Agar can be used as an ingredient in jellies.
Agar, commonly shortened to agar, is a gel-like substance derived from certain types of red algae or seaweed. It has various uses, although most people know it as a culture medium in petri dishes. This substance is also perfectly edible and, in addition to being part of the regional cuisine, it is also used as a thickener in sweets and other foods. Because it is derived from plant material, it has the advantage of being suitable for vegetarians, unlike gelatin, which is derived from animal sources.
Composition and Properties
Agar is derived from certain types of red algae.
Agar actually consists of two substances, called agarose and agaropectin. Agarose is a polysaccharide, a type of polymer in which a large number of small carbohydrate units join together to form much larger molecules. Agaropectin is also a polysaccharide, but it consists of smaller molecules that also contain non-carbohydrate components, such as sulfates.
Agar and bacteria in a Petri dish.
The substance is solid at room temperature, but it melts and solidifies easily. It does not dissolve in cold water, but absorbs large amounts, swelling in the process. Agar dissolves in water near the boiling point and forms a gel, even at very low concentrations.
Production and Supply
Two types of seaweed, Gelidium and Gracilaria, are harvested to produce agar. They are found in many parts of Asia and on the western coast of the United States. Gelidium provides a superior product for certain uses, such as growing bacteria.
Agar has many uses in the fields of microbiology and chemistry.
To extract the substance, the algae are washed and heated in water, causing it to dissolve. Once cooled, it forms a gel with a low concentration of the product. The concentration is increased by a freeze-thaw technique or by squeezing the water under pressure. The rest of the water is then removed by drying with hot air, leaving the solid product, which can be cut into blocks or ground to produce granules, flakes or powder. Some can be further processed to separate agarose, which has some more specialized applications in biochemistry.
Agar is used to make jelly-like foods like gummy bears.
Many supermarkets sell human-grade agar, usually in the same area that has vegetarian alternatives. Laboratory-grade product is sold by scientific supply companies. While food-grade versions can sometimes be used in a laboratory, those intended for scientific use should not be consumed, in case potentially harmful substances have been added to them.
applications
Agar has various uses in the fields of microbiology, biochemistry, and molecular biology. In microbiology, it is one of the most important and widely used materials. Since most microbes cannot digest it, it can, with the addition of the right nutrients, act as a growth medium for bacteria, fungi, and other microorganisms. Microbes feed on the added nutrients but cannot digest the agar, so it remains intact, allowing colonies of organisms to be easily observed and studied.
Laboratory agar usually comes in a very pure powder form, as special steps must be taken to ensure that it is free of microorganisms, spores, and any chemicals that might impede or interfere with the growth of the organisms being cultured. It is dissolved in hot water and cooled, then a suitable nutrient and possibly other chemicals are added, depending on what is being grown. The mixture is poured into Petri dishes, where it forms a gel, and then the materials to be tested are deposited on the surface, usually in strips. The petri dishes can then be incubated at a suitable temperature and observed over a period of days to see what is growing in them. Agarose, extracted from agar, is mainly used as a gel for electrophoresis, a technique that separates different proteins and DNA. fragments based on their size and electrical charge.
Agar also has many uses in cooking and the food industry. In parts of Asia, it is used as an ingredient in soups and jellies. Outside of Asia, the substance appears in a wide variety of foods, along with two other vegetable gelatins, carrageenan and alginate. It’s often used in foods that need to be gelled, but it behaves a bit differently than protein-based jellies, tending to be a bit more viscous and sometimes creates a weird texture. For vegetarians, it makes foods like marshmallows, gummy bears, and gummy bears edible.