CULINARY INFO
Food Hygiene IV
"DISCLAIMER"
The information contained here is supplied for your interest only and further research may be required.
I have gathered it from many sources over many years. While I attempt to insure they are crossed referenced for accuracy,
I take no responsibility for mistakes - additions or corrections are welcomed.
Food
To understand how to control them we must first understand what Bacteria require for growth or to multiply.
Bacteria are asexual and multiply by a process called 'binary division'. This means that under the right conditions they will split into two. For this process to take place they require:
- Moisture
- Food
- Warmth : 37C (98.6F) which is our body temperature
- Time : if all of the above is in place, bacteria will multiply every 20 minutes.
Note that they do not require oxygen to survive, in fact many pathogens thrive in air tight conditions, i.e. clostridium botulinum, so if not properly sterilised, bottled vegetables, canned goods etc can also be source of pathogens. Great care must be taken when producing home made bottled goods, preserves etc.
In ideal conditions, a single bacteria can multiply in 24 hours to: 9,000,000,000,000,000,000,000,000,000,000 BUT REMEMBER we are never normally talking about a single bacteria, but millions! With 3 million of them fitting on a pinhead!
Which should make you think twice about eating that food you left standing on the stove overnight! ;-)
Now by understanding thier requirements to multiply, we can look at how to control or destroy them. Basically if we remove one of thier requirements we are on our way to control them, if we remove more than one we are on our way to destroying them. Lets look at this in detail.......
The most important of the bacteria requirements is the warmth or temperature they require. If we control our temperatures in the kitchen we can can control the bacteria growth or destroy them.
CONTROLLING BACTERIAL GROWTH
- -18C (0 F):
The temperature that freezers should be running at. Freezing does not destroy bacteria, pathogens or their toxins and spores. In a freezer bacteria are merely in a state of suspended animation or a hibernation state. They will not multiply, but nor will they die. - 0C to 4C (32 to 39F):
The temperature that refrigerators/chillers should be running at. Chilling food does not destroy bacteria, pathogens or their toxins and spores. In a chiller bacteria merely slow down their rate of reproduction to a virtual stop, they will however continue to multiply, all be it very slowly - 65C (149F):
Most bacteria will start to die at this temperature - 70C (158F):
The internal temperature of foods should reach this to ensure any bacteria has been destroyed. To achieve this solid foods such as roast meats and steaks need to be thoroughly cooked until the juices run clear (no signs of blood). Liquid style foods such as sauces, soups and stews etc should be brought to a boil (while stirring) and simmered for a minimum of three minutes.
NEVER reheat foods more than once or the bacteria in the food will not only multiply as the food is cooled down and stored, but they will also become heat resistant. Bacteria are capable of producing spores; this heat resistant shell will resist the most ardent cooking temperatures and food poisoning is inevitable.
THE DANGER ZONE
This is the temperature zone at which bacteria will multiply: 5C to 65C (32F to 149F). When food is held within this zone, bacteria will multiply and could end up being a problem and cause food poisoning. To ensure this doesn't happen:
- Take a chilly bin with you when shopping to place ant chilled or frozen foods in to transport home.
- Plan your shopping so that any other chores are completed first: checking your mail box, clothes shopping, coffee or lunch, visiting freinds etc....always go straight home after grocery shopping.
- Place chilled and frozen foods away as soon as you arrive home.
- Leave fresh meats or fish in the refrigerator until just before you need it and ensure it is covered (to stop flies etc landing on it)
- When you go on a picnic or have a bbq, ensure the food is kept in a chilly bin with ice to keep it chilled.
DEFROSTING FOODS
Defrost foods in a sealed covered container, slowly in the refrigerator, DO NOT leave defrosting on the kitchen bench overnight.
STORING FOODS IN THE CHILLER
- Store all raw meats below cooked foods (preferably on the bottom shelf)
- Store all raw meats in sealed containers (both of these points will prevent any blood dripping onto foods below
- Store all raw meats and fish seperately; do not mix poultry and beef for example in the same container.
- Keep all fruit and vegetables, dairy products and foods that require no further cooking away from all raw meats and fish
- Thoroughly clean your refrigerator as needed (at least once a week)
BACTERIA ON WORK SURFACES (benches, knives etc)
Tea towels are PUBLIC ENEMY #1!! The moment a tea-towel is used for drying dishes etc it is 'unclean'. Further use of it will only only help spread bacteria.
Application of heat: the best method to control and destroy bacteria is the application of heat, however the following points must be considered:
1. Wet heat is far more effective than dry heat; it destroys the pathogens far quicker
2. Temperatures in excess of 70C must be used; however above 80C is preferred and will be safer
3. Washing, disinfecting and sanitising with hot water is far more effective and quicker than using chemicals (and cheaper!)
Using chemical agents
There are many commercial and retail chemicals available to banish bacteria from your work surfaces. They all no doubt do what they claim they will, but using water at the correct temperature will do the job not only better, but also quicker and cheaper. Common chemicals used for cleaning are:
- Detergents: unless they have an anti-bacterial agent are used to remove grease and dirt, by forming an emulsion between them and the water.
- Disinfectants: used to reduce the levels of bacteria to a safe level
- Sanitisers: will eliminate most bacteria
- Use only in the manufacturer's recomended amounts
- Use only in the manufacturer's recomended water temperature (too cold or too hot can render the chemical useless)
- Use only as per the manufactureres instructions: most require being left on the surface for an hour or so to be effective
- Most will require being rinsed off after being left on the surface for required amount of time or they will contaminate your foods
By far the most effective method of destroying bacteria is cleaning with water at the correct temperature, especially as it will clean and disinfect or sanitise at the same time. Cancelling the need for purchasing and using chemicals.
Water temperature must be as hot as possible
- 82 C (176F) for disinfecting
- 100 C (212F) for sanitising
Which has got to be good for all of us!!
WASHING YOUR HANDS!
Frequent hand washing is an important step in eliminating food poisoning cases. Hands should be washed in as hot as water as the hands can stand, with soap and a nail brush. They should be dried with paper towels, roller towels or hot air blower.
When should you wash your hands?
- After touching your hair
- After touching any part of your face
- After blowing your nose
- After visiting the bathroom
- After handling raw meats and fish
- After handling chemicals (cleaning agents etc)
- After handling garbage
- In between changing tasks: between handling raw meats and cutting cooked meats, between handling raw fish and cutting fruits and veg etc
All equipment for these tasks should also be thoroughly cleaned.
CROSS CONTAMINATION
Cross contamination: "The contamination of safe foods from unsafe foods via a vehicle". By following all of the above should eliminate the possibility of contaminating your nice fresh, clean foods with bacteria from unsafe foods and minimise your chances of getting food poisoning.
