Time and Temperature
In the first two chapters we talked about Foodborne Illnesses and how contamination happens. In the chapter three, we talked about your staff and how their work practices and personal hygiene can significantly help reduce cross contamination issues.
In this chapter, we are going to take the fight against foodborne illness and concentrate on the two areas that can have a serious impact on food safety within your operation.
These two areas are known as Time and Temperature Controls.
Simply put, if you get these two controls right, you will significantly reduce the risks of a foodborne illness outbreak!
THE JOURNEY OF FOOD
Over the next four chapters, we are going to follow “”The Journey of Food”” as it passes through your operation.
The best way to do this is to visualize the food on this journey, and at each stage, establish what the issues could be, understand the time & temperature controls required, and determine the processes you can implement to reduce the chances of a foodborne illness outbreak.
Within the next four chapters, we are going to look at all aspects from purchase, through delivery and storage, to preparation, cooking, and serving to the consumer.
To start, we are going to run through the basics and concentrate on Time-Temperature. We have already discussed many of the points. However, the points are so important that it is worth reinforcing them as we go through the “Journey of Food”
TOP 10 CAUSES OF FOODBORNE ILLNESS:
Take a look at the following list. What is the key thing that you notice?
- Preparing food too far in advance (time & temperature)
- Cooling food too slowly (time & temperature)
- Food handlers touching raw then cooked product (cross-contamination)
- Poor personal staff hygiene (cross contamination)
- Not cooking food to the correct temperature (time & temperature)
- Not storing food correctly (time & temperature)
- Not reheating food to the correct temperature (time & temperature)
- Not thawing food properly (time & temperature)
- Time to put deliveries into storage (time & temperature)
- Not hot-holding food at the correct temperature (time & temperature)
8 OUT OF THE 10 MOST COMMON CAUSES OF A FOODBORNE ILLNESS ARE TIME & TEMPERATURE RELATED. As we mentioned, when you get these two controls right, you significantly reduce the risk of a foodborne illness!
THE TEMPERATURE DANGER ZONE
The Temperature Danger Zone is 41°F to 135°F.
Pathogenic Bacteria love any temperature between 41°F and 135°F. Given the right conditions as mentioned in Chapter 2, they can multiply every 10 to 20 minutes, (Binary Fission). If given enough time, even food previously prepared or cooked that is then left in this Temperature Danger Zone will become contaminated again!
In addition, pathogenic bacteria multiply at their fastest at temperatures between 70°F and 125°F. These are typical temperatures that you will find in a kitchen.
The simplest and most effective way of reducing the chances of a foodborne illness is to restrict the time food sits in the Temperature Danger Zone. Do not give pathogenic bacteria the chance to multiply!
At temperatures above 135°F and below 41°F, many bacteria will die or become dormant. They do not have the right conditions to grow or multiply.
MONITORING TIME AND TEMP
As a manager, we would suggest that controlling Time & Temperature is your most important role. Make sure that your staff monitor time and temperatures throughout the “Journey of Food”. Staff must be fully trained, aware of the risks, and you need to constantly monitor their actions.
Download and print the Temperature Danger Zone illustration, and place it in areas of the kitchen that staff can easily see, usually around the prep and cooking areas.
Also, ask them weekly what the Temperature Danger Zone is. You want them to be able to recite it in their sleep!
As the manager, (PIC), you need to feel confident that the food you are storing, cooking, reheating, or hot holding is at the right temperature. The only way for you to be confident that food is at the right temperature is to accurately and consistently measure temperatures.
Without the use of temperature probes, you might as well just guess!
There are two main types of temperature probes, portable and built-in devices.
Built-in Temperature Sensors
Sometimes called Air Probes. A lot of equipment you have in your kitchen will probably already have built-in devices. For example commercial refrigerators, walk-in coolers, freezers, ovens, and hot-holding units.
These offer a great way of checking temperatures, especially when checking the daily temperatures of coolers and freezers.
However, as a manager, you need to be aware that built-in sensors have their limitations.
They only measure the air temperature NOT the temperature of the food itself. This is an important point to remember when cooking food.
If the doors of a refrigerator or freezer are opened often in the day, or left open for long periods, the temperature readings can vary.
Refrigerators and freezers need to be regularly checked and calibrated if needed.
An additional hand-held infrared thermometer is a good backup to check refrigerator and freezer temps and also delivery wagons. They are relatively inexpensive nowadays.
Portable Temperature Probes (Handheld Units)
- Immersion Probes, which are ideal for liquids such as soups, sauces, frying, or cooking oils.
- Penetration Probes, which include Bimetallic Stemmed Thermometers and Thermocouple, digital thermometers are ideal for foods such as meat, poultry, fish where you need to record the temperature at the center or thickest part of the food.
These are all excellent and absolutely vital in cooking, re-heat, and hot hold procedures, as they will accurately read temperatures at the center or core of the food.
They are also vital in checking the temperatures of items that are in the preparation area. If you have a concern about a food product and you think it may have been left in the Temperature Danger Zone for too long, a hand-held probe will give you an accurate answer.
Digital Probe Thermometers and Bimetallic Stemmed Thermometers are the types recommended and it is good practice to have several in your business.
HOW TO MEASURE TEMPERATURES WITH A PROBE THERMOMETER
Be sure to sanitize the probe before touching the food.
As you near the end of the cooking phase, place the probe in the thickest part of the food, usually at the center, and wait for the thermometer to give a steady reading.
You can temperature check in other areas, just make sure you get a reading from the thickest part first.
Then remove the probe and sanitize it.
While temperature probes are an excellent and needed way to accurately monitor temperatures, if not cleaned correctly, they can also act as the perfect “vehicle of contamination”.
They must be cleaned with a sanitizing wipe before use and then immediately after use.
For example: If you check the temperature of a raw chicken breast and then immediately test the temperature of a cooked joint of meat without cleaning the probe, you have cross-contaminated the joint of meat.
As a manager, it is your responsibility to train staff in the correct use of temperature probes; how and where to probe, and how to clean. They will also need to understand where the temperature information is recorded and why it is necessary.
Calibrating a Probe Thermometer
Calibrating a probe or bimetallic stemmed thermometer involves checking the boiling point of water which is 212°F, and that freezing point of water which is 32°F.
To calibrate at 212°F, agitate the digital probe thermometer in a bowl of boiling water, or steam from a boiling kettle. As soon as you pour boiling water into a bowl, it starts to cool, so you need to be quick, whereas a boiling kettle will hold its temp for much longer.
The only acceptable readings are 210°F, 212°F, or 214°F. If you get a reading outside this range, the batteries should be changed, or the unit should be repaired or thrown away.
Let’s now use a Bimetallic Stemmed Thermometer to demonstrate the lower temperature. Fill a container with crushed ice, add tap water until full, and stir the mixture.
Put the thermometer stem in the ice water just past the sensing area. Do not let the stem touch the container. Wait for at least 30 seconds or until the indicator stops moving.
If it needs adjusting, hold the calibration nut with a wrench and, if needed, rotate the thermometer head until it reads 32°F, (0°C).
If you use a digital probe thermometer, use the same method to test. The only acceptable readings should be 30°F, 32°>F, or 34°F. If you get any reading outside this range, the batteries should be changed, or the unit should be repaired or thrown away.
Final, final point! We call this, PROVE IT!!
Use the attached form and check all thermometers on a monthly basis. Your local health official will be impressed.
Many DOH jurisdictions will accept a documented rotation procedure for the replacement of thermometers. Determine if your local DOH jurisdiction will allow a variance for calibration of thermometers.