Food Toxicology 2(2+0)

Lesson 9 : Toxicants Found in Foods

Bacterial Toxins

The causes of food borne diseases are many, but bacteria are the most common. In order of economic significance, bacterial toxins are the most important, followed by mycotoxins and aquatic biotoxins. Bacterial toxins have the highest significance with respect to public health. Although mycotoxins have been responsible for individual acute poisoning outbreaks, primary concerns regarding mycotoxin contamination in foods and feeds are related to both human illnesses due to long-term, low level exposure and animal health. A pathogenic bacterium is where the human illness is associated with food borne toxins. According to the Council for Agricultural Science and Technology, Bacillus cereus (diarrheal type), Clostridium perfringens, enterohemorrhagic and enterotoxigenic Escherichia coli, and Vibrio cholera are the toxicoinfecting bacteria frequently documented as foodborne disease agents.The toxins produced by these organisms require linkage to and/or invasion of the intestinal epithelial cells and damage to specific cells. On the other hand, Bacillus cereus (emetic type), Clostridium botulinum, and Staphylococcus aureus are toxicogenic bacteria which synthesize toxins in the food, and their presence is not required to cause illness. On the other hand, although there is a paucity of information on aquatic biotoxins, contamination of seafoods with these toxins has the highest potential human health risks because of the widespread distribution. The microbial diseases are on the rise. The reasons for the increase in foodborne illnesses are as follows.

1. There are better epidemiological capacities and better means to report cases, as well as better means to detect and identify food borne illnesses.
2. Over the last few decades, people have made significant changes in their lifestyle and food consumption. They eat out more often, travel more, and choose exotic foods more often.
3. Vegetables and fruits come from different countries, which sometimes have different sanitation standards and different strains of microbes.
4. As a working society, we have gotten further away from food preparation and as such there is less emphasis on teaching about food preparation.
5. At present, school curriculums rarely contain safety instructions for preparing food, i.e., home economics classes.
6. People consume more meals in restaurants, where food passes through many hands, thereby increasing the chances of food contamination due to improper handling.
7. Also, consumers’ demand for natural or organic foods has resulted in more unpasteurized food production.
8. Food distribution is more global, which has increased the possibility of problems becoming more far-reaching. With larger operations, one mistake in food preparation can affect large numbers of people. Large production can increase the potential for cross-contamination.
9. Microorganisms are developing resistance to antibiotics. Overuse of antibiotics has increased the incidence and decreased the ability to treat microbial diseases.
10. We are also to blame because we fail to use sound food safety practices in our homes. Our food handling practices, such as lack of good cleaning techniques in the kitchen, careless hand-washing, and not observing food temperatures between 40 ? and 160 ? F (4 ? and 68 ? C, respectively), have put us at greater risk. Some still believe that foods should be cooled to room temperature before being refrigerated. This belief comes from the practice of placing hot food into iceboxes, causing the hot food to melt the ice, thereby spoiling all the food in the icebox.
11. Microbial-related food borne diseases can be due to either infections or intoxications.

Diseases involving the pathogen itself are infections, and those involving the pathogen’s toxic products (toxin, toxic metabolites) as causal agents are intoxications. Intoxications also refers to foodborne illnesses resulting from other natural sources.

Table: Sources of some toxic materials in foods

S.No.	Sources	Examples of toxic materials
1.	Naturally present	Solanin(potato) Scombrotoxin(fish) Gyanogenic glycosides(tapioca) Mercury(black marlin)
2.	Process induction	Polynuclear aromatics(smoked Food asdditives products) Nitrosamines (cured meats) Lysinoalanine (alkali treated soy protein)
3.	Contaminants	Heavy metals(fish, molluscs) Mycotoxins(peanuts, grain) Vinyl chloride(PVC packaging) Asbestos fibres(beverage filtration)
4.	Food additives	Nirrate, nitrite(meat curing) Monosodium glutamate(flavour enhancer) Diethyl pyrocarbonate(beverage steriliser)