|KOGA, CLARISSA - University Of Illinois|
|LEE, YOUNGSOO - University Of Illinois|
Submitted to: Food Structure
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/9/2015
Publication Date: 4/10/2015
Citation: Hwang, H., Kim, S., Evans, K.O., Koga, C., Lee, Y. 2015. Morphology and networks of sunflower wax crystals in soybean oil organogel. Food Structure. 5:10-20.
Interpretive Summary: This study gives the detailed structural information of sunflower wax crystals formed in the soybean oil organogel. Organogel has received considerable attention as a material that may potentially produce trans-fat free, low saturated fat-containing margarines and spreads. Sunflower wax is a very effective organogelator for soybean oil. However, no one has a good understanding of what makes this material so effective. It is important to understand factors affecting gelation ability to further utilize this technology for development of food products such as trans-fat free, low saturated fat-containing margarines and spreads. For the first time, we found that sunflower wax forms numerous extremely thin crystals in the soybean oil organogel and this crystal shape is much more effective than conventional trans-fat containing materials for greater firmness. Therefore, it was concluded that this crystal shape is responsible for the earlier experimental result that the small amount of sunflower wax could replace a large amount of hydrogenated vegetable oil containing trans-fats.
Technical Abstract: While sunflower wax has been recognized as an excellent organogelator for edible oil, the detailed morphology of sunflower wax crystals formed in an edible oil organogel has not been fully understood. In this study, polarized light microscopy, phase contrast microscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM) were utilized to identify crystal morphology of sunflower wax in 5% sunflower wax-soybean oil organogel prepared at the cooling rate of 2.8-3.0 °C/min. Phase contrast microscopy gave better information than polarized light microcopy about the detailed shape of crystals. Phase contrast microscopy, SEM and AFM revealed that sunflower wax forms extremely thin plate-like crystals under the given experimental conditions. AFM showed that the thickness of these crystals typically range from 100 to 250 nm. Pure wax esters also could produce the thin plate-like crystals in soybean oil indicating that the major ingredients in sunflower wax, wax esters, are responsible for the crystal morphology. The study on the effect of the medium on crystal morphology showed that the crystal morphology significantly depends on the medium while sunflower wax inherently has the tendency to form the plate-like crystals. Sunflower wax could form thin plate-like crystals in the medium containing a long alkyl chain such as triacylglycerols, methyl fatty esters and octadecane. The exceptionally strong gelation ability of sunflower wax could be explained by the effectiveness of immobilization of oil with the numerous thin plate-like crystals formed in the organogel.