Today i am going to update more about the various types of hazards.

1. Different classes of hazards
Basically, there are 3 different classes of hazards, physical, chemical and biological.

1.1 Physical hazards
Physical hazard is any foreign or harmful objects that is not presently found in the food itself.
Examples: Glass, hairs, metal, etc

1.2 Chemical hazards
Chemical hazard can be classified into 3 categories. They are naturally occurring, intentionally added and unintentionally added.
Naturally occuring chemicals found in food products can be mycotoxins, shellfish toxins and etc.
Intentionally added chemicals would usually refer to preservatives in food.
Unintentionally added chemical would be pesticides, cleaning agents, fertilisers from plant and etc.

1.3 Biological hazards
Biological hazard usually refers to the potential of growing microorganisms or the presence of microorganisms in ingredients. There can be many different type of biological hazard depending on the type of microbes grown. There are basically 5 different categories of microorganisms.
They are: Yeast, mold, bacteria, virus and protozoa. Another type of biological hazard can be caused by parasitic worms.

I am going to touch further more on biological hazard caused by bacteria. There are basically 2 types of bacteria.
1. Spore-forming
2. Non-sporeforming

1.3.1 Spore-forming bacteria
Spore-forming bacteria such as Clostridium botulium and bacillus cereus are more common in food. Identification of these bacteria is very important in food because the spore that are formed from bacteria has high resistance to heat, freeze and chemical. The vegetative cells of bacteria would be killed through the cooking process, however, it is the spores which will survive through the harsh conditons of the cooking process.

1.3.2 Non-sporeforming bacteria
Non-sporeforming bacteria is very common in many food, and some examples were Salmonella, staphylococcus aereus, e-coli. This category of bacteria is of lesser issue as most of them would be destroyed due to high heat treatment during cooking.

The presence of biological hazard is essential for us to control, however, it depends on the product itself. For certain products where further step is used to eliminate these microbes, there is no need for us to control it. Such methods could be freezing and high heat treatment.

References
1. Seafood Network Information Center, Sea Grant Extension Program. http://seafood.ucdavis.edu/haccp/training/slides/chapt02.ppt; accessed on 3th May 2008

2. Dr. M.A. Cousin. Department of Food Science, Purdue University, West layfayette, IN. Spore forming bacteria in foods. http://www.math.unl.edu/~jump/Center1/Labs/Sporeforming%20Bacteria%20in%20Foods.pdf; accessed on 3th May 2008