19-02 Applications in Biology
Water content and fat-water ratio are two important parameters in many manufactured foodstuffs. Control of product quality may depend critically on them, but the traditional chemical methods of measurements may take between a few hours to a day to complete. NMR methods exist to perform such measurements in less than a minute which is fast enough to help in the control of the production line. Some companies already use spectrometers dedicated to this sort of work, but there is still room for a huge expansion in the market. Routine analysis is a totally trivial task, however, it may take many weeks for a research scientist and a line manager to develop an appropriate method for each particular analytical task, and the number of suitably trained scientists is very small.
Another area of routine analysis is that of fruit juices, beer, and wine. The European Community has sponsored the development of an NMR test for the quality of wine, particularly to detect glycol adulteration. A routine method for determining the alcohol content in fermentation vats in two-three minutes is available. Magnetic resonance allows screening of beer, juices, and wine to authenticate the origin, purity, and blending with other substances and liquids (SNIF NMR spectroscopy).
NMR is also useful as a research tool in food science, and MR imaging is beginning to be applied to foodstuffs as well. An early example was of chocolate showing how heating to 40° C and then cooling produced a permanent change in the chocolate. More recently the effect of freeze-thaw cycles on the structure of soft fruit and vegetables has been followed, and a particular promising use is the monitoring and visualization of the fat content of farmed fish (e.g., aquaculture of salmon).
Chlorine-35 (35Cl) NMR was used to show how salt (sodium chloride) interacted synergistically with the food additive sodium tripolyphosphate (E 400) so that a smaller amount of it still produced the desired effect, and ³¹P NMR has been used to demonstrate the hydrolysis of this additive when it is added to meat. Detailed studies have been made of starch and carrageenans, a polysaccharide obtained from seaweed and used in large quantities in food manufacturing.
Starch and carrageenans are important in creating the correct texture in many foods and a fuller understanding of their properties will help in production of cheaper food of a higher quality and in the more efficient use of raw materials.
19-02-02 Agriculture, Forestry, and Environment
NMR techniques have only recently begun to be applied to plant systems but one major area already established is the phosphorus and nitrogen nutrition of plants. Basic research in this area can hopefully lead to a more efficient use of fertilizers and thereby lead to reduced pollution of rivers, lakes, and the seas.
MR imaging of plant systems is even younger than spectroscopy but in one study of frost damage in pot grown pine and spruce seedlings it was possible to detect damaged and dead root systems weeks before the shoots showed any sign of damage. For instance, with Sweden alone producing 600 million seedlings per year at a price of less than one Euro each, there is considerable financial incentive to prevent frost-damaged seedlings being planted out. As a basic research tool MR imaging of intact root systems could be invaluable in increasing the understanding of how root systems develop, and so help in tackling problems like optimizing the uptake of nutrients (essential in nutrient-poor soil) or in preventing the blowing over of forest trees ("wind throw") which is a source of major economic losses.
Solid-state ¹³C NMR studies of soil have helped soil scientists to understand the rather large and complex organic molecules present in soil. For example, the chemical analytical methods used before the advent of solid-state NMR had seriously underestimated the percentage of aliphatic carbon groups as against aromatic carbon groups. An understanding of soil chemistry is important when studying the nutrition of plants and when considering the environmental effects of, e.g., acid rain or radioactive fall-out after the nuclear power plant accidents.
A full understanding of the consequences caused by increasing levels of greenhouse gases (especially carbon dioxide and methane) must include the whole of the carbon-cycle. The soil is an important element of this cycle, having immense amounts of carbon temporarily stabilised in the form of humus.
Direct monitoring of pollution is also possible, particularly in adverse environments, e.g., the artic seas. The size of mussel populations, counted by divers, are currently used as an indication of pollution. Recent laboratory results have revealed quite distinctive changes on the ³¹P spectra of mussels when subjected to low doses of petrochemicals (benzene, phenol, formalin) or heavy metals (cadmium, zinc, lead, mercury). It is hoped that a pollution monitoring system might be developed from this work.