Effect of food emulsifiers on crystal structure and habit of stearic acid

Several food emulsifiers have been found to serve as crystal structure modifiers for stearic acid crystallized from various organic solvents. Stearic acid that usually precipitates under appropriate crystallization conditions as the B- form is converted into the C- form when 1- 5% of sorbitan esters or ethoxylated sorbitan esters of fatty acids are present in the solution. Other emulsifiers such as polyglycerol esters, bdsubstituted monoglycerides and sucrose esters of fatty acids consisting of bulky hydrophilic groups are also effective emulsifiers in preserving the C- form of the crystallized stearic acid. The active emulsifiers modify the external crystal habit of stearic acid. Mass spectrograph analysis indicates that sorbitan monostearate (Span 60) is precipitated with the stearic acid.     

Formation and investigation of microemulsions based on jojoba oil and nonionic surfactants

The properties of jojoba oil make it uniquely suited as a raw material for the cosmetics industry. Water-based, thermodynamically stable preparations of jojoba oil are essential in many formulations. New microemulsions were prepared based on jojoba oil and different nonionic surfactants, namely polyoxyethylene-(ethylene oxide)₁₀-oleyl alcohol (Brij 96V) and ethoxylated sorbitan esters (Tweens). The effects of the surfactants and of primary alcohols as cosurfactants on the isotropic regions of the phase diagram were elucidated. It was found that, up to a certain cosurfactant chain length, the isotropic region expanded considerably as chain length increased. The size of the isotropic region also increased as a function of the ethylene glycol content of the aqueous phase in microemulsions based on ethoxylated alcohol but shrank when ethylene glycol was included in microemulsions prepared with ethoxylated sorbitan esters. Secondary structural phase transitions from water-in-oil to bicontinous and to oil-in-water structures (as determined by measuring conductivity and viscosity) were found to be related to jojoba oil content. Dynamic light scattering and small angle X-ray scattering studies established that incorporation of jojoba oil into Brij 96V micelles caused micellar transformation from elongated to spherical droplets and a decrease in the aggregation number.     

Span 60对3-甲基吡啶电氧化的影响

通过循环伏安曲线测定,考察了Span 60(山梨糖醇酐单硬脂酸酯)对3-甲基吡啶电氧化的影响。正交实验确定的最佳反应条件是:n(3-甲基吡啶)/n(硫酸)=0.4,添加高于或接近临界胶束浓度的Span 60,反应温度15℃,阳极电位1.9~2.0 V,电解电量为理论电量的10%;其选择性可达85.46%,电流效率为48.69%,电流密度提高300 mA/cm2,并根据最佳反应条件进行外循环放大实验,其结果与小试基本相同。在选定的实验范围内,Span 60对3-甲基吡啶电氧化有明显的促进作用,有应用前景。     

Statistical development of improved emulsification systems for bakers shortenings

Statistical design methods were used to observe trends of surfactant functionality for specific cake and icing quality attributes. A two-level factorial design was used in the initial screening activity. within the favorable region, a rotable central composite design was used to more accurately detect surfactant effectivenness. It was found that sorbitan monostearate improved cake volume and tenderness but reduced icing aeration. Polysorbate esters increased icing aeration but had relatively little effect on cake volume and tenderness. Based on the information obtained, individual blends of emulsifiers were developed to suit specific needs.     

Polymorphic transitions of mixed triglycerides,SOS, in the presence of sorbitan monostearate

The polymorphic behavior of 1,3-distearoyl-2-oleo glycerol (SOS) has been investigated in the presence of a selected food emulsifier, sorbitan monostearate. Five polymorphs, named α, γ, pseudo-β′, and β₂, and β₁ were crystallized and identified by both x-rays and DSC. Each polymorph was treated using two selected protocols—the “screen cycle” and the “aging cycle.” It has been demonstrated that sorbitan monostearate, when present in the molten fat, will significantly retard the α to γ transition during both the screen cycle and the aging cycle. A retardation effect was not detected for the γ to pseudo-β′ transition (during the screen or the aging cycle). The emulsifier that is inserted into the fat behaves as a conventional impurity, causing significant reduction in the melting temperatures of each polymorph. As a result, the fat tends to melt prior to its transition. The behavior of SOS in the presence of the sorbitan monostearate is therefore different than that of SSS (tristearin), and may explain, in part, the absence of the strong blooming transition to high melting polymorph that occurs when the fat is rich in SOS. This behavior can also shed some light on the behavior of cocoa butter in the presence of sorbitan esters.     

