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。     

Crystallization properties of palm oil by dry fractionation

The crystallization, thermal, physical, chemical and morphological properties of palm oil were investigated using differential scanning calorimetry, polarized microscopy, pulsed nuclear magnetic resonance (NMR) and gas chromatography (GC). The palm oil was fractionated into various stearin and olein (with iodine values (IV)>63) fractions by means of a dry fractionation process. During the cooling sequence, samples were taken at regular intervals from the crystallizer and analyzed for their iodine values, chemical compositions and physical behaviour. The physical properties of olein and stearin fractions, such as cloud point, slip melting point and solid fat content, were dependent on the crystallization temperatures. The iodine values of the olein and stearin fractions increased as the crystallization temperature decreased and both fractions started to cloud at lower temperatures. The palmitic acid content of stearin and olein fractions was also affected by the crystallization temperatures.     

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。     

PARAMETERS THAT DETERMINE TRIPALMITIN CRYSTALLIZATION IN SESAME OIL

The crystallization of tripalmitin (TP) in sesame oil (0.98, 1.80 and 2.62% w/v) was investigated under isothermal conditions using a cooling rate similar to the one achieved by industrial crystallizers (1 K/min) and utilizing a modification of the Avrami equation. It was concluded that z, the crystallization rate constant, and the associated energy of activation (Ea) values determined through Avrami's original equation yield erroneous results. Additional results indicated that the increase in supercooling at constant oil phase viscosity (e.g., 5.25–5.5 dynes/cm²) during crystallization, produced a higher degree of nucleation without an appreciable effect on TP crystal size. In contrast, as viscosity of the oil phase decreased at equal supercooling conditions (e.g., 22.0 - 22.5C) the main crystallization process evaluated through z and Ea was crystal growth. It was also concluded that the characteristic crystallization stages of induction time for nucleation, crystal nucleation and growth, and end of crystallization were evident in the viscosity profile of the solid fraction developed during TP crystallization. The predominance of any of these processes (i.e., nucleation or crystal growth) as a function of supercooling and viscosity of the oil phase determines, to a great extent, the rheological profile during crystallization and the final viscosity value of the crystal suspension.     

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。     

植物蜡及液态植物油构建油凝胶的物性研究

以米糠蜡、棕榈蜡、蜂蜡3种食品级植物蜡为凝胶剂,葵花籽油、油茶籽油、亚麻籽油、棉籽油为基料油,构建了植物油基油凝胶,系统分析了油凝胶的外观形态、持油能力、微观结构、硬度、晶型及熔化结晶行为。结果发现,棕榈蜡基油凝胶涂抹性能优良,蜂蜡基油凝胶在三者中具有最高的持油能力。微观分析表明,米糠蜡形成的油凝胶晶体结构较为清晰,呈细长的针状;蜂蜡形成的油凝胶晶体结构最为细小,呈细小的针状;棕榈蜡形成的油凝胶,针型细密,并呈絮状结晶。晶体密度及样品硬度均随凝胶剂质量分数增加而增加。油凝胶的晶型与凝胶剂质量分数、基料油的种类无太大关系,主要取决于凝胶剂的种类。熔化结晶行为表明,凝胶剂种类相同时,随着其质量分数的增加,油凝胶的结晶/熔化峰值温度均升高。     

隔膜压滤机在棕榈油干法分提中的应用

隔膜压滤机用于棕榈油分提过程的固液分离,在过滤完成后,通过压缩介质(水或空气等)依靠隔膜对滤饼压榨、挤干.采用隔膜压滤机,棕榈硬脂硬度提高、棕榈液油得率增加,分离效果好.过滤过程应用自动化控制,操作方便、产品质量稳定.     

