Food aid is a critical component of the global food system, particularly when emergency situations arise. For the first time, we evaluate the water footprint of food aid. To do this, we draw on food aid data from theWorld Food Programme and virtual water content estimates from WaterStat. We find that the total water footprint of food aid was 10 km3 in 2005, which represents approximately 0.5% of the water footprint of food trade and 2.0% of the water footprint of land grabbing (i.e., water appropriation associated with large agricultural land deals). The United States is by far the largest food aid donor and contributes 82% of the water footprint of food aid. The countries that receive the most water embodied in aid are Ethiopia, Sudan, North Korea, Bangladesh and Afghanistan. Notably, we find that there is significant overlap between countries that receive food aid and those that have their land grabbed. Multivariate regression results indicate that donor water footprints are driven by political and environmental variables, whereas recipient water footprints are driven by land grabbing and food indicators.

Cities are complex and evolving systems with various factors playing key roles, e.g., population increase, the migration of population, the availability of resources, and the flexibility of policies. Consumers’ socioeconomic status is also an important aspect that needs to be studied in the context of a self-reliant urban city in its resource consumption. In this regard, the association between water–food and socio-economic attributes was analyzed based on the consumer-centric approach for the Hyderabad Metro Development Authority (HMDA) region, India. In this study, the embedded water content in food consumption was estimated and analyzed for nine food groups and twelve economic classes of the HMDA region. The middle economic classes were found to correspond to ~80% of embedded water content in the HMDA region, followed by the upper and lower economic classes. Except for cereals, per capita, the water consumption of all food groups increased with the spending power of the economic class. The green, blue, and grey consumption water footprints (WFs) suggested that much of the water that is being consumed in the HMDA region is precipitation-driven, followed by surface and groundwater resources. Limited water resources, water resource variability, climate change consequences including future climate projections, uncertainty in data, WF estimates, and region’s future growth imply a detailed study in drafting policies to become a self-reliant region.

As part of a survey conducted by the Central Agricultural Office of Hungary, 67 food samples including beverages were taken from 57 food industrial and catering companies, 75% of them being small and medium-sized enterprises (SMEs). Moreover, 40% of the SMEs were micro entities. Water used for food processing was simultaneously sampled. The arsenic (As) content of solid food stuff was determined by hydride generation atomic absorption spectrometry after dry ashing. Food stuff with high water content and water samples were analyzed by inductively coupled plasma mass spectrometry. The As concentration exceeded 10μg/L in 74% of the water samples taken from SMEs. The As concentrations of samples with high water content and water used were linearly correlated. Estimated As intake from combined exposure to drinking water and food of the population was on average 40% of the daily lower limit of WHO on the benchmark dose for a 0.5% increased incidence of lung cancer (BMDL0.5) for As. Five settlements had higher As intake than the BMDL0.5. Three of these settlements are situated in Csongrád county and the distance between them is less than 55km. The maximum As intake might be 3.8μg/kg body weight.

A new model of water sorption isotherm is developed on the basis of Raoult's law. It is assumed that water present in food occurs in two states, as free water with properties of the bulk water and as water of hydration. Hydrated molecules are considered as new entities with molecular weights larger than those of non-hydrated molecules. Hydration reduces the free concentration of water and thus affects water activity in solution. Application of the developed equation to food sorption data showed that it gives approximation of sorption isotherms much better than that offered by the GAB model. Moreover, it predicts infinite adsorption at a(w)=1, the property which is not offered by the GAB equation. The new equation makes it possible to interpolate isotherms at high water activities close to one. The probability that the new equation will fit the food isotherm with small RMS is higher than 90% and substantially exceeds that found for the GAB model. As a two-parameter model it makes substantial improvement over the three-parameter GAB equation.

A molecular dynamics (MD) modeling and simulations approach has been rationally built and developed to study porous food systems constructed with amylose and dextran chains. The findings from our MD studies indicate that the presence of food macromolecules decreases the energetics of the water–water interactions for the nearby water molecules in the pore space, but provides additional water–macromolecule interactions that can significantly outweigh the partial loss of water–water interactions to make the adjacent water molecules strongly bound to the food macromolecules so that the water activity and water removal rate are decreased as dehydration proceeds and, thus, the dehydration energy requirement would be increased. The effects of pore structures are greater in systems with higher densities of food macromolecules, smaller in size pores, and stronger water–macromolecule interactions. Dehydration of food materials can thus be reasonably expected to start from the largest pores and from the middle of the pores, and to have non-uniform water removal rates and non-planar water–vapor interfaces inside individual pores as well as across sections of the food materials. The food porous structures are found to have good pore connectivity for water molecules. As dehydration proceeds, water content and the support from water–water and water–macromolecule interactions both decrease, causing the food porous structures to adopt more compact conformations and their main body to decrease in size. Dehydration in general also reduces pore sizes and the number of pore openings, increases the water–macromolecule interactions, and leads to the reduction of the overall thermal conductivity of the system, so that more energy (heat), longer times, and/or greater temperature gradients are needed in order to further dehydrate the porous materials. Our thermodynamic analysis also shows that the average minimum entropy requirement for food dehydration is greater when the water–macromolecule interactions are stronger and the food macromolecular density is higher. The importance of the physicochemical affinity of food molecules for water and of the compatibility of the resultant porous structures with water configurational structures in determining food properties and food processing through the water–macromolecule interactions, is clearly and fundamentally verified by the results and discussion presented in this work.

