Food additives

Food Standard and Quality Control

Lesson 18 : Food Toxicants - Contaminants

Food additives

Food additives are non-nutritive substances added intentionally to food, generally in small quantities to improve its appearance, flavor, texture or storage properties.
There is no limit to what chemical contaminants might be deliberately added to foods during manufacture in order to cause harm to the consumer. In most cases, however, the aim is not to cause harm, but to defraud for financial gain. However, potential harm can still result.

Sudan dyes

The Sudan I-IV group of chemicals are synthetic azo dyes which have been historically used in industry to colour products such as shoe polish, automotive paints and petroleum derivatives. They are not permitted food colours.

During the summer of 2003 it became apparent that chilli powder and related products in the European market, and originating from India, were contaminated with Sudan I-IV at levels between 2.8 and 3500mg/kg.

Although the Sudan dyes were deemed to be toxic, the levels at which they were found were probably not a major health concern. However, the dyes are not permitted for use and they were being incorporated into the chilli powder in order to make it appear to be of better quality than it actually was.

The chilli powder was incorporated into various sauces, which were themselves then used as ingredients in a range of ready meals. With the significant dilution effect of this, analysing the final food for Sudan dyes became a problem, as the levels involved were now very small. Instead a major traceability program had to be launched into to identify and remove all affected products. This involved the withdrawal of over 1000 products, at a significant cost to the food industry.

Melamine has no nutritional value but because it is high in nitrogen, it makes food that uses it as an ingredient appear to have more protein than it actually does and so meet required contractual obligations. Melamine is an industrial chemical found in plastics and was found to have been fraudulently added to wheat gluten and rice protein from China, which was subsequently used in pet foods.

This was a particular problem in the USA in 2007, when a pet food recall was initiated by manufacturers who had found their products had been contaminated. Further vegetable protein imported from China was later implicated. It was claimed that some of the animals that had eaten the contaminated food had become ill, although melamine was not previously believed to have been significantly toxic at low doses.

In September 2008, it was discovered that melamine was present in infant milk powder produced in China. At least four infants are believed to have died as a result, and over 54,000 were receiving.

Spanish Toxic Oil Syndrome

There are occasions, thankfully rare, when an act of adulteration or substitution is not just fraudulent but jeopardises food safety, sometimes with extremely serious consequences. Perhaps the most serious such incident is that which resulted in Spanish Toxic Oil Syndrome. The incident started as a deliberate act of fraudulent adulteration. A large volume of rapeseed oil had been treated with aniline to downgrade it for industrial use. Some unscrupulous traders decided to refine, decolourise and deodorise this oil, mix it with other oils, package and label it as olive oil, and then illegally introduced it on to the Spanish market. Unfortunately, the oil contained a highly toxic substance formed in a reaction between the aniline and fatty acids in the oil.

Over 20,000 people suffered health problems – many with symptoms as severe as respiratory failure and muscle wasting – and as many as 600 people are believed to have died as a result of consuming the oil. The evidence linking the outbreak to the oil was initially epidemiological, and it was only after several years of extensive investigation, involving sophisticated chemical analysis (including GC-MS) that the causative agent was reliably confirmed. A full account of the incident can be found in Wood et al. (1994).


They are chemically diverse group of harmful compounds with correspondingly diverse range of physiological effects. Species of different fungal genera produce mycotoxins, including Aspergillus, Fusarium and Penicillium, in a range of commodities, including nuts, dried fruits and cereals.

Until recently most of the human health issues have focussed on the so-called ‘storage mycotoxins’ mainly, the aflatoxins and ochratoxin A.

These are produced mainly as a result of the growth of the mould on the commodity when it is stored incorrectly - usually at too high moisture levels. Aflatoxin can also be a problem in milk if contaminated grain is fed to dairy cattle.

More recently attention has begun to focus on toxins produced by Fusarium spp., e.g. the fumonisins and tricothecenes (deoxynivalenol, nivalenol). In cereals these appear to be produced mostly while the grain is developing in the field, in contrast to the ‘storage mycotoxins’.

Another mycotoxin that has received recent attention is patulin. This mycotoxin is formed by some strains of the mould Penicillium expansum, which occurs naturally on some fruit and vegetables, but most notably apples. The major dietary source of patulin is apple juice.

Last modified: Monday, 20 February 2012, 6:05 AM