Polymorphic occurrence and crystallization rates of tristearin/tripalmitin mixtures under non‐isothermal conditions

Abstract

The effect of composition and cooling rate on polymorphic occurrence and crystallization rates in binary mixtures of tripalmitoylglycerol (PPP) and tristearoylglycerol (SSS) has been studied using differential scanning calorimetry (DSC), light microscopy and X-ray diffraction under constant cooling rates. In general, b and b' polymorphs were observed at cooling rates of 0.5 K/min and less, and the a form at higher cooling rates. Double peaks were observed in the DSC exotherms of mixtures containing more than 30% SSS. The X-ray data showed that, when cooling at 0.5 K/min, the double peaks correspond to the crystallization of the a and b' forms. However, when cooling at 1 K/min and higher, the double peaks appear to arise from the crystallization of two a phases -one PPP rich and the other SSS rich. Light microscopy experiments also show two distinct morphologies, which corroborates this view. The apparent SSS-rich phase crystallizes as irregular spherulites whereas the apparent PPP-rich phase forms a fine crystal mass. Analyses of thermograms relating to the a form show that the amount of supercooling at the onset of crystallization is virtually independent of composition. However, peak width information shows that, once started, pure-component samples crystallize faster than mixtures.

Moisture barrier and physical properties of acetylated derivatives with increasing acetylation degree

“…In the A2 and M products, bimodal endothermic peaks are visualized with the lowest peak due to the presence of diacetylated compounds (at 38.75 6 0.11 7C and 45.13 6 0.35 7C, respectively) and a higher peak (at 50.42 6 0.59 7C and 60.52 6 0.04 7C, respectively) due to non-acetylated stearin and palmitin fractions. TC18 presents three transition peaks characteristic of the three polymorphs, a (here at 55.30 6 0.30), b', and b (here at 67.90 6 0.50), of tristearin at temperatures close to the values reported in the literature [21]. The presence of a small fraction of tripalmitin only induces a slight decrease in the temperature of the two lower peaks and may have increased their relative surfaces compared to the third peak.…”

Exploring concentration, surface area and surface chemistry effects of colloidal aggregates on fat crystal networks

“…4b are centred around 48.45 C, showing that the a polymorph is formed under the conditions of our experiment. This result is corroborated by the data of Himawan et al 15 This study focuses on the crystallization onset temperatures and melting peak temperatures since these are well dened values. However, it is also possible to extract crystallization and melting enthalpies which are related to the area of the peaks.…”

Induction Periods for Lipid Crystallization of Various Vegetable Oils

“…Crystallization behaviors under non-isothermal conditions have been commonly investigated using differential scanning calorimetry DSC 17 , although we mainly investigated the induction period during isothermal storage to understand the processes transpiring during chilled or frozen storage of lipid-containing food. A difference in the melting behavior of rapeseed oil has been recognized between isothermal and non-isothermal storages 13 .…”