On the quantitative phase analysis and amorphous content of triacylglycerols materials by X-ray Rietveld method

• Published in: Chemistry and physics of lipids 2018-05, Vol.212, p.51-60
• Main Authors: Calligaris, Guilherme A., da Silva, Thais L.T., Ribeiro, Ana Paula B., dos Santos, Adenilson O., Cardoso, Lisandro P.
• Format: Article
• Language: English
• Subjects: Crystallinity; Polymorphism; Quantitative analysis; Rietveld method; Triacylglycerol; X-ray diffraction
• ISSN: 0009-3084; 1873-2941
• DOI: 10.1016/j.chemphyslip.2018.01.003

Mixtures (M) and blended (B) hardfats samples involving fully hydrogenated of soybean (FHSO) and palm (FHPO) oils were characterized by XRD associated with the Rietveld structure refinement method, aiming a quantitative analysis of TAG polymorphs. The M50:50 sample was prepared to 50% of FHSO (β-form) and 50% of FHPO (β’-form). Quantitative Phase Analysis (QPA) based on Rietveld Method applied to this sample provided the expected value for them, validating the applicability of this approach in this kind of materials. After thermal treatment and melting, the QPA of the blended B50:50 sample has shown a distinct concentration of the β and β’ polymorphic forms, with the predominance of the β’-form due to the seeding process. [Display omitted] •Rietveld Method supports XRD quantitative phase analysis of polymorphism on industrial and academic appealing samples.•Rietveld analysis of modified β-SSS and β’-PPS structures to allow β and β’ polymorphs content from TAG materials.•Assessment of amorphous/crystalline cocoa butter content based on XRD pattern by Rietveld Method.•This approach allows for improvement on the TAG polymorphic characterization compared to labeling peak intensities. The characterization of fat components becomes very useful for formulation of shortening, margarines and fat products due to their unique properties of plasticity, texture, solubility, and aeration. However, X-ray diffraction experiments on such materials are usually limited to a qualitative evaluation of the polymorphic properties based only on the characteristic d-spacing peak intensities. In this work, interesting results based on the Rietveld Method have supported both a Quantitative Phase Analysis and Degree of Crystallinity study on industrial and academic appealing samples, such as triacylglycerol standards, fully hydrogenated vegetable oils (hardfats) and cocoa butter. This useful approach to the area of oils and fats can provide valuable information about the polymorphism and its relationship to the application of lipid materials in food science and technology. Here, the discrimination between β and β’ polymorphs on samples made of mixtures or blended hardfats was attained, and the results have shown a relevant contrast in comparison to a purely qualitative approach. Assessment of amorphous content on cocoa butter samples was achieved by isolating its contribution from the total X-ray diffraction background via mathematical tools during the whole pattern fitting.