Recently, research on the structures, physical properties, and functionality of oleogel as a solid component for oily foods has been rapidly developed. In the oleogel, about 90% or more liquid oil is entrapped and immobilized by the network of gelators and it is necessary to cool the sol state, in which the liquid oil and the gelators are mixed at a high temperature, to form a dense network of the gelators. Previous studies have clarified the basic physical properties of oleogel using various gelators, and active research has been conducted on its application not only to oily foods such as margarine, shortening and ice cream, but also to alternative meats. This paper discusses possibilities and problems associated with the application of the oleogels to foods.

Technical methods for controlling the hardness of wax-gels in which waxes are used as the solidifying agent are described. The hardness of the wax gel varies by the type of oils or the mixture of waxes, and the difference in the hardness is related to the shape of wax crystals in the gel and the card-house structure formed by them. The gelling abilities of plant-derived waxes are generally inferior to those of hydrocarbon waxes, but the hardness can be increased by adding long-chain ester waxes or high-melting-point higher alcohols.

Thermosensitive gels can alter their shape, strength, or physicochemical properties in response to the change in temperature. One of thermosensitive gels is stearyl acrylate (SA) organogel swollen with oil or organic solvent. There is also a copolymer hydrogel with SA and a hydrophilic monomer. These gels are synthesized by a free radical polymerization. These gels show similar thermosensitive properties such as a hard-to-soft transition and a shape-memory function. Thermosensitive properties occur on the basis that the hydrophobic stearyl side chains form a crystalline lamellar structure at temperatures below the crystallization temperature and their packing becomes amorphous at temperature above the melting temperature. The pulsatile (on-off) drug release using the SA organogel was successfully conducted: release was halted at 36°C and release occurred at over approximately 40°C.

Low-molecular-weight oil gelators have been attracting attention in recent years, because gelators suitable for various applications, such as gel physical properties, temperature characteristics, and stimulus responsiveness, can be developed through precise molecular design. In this paper, we introduce the gelling ability of long-chain alkyldiamide-type low-molecular-weight oil gelators (two types of gelators; dicarboxylic amidoamine-type oil gelators and asymmetric diamide-type oil gelators) for various oils, and the relationship between molecular structures such as alkyl groups and lipophilic groups and solution properties.

A low-molecular-weight gelling agent is an additive that forms a self-assembled structure in a solvent with a compound of molecular weight 1,000 or less to increase the viscosity or to gel the solvent. While there are many commercial water-based viscosity-increasing /gelling agents, the number of non-aqueous (hydrophobic fluid) products is remarkably small. Such additives are often discovered by chance. We believe, however, that it is necessary to proceed with development while aiming to establish guidelines for the molecular design of additives. In this paper, based on our research into pyromellitic acid tetracarboxamide, we introduce a series of studies including the molecular design of effective viscosity-increasing and/or gelling agents for hydrophobic fluids, and evaluate their rheological properties and the scale-up of reactions.