The water activity, pH and other compositional parameters such as the moisture, fat and NaCl contents of various food emulsions were determined: butters, margarine (W/0) and mayonnaises (O/W). Water activity was determined by a gravimetric method (PEC procedure) and an instrumental method (dew-point hygrometer). The mean a(w) values obtained for the samples assayed were 0.904 +/- 0.050 (butters), 0.914 +/- 0.028 (margarines) and 0.947 +/- 0.013 (mayonnaises). The a(w) of the butter and margarine samples could be predicted with an error less than 0.02 units from the NaCl content of their aqueous phase (m) by using the following simple linear regression equation: a(w) = 0.954 - 0.036m. This equation could not be used to predict the a(w) of the mayonnaises, which, however, were obtained by using the Chen equation for mixtures of solutes.

This study has deduced a correlation between points of inflection of water activity and loss factor with respect to moisture content. A point of inflection in loss factor with respect to moisture content was found to coincide with the sorption isotherm point of inflection that defines the transition from multilayer to solution in every instance analysed, with an average difference of just 0.01 kg kg−1. Food can support microbial growth and chemical reactions in water activity levels above this critical transition. This correlation was discovered using published dielectric and sorption data for specific foods at similar temperatures. It was found that low sugar foods containing high levels of hydrocolloids generally exhibited different behaviour from fruits. This shows that microwave heating behaviour will be different in fruits compared to low sugar foods with high hydrocolloid content when drying to achieve a certain water activity and therefore shelf life.

China’s water resources are under increasing pressure from socioeconomic development, diet shifts, and climate change. Agriculture still concentrates most of the national water withdrawal. Moreover, a spatial mismatch in water and arable land availability—with abundant agricultural land and little water resources in the north—increases water scarcity and results in virtual water transfers from drier to wetter regions through agricultural trade. We use a general equilibrium welfare model and linear programming optimization to model interprovincial food trade in China. We combine these trade flows with province-level estimates of commodities’ virtual water content to build China’s domestic and foreign virtual water trade network. We observe large variations in agricultural water-use efficiency among provinces. In addition, some provinces particularly rely on irrigation vs. rainwater. We analyze the virtual water flow patterns and the corresponding water savings. We find that this interprovincial network is highly connected and the flow distribution is relatively homogeneous. A significant share of water flows is from international imports (20%), which are dominated by soy (93%). We find that China’s domestic food trade is efficient in terms of rainwater but inefficient regarding irrigation, meaning that dry, irrigation-intensive provinces tend to export to wetter, less irrigation-intensive ones. Importantly, when incorporating foreign imports, China’s soy trade switches from an inefficient system to a particularly efficient one for saving water resources (20 km ³/y irrigation water savings, 41 km ³/y total). Finally, we identify specific provinces (e.g., Inner Mongolia) and products (e.g., corn) that show high potential for irrigation productivity improvements.

Water vapour sorption isotherms describe the relationship between water content and water activity. Depending on the nature of food powder (crystalline or amorphous), the shape of isotherm is different. Mostly food powders have complex structures, including potentially crystallisable solutes such as sugars, which show changes in crystallinity during the adsorption of water. Even for such an apparently simple system as crystalline sugar, numerous factors affect the adsorption of water vapour and, as a consequence, the storage stability. The presence of a thin film of saturated solution at the surface of the crystal, grain size distribution and the inclusion of mother liquor droplets in the crystal are some of the factors which perturb the equilibrium relative humidity of sugar and its aptitude to caking. These conditions were carefully studied at the level of the laboratory and in a pilot silo. Conditions of "decaking" (recovering a flowing sugar after caking) were also established. In the case of noncrystalline powders, water activity, together with glass transition temperature, is important to determine if it is necessary to interpret the origin of the formation of bridges between food powder particles and the caking phenomenon.

A new paradigm for sustainable, integrated, water resources management is emerging from international conferences around the world. Its most succinct description is ‘the water–food–energy nexus for a green economy’. The water, food and energy nexus aims at the most efficient, best practice principles applied throughout the full food supply chain. This includes consideration of reducing wastage of the food for various reasons in the supply chain. This paper describes the global opportunities for better efficiency and resources conservation in the water, food, and energy supply chains with examples from Australia. Food wastage equates on average to 243 l day⁻¹ of water per person in the food they throw away, which is 1.5 times the daily water use per person in the UK. The concepts of virtual water and water footprint can help in identifying opportunities to save water by targeting reduction of wastage of food that has the highest virtual water content. A green economy aims at achieving optimised supply chain objectives in a manner that espouses the sustainability principle, gives due attention to environmental concerns and helps with eradication of poverty and hunger.