Polymorphic behavior of sunflower oil stearins

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

Long Beach, California

Congreso; 103rd AOCS Annual Meeting & Expo; 2012

American Oil Chemists' Society

The actual legislation about trans fats encouraged manufacturers to find trans fats alternatives. Very recently, a new variety of sunflower oil has been cultivated in Argentina. This mutant line has a high stearic content (17 to 22%) on a high oleic background. Its stearins have appropriate physical properties to use in chocolate. However, the polymorphism of this new material which is closely related to chocolate shelf life and consumer acceptability was not described yet. Two sunflower stearins obtained by dry or solvent fractionation, were melted and then crystallized at 10°C/min to different crystallization temperatures. Isothermal crystallization was followed using synchrotron radiation X-ray. In both cases, the α-form is obtained after a few minutes for all crystallization temperatures selected (5, 16, 18.5 and 19°C for soft stearin and 10, 23,24, and 25°C for hard stearin). When samples were in the α-form solid fat content was lower than 3% but when polymorphic transition to more stable forms occurred they started to crystallize very rapidly. Hard stearin showed two different β ' forms while soft stearin presented only one β ' form. β -form did not cristallized under the experimental conditions used in this study. To obtain it samples were stored at -20°C for a month.