FOOD HYGIENE IN CATERING

Keywords or Contents or Home

Bacillus cereus

Central kitchen

Cleaning

Clos. perfringens

Contamination

Cook-chill

Cook-freeze

Cooking

Danger zone

Diarrhoea

Disinfection

Feeder kitchen

Food debris

Food handling

Food poisoning

H.A.C.C.P.

Hazard analysis

High risk food

Hygiene

Insects

Low risk food

Microbes

Microbial contamination

Microwave ovens

Personal hygiene

Pests

Physical contamination

Rodents

Salmonella

Sanitizers

Service catering

Spores

Staph aureus

Stomach

Temperature

Thermometer

Toxin

Trade catering

Use By

Contents

12(i) Introduction

12(ii) Sandwich making

12(iii) Catering for functions

12(iv) Takeaways, cafes and restaurants

12(v) Service catering

12(vi) Cook-chill and Cook-freeze

12(vii) Summary

12(i) Introduction

Catering is about providing meals or snacks either as a business or as a service so can roughly be divided into trade catering in which the main purpose is to make a profit and service catering in which the main purpose is to provide a service in meals. Examples of trade catering are takeaways and restaurants. Examples of service catering are work's canteens, school meals, meals on wheels and hospital catering.

All catering operations share the need for basic food hygiene such as cleanliness and temperature control as described in earlier chapters. However there are special problems linked with certain types of catering and it is the purpose of this chapter outline some of these.

12(ii) Sandwich making

In sandwich making the main risks come from either handling the food or from the fillings, many of which are high risk foods.

The hands should be thoroughly cleaned before preparing the sandwiches and as an added precaution sterile, disposable gloves should be worn. Failure to do this could lead to outbreaks of Staph. aureus food poisoning.

Care must be taken that the fillings are stored under appropriate conditions ( between 2ºC and 4ºC for high risk foods ) and used before their 'Use By' dates.

All surfaces and equipment used in making sandwiches must be sanitized before preparing the sandwiches and cleaned then sanitized when the preparation is finished.

If the sandwiches are not chilled they must be sold and eaten within four hours of preparation. Any unused sandwiches must be thrown away. If the sandwiches are chilled they must be separately wrapped (in clingfilm or a similar food safe plastic) and stored at or below 6ºC. These sandwiches must be labelled with a 'Use By' date and sold within twelve hours of preparation. Any unsold sandwiches must be thrown away.

Filled rolls need the same care as sandwiches.

12(iii) Catering for functions

Catering for functions or events including weddings, parties or fund raising events which are either done by amateurs or professional caterers. However the problems are the same in both cases.

Unfortunately this type of catering accounts for a large number of cases of food poisoning, especially Staph. aureus and Salmonella. Most of the outbreaks of Salmonella have been associated with chicken or turkey. The reasons for these outbreaks are likely to be:

a) Inadequate cooking of poultry allowing some Salmonella bacteria to survive the cooking process.

b) Poor handling of food allowing the food to become contaminated with Staph aureus. This indicates a low standard of personal hygiene.

c) Poor temperature control of the food allowing food to spend too long at warm temperatures. This leads to rapid growth of microbes.

The risk of food poisoning in this type of catering can be reduced by:

a) Thorough cooking of poultry to kill the Salmonella bacteria.

b) Good personal hygiene together with a use of sterile disposable gloves when handling food to avoid skin contact.

c) Reducing the time the food spends in the danger zone.

Unfortunately most function rooms do not provide fridges or areas for refrigerated storage so the food will inevitably have to spend some time at room temperature. However this time can be considerably reduced by careful planning.

Buffet food should be chilled as soon as possible after preparation. The food should be transported in a refrigerated trailer between 0 and 5ºC and not by a warm car or delivery van. The food should arrive after the beginning of the function and not left in the function room hours before the function is due to begin, so allowing millions of uninvited microbes to gate crash.

