Agar | Description, Uses, & Properties - Encyclopedia Britannica

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External Websites

• Food and Agriculture Organization of the United Nations - Production, Properties, and Uses of Agar
• IOPscience - IOP Conference Series: Earth and Environmental Science - Preliminary Characterization of Seaweed Agar Sheet Products: Case Study of Local Small and Medium Enterprise in Java Island
• Nature - Benefits of seaweed
• Science Buddies - All About Agar
• Eprints at CMFRI - Agar production from Gracilaria with improved qualities (PDF)
• WebMD - Agar - Uses, Side Effects, and More
• The Pharma Innovation Journal - Agar-agar extraction, structural properties and applications: A review
• National Center for Biotechnology Information - PubMed Central - Beyond Agar: Gel Substrates with Improved Optical Clarity and Drug Efficiency and Reduced Autofluorescence for Microbial Growth Experiments
• USDA Agricultural Marketing Service - Agar-Agar (PDF)

Ask the Chatbot a Question Also known as: agar-agar Written and fact-checked by Britannica Editors Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... Britannica Editors Last updated Dec. 12, 2025 •History Table of Contents Table of Contents Ask the Chatbot

agar, gelatin-like product made primarily from the red algae Gelidium and Gracilaria (division Rhodophyta). Best known as a solidifying component of bacteriological culture media, it is also used in canning meat, fish, and poultry; in cosmetics, medicines, and dentistry; as a clarifying agent in brewing and wine making; as a thickening agent in ice cream, pastries, desserts, and salad dressings; and as a wire-drawing lubricant. Agar is isolated from the algae as an amorphous and translucent product sold as powder, flakes, or bricks.

Also called: agar-agar (Show more) Related Topics: red algae Gelidium Gracilaria homopolysaccharide phycocolloid (Show more) On the Web: National Center for Biotechnology Information - PubMed Central - Beyond Agar: Gel Substrates with Improved Optical Clarity and Drug Efficiency and Reduced Autofluorescence for Microbial Growth Experiments (Dec. 12, 2025) (Show more) See all related content

Although agar is insoluble in cold water, it absorbs as much as 20 times its own weight. It dissolves readily in boiling water; a dilute solution is still liquid at 42 °C (108 °F) but solidifies at 37 °C (99 °F) into a firm gel. In its natural state, agar occurs as a complex cell-wall constituent containing the polysaccharide agarose with sulfate and calcium.

This article was most recently revised and updated by Melissa Petruzzello.