Bio-Products Obtained from Broccoli and Cabbage Wastes Are Proposed as Functional Food Ingredients and Bioherbicides for Sustainable Weed Management

Developing processes that contribute to the valorization of vegetable wastes is of great importance since these residues are characterized by being of high quality, having a huge potential for valorization. However, upcycling vegetables residues and defining specific applications for the value-added products obtained might be a challenge, and they should be tackled by means of different and complementary innovations. In the present study, broccoli and white cabbage discards were transformed into powdered products by means of selected techniques and conditions, which have been explored for applications in the agri-food sector. The obtained brassica powders were rich in bioactive compounds such as phenolics and isothiocyanates. Their antioxidant properties in response to in vitro digestion were evaluated to assess the potential of the products as functional food ingredients. On the other hand, brassica powders were tested as bioherbicides. For that purpose, inhibition tests on weed germination and growth of weeds from agricultural soil seedbank and selected species (Lolium rigidum, Papaver rhoeas, Portulaca oleracea, and Echicnochloa crus-galli) were performed under controlled greenhouse conditions. In vitro simulated digestion studies demonstrated that bioactive constituents of powders were progressively released during digestion, and consequently, a part of them could be finally absorbed and, thus, provide their beneficial effect. Brassica bioproducts significantly reduced the germination of weeds from the agricultural soil seedbank, and the selected weed species tested, namely L. rigidum, P. rhoeas, P. oleracea, and E. crus-galli. Powders also showed a negative effect on the root weight and length of dicotyledonous weeds from the soil seedbank and L. rigidum, whereas a stimulatory effect was observed on the spring–summer species, E. crus-galli and P. oleracea. The results of this work contribute to extending the range of applications for brassica industrialization wastes.