The function should be arranged around the food. The food should be served then eaten when it arrives and not left at warm temperatures until the speeches end. While people talk microbes grow.

d) Unless the function room contains facilities for keeping hot food between 65ºC and 80ºC, hot food should not be served in functions. If the hot food becomes contaminated with microbes when it cools to become warm food and then is kept warm for a few hours, the function could end in an outbreak of food poisoning.

e) The food should be kept covered between preparation and serving to prevent physical contamination or contamination by pests like insects.

f) The function room might not be ideal for serving food but these problems can be lessened with care. The room should be cleaned thoroughly before the function.

Tables, especially wooden ones, should be covered with clean table cloths before the food is placed on them.

Unless there is an adequate washing up area adjacent to the function room, it is safest to use disposable plates and cutlery.

g) All left over food should be thrown away and not kept displayed until the end of the evening or day so that microbes can enjoy the function. Under no circumstances should the food be kept and eaten at a later date.

h) After the display tables have been cleared of food, the tables should be cleaned then disinfected. When the function is over the room should be cleaned and cleared of food debris, so that rodents are not invited.

12(iv) Takeaways, cafes and restaurants

Over the last thirty years the traditional English Chippy has been joined on the high street by a diverse range of ethnic and speciality takeaways from Chinese, Indian, Greek, Italian, Turkish to American fast food outlets. Along with the diversification of takeaways over the last thirty years there has been a similar increase in the variety of cafes and restaurants.

However all these businesses share the need to practise a high standard of hygiene. This includes:

a) The premises should be kept clean and all surfaces should be disinfected at the end of the day.

b) The food should be cooked thoroughly.

c) The food should be kept either below 5ºC or above 65ºC.

d) The food should be handled only when it is absolutely necessary and if need be the handler should wear disposable gloves.

e) The handler should be properly trained in food hygiene and practise good personal hygiene.

f) The ingredients used should be stored at the appropriate conditions and used within their shelf life.

g) All food, whether cooked or raw, should be stored covered.

h) All cooked food which is unsold at the end of the day should be thrown away and not kept tell the next day.

i) Only hot cooked food should be placed in a hot cabinet and under no circumstances should hot cabinets be used to cook or reheat food.

j) Waste should be properly managed and not allowed to accumulate.

k) If microwave ovens are used these should be of the commercial type rather than domestic ones. These microwave ovens should be regularly serviced by a qualified engineer to ensure that they are working properly. Microwave oven thermometers should be used to ensure that the food reaches an internal temperature above 80ºC.

Besides these general requirements for all takeaways and restaurants there are specific hygiene problems associated with certain types of takeaways of restaurants.

a) Chinese and Indian cuisine

With Chinese and Indian cuisine care has to be taken with rice. Although uncooked rice is a low risk food, once the rice has been cooked it becomes a high risk food and is prone to attack by a bacterium known as Bacillus cereus. The name Bacillus cereus is derived from Latin and means waxy rods. This causes a food poisoning loosely known as 'fried rice food poisoning'. This is not an accurate description as Bacillus cereus can also cause food poisoning in boiled rice if it is kept and treated in an unsafe manner.

These 'waxy rods' can grow both in the presence and absence of oxygen and when conditions are unfavourable to them, they can change into spores. Bacillus cereus spores are present in uncooked rice grains and these dormant spores can survive the cooking process. If the rice is eaten immediately after it has been cooked there is no problem. However if the rice is stored between 10ºC and 63ºC the dormant spores may change into active rods. These active rods grow fastest between 28ºC and 35ºC and release a toxin into the rice whilst growing. This toxin is heat resistant and can survive frying or reheating.

If rice contaminated by Bacillus cereus toxin is eaten, illness normally follows between one and five hours. The toxin causes inflammation of the stomach resulting in stomach pains and vomiting. Sometimes there is diarrhoea as well. The illness usually lasts between six and twenty-four hours.

Care has to be taken with curries because many spices, like ginger, are root crops which are heavily contaminated with bacteria, including Clostridium perfringens. Clostridium perfringens spores survive the drying process so are present in dried spices.

Clostridium perfringens food poisoning is best prevented by serving curries as soon as they have been cooked. If this is not possible the curry should be kept hot, above 65ºC. Left over curry should be thrown away at the end of the day and not kept as stock for the next day.

b) Chicken takeaways

The main risk here is from Salmonella if the chicken has not been properly cooked.

