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The purpose of the present work is to present a review of literature on equations for fitting water sorption isotherms of foods and food products. Twenty-three equations, which have been proposed in the literature for correlating equilibrium moisture content in food systems, have been compiled and analysed. Their origin, range of applicability (both to type of food and water activity) and use are discussed. It is hoped that this critical compilation may be a useful guide for those researchers interested in the mathematical description of the water sorption isotherms of foods.

An empirically modified two-parameter multilayer adsorption equation is shown to take into account the effect of temperature on the water sorption isotherms of some food materials. Characteristic parameters of the sorption equation for each food tested are presented.The equation should be of value in predicting the shelf life behaviour of food products at different storage temperatures.

The present work examined some fundamental aspects of the relationship between water activity and % moisture in honey. For this purpose a theoretical analysis was made on water activity lowering in sugar solutions and honey; the correlation between water activity and % moisture in Argentine honeys was then experimentally determined and explained on the basis of the above analysis. A very good straight line relationship (correlation coefficient 0.971) was found between both parameters in the range examined (15-21% moisture), and also the goodness of fit of the regression equation was found to be quite satisfactory.Previous literature results were compared with the present ones.

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The use of sugar for the treatment of infected wounds was investigated in in vitro experiments with bacteria pathogenic to humans, such as Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Staphylococcus aureus. Studies showed that solutions of appropriate sugar concentration incubated at pH 7.0 and 35 degrees C were lethal to the bacterial species studied. On the basis of these results, it is proposed that an important function of sugar in the treatment of infected wounds is to create an environment of low water activity (aw), which inhibits or stresses bacterial growth.

Summary The objective of the present study is to evaluate the capacity of four published three‐parameter equations in describing water sorption isotherms of various types of foods. Thirty‐nine food isotherms obtained from literature and relating to fruits, meats, milk products, proteins, starchy foods and vegetables were used to evaluate the fitting abilities of the various equations. The equations studied were: B.E.T. modified – Brunauer (1945), Chen (1971), Young & Nelson (1967) and Hailwood & Horrobin (1946).

The thermal stability of enzyme invertase in reduced-moisture model systems of maltodextrin (MD), polyvynilpyrrolidone (PVP; MW 40,000) and trehalose heated at 90ЊC was studied. Significant invertase inactivation was observed in heated glassy PVP and MD systems kept well below their glass transition temperature (T g ), but the enzyme was fairly stable in rubbery trehalose systems. However, at moisture contents which allowed trehalose crystallization rapid thermal inactivation of invertase was observed. Invertase inactivation in heated PVP, MD and trehalose systems of reduced-moisture could not be predicted on the basis of glass transition and this was particularly true for trehalose. Conditions which would allow collapse of the systems and crystallization of trehalose were fairly well predicted based on the estimated T g of model systems.