Applications water-activated

Pesticide) Alachlor Lombardia Region (Northern Surface water Italy) - Meteorological data - Application rate - Active ingredient lost by drift - Percentage of active ingredient lost by runoff [53]... 

Kapsalis, J.G. 1987. Influence of hysteresis and temperature on moisture sorption isotherms. In Water Activity Theory and Application to Foods (L.B. Rockland and L.R. Beuchat, eds), pp. 173-213. Dekker, New York. 

For most applications, the activity of water may be taken as unity. A better approximation for the activity of water is its mole fraction (7 ). 

Friedel, R.R., and Cundell, A.M., The application of water activity measurement to the microbiological attributes testing of nonsterile OTC drug products, Pharm. Forum, 25(2) 6087-6090 (1998). 

One of the limitations of this model is that the confinement of water molecules within clusters precludes its use within the context of water transport simulation because cluster-connective hydration structure is absent. Furthermore, water activity and contractile modulus are macroscopic based concepts whose application at the nanoscopic level is dubious. P is represented by a function borrowed from macroscopic elastic theory that contains E, and there is no microstructure-specific model for the resistance to deformation that can be applied to Nation so that one is forced to use experimental tensile moduli by default. 

U.S. Pharmacopeia (USP) (2007), Application of water activity determination to non-sterile pharmaceutical products, general chapter <1112>, U.S. Pharmacopeial Convention, Rockville, MD. 

When water molecules interact with an enzyme, it is natural that conformational changes can occur, which in turn can cause changes in the selectivity of the enzyme. Since enantioselectivity of enzymes is of major importance for many applications, it is a common task to investigate how to choose reaction conditions providing the maximal enantioselectivity. As might be expected, because water can interact with enzymes in many ways, it is difficult to generalize the effects. In some studies of lipase-catalyzed esterification reactions, no effects of water activity on enantioselectivity were observed [30]. In a similar study, no effects were observed in most cases, while the enantioselectivity of one lipase-catalyzed reaction decreased... 

Rockland, L.B. and Beuchat, L.R. (eds) (1987) Water Activity Theory and Applications to Food, Marcel Dekker, New York. 

Reserve batteries have been developed for applications that require a long inactive shelf period followed by intense discharge during which high energy and power, and sometimes operation at low ambient temperature, arc required. These batteries arc usually classified by the mechanism of activation which is employed. There are water-activated batteries that utilize fresh or seawater electrolyte-activated batteries, some using the... 

The importance of temperature control is significant for laboratory comparisons, accelerated shelf-life studies, and packaging requirements. Also, temperature may be essential when measuring aw levels near critical values, especially for government regulations or critical control points. The precision required in water activity applications will determine the need for temperature control. Several reasons for sample temperature control are ... 

In most skin applications stability of the enzymes is a key issue as they are autolytic. This can be achieved by copackaging and use of high concentrations of glycerol to reduce the water activity of the enzyme to stabilize it. On dilution with a moisturizer the enzyme becomes activated.49 More work is needed to stabilize enzymes in emulsions. 

Activated carbon is a finely divided form of amorphous carbon manufactured from the carbonization of an organic precursor, which possesses a microporous structure with a large internal surface area. The ability of the hydrophobic surface to adsorb small molecules accounts for the widespread applications of activated carbon as gas filters, decoloring agents in the sugar industry, water purification agents, and heterogeneous catalysts. 

Maltodextrin solutions are not evaporated to as low a solids level as is typical of most glucose syrups because the viscosity of the latter is extremely high (see Table 21.9). At the higher solids level of 43 or 44 Baume typical for com syrups, maltodextrin solutions would be extremely difficult to pump. It should also be noted that, since the water activity of maltodextrins at a given solids level is so much higher than that of other syrups, some care must be exercised in the handling of these products to prevent microbial fermentation. Commercial maltodextrins, as shown in Table 21.1,15 are used in applications where high viscosity coupled with a bland, neutral taste is desirable. 

A practical application of activated carbon catalyzed chlorination is the synthesis of para nitrobenzotrichloride via chlorination at 150-200 °C112. At even higher temperature (250 °C) large-pore carbon, in presence of water vapors, is an effective catalyst for chlorodemethylation of para xylene (equation 6)113. 

Sterilisation of blood products and other organ transplant tissues opens another area for photodynamic effect applications. Photodynamic activity of some inorganic sensitizers together with their photocatalytic activity can be very useful in water, air, and surface detoxification (see Chapter 21). APDT can be a new approach for safe food. The reduction of several Gram-positive bacteria and yeasts has been observed in tests with visible light and haematoporphyrin or chlorophylls (natural constituents of food) as photosensitizers [54],... 

An important case is the application of enzymes in laundry detergents. Market trends in the United States show that consumers prefer liquids to powder detergents by a ratio of 2 to 1. These products are stored with no temperature control on shelves in the presence of harsh surfactants, such as linear alkylbenzyl sulfonate (LAS) and require extraordinary measures for stabilization. LAS, by its nature as an effective cleaning agent, causes surfactant-induced unfolding in proteins. There are countless examples of the development of stabilization systems in the intellectual property space. A common theme is to reduce the water activity and to use borate/glycol stabilizers that bind to the active site of proteases. 

Hydrolytic enzymes such as lipases and proteases catalyze readily reversible reactions and will often promote reverse hydrolysis at reduced water activities. Water can be removed with desiccants, as an azeotrope with a solvent or through application of a vacuum. Lipases have proven particularly useful in this regard, allowing the formation of esters from alcohols and either free carboxylic acids or esters (see Figure 31.12). 

There is considerable worldwide interest in the application of lipases for fat modification and ester synthesis. In systems with low water activity, lipases are able to catalyze ester synthesis as well as interesterification reactions in fats. The lipase reactions under low water activity can be performed in several ways. We consider batch or continuous reactions in melted fats by use of immobilized lipases as the most relevant way for the industry. 

Bone, D.P. 1987. Practical applications of water activity and moisture relations in foods. In Water activity Theory and application to food, ed. L.B. Rockland and L.R. Beuchat. New York Marcel Dekker, Inc. 

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