If frozen chicken pieces are used they must be stored at -20ºC, until needed. If frozen whole chickens are used they must be thoroughly defrosted in a fridge before use.

Usually fried chicken takeaways rely on frozen pieces. These pieces can be deep fried from frozen but must be cooked to a temperature of at least 80oC. The fryers must not be overfilled as adding too many frozen pieces will reduce the oil temperature thus lengthening the cooking time.

The cooking time will depend on the initial oil temperature, the heating capacity of the fryer and the number of pieces added. If the oil temperature is kept to a constant before the frozen pieces are added, the cooking time will depend on the number of pieces added, and a chart can be made indicating the time needed for the number of pieces added.

Both freezers and fryers need to be well maintained and the temperatures carefully controlled.

Any unsold cooked chicken pieces must be thrown away at the end of the day, if held above 65ºC, or within one hour if kept at room temperature.

When chickens are spit roasted they must be cooked so that all areas reach a temperature above 80ºC. The chicken must either be held in a hot cabinet above 65ºC or rapidly cooled to 4ºC or below then stored in a fridge. A blast chiller is useful in rapidly cooling the chicken. The spit should be cleaned daily and chicken should not be left on the spit when the heat is off.

c) Mince meat in restaurants and takeaways

Most mince meat used in catering is served as hamburgers, but meat balls and doner kebab are also mainly composed of mince. Sausage meat is also a type of mince.

Mincing increases the microbial load of the meat, as the microbes are distributed throughout the product during mincing. Hence mince meat products spoil faster than joints and are more likely to cause food poisoning if care is not taken.

There have been outbreaks of Salmonella from meat balls, sausages and faggots so these foods need to be cooked to an inside temperature of at least 80ºC.

Cooked sausages and hamburgers should be held at least 65ºC and if not sold after an hour, thrown away.

Probably the most risky mince dish is doner kebab. Doner kebabs are generally large minced beef or lamb joints which are shaped by hand. Hence these kebabs are hard to refrigerate and easy to contaminate. The way that they are cooked and cut creates more hazards. Cooking is by an electric spit which heats the outside whilst the middle remains warm, possibly for minutes. There might be insufficient heat to destroy Staphylococci toxins and Clostridium spores. Cutting is by an electric knife which can easily become contaminated by uncooked meat beneath the surface. It takes skill not to cut off any undercooked meat.

These problems are compounded by bad practise such as cutting off too much meat and keeping the excess pieces warm until sold, or switching of the grill whilst the kebab is still on the spit.

The safest method is to use several small kebabs instead of one large joint, and keeping the kebabs covered in the fridge until needed for the spit. The hands should be washed before and after handling the raw meat. All the equipment needs to be kept clean and the electric knife should be washed every time after use.

12(v) Service catering

a) Introduction

Service catering includes school meals, hospital meals, meals on wheels and work canteens.

Unfortunately this type of catering has been responsible for about half the reported cases of Clostridium perfringens food poisoning as well as many cases of Salmonella and Staph. aureus food poisoning in the U.K . The standard of hygiene in hospital kitchens has been historically low, as in the U.K.before 1987, food hygiene in hospitals was not properly regulated and these premises were exempt from prosecution under the food laws. This was unfortunate as the sick are one of the most vulnerable groups and many of the people who have died from food poisoning have been hospital patients. This situation should improve as the food laws (Warning UK only) now apply to hospitals and E.H.O.s are empowered to enforce them.

b) Problems associated with service catering

1) Bad planning

Badly planned kitchens lead to raw and cooked food being in close proximity, hence increasing the chances of contamination. Also badly planned kitchens are harder to clean.

2) Poor handling of cooked food

In service catering the food is often held for a couple of hours between preparation and consumption. It is very important that the food is held in hot cabinets or hot trays above 65ºC. The temperature of these holding units need to be carefully monitored. These units also need to be regularly serviced and properly maintained.

Meals on wheels and hospitals need to take particular care with their hot trays as they are dealing with the elderly and the infirmed. Do not deliver food poisoning.

3) Inadequate cooking systems

When cooking too large a quantity of food with an inadequate heat supply or poor heat distribution, the food stays too long in the danger zone. If joints of meat weighing more than 2Kg are used there is a risk of Clostridium perfringens food poisoning. If the food is to be served chilled, large quantities of cooked food take longer to cool. Instead the food should be split into smaller batches before cooking.

