Phytochemical Profile and Bioactivity of Industrial Rapeseed Meal Ethanol-Wash Solutes

Rapeseed meal is a by-product of oil producing industry which contains a high amount of protein (37–42%). To prepare protein isolates, suitable for human nutrition, the industrial rapeseed meal is often subjected to a pre-treatment with aqueous ethanol solution. The aim of the study was to investigate the phytochemical profile and bioactivity of the ethanol-wash solutes (EWS) obtained as a waste product of the main process of the protein isolate preparation from industrial rapeseed meal. Proximate composition analysis revealed that total carbohydrates were more than half of the product (60.63%). The content of hydrolysable reducing sugars was 44.13%, while glucose was 7.22%. The total phenols amounted 13.38%. EWS contained 1.63% total flavonoids and 242.05 µmol/g dry weight glucosinolates. The major components, as determined by GC–MS analysis, were sucrose, turanose and melibiose with 22.68%, 4.08% and 3.97% of total ion current (TIC) of polar compounds, respectively; cetyl alcohol (2.45% of TIC) and methyl oleate (2.08% of TIC) representing nonpolar compounds, and sinapic acid (73.71% of TIC) which was the prevailing substance of the phenolic acids identified in the EWS. The 0.2% EWS, prepared in aqueous 70% ethanol solution, exhibited 70.68% scavenging capability of DPPH radicals and 585.11 µmol Fe2+/g EWS (dry weight) reducing capacity. The product demonstrated limited antibacterial but broad antifungal activity which was expressed against Aspergillus niger (ATCC 1015), Aspergillus flavus, Penicillium sp., Rhizopus sp. and Fusarium moniliforme (ATCC 38932) as determined by the agar-well diffusion assay. Overall, EWS exhibited bioactive capacity, which revealed its potential application as a value-added product in the food and nutraceutical industries or agriculture. The broad-spectrum antifungal activity makes the product a prospective agent for food biopreservation or plant bioprotection.