Comparison of Chemical Composition and Colour Parameters of Different Mentha Genus Plants Grown under Organic Conditions

Mentha species are one of the world oldest and popular herbs, that are used in cosmetic and food industry, as well as tea for their medical properties. Due the consumer perception of ecological production and aromatic plants production waste utilization the objective of this work was to determine differences in chemical content and colour among different varieties and parts of Mentha plants ecologically grown in Lithuania. In mint leaves there were determined: content of essential oils, dry matter, soluble solids, ascorbic acid, crude fibre, crude ash, photosynthetic pigments and colour CIE L*a*b* parameters. In the case of mint plants stems, the same analyses were performed except ascorbic acid, soluble solids and colour. The highest content of essential oils were found in Mentha spicata L. ‘Moroccan’ and Mentha piperita L. ‘Glacialis’ leaves, while the least in Mentha suaveolens Ehrh. ‘Variegata’. The content of essential oils in the stems was minor and did not depend on mint variety. Plant parts differ significantly in respect of chemical composition. Amount of dry matter in mint leaves and stems was very similar, while crude ash in the leaves was twice higher than in the stems. Content of crude fibre in the leaves did not differ significantly in all investigated varieties and was 3.6 times lower comparing with the stems. Average ratio of chlorophyll a to b in the leaves was equal to 2.78, while in stems equal to 2.83. The lightest was Mentha suaveolens ‘Variegata’, the darkest Mentha spicata L. ‘Moroccan’ and the greenest Mentha piperita L. ‘Swiss’ leaves. Mints and their parts differ in chemical content and can have widespread usage not only for production of high-value natural products but in addition as alternative fibrous biomass plants.