棕榈油干式分提工艺结晶回温的原因及解决办法

简要说明了棕榈油干式分提工艺结晶回温的害处,并详细分析了回温的原因。回温是由于RBD棕榈油熔点偏高或偏低,或者是结晶菜单不适合造成的。针对不同的回温原因,分别提出了不同的解决办法:当RBD棕榈油熔点偏低时,结晶菜单主结晶段设置温度应下调、时间应减少;当RBD棕榈油熔点偏高时,结晶菜单主结晶段设置温度应上调,时间应增加;当结晶菜单设置不合适时,可归类于RBD棕榈油熔点偏低或偏高进行调整。     

Separating Tocotrienols from Palm Oil by Molecular Distillation

Crude palm oil contains approximately 1% minor components, including carotenoids and vitamin E (tocopherols and tocotrienols), which contribute to the stability and nutritional properties of palm oil. Palm oil is considered one of the best sources of vitamin E. The vitamin E content in palm oil is unique because it is composed of tocotrienols rather than tocopherols. Palm fatty acid distillate (PFAD) is the volatile organic material recovered as a valuable by-product in the deodorization of palm oil. Several processes have been proposed for recovering tocopherols and tocotrienols from PFAD. For this separation process, it is necessary to develop a processing procedure to extract the valuable tocotrienols and other minor components from PFAD using molecular distillation. Molecular distillation occurs at low temperatures and reduces the problem of thermal decomposition. High vacuum also eliminates oxidation that might occur in the presence of air. The rate of evaporation is controlled by the rate at which the molecules escape from the free surface of the liquid and condense on the condenser. The effects of feed-flow rate and temperature of distillation on extraction of minor components from PFAD are based on concentrations, distribution coefficients, and relative volatilities. The separation of tocotrienols from PFAD approached maximum values at low temperatures and fell drastically as temperature increased. For the optimum conditions for the extraction of tocotrienols with high yield and purity, it is necessary to determine the effect of processing variables on the extraction of minor components (i.e., tocotrienols, α-tocopherol) from the PFAD in terms of concentrations in the liquid and vapor phases, to reveal the behavior of target components in the evaporation process, and to determine the evaporation and volatility properties of tocotrienols and other minor components from PFAD.     

Effect of Lipid Physical State of Palm Derivatives on β‐Carotene Bleaching

This research was addressed to study the effect of lipid physical state on bleaching kinetics of β‐carotene. To this aim, β‐carotene was added to palm oil and palm stearin and the samples were stored at increasing temperatures allowing different degree of crystallization. Phase transition properties of palm derivatives were studied by differential scanning calorimetry and synchrotron X‐ray diffraction, whereas β‐carotene bleaching kinetics were followed by measuring color changes. Bleaching proceeded at comparable rate in palm oil and palm stearin containing systems stored at 20 and ?18 °C, whereas the color changes showed a maximum rate at 4 °C in palm stearin samples and at ?7 °C in palm oil systems. Arrhenius plot clearly highlighted deviations from the linearity underlining the crucial role of lipid physical properties in determining the bleaching rate. The location and the compartmentalization of β‐carotene in the fat lattice could affect its chemical stability.     

Influence of chemical refining process and oil type on bound 3-chloro-1,2-propanediol contents in palm oil and rapeseed oil

The formation of bound 3-chloro-1,2-propanediol (3-MCPD-ester) in oils during chemical refining process was investigated for two palm oils and one rapeseed oil. Additionally, contents of mono- and diglycerides as well as total chlorine and chloride were determined. For all oils the deodorisation step representing one part of the refining process had the main impact on formation of 3-MCPD-esters whereas a direct effect of the other process steps could be neglected. 3-MCPD values in the range of 4–5 ppm for palm oil and 1 ppm for rapeseed oil were found. The chloride content was below detection limit. However, measurable amounts of total chlorine were found in palm oil with the highest 3-MCPD-ester contents. A considerable part of this total chlorine in the refined palm oil was embedded in the 3-MCPD-esters. On the other hand, content of diglycerides as the other potential pre-cursor was between 1% and 10% exceeding the 3-MCPD-ester contents by up to five magnitudes.     

