Oleogels are lipid-based soft materials composed of large fractions of oil (> 85%) developed as saturated and hydrogenated fat substitutes to reduce cardiovascular diseases caused by obesity. Promising oleogels are unstable during storage, and to improve their stability careful control of the crystalline network is necessary. However, this is unattainable with state-of-the-art technologies. We employ ultrasonic standing wave (USSW) fields to modify oleogel structure. During crystallization, the growing crystals move towards the US-SW nodal planes. Homogeneous, dense bands of microcrystals form independently of oleogelator type, concentration, and cooling rate. The thickness of these bands is proportional to the USSW wavelength. These new structures act as physical barriers in reducing the migration kinetics of a liposoluble colorant compared to statically crystallized oleogels. These results may extend beyond oleogels to potentially be used wherever careful control of the crystallization process and final structure of a system is needed, such as in the cosmetics, pharmaceutical, chemical, and food industries. Abbreviations USSW Ultrasonic standing wave HIU High-intensity ultrasound Oleogels are lipid-based materials that contain 85%-99.5% liquid oil trapped in a network of structuring molecules called oleogelators 1. Oleogels were developed during the last 15 years as saturated and hydrogenated fat substitutes 2. Saturated fats are used in the food, cosmetics, and pharmaceutical industries due to their ability to form solid and crystalline structures at room temperature. These crystalline structures are employed as delivery and protective systems and structuring agents 3. However, excessive consumption of saturated fats correlates with obesity that in turn causes cardiovascular diseases, metabolic syndrome and type-2 diabetes 4-6. Obesity is a global problem. In 2014, 2.5 billion adults and 41 million children worldwide were overweight or obese; these numbers have doubled since 1980 7. The annual healthcare costs related to treating diseases caused by/related to obesity is 60 billion euros in Europe 8 and 210 billion dollars in the USA 9. Lowering the intake of saturated fats, for example, by using oleogels rich in polyunsaturated fatty acids can help reduce cardiovascular diseases caused by obesity. Oleogels can be prepared using direct 1 and indirect 10 methods. Indirect methods are foam, emulsion and solvent exchange and aerogel templating where proteins or polysaccharides are used to prepare the scaffold in which oil is absorbed/retained 10. The direct method makes use of self-assembling molecules (e.g. monoglycerides, waxes, fatty acids, fatty alcohols, ethyl cellulose, phytosterols, phytosterol esters, etc.) to gel the oil 1. Structuring agents are dispersed into the oil, and then a heating and a cooling step are successively applied. The oleogelators rearrange themselves during the cooling step to form a crystalline/polymeric network. The network entraps the oil and gels the system 11. The direct method is...

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Ability to control the structure of water- and lipid-based materials is important when tailoring their mechanical, thermal, and sensory properties in e.g. food, cosmetic, pharmaceutical, and chemical applications. We present an approach for organizing solid particle dispersions and lipid crystals during their formation using ultrasonic standing waves (US-SW). We designed and built a chamber to apply US-SW to water- and lipid-based samples, control their cooling rates, and observe the processes in real time using optical microscopy. As an example, we demonstrated that this process is applicable during the crystallization of saturated fat, the formation of oleogels, and sucrose crystals dispersions. The results indicate ability to control crystalline microstructures in static and dynamic temperature conditions.