Red seaweed refers broadly to commercially harvested species within the red algae division (Rhodophyta) that are used primarily as sources of hydrocolloids — agar and carrageenan — for the food industry. While there is significant overlap with the broader category of red algae, “red seaweed” in a food context typically emphasises the species grown or collected for industrial extraction rather than direct consumption.
Carrageenan, extracted from species like Eucheuma, Kappaphycus, and Chondrus crispus, is used as a stabiliser and thickener in dairy products, plant-based milks, processed meats, and many other manufactured foods. Agar, extracted from Gelidium and Gracilaria species, is used as a gelling agent in desserts, confectionery, and as a vegetarian alternative to gelatine.
These seaweed-derived ingredients are present in a wide range of everyday food products sold in Australia, even if consumers rarely encounter the raw seaweed itself.
How it's produced
Red seaweed for industrial use is both farmed and wild-harvested, depending on the species. Eucheuma and Kappaphycus — the dominant carrageenan sources — are farmed extensively in the Philippines, Indonesia, and Tanzania. Farming involves tying seedlings to lines or nets in shallow coastal waters, where they grow for six to eight weeks before harvest.
Wild harvesting of species like Chondrus crispus (Irish moss) and Gelidium continues in Atlantic coastal regions, with harvesters raking or hand-collecting seaweed from intertidal and subtidal areas. After collection, the seaweed is washed, sun-dried or machine-dried, and baled for transport to processing plants where the hydrocolloids are extracted using hot water and alkaline solutions.
What it costs the planet (per kilo)
≈ Estimated from its category — typical for vegetables, not measured for this item yet. Sources & methods →
What comes from this
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