Harvest Stage and Brewing Conditions Impact Mineral Content, Phenolic Compounds, and Antioxidant Capacity of Lemon Balm (Melissa officinalis L.) Herbal Tea

Abstract

Lemon balm (Melissa officinalis L.) is commonly consumed as an herbal tea for its antioxidant health benefits. Young seedlings known as microgreens are popular for their distinct flavors and can contain higher mineral content on a dry weight basis compared to their adult counterparts. However, the use of microgreens for herbal teas has not been previously investigated. In this study, lemon balm was grown to adult and microgreen harvest stages and prepared as herbal teas by brewing with boiled (100 °C) water for 5 minutes and room temperature water (22 °C) for 2 hours. The effects of harvest time and brewing method on the mineral content, phenolic compounds, and antioxidant capacity of lemon balm herbal teas were assessed. Results showed that adult lemon balm tea contained higher total phenolics, total flavonoids, rosmarinic acid, and antioxidant capacity than microgreen teas, with hot preparations containing the highest amounts (p ≤ 0.05). In contrast, microgreen lemon balm teas contained higher amounts of minerals (p ≤ 0.05), including calcium, potassium, magnesium, sodium, phosphorus, copper, and zinc. In general, brewing conditions did not impact the content of most minerals. Overall, the results support the potential of using dried microgreens as herbal teas. Microgreen lemon balm teas prepared hot and cold offer antioxidant compounds and are richer sources of minerals than adult teas. The ease of growth for microgreens offers consumers the opportunity for home preparation of a novel herbal tea beverage.

Keywords: Antioxidant; Herbs; Infusion; Microgreens; Rosmarinic acid; Tea.