12. Various common food toxins and toxicity

I found the various common food toxins, pathogens and its toxicity.

In food, the common foodborne pathogens are Bacillus Cereus, Clostridium Botulinum, Esherichia Coli, Listeria Monocytogenes, Salmonella, Staphylococcus Aureus, and Asperigillus Flavus.

Peanut butter which is produced by the company contains foodborne pathogens such as Salmonella, Aspergillus Flavus, Staphylococcus Aureus, Rhizopus and Clostridium Botulinum. It also contains mycotoxins such as Aflatoxin which is produced by Asperigillus Flavus.

Bacillus Cereus
- cause Bacillus Cereus Food poisoning and it produces a diarrhoeal enterotoxin.
-sources: milk, dairy products.
- can be identified by the isolation and enumeration of B.cereus, preferably in both the infected food and the faeces of the victims.
- Procedures for isolation and enumeration of B.cereus involve direct agar plating techniques. However methods for detecting B.cereus enterotoxins are neither highly specific nor quantitative.
- Optimum temperature range for this emetic toxin production is 25 to 30 C. the emetic toxin is heat stable and can withstand normal cooking temperatures. So food is to be cooled rapidly to a temperature that prevents the growth of B.Cereus and food to be held in a warm state should be maintained above 60C.

Clostridium Botulinum
- can cause food borne botulism and produces C.botulinum toxin.
- Sources: may occur in almost all food, vegetable or animal origin.
- No microbiology methods are specifically designed for C.botulinum. Methods of enumerating the clostridia usually rely on reduction of sulphite to sulphide with the formation of black colonies which demonstrates the presence of C.botulinum by enrichment culture and toxin tests.

Escherichia Coli
- can cause infection and food borne illness.
- Sources: Milk, meat.
- Isolation of pathogenic E.coli involves plating sample on MacConkey or eosin-methylene blue agar.
- Enrichment and selective procedures would be carried out after black colonies are picked and identified as E.coli.
- Detection for E.coli is facilitated by enrichment and electromagnetic separation. Several biochemical tests are done to identify E.coli and some examples are Gram’s stain positive, indole positive, mannitol-positive, and Voges-Proskauer-negative. Important measures are taken to prevent food poisioning by education food workers in safe food handling techniques and proper personal hygiene.

Listeria Monocytogenes
- can cause listeriosis.
- sources: raw meat, wet sirfaces in food processing plants.
- an opportunistic pathogen that is capable of surving and multiplying in simple nutrient media and outside animal hosts.
- able to grow in simple bacteriological media. It is able to grow at low temperatures and thus multiply.
- Isolation can be done after plating onto non selective media such as blood soy agar and selective media such as modified McBride’s agar. Several enzyme-linked immunosorbent assay (ELISA) methods and nucleic acid probes are available for identification purposes.
- Listeriosis can be reduced whereby HACCP should be applied from farm to consumers to minimize the risk of food borne illnesses.

Salmonella
- can cause gastroenteritis, enteric fever and bacteraemia, focal infections and sequelae.
- sources: food of animal origin.
- Detection of salmonella involves pre-enrichment, enrichment, selective differential plating, isolation and identification.
- enumerated by the most probable number technique though it is a cumbersome procedure and too expensive for use in large number of samples.
- Identification of Salmonella can be done by primary screening on non selective differential agars such as triple sugar iron (TSI), and further identification can be done by biochemical testing of pure cultures. With the use of heat, irradiation, acidification and combinations of factors are used to destroy salmonella in food since low numbers of salmonellae can cause illness.

Staphylococcus Aureus
- can cause staphylococcal food poisoning.
- Sources: mucous membrane, and skin of all food animals.
- method of enumeration is Baird Parker’s medium.
- procedure for detecting staphylococcal enterotoxin in food is a combination of extraction, concentration and final detection of the toxin by the use of enzyme-linked immunosorbent assay (ELISA).
- Control can be achieved by preventing products from contamination and avoiding conditions where growth may occur.

Asperigillus
- produces mycotoxins and can cause mycotoxin poisoning.
- sources: peanut, corn, cottonseed.
- Enumeration of Asperigillus flavus can be done on antibacterial enumeration medium that contains inhibitors to reduce colony spreading.
- Identification of Asperigillus flavus grow rapidly on standard identification media such as malt extract agar. Asperigillus also produces mycotoxins such as aflatoxins which are found to be acute and chronically toxic in both animals and in man.
- ELISA techniques are used for toxin estimation and controlling of aflatoxin in corn can be directly detected when they fluoresce under UV light.


Reference:
Blackie Academic & Professional. Microorganisms In Foods 5. Microbiological specifications of food pathogens. 1996

p.s: book found in school library.

11. When to label food as Genetically Modified?

Found an useful decision tree in the FoodSafety.gov.au website which i think might be useful.
Reference:

http://www.foodstandards.gov.au/_srcfiles/user_guide_GM_labelling_0817.pdf (accessed: 16 June 2008)

10. How to distinguish GM food from natural food?

In the learning issues in our HFLA template, i was to research on ways to distinguish GM food from natural food and these were what i have found.

To distinguish GM food from natural food, it is important to check the presence of marker genes and promoter genes as these genes are using in the process of transformation.
Marker genes are used to quantify gene expression and to ensure that the DNA is properly delivered and transformation is stable. However, for plant cell transformation, marker genes can only be expressed inside cells of the target tissue and not in any contaminating microorganisms.
Also, Promoter genes are used in the process of transformation as it starts the mechanism of the DNA chain and cooperates with marker genes.


