One of the oldest methods of food preservation is the reduction of water content in foods. Sun and fire drying, salting of animal flesh, and sugaring of fruit in prehistoric times simulated natural drying processes such as fruit drying on trees. Foods with a high water content, such as milk, meat, fruits, and vegetables, undergo rapid microbial deterioration. The concept of water activity (a-w) gives information about the availability to microbial growth and the stability of food. It is expressed in terms of vapor pressure generated by an aqueous system relative to that of pure water at the same temperature. Growth and survival of food spoilage organisms (bacteria, yeasts and molds) are a function of water activity and other environmental factors including temperature, pH, oxygen, and carbon dioxide concentration, and the presence of preservatives.

Water is an essential component of food structures and biological materials. The importance of water as a parameter affecting virion stability and inactivation has been recognized across disciplinary areas. The large number of virus species, differences in spreading, likelihood of foodborne infections, unknown infective doses, and difficulties of infective virus quantification are often limiting experimental approaches to establish accurate data required for detailed understanding of virions’ stability and inactivation kinetics in various foods. Furthermore, non-foodborne viruses, as shown by the SARS-CoV-2 (Covid-19) pandemic, may spread within the food chain. Traditional food engineering benefits from kinetic data on effects of relative humidity (RH) and temperature on virion inactivation. The stability of enteric viruses, human norovirus (HuNoV), and hepatitis A (HAV) virions in food materials and their resistance against inactivation in traditional food processing and preservation is well recognized. It appears that temperature-dependence of virus inactivation is less affected by virus strains than differences in temperature and RH sensitivity of individual virus species. Pathogenic viruses are stable at low temperatures typical of food storage conditions. A significant change in activation energy above typical protein denaturation temperatures suggests a rapid inactivation of virions. Furthermore, virus inactivation mechanisms seem to vary according to temperature. Although little is known on the effects of water on virions’ resistance during food processing and storage, dehydration, low RH conditions, and freezing stabilize virions. Enveloped virions tend to have a high stability at low RH, but low temperature and high RH may also stabilize such virions on metal and other surfaces for several days. Food engineering has contributed to significant developments in stabilization of nutrients, flavors, and sensitive components in food materials which provides a knowledge base for development of technologies to inactivate virions in foods and environment. Novel food processing, particularly high pressure processing (HPP) and cold plasma technologies, seem to provide efficient means for virion inactivation and food quality retention prior to packaging or food preservation by traditional technologies.

Electrolyzed water (EW) is gaining popularity as a sanitizer in the food industries of many countries. By electrolysis, a dilute sodium chloride solution dissociates into acidic electrolyzed water (AEW), which has a pH of 2 to 3, an oxidationreduction potential of >1,100 mV, and an active chlorine content of 10 to 90 ppm, and basic electrolyzed water (BEW), which has a pH of 10 to 13 and an oxidation-reduction potential of -800 to -900 mV. Vegetative cells of various bacteria in suspension were generally reduced by >6.0 log CFU/ml when AEW was used. However, AEW is a less effective bactericide on utensils, surfaces, and food products because of factors such as surface type and the presence of organic matter. Reductions of bacteria on surfaces and utensils or vegetables and fruits mainly ranged from about 2.0 to 6.0 or 1.0 to 3.5 orders of magnitude, respectively. Higher reductions were obtained for tomatoes. For chicken carcasses, pork, and fish, reductions ranged from about 0.8 to 3.0, 1.0 to 1.8, and 0.4 to 2.8 orders of magnitude, respectively. Considerable reductions were achieved with AEW on eggs. On some food commodities, treatment with BEW followed by AEW produced higher reductions than did treatment with AEW only. EW technology deserves consideration when discussing industrial sanitization of equipment and decontamination of food products. Nevertheless, decontamination treatments for food products always should be considered part of an integral food safety system. Such treatments cannot replace strict adherence to good manufacturing and hygiene practices.

Worldwide, millions of tons of crustaceans are produced every year and consumed as protein-rich seafood. However, the shells of the crustaceans and other non-edible parts constituting about half of the body mass are usually discarded as waste. These discarded crustacean shells are a prominent source of polysaccharide (chitin) and protein. Chitosan is a de-acetylated form of chitin obtained from the crustacean waste that has attracted attention for applications in food, biomedical, and paint industries due to its characteristic properties, like solubility in weak acids, film-forming ability, pH-sensitivity, biodegradability, and biocompatibility. We present an overview of the application of chitosan in composite coatings for applications in food, paint, and water treatment. In the context of food industries, the main focus is on fabrication and application of chitosan-based composite films and coatings for prolonging the post-harvest life of fruits and vegetables, whereas anti-corrosion and self-healing properties are the main properties considered for antifouling applications in paints in this review.

