Effect of Natural Nanostructured Rods and Platelets on Mechanical and Water Resistance Properties of Alginate-Based Nanocomposites

Development and Characterization of Films with Propolis to Inhibit Mold Contamination in the Dairy Industry

Due to the number of polyphenols with multiple biological activities, propolis has high potential to be used as an active agent in food protective films. Therefore, this study aimed to develop and characterize a sodium alginate film with ethanolic extract of propolis (EEP) for its potential use as protective active packaging against filamentous fungi in ripened cheese. Three different concentrations of EEP were analyzed: 0, 5 and 10% w/v. The films obtained were characterized, assessing thermal and physicochemical properties, as well as the concentration of polyphenols in the EEP and antifungal activity of the active films. The incorporation of EEP in the films generated thermal stability with respect to the loss of mass. Total color values (ΔE) of the films were affected by the incorporation of the different concentrations of EEP, showing a decrease in luminosity (L*) of the films, while the chromatic parameters a* and b* increased in direct proportion to the EEP concentration. Antifungal activity was observed with a fungistatic mode of action, stopping the growth of the fungus in cheeses without development of filamentous molds, thus increasing the shelf life of the ripened cheese under the analytical conditions, over 30 days at room temperature. Overall, EEP can be used to prevent growth and proliferation of spoilage microorganisms in cheese.

Review of Thin Film Nanocomposite Membranes and Their Applications in Desalination

All over the world, almost one billion people live in regions where water is scarce. It is also estimated that by 2035, almost 3.5 billion people will be experiencing water scarcity. Hence, there is a need for water based technologies. In separation processes, membrane based technologies have been a popular choice due to its advantages over other techniques. In recent decades, sustained research in the field of membrane technology has seen a remarkable surge in the development of membrane technology, particularly because of reduction of energy footprints and cost. One such development is the inclusion of nanoparticles in thin film composite membranes, commonly referred to as Thin Film Nanocomposite Membranes (TFN). This review covers the development, characteristics, advantages, and applications of TFN technology since its introduction in 2007 by Hoek. After a brief overview on the existing membrane technology, this review discusses TFN membranes. This discussion includes TFN membrane synthesis, characterization, and enhanced properties due to the incorporation of nanoparticles. An attempt is made to summarize the various nanoparticles used for preparing TFNs and the effects they have on membrane performance towards desalination. The improvement in membrane performance is generally observed in properties such as permeability, selectivity, chlorine stability, and antifouling. Subsequently, the application of TFNs in Reverse Osmosis (RO) alongside other desalination alternatives like Multiple Effect Flash evaporator and Multi-Stage Flash distillation is covered.

Significantly improve the water and chemicals resistance of alginate-based nanocomposite films by a simple in-situ surface coating approach

Biopolymers have shown great application prospects due to their advantages of being biodegradable, renewable, non-toxic, safe and inexpensive. However, the innate hydrophilicity of biopolymers means the materials prepared from them easily swell or disintegrate in aqueous media, limiting their applications. Herein, on the basis of improving the mechanical performance of a sodium alginate/poly(vinyl alcohol) (SA/PVA) film by introducing palygorskite (Pal) nanorods, the hydrophobicity of the obtained SA/PVA/Pal film was improved further by surface coating with methyltrichlorosilane (MTCS) through a vapor deposition-surface polycondensation reaction. MTCS nanofilaments, with a size of approximately 50 nm, were formed on the film surface by the silanization reaction between MTCS and hydroxyls, resulting in an improvement in surface hydrophobicity characterized by a contact angle (111.8°) higher than that of SA/PVA/Pal film (72.7°). Therefore, the obtained films maintained their original shape and strength after soaking for a long time in aqueous solutions containing acid, alkaline, and electrolyte, also in organics, while the uncoated film dissolved quickly and lost its original shape. Moreover, the surface coating also increased the film's tensile strength from 11.43 to 28.69 MPa. This demonstrates a simple, universal and effective way to improve the resistance of biopolymer-derived materials to water and various chemicals.