Food safety starts with temperature monitoring.

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HACCP Hazard Analysis and Critical Control Points is your key to food safety.

Food safety guidelines apply where food is prepared, cooked, stored, displayed or moved. The critical factors for food quality and safety are temperature and pH. Temperature is the single most important factor which keeps pathogens like bacteria under control.

High risk foods are foods where bacteria may multiply if the food is stored at the wrong temperature. They include meat, chicken, seafoods, eggs, smallgoods and diary products. They also include salad vegetables and any prepared food containing combinations of these products. Generally bacteria will grow and multiply at between 5 deg C and 60 deg C so this is the danger zone to avoid or minimize.

Here are some places where you need to measure the temperature of food.

Food delivery. For example if you have uncooked, raw or unprocessed food delivered to your shop. Check that frozen food is still frozen hard. Refrigerated food needs to be 5 deg C or lower.

Food storage. Keep frozen food at minus 15 deg C or lower in a freezer. This will prevent any bacteria from growing. For storing foods for shorter periods keep it in a fridge at 5 deg C or lower.

Thawing food. If food is partly thawed but is still colder than 5 deg C then place it in a fridge and store at 5 deg C or lower. If food reaches 5 deg C or is slightly warmer for under 4 hrs then it generally may be used straight away. If high risk food stays out at over 5 deg C for longer than 4 hrs then don't use it. Thaw food out in the fridge not at room temperature. Or use a microwave oven but remember to use the food straight away as parts of the food may be warm enough to allow bacteria to start multiplying quickly.

Re-cooling food. Generally if food rises above 5 deg C but for less than 2 hrs then it may be put back in the fridge at 5 deg C and used as normal refrigerated food.

Food preparation. If raw foods have to be taken out for processing prior to cooking some precautions apply. Don't leave the food out of the fridge for more than 4 hrs. After preparation return the food to the fridge not the freezer.

Cooking food. To kill all bacteria that may cause food poisoning, food must be cooked at at least 75 deg C. The important thing to remember is that food that has solid portions like some meats and chicken has to reach 75 deg C right through. So you will have to measure the temperature inside the food.

Preparing cooked (hot) food for storage. Food that has been cooked can be left out at room temperature until it cools enough to be put into the fridge. But the food must reach 21 deg C within 2 hrs. Allow up to 2 hrs for the food to cool from 60 deg C to 21 deg C. Then it can be put into the fridge. Then the food must get to 5 deg C or less withing a further 4 hrs.

Serving food. Hot food needs to be served at 60 deg C or over to prevent bacteria multiplying. Frozen food needs to be served frozen at minus 15 deg C or below. Cold food needs to be served at 5 deg C or below.

Displaying hot food ready for sale. Sometimes food is pre cooked and offered for sale hot. It has to be kept at 60 deg C or above to prevent bacteria from multiplying while it is on display or stored. It is important to check that the food is at 60 deg C or above right through and not just on the surface.

Displaying cold food ready for sale. Keep high risk foods or prepared dishes that contain high risk foods at 5 deg C or below.

Re heating food. Food can be reheated but it must be re heated to 75 deg C or above. The reason is that even while food has been waiting at a temperature of 60 deg C there may be some bacteria which survived the initial cooking that may have started to multiply. There could easily have been some un noticed contamination of the displayed or stored food. So the food has to be heated right through again to 75 deg C or above.

Read about using thermometers in a fast food outlet Thermometers.

Pickled and preserved food. Pickling is a widely used method for making foods safe for long term storage. Pickling can be achieved by natural fermentation in a salt solution or by adding acetic acid (vinegar). In both methods the main benefit is that the food becomes more acidic. If pH is below 4.6 then most (there are some exceptions) pathogenic bacteria are at least deactivated.

Food with this low pH can even be stored at higher temperatures but only for a limited time. For example rice prepared for use in sushi products can be made safe if enough vinegar is added to lower the pH below 4.6. The rice and products made from it can then be displayed at temperatures up to 25 deg C but only for specific periods - often around 4 hrs. Specific local food safety guidelines specify the times and temperatures acceptable so these should be consulted.

pH test papers such as Macherey Nagel Duotest 3.5 - 6.8 are a cost effective and easy to use method for testing pH especially for fairly clear solutions or for surface testing semi solid foods. For accurate measurements a food quality pH meter is preferred. These use a pH probe which is specifically designed to withstand contamination by food products.

This article is for general information only. People who handle food should refer to appropriate up to date regulations and guidelines or obtain professional advice regarding their specific situation.

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