Apparent water diffusivity has been studied on an emulsified food model made of gelatin and hydrogenized vegetable fat. Lipid content was varied from 0 to 50% w/w and three particle mean diameters were generated (40, 110, and 400 mu m) in gelatin samples containing 75g of water per 100g of fat-free sample. In joined compartment experiments, fatty hydrated gels were dehydrated in contact with either a dry pure gelatin compartment or an industrial sponge cake. Water content profiles were used to determine the apparent water diffusivity value using Ruiz Cabrera et al.'s method,([1]) which takes gel shrinkage into account.

Two healthy men were evaluated before and after a 56 day raft voyage to determine endocrine and metabolic status immediately after and during the recovery phase after long term caloric, protein, and water deprivation. Daily intake during the trip consisted of no protein, 300 ml water, and for the first 40 days, 300 Kcal glucose. The subjects lost weight from 84.1 to 58.1 and 78.3 to 57.7 kg, respectively. Other variations were measured including rate of excretion, diurnal patterns, serum testosterone levels, plasma insulin levels, serum glucose concentrations, triglyceride content, liver function, fat and xylsoe absorption, and renal function.

The structured food systems (i.e. cellular tissues) are dissipative structures whose functionality mainly concerns their properties (physico-chemical properties, chemical and biochemical reactions), external interactions with surroundings (interactions with micro-organisms, heat and mass transport pathway) and especially, their interactions with consumers (nutritional value, quality, taste and flavour, texture, appearance: size, shape, colour). Dehydration or rehydration processes concern heat and mass transport phenomena (water, solutes) coupled with micro and macrostructure changes both producing important effects on food functionality. Control of these changes is the major concern in food product development. This control must be applied not only to the changes in physico-chemical properties but also to those related with consumers' issues. Food matrixengineering is a branch of food engineering which aims to apply the knowledge of the food matrixcomposition, structure and properties to promote and control adequate changes which can improve some sensorial and/or functional properties in the food. These changes, which are caused by some basic operations, are related to the phenomena of heat and mass transfer, vaporization-condensation, internal gas or liquid release, structure deformation-relaxation and phase transitions in matrixcomponents, and are usually coupled throughout the operation's progress. The final product may be a new product with improved composition and sensorial properties and/or more stability. All these concepts are discussed in this paper using several examples related to the application of combined food dehydration techniques.

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Six ponies were deprived of drinking water and food and compared over 24 hours with nondeprived ponies, ponies deprived of water but with food available, and ponies deprived of food but with water available. When food was eaten during water deprivation, plasma osmolality rose 4% from 284 mOsm/kg to 295 mOsm/kg. During water and food deprivation, plasma osmolality failed to rise, even over 24 hours, and usually fell. Packed cell volume was higher when food but not water was available. Food and/or water deprivation had no significant effect on plasma protein concentration. When food was available, the ponies drank three times more water (13.1 ± 2.1 kg) than when water but not food was available (3.5 ± 1.4 kg). Blood volume changes were calculated from packed cell volume and plasma protein data, and it was found that blood volume did not change significantly with deprivation. Urine volume did not vary with deprivation, but free water clearance changed significantly, falling when food but not water was available. Under these conditions, blood volume is maintained, but the mechanisms are not clear. When deprived of both drinking water and food, ponies failed to develop the hyperosmolality expected under these conditions. Water deprivation while food is available is a more powerful challenge to water and electrolyte homeostasis than deprivation of both food and water.

Mammals in drylands are facing not only increasing heat loads but also reduced water and food availability as a result of climate change. Insufficient water results in suppression of evaporative cooling and therefore increases in body core temperature on hot days, while lack of food reduces the capacity to maintain body core temperature on cold nights. Both food and water shortage will narrow the prescriptive zone, the ambient temperature range over which body core temperature is held relatively constant, which will lead to increased risk of physiological malfunction and death. Behavioural modifications, such as shifting activity between night and day or seeking thermally buffered microclimates, may allow individuals to remain within the prescriptive zone, but can incur costs, such as reduced foraging or increased competition or predation, with consequences for fitness. Body size will play a major role in predicting response patterns, but identifying all the factors that will contribute to how well dryland mammals facing water and food shortagewill copewith increasing heat loads requires a better understanding of the sensitivities and responses ofmammals exposed to the direct and indirect effects of climate change. | The South African National Research Foundation (NRF), the Carnegie Corporation of New York, the Claude Leon Foundation, the Global Change System for Analysis, Research and Training (START), the Oppenheimer Memorial Trust, the Tswalu Foundation, the University of the Witwatersrand, and the Australian Research Council. | http://jeb.biologists.org | am2022 | Anatomy and Physiology | Centre for Veterinary Wildlife Studies | Paraclinical Sciences