The crystallization of shea stearin was investigated both before and after pre‐treatment with silica to remove a small amount (0.7 wt%) of diacylglycerols (DAGs) and oxidized material. NMR (for solid fat content), X‐ray diffraction (XRD), polarized light microscopy, confocal Raman microscopy, and non‐isothermal, isothermal and “stop‐and‐return” differential scanning calorimetry (DSC) techniques were used. Four major polymorphs previously found with 1,3‐distearoyl‐2‐oleoyl‐sn‐glycerol (StOSt) were detected: α, γ, β′, and β; whilst evidence for a further (δ) polymorph was found by DSC and possibly XRD but not Raman spectroscopy. Isothermal crystallization of shea stearins by DSC at 20°C produced α and δ forms within 5 min which then transformed to γ. Microscope images showed that after 1 day these had transformed into β′ with a few crystals of β, with further conversion to β after one week. Silica treated samples showed a faster initial crystallization, with faster transformation or direct crystallization into δ and then γ and β′ forms. Non‐isothermal DSC also showed a faster transformation into γ from α on the subsequent remelt. However, further transformation into β appeared to occur at reasonably similar rates for both types, suggesting that DAGs have less influence on this transformation and may be excluded from higher forms. Practical applications: This paper has two main practical applications: (i) Provides knowledge and understanding of the crystallization and polymorphic behavior of commercial shea stearin, which is a widely used fat in the confectionery, cosmetic, and pharmaceutical industries. (ii) The presence of small amounts of DAGs significantly delays the crystallization process of shea stearin, particularly of the lower polymorphs.

The kinetic phase behavior and phase transformation paths of tripalmitoylglycerol (PPP) and 1,3‐dipalmitoyl‐2‐stearoyl‐sn‐glycerol (PSP) mixtures are investigated at 10.0 °C min−1 (fast cooling) and 1.0 °C min−1 (slow cooling) cooling rates, and re‐heating at 5.0 and 1.0 °C min−1. Mixtures with 0.1 XPSP increments are studied in terms of polymorphism, crystallization, and melting. At the higher cooling rate, all samples crystallized in the α polymorph, while at the lower cooling rate, samples containing XPSP ≤ 0.3 crystallized in the α polymorph and samples containing XPSP > 0.3 crystallized in the β′ polymorph. During heating, all samples transformed to a more stable β′ form and melted finally in the β form (XPSP ≤ 0.3) or in the β′ form (XPSP > 0.3). Kinetic phase diagrams are determined from the DSC heating thermograms and XRD patterns obtained during cooling and heating and displayed an eutectic behavior with an eutectic point at XPSP = 0.3 irrespective of the rate at which the samples are cooled and re‐heated. The eutectic temperature is independent of the cooling and heating rates used. This study shows that PSP has a strong effect on the physical properties of PPP–PSP mixtures and dominates a large part of the phase behavior of the PPP–PSP binary system. At lower PSP concentration, the mixtures transform to the most stable β form, but at increasing PSP concentration the mixtures stabilize in the β′‐phase which is preferred in many food application because this results in a smooth texture. Practical Application: The results of this study are useful for the food industry as they can help in understanding the functionality of hard fat‐based structuring agents in end applications and in developing new triacylglycerol‐based crystallization and structuring agent for specific food applications PPP–PSP mixtures, either cooled or heated at lower or higher rate, all samples display different type of phase behavior: α‐ to β′‐phase development via recrystallization from the melt for mixtures having low PSP concentration, an α‐ to β′‐phase development via solid–solid transformation, a β′2‐ to β′1‐phase development via solid–solid transformation, and a β′‐ to β‐phase development via solid–solid transformation with an apparently typical eutectic behavior, with an eutectic concentration (XE) of about XPSP = 0.3. The eutectic temperature is not affected by the processing conditions applied. In the XPSP ≤ XE side of the phase diagram, the transition is different, being more β stable and is strongly affected by increasing PSP content (XPSP > XE side), which are more β′ stable.