Reconsideration of polymorphic transformations in cocoa butter using the DSC

Cocoa butter was crystallized in the differential scanning calorimeter (DSC) in the presence and the absence of sorbitan monostearate at different cooling rates. The solidification and fusion curves were recorded. It was found that cooling rate affects enthalpies and temperatures of phase transitions. The very slow cooling rate causes a significant decrease in crystallization enthalpy, suggesting that fractionation of glycerides occurs under these conditions. In the presence of sorbitan monostearate 5%, cooling and heating curves of cocoa butter are sharper, the solidification point is higher and the fusion point is slightly lower. Further, in the presence of sorbitan monostearate both crystallization and fusion enthalpies are lower than in pure cocoa butter. The presence of the emulsifier seems mainly to promote the fractional crystallization. Fusion curves after different periods of isothermal crystallization suggest that higher polymorphic forms differ in chemical composition from lower ones, and that the presence of sorbitan monostearate affects the fractionation in the fat.     

Effect of Surfactants on the Polymorphic Behaviour of Hydrogenated Canola Oil

The effect of a number of surface active lipids on the polymorphic behavior of hydrogenated Canola oil was investigated. Compounds tested included sorbitan tristearate, sorbitan trioleate, sorbitan monostearate, sorbitan monopalmitate, sorbitan trilaurate, and Admul WOL. Polymorphic transition was measured by X-ray diffraction patterns and crystal growth by polarized light microscopy. Some of the surfactants were effective in delaying the transition to the β-polymorphic form. The most effective compound was sorbitan tristearate. Differential scanning calorimetry was used to demonstrate recrystallization at heating rates of 5 and 10°C per minute. It is suggested that some surfactants have the ability to become incorporated into the crystal lattice and prevent or delay the transformation to the β-form. To be effective, the surfactant should co-crystallize with the fat. Surfactants with low melting points were not effective.     

Crystal structure modifications of tristearin by food emulsifiers

The effect of several emulsifiers as crystal structure modifiers of tristearin has been investigated. The less thermodynamically stable modification, named a, is preserved when 1–10% of sorbitan monostearate was added before allowing the molten tristearin to cool and crystallize. Several other emulsifiers have been tested and it has been found that the combination of bulkiness of the hydrophilic groups with the right lengths of the hydrophobic chains of a given emulsifier is necessary to preserve the a-modification. Liquid emulsifiers and those having a pronounced hydrophilic character are not efficient as modifiers. The emulsifier has been shown to be incorporated into the tristearin during crystallization from solvent without an immediate effect, but it affects subsequent behavior upon melting and resolidification.     

Fluid shortening medium

Because of an apparent interest in a liquid shortening with good baking properties, a program for the development of such a product was instituted. Past efforts to accomplish this by dissolving or suspending emulsifiers in vegetable oils had not had notable, success. In this instance it was decided to use a different approach, that of making an emulsion in water, in trying to impart desirable baking properties to vegetable oils. It was also desired that a fluid product be produced from animal or hydrogenated vegetable fats, using the same approach. Shortening emulsions were prepared by using sorbitan monostearate, polyoxyethylene-2-sorbitan monostearate, and mono-and diglycerides as dual-purpose emulsifiers to provide a stable emulsion and impart good baking properties. Emulsions were prepared and tested and found capable of utilizing all common shortening base-stocks in baking. In most cases also excellent results in cream icings were obtained. The most serious problem which occurred was the tendency of emulsions made with animal fats to become plastic. A study of the causative factors was made, and the conclusion was reached that a stable fluid products could be obtained through careful selection of ingredients. Important factors which affected emulsion viscosity were monoglyceride level and hardness; the ratio of sorbitan monostearate to polyoxyethylene sorbitan monosterate, and their level; and the shortening basestock used. The stability of the emulsions was studied and the conclusions were reached that aging did not affect baking quality significantly although optimum effectiveness was reached apparently several days after preparation; the emulsions were not particularly subject to oxidative rancidity; bacteria and mold counts increased only slightly during storage periods as long as two months at room temperature. An unexpected result was the markedly-improved performance when the shortening was pre-emulsified as shown by the baking data and icing quality factors which were reported.     

