Crystal network structure and stability of beeswax-based oleogels with different polyunsaturated fatty acid oils.

The effect of different types of oils including camellia oil (CLO), sunflower oil (SFO), corn oil (CO) and linseed oil (LO) on the formation, crystal network structure and mechanical properties of 4%wt beeswax (BW) in oleogel was investigated. BW oleogels containing oils with higher contents of polyunsaturated fatty acids gelled first (1%wt), especially LO with higher contents of linolenic acid rather than CLO with higher contents of monounsaturated fatty acids. In comparison, oils with higher polyunsaturated fatty acid contents exhibited higher Db with more extensive microstructure at different cooling rates, which was related to shorter nucleation induction time of crystal and higher crystallinity. Stronger van der Waals forces were observed in oleogels with higher polyunsaturated fatty acid contents especially for LO oleogel. Rheology also showed that LO oleogel with higher content of linolenic acid had higher crystallinity and lower crystal melting interfacial tension, resulting in the formation of a more stable network structure.

Gelation behavior and crystal network of natural waxes and corresponding binary blends in high-oleic sunflower oil.

Wax-based oleogels attract considerable attention for their perfect gelation properties, but the waxy mouthfeel severely limits their implementation in food. Herein, we developed a novel strategy via designing the crystal network to produce wax-based oleogels with a suitable mouthfeel. Four natural waxes with different melting points were selected as oleogelators to investigate the gelation behavior. All waxes at 5 wt% concentrations could form stable oleogels with low-frequency dependence. Especially, rice bran wax (RBW) and beeswax (BW) with high oil-binding capacity indicated that the ordered crystal network with fiber or needle-like morphology is more suitable for trapping liquid oil. Interestingly, China lacquer wax (ZLW) presented satisfactory oral melting characteristics according to the melting properties. Subsequently, to enhance the structure of ZLW-oleogel, RBW and BW with desirable crystal networks were added at varying mass ratios (100:0, 75:25, 50:50, 25:75, and 0:100). The binary oleogels exhibited monotectic behavior from thermodynamic phase diagrams. The polarization microscope indicated that similar needle-like crystals in BW/ZLW system enhanced the order of network structure, while long fiber-like crystals by RBW dominated the crystallization of RBW/ZLW binary oleogels. Finally, the BW/ZLW binary oleogels with ratios of 25:75 and 50:50 showed no-waxy mouthfeels in sensory analysis. These findings provide strong theoretical support for the application of wax-based oleogels in plastic fats replacement. PRACTICAL APPLICATION: Natural wax-based oleogel has been widely investigated due to the high oil binding capacity and perfect gelation properties. But its waxy mouthfeel severely limits the application in the food industry. In this study, oleogels with no-waxy an mouthfeel were obtained by designing wax-blend crystalline network. These findings provide strong theoretical support for the application of wax-based oleogels in plastic fats replacement.

Comparation of micro-viscosity of liquid oil in different colloidal fat crystal networks using molecular rotors.

Micro-viscosity is an important parameter to describe the microenvironment of the fat crystal network. In this study, we evaluated the micro-viscosity of the liquid oil confined in mixtures of palm kernel stearin (PKS)/soybean oil (SO) and fully hydrogenated rapeseed oil (FHRSO)/SO using molecular rotors. The micro-viscosity was shown to increase with solid fat content (SFC), as well as with high proportion of triglycerides that crystallized and formed stronger linked networks. In addition, the thickness of nanocrystals decreased with the increase of solid fat and denser fat crystal network appeared with larger box-counting fractal dimension. Mathematic fit analysis further indicated that molecular confinement of the oil was strongly dependent on the microstructure with high-space filling colloidal fat crystal networks. Larger box-counting fractal dimension led to higher micro-viscosity. However, the critical box-counting fractal dimension was found to be 1.86 irrespective of the nature of the network.

Comparative analysis of graded blends of palm kernel oil, palm kernel stearin and palm stearin.

