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Option 9.6 - Preservatives
and Additives: 4. Natural preservatives
Syllabus reference (October 2002 version) |
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| 4. Natural preservatives are utilised in some food products | Students learn to: |
Students: |
Extract from Senior Science Stage 6 Syllabus (Amended October 2002). © Board of Studies, NSW.
[Edit: 29 May 09]
Prior learning: Science Stages 4-5 syllabus: Outcome 4.8.3.
gather, process and analyse information from secondary sources to trace the historical development of our understanding of food spoilage and the need for preservation techniques and substances
- Gather information by looking in encyclopedias. As well as looking under 'preservation techniques' you could also look under early cultures such as 'Egyptian', 'ancient Greek' or 'ancient Chinese' cultures. You could also look on the Internet. Go to a search engine then enter 'historical', food spoilage' and 'preservation technique' or 'preservative'. You could also enter techniques such as salting, drying and pickling.
- Process what you have gathered by comparing the information obtained from different sources. Decide what is the most relevant information. You could then assemble it in a time line.
- Analyse the information by noting trends concerning different techniques that were used and the climate of that geographic area. Note also the technology that was available at the time a technique was used and if the technique changed in different places at the same time. Are some early techniques still used today?
identify that bacteriocins can be used as natural preservatives
- Bacteriocins or the bacteria that produce them can be added to food to kill competing micro-organisms, such as Listeria, Bacillus and Clostridium botulinum. For example bacteria that produce bacteriocins are added to yoghurt.
describe bacteriocins as chemical compounds produced by a range of micro-organisms which can inhibit the growth of other micro-organisms such as in cheeses and yoghurts
- Bacteriocins are peptides or small proteins that are produced by bacteria, including lactic acid bacteria, whose natural home is the intestinal tract of humans and other animals. The bacteriocins of lactic acid bacteria usually inhibit the growth of closely related bacteria such as E. coli, Salmonella or H. pylori by making holes in their membranes.
- Some foods they are added
to are:
- dairy products: processed cheese and cheese spreads; direct acidified cheeses; pasteurised dairy desserts; fresh and recombined milk
- dressings and sauces
- canned foods
- crumpets
- wine during winemaking
- vegetables during pickling.
- Lately, there has been
a renewed interest in bacteriocins as sparked by the problem of the perennial
loss in worldwide food supply caused by food spoilage. Chemical preservatives,
once considered a must in food preservation, are slowly being eased out of
the market as they are found to be hazardous to human health. As a result,
food researchers are now zeroing in on biopreservation system where good bacteria
are allowed to produce bacteriocins in food where they naturally grow or have
been cultured. Bacteriocins are then purified and used as pure, natural preservatives
in food.
For more information on bacteriocins
Wikipedia, USA
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