Evaluation of functional and nutritional potential of a protein concentrate from Pleurotus ostreatus mushroom.

Edible mushrooms used as a protein-rich food may be an attractive alternative to conventional protein sources, while promoting its valorization. This work aimed to obtain a protein concentrate from a Pleurotus ostreatus mushroom flour, its characterization, and nutritional and functional properties evaluation. Methodologies applied for extraction and precipitation of protein were optimized - pH 4 and 12, respectively; and flour-solvent ratio of 1:20 w/v. The protein density was increased by 78%. P. ostreatus flour and concentrate were characterized by proximal composition. The content of total phenolic compounds in the protein concentrate decreased, leading to a positive effect on protein digestibility, while the DPPH radical scavenging activity was not significantly affected. Peptides with molecular weights from 12 to 35 kDa, with possible bioactivity, were identified by electrophoresis. Protein digestibility assessed by in vitro gastrointestinal digestion showed a 4.2-fold higher hydrolysis degree in the protein concentrate than the flour.

ß-lactoglobulin micro- and nanostructures as bioactive compounds vehicle: In vitro studies.

ß-Lactoglobulin (ß-Lg) is known to be capable to bind hydrophilic and hydrophobic bioactive compounds. This research aimed to assess the in vitro performance of ß-Lg micro- (diameter ranging from 200 to 300 nm) and nano (diameter < 100 nm) structures associated to hydrophilic and hydrophobic model compounds on Caco-2 cells and under simulated gastrointestinal (GI) conditions. Riboflavin and quercetin were studied as hydrophilic and hydrophobic model compounds, respectively. Cytotoxicity experiment was conducted using in vitro cellular model based on human colon carcinoma Caco-2 cells. Moreover, the digestion process was simulated using the harmonized INFOGEST in vitro digestion model, where samples were taken at each phase of digestion process - oral, gastric and intestinal - and characterized in terms of particle size, polydispersity index (PDI), surface charge by dynamic light scattering (DLS); protein hydrolysis degree by 2,4,6-trinitrobenzene sulfonic acid (TNBSA) assay and native polyacrylamide gel electrophoresis; and bioactive compound concentration. Caco-2 cell viability was not affected up to 21 × 10-3 mg mL-1 of riboflavin and 16 × 10-3 mg mL-1 quercetin on ß-Lg micro- and nanostructures. In the oral phase, ß-Lg structures' particle size, PDI and surface charge values were not changed comparing to the initial ß-Lg structures (i.e., before being subjected to in vitro GI digestion). During gastric digestion, ß-Lg structures were resistant to proteolytic enzymes and to acid environment of the stomach - confirmed by TNBSA and native gel electrophoresis. In vitro digestion results indicated that ß-Lg micro- and nanostructures protected both hydrophilic and hydrophobic compounds from gastric conditions and deliver them to target site (i.e., intestinal phase). In addition, ß-Lg structures were capable to enhance riboflavin and quercetin bioaccessibility and bioavailability potential compared to bioactive compounds in their free form. This study indicated that ß-Lg micro- and nanostructures were capable to enhance hydrophilic and hydrophobic compounds bioavailability potential and they can be used as oral delivery systems.

Physicochemical characterisation and release behaviour of curcumin-loaded lactoferrin nanohydrogels into food simulants.

Whey protein nanostructures can be used as vehicles for the incorporation of nutraceuticals (e.g., antioxidants or vitamins) aimed at the development of functional foods, because nanostructures provide greater protection, stability and controlled release to such nutraceuticals. Fundamental knowledge is required regarding the behaviour of nanostructures when associated with nutraceuticals and their interactions with real food matrices. In this study, a lactoferrin (LF) nanohydrogel was developed to encapsulate curcumin (nutraceutical model) and its behaviour was evaluated in terms of the LF structure and the interaction with curcumin. The release kinetics of curcumin from LF nanohydrogels was also assessed using food simulants with a hydrophilic nature (10% ethanol) and lipophilic nature (50% ethanol). This system was able to encapsulate curcumin at 80 µg mL-1 with an efficiency of ca. 90% and loading capacity of ca. 3%. Through spectroscopic characterisation, it is suggested that LF and curcumin bind via hydrophobic interactions and the average binding distance between LF and curcumin was found to be 1.91 nm. Under refrigerated conditions (4 °C), this system showed stability for up to 35 days, while at room temperature (25 °C) it was shown to be stable for up to 14 days of storage. The LF nanohydrogel presented higher release rates of curcumin in a lipophilic food simulant (stable after ca. 7 h) as compared to a hydrophilic simulant (stable after ca. 4 h). LF nanohydrogels were successfully incorporated into a gelatine matrix and showed no degradation in this process. The behaviour of this system and the curcumin release kinetics in food stimulants make the LF nanohydrogel an interesting system to associate with lipophilic nutraceuticals and to incorporate in refrigerated food products of a hydrophilic nature.