A comprehensive analysis of graded binary and ternary blends of palm kernel oil (PKO), palm kernel stearin (PKS) and palm stearin (POs) was conducted, including solid fat content, iso-solid diagram, thermal properties, polymorphism and microstructure. Both PKO/POs and PKS/POs blends showed eutectic behavior. While PKO/PKS blends displayed good compatibility and only slightly monotectic effect at high temperature (above 30 °C). POs addition elevated binary phase transition temperature and accelerated the ß crystal formation. PKO/POs and PKS/POs binaries showed ß' polymorphism, ß and ß' polymorphism, and ß polymorphism with different POs additions, while all of PKO/PKS blends showed ß' polymorphism. Ternary blends (PKO/PKS/POs) showed eutectic effects, especially at high temperature (25 and 30 °C). POs addition made ternary blends undergo a polymorphism transformation from ß' to ß. Our findings open up the possibility of non-hydrogenated fat products as well as develop specific food formulations.

Structural and mechanical behavior of colloidal fat crystal networks of fully hydrogenated lauric acid-rich fats and rapeseed oils mixtures.

The effects of lipid composition, crystallization temperature, Solid fat content (SFC), microstructure on the rheological properties of blends of fully hydrogenated palm kernel oil (FHPKO) or fully hydrogenated coconut oil (FHCNO) with rapeseed oil (RSO) in the range of 20-100% were investigated using small and large deformation rheology. The variation of chemical composition, crystallization temperature (5-30 °C), SFC of the blends resulted in different rheological properties. Shear modulus was positive correlation with the content of saturated fatty acid of the sample. The storage modulus (G') and yield force increased with the addition of FHPKO or FHCNO and were dramatically influenced by SFC and crystallization temperature. The values of G' in FHPKO/RSO blends were higher than those of corresponding FHCNO/RSO blends. Combined analysis of SFC and microstructure related to rheological behavior revealed that smaller average crystal diameter, higher SFC and higher fractal dimension led to higher storage modulus of fat crystal networks.

Influence of indigenous minor components on fat crystal network of fully hydrogenated palm kernel oil and fully hydrogenated coconut oil.

Purification of triglycerides from fully hydrogenated palm kernel oil (FHPKO) and fully hydrogenated coconut oil (FHCNO) was performed by a chromatographic method. Lipid composition, thermal properties, polymorphism, isothermal crystallization behaviour, nanostructure and microstructure of FHPKO, FHPKO-triacylglycerol (TAG), FHCNO and FHCNO-TAG were evaluated. Removal of minor components had no effect on triglycerides composition. However, the presence of the minor components did increase the slip melting point and promote onset of crystallization. Furthermore, the thickness of the nanoscale crystals increased, and polymorphic transformation from ß' to ß occurred in FHPKO after the removal of minor components, and from α to ß' in FHCNO. Sharp changes in the values of the Avrami constant K and exponent n suggested that the presence of minor components changed the crystal growth mechanism. The PLM results indicated that a coarser crystal structure with lower fractal dimension appeared after the removal of minor components from both FHPKO and FHCNO.

Non-triglyceride components modulate the fat crystal network of palm kernel oil and coconut oil.

PKO and CNO are composed of 97-98% triacylglycerols and 2-3% minor non-triglyceride components (FFA, DAG and MAG). Triglycerides were separated from minor components by chromatographic method. The lipid composition, thermal properties, polymorphism, isothermal crystallization behavior, nanostructure and microstructure of PKO, PKO-TAG, CNO and CNO-TAG were evaluated. Removal of minor components had no effect on lipid composition and equilibrium solid fat contents. However, presence of minor components did increase the slip melting point and promoted the onset of crystallization from DSC crystallization profiles. The thickness of the nanoscale crystals increased with no polymorphic transformation after removing the minor components. Crystallization kinetics revealed that minor components decreased crystal growth rate with higher t1/2. Sharp changes in the values of the Avrami constant k and exponent n were observed for all fats around 10°C. Increases in n around 10°C indicated a change from one-dimensional to multi-dimensional growth. From the results of polarized light micrographs, the transformation from the coarser crystal structure to tiny crystal structure occurred in microstructure networks at the action of minor components.