Smart Nonaqueous Foams from Lipid-Based Oleogel

Abstract

Oil foams are composed of gas bubbles dispersed in an oil phase. These systems are scarcely studied despite their great potential in diverse fields such as the food and cosmetic industries. Contrary to aqueous foams, the production of oil foams is difficult to achieve due to the inefficiency of surfactant adsorption at oil-air interfaces. Herein, we report a simple way to produce oil foams from oleogels, whose liquid phase is a mixture of sunflower oil and fatty alcohols. The temperature at which the oleogel formed was found to depend on both fatty alcohol chain length and concentration. The air bubbles in the oleogel foam were stabilized by fatty alcohol crystals. Below the melting temperature of the crystals, oleogel foams were stable for months. Upon heating, these ultrastable foams collapsed within a few minutes due to the melting of the crystal particles. The transition between crystal formation and melting was reversible, leading to thermoresponsive nonaqueous foams. The reversible switching between ultrastable and unstable foam depended solely on the temperature of the system. We demonstrate that these oleogel foams can be made to be photoresponsive by using internal heat sources such as carbon black particles, which can absorb UV light and dissipate the absorbed energy as heat. This simple approach for the formulation of responsive oil foams could be easily extended to other oleogel systems and could find a broad range of applications due to the availability of the components in large quantities and at low cost.

Non-aqueous foams: Current understanding on the formation and stability mechanisms

“…The determination of the solubility boundary is the main parameter to determine for these systems before studying the foaming properties. The Differential Scanning Calorimetry (DSC) is a useful technique to determine both the temperature at which the crystals begin to melt and the temperature at which this melting process is over [35]. The solubility limit can be approximated in these systems as the temperature at which the melting is finished.…”

“…The foamability and foam stability depend on the size, shape and concentration of the crystals ; these parameters are linked to both the properties of solvent and the molecular structure of the foam stabilizer. Crystalline particles from various systems have been used to obtain non-aqueous foams: mono or diglycerol fatty ester [30][31][32][33]37], mixture of mono and diglycerides [34], fatty alcohol [35], fatty acid [11] or sucrose ester and sunflower lecithin [36] (Tab.2). Myristic acid and fatty alcohols crystallize into two-dimensional plate-like crystals [11,35].…”

Stability of bubbles in wax-based oleofoams: decoupling the effects of bulk oleogel rheology and interfacial rheology

“…Oleofoams are more difficult to stabilise compared with aqueous foams, because of the limited availability of non-aqueous foaming agents (Heymans et al 2017). Recent studies have shown that the addition to vegetable oils of crystallising agents such as fat (Brun et al 2015;Mishima et al 2016;Binks and Marinopoulos 2017), fatty alcohol (Fameau et al 2015), fatty acid (Binks et al 2016), or food-grade emulsifier (Gunes et al 2017;Heymans et al 2018) crystals improves the foamability and stability of the resulting oleofoams. The benefits of such systems include a long shelf-life at above refrigeration temperatures and a reduced need for additives, which are desirable features for consumers.…”

Synthesis, physicochemical properties, and health aspects of structured lipids: A review

“…Oil foams, also called oleofoams, non-aqueous foams, or whipped oils, refer to a colloidal dispersion where air bubbles are dispersed in oils (Figure 3d; Heymans et al, 2018), which can be used as low-calorie food products (Gunes et al, 2017) and lubricating oil (Binks, Davies, Fletcher, & Sharp, 2010). Crystalline particles including MAGs (Gunes et al, 2017;Heymans et al, 2018), DAGs (Shrestha, Shrestha, Sharma, & Aramaki, 2008;Shrestha, Shrestha, Solans, Gonzalez, & Aramaki, 2010), TAGs (Binks & Marinopoulos, 2017;Mishima, Suzuki, Sato, & Ueno, 2016), fatty acids (Binks, Garvey, & Vieira, 2016), fatty alcohol (Fameau et al, 2015), and a combination of sucrose ester and lecithin (Patel, 2017d), as well as solid particles such as fluorinated particles (Binks, Johnston, Sekine, & Tyowua, 2015), have been reported to be capable of stabilizing air-oil interface in oil foams. Here, we mainly focus on edible oil foams stabilized by crystalline MAGs and DAGs.…”