Aquest article explica el paper de l’aigua en el comportament general de les plantes i, en concret, la seva rellevància en l’agricultura, amb l’objectiu que els lectors, no especialitzats en aspectes fisiològics, entenguin la importància del recurs de l’aigua en la producció d’aliments i béns. Per a fer-ho, s’analitzen els conceptes més rellevants que governen el funcionament de l’aigua a la planta i la relació amb els processos més lligats a la producció (fotosíntesi i creixement vegetatiu). Per a il·lustrar aquests conceptes es presenten alguns exemples agronòmics relacionats amb la sensibilitat estacional al dèficit hídric, l’eficiència en l’ús de l’aigua o la dependència de la producció d’aliments a la disponibilitat d’aigua.PARAULES CLAU: aigua, producció d’aliments, fisiologia vegetal, potencial hídric, fotosíntesi, transpiració, sensibilitat estacional al dèficit hídric. | This paper explains the role of water in the general behaviour of plants and more specifically its importance in agriculture, with the aim to let the reader who is not specialized in physiological aspects understand the function of water in the production of food and goods. To do this, the most significant concepts regulating the behaviour of water inside the plant have been analysed, together with the relationship of water with the processes most closely linked to production (photosynthesis and vegetative growth). Likewise, to illustrate these concepts, some agronomic examples are given in relation to seasonal sensitivity to water deficit, water use efficiency, and the dependence of food production on water availability.KEYWORDS: water, food production, plant physiology, water potential, photosynthesis, transpiration, seasonal sensitivity to water deficit. | Este artículo explica el papel del agua en el comportamiento general de las plantas y, en concreto, su relevancia en la agricultura, con el objetivo de que los lectores, no especializados en aspectos fisiológicos, puedan entender la importancia del recurso del agua en la producción de alimentos y bienes. Para ello, se han analizado los conceptos más destacados que gobiernan el funcionamiento del agua en la planta y su relación con los procesos más vinculados a la producción (fotosíntesis y crecimiento vegetativo). Para ilustrar estos conceptos se presentan algunos ejemplos agronómicos relacionados con la sensibilidad estacional al déficit hídrico, la eficiencia en el uso del agua o la dependencia de la producción de alimentos a la disponibilidad de agua.PALABRAS CLAVE: agua, producción de alimentos, fisiología vegetal, potencial hídrico, fotosíntesis, transpiración, sensibilidad estacional al déficit hídrico.

Microbiological Examination Methods of Food and Water (2nd edition) is an illustrated laboratory manual that provides an overview of current standard microbiological culture methods for the examination of food and water, adhered to by renowned international organizations, such as ISO, AOAC, APHA, FDA and FSIS/USDA. It includes methods for the enumeration of indicator microorganisms of general contamination, indicators of hygiene and sanitary conditions, sporeforming, spoilage fungi and pathogenic bacteria. Every chapter begins with a comprehensive, in-depth and updated bibliographic reference on the microorganism(s) dealt with in that particular section of the book. The latest facts on the taxonomic position of each group, genus or species are given, as well as clear guidelines on how to deal with changes in nomenclature on the internet. All chapters provide schematic comparisons between the methods presented, highlighting the main differences and similarities. This allows the user to choose the method that best meets his/her needs. Moreover, each chapter lists validated alternative quick methods, which, though not described in the book, may and can be used for the analysis of the microorganism(s) dealt with in that particular chapter. The didactic setup and the visualization of procedures in step-by-step schemes allow the user to quickly perceive and execute the procedure intended. Support material such as drawings, procedure schemes and laboratory sheets are available for downloading and customization. This compendium will serve as an up-to-date practical companion for laboratory professionals, technicians and research scientists, instructors, teachers and food and water analysts. Alimentary engineering, chemistry, biotechnology and biology (under)graduate students specializing in food sciences will also find the book beneficial. It is furthermore suited for use as a practical/laboratory manual for graduate courses in Food Engineering and Food Microbiology.

El presente trabajo se ha centrado en el desarrollo de emulsiones alimentarias aceite-en-agua estabilizadas con proteínas de atún. Específicamente, se ha analizado la influencia del método de conservación de las proteínas aisladas (liofilización, congelación) y de las condiciones de procesado seleccionadas sobre el comportamiento reológico y la microestructura de dichas emulsiones. Se han preparado emulsiones aceite en agua (con un contenido del 70% en peso de aceite) estabilizadas con proteínas de atún. La concentración de emulsionante usada ha sido 0,50% en peso. El comportamiento reológico de estas emulsiones no depende significativamente del método de conservación de la proteína empleado. Por otra parte, un aumento de la velocidad de agitación durante el proceso de manufactura de la emulsión da lugar a una disminución continua del tamaño medio de gota y a un aumento de las funciones viscoelásticas dinámicas, menos significativo a medida que aumenta dicha velocidad de agitación. | This work is focused on the development of o/w salad dressing-type emulsions stabilized by tuna proteins. The influence of protein conservation methods after the extraction process (freezing or liofilization) on the rheological properties and microstructure of these emulsions was analyzed. Processing variables during emulsification were also evaluated. Stable emulsions with adequate rheological and microstructural characteristics were prepared using 70% oil and 0.50% tuna proteins. From the experimental results obtained, we may conclude that emulsion rheological properties are not significantly affected by the protein conservation method selected. On the contrary, an increase in homogenization speed favours an increase in the values of the linear viscoelastic functions. Less significant is the fact that as agitation speed increases further, mean droplet size steadily decreases.

The transport of water in four EVOH copolymers commonly used in high barrier food packages was characterized through permeation (continuous flow) and gravimetric experiments at different rela tive humidities and 23 ± 2°C. Water sorption isotherms were fitted with the D'Arcy and Watts' equa tion. From these data, the value of the solubility coefficient (S, as defined by Henry's law) was deter mined and was found constant within a 0.2-0.75 water activity (a w) range. Water uptake at the same a w increased as the EVOH ethylene content decreased. The permeability coefficient (P) for water through EVOH was determined as a function of water activity. The permeability was constant within the range of 0.3-0.75 a w and decreased with EVOH ethylene content. At high relative humidities (a w > 0.75) the value of permeability increased by up to two orders of magnitude. In this range, the higher the ethylene content the lesser the value of P.

Food service directors and dietitians in many parts of the United States are having to cope with rationed water and use filtered water. Throughout the country, theEnvironmental Protection Agency reports that one third of our drinking water supply is contaminated. The water problem might well become more serious than the energy crisis. An in depth report on what has happened and what should be known about one of the nation's most urgent, but least accepted, problems is presented. Illustrative photographs and numerous tables accompany the report.

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.