New Approach to Structure–Property Correlations of Different Films of Sorbitan Esters and Their Self-Assembly into Viscoelastic Monolayers

This publication is focused on the structural origin of viscoelasticity in Langmuir monolayers. To improve the understanding of the structural origin of viscoelasticity of surfactant films, we systematically studied interfacial films of different sorbitan esters with saturated (Span 60 and 65) and unsaturated (Span 80 and 85) paraffin chains by means of surface rheology, Langmuir isotherms, X-ray reflectometry (XRR), and Brewster angle microscopy (BAM). The results of two-dimensional shear rheological measurements revealed the existence of temporarily cross-linked networks. In dynamic BAM experiments, we observed a swinging motion of the monolayers as a result of a sudden externally initiated mechanical perturbation. The viscoelastic film response, which relaxed with time as the external force vanished, could be traced back to the presence of foam-like supramolecular structures that interlinked solid-condensed domains. The temperature dependence of the elastic response implied that the solid domains decomposed at temperatures close to the bulk melting point of Span 60 and Span 65. We concluded that insoluble surfactants formed solid domains at the interface, which were linked with each other by nonsolid areas, giving viscoelastic films. These newly discovered insights into coherent film formations could provide new opportunities for designing mechanically stable surfactant interfaces.     

Emulsifiers derived from linseed oil and their potential use in coatings

In the development of a stable linseed oil emulsion paint, a series of emulsifiers were prepared from linseed, oil and its fatty acids and alcohols: (a) linseed monoglycerides, (b) mono-and dilinseed fatty sorbitan esters and a mixed ester obtained by the transesterification of linseed oil with sorbitol, (c) polyoxyethylene ether adducts formed by reacting, ethylene oxide with these sorbitan esters, and (d) linseed polyoxyethylene ether made by ethoxylation of linseed alcohols. Another series of surfactants was prepared by esterifying a polyoxyethylene ether of sorbitol with various amounts of linseed fatty acids. Conditions of preparation and pertinent physical, and chemical properties of the emulsifiers are given. Some of these emulsifiers demonstrated filmforming properties. Combinations were formulated into linseed oil emulsion paints with and without zinc oxide. Paints containing zinc oxide have been relatively stable in viscosity for about 2 yr.     

The determination of sorbitan monostearate in cake mixes and baked cakes

A method has been developed for the determination of sorbitan monostearate (SPAN 60^®, Atlas Chemical Industries, Inc.) in cake and cake mixes. The method involves extraction of sorbitan monostearate from the sample, partial purification of the extract by silica gel chromatography, recovery of the extract polyol and analysis by either gas or paper chromatographic procedures. The isosorbide moiety of the emulsifier is measured by gas chromatography. In the paper chromatographic procedure, the 1,4-sorbitan fraction is isolated, oxidized with periodic acid and the absorbance of the formaldehyde-chromotropic acid color is measured. The sorbitan monostearate content of the sample is calculated using the appropriate conversion factor obtained by analyzing known solutions of polyols from the product. The method was applied satisfactorily to several samples of baked white cake, yellow and chocolate cake mixes. Analyses of blank cakes showed that there are no interferences from other constituents of cake and that a blank cake is unnecessary in the application of the method.     

