The most common application for Agar is the formation of gels. It is used in microbiological growth media at high usage levels (1–2%) as the solid substrate for nutrients. The extreme temperatures in the media sterilization process fully hydrate and activate the gelling functionality once the media is cooled. The gels formed by Agar in water systems are very high in gel strength but exhibit a brittle teF. Agar delivers a set texture and firmness to bakery glazes and icings that are applied warm to donuts and pastries. Agar is also used at lower usage levels to manage moisture in systems using other gelling agents. Thus although Agar gels have a tendency to exhibit syneresis, Agar can be used to manage syneresis from other gelling agents. At low usage levels, Agar is also used to aid in suspension in UHT-processed shelf-stable beverages because of its limited interaction with other functional ingredients (for example, proteins and fat emulsions).
Agar
Common Names
- Agar
- Agar Agar
- Agarose
Functionality
- Gels Formation
- Moisture Control
Quality
- Activation Temperature
- Set Temperature
- Gel Strength
Applications for Agar
Botanical Sources
Agar is isolated from red algae which grow between the rocky shoreline and out to depths of 120 ft. Common algae harvested include the genera of Gelidium, Gracillaria and Gigartinia. The traditional method of polymer extraction includes steeping the seaweed in hot water and purification through a cycle of gelling, freezing, thawing and finally drying into the powder we use as Agar. The heat required for activation and the gelling temperature vary depending on the algae. Locations of harvest include: Spain, Portugal, Morocco, Japan, Korea.
Polymer Chemistry
The carbohydrate polymer of Agar is made of of alternating sub-units of galactose and 3,6 anhydrogalactose linked with β(1-3)-D and α(1-4)-L linkages resulting in a very linear structure. This structure contributes both to the need for extreme temperature for activation and the high gel strength. Heat activation temperature can be as low as 165 F or 74° C or as high as boiling temperature at 212° F or 100° C. The gel set temperature ranges between 95-120° F or 35-50° C. Gel formation occurs in water systems as well as applications with high total solids with or without fat.