Edible oleogels as solid fat alternatives: Composition and oleogelation mechanism implications

The growing awareness of the adverse health effects of trans-fats and saturated fats are driving researchers to seek healthy alternatives. A promising strategy to structure liquid oil, called oleogelation, has been a subject of great interest. In the development of oleogels, highly unsaturated oils can be structured through different gelation mechanisms by varying structuring agents (e.g., polymeric or low molecular weight oleogelators). Due to their potential to reduce saturated fat in food products while also providing solid texture without changing the oil's chemical composition and nutritional values, oleogels have been introduced into various products (meat, spread, and confectionary) as alternatives to traditional solid fats. However, the shortcomings of oleogels cannot be ignored, such as the softer texture and the poorer plasticity than traditional solid fat. As the physicochemical properties and functionalities of oleogels are highly dependent on their composition and structuring mechanism, it is possible to obtain a product with desirable functionality by choosing a suitable oleogelator or oil phase. Thus, comprehensive and detailed knowledge regarding the role of oleoglarors, oil phase, and oleogelation mechanism on oleogelation is needed. This review primarily focuses on published information within the last decades addressing how the composition and oleogelation mechanism affect the structure and functionality of oleogels and oleogel-based products. The factors affecting the oil gelation are summarized concerning three aspects: (i) oleogelator (chemical composition and molecular structure); (ii) oil phase (TAG composition and minor component); and (iii) oleogelation mechanism. Finally, the future perspectives toward oleogels are highlighted. This review aims to deepen the understanding of oleogelation and the rational design of oleogel-based products.     

基于作用力探究凝胶因子与油凝胶之间的构效关系研究进展

近10年来,随着消费者对膳食中减少饱和脂肪酸和消除反式脂肪酸需求的提高以及相关部门要求取缔反式脂肪酸规定的制定,利用凝胶因子结构化植物油形成油凝胶的研究日益增多。诸多研究表明,植物油性质和凝胶因子种类对油凝胶理化性质有显著影响。本文概述了植物油对油凝胶的影响,从诱导形成油凝胶的3 个主要作用力：范德华力、氢键、π-π堆积的角度综述了凝胶因子与油凝胶之间的构效关系,为选择与合成一系列高效、价廉的食品级凝胶因子提供思路。     

蛋白基乳液模板法构建油凝胶的研究进展

传统塑性脂肪带来健康问题,液态油固化成为构建零反式、低饱和脂肪酸塑性脂肪替代品的新策略。蛋白质是优质的食品营养组分,是来源广泛的可再生资源,具有独特的界面特性。为扩大蛋白资源的应用范围及促进功能性油脂的开发,对蛋白质的结构化及蛋白基乳液模板法构建油凝胶(结构化油脂)研究进展进行了综述,同时介绍了蛋白基乳液模板法构建的油凝胶的应用。蛋白质在一定条件下可作为凝胶剂固化液态油;蛋白基乳液模板法构建油凝胶具有安全性高、对环境污染小等优点。采用蛋白基乳液模板法构建的油凝胶可应用于替代传统塑性脂肪、荷载生物活性成分方面。     

巴西棕榈蜡和单甘酯复配比对高油酸葵花籽油凝胶油结构和特性的影响

以高油酸葵花籽油为基料油,通过向其添加不同质量比的凝胶剂巴西棕榈蜡（carnauba wax,CW）与单甘酯（monoglyceride,MG）制备凝胶油。固定凝胶剂浓度为5%,探讨不同CW与MG的复配比对制备的高油酸葵花籽油凝胶油微观形态、凝胶晶型、热力学性质、硬度、持油性以及固体脂肪含量（solid fat content,SFC）的影响。结果表明:MG没有影响CW的熔化行为,二者没有形成共结晶,出现了偏晶现象,当CW与MG复配比为9:1时,MG晶体的存在促进了CW的结晶,同时CW的存在会抑制MG晶体的多晶态转变,提高体系的储藏稳定性;少量MG的加入显著降低了CW凝胶油的硬度（P<0.05）,当二者复配比为5:5并随着MG含量的增多和CW含量的减少,体系硬度显著增大（P<0.05）,在1:9时达到最大硬度137.33 g;MG的加入显著提高了CW凝胶油的持油性（P<0.05）,二者复配比为5:5时体系持油性最佳达到100%;CW与MG复配比为3:7时凝胶油在30~37.5 ℃的SFC明显低于CW和MG凝胶油,此时MG的加入对体系口感的改善起到了正向作用。     