Process development for continuous crystallization of fat under laminar shear

A novel continuous laminar shear structuring crystallizer with a suitable cooling system was designed and built. This is a new method to continuously crystallize edible fat in the desirable polymorphic form from the melt while being uniformly sheared.The machine consists of four main sections: Feed unit, shearing mechanism, cooling system and power unit. In each of these sections specific design considerations are taken into account which makes the process controllable and continuous. The shearing unit is made of two concentric cylinders. The internal cylinder is stationary and has a cooling system inside for temperature control. The outer cylinder rotates to produce a uniform shear in the sample fluid placed in the 1.5 mm gap between the cylinders. The sample’s feed rate is controlled while it is pumped to the gap. The cooling system has three segments and provides an individual temperature gradient for each region.Cocoa butter and a binary mixture of cocoa butter and milk fat were crystallized from the melt under shear and different cooling regimes. A major modification in the samples phase transition behavior was observed; laminar shear induces acceleration of phase transition from less stable polymorphic form to the more stable form, β_V. Moreover, X-ray diffraction patterns clearly showed crystalline orientation of the samples. This machine may open up new avenues for processing and manufacturing chocolate, shortenings and margarine.     

Separating the Role of Particles and the Suspending Fluid for the Flow of Soy Milks

The paper describes a model and a simple experimental method to determine suspension transport properties, separating the role of particles from the suspending fluid. Shear stresses are described as consisting of 2 components: 1st, a shear stress caused by the flow of the suspending fluid and 2nd, a shear stress caused by direct interaction between suspended particles. We show that the determination of these shear stresses of a complex (food) suspension is largely independent of the definition of its suspending fluid. The rheological behavior of soy milks at low and intermediate moisture contents was studied, and results are compared with those obtained previously. The method evidences that the high viscosity of soy milks is predominantly caused by direct particle interaction.     

Process development for continuous crystallization of fat under laminar shear

A novel continuous laminar shear structuring crystallizer with a suitable cooling system was designed and built. This is a new method to continuously crystallize edible fat in the desirable polymorphic form from the melt while being uniformly sheared.The machine consists of four main sections: Feed unit, shearing mechanism, cooling system and power unit. In each of these sections specific design considerations are taken into account which makes the process controllable and continuous. The shearing unit is made of two concentric cylinders. The internal cylinder is stationary and has a cooling system inside for temperature control. The outer cylinder rotates to produce a uniform shear in the sample fluid placed in the 1.5 mm gap between the cylinders. The sample’s feed rate is controlled while it is pumped to the gap. The cooling system has three segments and provides an individual temperature gradient for each region.Cocoa butter and a binary mixture of cocoa butter and milk fat were crystallized from the melt under shear and different cooling regimes. A major modification in the samples phase transition behavior was observed; laminar shear induces acceleration of phase transition from less stable polymorphic form to the more stable form, β_V. Moreover, X-ray diffraction patterns clearly showed crystalline orientation of the samples. This machine may open up new avenues for processing and manufacturing chocolate, shortenings and margarine.     

Crystallization and rheology of palm oil in the presence of sugar

Palm oil is an alternative to partially hydrogenated vegetables oils for fat-based confections given its semi-solid consistency and zero trans fat content. However, its slow crystallization behaviour results in hardening during storage and an objectionable texture. While there are numerous studies on palm oil solidification and storage properties in bulk, the impact of sugar in this context has yet to be reported. In this study, the crystallization and rheology of two commercial palm oils in both bulk and mixed 1:1 (wt.%) with confectioner's sugar were explored over four weeks of storage. The palm oil with the higher diacylglycerol and saturated triacylglycerol content experienced significantly higher solid fat contents and viscous/elastic moduli with storage time. The presence of sugar reduced the solid fat content of both palm oils, but increased their solid-like character, an effect we ascribed to the role of the dispersed sugar on oil viscosity. Principal component analysis on lipid composition identified the key species contributing to these properties. These findings establish a foundation for the optimization and improvement of palm-based confections.     

