How Yerba Mate is Processed
There are 3 main ways by which yerba mate is cultivated and harvested. By wild harvesting from the natural forest, by a mixed system combining forest growth with better cultivation practices, and through cultivated plantations. The latter is the most efficient method and is the primary method used in Argentina, the largest producer.
But before yerba mate is packaged for the consumer, it goes through several stages of processing.
The yerba mate plants are sprouted under carefully controlled conditions, then the plants are taken to the fields for planting. After 5-7 years the yerba mate tree is ready for harvesting. The production process begins by harvesting fresh mate leaves and stems, bagging, and transporting the bags to the processing facility. The leaves contribute to the intensity of flavor while the stems contribute a delicate balance, creating a softer flavor. Processing varies depending on the producer and what the intended style and flavor is for the final product.
There are several steps to the process.
Step 1 – Blanching. The leaves and stems are flash heated for 10 seconds to 3 minutes to break the epidermis and stomata in order to halt oxidation and deactivate leaf enzymes.
Step 2 – Drying. The blanched leaves are placed into drying chambers. There they may or may not be subjected to smoke, either filtered or unfiltered, and heat of 212 degrees Fahrenheit in order to dry the leaves to 4.5% humidity. This could take 8-24 hours. Organic yerba mate must not be smoked.
Step 3 – Aging. The dried product is placed in special bags, cement or cedar aging chambers. They may remain here for as long as 24 months. The aging process helps to develop the flavor. The longer the time the softer (less bitter) the flavor. The color changes during aging from a deep bright green to a pale green.
Step 4 – Milling. This step is important because the cut of the leaves and blend affects the taste of the infusion. The leaves, dust, and stems are separated and then combined to specific proportions.
Step 5 – Packaging. Important to preserve the qualities of a good yerba mate tea.