The fractal nature of fat crystal networks

Vreeker, R.; Hoekstra, L.L.; Boer, D.C. den; Agterof, W.G.M.

doi:10.1016/0166-6622(92)80273-5

Cited by 116 publications

(81 citation statements)

References 17 publications

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“…They found a decrease in fractal dimension from 2.46 to 2.15, which was in agreement with the drastic decrease in hardness observed by cone penetrometry in the interesterified samples. Vreeker et al (20) determined the value of the fractal dimension of tristearin in olive oil to be about 1.7-1.8. This value increased upon aging of the fat to D = 2 (20).…”

Section: Resultsmentioning

confidence: 99%

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Effect of processing conditions on physical properties of a milk fat model system: Rheology

Herrera

Hartel

2000

J Americ Oil Chem Soc

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The effect of processing conditions on rheological behavior of three blends of 30, 40, and 50% of high-melting fraction [melting point measured as Mettler dropping point (MDP) = 47.5°C] in low-melting fraction (MDP= 16.5°C) of milk fat was studied. The effects of cooling and agitation rates, crystallization temperature, chemical composition of the blends, and time of storage on complex, storage and loss moduli were investigated by dynamic mechanical analysis (DMA). Compression tests were performed on samples using frequency values within the linear viscoelastic range (1 to 10 Hz). Loss modulus was, on average, 10 times lower than elastic modulus and was generally not affected by processing conditions. Samples showed a more solid-like behavior that was better described by storage modulus. Storage modulus varied with all processing conditions used in this study, and even for the same solid fat content, different rheological properties were found. Storage and complex modulus increased with temperature of crystallization (25 to 30°C), even though solid fat contents of samples measured after 24 h at 10°C were the same. Moduli were higher for samples crystallized at slow cooling rate, decreased with agitation rate, and were lower for the 30-70% blend at all processing conditions used. Storage moduli also increased with storage time. Shear storage modulus was calculated from the DMA experimental data, and the results were in agreement with the values reported in literature for butter systems. Fractal dimensions calculated for these systems showed a significant decrease as agitation rate increased in agreement with the softening effect reported for working of butter.In food, an understanding of rheology is critical in optimizing product development efforts, processing methodology, and final product quality (1). The rheological behavior of plastic fats is governed by interactions between fat crystals in an aggregated three-dimensional, solid-liquid matrix (2). The liquid portion of the fat, interspersed throughout the aggregated fat network, serves as a continuous phase and, in conjunction with the solid fraction, is responsible for viscoelastic behavior (3). Of primary importance to the rheological behavior of fat are the amount of crystalline fat and the type of crystals present in the fat crystal network (4,5).Rheological measurements of fats can be performed at low or high deformation. In the latter, the fat crystal network undergoes irreversible deformation, whereas in the former, viscoelasticity is measured below the yield point and any permanent strain remains upon complete release of stress. Materials can be linear elastic, elastoplastic, or nonlinear elastic. Linear elastic materials show a straight line through the origin for stress vs. strain curves. Elastoplastic materials show straight lines until the yield point is reached, and then permanent deformation occurs with higher stress. Nonlinear elastic materials do not show linear behavior in any range of stress. Margarine and butter, at room temperature, may be...

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Section: Resultsmentioning

confidence: 99%

“…Vreeker et al (20) determined the value of the fractal dimension of tristearin in olive oil to be about 1.7-1.8. This value increased upon aging of the fat to D = 2 (20). Low fractal dimensions are indicative of low-density, open structures.…”

Section: Resultsmentioning

confidence: 99%

Effect of processing conditions on physical properties of a milk fat model system: Rheology

Herrera

Hartel

2000

J Americ Oil Chem Soc

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“…This means that randomness in the β crystal distribution may also be significant, probably as it relates to fractal analyses (26)(27)(28) in addition to morphological influence.…”

Section: Discussionmentioning

confidence: 97%

Physical analyses of gel‐like behavior of binary mixtures of high‐ and low‐melting fats

