Phase behavior of a binary lipid shortening system: From molecules to rheology

Abstract

The phase behavior of fully hydrogenated canola oil in soybean oil was investigated using iso-solid lines from temperature-controlled pulse-NMR along with DSC data, with the rate of cooling of crystallized samples kept constant. The molecular diversity within the fat system was investigated using HPLC and GC. The microstructure of the fats was determined using a temperature-controlled polarized light microscope, and the polymorphism of the solidified fat structures was determined via a temperature-controlled X-ray diffractometer. Hardness was measured by a temperature-controlled Instron mechanical analyzer with a penetration cone. The phase behavior predicted by the DSC and iso-solid lines did not account for the hardness trends observed, as the microstructure and polymorphism of the fat also played a significant role. The addition of hard fat to a system did not consistently increase the hardness of the fat system. Furthermore, the solution behavior demonstrated by the iso-solid line diagram did not account for all trends in melting behavior, as both intersolubility and polymorphic changes occurred simultaneously. It was found that variations in hardness can be inferred from structural changes, although the structural level causing variation differs.A phase is a domain, homogenous with respect to chemical composition and physical state (1). A natural fat is an example of a system of coexisting homogeneous domains in equilibrium. The relationship and occurrence of phase change in a fat system is referred to as the phase behavior of the fat. Phase behavior, characterized by the study of the solid fat content (SFC), is important in optimizing production processes and maintaining production quality, and has been used to predict important attributes such as mouthfeel and hardness in fat-containing food products. Studies on phase behavior also lead to a better understanding of the ways in which fat blends interact-an important understanding, because the large-scale industrial production of shortenings and other fat-containing products often requires blending of lipids from many different sources.The use of iso-solid lines to characterize phase behavior is important in illustrating some aspects of intersolubility but is ultimately limited in scope. In many instances, iso-solid line behavior may not indicate changes in polymorphism of the samples and certainly does not impart information beyond the prediction of hardness by SFC, a method that has been shown to be imperfect (2-4). On the other hand, DSC phase measurements can reflect changes in polymorphism as well as intersolubility. However, such changes are not attributable to either polymorphic or intersolubility effects alone when utilizing purely DSC data. Therefore, it is important to study phase behavior by using a number of different techniques, such as X-ray diffraction (XRD; 5), microstructure analysis, GC, and cone penetrometry.The fat systems used in this study are mixtures of fully hydrogenated canola and soybean oils. These two lipids were selected for stu...

Thermal Behavior, Microstructure, Polymorphism, and Crystallization Properties of Zero Trans Fats from Soybean Oil and Fully Hydrogenated Soybean Oil

“…Means among duplicate sample injections blends, with coefficients of determination (R 2 ) higher than 0.90, as in Figure 3. A similar relation among these parameters and hardfats concentration is observed by Humphrey et al 42 and by Humphrey and Narine 43 in studying blends containing various liquid and fully hydrogenated oils.…”

“…DeMan et al 66 report the β′ polymorph in fully hydrogenated canola oil, which characteristically tends to β stabilize. Humphrey et al 42 , evaluating polymorphic behavior in soybean oil/fully hydrogenated canola oil blends, found that the polymorphic forms varied with the concentration of fully hydrogenated canola oil in the samples. According to Metin and Hartel 30 and Kloek et al 52 , the persistence of β′ crystals in cases where stabilization is preferentially β-type probably results from the formation of mixed crystals, which may be favored by the triacylglycerol composition of the blend and by the tempering protocol used, particularly when a high degree of super-cooling occurs.…”

The binary phase behavior of 1,3-dimyristoyl-2-stearoyl-sn-glycerol and 1,2-dimyristoyl-3-stearoyl-sn-glycerol

“…Binary mixtures of MMS/MSM were prepared in molar ratios of 0.0, 0.1, 0.2, 0.4, 0.6, 0.8 and 1.0 as a function of MSM composition. Samples were prepared as detailed elsewhere (Humphrey et al, 2003).…”

Interesterificação química e enzimática de misturas de estearina de palma, óleo de coco e óleo de canola para formulação de margarinas com baixa concentração de isômeros trans

“…The original blends showed a prominent peak in the crystallization curve, which characterizes the trisaturated fraction of palm stearin and palm kernel oil, containing high melting point triacylglycerols. These results confirmed those of Humphrey, Moquin, and Narine (2003), which showed that an increase in the number of molecules with simultaneous crystallization leads to a larger energy release by the system. Enzymatic interesterification resulted in the appearance of other peaks in the crystallization curves, which is characteristic of the increase in the middle-melting-point TAG (SSO, SOO, and POS) content due to the exchange of acyl groups between TAGs.…”