The transport of water in four EVOH copolymers commonly used in high barrier food packages was characterized through permeation (continuous flow) and gravimetric experiments at different rela tive humidities and 23 ± 2°C. Water sorption isotherms were fitted with the D'Arcy and Watts' equa tion. From these data, the value of the solubility coefficient (S, as defined by Henry's law) was deter mined and was found constant within a 0.2-0.75 water activity (a w) range. Water uptake at the same a w increased as the EVOH ethylene content decreased. The permeability coefficient (P) for water through EVOH was determined as a function of water activity. The permeability was constant within the range of 0.3-0.75 a w and decreased with EVOH ethylene content. At high relative humidities (a w > 0.75) the value of permeability increased by up to two orders of magnitude. In this range, the higher the ethylene content the lesser the value of P.

Natural resources including water, energy, and food have an increase in demand due to the global population increases. The sustainable management of these resources is an urgent global issue. These resources combined in a very vital nexus are called the water–energy–food (WEF) nexus. The field of nanotechnology offers promising solutions to overcome several problems in the WEF nexus. This review is the first report that focuses on the suggested applications of nanofibers in the WEF sectors. An economic value of nanofibers in WEF sectors was confirmed, which was mainly successfully applied for producing clean water, sustainable energy, and safe food. Biotechnological solutions of nanofibers include various activities in water, energy, and food industries. These activities may include the production of fresh water and wastewater treatment, producing, converting, and storing energy, and different activities in the food sector. Furthermore, microbial applications of nanofibers in the biomedicine sector, and the most important biotechnological approaches, mainly plant tissue culture, are the specific focus of the current study. Applying nanofibers in the field of plant tissue culture is a promising approach because these nanofibers can prevent any microbial contamination under in vitro conditions, but the loss of media by evaporation is the main challenge in this application. The main challenges of nanofiber production and application depend on the type of nanofibers and their application. Different sectors are related to almost all activities in our life; however, enormous open questions still need to be answered, especially the green approach that can be used to solve the accumulative problems in those sectors. The need for research on integrated systems is also urgent in the nexus of WEF under the umbrella of environmental sustainability, global climate change, and the concept of one’s health.

For the first time, alginate polymer has been applied to prevent dyes from leaching out of colorimetric oxygen indicator films, which enable people to notice the presence of oxygen in the package in an economic and simple manner. The dye-based oxygen indicator film suffers from dye leaching upon contact with water. In this work, UV-activated visual oxygen indicator films were fabricated using thionine, glycerol, P25 TiO2, and zein as a redox dye, a sacrificial electron donor, UV-absorbing semiconducting photocatalyst, and an encapsulation polymer, respectively. When this zein-coated film was immersed in water for 24h, the dye leakage was as high as 80.80±0.45%. However, introduction of alginate (1.25%) as the coating polymer considerably diminished the dye leaching to only 5.80±0.06%. This is because the ion-binding ability of alginate could prevent the cation dye from leaching into water. This novel water-resistant UV-activated oxygen indicator was also successfully photo-bleached and regained colour fast in the presence of oxygen.

In the present paper, a mathematical model able to predict the water barrier properties of cellophane film as a function of the water activity at the upstream and downstream side of the film is presented. To validate the model water sorption, and permeation tests were performed at 30°C and at several water vapor activities. Despite the approximations involved in deriving the model, its ability to predict the water permeability of the investigated film is quite satisfactory. The proposed model was then applied to hypothetical measuring conditions in which the water activity at one side of the film was set equal to zero (like in a permeation test) or equal to 0.6 (like in the real working conditions), while the water activity of the other side changes between 0 and 0.6. A substantial difference has been observed between the two examined cases, showing the need for a more accurate analysis of the transport phenomena in the case of water sensitive packaging films like cellophane.

Zein, corn prolamine, was dissolved in several organic solvents to make films and their properties were examined. Ethanol with 20% water and acetone with 30% water were found to dissolve zein well and transform it into a transparent flexible film after moderate drying. Both films showed similar breaking strength to that of commercial thin film of polyvinylidene chloride for food use and were digested with proteases. Only the film prepared from acetone solution showed a relatively low water permeability. This water permeation was found to depend strongly on the rate of diffusion. 1,2-Epoxy-3-chloropropane (ECP) was added into the acetone solution to cross-link the zein molecules for the purpose of improving the breaking strength and water-resistant properties of the film. Alpha-chymotrypsin was found to digest the film even after the modification with ECP. However, this cross-linking resulted in little improvement in the water-resistant properties of the film and also reduced its flexibility.

This paper presents a mathematical model able to predict the water barrier properties of nylon film as a function of the water activity at the upstream and downstream side of the film. To validate the model, water sorption and permeation tests were conducted at 25 °C. The fitting and predictive ability of the proposed model was successfully tested by fitting the model to the sorption data and by predicting the nylon water permeability coefficient, respectively. The implications of the adopted approach on practical aspects of packaging were pointed out by comparing the nylon water barrier properties as evaluated by means of a permeation test and that in the real working conditions.