Influence of diglycerides on crystallisation of palm oil

Palm oil diglycerides and pure synthetic diglycerides of 1,2‐(2,3‐) and 1,3‐dipalmitoylglycerol, dioleoylglycerol and palmitoyloleoyl glycerol were added to purified triglycerides of palm oil. The crystallisation kinetics of the samples were studied by spectrophotometry, NMR analysis of the solid fat content and by X‐ray diffraction of the crystals obtained at 20°C. Palm oil diglycerides inhibited the nucleation process and retarded the crystal growth rate of palm triglycerides. The effect was less pronounced at a higher degree of supercooling. The extent of inhibition depended on the nature of the diglycerides and the concentration. © 1999 Society of Chemical Industry     

Influence of shear on fat crystallization

Processing conditions greatly impact fat crystallization kinetics and growth mechanisms. Recently, there has been increased interest in elucidating the role of shear on fat crystallization. This review provides an overview of fat crystallization under static conditions followed by a summary of the current body of work pertaining to the effects of shear on fat crystallization, namely its effects on nucleation and growth, crystal network formation, polymorphic transitions, and microstructure modification at different length scales. The effects of shear are usually tied to critical shear rates but shear generally enhances nucleation and growth, accelerates crystallization and polymorphic transitions, and can cause orientation and structuring of fat crystal networks.     

制取高不饱和脂肪酸大豆油脂方法的研究

利用结晶、温度回调结晶,将大豆油脂分成富含不饱和脂肪酸的油脂与低不饱和脂肪酸的油脂。通过单因素实验与正交实验,对影响分离效果的主要因素进行了研究,最佳工艺参数为:降温速度5℃.h-1,结晶温度-15℃,结晶时间24h,搅拌速度15r/min。利用温度回调至-5℃的方法,使富含不饱和脂肪酸的油脂产品碘值达到150.2gI2/100g。     

蔗糖形态对氢化棕榈仁油/可可脂混合体系结晶性质的影响

以氢化棕榈仁油/可可脂(质量比9∶1)混合体系为基料油,采用差示扫描量热仪(DSC)考察不同形态蔗糖(结晶糖、糖粉)和卵磷脂对熔化结晶性质的影响。结果表明:未添加卵磷脂时,蔗糖形态对基料油的熔化结晶性质影响不大;添加卵磷脂后,蔗糖颗粒越细,熔化和结晶温度越高;两种形态的蔗糖体系,添加卵磷脂均使结晶温度显著降低。     

An overview of structure engineering to tailor the functionality of monoglyceride oleogels

Monoglyceride (MG)-based oleogelation is an effective strategy to create soft matter structures with the functionality of fats, but with a nutritional profile similar to edible oils. MG oleogels are mainly studied to replace or reduce trans and saturated fats as well as to develop novel products with improved physical and organoleptic properties. The process consists of direct dispersion of MGs into the oil at temperatures above the melting point. This is followed by a cooling period in which the gelator network is formed, entrapping the oil in a crystalline structure. MG composition and concentration, oil type, process temperatures, stirring speed, shear rate during cooling, and storage time play a role in the kinetics of MG crystallization within an MG–oil system, which leads to the formation of lipid materials with different properties. A deep understanding of MG oleogelation processing parameters allows for the tailoring of oleogel properties to meet desirable characteristics as solid fat replacers. This review provides insight regarding manipulating physical process parameters to engineer structures with specific functionality. Furthermore, ultrasound technologies and optimization methodologies are discussed as tools for the production of oleogels with specific properties based on their potential use as well as the development of bi- and multi-gelators oleogels using MGs. Finally, the food applications in which MG oleogels have been tested are summarized in addition to the identified gaps that require further research.