Wetting foodstuffs

Widening interest in the quaHty of the environment has led to increased demand for information on a wide range of trace-metal contents of foodstuffs. Trace metals in foodstuffs are normally determined by spectroscopic techniques after complete destruction of the organic matrix. Destruction is achieved either by wet oxidation or by dry ashing additional treatment is normally required in order to obtain the metals of interest in a form suitable for analysis. Both methods of destruction are time consuming and tedious this is particularly true of the wet-oxidation procedure, which has the additional disadvantage of being potentially hazardous the methods require considerable analytical skill and experience. Both methods are prone to produce erroneous results either by the loss of an element of interest or by adventitious contamination from the component parts... 

On the other hand, defluorinated phosphate rock is utilized as an animal feed ingredient. Defluorinated phosphoric acid is mainly used in the production of animal foodstuffs and hquid fertilizers. Finally, sodium phosphates, produced from wet process acid as the raw material, are used as intermediates in the production of cleaning compounds. 

Table 13.3. Mean concentrations (ngg 1 wet wt.) of OCs in certain foodstuffs from Indonesia3...

An example is the determination of mercury in foodstuffs using cold vapour atomic absorption spectroscopy. The organic matter in foodstuffs is destroyed by wet oxidation. The mercury in solution is then reduced to the metallic state and released as a vapour in a stream of air. The quantity of mercury vapour in the air stream is measured by cold vapour atomic absorption spectroscopy. This part off the method is called the end determination. Often, as in this example, the end determination is equivalent to the analytical technique for the method. 

FC finishes alone do not sufficiently prevent coffee, tea and other foodstuffs from dyeing nylon and wool carpets with coloured spots, especially when these liquids are not quickly removed. Stain blocking for these carpets is achieved by the combination of FC products with syntans. The latter are also used for wet fasmess improvement of acid dyed nylon (see Chapter 13). Stain repellency is promoted by hydrophobic finishes, mostly fluorocarbons, but with decreasing costs also by... 

Every substance shows a more or less pronounced tendency to change. This was already stated by the Greek philosopher Heraclitus with the words Everything flows - Nothing stands stiU . For example, wet dishes, moist laundry, fresh bread, etc. dry in the air of a room, iron rusts when it is exposed to air and water, sugar dissolves in tea and so on. The perishing of foodstuffs in unopened cans and even pure chemicals in sealed bottles indicates that the cause for the ubiquitous change of substances is not an interaction between different reaction partners (as chemists believed in former times), but is an intrinsic property of each substance itself. 

Flow analysis is associated with wet chemistry thus, solid samples of diverse origin, e.g., alloys, soils, sediments, sludges and foodstuffs, are normally subjected to in-line treatment in order to form a liquid analyte zone. The two most common examples are in-line sample electrolytic dissolution, where the analyte zone is formed as a consequence of applying a direct electric current to the solid sample, and sequential extractions of soils and sediments. 

Kotz etal. (1972, Decomposition of biological materials for the determination of extremely low contents of trace elements in limited amounts with nitric acid under pressure in a Teflon tube) Hartstein et al. (1973, Novel wet-digestion procedure for trace-metal analysis of coal by atomic absorption) Jackson etal. (1978), Automated digestion and extraction apparatus for use in the determination of trace metals in foodstuffs) Campos etal. (1990, Combustion and volatilization of solid samples for direct atomic absorption spectrometry using silica or nickel tube furnace atomizers) Erber et al. (1994, The Wickbold combustion method for the determination of mercury under statistical aspects) and Woit-tiez and Sloof (1994, Sampling and sample preparation). 

Friend, M.T., Smith, C.A. and Wishart, D. (1977) Ashing and wet oxidation procedures for the determination of some volatile trace metals in foodstuffs and biological materials by AAS. Atom. Abs. Newsl., 16, 46-49. 

LR-NMR is the most commonly used NMR technique to date for quality control in food science and industry, with several official quality control methods in force. The success of the technique is due to several factors, including the power of the method (in terms of information and speed), the early application of the method to foodstuffs, the ecological appeal (no longer needing polluting chemicals), and the relatively low cost of the equipment, making it a very attractive alternative to the tedious wet chemical methods. 

Mono- and dicalcium phosphates are added to farm animal foodstuffs to guard against dietary deficiency of P. Stock feed dicalcium phosphate, CaHP04 2H2O, can be made from calcium hydroxide and most wet process phosphoric acid. Apart from possible reduction of P absorption, the Fe, Al and Mg salt impurities do not seem to be harmful to animals. The current world usage of calcium phosphates in animal foodstuffs exceeds 4 x 10 tons per annum. Over 95% of this usage (generally at 1 2% addition in proprietary products not farm produced) is almost equally divided between cattle, pig and ponltry foods. 

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