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19 pages, 2617 KiB

Open AccessArticle

Oleogels—Their Applicability and Methods of Characterization

by Eckhard Flöter, Till Wettlaufer, Valentina Conty and Maria Scharfe

Molecules 2021, 26(6), 1673; https://doi.org/10.3390/molecules26061673 - 17 Mar 2021

Cited by 66 | Viewed by 5787

Abstract

Oleogels or, more precisely, non-triglyceride structured lipid phases have been researched excessively in the last decade. Yet, no comprehensive knowledge base has emerged, allowing technology elevation from the laboratory bench into the industrial food application. That is partly due to insufficient characterization of [...] Read more.

Oleogels or, more precisely, non-triglyceride structured lipid phases have been researched excessively in the last decade. Yet, no comprehensive knowledge base has emerged, allowing technology elevation from the laboratory bench into the industrial food application. That is partly due to insufficient characterization of the structuring systems studied. Examining a single composition decided upon by arbitrary methods does not stimulate progress in the research and technology area. A framework that gives much better guidance to product applications can easily be derived. For example, the incremental structure contribution concept is advocated as a parameter to compare the potency of structuring systems. These can straightforwardly be determined by combining solubility data and structural measurements in the recommended manner. The current method to determine the oil-binding capacity suffers from reproducibility and relevance. A newly developed method is suggested to overcome these shortcomings. The recommended new characterization of oleogels should contribute to a more comprehensive knowledge base necessary for product innovations. Full article

(This article belongs to the Special Issue Crystallization of Lipids: From Fundamentals to Applications)

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13 pages, 3326 KiB

Open AccessArticle

Kinetic Study on Alpha-Form Crystallization of Mixed-Acid Triacylglycerols POP, PPO, and Their Mixture

by Ken Taguchi, Akihiko Toda, Hironori Hondoh, Satoru Ueno and Kiyotaka Sato

Molecules 2021, 26(1), 220; https://doi.org/10.3390/molecules26010220 - 4 Jan 2021

Cited by 7 | Viewed by 2973

Abstract

The crystallization behavior of the metastable

α

form of triacylglycerols (TAGs) plays a critical role as a precursor for the crystallization of more stable

β^{'}

and

β

forms for various applications in food and pharmaceutical products. However, precise analysis of the crystallization [...] Read more.

The crystallization behavior of the metastable

α

form of triacylglycerols (TAGs) plays a critical role as a precursor for the crystallization of more stable

β^{'}

and

β

forms for various applications in food and pharmaceutical products. However, precise analysis of the crystallization kinetics of

α

has not been performed, likely due to its rapid and complex behavior. This paper presents the observation results of the initial stages of the isothermal crystallization kinetics of

α

forms of 1,3-dipalmitoyl-2-oleoyl-glycerol (POP), 1,2-dipalmitoyl-3-oleoyl-rac-glycerol (rac-PPO), and molecular compound (MC) crystals of a POP/rac-PPO (1/1) mixture (MC

_{POP / PPO}

) using synchrotron radiation time-resolved X-ray diffraction and polarized optical microscopy. In all the TAGs,

α

crystals with a worm-like morphology started to grow rapidly in the first stage. Then, the

α

crystals slowly transformed into more stable forms in different manners for different TAG samples. In POP, the conversion was simple, as the

α

-2 form transformed into

γ

-3, whereas in rac-PPO, the lamellar distance values of the

α

-2 form continuously decreased with time and changed into the

α

-3 form. In the MC

_{POP / PPO}

crystals, in contrast, separate crystallization of

α

-2 of a rac-PPO fraction initially occurred, followed by the crystallization of

α

-2 of POP, and the two

α

forms merged into

α

-2 of MC

_{POP / PPO}

. This separate crystallization was caused by large differences in the crystallization kinetics of the

α

forms of POP and rac-PPO. Full article

(This article belongs to the Special Issue Crystallization of Lipids: From Fundamentals to Applications)

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22 pages, 6733 KiB

Open AccessArticle

Phase Behavior and Polymorphism of Saturated and Unsaturated Phytosterol Esters

by Eva Daels, Imogen Foubert, Zheng Guo, Wim Thielemans and Bart Goderis

Molecules 2020, 25(23), 5727; https://doi.org/10.3390/molecules25235727 - 4 Dec 2020

Cited by 3 | Viewed by 2626

Abstract

This study investigated how the physicochemical characteristics of phytosterol esters are influenced by the chain length and degree of unsaturation of the fatty acid ester moiety. Saturated and unsaturated phytosterol esters (PEs) were synthesized by the esterification of different types of fatty acids [...] Read more.