核桃油基油凝胶的制备及特性研究

为探究3种不同凝胶剂体系制备的核桃油基油凝胶的差异性,同时研究冷却温度对油凝胶结构特性的影响。使用单硬脂酸甘油酯、谷甾醇/谷维素、谷甾醇/卵磷脂3种凝胶剂制备油凝胶,测定其质构特性、流变性、持油性、化学键的相互作用以及色度;设置不同冷却温度(-80、-20、4、25℃)的油凝胶实验组,测定样品结构性质。结果显示,3种油凝胶体系内部分子间作用力不同,色度及各种结构性质之间差异显著,冷却温度为4℃时,油凝胶的持油率最大为(81.46±0.87)%,硬度较为适中为(46.5±5.1)g。说明核桃油凝胶可满足塑性脂肪涂抹性的要求,控制结晶温度可改变油凝胶的结构性质。     

肉桂酸基油凝胶及其乳液的制备及理化性质表征

选择玉米油为溶剂,肉桂酸为凝胶剂制备油凝胶,探究其流变学、质构、持油性、热力学特性及凝胶剂晶体形态;以油凝胶为分散相,制备油凝胶乳液（O/W型）,分析其粒径、流变学、稳定性等物理性质。结果表明：肉桂酸临界成胶质量分数为4%,4?℃条件下存放的油凝胶持油性较常温条件下更好;肉桂酸质量分数越大的油凝胶硬度越大,热稳定性越好;肉桂酸在油凝胶中呈现随机分布的长纤维状聚集体;油相质量分数为10%～20%时,油相含量越低,其乳液粒径越小、黏度越低、物理稳定性越好。油凝胶在常温下稳定性较差,而油凝胶乳液在常温下能保持良好的稳定性,有益于其在食品工业领域的研发与应用。     

Influence of wax type on characteristics of oleogels from camellia oil and medium chain triglycerides

Camellia oil (CO) and medium chain triglycerides (MCTs), characterised by different carbon chain lengths, were gelled using beeswax (BW), candelilla wax (CLW) and carnauba wax (CRW). Critical concentrations, oil-binding capacity (OBC), textural parameters, thermal properties, microscopic properties and infrared spectra were used to evaluate their differences. The carbon chain length of oil sources showed different results for the critical concentration of the three wax-based gel oils at 25 °C, and the oleogel of MCT and CLW exhibited a minimum value (1%). The oleogels formed from CO and waxes with wax esters as the main components (BW and CRW) exhibit significantly lower OBC and textural value than the oleogels made from MCT with BW and CRW. Meanwhile, this is corroborated with the thermal behaviour and crystal morphology, and distribution of the oleogels. However, no differences in crystal types and generation of new functional groups were observed by X-ray diffraction and Fourier-transform infrared spectrometer, suggesting that the differences in the properties of wax-based oleogels with different carbon chain lengths are attributed to the interactions between the waxes and the oil sources (physical interaction).     

