About Cooking Hamburgers

Most foodservice professionals know what the RULE is for cooking hamburgers--a core temperature of:

Color Is Not A Good Clue

Which of these two burgers was cooked in conformance to the RULE?

This IS a safely cooked hamburger, cooked to an internal temperature of 160 °F, even though it's pink inside.	This is NOT a safely cooked hamburger. Even though it's brown inside, it is undercooked. Research has shown that some ground beef patties look done at internal temperatures as low as 135 °F.

Deeper Into the Temperature Issue and the RULE

The science behind the RULE is pretty good, and is based on kill data for the involved pathogen:

 

Center Temperature (°F)	Time For a 107 Kill Rate
130° 135° 140° 145° 150° 155° 160° 165°	121.0 minutes  38.3 minutes  12.1 minutes  3.8 minutes  1.2 minutes  23.0 seconds  7.3 seconds  2.3 seconds

It's clear that the kill rate is conservative enough (seven log factor) to ensure that this very bad bug is effectively eliminated from the hamburger. You can also see how the RULE is associated with the bacterial kill data.

The problem is, how do you measure the temperature without dissecting each and every hamburger and probing it with an digital thermometer? 

At All QA, we see the problem in very simple terms:

• you need something simple, cheap and effective to stick into the burger to give you an immediate answer (disposable T-sticks), or

• you need to cross-calibrate a non-contact thermometer (IR gun) so that the temperature that it gives you will have a good correspondence with the internal temperature of the burger, or

• you need to cross-calibrate the temperature of your cooking surface temperature (using direct contact temperature measurement) and time the cooking of each hamburgers. 

Each of these three methods can be cost-effective and practical for the measurement of proper cooking temperature--the last and strongest line of defense against E. coli pathogenic strains.

Let's call this the "poke it" | "shoot it" | "time it" collection of practical methods.

The "Poke-It" Practical Method

There is an effective, disposable temperature stick that will give an immediate indication of the internal temperature of a cooked hamburger. It is called the T-Stick^®.  The reactive, food safe sensor dot is in the tip.  Stick it in--if it turns color, you have passed the RULE.  Very simple.

Shown here (left side image) are some T-Sticks^® that have been set for 140°F.  They will give a reading after 5 seconds that is very representative of the internal temperature of a cooked hamburger.

Different temperature models are available.  All QA now sells these effective disposable thermometers at attractive pricing.  Please call us to inquire about availability and pricing of T-Sticks^® in higher volume, or order direct on line.

T-Sticks^® are proven and tested and can be used as part of a validated program in your organization. 

The "Shoot-It" Practical Method

Research evidence has shown clearly that the outer skin temperature of a cooked hamburger will show a direct and predictable relationship with the internal, core temperature.  Since the RULE is all about the core temperature of a hamburger, we seem to have something here.  The system works like this:

1. Cook a hamburger on the actual equipment in the retail environment

2. Carefully measure the internal temperature with an accurate digital thermometer or a T-Stick^®

3. Take a temperature reading with a good IR thermometer of the outside of the hamburger

4. Find out the external temperature that corresponds to the RULE internal temperature -- that will be your cooking criterion ("non-contact equivalent temperature" = NCET)

5. When cooking hamburgers, shoot each one and do not stop cooking until the NCET is reached

• Quicker

• Less costly in the long run, since you have only the one-time investment in hardware

• Works with thin burgers (more difficult with the T-Sticks^®)

The "Time It" Practical Method

If the hamburgers that you cook are of uniform thickness, then it is a matter of physics that determines the heat accumulation rate at the core of the burger.  The longer the burger is cooked on a cooking surface of known temperature, the higher the core temperature of the burger gets.  It is a quite predictable relationship.  To set this up, you need to

1. Take a series of careful measurements of the actual cooking surface you will use (most guidelines recommend that you take seven measurements (corners and triangle in the middle)

2. Cook several hamburgers on the actual equipment in the retail environment for different times

3. Carefully measure the internal temperature with an accurate digital thermometer

4. Determine the cooking time that gets you into compliance with the RULE

5. Periodically recheck by repeating steps 1-4 above.

Some Considerations on Choice of a Practical Method

If you are considering some type of action to ensure the proper cooking of hamburgers in your operation, here are some comparative thoughts about the three methods:
 

Method	Advantages	Disadvantages	Equipment and Supplies
"Poke It"	Quickest training period Unequivocal result Approved and tested No need to run your own "calibration experiment"	Recurring cost Doesn't work with thin hamburgers very well Can take more time than other methods If you run out of probes, you are out of compliance	T-Sticks®
"Shoot It"	Probably the easiest to actually do day-in and out Supported by scientific data	Accurate to about 3°F, so you need a little slack in the cross-calibration Need to run your own "calibration protocol" Technique is very sensitive to burger thickness - if this changes, then calibration is not good	ThermaTwin™ IR/Thermocouple Thermometer (AQA 1717) combined with a needle probe thermocouple sensor (AQA49122-K) T-Sticks®
"Time It"	Useful if there is an automated cooking procedure or cooking is in "batches" Approved and tested Doesn't require a measurement step	Accurate to about 3°F, so you need a little slack in the cross-calibration Need to run your own "calibration protocol" and test griddle temperature daily Technique is very sensitive to burger thickness - if this changes, then calibration is not good Not practical for "cook to order" operation - each individual burger would need their own timer	Thermocouple thermometer for taking reference internal temperatures (many choices...we recommend that you call us with information about your budget, personnel and frequency of use) Griddle probe for the thermometer (AQA50014-K) Digital Cooking Timer (commercially available everywhere)

One program will be right for your operation.  Consider All QA Products as your source for the materials and equipment that you will need--we offer discounts and excellent customer service. We can also help you to set up a cross-calibration program (the details are more than we can put here). 

Please call us on our the sales line or send us an email.

B. W. Berry and M. E. Bigner-George, 2001 "POSTCOOKING TEMPERATURE CHANGES IN BEEF PATTIES"  Journal of Food Protection: Vol. 64:9:1405­1411.

Juneja V. K., 0. P. Snyder, A.C. Wlliams, and R. S Marmer, 1997  "THERMAL DESTRUCTION OF ESCHERICHIA COLI IN HAMBURGER" Journal of Food Protection: 10:1163-1166.