4) Poor staff time management

Often in service catering there are slack periods and busy periods. It is during these busy periods that the staff are more prone to make mistakes which compromise the safety of the food. It is also during these busy periods that staff are more likely to take risky 'short cuts'.

5) Excessive concentration on special diets

In hospitals, medical and catering staff sometimes concentrate on special dietary requirements, such as people with liver complaints, to the detriment of general food hygiene for the majority of the patients.

c) Prevention of food poisoning in service catering

1) Hazard analysis

The idea of hazard analysis is to predict the points in the catering operation where the risks from microbial, chemical and physical contamination are greatest. In an H.A.C.C.P. ( Hazard Analysis Critical Control Points) system the places where the product is at greatest risk are known as Critical Control Points. The catering operation has to be scrutinized to establish the C.C.P.s then these points need to be carefully controlled and monitored. If control is lost appropriate action needs to be taken.

For example when preparing a beef stew in a hospital the potential hazards are:

(i) Cross contamination between raw meat and vegetables. This can be controlled by using differently coloured chopping boards in differently designated areas for raw meat and raw vegetables. Monitoring would be by the kitchen supervisors.

(ii) Cross contamination by handlers. This can be controlled by good personal hygiene, especially by the washing of hands after using the toilet, after handling of waste and before and after handling raw food. Monitoring is yet again by the kitchen supervisor.

(iii) The size of the joints of beef should be reduced to below 2Kg before cooking to prevent Clostridium perfringens food poisoning. This is monitored by weighing the joints of meat.

(iv) The temperature of the stew, when cooking, should quickly be taken to above 80ºC and held there during the cooking process. This can be monitored with a food safe thermometer.

(v) The stew should be stirred frequently whilst cooking, to ensure a better heat distribution and some air reaches all areas. This air inhibits germination of Clostridium perfringens spores. Monitoring is by the supervisor.

(vi) The temperature of the cooked food should be held above 65ºC until it is served. If electrically heated trolleys are used monitoring is by a thermometer.

(vii) When the food has reached the ward it should be served promptly and not left standing at room temperature. Monitoring is by the ward nurse.

(viii) Any left over stew should be thrown away and not kept for use in another meal. Monitoring is by the kitchen supervisor.

2) Training of staff

In service catering ignorance is dangerous, so staff need to be made aware of the risks involved with unhygienic practises. Training is also an aid to motivation. Once handlers have been trained and motivated to practise a high standard of food hygiene the number of cases of food poisoning in service catering will decrease.

3) Recipes and procedures

Recipes and procedures should be written down ensuring that the appropriate food hygiene measures are included so that the food is safe to eat. These recipes and procedures should be strictly kept to and only changed after consulting a food hygiene expert.

4) Keeping of samples

Samples of meals served in service catering should be kept in the fridge for two days after the food has been eaten. Thus if there is an outbreak of food poisoning the cause can be readily identified and appropriate action taken to prevent a recurrence.

12(vi) Cook-chill and Cook-freeze

a) Introduction

Cook-chill and Cook-freeze are normally used in service catering, especially for school meals and hospital food. Some airlines utilize Cook-freeze for inflight catering.

There are economic advantages for large scale organizations to utilize either Cook-freeze or Cook-chill, as these systems lead to a more efficient use of equipment and staff. These methods can also provide a wider choice of menu to consumers.

In both systems the food is prepared, then cooked in a central kitchen, then chilled or frozen, before being transported cold to a feeder kitchen, where the food is reheated before being served. Provided care is taken with temperature control, these systems are safer than conventional service catering. As the staff can work at a steady rate there is no mad rush to meet meal times. Also careful planning can eliminate many of the risks of cross contamination. Since the staff are under less pressure it is easier to integrate cleaning into the system.

However if there is an outbreak of food poisoning from a batch of Cook-freeze or Cook-chill a large number of people can be affected. So as in conventional service catering hazard analysis, training of staff, written procedures and sampling of batches should be practised. Some of the samples can be tested microbiologically before the food is eaten.

b) Cook-chill preparation

In Cook-chill the food is cooked to an internal temperature of at least 70ºC for two minutes to kill all active (vegetative) pathogens. The core temperature should be monitored with a probe thermometer, ideally linked to a temperature / time recording chart. Joints of meat should weigh less than 2Kg before cooking.

