Either natural like lead in some soil or artificial like industrial pollutants.
Premises:
A mere increase in size of the place or utensils without proportionate improvement in the hygiene does not ensure hygienic preparation
Utensils should be carefully chosen for mass catering
Design of the location should be well planned.
Appropriate sanitary services should be readily available
Site chosen should be away from industries and other sources of contamination.
Supply of raw ingredients
Supply should be adequate and of satisfactory quality
Food with micro-organisms can be made safe by proper cooking but food with chemicals can not be made safe. Therefore, food with less contamination should be chosen.
There should be national guidelines to suggest quantity of pesticides and fertilizers to be used.
There should be strict quality control of the raw materials being used. If needed, manager should specify the quality criteria of the food being purchased.
Hygienic practices”
Even basic hygiene will make all the difference
Preferably skilled workers properly trained in hygienic practices should be involved. If not, unskilled workers should be at least minimally trained
Hygiene can create both health hazard and economic hardship, especially if people affected are working in industries vital for the economy of the region or country.
Convenience of the supply of raw materials should be well balanced with issues of health
If food is planned to be reheated, then before cooling, it should be half cooked. This will ensure that food is not overcooked when reheating before serving.
Frozen/ chilled food should not be mixed with cooked food to save on fuel, or to improve quality.
How Food can turn Harmful?
Fair & festivals require serving of large quantity of food, while spreading the production over the normal working day or several working days.
This makes use of precooking. Then the food is either cooled for storage and re-warmed before serving.
Else, if the duration is short, food will be kept warm in hotplate or over water-bath.
There are many sources of contamination but they all have the same effect.
This gives sufficient time for the growth of pathogenic micro-organisms that have not been destroyed by cooking or that have reached food by other means.
Therefore, food should be maintained at temperatures either too high or too low for the growth of micro-organism.
But this is not always possible. Because, keeping food above 60 0C may cause the food to be overcooked or dry. Some foods may not tolerate cooling for long time.
An example of layout for mass catering premises
Therefore, dishes that may have to be kept for more than two hours before consumption should not be considered.
Need to serve the food simultaneously for large number of people leads to the employment of large number of staff for various tasks in and out of kitchen. These staff may be of doubtful cleanliness and they may be poorly trained in hygienic principles.
Also food may be cooked at one place and consumed at other place. If reheating facilities are not available at the point of consumption then food is likely to be unsafe.
This will cause health problems even if the place where the food cooked was of satisfactory hygiene.
What needs to be remembered at mass catering?
Though, mass catering is efficient and economical way of providing food for large numbers of people, the workload should be spread for the kitchen staff to ensure adequate hygiene.
Mass catering requires satisfactory food supply and adequate sanitary infrastructure.
Mass catering should see that there is no contamination of cooked food with raw food materials.
Staff should be trained well so that they understand the need for hygiene and to understand the instructions that need to be followed.
Laboratory testing of the food cannot take the place of proper supervision and hygiene.
It should be assumed that all the raw food contains pathogenic organisms which can be killed, removed or reduced to harmless concentrations by appropriate measures.
Good management is essential including, proper quality control, hygienic inspection, and training of staff.
If previous experience is lacking, they should consult experts before embarking on a mass catering.
There must be mechanism to report any occurrence of food poisoning at the earliest.
Whatever the trade and economic considerations, health aspects must take priority.
There is one final rule, that applies to all catering but particularly to mass catering, if you can’t do it properly, don’t do it at all.
normal working day or several working days. 
Participants