This study investigated how the physicochemical characteristics of phytosterol esters are influenced by the chain length and degree of unsaturation of the fatty acid ester moiety. Saturated and unsaturated phytosterol esters (PEs) were synthesized by the esterification of different types of fatty acids (stearic, palmitic, lauric, oleic, and linoleic acid) to β-sitosterol. The non-isothermal crystallization and melting behavior of the pure PEs were analyzed. It was proven by X-ray diffraction that saturated β-sitosteryl esters and β-sitosteryl oleate formed a bilayer crystal structure. The lamellar spacings of the bilayer structure decreased with decreasing fatty acid chain length and with an increasing degree in unsaturation. The degree of unsaturation of the fatty acid chain of the β-sitosteryl esters also influenced the type of subcell packing of the fatty acid moieties in the bilayer structure, whether or not a metastable or stable liquid crystalline phase was formed during cooling. Furthermore, it was found that the melting temperature and enthalpy of the β-sitosteryl esters increased with an increasing fatty acid chain length while they decreased with an increasing degree of unsaturation. The microscopic analyses demonstrated that β-sitosteryl oleate formed much smaller spherulites than their saturated β-sitosteryl analogues. Full article

(This article belongs to the Special Issue Crystallization of Lipids: From Fundamentals to Applications)

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14 pages, 3833 KiB

Open AccessFeature PaperArticle

Crystal Memory near Discontinuous Triacylglycerol Phase Transitions: Models, Metastable Regimes, and Critical Points

by David A. Pink, Marjorie Ladd-Parada, Alejandro G. Marangoni and Gianfranco Mazzanti

Molecules 2020, 25(23), 5631; https://doi.org/10.3390/molecules25235631 - 30 Nov 2020

Cited by 1 | Viewed by 1745

Abstract

It is proposed that “crystal memory”, observed in a discontinuous solid-liquid phase transition of saturated triacylglycerol (TAG) molecules, is due to the coexistence of solid TAG crystalline phases and a liquid TAG phase, in a superheated metastable regime. Such a coexistence has been [...] Read more.

It is proposed that “crystal memory”, observed in a discontinuous solid-liquid phase transition of saturated triacylglycerol (TAG) molecules, is due to the coexistence of solid TAG crystalline phases and a liquid TAG phase, in a superheated metastable regime. Such a coexistence has been detected. Solid crystals can act as heterogeneous nuclei onto which molecules can condense as the temperature is lowered. We outlined a mathematical model, with a single phase transition, that shows how the time-temperature observations can be explained, makes predictions, and relates them to recent experimental data. A modified Vogel-Fulcher-Tammann (VFT) equation is used to predict time-temperature relations for the observation of “crystal memory” and to show boundaries beyond which “crystal memory” is not observed. A plot of the lifetime of a metastable state versus temperature, using the modified VFT equation, agrees with recent time-temperature data. The model can be falsified through its predictions: the model possesses a critical point and we outline a procedure describing how it could be observed by changing the hydrocarbon chain length. We make predictions about how thermodynamic functions will change as the critical point is reached and as the system enters a crossover regime. The model predicts that the phenomenon of “crystal memory” will not be observed unless the system is cooled from a superheated metastable regime associated with a discontinuous phase transition. Full article

(This article belongs to the Special Issue Crystallization of Lipids: From Fundamentals to Applications)

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20 pages, 4208 KiB

Open AccessArticle

Binary Phase Behavior of 1,3-Distearoyl-2-oleoyl-sn-glycerol (SOS) and Trilaurin (LLL)

by Shinichi Yoshikawa, Shimpei Watanabe, Yoshinori Yamamoto and Fumitoshi Kaneko

Molecules 2020, 25(22), 5313; https://doi.org/10.3390/molecules25225313 - 14 Nov 2020

Cited by 9 | Viewed by 2547

Abstract

This paper reports the precise analysis of the eutectic mixing behavior of 1,3-distearoyl-2-oleoyl-sn-glycerol (SOS) and trilaurin (LLL), as a typical model case of the mixture of cocoa butter (CB) and cocoa butter substitute (CBS). SOS was mixed with LLL at several [...] Read more.