油脂品种对肉桂酸基油脂凝胶形成及性质的影响

菜籽油、玉米油和亚麻籽油为基料油添加肉桂酸,经加热搅拌、冷却静置后形成油脂凝胶。研究油脂品种对油脂凝胶临界成胶质量分数、持油性（oil binding capacity,OBC）、硬度、固体脂肪含量（solid fat content,SFC）、凝胶晶型及微观结构的影响。结果表明,油脂品种对油脂凝胶临界成胶质量分数无影响,临界成胶质量分数均为4%;对OBC有一定的影响,且随肉桂酸质量分数的增加油脂凝胶OBC明显增强;菜籽油油脂凝胶硬度最小,亚麻籽油油脂凝胶硬度最大;对SFC的影响为菜籽油油脂凝胶＜玉米油油脂凝胶＜亚麻籽油油脂凝胶。同时,晶型分析表明3?种油脂凝胶主要晶型均为β和β′。通过偏光显微镜观察出3?种油脂凝胶的晶体结构及晶体分布差异明显,说明油脂品种对油脂凝胶的微观结构有显著影响。     

基于蜂蜡油凝胶的植物奶油制备与性质表征

考察影响蜂蜡油凝胶和基于蜂蜡油凝胶的植物奶油的理化性质的关键因素。以玉米油为油相,蜂蜡为凝胶剂,添加不同的小分子乳化剂（失水山梨醇脂肪酸酯、卵磷脂）制成油凝胶;油凝胶与水混合,通过乳化法制得植物奶油。理化性质表征发现,蜂蜡-卵磷脂油凝胶和蜂蜡-司盘40油凝胶的持油力均能达95%以上,持油效果较好;而乳化剂的质量分数和贮藏温度均会对油凝胶的硬度产生影响：乳化剂质量分数越高,贮藏温度越低,油凝胶的硬度越低;综合考虑蜂蜡油凝胶的质构特性以及持油力,冷藏条件下,乳化剂质量分数为1%的蜂蜡油凝胶综合性能较好。同时,乳化剂的质量分数和贮藏温度也会对植物奶油的流变特性产生影响：乳化剂质量分数越高,贮藏温度越低,植物奶油的黏弹性和稳定性越好;乳化剂的加入还可以大大改善植物奶油的持水力;整体而言,冷藏条件下,乳化剂质量分数为2%的植物奶油综合性能较好。本课题制备的植物奶油具有成为黄油及奶油替代品的潜力,可以为消费者提供更加健康的食品原料。     

Synthesis,physicochemical properties,and health aspects of structured lipids: A review

Structured lipids (SLs) refer to a new type of functional lipids obtained by chemically, enzymatically, or genetically modifying the composition and/or distribution of fatty acids in the glycerol backbone. Due to the unique physicochemical characteristics and health benefits of SLs (for example, calorie reduction, immune function improvement, and reduction in serum triacylglycerols), there is increasing interest in the research and application of novel SLs in the food industry. The chemical structures and molecular architectures of SLs define mainly their physicochemical properties and nutritional values, which are also affected by the processing conditions. In this regard, this holistic review provides coverage of the latest developments and applications of SLs in terms of synthesis strategies, physicochemical properties, health aspects, and potential food applications. Enzymatic synthesis of SLs particularly with immobilized lipases is presented with a short introduction to the genetic engineering approach. Some physical features such as solid fat content, crystallization and melting behavior, rheology and interfacial properties, as well as oxidative stability are discussed as influenced by chemical structures and processing conditions. Health‐related considerations of SLs including their metabolic characteristics, biopolymer‐based lipid digestion modulation, and oleogelation of liquid oils are also explored. Finally, potential food applications of SLs are shortly introduced. Major challenges and future trends in the industrial production of SLs, physicochemical properties, and digestion behavior of SLs in complex food systems, as well as further exploration of SL‐based oleogels and their food application are also discussed.     

