Crystallization Behavior of Molecular Compound in Binary Mixture System of 1,3‐Dioleoyl‐2‐Palmitoyl‐sn‐Glycerol and 1,3‐Dipalmitoyl‐2‐Oleoyl‐sn‐Glycerol

Abstract

Previous studies showed that the stable β‐form of molecular compound (MC) crystals having a double‐chain‐length structure is formed in a binary mixture system of 1,3‐dioleoyl‐2‐palmitoyl‐sn‐glycerol (OPO) and 1,3‐dipalmitoyl‐2‐oleoyl‐sn‐glycerol (POP) with a 1:1 concentration ratio of OPO and POP. The use of MC crystals made of POP and OPO for edible applications, such as margarine, is advantageous due to no‐trans, low‐saturated, and high‐oleic fats. Industrial manufacturing technology involves rapid cooling processes, and the kinetic properties of crystallization of MC of OPO and POP are required. In this study, we clarified the crystallization of MC of OPO and POP under rapid cooling at rates of 1–150 °C min−1, using synchrotron radiation time‐resolved X‐ray diffraction and differential scanning calorimetry methods. The main results are as follows: (1) POP and OPO crystallized in separate manners without the formation of MC crystals under rapid cooling (>40 °C min−1), while MC crystals started to form with decreasing rates of cooling in addition to the POP and OPO crystals (<30 °C min−1); (2) metastable and stable forms sub‐α, α, β′, and β of POP and OPO were formed, whereas the MC crystals of β were formed during the cooling processes; and (3) the heating processes after crystallization by rapid cooling caused separate melting of the metastable and stable forms of POP and OPO crystals and the formation of MC crystals of β made of POP and OPO, as well as melting of the MC crystals alone.

An Insight into the Solid-State Miscibility of Triacylglycerol Crystals

“…Thus, valuable information for fat systems can be obtained from TAG mixtures when close to real manufacture conditions are employed. For example, the application of varying cooling rates (1 to 150 °C·min −1 ) has shown to influence the crystallization behavior of POP/OPO mixtures in a way that the single crystallization of molecular compound is limited to relatively slow cooling, whereas the system tends to complete immiscibility when the rate is sufficiently increased [ 47 ] ( Figure 7 ).…”

“… Crystallization behavior of 50POP/50OPO mixtures from low to very high cooling rates. Adapted with permission from [ 47 ], © 2018 American Oil Chemist’s Society. …”

“…In addition to the intrinsic properties of TAG molecules, the crystallization and polymorphic behavior of lipids have shown to be strongly dependent on processing conditions [ 14 ], such as the application of shear rates [ 30 , 31 , 32 , 33 ], sonication [ 34 , 35 , 36 ] or emulsification [ 37 , 38 , 39 , 40 ]. Moreover, special attention has been paid to the influence of dynamic thermal treatments of cooling and heating on the polymorphic crystallization and transformation of TAGs, their mixtures, and more complex fats [ 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ], which become of special relevance from an industrial point of view [ 28 , 50 ].…”

Mixing Ratio and Cooling Rate Dependence of Molecular Compound Formation in OPO/POP Binary Mixture

“…Further, to crystallize these oils and fats together, rapid cooling is usually performed using a scraped-surface heat exchanger during the manufacturing process [3]. The cooling rate is estimated to be ≥100 • C min −1 [4], and the products solidify when cooled. Although various physical changes such as shearing and pressure are observed when using a scraped-surface heat exchanger, we treated rapid cooling as the first step to clarify the crystallization behavior of edible oil and fat products.…”

“…The lattice structure of the crystal polymorph was clarified by X-ray diffraction measurement. Table 1 summarizes the values of the long and short spacings in the typical polymorphs of oils and fats [4,[7][8][9][10]. Table 1.…”