Agar will solidify under acidic conditions. Agar can solidify under acidic conditions. Agar is a gel derived from seaweed that is capable of forming a gel at elevated temperatures and in acidic environments. When agar is mixed with an acidic substance, such as lemon juice, vinegar or certain fruit juices, the polysaccharide molecules in the agar bind to each other to form a three-dimensional mesh, which causes the mixture to solidify. This is why, when making jellies and desserts, acidic ingredients are added to encourage the agar to solidify. Agar, the scientific name of agar, English name (agar), also known as oceanic vegetables (agar-agar), Haidong vegetable, frozen powder, agar, stone flower gum, swallow vegetable essence, oceanic powder, cold days, large vegetables, is a kind of plant glue, commonly used in the sea of the unicorn vegetable, stone flower vegetable, Gracilaria, etc., made of colorless, non-fixed shape of the solid, soluble in hot water. Widely used in the food industry, also commonly used as a bacterial culture medium.