Effects of monoglyceride content,cooling rate and shear on the rheological properties of olive oil/monoglyceride gel networks

Functionality of conventional fat spreads can be achieved without hydrogenation by the formation of stable network structures upon cooling of mixtures of monoglycerides (MGs) and vegetable oils from the melt. Such mixtures are healthy substitutes for margarine and butter. The effects of MG content, cooling rate and shear on the temperature ramp, mechanical spectra and hardness of olive oil/MG gel networks were investigated. A minimum MG volume fraction was necessary for formation of a gelled network, but this concentration was less than that needed for a space‐filling network structure. Onset of gel network or structure formation was indicated by a sudden divergence in value of the elastic modulus G′. The temperature at onset of structure formation, T_o, final G′ value and network hardness all increased with increase in MG content. High cooling rates led to low final G′ values but harder networks, and vice versa. Maximum gel network development occurred when moderate shear (about 300 s^?1) was applied at incipient gelation. Copyright © 2004 Society of Chemical Industry     

Monoglyceride organogels developed in vegetable oil with and without ethylcellulose

We used two commercial monoglycerides (MGs) with different composition (SKB, ≈ 79% glycerol monostearate and ≈ 12% glycerol monopalmitate; PKB, ≈ 47% glycerol monostearate and 47% glycerol monopalmitate) to develop organogels [2% and 8% (wt/wt) MG content]. The objective was to investigate the effect of shearing (SH) and the presence of 6% ethylcellulose (EC) as factors to limit the sub-α to β polymorphic transition of MG, and the subsequent crystals agglomeration that results in deleterious effect on the organogel's mechanical and oil-binding properties. The results showed that under static conditions (ST) both type of MG developed organogels (OG), but their structure, measured as the complex modulus (G*), was weak particularly in the organogels formulated with PKB at 2%. Nevertheless, the OG-ST had higher strength and lower oil loss than the OG-SH. The X-ray analysis showed that the use of shear during organogelation reduced the time at which the sub-α to β polymorphic transition occurred in both the SKB and the PKB oleogels. Additionally, shearing seemed to hinder the formation of well-organized microplatelet structure, and from there the lack of gelation in the 2% OG-SH and the higher oil loss of the 8% OG-SH compared with their static counterparts. Independent of the concentration of SKB and PKB, the presence of EC resulted in organogels with higher G* than that for OG-ST without EC. This, in spite the EC concentration used was below the critical concentration for vegetable oil gelation. The results showed that EC slowed the rate for the sub-α to β polymorphic transition in the MG organogels. Thus, irrespective of the type of MG and the concentration used, during 14 days of storage at 15 °C the OG-EC systems showed a lower oil loss as a function of time than the corresponding organogels developed without EC. This was particularly evident in the organogels formulated with SKB and those formulated with 8% of MG. We suggest that EC limits the molecular mobility in the MG organogels, and therefore, slows the sub-α to β polymorphic transition and the subsequent β crystals' agglomeration. The results showed that there is a synergistic interaction between MG and EC that result in organogels with higher viscoelastic properties and lower oil loss than those observed in MG-organogels without EC.     

Synergistic effects of oleogelators in tailoring the properties of oleogels: A review

Conventional solid fats play a crucial role as an ingredient in many processed foods. However, these fats contain a high amount of saturated fats and trans fats. Legislations and dietary recommendations related to these two types of fats set forth as a consequence of evidence showing their deleterious health impact have triggered the attempts to find alternate tailor-made lipids for these solid fats. Oleogels is considered as a novel alternative, which has reduced saturated fat and no trans fat content. In addition to mimicking the distinctive characteristics of solid fats, oleogels can be developed to contain a high amount of polyunsaturated fatty acids and used to deliver bioactives. Although there has been a dramatic rise in the interest in developing oleogels for food applications over the past decade, none of them has been commercially used in foods so far due to the deficiency in their crystal network structure, particularly in monocomponent gels. Very recently, there is a surge in the interest in using of combination of gelators due to the synergistic effects that aid in overcoming the drawbacks in monocomponent gels. However, currently, there is no comprehensive insight into synergism among oleogelators reported in recent studies. Therefore, a comprehensive intuition into the findings reported on synergism is crucial to fill this gap. The objective of this review is to give a comprehensive insight into synergism among gelators based on recent literature. This paper also identifies the future research propositions towards developing oleogels capable of exactly mimicking the properties of conventional solid fats to bridge the gap between laboratory research and the food industry.     

