Working paper 1 of the Dialogue on Water, Food and Environment, 2001. The complete article is available on the CD-ROM version of this Annual Report or at www.iwmi.org/dialogue

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.

The effect of glass transition on nonenzymatic browning (NEB) rates of amorphous, L-lysine, and D-xylose containing maltodextrin (MD)- or polyvinylpyrrolidone (PVP)-based food models, equilibrated into a(w) of 0.23, 0.33, or 0.44 was studied. Glass transition temperature, T(g), was measured using DSC and NEB rates, followed spectrophotometrically. Use of citrate buffer as a pH regulator was evaluated. The NEB rates were higher in PVP than in MD models. Arrhenius plots showed nonlinearity in the vicinity of the T(g). Increasing a(w) decreased T(g), but did not affect NEB rates around the T(g). The temperature difference (T - T(g)) was not a sufficient measure of material stability.

The world’s farmers will likely need to produce enough food to feed 8 billion people by 2025, and to do so they must have enough water to raise their crops. Yet farmers are already competing with industry, domestic water users, and the environment for access to the world’s finite supply of water. Will available freshwater meet the rapidly growing demands for household, industrial, and environmental needs and still provide enough water to produce food for a burgeoning population? New research from IFPRI shows what steps policymakers and water users can take now to help ensure that water scarcity will not result in worsening hunger for the world’s poorest people. | Non-PR | IFPRI2; Public Policy and Investment; 2020 | DGO