In China, waste sorting practice is not strictly followed, plastics, especially food packaging, are commonly mixed in food waste. Supercritical water gasification (SCWG) of unsorted food waste was conducted in this study, using model unsorted food waste by mixture of pure food waste and plastic. Different operating parameters including reaction temperature, residence time, and feedstock concentration were investigated. Moreover, the effect of three representative food additives namely NaCl, NaHCO₃ and Na₂CO₃ were tested in this work. Finally, comparative analysis about SCWG of unsorted food waste, pure food waste, and plastic was studied. It was found that higher reaction temperature, longer residence time and lower feedstock concentration were advantageous for SCWG of unsorted food waste. Within the range of operating parameters in this study, when the feedstock concentration was 5 wt%, the highest H₂ yield (7.69 mol/kg), H₂ selectivity (82.11%), total gas yield (17.05 mol/kg), and efficiencies of SCWG (cold gas efficiency, gasification efficiency, carbon gasification efficiency, and hydrogen gasification efficiency) were obtained at 480 °C for 75 min. Also, the addition of food additives with Na⁺ promoted the SCWG of unsorted food waste. The Na₂CO₃ showed the best catalytic performance on enhancement of H₂ and syngas production. This research demonstrated the positive effect of waste sorting on the SCWG of food waste, and provided novel results and information that help to overcome the problems in the process of food waste treatment and accelerate the industrial application of SCWG technology in the future.

In food packaging systems, moisture content influences chemical and physical film properties, also determining processes such as food spoilage, and properties of food texture and crispiness level. The study of water permeation and sorption processes of new materials intended to be used as packaging is very important to determine the best application conditions and to predict the film behavior under different moisture conditions inside and/or outside the packaging. In order to determine the suitable temperature and water activity (aw) application conditions for whey protein isolate (WPI)/polyvinyl alcohol (PVOH) blends as food flexible packaging, water permeation and water sorption thermodynamic behavior of these materials were evaluated. WPI/PVOH films and blends had solubility preponderant over the diffusion on the water permeation process. Water sorption experimental data were well described by the GAB model, and curves showed a more expressive increase of water sorption at aw > 0.75, with lower equilibrium moistures (Ye) at room than at chilled temperatures. Differential enthalpy decreased and differential entropy increased by the Ye gain, and the occurrence of enthalpy-entropy compensation was confirmed with enthalpy driving the sorption process. The addition of PVOH to the WPI matrix made the water sorption process more spontaneous. Water sorption thermodynamic analysis indicates that the application of WPI/PVOH blends as packaging is best suitable for foods and external environments with aw below 0.75 and at room temperature.

One of the most common materials used for packaging is low density polyethylene film. To improve the water vapour transfer of the film, zeolite¡polymer composite films and perforated films are produced. The solid-low density polyethylene composite films were prepared by extrusion of polyethylene beads coated with hot zeolite particles of a definite size range in an industrial extruder (-420/+212, -212/+106, -106/+53 microparticles/g of polyethylene beads). A needle (0.2, 0.5 and 1.75 mm in diameter) attached to the tip of a soldering gun was used for the production of the perforated polyethylene films (1, 3, 6, 12, 18 and 24 holes per 38.5 cm2). The overall evaluation indicates that the water vapour transfer rates can be modified by the composite and the perforated films, which provides packaging material variety for foods of different moisture content. The solid- polyethylene composite films showed less permeability to water vapour than the polyethylene film. This may be attributed to two reasons: the available polyethylene area is reduced by the presence of solid particles and these solid particles have an important sorption property. The water vapour transfer rates increased by the perforated films.

Zein electrospun nanofibers have poor water resistance, which restricts its applications in food preservation. To improve the water resistance of nanofibers, zein/ethyl cellulose (EC) hybrid nanofibers were prepared at different ratios. Besides, we also encapsulated cinnamon essential oil (CEO) into electrospun fibers for Agaricus bisporus preservation. As the weight ratio of EC increased from 0% (ZE-10) to 100% (ZE-01), the viscosity of electrospinning solutions gradually increased from 80.33 ± 19.23 mPa·s to 756.78 ± 22.48 mPa·s, resulting in sufficient chain entanglement for the preparation of uniform fibers. The average diameters of ZE-01, ZE-12, ZE-11, ZE-21, and ZE-10 nanofibers were 326 ± 53 nm, 267 ± 31 nm, 237 ± 51 nm, 292 ± 45 nm, and 362 ± 70 nm, respectively. The hydrogen bonds between the hydroxyl groups of ethyl cellulose and the amino groups of zein decreased the amount of free hydrophilic group, thus improving water resistance of nanofibers. Food packaging potential was evaluated using Agaricus bisporus. The zein/EC nanofibers loaded CEO significantly decreased weight loss and maintained the firmness of the Agaricus bisporus, and improved the quality of the Agaricus bisporus during storage.