This paper reports the precise analysis of the eutectic mixing behavior of 1,3-distearoyl-2-oleoyl-sn-glycerol (SOS) and trilaurin (LLL), as a typical model case of the mixture of cocoa butter (CB) and cocoa butter substitute (CBS). SOS was mixed with LLL at several mass fractions of LLL (w_LLL); the mixtures obtained were analyzed for polymorphic phase behavior using differential scanning calorimetry (DSC) and synchrotron radiation X-ray diffractometry (SR-XRD). In melt crystallization with constant-rate cooling, SOS and LLL formed eutectics in their metastable polymorphs, allowing the occurrence of a compatible solid solution at w_LLL ≥ 0.925. With subsequent heating, the resultant crystals transformed toward more stable polymorphs, then melted in a eutectic manner. For mixtures aged at 25 °C after melt crystallization, eutectics were found in the extended w_LLL region, even at w_LLL = 0.975. These results indicate that phase separation between SOS and LLL progressed in their solid solution under stabilization. The crystal growth of the separated SOS fraction may cause fat-bloom formation in compound chocolate containing CB and CBS. To solve this problem, the development of retardation techniques against phase separation is expected. Full article

(This article belongs to the Special Issue Crystallization of Lipids: From Fundamentals to Applications)

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13 pages, 4138 KiB

Open AccessArticle

Mixing Ratio and Cooling Rate Dependence of Molecular Compound Formation in OPO/POP Binary Mixture

by Kengoh Nakanishi and Satoru Ueno

Molecules 2020, 25(22), 5253; https://doi.org/10.3390/molecules25225253 - 11 Nov 2020

Cited by 12 | Viewed by 1921

Abstract

Owing to the increasing reports of the harmful effects of trans and saturated fatty acids, the demand for trans- and saturated-fatty-acid-free oil and fat products is increasing among consumers. However, it is difficult to maintain the product stability and shape retention of such [...] Read more.

Owing to the increasing reports of the harmful effects of trans and saturated fatty acids, the demand for trans- and saturated-fatty-acid-free oil and fat products is increasing among consumers. However, it is difficult to maintain the product stability and shape retention of such oil and fat products. As a result, there is a high demand in the processed oil and fat industry to develop solutions to such problems. Herein, we used molecular compound (MC) crystals in an attempt to find alternatives to trans and saturated fatty acids. The MCs used were 1,3-dioleoyl-2-palmitoyl-sn-glycerol (OPO) and 1,3-dipalmitoyl-2-oleoyl-sn-glycerol (POP)—the main components of lard and palm oil, respectively. We believe that OPO and POP can be used to obtain no-trans, low-saturation, and high-oleic-acid oil and fat products. Optimal conditions for efficient MC crystallization were examined by changing the oil and fat composition under rapid cooling conditions assuming industrial cooling process by using differential scanning calorimetry and synchrotron radiation time-resolved X-ray diffraction methods. It was concluded that the increase in OPO concentration destabilized MC formation, while the increase in POP concentration stabilized it under rapid cooling conditions. As a result, it was shown that MC crystals can be efficiently obtained by reducing the degree of POP supercooling. Full article

(This article belongs to the Special Issue Crystallization of Lipids: From Fundamentals to Applications)

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14 pages, 4062 KiB

Open AccessArticle

Multiple β Forms of Saturated Monoacid Triacylglycerol Crystals

by Seiya Takeguchi, Arisa Sato, Hironori Hondoh, Mio Aoki, Hidetaka Uehara and Satoru Ueno

Molecules 2020, 25(21), 5086; https://doi.org/10.3390/molecules25215086 - 2 Nov 2020

Cited by 13 | Viewed by 2692

Abstract

We have investigated the polymorphism of triacylglycerol (TAG) crystals as they affect the qualities such as shelf life, mouth feel, and texture of chocolate and other products. Saturated monoacid TAGs, like trilaurin, are considered as models for TAG crystallization; however, there is still [...] Read more.