聚氧乙烯山梨醇酐单硬脂酸酯的合成与应用

以山梨醇和硬脂酸为原料,经脱水、酯化、醚化制得聚氧乙烯山梨醇酐单硬脂酸酯,它具有良好的活性,已广泛应用于食品、日化、医药、机械加工等领域。     

Preparation of water soluble Am–AA–SSS copolymers by inverse microemulsion polymerization

Inverse microemulsion copolymerization of acrylamide (Am), acrylic acid (AA), and sodium 4-styrenesulfonate (SSS) initiated by redox initiators composed of ammonium peroxodisulphate (APS) and sodium bisulfite, and stabilized by the mixed emulsifier system sorbitan monooleate (Span-80) and polyoxyethylene sorbitan monooleate (Tween 80) were examined as a function of the combination of hydrophilic (Tween 80) and hydrophobic (Span 80) emulsifiers, reaction temperature, AM/AA mass ratio, SSS concentration, and initiator concentration. The physicochemical and thermal properties and the structure of this copolymer were also determined and discussed. The reaction rates for all runs of the experiments exhibited two intervals, which were typical of microemulsion polymerization. The copolymer had only one glass transition temperature of 115.5 °C, indicating a random structure.     

Raman spectroscopy of the polymorphic forms and liquid state of cocoa butter

Raman spectroscopy was used to characterize the polymorphs and liquid state of cocoa butter, with emphasis placed on the evolution of the ester carbonyl stretching region (1800–1700 cm^?1), along with complementary analysis and comparison of the Raman‐active C? C (1200–1000 cm^?1), C?C (1660 cm^?1), C? H (3000–2700 cm^?1) and CH₂ (1500–1250 cm^?1) vibrational modes. Unique Raman signatures were obtained for all cocoa butter polymorphs, with their identity confirmed using DSC and XRD. The ester carbonyl region permitted polymorph discrimination due to differences in the number of modes, their relative frequencies and their full‐widths at half‐maximum. The C? C stretching modes, which provided insight into the trans/gauche content, were polymorph‐independent. C? H stretching generally increased with polymorph stability, indicating the dominance of antisymmetric C? H methylene vibrations as the cocoa butter crystal lattice became more ordered. The change in the intensities of the C? H stretching bands used to probe the order–disorder transition of forms IV, V and VI hinted at pre‐melt structural changes mostly in forms IV and V. Overall, Raman spectroscopy clearly demonstrated that the different functional groups studied could be characterized independently, allowing for the understanding of their role in cocoa butter polymorphism. Practical applications : Fat bloom is the unwanted, uncontrolled re‐crystallization or polymorphic transition of CB form V crystals into form VI normally caused by the migration of lower‐melting fats (e.g. in centre‐filled products) and/or temperature fluctuations during storage. In its mildest form, it appears as an overall dulling of the chocolate surface. In its extreme form, the appearance of the chocolate deteriorates significantly with the development of distinct white patches. Though forms V and VI can be clearly distinguished via XRD, we present evidence that Raman spectral characterization of the ester carbonyl stretching (1800–1700 cm^?1), C? C (1200–1000 cm^?1), C?C (1660 cm^?1), C? H (3000–2700 cm^?1) and CH₂ (1500–1250 cm^?1) vibrational modes yields distinct liquid–solid and polymorph‐dependent differences in CB. From a practical standpoint, the unique signatures associated with forms V and VI offer novel possibilities in the study of fat bloom formation, such as the development of predictive tools.     

Stability of Dye Dispersions in the Presence of Some Eco-Friendly Dispersing Agents

The stability of dye dispersions in the presence of ethoxylated sorbitan lauryl and oleyl esters were reported and compared with dye dispersions containing a conventional dispersing agent, i.e. naphthalene sulfonic acid methylene-bis sodium salt (NSAB). The optimum operating conditions obtained using a central composite design and stability of dye dispersions were evaluated by a turbidimetry method. Results showed that the dose of surfactants and the temperature of operation were important factors in preparing stable dye dispersions. Also, the best conditions for preparing dye dispersions were as follows: dose of surfactant 0.05 g, temperature 25 °C and time 5 min. In addition to, findings indicated that both of the used surfactants had better performance in dispersing the dyes in water. However, ethoxylated sorbitan oleate had better efficiency relative to other used dispersing agents. The performance of both sorbitan esters were compared with NSAB. The results indicated that they can create stable dye dispersions in aqueous media and have approximately the same effectiveness with NSAB. In this series, although oleate ester had a better performance than the laurate, the difference in performance of using dispersing agents was not significant. This finding was confirmed by the results of the particle size analysis of dye dispersions.     

