In food biotechnology, Pleurotus ostreatus is of great interest as a source of natural antioxidants and angiotensin-converting enzyme (ACE) inhibitors. However, research in this area has not yet been completed. The effect of various drying methods on the structural properties and the rehydration capacity of mushrooms was investigated in this paper. The content of secondary metabolites, the peptide profile, and the antioxidative effect and ACE inhibitory activity of dry mushrooms were investigated in vitro, simulating the process of gastrointestinal digestion. X-ray microtomography has confirmed that structure of lyophilic and sun-dried mushrooms is dominated by open pores, and in mushrooms dried with hot air and microwave, closed pores. Experiments have shown that the conditions of freeze drying and sun drying of Pleurotus ostreatus provide a higher rehydration capacity of dried mushrooms. The maximum activity of radical absorption of the oyster mushroom after microwave drying was observed. The iron restoring capacity of the mushrooms is maximally maintained with microwave drying and hot-air drying. The properties of the antioxidant product with an emphasis on the high activity of inhibiting lipid oxidation of the mushroom maximized after drying in the sun. Mushrooms dried lyophilically and in the sun showed the highest ACE inhibitory activity.

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A comparative analysis of protein and peptide profile, biological activities of hydrolysed bovine colostrum and whey was performed. It was found that the depth of proteolysis, qualitative and quantitative composition of protein component of samples determined the level of their antiradical, antimutagenic, antimicrobial and antigenic properties. SDS electrophoresis of experimental samples revealed more extensive protein hydrolysis in the course of alcalase treatment than during enzymatic reaction with neutrase. Using fluorimetric method the influence of hydrolysis with endopeptidases and fermentation with Lactobacillus acidophilus on antioxidant properties of milk proteins was established. 1.7–5.5 times increase in antiradical activity of derived samples in comparison with native proteins was recorded. Reduction in mutation rate induced by whey hydrolysate in tested strain Salmonella typhimurium TA 98 ranged from 15.7 % to 49.2 %, whereas antimutagenic effect on strain TA 100 varied from 18.8 % to 52.1 %, exceeding the similar values shown by colostrum hydrolysates. Samples of colostrum and whey hydrolysed with alcalase are enriched with specific short-chain peptides which determine their relatively high antimutagenic and antiradical properties. Immunoprecipitation reaction demonstrated effective splitting of β lactoglobulin by alcalase, resulting in production of hypoallergenic hydrolysates. It was found by impedimetric technique that neutrase-cleaved colostrum accounted for maximum inhibition of Escherichia coli АТСС 8739 (82 %) and Staphylococcus aureus АТСС 6538 (19 %). Samples of enzymatic hydrolysates of colostrum and whey proteins with confirmed antimicrobial, antimutagenic and antioxidant action were obtained. The use of hydrolysed and fermented colostrum with elevated antioxidant potential in special nutrition appears extremely promising.

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