An official website of the United States government.
Generally, values for carbohydrate in food for labelling purposes are obtained using an approach based upon the Weende proximate system, in which carbohydrate is measured 'by difference': subtraction of the other proximates (protein, fat, ash, water and dietary fibre) from the total. This is prone to accumulative errors arising from the other analyses involved.
<p>
There is a clear need for an accurate, rapid and universally accepted procedure for the direct measurement of carbohydrate in a range of foods, that could be used by industry and the regulatory authorities to monitor compliance with labelling requirements. Techniques such as the Kjeldahl and Dumas methods are used for protein determination. In these, it is common practise to measure total nitrogen and employ correction factors to provide an analysis, which, though not perfectly specific, is quick, cheap and suitable for purpose.
<p>
The objective of this project was to develop a simple, rapid, automated, accurate and precise method for determining the carbohydrate content of foods, for use by industry and regulatory authorities.
The method chosen for development was based on pyrolysis-elemental analysis (Py-EA), which generates carbon monoxide from carbon sources in foodstuffs.
<p>
When pyrolysed, carbohydrates, such as sucrose, give a high yield of carbon monoxide (CO) as the ratio of oxygen-to-carbon molecules (O:C) is close to unity (1:1). Other components in food (e.g. fats and protein) have a lower ratio of O:C, so yield less CO when pyrolysed. Using this procedure, the carbohydrate content of foods can be quantified by calibration of the CO response against known masses of sucrose. A correction factor can then be applied, subtracting the contribution of protein, fat and fibre from the CO signal. This contribution is calculated by the application of response factors for the percentage of protein, fat and fibre measured in the food using existing methods.
<p>
The Py-EA method was evaluated by comparison with some well validated reference materials and then tested against commercial samples by comparing the results with the information on the label.
<p>Find more about this project and other FSA food safety-related projects at the <a href="http://www.food.gov.uk/science/research/" target="_blank">Food
Standards Agency Research webpage</a>.