Antimicrobial Effect of Titanium Dioxide Nanoparticles

The widespread use of antibiotics has led to the emergence of multidrug-resistant bacterial strains, and therefore a current concern for food safety and human health. The interest for new antimicrobial substances has been focused toward metal oxide nanoparticles. Specifically, titanium dioxide (TiO2) has been considered as an attractive antimicrobial compound due to its photocatalytic nature and because it is a chemically stable, non-toxic, inexpensive, and Generally Recognized as Safe (GRAS) substance. Several studies have revealed this metal oxide demonstrates excellent antifungal and antibacterial properties against a broad range of both Gram-positive and Gram-negative bacteria. These properties were significantly improved by titanium dioxide nanoparticles (TiO2 NPs) synthesis. In this chapter, latest developments on routes of synthesis of TiO2 NPs and antimicrobial activity of these nanostructures are presented. Furthermore, TiO2 NPs favor the inactivation of microorganisms due to their strong oxidizing power by free radical generation, such as hydroxyl and superoxide anion radicals, showing reductions growth against several microorganisms, such as Escherichia coli and Staphylococcus aureus. Understanding the main mechanisms of antimicrobial action of these nanoparticles was the second main purpose of this chapter

Development of Biocomposites with Antioxidant Activity Based on Red Onion Extract and Acetate Cellulose

Antioxidant biocomposites have been successfully developed from cellulose acetate, eco-friendly triethyl citrate plasticizer and onion extract as a source of natural antioxidants. First, an onion extraction process was optimized to obtain the extract with highest antioxidant power. Extracts under absolute ethanol and ethanol 85% were the extracts with the highest antioxidant activity, which were the characterized through different methods, DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2ʹ-azinobis(3-ethylbenzothiazoline-6-sulphonate)), that measure radical scavenger activity, and polyphenolic and flavonoid content. Afterwards, the extract was incorporated in cellulose acetate as polymer matrix owing to develop an active material intended to oxidative sensitive food products packaging. Different concentrations of onion extract and plasticizer were statistically studied by using response surface methodology in order to analyze the influence of both factors on the release of active compounds and therefore the antioxidant activity of these materials

High hydrostatic pressure effect on chemical composition, color, phenolic acids and antioxidant capacity of Cape gooseberry pulp (Physalis peruviana L.)

The aim of this study was to evaluate the effects of high hydrostatic pressure (HHP) at 300, 400 and 500 MPa/1, 3 and 5 min on nutritional and antioxidant properties of Cape gooseberry pulp after immediate application and after 60 days of storage. Proximal analysis, color, phenolic acids content and antioxidant capacity were determined. When analyzing the immediate effect of different treatments, a clear influence of HHP was observed in all the components of the proximal analysis. Regarding color, none of the three chromatic parameters showed significant differences with control leading to a minimum ΔE at 300 MPa/3 min. Changes in bound and free phenolic acids were evidenced after treatments. The maximum levels of TPC as well as antioxidant capacity were observed at 500 MPa/5 min. By the end of storage, all treated samples discolored leading to ΔE = 14.9 at 500 MPa/5 min. The profile of free and bound phenolic acids presented differences compared to Day 0. The antioxidant capacity by means of ORAC increased for treatments above 300 MPa/5 min indicating the effectiveness of these treatments for the production of functional products based on gooseberry pulp. For treatments above 400 MPa/3 min, molds and yeasts were not detected.Fil: Vega Gálvez, Antonio. Universidad de la Serena; ChileFil: López, Jessica. Universidad de la Serena; Chile. Universidad de Santiago de Chile; ChileFil: Torres Osandón, Maria José. Universidad de la Serena; ChileFil: Galotto, Maria José. Universidad de Santiago de Chile; ChileFil: Puente Díaz, Luis. Universidad de la Serena; ChileFil: Quispe Fuentes, Issis. Universidad de la Serena; ChileFil: Di Scala, Karina Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; Argentin