To study the factors and mechanisms involved in microorganisms' death or resistance to temperature in low-water-activity environments, a previous work dealt with the viability of dried microorganisms immobilized in thin-layer on glass beads. This work is intended to check the efficiency of a rapid heating-cooling treatment to destroy microorganisms that were dried after mixing with wheat flour or skim milk. The thermoresistance of the yeast Saccharomyces cerevisiae and the bacterium Lactobacillus plantarum were studied. Heat stress was applied at two temperatures (150 or 200 degrees C) for treatments of one of four durations (5, 10, 20, or 30 s) and at seven levels of initial water activity (a(w)) in the range 0.10 to 0.70. This new treatment achieved a microbial destruction of eight log reductions. A specific initial water activity was defined for each strain at which it was most resistant to heat treatments. On wheat flour, this initial a(w) value was in the range 0.30-0.50, with maximal viability value at a(w)=0.35 for L. plantarum, whatever the temperature studied, and 0.40 for S. cerevisiae. For skim milk, a variation in microbial viability was observed, with optimal resistance in the range 0.30-0.50 for S. cerevisiae and 0.20-0.50 for L. plantarum, with minimal destruction at a(w)=0.30 whatever the heating temperature is.

This review examines recent published suggestions that "water dynamics" may be applied instead of water activity (aw) determination to predict microbial stability of concentrated and intermediate moisture food systems. Factors such as the relative effectiveness of additives for antimicrobial stabilization through aw-lowering (i.e. glucose vs fructose, glycerol vs propylene glycol) and the importance of glass transition temperature as an indicator of microbial stability were examined, based on available experimental data. Determination of the glass-rubber transition characteristics and/or the use of the "water-dynamics" map does not enable prediction of the microbial stability of foods (i.e. inhibition of growth) with confidence. These were no more effective alternatives than the concept of water activity as a basis for predicting microbial growth in foods.

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.

Analytical grade (AG) and industrial grade (IG) of three-food grade antioxidants butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and propyl paraben (PP) were analyzed to prove their fungitoxic effect on Aspergillus section Flavi strains. The effect of interactions among 10 antioxidant treatments at water activity levels (0.982, 0.955, 0.937 aW) for 11 and 35 days of incubation and at 25 °C in peanut grains on mycelial growth (CFU g(-1)) and aflatoxin B(1) (AFB(1)) accumulation were evaluated. Both antioxidant grade treatments had a significant effect (P < 0.001) on fungal count. All antioxidant treatments showed the highest effectiveness on control of growth of peanut aflatoxigenic strains at 0.937 aW and at 11 days of incubation. Overall, AG and IG binary mixtures M3 (20 + 10 mM), M4 (20 + 20 mM) and ternary mixtures M5 (10 + 10 +10 mM), M6 (10 + 20 + 10 mM), M7 (20 + 10 + 10 mM) and M8 (20 + 20 + 10 mM) were the treatments most effective at inhibiting growth of Aspergillus section Flavi strains. Industrial grade BHA 10 and 20 mM, binary mixtures M1 (10 + 10 mM), M2 (10 + 20 mM), M3 (20 + 10 mM), M4 (20 + 20 mM) and ternary mixtures M5 (10 + 10 + 10 mM), M6 (10 + 20 + 10 mM), M7 (20 + 10 + 10 mM) and M8 (20 + 20 + 10 mM) completely inhibited AFB1 production. The studied results suggest that IG antioxidant mixtures have potential for controlling growth of these mycotoxigenic species and prevent aflatoxin accumulation at the peanut storage system.

Few data are available on the thermophysical properties of high porosity foodstuff in the freezing domain. This paper presents some data obtained with a cellulose sponge used as a model food. The fraction of unfreezable water was obtained from differential scanning calorimetry data, using two different methods with a very good agreement. Water activity was experimentally determined at positive temperature. Experimental data were modeled by the Guggenheim-Anderson-de Boer (GAB) model, and a model deduced from the Clausius-Clapeyron equation. The GAB model was used to extrapolate these data in the subzero domain. It showed a good agreement until a water activity of 0.9, whereas the second model is usable only up to the value of 0.75.