Quantitative Phase Analysis of Complex Fats during Crystallization

Abstract

The quantitative study of polymorphism in fats is complicated due to their complex composition and consequent intricate crystallization behavior. We aimed to illustrate how quantitative phase analysis can be performed in crystallizing complex fats. The advantages of our proposed method are that detailed structural information or internal standards are not needed and that it can be applied even to wide-angle X-ray diffraction patterns with a high noncrystalline (liquid fat) contribution and overlapping peaks. Diffraction patterns of palm oil and anhydrous milk fat during crystallization were decomposed by fitting a model based on Pearson type VII functions. From the decomposed patterns, the contribution of each phase was quantified as a function of time. Each contribution to the pattern was then converted to its mass fraction using response factors derived from the corresponding solid fat content, which was measured using low-resolution nuclear magnetic resonance (NMR). This approach allowed us to quantify the evolution of liquid and polymorphic phases during the early crystallization of complex fats and, for the first time, to quantify coexisting α, β′, and β phases. This method is flexible enough for fats with diverse triacylglycerol profiles yet detailed enough to quantify phase transitions in a system as complex as milk fat.

Polymorphism of a Highly Asymmetrical Triacylglycerol in Milk Fat: 1-Butyryl 2-Stearoyl 3-Palmitoyl-glycerol

“…Indeed, the αto β′polymorphic conversion is accompanied by a continuous increase in the solid fat content (SFC). Estimations from the wide-angle X-ray patterns 39 show that the SFC increases from 47 to 76% from t = 1 to t = 18 h of isothermal hold. Details on SFC estimations are presented in the Supporting Information Figure S1.…”

Solid-liquid phase transitions in Griebenschmalz, smalec, and fedt studied using 13C solid-state NMR with dynamics-based spectral filtering

“…While the ~1 ppm higher shift of the all-trans methylene for the high-melting form is consistent with literature data for the a/b¢-and b-forms of tripalmitin [13], and corresponds to the differences observed for the interior methylene carbons in triclinic and other crystal forms of all-trans alkanes [39], the carbonyl shifts agree with none of the conventional a-, b¢-, or b-forms [13,40], indicating that the molecular conformations and crystal structures in the present fat blends differ from the ones found in pure triglycerides. Although X-ray diffraction of complex fat blends are often interpreted using crystal form terminology developed for simpler triglyceride systems [41,42], the data in Fig. 4 suggests that further solid-state NMR studies may be useful to elucidate the details of the structures and possibly identify sub-groups of crystal forms.…”

Polymorphic Phase Transitions in Bulk Triglyceride Mixtures

“…The fractions of these two phases are approximately equal, as their peak areas are similar. To make the latter conclusion we assume that the specific response factors [13] for the signal obtained from the different domains are similar, because the LLL and MMM molecules belong to the same homologous series.…”

“…8,10,11 The phase behavior of natural oils and fats plays a crucial role in the texture, solubility, plasticity, glossiness, firmness, and many other properties of various consumer products, including ice cream, chocolate, margarine, butter, whipped cream, and others in the food industry and lip balms, creams, and lotions in cosmetics. 10,12,13 Therefore, a deep understanding of the phase behavior of these systems is of fundamental importance for controlling and predicting these properties and for optimization of fat-based formulations when using healthier and/or more sustainable raw materials.…”