The crystallizing behavior of a model water/oil (W/O) emulsion with different fat formulas was investigated. The model W/O emulsion was stored in a programmable oven under a temperature fluctuation cycle of 5 7C for 12 h and 20 7C for another 12 h. Crystal growth was observed using a polarization microscope, until the crystals were over 100 mm in diameter, which causes texture degradation. We examined whether the texture degradation is related to the fatty acid formula and the triglyceride formula by carbon number. We also examined the effect of the triglyceride species concentration estimated from the fatty acid formula on the texture degradation. The palmitic acid content was related with texture degradation at high concentration among the fatty acid species. The triglyceride content was not related with texture degradation. Triacylglycerol species with palmitic acid such as tripalmitate (PPP) and 1,3-dipalmitoyl-2-oleoyl-glycerol (POP) were related with texture degradation. The summed up concentration of three triglycerides [PPP, POP and 1,2-dipalmitoyl-3-oleoyl-glycerol (PPO)] was related with texture degradation. Lipid Sci. Technol. 2010, 112, 304-309 Practical applicationsWe examined the effects of fatty acid and TAG species on the crystallizing behavior in the complex composition of fat. Our results would be useful to formulate the fat composition of W/ O emulsions and to control the growth of granular crystals.

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The effect of shearing on the polymorphic behavior of palm oil-based fat blends with low (LT-Fat) and high (HT-Fat) trans-fatty acid contents during storage was investigated. A shear stress was applied to fat blends at 5℃ or 10℃ by the flat-crush method or after rapid or slow cooling by the syringe-extrusion method. The fat networks were evaluated by cryo-scanning electron microscopy (SEM), polarized light microscopy, and solid fat content measurement, and the polymorphic transition from the β′-form to the β-form under thermal thawing between 5℃ and 20℃ was investigated by X-ray diffraction. Transition to the β-form of LT-Fat with shearing was retarded compared with that without shear. SEM revealed that with shearing, LT-Fat built complex networks involving both fine reticulation and a tight structure, whereas without shearing, the structure was nearly uniform. These results suggest that the non-uniformly network achieved by shearing could suppress the localization of specific triacylglycerides, preventing transformation into the β-form.

Fatty acid was covalently attached to lipase (EC 3.1.1.3.) fromPhycomyces nites, yielding a modified lipase of higher specific activity in hydrolytic and synthetic reactions in organic solvents. Attached long‐chain fatty acids solubilized the lipase in organic solvent and, therefore, promotion of dispersibility in organic solvent resulted in much higher reactivity. The initial rate of transesterification by modified lipase was almost 40 times that of native lipase in organic solvent. The specificities and selectivity of the modified lipase depended on the kind of attached fatty acid.

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