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Listen to this siteWednesday 2 August 2006
This research project aims to develop a simple, rapid and accurate method for the direct determination of the carbohydrate content of foods by industry and regulatory authorities.
Study Duration : June 1999 to May 2002
Contractor : Central Science Laboratory
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.
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.
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.
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.
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.
There have been several concerted efforts into the development of a simpler and more accurate method for determining the carbohydrate content of foods, for use by both industry and regulatory authorities.
The project was expanded outside of its original scope of using reference materials to determine the accuracy of the pyrolysis-elemental analysis (Py-EA) technique for measurement of carbohydrate in food, to include the analysis of retail products and the comparison of the calculated values with those declared on the label.
This project reports that:
The research demonstrated that the Py-EA technique is a rapid and robust technique for directly determining the carbohydrate content of the foods studied.
Dennis, M. J., Heaton, K., Rhodes, C., Kelly, S., Hird, S. and Brereton, P. The evaluation of a method for the direct measurement of carbohydrates in foodstuffs. Submitted for publication in Anal. Chim. Acta.
The final report is available from the FSA Library and Information centre. To obtain a copy, please contact the Enquiry Desk, Dr. Elsie Widdowson Library and Information Services, Food Standards Agency (020 7276 8181/8182 or at infocentre@foodstandards.gsi.gov.uk ).
Contact
: For any enquiries concerning this research project, please contact the relevant Programme contact or email
science@foodstandards.gsi.gov.uk
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