A bulletin for the Australian Food Industry March 1997
Contents: How safe are fruit juices and acid foods? | Genetically modified soya | Foreign objects in foods
Foreign objects in foods
Food safety and hygiene are primarily concerned with the minimisation of risk to public health by appropriate measures to reduce microbial and chemical contaminants in food. However as any food processor knows, the majority of customer complaints and market rejections occur because of real and imagined foreign objects in foods. Of course these objects may also act as a vehicle for either microbial or chemical contamination.
The list of foreign objects which have been found in food is virtually endless and many general food hygiene regulations are aimed at eliminating possible sources of foreign objects in food during preparation procedures. Thus the wearing of hair covers by workers, guards over adhesives or bandages on workers, the prohibition on smoking, the removal of jewellery before entering a food processing plant are all designed to reduce the risk of foreign bodies finding their way into food.
Some of the more common objects unintentionally found in foods from time to time are listed below:
Unwanted parts of the raw food materials. These are probably the most common and while not usually dangerous can result in serious customer complaints. They include fruit pits, the stem or calyx of fruits, peel or shell material and bone fragments.
Insects. Insects in food have been a problem as long as there has been a food industry and consumers take a very dim view of finding either whole insects or insect fragments in purchased food. Unfortunately, the consumer's home can sometimes be the source of the insect and this can lead to disputation between processor and consumer. It is often possible to distinguish by chemical or physical means if an insect has undergone the type of processing to which the food in question has been subjected and processors should be aware of this.
It can also be helpful to identify the insect as a knowledge of its life cycle and habits may provide information on how the insect entered the food. The Division of Food Science and Technology is able to call on expert advice from CSIRO Division of Entomology in these matters.
Metal fragments. These may enter the food during harvesting and pass through the various processes though it is probably more common for metal to enter the food in the factory via machinery or staff carelessness. Springs, staples, nuts, bolts, wire pieces have all been found from time to time. Lead shot in game used to be a common problem A metal fragment is another foreign object which may find its way into food in the consumer's home. It is usually possible to determine this by a careful examination of the type and severity of any corrosion which has occurred on the metal.
Plastics. Plastics are now so widely used that their presence as a foreign body in processed foods seems likely to continue to increase unless processors are especially vigilant. The source of plastics is almost endless in a food factory but a major problem is the inadvertent incorporation in the final product of plastic fragments from packaging used to contain an ingredient of the food in question.
Glass fragments. Glass may be found in any food packed in any type of container. The source of the glass will often be inside the factory rather than a container itself. Because of its potential to do harm, contamination of food by glass is of particular concern. As with metal contamination, the composition of the glass foreign body can be used to help pinpoint the source of contamination.
Many other materials may be mistaken for glass by consumers. These include hard plastics, improperly dissolved crystalline ingredients and struvite, a crystalline material occasionally formed in processed fish products.
Identification of foreign bodies
A wide range of physical and chemical tests may be employed to identify foreign bodies in foods. It is usual, however, to commence an investigation using light microscopy. An experienced microscopist may be able to identify a foreign object without further testing or provide sufficient information for the analyst to select which range of tests will provide further useful information. These tests include scanning microscopy, X-ray microanalysis, infra-red spectroscopy and atomic absorption spectroscopy. Details of these applications can be found in "Guidelines for the identification of foreign bodies reported from food," Guideline No. 4, published by Campden & Chorleywood Food Research Association, Gloucestershire, UK.
Food Science Australia
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