INFORM September 2024

18 • inform September 2024, Vol. 35 (8)

case of protein or sugars—their use in capillary suspensions may also offer unique functionalities and opportunities for exploration. Capillary suspensions have also been used as a fat alter native for baked goods. One research team made sponge cakes with whey protein-in-oil capillary suspensions. The protein enriched cakes showed similar aeration and sensory properties to the control cake made with margarine. Where other researchers found that wax oleogels produce sponge cakes with textures similar to those made with oil (https://doi. org/10.1039/D2FO00563H). HYBRID OLEOGELS But what if we combined two gelation methods to develop a new material? Capillary suspensions are promising for applica tions where air incorporation and structure are required. Yet, they lack the crystallinity to provide the barrier properties of fat. Wax oleogels produce weaker networks but offer crystal linity. In hybridizing these gelation methods, the wax gel may provide a source of crystallinity, and a barrier to bridging fluid evaporation since it gels the oil. Capillary suspension could provide gel strength and tunabil ity, altering physical properties like crystal shape and wax gel oil binding without increasing the melting temperature or impart ing off-flavors. Studying the way that crystalline networks inter act with particle networks and interfaces adds to the current understanding of both types of oil structuring and could lead to new soft material science and functional food design. Simoes and Rousseau prepared canola oil-continuous cap illary suspensions with glass particles bridged by water and gelled the oil phase with hextriacontane (C36), a hydrocarbon wax (https://doi.org/10.1039/D3SM01619F). The wax was cho sen as a control for surface active. Minor components found in natural waxes may change crystallization kinetics or inter facial properties between the oil and water, affecting capillary force. Glass particles were used as a proxy for food particles since they are non-porous, non-swelling and have a smooth surface. Glass particles are polar because of their surface alco hol groups. These groups also allow for the glass particles to be chemically hydrophobized to understand the effects of particle polarity and to compare networks using particles of the same size distribution. Without water, both polar and non-polar particles pre vented wax oleogel formation. But when wax is added to the capillary suspension a hybrid gel forms. The hybrids have unique properties when compared to a wax oleogel or a capil lary suspension. The capillary suspensions provided substantial network strength in the hybrids, increasing gel firmness. The wax network imparted some brittleness and after scooping the hybrids visually displayed decreased oil loss. The hybrids made with non-polar particles had a surprising gel strength that was greater than the sum of its parts suggesting that there was some interaction between the gelling methods. The hybrid gels showed greater gel strength with lower amounts of water. Yet, without enough water to form the capillary network no gel formed, suggesting that the capillary network is important

the crystals have sintered together. Upon shear, the network is broken and is comprised of dispersed crystal clusters that require re-aggregation through weak Van der Waal forces to reform a network (https://doi.org/10.1021/acs.jafc.5b01548). Capillary suspensions, on the other hand, merely need to have their particle clusters reaggregate to form as strong of a bridge as the original material prior to shear. In other mate rial applications like ceramics, capillary suspensions show the ability to retain their structure, resulting in enhanced proper ties. This only occurs if the network has a secondary method of curing, allowing the particles to irreversibly sinter. If the liquid bridges are a volatile fluid and evaporate, the network returns to a particle-in-oil suspension and the network loses its strength. STRUCTURING EDIBLE OILS WITH FOOD PARTICLES By using particle properties to structure oils, there is no need for additives like wax or more solid fat. Food particles have been used to make capillary suspensions for fat-free spreads and margarines. Non-polar particles like cocoa and starch (https://doi.org/10.1016/j.foodhyd.2014.01.027) and polar particles like proteins (https://doi.org/10.1016/j.food hyd.2024.110073) can give oils solid-like properties with the addition of a small quantity of water. In these cases, without the added water the suspensions would flow like a fluid instead of being spreadable. The water bridges also provide the oppor tunity to add flavors, salts, or sweeteners, that would other wise be insoluble in a lipid phase, leading to more freedom in food formula without the need for emulsifying agents. Since food particles are usually non-spherical, have com plex microstructures, and may even swell or dissolve—in the Capillary suspensions and their structures under scanning electron microscopy. Particles are depicted as grey spheres, connected by blue water bridges surrounded by a yellow oil phase. Increasing water from 3 to 9 percent promotes the formation of spherical agglomerates. Polar particles become part of the agglomerates, non-polar particles tend towards coarse Pickering-like structures, decorating the droplet exterior. Source: Simoes and Rousseau, Soft Matter , 20, 4329-4336, 2024.