Discarded roselle seeds produce coffee-like brew with high antioxidant levels after 30-minute roast

Roselle seeds, an often discarded by-product of the Hibiscus sabdariffa plant, could offer a viable caffeine-free alternative to coffee, according to new research in the International Journal of Food Safety, Nutrition and Public Health. The work has looked at the nutritional value of the seeds as well as their taste and aroma. The team found that Roselle seeds roasted for half an hour could be used to brew a beverage that had a flavor, aroma and body very close to traditional coffee and better than many existing substitutes. It was also shown to contain high levels of antioxidant compounds thought to have health benefits.

There is a growing interest in substitutes for coffee, and a market for tasty drinks that do not have the stimulant effects of caffeine. Many of the “herbal” type brews that have been marketed now replicate coffee’s depth of flavor and complexity.

The researchers point out that Roselle is cultivated for its tart, ruby-colored calyces, the outer part or sepals of its flowers. These are used to make teas and syrups. However, the plant also contains protein-rich seeds that take on new chemical properties when roasted.

The team compared unprocessed Roselle seeds with batches roasted for 10, 20, and 30 minutes. They measured bioactive components including antioxidant flavonoids and phenols, as well as tannins and saponins. They found that roasting consistently increased the concentration of these potentially beneficial molecules.

However, it was the sensory testing that was perhaps most important and revealed the true potential of the Roselle seed as a coffee substitute. Participants rated the 30-minute roast highest for flavor, taste, body, and overall acceptability. While the Roselle brews were no real competition for commercial coffee for coffee lovers, the longer roast did score close to true coffee.

If Roselle seeds can be developed into a satisfying, caffeine-free brew similar to coffee, they could add value to a crop already grown in many tropical regions, reduce agricultural waste and offer consumers a more convincing alternative to coffee in the same way that Rooibos (Aspalathus linearis) and similar products have given tea drinkers an alternative to traditional tea.