Effects of different drying methods on quality of male flowers of Eucommia ulmoides based on color and chemical composition

Abstract

To study the effects of different drying methods on the quality of male flowers of Eucommia ulmoides(MFOEU), we treated fresh MFOEU samples with drying in the shade(DS), vacuum freeze drying(VFD), high-or low-temperature hot air drying(HTHAD, LTHAD), microwave drying(MD), and vacuum drying(VD), respectively. The color, total flavonoid content, total polysaccharide content, and main active components such as geniposide, geniposidic acid, rutin, chlorogenic acid, galuteolin, pinoresinol diglucoside, and aucubin in MFOEU were taken as the evaluation indicators. The quality of MFOEU was comprehensively evaluated by entropy weight method combined with color index method, partial least squares discriminant analysis and content clustering heat map. The experimental results showed that VFD and DS basically kept the original color of MFOEU. The MFOEU treated with MD had higher content of total polysaccharides, phenylpropanoids, lignans, and iridoids. The MFOEU treated with LTHAD had higher content of total flavonoids and that treated with VD had lower content of active components. According to the results of comprehensive evaluation, the quality of MFOEU dried with different methods followed the order of MD>HTHAD>VFD>LTHAD>DS>VD. Considering the color of MFOEU, the suitable drying methods were DS and VFD. Considering the color, active components, and economic benefits of MFOEU, MD was the suitable drying method. The results of this study are of a reference value for the determination of suitable methods for MFOEU processing in the producing areas.