Crystallization behavior of high oleic high stearic sunflower oil stearins under dynamic and static conditions

SILVANA MARTINI; JAIME A RINCON CARDONA; YUBIN YE; C Y TAN; ROBERTO J CANDAL; MARIA L HERRERA

Montreal

Congreso; 104th AOCS Annual Meeting & Expo; 2013

American Oil Chemists' Society

The isothermal crystallization behavior of soft (SS) and hard (HS) stearins obtained from high stearic high oleic sunflower oil (HSHOSFO) was studied using polarized light microscopy, differential scanning calorimetry, texture analysis and wide (WAXS) and small (SAXS) angle X-ray scattering with synchrotron source. Samples were crystallized under dynamic conditions (with agitation) and under static conditions at different temperatures. SS samples were crystallized at 16, 17, 18, 19, and 20 °C; while HS samples were crystallized at 24, 25, 26, 27, and 28 °C. Results from this research show that crystallization temperature and shear strongly affect the crystallization of these systems. Both fractions are polymorphic in nature which translates into different crystal morphologies and textures. The first form obtained when samples were isothermally crystallized to crystallization temperature (Tc) was always the -form. Polymorphic behavior strongly changed with Tc for both fractions. SS fractions were characterized by β’1 for lower Tc (16 °C) and β2 or 1 crystals for higher Tc (20 °C) when crystallized under dynamic conditions (shear), while this same fat system was characterized by β’2 crystals at lower Tc (16 °C) and β’1 at higher Tc (20 °C) when crystallized under static conditions. Interestingly, neither β2 nor 1 crystals were observed for SS samples crystallized under static conditions after 90 min at Tc. Similarly, HS samples were mainly characterized by β’1 crystals at lower Tc (24 °C) and β2 or 1 crystals at higher Tc (28 °C) when crystallized under dynamic conditions; while the same fat is characterized by β’2 crystals when crystallized at lower Tc (24 °C) and  and ’1 crystals when crystallized at higher Tc (27 °C) under static conditions. These results suggest that agitation, or crystallization under dynamic conditions promotes the formation of more stable polymorphic forms. These different polymorphic behaviors as a function of Tc are translated in significant textural behavior of the samples.