Characterisation of fibre-rich ingredients obtained from defatted cold-pressed rapeseed cake after protein extraction

Fibre-rich ingredients obtained after protein isolate production from cold-pressed rapeseed meal using alkali extraction at pH 12 with ethanol pretreatment (ingredient 1), and natural deep eutectic solvent (NDES) extraction with choline chloride:urea (ChCl:urea) (ingredient 2) and betaine:citric acid (ingredient 3) were compared in terms of chemical profile, minerals, amino acids, antinutrients, and colour. All ingredients were rich in dietary fibres (46.9 ± 2.36–63.0 ± 1.44 %) and proteins (22.5 ± 0.24–35.5 ± 0.66 %). Minerals, particularly potassium, magnesium, zinc, manganese, and iron, were significantly present. The ChCl:urea system provided the highest lysine and methionine content, with methionine detected only in NDES-extracted ingredients. Glucosinolates were absent in all ingredients. Alkali extraction minimized total phenolic content and tannins, while betaine:citric acid extraction reduced phytates most effectively. NDES systems resulted in better colour parameters. Fibre-rich ingredients exhibit significant potential as functional components for enriching food products, combining high nutritional value with minimized antinutritional factors. • Fibre-rich ingredients were obtained from rapeseed meal using alkali and NDES extractions. • Ingredients were rich in fibers (46.9–63.0 %) and proteins (22.5–35.5 %). • Alkali extraction was the most effective method for minimizing phenolics and tannins. • Betaine:citric acid NDES system reduced phytates most effectively. • NDES systems resulted in better colour parameters.