We have investigated the polymorphism of triacylglycerol (TAG) crystals as they affect the qualities such as shelf life, mouth feel, and texture of chocolate and other products. Saturated monoacid TAGs, like trilaurin, are considered as models for TAG crystallization; however, there is still debate about the number of their polymorphs that exist. In this study, we characterized a set of novel polymorphs, β forms of saturated monoacid TAGs, which were obtained via different pathways depending on the crystallization history, by polarized light microscopy, X-ray diffraction, and differential scanning calorimetry. Saturated monoacid TAGs were crystallized as the unstable polymorphs, the α or β’ forms first, and then they were transformed into β forms by solid–solid transformations. The β form that had transformed from β’ changed its morphology by a polymorphic transformation, while the β form made from the α form kept its spherulite morphology. The β forms obtained showed different melting points. Additional heat treatment promoted further polymorphic transformation. Four novel β forms were found for each of the saturated monoacid TAGs, trilaurin, trimyristin, tripalmitin, and tristearin. They showed similar polymorphism with the same subcell packing. Full article

(This article belongs to the Special Issue Crystallization of Lipids: From Fundamentals to Applications)

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14 pages, 2933 KiB

Open AccessArticle

Structural Study on Fat Crystallization Process Heterogeneously Induced by Graphite Surfaces

by Fumitoshi Kaneko, Yoshinori Yamamoto and Shinichi Yoshikawa

Molecules 2020, 25(20), 4786; https://doi.org/10.3390/molecules25204786 - 19 Oct 2020

Cited by 7 | Viewed by 2619

Abstract

Some inorganic and organic crystals have been recently found to promote fat crystallization in thermodynamically stable polymorphs, though they lack long hydrocarbon chains. The novel promoters are talc, carbon nanotube, graphite, theobromine, ellagic acid dihydrate, and terephthalic acid, among which graphite surpasses the [...] Read more.

Some inorganic and organic crystals have been recently found to promote fat crystallization in thermodynamically stable polymorphs, though they lack long hydrocarbon chains. The novel promoters are talc, carbon nanotube, graphite, theobromine, ellagic acid dihydrate, and terephthalic acid, among which graphite surpasses the others in the promotion effect. To elucidate the mechanism, we investigated the influence of graphite surfaces on the crystallization manner of trilaurin in terms of crystal morphology, molecular orientation, and crystallographic features. Polarized optical microscopy, cryo-scanning electron microscopy, synchrotron X-ray diffractometry, and polarized Fourier-transform infrared spectroscopy combined with the attenuated total reflection sampling method were employed for the analyses. All the results suggested that the carbon hexagonal network plane of graphite surfaces have a high potential to facilitate the clustering of fat molecules against high thermal fluctuations in fat melt, the fat molecules form a layer structure parallel to the graphite surface, and the clusters tend to grow into thin plate crystals of the β phase at the temperatures corresponding to low supercooling. The β′ phase also has a larger chance to grow on the graphite surface as supercooling increases. Full article

(This article belongs to the Special Issue Crystallization of Lipids: From Fundamentals to Applications)

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Review

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27 pages, 4337 KiB

Open AccessReview

An Insight into the Solid-State Miscibility of Triacylglycerol Crystals

by Jorge Macridachis-González, Laura Bayés-García and Teresa Calvet

Molecules 2020, 25(19), 4562; https://doi.org/10.3390/molecules25194562 - 6 Oct 2020

Cited by 22 | Viewed by 4500

Abstract

The crystallization properties of triacylglycerols (TAGs) strongly determine the functional properties of natural lipids. The polymorphic and mixing phase behavior of TAG molecules have long been, and still are, a hot topic of research with special relevance for the cosmetic, pharmaceutical, and food [...] Read more.

The crystallization properties of triacylglycerols (TAGs) strongly determine the functional properties of natural lipids. The polymorphic and mixing phase behavior of TAG molecules have long been, and still are, a hot topic of research with special relevance for the cosmetic, pharmaceutical, and food industry. To avoid the difficulties arising from the study of whole real fats, studies at the molecular level on mixtures of a limited number of TAGs has become an indispensable tool to identify the underlying causes of the physical properties in lipid systems. In particular, phase diagrams of binary mixtures of TAGs exhibiting a different degree of heterogeneity (monoacid or mixed fatty acids; molecular symmetry; the presence of cis or trans double bonds) have resulted in a significant breakthrough in our knowledge about structure–interaction–function relationships. The present work aims to provide an overview of the main reports regarding binary and ternary TAG systems, from the early studies to the most recent developments. Full article

(This article belongs to the Special Issue Crystallization of Lipids: From Fundamentals to Applications)

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