Pigments in mint leaves and stems
Latvia University of Agriculture, Faculty of Food Technology, Department of Food technology, Liela Street 2, LV 3001 Jelgava, Latvia *Correspondence: evita.straumite@llu.lv
Abstract:
Mint is the genus belonging to the Labiatae family and includes a huge diversity of varieties with different sensory properties. An important quality parameter is its colour, and the compounds responsible for it are pigments such as chlorophyll a and b, carotenoids etc. The aim of the current research was to determine the pigment content in the leaves and the stems of different mint varieties grown in Latvia. Mint of nine varieties (Mentha suaveolens ‘Apple mint’, Mentha suaveolens ‘Variegata’, Mentha spicata ‘Marokko’, Mentha piperita ‘Swiss’, Mentha piperita ‘Granada’, Mentha piperita f. citrate ‘Grapefruit’, Mentha piperita ‘Chocolate’, Mentha piperita ‘Almira’, Mentha piperita ‘Bavarian’) collected in Latvia was analysed. Chlorophyll a, chlorophyll b and carotenoids were determined spectrophotometrically in the acetone extracts of fresh leaves and stems at various wavelength 470, 645 and 662 nm. To analyse a relationship between chlorophyll a and b in the leaves and the stems a calculation of ratio a/b was performed. Additionally the colour of samples was measured in CIE L*a*b* system. For the statistical analysis – linear correlation, analysis of variance, hierarchical cluster analysis was performed. The differences were considered significant at P < 0.05. Among studied mint leaves the highest content of chlorophyll a and b, carotenoids was determined in the ‘Bavarian’ mint. The colour component L* value for variety ‘Bavarian’ leaves was one of the lowest among studied samples (showing a darker colour intensity). The stems of the mint variety ‘Bavarian’ had a high content of chlorophyll especially chlorophyll b. The highest content of carotenoids was determined in Mentha spicata ‘Marokko’. Analysing a relationship between the colour components L*a*b* and the content of pigments no significant correlations were determined.
Key words:
mint varieties; chlorophyll a; chlorophyll b; colour.