An official website of the United States government.
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.
<p>
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 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.
<p>
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.
<p>
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
<p>
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.
<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>.