Browsing by Author "Pintado, M.M."
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- Evaluation and insights into chitosan antimicrobial activity against anaerobic oral pathogensPublication . Costa, E.M.; Silva, S.; Pina, C.; Tavaria, F.K.; Pintado, M.M.The objective of this study was to assess the antimicrobial capability of non-chemically altered chitosan as an alternative to traditional antimicrobials used in the treatment of oral infections. The action mechanism of chitosan was also ascertained. High and low molecular weight chitosan showed antimicrobial activity at low concentrations for all tested bacteria with the MICs varying between 1 and 7 mg/ ml with a drop of efficacy relatively to the action of LMW chitosan. In addition chitosan showed also to be an effective bactericidal presenting bactericidal effect within 8 h at the latest. Additionally the evaluation of chitosan’s action mechanism showed that both MWs acted upon the bacterial cell wall and were not capable of interacting with the intracellular substances, as showed by the inefficacy obtained in the flocculation assay
- Impact of different thermal treatments and storage conditions on the stability of soybean byproduct (okara)Publication . Voss, G.B.; Rodríguez-Alcalá, L. M.; Valente, L.M.P.; Pintado, M.M.Okara is the byproduct obtained from tofu or soymilk production process. It has a rich nutritional composition, especially in fibers, proteins and lipids. Stabilization processes are required to assure its efficient and safe use, because there are few studies on okara. The main objective of this study was to evaluate the chemical composition (protein, fiber, lipids, ash and isoflavones), microbiological stability, antioxidant capacity and antinutritional factors in fresh okara stored at 4 and − 18 °C and dried okara (80 °C/5 h and 200 °C/1 h) stored at room temperature for 15 days. Okara showed a rich nutritional composition— ca. 35% of fiber, 30% of protein and 11% of lipids. The okara’s lipid profile showed high and valuable level of PUFA (ca. 56%) followed by MUFA (ca. 21%) and SFA (ca. 23%). The Fresh okara showed the highest antioxidant activity and total phenols, however for isoflavones (genistin, genistein, daidzin, daidzein) the dried okara at 200 °C exhibited higher content compared to dried okara at 80 °C and fresh okara. Okara samples submitted to thermal treatment showed a decrease in antinutritional factors in relation with fresh okara, whereas the treatment of dried okara at 200 °C was the most efficient inducing a decrease of ca. 6 times. In conclusion, the nutritional richness of this byproduct suggests okara as a valuable nutritional ingredient for further inclusion in food and feed, but considering the limited studies carried out to date, further studies are warranted to better stabilize okara.
- Synthesis optimization and structural characterization of chitosan-glucose derivative obtained by the Maillard reactionPublication . Montenegro, M. I.; Cardelle-Cobas, A.; Gullón, B.; Ruiz-Matute, A.; Corzo, N.; Pintado, M.M.Several strategies have been applied in order to expand the functional properties of chitosan and its applicability. One of the most successful is the introduction of hydrophilic residues in the chitosan molecule via formation of covalent bonds with the reactive amino groups that may provide it higher solubility (allowing application in more diverse food matrices) and more functional properties, namely prebiotic activity (allowing the development of new functional foods). The Maillard reaction is one of the most important used reactions. Several authors have carried out this kind of chitosan modification obtaining new derivatives with better functional properties. For that, the aim of this work was to optimize the synthesis of a chitosan (Chit)-glucose (Glc) derivative by the Maillard reaction as well as to carry out a complete structural characterization of the obtained derivative. Reaction conditions, evaluating the extent of the Maillard reaction, were optimized by varying temperature (40-80 °C), Glc concentration, and reaction time (0-72 h). Assessment of the reaction extent was carried out by measurements of absorbance and fluorescence. Structural characterization of the derivative was performed by different methodologies in order to determine the molecular weight (Mw) of the derivative, the degree of substitution (DS) and, to confirm the structure of the new derivative, a colloid titration method, High-Performance Liquid Chromatography-Size Exclusion Chromatography (HPLC-SEC), Fourier Transform Infrared Spectroscopy (FT-IR) and Proton Nuclear Magnetic Resonance (1H-NMR) were used. The results obtained, regarding the extent of the reaction, allowed to determine the optimal conditions being: 2% (w/v) of chitosan, 2% (w/v) of Glc, 60 °C and 32 h of reaction time. Structural characterization confirmed the successful introduction of the glucose into the chitosan molecule obtaining a Chit-Glc derivative with a Mw of 76 ±4.25 and a DS of 64.76 ±4.40 %.