06/08/2026
If you enjoy experimenting with herbal teas, here's a technique worth trying. Instead of simply drying raspberry leaves, you can oxidize them to create a tea with a completely different character.
The process is similar to the one used to produce green, oolong, and black teas from the tea plant (Camellia sinensis). Oxidation unlocks new layers of flavor, often bringing out delicate floral, fruity, and honey-like notes that are rarely found in herbs dried in the usual way. The resulting tea can be surprisingly rich and complex, sometimes even reminiscent of fine tea made from the tea plant.
This process is often mistakenly called fermentation. In fact, the transformation is caused mainly by natural enzymes in the leaves. Once the leaves are bruised, these enzymes begin breaking down chlorophyll and transforming tannins and other compounds, creating new aromas, flavors, and the characteristic darker color.
The technique has been used in Russia since the 17th century to prepare tea from fireweed (Chamaenerion angustifolium, Swedish: mjölke), traditionally known as Ivan Chai. The same method also works beautifully with raspberry leaves and many other plants used for herbal teas.
Method:
🌱Harvest and bruise the leaves, by rolling, crushing, or chopping. You want to damage the cells of leaves, this will start the oxidation process.
🌱Press the leaves firmly into a clean jar or other container. Pack tightly.
🌱Keep warm. Leave the container at 40–70 °C for 4–12 hours. I usually wrap my jar in black towel and leave somewhere in sun. During this time, the leaves will darken and develop a sweet, fruity, or floral aroma. The exact time depends temperature, and the flavor profile you prefer. Open your jar, smell and decide when you are happy with results.
🌱Dry the leaves, at 40–50 °C until they are completely dry.
🌱Store and mature. While it can be enjoyed immediately, allowing it to mature for a few months often produces an even deeper, more rounded flavor.
