemented with linseed oil and compared to control TAG. Homogenization was used to vary the size of emulsion droplets, from 1.7 to 0.2 ??m. The crystallization properties of TAG were studied using synchrotron X-ray diffraction coupled to differential scanning calorimetry. We characterized the coexistence of several solid fat phases with a liquid phase, the characteristics of which depended on the temperature, FA composition and droplet size. The enrichment in UFA from 29 to 51 wt.% led to a decrease in the enthalpy ratio (??H_partial/??H_total) from 64 ± 4 to 54 ± 4% at 4 °C and to the formation of 2 L (41.8 Å) structure with ??₁, ??′₁, and ??′₂ polymorphic forms while 2 L (39.5 Å) and 3 L (56.6 Å) structures with ??₁, ??₂, ??′₁ and ??′₂ polymorphic forms were formed with control TAG. The size of the emulsion droplets also affected the structural and thermal properties of milk TAG. Such experiments increased the knowledge about the crystallization properties of TAG dispersed in emulsion and will be useful for industrial applications and the development of UFA-enriched dairy products with improved nutritional properties.     

Rates of Crystallization of Dried Lactose-sucrose Mixtures

The isothermal crystallization kinetics of glassy lactose/sucrose mixtures were studied at several storage temperatures (close to T_g and T_m). The kinetic parameters implicit in the Avrami equation were determined. Activation energies for transport (E_D) and surface nucleation (W*) were also found and correlated to the molar composition of the lactose/sucrose mixtures. A monotonic increase in the half crystallization time (t_1/z), Avrami index (n), % crystallization per day, activation energy for transport (E_D) and surface nucleation energy (W*) and a decrease in the crystallization velocity constants (K) were related to the increase in the lactose content of lactose/sucrose mixtures.     

零反式脂肪酸涂抹脂基料油酶法酯交换制备研究

利用固定化脂肪酶催化棕榈油硬脂和葵花籽油进行酯交换反应,制备零反式脂肪酸涂抹脂基料油。考察了不同搅拌速度、反应温度、酶加量和反应时间对酯交换反应的影响,并对反应前后油脂的熔点、晶型和结晶速率等结晶行为进行了分析和比较。结果表明:搅拌速度200 r/min,酶加量6%,在70℃下反应3 h为最优的酯交换条件。酯交换产物的熔点大幅下降,晶型主要以β’晶型为主,结晶速率变慢。     

γ-氨基丁酸结晶热力学的研究

研究了γ-氨基丁酸(GABA)的结晶热力学特性,分析了温度、溶剂的组成、pH、杂质等因素对GABA溶解性的影响。结果表明,GABA极易溶于水,25℃时饱和浓度达到774.49g/L,且GABA在水中的溶解性随温度的变化不大。GABA微溶于乙醇,采用水-乙醇复合溶剂可以降低GABA的饱和浓度,在水与乙醇的体积比为1∶4,温度为25℃时GABA的饱和浓度可降低至75.9g/L;酶反应液中杂质的存在会降低GABA的饱和浓度;当pH为7.3时GABA的饱和浓度最小;进一步测定了γ-氨基丁酸酶反应液处理液的介稳区宽度,为酶反应液中GABA的结晶提供了热力学基础。     

Kinetic analysis of isothermal crystallization in hydrogenated palm kernel stearin with emulsifier mixtures

The kinetics of isothermal crystallization of hydrogenated palm kernel stearin (HPKS) with emulsifiers was evaluated by applying the Avrami equation. Effects of five commercial emulsifiers (lecithin, monoglyceride, polyglycerol polyricinoleate, Span 60, and Tween 60) on crystallization behaviors were tested at four different isothermal temperatures (15, 20, 25, and 30 °C). It is shown that, as temperature increases, induction time for HPKS samples generally increased especially from 25 to 30 °C. Meanwhile, different nucleation mechanisms were observed according to Avrami exponent (n) values. The addition of emulsifiers generally accelerated crystallization rate without changing the growth mechanism (plate-like growth) under 25 °C. However, when the temperature increased to 30 °C, n ranged from 1.0 to 5.1, which indicated different nucleation mechanisms induced by different emulsifiers. Avrami constant (k) (indicating the crystallization rate) decreased as the temperature increased except for samples with Span 60. At higher temperatures, values of t_1/2 were significantly higher which reflects the decrease in k at higher temperatures. Crystal microstructures at 30 °C were obtained by using polarized light microscope. Lecithin and Span 60 samples showed large and dense crystals compared with the control sample. Tween 60 sample showed very small crystals which aggregated in a line trend. However, small differences were observed in fractal dimension results except for Tween 60 sample.     

