Fermented, Freeze-Dried Snacks from Lactarius deliciosus as a Source of Functional Compounds and Lactic Acid Bacteria

Lactarius deliciosus is an edible, seasonal, wild-growing forest mushroom with significant functional properties and potential applications in health-promoting foods. The aim of the study was to compare the level of selected functional compounds (minerals, phenols, indoles, L-phenylalanine, lovastatin, ergothioneine, glucans, chitin, chitosan) and Lactic Acid Bacteria (LAB) in freeze-dried snacks made from the fermented caps of L. deliciosus mushrooms. The snacks were made from mushrooms blanched in water or microwave, and fermentation was carried out using one of the strains of probiotic bacteria: L. acidophilus (LA-5) or L. plantarum (SWA016). After 6 months of storage, mushroom products were a good source of functional compounds, especially LAB, minerals, indoles, lovastatin, antioxidants (phenolic compounds), and dietary fibre. Fermentation with added probiotic cultures enhanced indigenous lactobacilli levels, but after storage, only microwave-blanched snacks fermented with L. plantarum retained a high LAB count (7.3 log CFU/g). The selection of pre-treatment significantly influenced bioactive compound composition: water blanching enhanced lovastatin and 6-methyl-D,L-tryptophan contents, whereas microwave blanching maximised K, S, Rb, Fe, Se, Mn, Br, phenolic compounds, antioxidant activity, and soluble dietary fibre. In order to optimise the level of the most important bioactive compounds and LAB, microwave blanching with the addition of L. plantarum SWA016 should applied.