Binary Mixtures of Tripalmitoylglycerol (PPP) and 1,3‐Dipalmitoyl‐2‐stearoyl‐sn‐glycerol (PSP): Polymorphism and Kinetic Phase Behavior

Abstract

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.

Polymorphism and Kinetic Behavior of Binary Mixtures of Trisaturated Triacylglycerols Containing Palmitic and Stearic Acid Under Non‐Isothermal Conditions

“…At the higher cooling rate, it was already concluded that PSP drives the overall crystallization process. In our previous study, [14] mixtures of PPP-PSP, when cooled at 1.0 C min À1 , crystallized in the β 0 -form when X PSP ! 0.2.…”

“…0.5, which could be associated with the presence of the more stable β 0 1 -form. [14] In the PSS-PSP mixtures, however, the peak temperatures slightly decreased when PSP concentration was increased (X PSP 0.5, dotted line in Figure 2b), followed by a linear increase in the peak temperature at higher PSP concentrations (X PSP ! 0.6).…”

“…For preparation of PPP and PSP, the method as described by Bhaggan et al was used. [14] Pure PSS was prepared via hydrogenation of pure POO that was produced via a similar procedure. Oleic acid (700 g) was reacted with glycerol (70 g) in the presence of enzyme (21 g) (Lipozyme RM IM, Novozymes Denmark) and the purified OOO (500 g) was reacted with palmitic acid (250 g) using a 1,3-specific lipase (Biocatalyst L, Bunge Loders Croklaan, the Netherlands) to produce POO, which was purified by silica treatment.…”

“…Oleic acid (700 g) was reacted with glycerol (70 g) in the presence of enzyme (21 g) (Lipozyme RM IM, Novozymes Denmark) and the purified OOO (500 g) was reacted with palmitic acid (250 g) using a 1,3-specific lipase (Biocatalyst L, Bunge Loders Croklaan, the Netherlands) to produce POO, which was purified by silica treatment. [14] The latter acidolysis process was conducted in a packed bed reactor process in which the residence time in the column was controlled to minimize the formation of POP. The obtained product, which contained about 96% POO was further fully hydrogenated to obtain PSS in which process the traces of POP were converted to PSP.…”

“…In a previous study we studied the polymorphism and kinetic phase behavior of binary mixtures of PPP and PSP. [14] The present paper presents a study of the polymorphism and the kinetic phase behavior of binary mixtures of PPP-PSS and PSS-PSP. A good understanding of the transformation behavior of these TAGs can help in the control of the crystallization, phase development, and stabilization of many important food products.…”