氢化棉籽油等温结晶动力学的研究

用脉冲核磁共振(PNMR)法测定了两种氢化条件下氢化棉籽油的固体脂肪含量(SFC)。根据不同温度下固体脂肪含量随时间的变化绘制等温结晶曲线。等温结晶曲线有两种:双曲线和反曲线。当过冷却度高时,结晶曲线为双曲线;当过冷却度低时,结晶曲线为反曲线。用Avrami方程进行氢化棉籽油的等温结晶动力学分析,结果表明:过冷却度与晶体的成核和生长方式有显著相关性。当过冷却度高时,结晶常数较小,晶体成核和生长速率快;当过冷却度低时,结晶常数较大,晶体成核和生长速率慢。研究氢化棉籽油的结晶行为对人造奶油、起酥油和可可脂替代品基料油的选择有一定的指导意义。     

司盘85对棕榈油结晶过程动力学的影响分析

采用核磁共振仪测定棕榈油及添加0.01%~0.1%司盘85棕榈油的等温结晶行为。采用Avrami方程进一步探究样品的等温结晶动力学,研究司盘85对棕榈油结晶行为的影响。结果表明:棕榈油及添加0.01%~0.1%司盘85棕榈油的Avrami指数在1.422~1.912之间,可知样品的晶体生长为二维;司盘85对棕榈油的结晶过程具有抑制作用,且随着司盘85添加量的增大,其抑制作用增强,表现为结晶速率常数减小,半结晶时间延长。     

Influence of Chemical Composition on the Isothermal Cocoa Butter Crystallization

ABSTRACT: The influence of chemical composition on the isothermal cocoa butter crystallization was investigated quantitatively. Apart from the fatty acid and triacylglycerol profile, the amounts of some minor components (diacylglycerols, free fatty acids, phospholipids, soap, unsaponifiable matter, iron, and primary oxidation products) were determined. With the forward model selection technique, a multiple linear regression model was established, showing the influence of chemical characteristics on the different crystallization parameters of the new model to describe the fat crystallization kinetics as developed by Foubert and others (2002). The ratios of saturated to unsaturated fatty acids and monounsaturated to diunsaturated triacylglycerols have the most important effect on the amount of crystallization, the induction time of the 2nd step of the crystallization process, and the order of the reverse reaction. The more unsaturated fatty acids and the more diunsaturated triacylglycerols, the lower the amount of crystallization; the higher the induction time for the 2nd step of crystallization, the lower the order of the reverse reaction. The amount of diacylglycerols has the most important (negative) influence on the rate constant. Other minor components with a rather pronounced influence on different crystallization parameters are the free fatty acids, phospholipids, and traces of soap.     

Avrami法研究微量司盘85对棕榈油结晶动力学的影响

采用差示扫描量热仪（differential scanning calorimetry,DSC）分析棕榈油及其与司盘85混合物的等温结晶及熔融行为,通过Hoffman-Weeks法计算出样品的平衡熔点。采用Avrami方程进一步研究样品的等温结晶动力学,从而得到与结晶动力学相关的参数。结果表明：DSC分析显示司盘85可明显降低棕榈油的结晶率和成核速率。通过Hoffman-Weeks法和Avrami方程求得的温度数据具有良好的线性关系,表明Avrami方程适用于棕榈油结晶过程的研究,但在结晶后期出现偏离。拟合得到的Avrami指数（n）在2.37～2.77之间,可知样品二维和三维晶体生长同时存在;结晶速率（k）和半结晶时间（t1/2）随着添加剂的添加均变小。