Characterisation of Fat Crystal Polymorphism in Cocoa Butter by Time-Domain NMR and DSC Deconvolution

Abstract

The polymorphic state of edible fats is an important quality parameter in fat research as well as in industrial applications. Nowadays, X-ray diffraction (XRD) is the most commonly used method to determine the polymorphic state. However, quantification of the different polymorphic forms present in a sample is not straightforward. Differential Scanning Calorimetry (DSC) is another method which provides information about fat crystallization processes: the different peaks in the DSC spectrum can be coupled to the melting/crystallisation of certain polymorphs. During the last decade, nuclear magnetic resonance (NMR) has been proposed as a method to determine, qualitatively and/or quantitatively, the polymorphic forms present in fat samples. In this work, DSC- and NMR-deconvolution methods were evaluated on their ability to determine the polymorphic state of cocoa butter, with XRD as a reference method. Cocoa butter was subjected to two different temperature profiles, which enforced cocoa butter crystallization in different polymorphic forms. It was found that XRD remains the best method to qualitatively determine the polymorphic state of the fat. Whereas the quantitative NMR and DSC deconvolution results were not fully in line with the XRD results in all cases, NMR deconvolution showed great promise both in a qualitative and quantitative way.

Kinetics Crystallization and Polymorphism of Cocoa Butter throughout the Spontaneous Fermentation Process

“…CB is mainly composed of 23.2–29.3% 1,3-di-stearoyl-2-oleoyl-glycerol (SOS), 34.2–38.6% 1-palmitoyl-2-oleoyl-3-stearoyl-glycerol (POS), and 13.5–17.1% 1,3-dipalmitoyl-2-oleoylglycerol (POP) [ 9 , 10 ]. These TAGs allow CB to crystallize in six polyforms, which are γ, α, ′, , , and , and are identified according to their melting temperatures (17.3, 23.3, 25.5, 27.5, 33.8, and 36.3 °C; respectively) [ 9 , 11 , 12 , 13 , 14 ] and stability. Although the contribution of POP is less than those of POS and SOS, its presence may influence the formation of metastable polymorphic forms in CB [ 15 ].…”

“…On the other hand, the analytical technique of X-ray diffraction (XRD) is the most used to study the polymorphism of fat crystals. However, access to XRD equipment is not easy in a research and development unit, so differential scanning calorimetry (DSC) [ 12 ] is an alternative. MacNaughtan et al [ 37 ] demonstrated that the DSC technique could provide reproducible kinetic data on the tristearin-tripalmitin crystallization and polymorphism.…”

Role of Stearic Acid as the Crystal Habit Modifier in Candelilla Wax-Groundnut Oil Oleogels

“…It allows the characterization of atomic and molecular structures of materials by evaluating parameters such as crystallite size and lattice strain. In the food industry, XRD is extensively used to investigate the polymorphism of fats, which refers to the different crystal arrangements of the long hydrocarbon chains in fats [68][69][70]. The three most commonly observed polymorphic structures in fats are α, β , and β, in increasing order of stability [71].…”

Functional and Quality Profile Evaluation of Butters, Spreadable Fats, and Shortenings Available from Czech Market

“…Repeated temperature cycling of butter products from refrigerated to room conditions allows the conversion of a metastable state to a more stable form (β), being adversely affected in the process of spreadability [ 9 ]. For spreadable fats, small β′ crystals are favored since they enable the formation of a good crystal network throughout the continuous lipid phase which is related to desirable sensory and textural properties [ 10 ].…”