Enzyme-Assisted Extraction Enhancing the Phenolic Release from Cauliflower ( Brassica oleracea L. var. botrytis ) Outer Leaves

Phenolic compounds are highly present in byproducts from the cauliflower (Brassica oleracea L. var. botrytis) harvest and are thus a valuable source for valorization toward phenolic-rich extracts. In this study, we aimed to optimize and characterize the release of individual phenolic compounds from outer leaves of cauliflower, using two commercially available polysaccharide-degrading enzymes, Viscozyme L and Rapidase. As major results, the optimal conditions for the enzyme treatment were: enzyme/substrate ratio of 0.2% for Viscozyme L and 0.5% for Rapidase, temperature 35 °C, and pH 4.0. Using a UPLC-HD-TOF-MS setup, the main phenolic compounds in the extracts were identified as kaempferol glycosides and their combinations with different hydroxycinnamic acids. The most abundant components were kaempferol-3-feruloyldiglucoside and kaempferol-3-glucoside (respectively, 37.8 and 58.4 mg rutin equiv/100 g dry weight). Incubation of the cauliflower outer leaves with the enzyme mixtures resulted in a significantly higher extraction yield of kaempferol-glucosides as compared to the control treatment.