Effect of meibomian gland morphology on functionality with applied treatment

PurposeTo determine how Meibomian gland (MG) morphology affects MG function by means of gland expression with the effect of treatment.MethodsFifteen patients (aged 31.6 ± 13.1 years) from a dry eye clinic diagnosed with MG dysfunction had their 365 lower lid MGs visualised with a slit-lamp biomicroscopy. Using infrared meibography (Oculus K5m), MG length, width and tortuosity were objectively measured. Each MG was expressed and the meibum graded (0=clear fluid, 1=cloudy fluid, 2= particulate fluid, 3=inspissated, or 4 = no expression) to determine its functionality. Participants had functionality repeated each time following a sequence of a warm compress, debridement, and forcible expression after 5 min.ResultsJust over 10 % of complete length MGs gave clear expression, while about 5% did not express at all, with most expressed meibum being particulate in nature. In contrast, the majority of partial length glands gave inspissated expression (38 %), with 32 % not expressing at all. No MG of <10 % length expressed. MG gland length was correlated with gland expression (r=?0.507, p < 0.001) and MG tortuosity (r=?0.129, p < 0.001), but not MG width (r=?0.090, p = 0.167). Regardless of MG length, warm compress increased the quality of expression (p < 0.002). Debridement further improved expression in partial MGs (p = 0.003), but not forcible expression (p = 0.529).ConclusionsLength is the key functional morphology metric of lower lid MGs. Warm compress and massage increase the quality of expression in all, but the shortest glands and patients with partial length glands also benefit from debridement.     

利用蜂蜡-米糠蜡制备大豆油凝胶油

利用蜂蜡、米糠蜡及其混合物作为凝胶剂,开发大豆油基凝胶油,并将制备的凝胶油与起酥油的物理性质进行比较。通过对2 种添加量下（5%、8%）蜂蜡和米糠蜡（蜂蜡与米糠蜡质量比10∶0、9∶1、8∶2、7∶3、6∶4、5∶5、3∶7、1∶9、0∶10）制备凝胶油的性质测定,结果发现随着米糠蜡比例的增加,凝胶油的硬度（11.9～140.4 g）呈先增加后减小再略有增加的趋势,当蜂蜡与米糠蜡比例为8∶2时,凝胶油的硬度最大,表明蜂蜡和米糠蜡混合后有协同作用;同时析油率采用离心的方法评价,结果发现米糠蜡比例较低（蜂蜡∶米糠蜡＞5∶5）时,凝胶油稳定,析油率为0%,且添加量8%条件下凝胶油的析油率低于普通起酥油。同时固体脂肪曲线、差示扫描量热法结果显示,在10～40 ℃条件下凝胶油的固体脂肪质量分数（8.5%～4%）显著低于起酥油（65%～20%）;融化峰值温度（50.2 ℃）高于起酥油（43.1 ℃）;X射线衍射结果显示8%蜂蜡-米糠蜡（8∶2）凝胶油样品的晶体形态（β’）与起酥油接近,都是细小的结晶。应用发现,蜂蜡与米糠蜡比例为8∶2,添加比例为8%的凝胶油具有较好的烘焙效果,使最终产品的固体脂肪含量大大降低,或许能为消费者拥有更健康的产品提供一条可行途径。     

