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This research project aims to address the need for a stable sulphite containing reference material that can be used in proficiency schemes and as a quality control material.
Study Duration : October 2000 to March 2002.
Contractor : Campden and Chorleywood Food Research Association
The use of sulphiting agents as a preservative in food is well established. Sulphiting agents act as antimicrobials and as inhibitors of oxidation, enzymic and non-enzymic browning, and a wide range of enzymes (including proteases, oxidases and peroxidases). The term 'sulphiting agent' usually refers to gaseous sulphur dioxide or to the potassium and calcium salts of hydrogen sulphite (bisulphite), disulphite (metabisulphite) or sulphite. For regulatory purposes, sulphite content is always calculated as sulphur dioxide and referred to in either milligrams per kilogram or milligrams per litre.
The use of sulphur dioxide as an additive in foods is controlled by'The Miscellaneous Food Additives Regulations' 1995, and its subsequent amendments in 1997; 1999; 2001 and 2003, which specifies to which foods and at what levels sulphite preservatives may be added. These regulations are necessary as sulphite can have harmful effects on susceptible sectors of the population, especially asthma sufferers, in which case the consumption of sulphites can induce itching, urticaria (hives) and constriction of the windpipe.
When used as a preservative in foods, sulphites are oxidised, undergoing both reversible and irreversible bonding reactions. Because of this, the sulphite content of foods decreases during storage. It is therefore standard practice to add sulphiting compounds to foodstuffs at levels above the legal limit in the knowledge that the total sulphur dioxide content of the food will reduce to below the limit before they are made available for sale. These factors, in addition to the health risk to sensitive individuals, mean that the determination of total sulphur dioxide content in food is an essential enforcement test. Testing is routinely carried out in many food laboratories, and the methodology is well established. There is, however, a need to produce a stable reference material that could be used to check the proficiency of laboratories undertaking the test and for routine analytical quality control purposes
The aim of this project was to investigate the possibility of producing a stable, homogeneous sulphite-containing food product which could be used in proficiency schemes and also act as an analytical quality control material for use in laboratories.
Following initial research on the use of sulphites in foods and previous work on the production of sulphited standard material, two storage trials were undertaken. The first was a short-term trial to investigate the most suitable foodstuff, sulphiting compound, production method, and packaging and storage conditions to be used in the second, main trial. The main trial, carried out over an eight-month period, aimed to determine whether the material was sufficiently stable to be used as a reference point.
In addition to these storage trials, an inter-laboratory trial was undertaken, using samples produced for the main trial, to ascertain the variability of results between a number of different Public Analyst Laboratories when analysing samples for sulphur dioxide content. This data would hopefully also give results that could be used in the certification of the sulphur dioxide content of such a material.
The results of the preliminary trial indicate that batches of sausage meat treated with both sulphiting compounds (sodium metabisulphite and formaldehyde bisulphite addition compound) were stable for two months in frozen storage, and remained unaffected by overnight storage under ambient conditions. This overnight storage was intended to simulate the delivery by courier to laboratories that might be required to analyse the product. Although both sulphiting compounds appeared to be stable, and therefore suitable for use in the main trial work, because only sodium metabisulphite is actually used in foods as a sulphiting agent, it was chosen as the sulphiting compound for the main trial.
The results of the main storage trial indicate that samples of sausage meat produced and stored in this manner are stable for at least eight months in frozen storage. The inter-laboratory trial showed good reproducibility of results between different laboratories. This suggests that the material produced would be suitable for use in proficiency schemes and as an in-house reference material. If produced as a reference material, the product would need to be issued with a reference value, which should ideally be based on the results from a number of the laboratories participating in the trial (excluding any outliers) and corrected for recovery.
It can be concluded from the results of the project that the sausage meat produced, if vacuum packed and stored frozen, would be a suitable standard reference material for use in proficiency testing schemes and in-house quality control.
The final report is available from the FSA Library and Information centre. To obtain a copy, please contact the Enquiry Desk, Library and Information Services, Food Standards Agency (020 7276 8181/8182 or at library&info@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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