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

Abstract

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...

In situ optical observation of microstructure of β-fat gel made of binary mixtures of high-melting and low-melting fats

“…1, gel-like behavior was observed as reported previously (Higaki et al, 2003). In this case, small FHR-B crystals with dimensions of 10 lm were formed in the FHR-B/SFO liquid mixture at T c ¼ 20°C (Fig.…”

“…Our previous XRD study showed that the b 0 and b forms developed in the FHR-B/SFO liquid mixture at T c ¼ 20°C. In addition, the b 0 form transformed to the b form by solid-state transformation after subsequent heating from 20 to 38°C not by melt-mediation when V c was 1.5°C/min (Higaki et al, 2003). The crystals shown in Fig.…”

“…The TAG and fatty acid compositions of these fat materials have been reported elsewhere (Higaki et al, 2003). The melting points of the HM and LM fats are shown in Table 1.…”

“…Recently, we found that gel-like behavior occurs only in fat mixtures consisting of two kinds of fats, highmelting (HM) fat (concentrations below 4.0 wt%) and low-melting (LM) fat when special thermal treatments were applied to the mixture systems without any other ingredients (Higaki, Sasakura, Koyano, Hachiya, & Sato, 2003). We assumed that the crystal network of the HM fat fractions of b polymorph was formed during proper thermal treatment to reveal gel-like fat.…”

Basic Evaluation of Gelatinous Fat to Improve Properties of Nursing Care Food

“…Gel with water as the liquid component in the continuous phase is called hydrogel, while gel with liquid oil in the continuous phase is called organogel. Although hydrogels have been mainly used for nursing care food, organogels have better properties than hydrogels, such as weak polarity, resilience, and viscoelasticity 22,23 . Therefore, we considered that an organogel could be used as an aggregating ingredient of minced food, and developed an adjusted gelatinous fat in order to promote bolus formation.…”