Reference:
Genes needed for transformation. http://library.thinkquest.org/C004033F/gmprocess_genes.htm (accessed: 14 June 2008)

9. Advantages and Disadvantages of GM food

Found some information on the advantages and disadvantages on GM food as well.

Advantages:

1. Increase the crop yields to feed the world population
2. Increase the tolerance of crops to adverse growing conditions, e.g. drought
3. improve the nutrient composition of crops, e.g. increase the protein content of rice.
4. Provide resistance to crop pests and reduce the use of pesticides by growing GM food such as Bt corn, i.e. save the environment
5. Improve sensory attributes of food, e.g. flavor, texture
6. Improve the processing characteristics so as to reduce wastage of food and minimize the cost during transport and storage
7. Eliminate allergy-causing properties in some foods
8. herbicide tolerance. Crop plants genetically-engineered to be resistant to one powerful herbicide could help prevent environmental damage by reducing the amount of herbicides needed. For example, Monsanto's strain of soybeans.
9. Disease resistance.
10. Pharmaceuticals. Medicines and vaccines are costly to produce and sometimes require special storage conditions not readily available in third world countries. Researchers are working to develop edible vaccines in tomatoes and potatoes

Disadvantages:

1. Unintended modification of similar species in the neighboring fields due to cross pollination
2. Disturbing the balance of ecosystems, e.g. some animals may lose their home when extending farmland area
3. A chance of developing super pests as DNA is changed
4. The initial genetic structure of both animals and plants will be disturbed
5. Vegetarians may worry about eating plants which contains genes from animals for religious, health or other reasons
6. Unintended harm to other organisms. pollen from B.t. corn caused high mortality rates in monarch butterfly caterpillars. Unfortunately, B.t. toxins kill many species of insect larvae indiscriminately; it is not possible to design a B.t. toxin that would only kill crop-damaging pests and remain harmless to all other insects.
7. Reduced effectiveness of pesticides. there are concerns that insects will become resistant to B.t. or other crops that have been genetically-modified to produce their own pesticides.
8. Allergenicity (Human health risk) There is a possibility that introducing a gene into a plant may create a new allergen or cause an allergic reaction in individuals. testing of GM foods may be required to avoid the possibility of harm to consumers with food allergies. Labeling of GM foods and food products plays an important role.
9. Economic concerns. Bringing a GM food to market is a lengthy and costly process. Many new plant genetic engineering technologies and GM plants have been patented Yet consumer advocates are worried that patenting these new plant varieties will raise the price of seeds so high that small farmers and third world countries will not be able to afford seeds for GM crops, thus widening the gap between the wealthy and the poor.

Reference:

GM Food. http://library.thinkquest.org/C004033F/pros&cons_text.htm (accessed: 14 June 2008)

http://www.csa.com/discoveryguides/gmfood/overview.php

8. What is GM food?

What is GM food?

In Standard 1.5.2, GM food is described as “food produced using gene technology” and is defined as “a food which has been derived or developed from an organism which has been modified by gene technology”, where gene technology is defined as “recombinant-DNA techniques that alter the heritable genetic material of living cells or organisms”.

Reference:
Frequently Asked Questions on Genetically Modified Food. Food Standards Australia New Zealand. Revised on March 2008. http://www.foodstandards.gov.au/foodmatters/gmfoods/frequentlyaskedquest3862.cfm (accessed: 14 June 2008)

7. Process of Genetic Modification

Was tasked to find out about genetic modification
and these were what i have found on the web.

Production of GMOs is a multistage process which can be summarized as follows:
1. identification of the gene interest;
2. isolation of the gene of interest;
3. amplifying the gene to produce many copies;
4. associating the gene with an appropriate promoter and poly A sequence and insertion into plasmids;
5. multiplying the plasmid in bacteria and recovering the cloned construct for injection;
6. transference of the construct into the recipient tissue, usually fertilized eggs;
7. integration of gene into recipient genome;
8. expression of gene in recipient genome; and
9. inheritance of gene through further generations.

Reference:
A.Beardmore John, S. Porter Joanne. University of Wales SwanseaUnited Kingdom. Genetically Modified Organisms and Aquaculture. Page 4.
ftp://ftp.fao.org/docrep/fao/006/y4955e/Y4955E00.pdf

6. Product Recall Procedures

Was instructed to find out more about product recall and its procedures.

What is food recall?
"It is action taken to protect the public from products that may cause health problems or possible death. A recall is intended to remove food products from commerce when there is reason to believe the products may be adulterated or misbranded."

What occurs during investigations?
"It may include some or all of the following steps:
1. Contacting the manufacturer of the food for more information;
2. Interviewing any consumers who allegedly became ill or injured from eating the suspect food;
3. Collecting and analyzing food samples;
4. Collecting and verifying information about the suspected food;
5. Discussions with FSIS field inspection and compliance personnel;
6. Contacting State and local health departments; and
7. Documenting a chronology of events. "

I have also read up that the recall would be classified under 3 classes.

• Class I - A Class I recall involves a health hazard situation in which there is a reasonable probability that eating the food will cause health problems or death.
• Class II - A Class II recall involves a potential health hazard situation in which there is a remote probability of adverse health consequences from eating the food.
• Class III - A Class III recall involves a situation in which eating the food will not cause adverse health consequences.

Reference

http://www.fsis.usda.gov/fact_sheets/fsis_food_recalls/index.asp (accessed: 2 May 2008)