After cooking the food should be portioned hygienically into clean metal containers or food grade, heat resistant, disposable plastic ones in a cool room at 10ºC. If microwave ovens are used for reheating, plastic or ceramic containers must be used. The containers should be labelled before portioning with the contents, the date filled, the reheating time and the 'Use By' date. In Cook-chill the 'Use By' date is four days after the filling date. If the food is touched when handling, such as when deboning chicken, sterile disposable gloves must be worn. The food should be portioned within half an hour of cooking.

After portioning, chilling must take place as soon as possible as the food must be chilled to at least 3ºC within 90 minutes. Normally an automatically controlled blast chiller with a temperature / time recording chart is used. The chiller must not be overloaded.

c) Cook-chill storage, distribution and reheating

Storage takes place in a specially designed chill room which should only be used for Cooked-chilled food and not for any other purpose including a reserve chill store for raw product or for staff sandwiches. The chill store should be designed to facilitate stock control. The food should be kept between 0 and 3ºC. However the chill store might reach a temperature of 5ºC for short periods, during defrost cycles, but if the food reaches a temperature above 56C it must be eaten within 12 hours or thrown away. If the food reaches a temperature of 10ºC, or higher, for any time during storage or distribution, it must be thrown away. The temperature of the cold store should be monitored with a temperature / time recording chart. An alarm system should be fitted in case the temperature rises, due to a compressor failure. There should be spare compressor capacity so that the compressors can be properly maintained.

The food should be transported to feeder kitchens at 3ºC. If the food is not immediately reheated on arrival at the feeder kitchen, there must be refrigeration facilities to hold the food at 3ºC, before reheating.

The food should be reheated to an internal temperature of at least 70ºC (but preferably 80ºC) as fast as possible, then served within 15 minutes. The temperature of the food should not drop below 63ºC before it is served.

Unfortunately there are still some hospitals (Warning UK only) which do not follow the Department of Health "Guidelines on Cook-chill and Cook-freeze Catering Systems". Instead of reheating the Cook-chill food in a feeder kitchen on the ward, the food is reheated in a main kitchen, then transported hot to the ward. This seriously reduces the safety of the system.

d) Cook-freeze

Cook-freeze is a similar system to Cook-chill but the food is frozen after cooking and portioning, rather than just chilled. The food should be cooled to -5ºC within 90 minutes of cooking, then frozen to a temperature of -20ºC before storage. Freezing is generally either by a blast freezer or a liquid nitrogen freezer.

When food is frozen quickly small ice crystals form inside the cells of meat and vegetables, whilst when food is frozen slowly large ice crystals form outside the cells causing the cellular structure to breakdown. Hence slow freezing causes a loss of texture and quality as well as making the food more susceptible to microbial attack. Both blast freezing and liquid nitrogen freezing are rapid methods.

Temperature and stock control in the cold stores is similar to Cook-chill except that the temperature is kept at -20ºC.

The shelf life of Cook-freeze is about eight weeks.

e) Comparison between Cook-freeze and Cook-chill

The Cook-freeze system is inherently safer than the Cook-chill system and provides a longer shelf life. However the running costs of Cook-chill are lower than Cook-freeze as the lower the storage temperature, the greater the energy cost.

In Cook-freeze certain sauces, especially those containing eggs need to be reformulated as freezing followed by reheating may result in separation of the sauce. However Cook-chill food is more prone to chemical changes than Cook-freeze food, especially in meat products. This can lead to flavour deterioration such as 'warmed over' flavour.

12(vii) Summary

In all forms of catering the main consideration must be the safety of the food. All catering operations should be carefully planned. The planning should include hazard analysis or risk assessment. The procedures should be carefully monitored to ensure that they are correctly carried out. All staff involved in handling food should be trained to an appropriate level in food hygiene.

If there is any doubt about the safety of any food it should be thrown away rather than sold or eaten.

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© R. T. L. Berg 1999