Lipophilic pigments differentially respond to drying methods in tea (Camellia sinensis L.) leaves

Abstract

This study evaluated the effectiveness of drying methods in tea leaves on lipid soluble pigments. Tea leaves were conventionally steamed, freeze-dried, room temperature-dried, oven-dried, or microwave-dried and afterward 6 lipophilic pigments were identified using the high performance liquid chromatography approach. While conventional drying resulted in evenly distributed total higher pigment metabolites, the freeze drying method resulted in highest levels of chlorophyll, lutein, and β-carotene. Room temperature drying resulted in the lowest contents of pigment metabolites, and the microwave drying method had uniformly moderate levels of metabolites. The levels of these lipophilic pigments were visualized using a heatmap and co-correlated according to the drying method. The principal component analysis scores plot shows that a relatively close linkage appeared between fresh leaves and the room temperature drying method as well as between the conventional and microwave drying methods. The conventional, freeze, room temperature, and microwave drying methods resulted in differential correlations among the pigment metabolites; in other words, drying method affects final ratios of pigment metabolites amongst themselves. Both the freeze drying method as well as the microwave drying method appear to better maintain pigment metabolite contents, compared to the conventional drying method, and could replace the conventional method for these reasons.