Effects of wax concentration and carbon chain length on the structural modification of fat crystals

Abstract

Natural waxes are cost-effective and potential fat crystallization modifiers; however, there is limited information about their implementation in solid triacylglycerol (TAG) oil. Herein, we investigated the effects of two natural waxes, namely, candelilla wax (CLW) and rice bran wax (RW), with different concentrations (2, 4, 6, and 8 wt%) and carbon chains on the crystal growth and structure of palm kernel stearin (PKS85). CLW significantly accelerated the PKS85 crystallization process. Both waxes could induce a new hydrocarbon chain with the lengths of 3.70 and 4.15 Å during the TAG crystallization, respectively. Particularly, X-ray diffraction (XRD) indicated that PKS85 combined with CLW showed a similar lamellar thickness (d₀₀₁) and crystal domain size (ξ) with pure PKS85, whereas that of PKS85 containing RW was 1.7–1.8 and 1.5–1.8 fold higher, respectively. This result corresponded to the carbon chain length of CLW and RW, which was double and quadruple that of PKS85, respectively. Further, these variations were reflected in the crystal microstructures of PKS85 with CLW and RW, where the former showed small homogeneous crystals, while the latter displayed large rod-like layered crystals. In addition, the firmness significantly increased when CLW and RW were added, which is possibly attributed to the fact that the waxes became the backbone of the crystal “fence”. Our findings give clear insight into the interaction between TAGs and wax molecules in the crystallization process, which can help guide the utilization of natural waxes in the modification of fats.