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Food manufacture

Food nasties

In the core strand, Food manufacture, you are required to know the reasons for preserving food, one of the key reasons is food safety. Preventing microbial growth is the basis of food preservation.Although there are a number of bacteria which can cause food poisoning, three that have received a lot of publicity are listeria, salmonella and Escherichia coli.

Outcomes
This material addresses aspects of the following syllabus outcome:
H1.4 The student evaluates the impact of food manufacture on the individual, society and environment.

Source: Board of Studies NSW, Stage 6 Food Technology Syllabus, Preliminary and HSC Courses (1999)

A good source of information on food safety and hygiene is:

Food safety and hygiene: A bulletin for the Australian Food Industry

Activity

The activities in this tutorial focus on articles held on the above web site. Read the articles to enhance or revise your knowledge of food poisoning.

Listeria

Listeria is a psychrophile, that is, it grows in cold conditions. Chilled ready-to-eat and refrigerated foods hold the greatest risk. While infection from listeria is uncommon, it is very dangerous to the unborn child. If a pregnant woman contracts listeria there is a high risk that the unborn child will be infected. This can lead to still birth, miscarriage, premature birth. If the baby is born, it can be very sick.

Examples of foods that may cause problems are:

• soft cheese such as brie, camembert and ricotta (these are safe if cooked and served hot)
• takeaway cooked diced chicken (as used in chicken sandwiches)
• cold meats
• pate
• pre-prepared or stored salads
• raw seafood (such as oysters and sashimi)
• smoked seafood such as smoked salmon, smoked oysters (canned are safe)

Source: ANZFA

Raw milk cheese and listeriosis October 95

1. Who is at greatest risk of listeriosis?
2.  In which foods are you most likely to find listeria monocytogenes?
3. What impact will the outbreak of listeriosis reported in the article have on the export of raw milk cheese from France to countries such as the US ?

Cheese from unpasteurised milk and listeriosis August 1999

This is a follow up article to October 1995.

1. What do you think would be a likely recommendation regarding cheese made from unpasteurised milk?

Salmonella

The Salmonella class of microorganism is fairly easily destroyed by heat, however samples of Salmonella have been found in egg and meat products that have been frozen for two years. So, Salmonella can lay dormant in frozen foods. The freezing method and the type of food may have some influence on the survival of Salmonella In the past it was believed that it was unable to grow at pH levels below 4.5, the following article suggests it is questionable.

 Salmonella from unexpected source May 1996

1. Salmonella is usually linked to animal products. What other products have been found to be contaminated?
2. State three factors that increase microbiological risks.
3. Salmonella is generally unable to grow at pH levels below 4.5. Explain why there is some doubt about this statement.

Extension reading

Another article on Salmonella and orange juice can be found in the May 1999 issue - Salmonella in unpasteurised orange juice. This is quite a long article, but if you scroll down you will find some discussion about the Australian Food Standards Code for fresh orange juice and other recommendations.

Enterohaemorrhagic Escherichia coli (EHEC)

Enterohaemorrhagic Escherichia coli (EHEC) can cause severe reactions in humans including damage to the renal system. This organism does not grow below 7°C. Although it is generally prevented from growing in acidic conditions, it is possible the organism may still survive. EHEC is heat sensitive, so it is less likely to occur in cooked foods.

Enterohaemorrhagic Escherichia coli outbreak in Japan December 1996

1. Based on anecdotal reports, state one reason why there was an outbreak of Enterohaemorrhagic Escherichia coli (EHEC) in Japan.
2. Cross contamination and EHEC is a problem. Most cases of food poisoning have been linked to raw or undercooked meat. However, apple juice has been a source of infection in the US and Canada .
   Why would apple juice be a risk?
3. Based on this information, and from your own knowledge, write guidelines for the prevention of EHEC food poisoning.