Drying of Saffron Petals as a Critical Step for the Stabilization of This Floral Residue Prior to Extraction of Bioactive Compounds

Saffron petals represent floral biomass generally wasted due to rapid deterioration. Previous characterization studies have revealed the presence of bioactive compounds in petals, such as flavonols and anthocyanins. Petal stabilization is a challenge for the efficient isolation of these compounds. This research evaluated three different drying techniques before the solid-liquid extraction of bioactive compounds: oven-drying (40 and 60 °C), lyophilization, and vacuum evaporation (25 and 50 °C). The characterization of the extracts allowed the annotation of 22 metabolites with a quantitative predominance of anthocyanins and derivatives of kaempferol and quercetin. Oven-drying at 60 °C was the most suitable approach for extracting minor compounds, such as crocins and safranal, at concentrations below 1 mg/g dry weight. Vacuum evaporation (50 °C) and lyophilization were the most recommended strategies for efficiently isolating flavonoids. Therefore, drying saffron petals is crucial to ensure the efficient extraction of bioactive compounds.