Matching the Functionality of Single-Cell Algal Oils with Different Molecular Compositions

The fatty acid composition, triglyceride composition, melting/crystallization profiles, crystallization kinetics, X-ray diffraction patterns, microstructure and mechanical properties of a pair of algal oils were studied to elucidate structural reasons for the similarity in melting and mechanical properties. Oil A is a predominantly saturated fat, rich in capric, myristic and palmitic acids, composed mostly of trisaturated triglycerides while Oil B contains predominantly palmitic and oleic acids in triglycerides such as POP/OPP and OOP/OPO. The DSC thermogram of Oil A shows similar peak melting temperatures to that of Oil B with Oil B exhibiting a few additional peaks. Both oils exhibit identical SFC-temperature profiles. Polarized light microscopy revealed a needle-like morphology for both Oil A and Oil B, with an average length of approximately 3.5–4.0 μm. The similar morphology of the crystals was attributed to a similar polymorphic form (β’) present in both. The fractal dimensions for the distribution of crystalline material within the fat crystal networks of both oils were also similar. The identical melting and mechanical properties of Oil A and Oil B were thus be attributed, respectively, to the presence of different triglycerides (in approximately equal proportions) with similar melting points and the assembly of these triglycerides into crystals of identical shape and size, which are in turn assembled into a network with identical crystal mass distributions. This work suggests that the mechanical and thermal properties of oils with vastly different molecular compositions can be matched by targetting specific TAG combinations which yield similar melting behavior, microstructure and mechanical response.