Summary The aim of the study was to estimate the optimum method to obtain water‐soluble (WS‐DF) and alkali‐soluble (AS‐DF) dietary fibres fibres from defatted rice bran (DRB) to develop functional components for food. The different pre‐treatments of DRB, such as ultrasound (US) treatment, hydrolysis by cellulase (HC) and combined treatment (HC‐US), were compared with hot‐water (HWT) treatment on yields, and structural, physicochemical, and functional properties of WS‐DF and AS‐DF. Results showed that amounts of WS‐DF (5.54–9.03 g/100 g) and AS‐DF (7.22–9.58 g/100 g), and total dietary fibre (TDF) (42.21–45.44 g/100 g) obtained from the DRB after US, HC and HC‐US treatments were significantly higher than that after HWT (6.36, 5.65 and 31.92 g/100 g, respectively). The FT‐IR indicated that the effect of applied treatments on the changes of the chemical structure of polysaccharides was stronger for the WS‐DF than that for the AS‐DF. Scanning electron microscopy (SEM) showed that the surfaces of US‐treated DFs particles were much more fractured than those after the HWT and HC. The combined HC‐US treatment at 50°C for 30 min significantly enhanced the purity (85–91%) and homogeneity of RB DFs structure resulting in increased water‐holding, swelling and glucose adsorption capacities compared to conventional processes maintaining acceptable bioactivity. Our study showed that conventional hot water extraction could be replaced with the ultrasonication technology as an effective tool for the modification of rice bran DFs’ structure and functional properties.

A probiotic nutraceutical based on functionalised rice bran (RB) supplemented with lingonberry (Vaccinium vitis-idaea L.) pulp (LP) at various levels (10-50 g/100 g d.w.) was developed. Prior to immobilisation of lactic acid bacteria (LAB) cells, RB-LP matrix was structured by ultrasound (US) (850 kHz; power 160 W) for 20 min at 40 °C. Xanthan gum and sodium alginate were used for the stabilisation of RB-LP matrix. Survival and fermentative activity of the immobilised LAB cells was studied by monitoring pH, cell number, antimicrobial activity, lactic acid and acetic acid production. US treatment increased by 17.5% soluble dietary fibre (SDS) contents in RB but reduced on average by 49.9% hyperoside, quercetin, quercitrin and coumaric acid contents in LP material. RB substrate supplemented with LP (20-50 g/100 g d.w.) resulted in higher antimicrobial activity against Escherichia coli, Salmonella typhimurium and Staphylococcus aureus for Lactobacillus brevis, and against Bacillus cereus and Staphylococcus aureus for Pediococcus acidilactici. RB-LP matrix stabilised with alginate-xanthan and alginate maintained 8.09-8.67 log CFU g À1 live cells of immobilised L. brevis after 7 weeks of storage at 4 °C. In the case of protection under simulated in vitro digestion conditions, RB-LP gels with sodium alginate demonstrated the highest cell survival with 4.25 CFU g À1 viable cells remaining in the product and 5.23 log CFU g À1 live cells in the digestion medium.

In this study, the model gel-type delivery system containing rice bran (RB), lingonberry (Vaccinium vitisidaea L.) press cake (LPC) and thyme essential oil (Thymus vulgaris L.), was developed and evaluated by their texture, gelation rate and antioxidant activity changes during storage and simulated gastrointestinal digestion. For the structuring of the gel-type RB-LPC matrix, a high-intensity ultrasound (850 kHz; 1.3 W cm À2) treatment at 40°C was applied. The release of total phenols and flavonoids was measured during digestion process by a spectrophotometric method and reversed-phase high-performance liquid chromatography (RP-HPLC), respectively. The contributions of xanthan and alginate as gelling agents to improve the stability of the gel texture protecting it from fast degradation under gastrointestinal digestion enable a controlled release of antioxidants, thus improving their biodistribution. Storage temperature influenced the reduction of antioxidant activity in gels depending on stabiliser used, with the lowest values from those with alginate when stored for 28 days at 4°C. This knowledge can be used to facilitate the selection of the most appropriate plant polysaccharide-based delivery system for specific applications.

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The aim of this study was to evaluate rice polish as a substrate for the production of metabolites characterised by antifungal activity by using lactic acid bacteria. The Lactobacillus plantarum, L. brevis, L. paracasei, L. uvarum, L. farraginis, Pediococcus pentosaceus and P. acidilactici strains were tested in the experiment. The antifungal activity of the strains was evaluated against filamentous fungi, such as Aspergillus versicolor, A. terreus, A. niger, A. fumigatus and Penicillium spinulosum, P. viridicatum, P. palitans. The rice polish fermentation was carried out in a single step without growth supplementation at submerged fermentation conditions. The obtained results confirmed that rice polish is a suitable substrate for the production of antifungal metabolites depending on lactic acid bacteria (LAB) strain. The tested P. pentosaceus strains showed strong and moderate inhibitory activity against P. viridicatum, A. versicolor fungi, while P. acidilactici strains showed moderate and low activity against Aspergillus sp. fungi. None of the tested LAB exhibited antifungal activity against A. terreus and A. niger.