Writing in the Journal of Agriculture and Food Chemistry, the researchers describe how magnetic levitation or ‘MagLev’ can be used to take density measurements that could be useful to food processors.
Food industry applications
In the study, the researchers use the technology to analyse the fat content of milk, cheese, vegetable oil and peanut butter, and to estimate the salinity of water and monitor the removal of husk or drying of grains.
They conclude that: “MagLev offers a single inexpensive, and easy-to-use method for measuring the densities of liquids and solids.”
MagLev was applied to the business of analysing food products through the creation of a special sensor, about the size of an ice cube. This sensor consists of a container filled with a solution of paramagnetic ions that has two magnets at each end.
Samples of different materials can be placed inside, and the distance they migrate through the fluid provides a measure of their density.
Benefits and drawbacks
Assessing the performance of the sensor, the scientists said it was accurate, rapid, and flexible, being suitable for a wide variety of liquids and solids including those with irregular shapes.
But they conceded that there are also several disadvantages. Notably, the technique requires a paramagnetic solution that may be incompatible with certain substances. For example, it may cause swelling, extract components or dissolve the test substance.
Other potential drawbacks include a trade-off between sensitivity and dynamic range, an inability to measure densities of samples smaller than 5 μm in diameter and an absence of information on the precise chemical composition of a sample.
Considering these positive and negative points, the scientists said: “MagLev may be particularly useful for analysing samples on the basis of density when the need for small volume, portability, simplicity and low costs is of primary importance.”
Funding for the research was provided by the Bill and Melinda Gates Foundation.
Source: Journal of Agriculture and Food Chemistry
2010, 58 (11), pp 6565–6569
Magnetic Levitation in the Analysis of Foods and Water
Authors: K. Mirica, S. Phillips, C. Mace and G. Whitesides