Influence of Fatty Acid Moieties of Sorbitan Esters on Polymorphic Occurrence of the Palm Mid‐Fraction

The influence of chain length and subcell packing of fatty‐acid moieties in sorbitan esters (SE) on the polymorphism of the palm midfraction (PMF) was examined. SE with different fatty‐acid moieties (sorbitan tripalmitate; sorbitan tristearate [STS]; and sorbitan tribehenate [STB]) were blended with PMF and PMF polymorph formation was examined using synchrotron radiation X‐ray diffraction and differential interference contrast microscopy. PMF without additives was crystallized in the β′ form under the isothermal condition at 22 °C; however, the addition of STS, which forms an α subcell structure, promoted the crystallization of PMF in the α form. In contrast, crystallization of PMF in the β′ form was accelerated by the addition of STB. These results showed that when the chain length of the fatty‐acid moiety between fat and emulsifiers was similar, the crystallization of PMF in the α form was promoted by the α subcell packing in STS crystals that were nucleated prior to PMF crystallization. In contrast, STB crystals, which have an α subcell packing, accelerated the crystallization of PMF in the β′ form because of the large difference between the chain lengths of STB and PMF. Therefore, structural similarities in both the chain length and the subcell packing are essential features that regulate the template effect, and the promotion of the crystallization of PMF in the β′ form by the addition of STB was caused by heterogeneous nucleation.     

Argan oil-in-water emulsions: Preparation and stabilization

We prepared stable oil-in-water emulsions of argan oil with two different types of mixtures of nonionic emulsifiers. Three different types of oil (Israeli argan oil, Moroccan argan oil, and soybean oil) were emulsified with mixtures of Span 80 and Tween 80. The optimum HLB value for argon oil was 11.0 (±1.0). The argan oil-in-water emulsions were stable for more than 5 mon at 25°C. Synergistic effects were found in enhancing stability of emulsions prepared with sucrose monostearate. The origin of the oil and the internal content of natural emulsifiers, such as monoglycerides and phospholipids, have a profound influence on its interfacial properties and on the stability of the argan oil-in-water emulsions.     

一种测定乳状液稳定性的简便有效的新方法

An innovational test method was developed on the basis of redefinition of the emulsion stability. The stability was characterized by relative volume percentage of disperse phase demulsified thoroughly from the top part and the bottom part of an emulsion sample, each weighting the same amount, after being settled for a given time at constant temperature. Three series of emulsions were prepared and tested successfully, which were emulsions of paraffin oil and water stabilized with polyoxyethylene lauryl ether series (AEO3 and AEO9) at various HLBs,and emulsions of rapeseed oil and water stablized with sorbitan monoleate (Span80) and each of polyoxyethylene(20) sorbitan carboxylic esters (Tween20, Tween40, Tween60, Tween80 and Tween85) at different HLBs. It proved that this method is especially workable while the boundaries are opaque in a wide range of HLBs and is capable of offering an accurate optimum HLB.     

工艺参数对层状液晶乳液结构的影响

讨论了由聚氧乙烯醚失水山梨醇脂肪酸酯、失水山梨醇脂肪酸酯、直链脂肪醇和挥发性物质组成的层状液晶乳液的制备过程中乳化时原料的加入顺序、乳化时间、冷却时搅拌速度及冷却时间对乳液的形态(脂质体结构,洋葱结构),特别是对乳液颗粒的粒径及粒径分布的影响。结果表明:乳化过程的时间对粒径的分布无明显影响;将水加入到含表面活性剂的油相中有利于形成完整结构的液晶乳液;冷却过程中的搅拌速度及搅拌时间对粒径的影响最大,为了得到较大颗粒为主的粒径分布,较佳冷却条件是搅拌速率在1 500 r/min、冷却60 min;慢速冷却有利于形成层间距较大的层状液晶,快速冷却易形成层间距略小的层状液晶。