CONICET | Buscador de Institutos y Recursos Humanos

The polymorphic phases of two high stearic high oleic (HSHO) sunflower oil stearins obtained by dry and sol-vent fractionation of the oil with the aim of use them astransfat replacers or cocoa butter equivalent were studied by performing in situ isothermal crystallization studies following the appearance of polymorphic forms by X-ray using synchrotron radiation. Thermal behavior, equilibrium and actual isothermal solid fat content and morphology of phases were also analyzed. Three polymorphic forms were observed when sam-ples were crystallized at 10 °C/min to different crystallization temperatures (Tc ):α, β´2, and β´1. The αform was thefirst polymorph obtained at all temperatures used and in the opposite way expected, at most crystal-lization temperatures it did not disappear whenβ´2orβ´1forms appeared.β´2form crystallized below 16 or 23 °C for soft and hard stearins, respectively. Above those temperatures, the obtained polymorph was theβ´1 form. Theβpolymorphs were not obtained during the times selected for isothermal crystallization. However, β2form appeared at least after 6 h atTcwhile after 48 h of storage at 25 °C theβ1polymorph was the main form. The β2polymorphic form, which is required for chocolate manufacture, has a very short life and was isolated fromβ1by applying cooling/reheating cycles. Theβ1form was the most frequently observed. There-fore, processing conditions must be carefully controlled to obtain the desired polymorphic form during prod-uct manufacturing. This study provides full characterization and quantification of polymorphic phases of HSHO stearins in real time. Results from this study will help optimize processing conditions for the use of HSHO stearins in industrial applications as trans fat replacers and cocoa butter equivalents.

enviar mensaje