Chemical interesterification of milkfat and milkfat-corn oil blends

Blending and chemical interesterification of fats have been used to modify physical and chemical properties of natural fats. The objective of this study was to produce binary mixtures of butterfat and corn oil that serve as a base for a tablespread, keeping the desirable organoleptic qualities of butter, yet with higher contents of ω-6 fatty acids. Chemical interesterification was performed to improve butter’s physical properties, such as better spreadability. Liquefied butterfat and corn oil were mixed in different proportions and then chemically interesterified. Butterfat consisted of 66.5% saturated fatty acids, with palmitic acid being predominant. Corn oil had more than 50% of linoleic acid in its composition. Interesterification significantly reduced trisaturated and triunsaturated triacylglycerol contents and increased softening points in all blends. The negative coefficients of the blends from multiple regression of the solid fat content revealed a monotectic interaction between butterfat and corn oil in temperatures ranging from 10 to 35 °C, before and after interesterification.     

Monoglyceride self-assembled structure in O/W emulsion: formation,characterization and its effect on emulsion properties

Monoglycerides (MGs) can form self-assembled structures (liquid crystals) in aqueous or oil systems, which can structure emulsions. In this study, MG was incorporated in Tween 20 or whey protein isolate (WPI) stabilized O/W emulsions, and the crystallizing behavior of MG in the emulsions and its effect on emulsion properties were investigated. Differential scanning calorimetry (DSC) analysis indicated that in TW emulsions MG crystals were mainly in β form when stored at 25 °C, but in α and sub-α forms at 4 °C before finally transferred to β form. In WPI emulsions, only β-form MG crystals were formed regardless of the storage temperature. Synchrotron X-ray diffraction (XRD) study revealed that MG liquid crystals (β form) were stacking in a well ordered lamellar style with a bilayer thickness of 49.5 Å. α and sub-α forms of the crystals were packing in hexagonal and orthorhombic styles, respectively. MG structured WPI emulsions were unstable when subjected to lower pH or NaCl solutions, probably because of WPI replacement by MG, as well as the interaction between MG and WPI.     

利用初榨大豆毛油制备β-谷甾醇油脂凝胶

利用初榨大豆毛油中天然磷脂,通过添加β-谷甾醇,使其与天然磷脂形成复合凝胶剂制备油脂凝胶,研究β-谷甾醇添加量对油脂凝胶硬度、热力学性质、固体脂肪含量（solid fat content,SFC）、凝胶晶型和微观结构的影响。结果表明：在20 ℃条件下,油脂凝胶中β-谷甾醇添加量不小于12%时,即可出现凝胶行为。油脂凝胶的硬度和SFC都随着β-谷甾醇添加量的增加而增加,且在不同贮藏温度下硬度变化显著。β-谷甾醇添加量对热力学特性影响较大,熔化结晶均为单峰。油脂凝胶主要为β型晶体,晶体为长针状并均匀分布,随β-谷甾醇添加量的增多,油脂凝胶晶体密度增大,尺寸变小,形成的三维网状结构更加紧密,截留植物油的能力不断提高,表明β-谷甾醇可以与初榨大豆毛油中的天然磷脂结合形成油脂凝胶,该油脂凝胶中无反式脂肪酸,富含天然营养成分,具有适宜油脂凝胶硬度及良好的结构稳定性等优势。     

天然蜡基油脂凝胶制备、结晶特性及应用研究进展

油脂凝胶化工艺是最具潜力的零反式脂肪酸、低饱和脂肪酸塑性脂肪制备技术之一。油脂凝胶是通过向液态植物油中添加凝胶剂,在加热搅拌或模板脱水等加工条件下获得的具有热可逆、类固态行为的脂质固形物。天然蜡因其价格低廉、容易获得,且能在较低浓度下构建具有较强质构特性的油脂凝胶,被证明是最有效的结晶型凝胶因子。本文系统综述不同组成的天然蜡构建蜡基油脂凝胶的工艺,重点讨论影响蜡基油脂凝胶结晶特性的因素,简要阐述蜡基油脂凝胶的主要优势及其应用情况。在此基础上,对天然蜡基油脂凝胶在食品专用油脂工业化生产中的开发、所遇到的挑战和未来的发展进行讨论。     

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.