Ensuring the safety of food is not difficult but it does require the commitment of senior management, the training of all staff Involved in food production and service and the investment in the necessary refrigeration and other equipment

In the U.S. Journal of Food Protection in 1980, the results of a major survey were published. which showed that in virtually all different types of food poisoning outbreak the two major causes were the improper cooling of food and the improper refrigerated storage of food.

The introduction of food safety legislation in the last few years has been extensive but even so, there are frequent outbreaks of food poisoning. one of the latest being trio E Coli epidemic in Scotland, resulting in over fifteen deaths to date.

Food becomes unsafe if two events occur:

• if it is contaminated with pathogenic (harmful) bacteria- These may be airborne but are frequently transferred from other foods by cross-contamination (e.g. from
  raw meat to cooked meat) or carried by pests such as flies.
• if the pathogenic bacteria are allowed to multiply to such an
  extent that the volume of bacteria present will cause people to be ill If they consume the food.

Pathogenic bacteria typically grow most prolifically at blood heat, (about 38^o(C). become dormant at low temperatures (e.g. below +5^o(C) and are killed at high temperatures (e.g.above +63^o(C)

In the majority of cases then, if food is thoroughly cooked and or stored at a high enough temperature, all the bacteria will be killed, and if food is stored at a low enough temperature for a reasonable period of time, it will not permit much growth of harmful bacteria, and therefore not make food unsafe to eat. When food is cooled from a hot temperature to a cold temperature it will pass through the danger zone at which bacteria grow most prolifically. As the food will almost inevitably become re-contaminated by airborne bacteria, it is essential that this cooling process should take place as quickly as possible before the bacteria have time to acclimatise to their new surroundings and start multiplying. Typically this is in the region of 90 minutes and this is one of the reasons why the UK Department of Health recommends 90 minutes as the ideal cooling period from a temperature of +70^oc to +3^oC. This, in fact is the recommended minimum performance of a blast chiller, which should ideally be used to chill foods rather than ";leaving them out to cool"; or placing them in a storage refrigerator when still hot.

The following is a simple guide which helps to prevent cross-contamination and the growth of pathogenic bacteria.

• Deal with goods that need refrigerating as soon as they are delivered to your kitchen.
• Remove all external packaging, which could have become contaminated in a loading bay or on the pavement for example, and place in the appropriate refrigerator, in a clean sealed container if necessary.
• Segregate foods of different risk categories. Them are different interpretations of what these categories are, but it is suggested you adhere to the following:

HIGH RISK FOODS are those which am ready to eat and are therefore most vulnerable. They provide excellent conditions for bacterial growth and are not likely to receive further cooking to kill off any bacteria, e.g. cooked meats,sandwiches, quiches etc.)

LOW RISK FOODS are those likely to contaminate others (e. a. raw chickens, meat etc.), but which will themselves receive same form of cooking to kill off bacteria present within them.

• When re-heating chilled food, ensure that a temperature of at least +70^oC is reached throughout the product and serve within 15 minutes.
• When cooked food is stored or displayed hot, ensure that a minimum temperature of +65^oC is maintained.
• Once food is cooked or reheated do not let it come into contact with uncooked or raw foods (except when required at the point of service - e.g. salad garnish or warm items on a salad base)

The feasibility of different refrigerators for different products will depend upon the size of the kitchen, but you are advised to opt for more smaller refrigerators rather than one large one. if you do have to mix products in one refrigerator, place the high risk products at the top in sealed containers with the low risk products at the bottom.

Ideally the following temperatures should be specified for storing different products

Raw meat and poultry	-2o0 to OoC
Wetfish	-1oC to +1oC (with flaked ice)
Dairy goods	+1oC to +4oC
Fruit and vegetables	+1o0 to +4oC
Cooked foods	0oC to +3oC
Frozen foods	-18oC to -21oC

These are the operating temperatures of the refrigerators necessary to maintain foods at the ideal temperatures. They will not only help to ensure the safety of food but will also maintain quality of food longer and will be of financial benefit by reducing food waste.

The specification of refrigeration is equally important There are two main functions of a refrigerator aerator. of whatever size

• To control temperature
• To enable hygiene maintenance.

To control temperature

• a good quality insulation such as high density polyurethane
• fan assisted air circulation to ensure movement of cooled air around the cabinet or room
• air ducting in refrigerator cabinets to ensure circulation even when heavily loaded
• appropriately sized refrigeration system to cope with continual door opening and heat ingress, especially during hot weather.
• an efficient defrost system.
• adjustable temperature to suit the product being stored.
• accurate temperature display.

To enable good hygiene

• hard non-permeable fabric (e.g. stainless steel, aluminium or new technology plastics)
• coved corners for ease of cleaning
• fully removable shelves and shelf supports
• easily removable door gaskets
• castors to allow movement for cleaning underneath and behind

There are many other features available on refrigerator such as fault diagnosis, service alarm, door open alarm, temperature recording devices etc., but the basic requirements for food safety are to maintain temperature and to allow the refrigerator to he cleaned so that it does not become the source of contamination.

Follow this simple guide and you are almost certain to ensure food safety.

Bob Kingsbury
Delta-T Ltd. 1997