Higaki

Sasakura

Koyano

et al. 2003

J Americ Oil Chem Soc

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Gel-like fat mixtures of high-melting (HM) and low-melting (LM) fats were formed by means of rapid cooling and subsequent heating. No "non-fat" ingredients such as emulsifiers, water, or waxes were added to the mixtures. The gel-like fats having solid fat content (SFC) values below 2.0 wt% formed crystal networks of HM-fats that entrapped the liquid oil fraction of LM-fats. In a search for optimal fat combinations exhibiting gel-like behavior, fully hydrogenated rapeseed oil with a high amount of behenic acid (FHR-B), fully hydrogenated rapeseed oil with a high amount of stearic acid (FHR-S), tristearoylglycerol (SSS), triarachidonoyl-glycerol (AAA), and tribehenoylglycerol (BBB) were examined as the HM-fats. For LM-fats, sal fat olein (SFO), cocoa butter (CB), palm super olein (PSO), and olive oil were examined. The following results were obtained: (i) the gel-like behavior was observed in mixtures of FHR-B/SFO and FHR-B/CB with initial concentrations of FHR-B of 1.5-4.0 wt%. (ii) Rapid cooling to T c (crystallization temperature) from 70°C and subsequent heating to T f (final temperature) were necessary to reveal the gel-like behavior, whereas simple cooling without a cooling/heating procedure did not form the gel-like fat mixture. (iii) Optimal values of T c and T f were related to the m.p. of the LM-fat and HM-fat, respectively. (iv) Temperature variations of SFC as well as X-ray diffraction spectra showed that the melt-mediated transformation from α to β of the HM-fat crystals was a prerequisite to reveal the gel-like behavior. Consequently, the fat mixture revealing the gel-like behavior might be called β-fat gel.Paper no. J10361 in JAOCS 80, 263-270 (March 2003).KEY WORDS: Cocoa butter, fully hydrogenated rapeseed oil, gel-like fat, polymorphism, sal fat olein.Fats and oils are, in general, employed in industrial applications in solid (crystalline), semisolid, emulsion (oil-in-water and water-in-oil), gel, and liquid states. A gel state is defined as a two-phase colloidal system consisting of a solid and a liquid in a more solid form than sol, although there are various definitions representing the complicated nature of gel states (1). Because of their smooth texture, viscoelasticity, appearance, easy handling, and comfortable mouthfeel, gel materials have attracted much attention in food, cosmetic, and pharmaceutical sciences and technology (2-5). Therefore, a wide variety of research into gel phases made of polysaccharides, proteins, and other biopolymer materials has been performed (6,7). In a gel phase made of lipid emulsifiers and water, a lamellar-type lyotropic liquid crystal (LC) phase is formed at elevated temperatures. In the LC phase, a water phase is swelled into a continuous lamellar LC phase. When this LC phase is cooled to undergo the transformation from the LC phase to a crystallization phase, the lamellar structure involving the swollen water phase is maintained, forming a highly viscous phase called an α-gel phase (8-10). Further cooling forms a rheologically hard phase called a coagel. T...

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“…Vreeker et al 4 were the first to realize and propose the fractal nature of fat crystal networks and explained the power-law relationship between the G′ and SFC data for fat samples with low SFC (<10%) by the strong-link regime of Shih et al The fractal dimension of the networks was determined using a light scattering method. Shortly after, Johansson 8 provided strong experimental evidence for the fractal nature of fat crystals in oils.…”

Section: Fractal Modelmentioning

confidence: 99%

“…This structural hierarchy within fat crystal networks has been recognized for a long time by many groups [1][2][3] and further developed during the modeling of the rheological properties of fats. [4][5][6] Figure 1 shows an illustration of the structural hierarchy in fat crystal networks.…”

Section: Introductionmentioning

confidence: 99%

Modeling the Rheological Properties of Fats: A Perspective and Recent Advances

Marangoni

Tang

2007

Food Biophysics

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The elastic modulus of colloidal fat crystal networks scales with the volume fraction of solids in a power-law fashion. To explain and predict how the elastic properties of these networks change with their volume fraction of solids, several physical models have been proposed. In this review, the chronology of the development of structural-mechanical models to explain the elasticity of fats is reviewed, leading to the development of the fractal model. In the fractal model, the fractal-like behavior of fat crystal networks, which can be considered fractal gels of polycrystals in oil, or colloidal crystals, is used to explain the power-law scaling behavior of the shear elastic modulus to the volume fraction of solids. Lately, however, many experimental results and simulation studies suggest that the stress distribution within networks can be dramatically heterogeneous, which means that a small part of the network carries most of the stress. This concept was introduced into a modified fractal model by deriving an expression for the effective volume fraction of stress-carrying solids. The modified fractal model fits the experimental data well and successfully explains the sometimes observed non-linear log-log behavior between the shear elastic modulus and the volume fraction of solids.

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The fractal nature of fat crystal networks

Cited by 116 publications

References 17 publications

Effect of processing conditions on physical properties of a milk fat model system: Rheology

Effect of processing conditions on physical properties of a milk fat model system: Rheology

Physical analyses of gel‐like behavior of binary mixtures of high‐ and low‐melting fats

Modeling the Rheological Properties of Fats: A Perspective and Recent Advances

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