The kinetic phase behavior and phase transformation paths of pure tripalmitoylglycerol (PPP), 1‐palmitoyl‐2,3‐distearoyl‐sn‐glycerol (PSS), and 1,3‐dipalmitoyl‐2‐stearoyl‐sn‐glycerol (PSP) and binary mixtures thereof, are investigated at 10.0 °C min−1 (fast cooling) and 1.0 °C min−1 (slow cooling) cooling rates, and further re‐heating at 5.0 and 1.0 °C min−1. Mixtures are studied in terms of polymorphism, crystallization, and melting behavior. Kinetic phase diagrams are determined from DSC heating thermograms and XRD data. Independent of the cooling rate, most samples crystallized in the α‐polymorph and transformed into the more stable β′‐form via melt‐mediated crystallization or direct recrystallization from the α‐phase. Samples containing a high amount of PSP crystallized in the β′‐form at slow cooling rate and samples containing high PPP concentration ultimately transform to the most stable β‐form. The kinetic phase diagram of PPP‐PSS mixtures present an apparently typical eutectic behavior with a eutectic point at XPSS = 0.3, when the samples are melted at the higher heating rate, which shifts to higher concentration, XPSS = 0.5, when the lower heating rate is applied. The eutectic temperature (58.4 ± 0.3 °C) is independent of the cooling and heating rates used. The kinetic phase diagram of PSS‐PSP mixtures display two types of behaviors, a probable monotectic behavior in the most stable phase and a eutectic behavior in the meta‐stable phase when the samples are melted at higher heating rate. This study shows that PSS has a strong effect on the physical properties of PPP‐PSS blends and affects a large part of the phase behavior of this binary system. At lower PSS concentrations, the mixtures transform to the most stable β form, but at increasing PSS concentration, the samples stabilize in the β′‐phase. In the PSS‐PSP binary systems, all the mixtures stabilize in the β′‐phase, which is preferred in many food applications since it is associated with a smooth texture. Practical Applications: This research extends a previous study on the phase behavior of the most common trisaturated triacylglycerols and the results are useful for the food industry as they can help in understanding the functionality of hard fat based structuring agents in end applications, and in developing new triacylglycerol based crystallization and structuring agent for specific food applications. The kinetic phase behavior of trisaturated triacylglycerol containing stearic and palmitic acid were studied under three sets of conditions. The binary systems showed different behaviors at the conditions studied. An apparent eutectic phase behavior was obtained for mixtures containing mono‐acid and symmetric triacylglycerols. However, the samples containing asymmetric triacylglycerols showed a probable monotectic phase behavior in the most stable β′1‐phase.

Nine different stearin fractions with 1,3‐distearoyl‐2‐oleoyl‐sn‐glycerol (StOSt) contents ranging from 69–84% were obtained via fractionation from fats produced by acidolysis of high oleic sunflower oil (HOSO) with various mixtures of stearic (either 95 or 98% pure) and palmitic acids (98% pure). Samples were further treated with silica to reduce the oxidised glyceride and DAG content. Isothermal crystallisation at 20°C showed a single main peak, but evidence of crystallisation during the initial DSC transient was also apparent for high StOSt content samples. This was confirmed as the α form by stop‐and‐return DSC and XRD. The main crystallisation event was generally faster (including a shorter induction time) for samples with higher StOSt levels (lower POSt levels). Silica treatment generally accelerated transformations to higher polymorphs (γ, β′ and β). Raman microscopy experiments showed that crystallisation of the β‐form was achieved after 7 days storage at 20°C but only in the silica treated stearin samples. This is consistent with higher solid fat content (SFC) values that were obtained with silica treated samples, which also increased with higher levels of StOSt. The results suggest that such stearins could potentially replace shea stearin in cocoa butter equivalents (CBE) formulations. Practical applications: This paper has two main practical applications: (i) Provides knowledge and understanding of the crystallisation and polymorphic behaviour of isolated hard stearins, obtained from enzymatic acidolysis of high oleic sunflower oil, which can be further used in CBE formulations. (ii) The presence of minor components significantly delays the crystallisation of the stearins, confirming the desirability of higher quality (less oxidised/hydrolysed) fat ingredients.

Filling fats are used in bakery and confectionery applications. These fats are made up of complex mixtures of triacylglycerols (TAG). The crystallization, melting behaviour and polymorphic stability of fat blends are determined by the behaviour of the TAGs that they contain. Filling functionalities are influenced by their fat composition but also by the processing conditions used for crystallization. In this study, the crystallization behaviour of fat blends, all based on shea stearin as hard fat (which is high in 1,3-distearoyl-2-oleoyl glycerol (SOS)) combined with either sunflower oil, shea olein or rapeseed oil, were investigated by means of pulsed nuclear magnetic resonance (pNMR), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Blends containing either 30 or 40% shea stearin combined with one of the soft fats were selected as they met the criteria required for filling fats. Under static isothermal conditions (at 10°C, 15°C or 20°C), a two-step crystallization was observed for those blends, which can be explained by polymorphic transitions from a-form into more stable forms. All the selected blends exhibited different crystallization mechanisms according to the TAG composition of the liquid phase and their complementarity with TAG from the solid phase.Practical applications: Results of this research are useful for the fat industry as they could help to develop new filling fats, based on shea stearin, with a reduced content of saturated fats, while maintaining the desired physical properties of such specific products.