Low-calorie sugars offer new way to solidify vegetable oils and gels
Researchers at the City College of New York have reported the successful transformation of vegetables oils into a semi-solid form using low-calorie sugars as a structuring agent.
The findings, which were published on 15 November 2013 in the Journal of Agricultural Food Chemistry, could provide an alternative to structured oil products produced using saturated or trans fatty acids, which have been linked to coronary artery disease, obesity and diabetes.
Oils are transformed to semi-solid forms known as structured oils. The best known of these are vegetable oil and margarine. Structured oils are also contained in confectionery and cake frosting.
The researchers, led by City College Professor of Chemistry Georg John, tested two sugar alcohol-based gelators, mannitol dioctanoate (M8) and sorbitol dioctanoate (S8), as structuring agents for four refined vegetable oils purchased at local grocery stores: canola oil, olive oil, soybean oil and grapeseed oil. Both M8 and S8 are amphiphiles (molecules that are attracted to water and fats) consisting of two octanoic acid chains (C8) appended to a sugar alcohol molecule.
"We have demonstrated the first sugar-based thickening agents for oil," said Professor John, whose previous investigations into the use of amphiphiles to solidify oil in the presence of water demonstrated their potential use in oil spill cleanups.
Professor John added that each of the two agents identified meet both US Food and Drug Administration (FDA) and GRAS (Generally Recognised as Safe) safety specifications, which means they could be used for food processing.
M8 and S8 produced stable gels
Researchers said both M8 and S8 "demonstrated excellent gelation tendencies" for all the oils that were tested, and the gels remained stable for several months. When mixed with the oils, the gelation agents self-assembled into three-dimensional crystalline networks that encapsulated the oils in liquid stage. Optimal gelation was achieved at structuring agent concentrations between three per cent and five per cent.
Differences between M8 and S8
However, the researchers said some differences between the two agents were reported. For example, M8 gels were opaque in appearance, while those made with S8 were translucent. This was because M8 yields a more densely packed network while the network of S8 gels consisted of needle-like microcrstallites.
M8 was found to be a more efficient gelator, producing stronger gels. However, Professor John said that S8 gels, which had finer structures and appeared more translucent, would be better suited to specific applications.
"The multi-functionality and tunability of sugar-based gelators presents opportunities to develop next-generation oil thickeners," Professor John said.
The research team also included Swapnil R Jadhav and Hyeondo Hwang from City College and Qingrong Huang from Rutgers University.
