Functional food obtained from fermentation of broccoli by-products (stalk): Metagenomics profile and glucosinolate and phenolic compounds characterization by LC-ESI-QqQ-MS/MS

This research revalues broccoli stalk by-product as a novel fermented health food, using its autochthonous microbiota. Broccoli stalk slices were packed into glass jars, brine was added (6% w/v), and two dressings were studied: garlic, and mustard seeds. No dressing was used as control. Natural fermentation was carried out at 25 °C for 6 days followed by a further 6 days storage at 4 °C. The identification of individual glucosinolates and phenolic compounds was performed by LC-ESI-QqQ-MS/MS. At day 3, the highest content in functional compounds such as glucoerucin and indolic glucosinolates as glucobrassicin, 4-methoxy-glucobrassicin and 4-hidroxy-glucobrassicin, and phenolic acids and flavonoids as sinapic acid, 4-O-feruloyl quinic acid and quercetin-3-O-diglucoside was found. At day 6, the broccoli stalks reached the maximum counts in lactic acid bacteria (>8 log cfu g⁻¹), remaining stable until day 12 at 4 °C, including as the main genera Lactobacillus and Leuconostoc. Metagenomic analysis identified 1009 bacteria genera; Latilactobacillus sakei was the most predominant lactic acid bacteria species, followed by Lactobacillus curvatus, Leuconostoc kimchi and Leuconostoc carnosum. This is an example of a vegan and functional food product, based on a circular economy model, using broccoli by-products.