Whipped oil stabilised by surfactant crystals

Binks, Bernard P.; Garvey, Emma J.; Vieira, Josélio

Abstract

We describe a protocol for preparing very stable air-in-oil foams starting with a one-phase oil solution of a fatty acid (myristic acid) in high oleic sunflower oil at high temperature. Upon cooling below the solubility limit, a two-phase mixture consisting of fatty acid crystals (length around 50 μm) dispersed in an oil solution at its solubility is formed which, after whipping, coat air bubbles in the foam. Foams which do not drain, coalesce or coarsen may be produced either by increasing the fatty acid concentration at fixed temperature or aerating the mixtures at different temperatures at constant concentration. We prove that molecular fatty acid is not surface-active as no foam is possible in the one-phase region. Once the two-phase region is reached, fatty acid crystals are shown to be surface-active enabling foam formation, and excess crystals serve to gel the continuous oil phase enhancing foam stability. A combination of rheology, X-ray diffraction and pulsed nuclear magnetic resonance is used to characterise the crystals and oil gels formed before aeration. The crystal-stabilised foams are temperature-sensitive, being rendered completely unstable on heating around the melting temperature of the crystals. The findings are extended to a range of vegetable oil foams stabilised by a combination of adsorbed crystals and gelling of the oil phase, which destabilise at different temperatures depending on the composition and type of fatty acid chains in the triglyceride molecules.

Citation

Binks, B. P., Garvey, E. J., & Vieira, J. (2016). Whipped oil stabilised by surfactant crystals. Chemical science, 7(4), 2621-2632. https://doi.org/10.1039/c6sc00046k

• Journal Article Type: Article
• Acceptance Date: Mar 2, 2016
• Online Publication Date: Mar 3, 2016
• Publication Date: Apr 1, 2016
• Deposit Date: Mar 9, 2016
• Publicly Available Date: Nov 23, 2017
• Journal: Chemical science
• Print ISSN: 2041-6520
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 7
• Issue: 4
• Pages: 2621-2632
• DOI: https://doi.org/10.1039/c6sc00046k
• Keywords: Whipped oil
• Public URL: https://hull-repository.worktribe.com/output/412503
• Publisher URL: http://pubs.rsc.org/en/Content/ArticleLanding/2016/SC/C6SC00046K?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2FSC+%28RSC+-+Chem.+Sci.+latest+articles%29&utm_content=Google+UK#!divAbstract
• Additional Information: This is a copy of an open access article published in Chemical science, 2016, v.7 issue 4.
• Contract Date: Nov 23, 2017