Production of Polyhydroxyalkanoates for Biodegradable Food Packaging Applications Using Haloferax mediterranei and Agrifood Wastes.

Polyhydroxyalkanoates (PHAs) are high-value biodegradable polyesters with thermoplastic properties used in the manufacturing of different products such as packaging films. PHAs have gained much attention from researchers and industry because of their biobased nature and appropriate features, similar to conventional synthetic plastics. This review aims to discuss some of the recent solutions to challenges associated with PHA production. The implementation of a cost-effective process is presented by following different strategies, such as the use of inexpensive carbon sources, the selection of high-producing microorganisms, and the functionalization of the final materials to make them suitable for food packaging applications, among others. Research efforts are needed to improve the economic viability of PHA production at a large scale. Haloferax mediterranei is a promising producer of PHAs due to its ability to grow in non-sterile conditions and the possibility of using seawater to prepare the growth medium. Additionally, downstream processing for PHA extraction can be simplified by treating the H. mediterranei cells with pure water. Further research should focus on the optimization of the recycling conditions for the effluents and on the economic viability of the side streams reutilization and desalinization as an integrated part of PHA biotechnological production.

Biodegradable active materials containing phenolic acids for food packaging applications.

The development of new materials for food packaging applications is necessary to reduce the excessive use of disposable plastics and their environmental impact. Biodegradable polymers represent an alternative means of mitigating the problem. To add value to biodegradable materials and to enhance food preservation, the incorporation of active compounds into the polymer matrix is an affordable strategy. Phenolic acids are plant metabolites that can be found in multiple plant extracts and exhibit antioxidant and antimicrobial properties. Compared with other natural active compounds, such as essential oils, phenolic acids do not present a high sensorial impact while exhibiting similar minimal inhibitory concentrations against different bacteria. This study summarizes and discusses recent studies about the potential of both phenolic acids/plant extracts and biodegradable polymers as active food packaging materials, their properties, interactions, and the factors that could affect their antimicrobial efficiency. The molecular structure of phenolic acids greatly affects their potential antioxidant and antimicrobial capacity, as well as their specific interactions with polymer matrices and food substrates. These interactions, in turn, can lead to plasticizing or cross-linking effects. In the present study, the antioxidant and antimicrobial properties of different biodegradable films with phenolic acids have been described, as well as the main factors affecting the active properties of these films as useful materials for active packaging development. More studies applying these active materials in real foods are required.

Influence of starch oxidation on the functionality of starch-gelatin based active films.

Biodegradable active films were prepared by casting, using corn starch, with differing oxidation degree, bovine gelatin, glycerol, as a plasticizer, and ethyl lauroyl arginate (LAE) as antimicrobial compound. The films were characterized as to their microstructure, physical properties and water affinity. Starch oxidation with sodium periodate (SP) greatly improved polymer compatibility and crosslinking, especially at 1:1 glucose:SP molar ratio, which promoted the films' strength (40-92%) and barrier capacity (33 and 40% reduction in water vapour and oxygen permeability, respectively in LAE-free films), while Maillard reactions promoted the film browning. LAE, with amino and carbonyl groups, participated in the condensation reactions, interfering in the network crosslinking. All films with LAE showed bactericidal effect against Listeria innocua and Escherichia coli and LAE free films with oxidized starch inhibited the growth of both bacteria by 1-2 log CFU, due to the antimicrobial properties of Maillard compounds. Blend films with the most oxidized starch and gelatin containing LAE are promising materials for food packaging applications.

Effect of the incorporation of antimicrobial/antioxidant proteins on the properties of potato starch films.

Glycerol plasticized potato starch films containing bioactive proteins (lactoferrin (LF) and/or lysozyme (LZ), at 0.1 and 0.2 ratio with respect to starch) were obtained by casting method and characterized as to their microstructural, thermal and physical (water content, mechanical, water and oxygen barrier, optical) properties. The bioactive properties, named antioxidant and antimicrobial, of the proteins and the films were also characterized. The incorporation of proteins affected the structural and physical properties of potato starch films, while modifying their thermal behavior and increasing the glass transition temperature. Both proteins showed a certain degree of compatibility with starch chains through the bond formations (increase in Tg), while a part is separated and migrates to the film surface. Their incorporation, especially that of lactoferrin, greatly increased the film's brittleness, regardless of the films water content, although they enhance the water vapor and oxygen barrier properties, whatever the age of the film. Protein also reduced the film's transparency and gloss, while lactoferrin induced color changes. The thermal degradation of blend films and isolated proteins occurred at temperatures of over 250°C, which means that blend starch films can be thermoprocessed, according to their thermoplastic properties and following the usual practices of the plastics industries. A synergistic antimicrobial action against Escherichia coli and coliforms was observed when both LZ and LF were simultaneously applied. Both of these exhibited antioxidant capacity.

Structure and oxidative stability of oil in water emulsions as affected by rutin and homogenization procedure.

The structural properties of oil-in-water (O/W) emulsions, as well as their oxidative stability upon storage at 50 °C, were studied. Eight different formulations were prepared, with the aim of studying the effect of three variables: the composition of the oil phase, the presence of the flavonoid rutin and the homogenization procedure on the structure and the oxidative stability. It was found that high pressure homogenization, through droplet size reduction, stabilized the emulsions both against creaming and oil oxidation. The interfacial protein was also partially replaced by rutin, further improving the stability of the emulsions, whereas purification of the oil phase had hardly any effect. Thus, the structural and oxidative stability of emulsions was controlled by the size of the droplets and improved by the addition of rutin.

Recent patents on the use of antioxidant agents in food.

The application of antioxidant ingredients is one of the most common ways to delay and prevent the detrimental effect of oxygen in foods. Some of the most widely used and studied antioxidants are carboxylic acids, tocopherols and thiol-containing compounds. However, consumer trends towards healthier and safer foods, together with the increasing concern for the potential toxicity of some antioxidants are leading research efforts towards the use of antioxidants obtained from natural sources, such as plant phenols, essential oils and chitosan. This paper reviews the latest published studies and issued patents on the use of antioxidants agents in foodstuffs. The properties of the most commonly used antioxidants as well as natural antioxidants are revised. Moreover, examples of recent patents on the application of antioxidants to different foodstuffs (meat, fish, vegetables, fruits and beverages) are given.