Flaxseed extracts are in focus because of their potential application as a food ingredient. Ethanol–water mixtures are recommended for preparation of plant extracts due to their acceptability for human consumption. However, there is a lack of comprehensive studies concerning solvent effect on phenolic profile (phenolic composition and content) and its impact on flaxseed extract antioxidant capacity. This study investigated the effect of ethanol concentration in ethanol–water extraction solvent on the changes in phenolic profile (HPLC analysis after alkaline or alkaline-acid hydrolysis) and the antioxidant activity (DPPH^· and ORAC_FL assays) of flaxseed extracts; various ethanol concentrations were investigated to prepare a suitable extract that could be safely introduced into food. The results showed relationships between the tested factors, i.e. the ethanol concentration and the phenolic content or the antioxidant capacity of flaxseed extracts. The content of phenolic compounds in extracts, including secoisolariciresinol diglucoside, phenolic acids and their glucosides, decreased with increasing concentration of the ethanol from 60 to 90 % in extraction solvent (total phenolics after alkaline hydrolysis were 106.5 and 7.7 mg g⁻¹, respectively). On the contrary, the content of phenolic acid esters was the highest in the 90 % ethanol flaxseed extract. Changes in the phenolic profile with ethanol increase in extraction solvent impacted negatively the radical scavenging activity of the extracts. This study indicates that the mixture of ethanol and water in proportion of 60:40 (v/v) is the most suitable to obtain flaxseed extract with the high content of phenolic compounds and antioxidant activity.

The application of flaxseed extracts as food ingredients is a subject of interest to food technologists and nutritionists. Therefore, the influence of the extraction method on the content and composition of beneficial compounds as well as anti‐nutrients is important. In the study, the effects of two solvent extraction methods, aqueous and 60 % ethanolic, on phenolic and cyanogenic glucoside profiles of flaxseed extract were determined and compared. The impact of extracted phenolic compounds on the antioxidant capacity of the extracts was also investigated. Defatted meals from brown and golden flax varieties were used as extraction material. The ethanolic extraction was more selective for phenolics (100.8–131.7 mg g⁻¹) than the aqueous one (11.5–15.7 mg g⁻¹). However, the contribution of particular phenolic compounds to total phenolics was much more dependent on flax variety than extraction method. A strong relationship was observed between both radical scavenging and ferric reducing activity and the content of phenolics (particularly secoisolariciresinol diglucoside). The correlation between extract chelating ability and phenolics was moderate suggesting that other flaxseed compounds are involved in this activity. The extraction method strongly affected cyanogenic glucoside content of flaxseed extracts; the aqueous extraction caused 96 % reduction in cyanogenic glucoside content (0.56–0.62 mmol g⁻¹) when compared to the content in defatted meal (9.1–11.6 mmol g⁻¹). On the contrary, ethanolic extraction resulted in the high cyanogenic glucoside content in the extracts (71–89 mmol g⁻¹). The results reveals that ethanolic extraction gives extracts rich in antioxidant lignans; aqueous extracts have lower antioxidant activity than ethanolic but cyanogenic glucosides are significantly reduced.

Cannabis sativa (hemp) is a plant considered to be abundant in bioactive compounds. The increasing production of hemp oil is leaving considerable amounts of hemp press cakes (HPC), which have not been sufficiently managed so far. One of the directions of development of plant-based food is the use of by-products of the agri-food industry in accordance with the idea of zero waste and the circular economy, so the purpose of this study was to determine the possibility of HPC fermentation using yogurt and kefir cultures and to determine the effect of the type of starter on the properties of the products. In the present study, starter cultures of yogurt (YO 122) and kefir (commercial grains) were used for HPC fermentation. Changes in lactic acid bacteria (LAB) and yeast population, pH, acidity, the content of bioactive compounds by spectrophotometric methods (proteins, amino acids, polyphenols, flavonoids, reducing sugars) and antioxidant activity (DDPH, ABTS, FRAP and reducing power) were determined. The results showed that it was possible to develop high-value beverages based on HPC with high fermentation efficiency: survivability of LAB and yeast (>10⁶ CFU/g) and acidification (pH in a range of 4.82–6.36 and 5.34–6.49 for yogurt and kefir culture, respectively). Moreover, the stability of hemp protein, with its variable free amino acid composition, antioxidant potential and presented changes in polyphenolic content, was observed during storage. The presented results show a new way to manage HPC as an oil industry residue by using it as a raw material for the development of a bioactive food product and illustrate the relationship between applied starter culture, the direction of fermentation and changes in the content of bioactive compounds.