Shaping metabolite profile, dehydration kinetics, quality retention, and sorption properties of red water lily (Nymphaea x rubra) petals through drying technology

Abstract

Red water lily petals are rich in bioactive compounds but deteriorate rapidly owing to their high moisture content, which accelerates chemical and microbiological activity. Drying thus extends shelf life. However, information on how drying methods affect drying characteristics, moisture adsorption, and quality, especially metabolite profiles, remains scarce. To address this gap, freeze drying (FD), convective drying (TD; 50 °C, 60 °C, and 70 °C), and intermittent microwave drying (MWD; 450, 720, and 900 W) were applied to investigate drying characteristics, moisture adsorption behaviors, quality attributes, and metabolite profiles of red water lily petals. The correlation between bioactive compounds and antioxidant capacity was investigated to identify key antioxidants. Among five models tested, the Midilli–Kucuk model best described the drying kinetics, with the highest R² (≥0.999) and the lowest χ² (≤1.25E−04), root mean square error (RMSE) (≤8.33E−05), and standard error of estimate (SEE) (≤9.53E−03). MWD reduced drying time by ∼97% compared to TD. Samples subjected to MWD exhibited lower structural shrinkage (51.11%–54.07%) than TD samples (53.99%–62.62%). FD resulted in the highest retention of antioxidant properties, comparable to MWD. Of 125 putatively identified phenolic compounds, 43 compounds (34.3%) exhibited strong correlations with antioxidant activity. Hierarchical cluster analysis showed that MWD at 450 and 720 W produced quality attributes comparable to those obtained with FD. These findings suggest that MWD is a viable alternative to FD for producing functional dried flower ingredients for nutraceuticals, functional foods, and natural pigments.