Oven Calibration

Hi! We are currently doing our HACCP Plan. We had identified baking as one of our CCPs but one of our coordinator is insisting that we can omit and that we just have to validate the kill rate(temperature and time) for microorganisms during baking. We did the validation and all our products passed the kill rate and even go beyond it. Our worry now is that we don't have any calibration procedure for our ovens which we think is essential during the certification process. We plan on doing the calibration, thus I am searching for the procedure on how to calibrate the oven. Ours is a rack type of oven. Thanks.

Your internal calibration is valid only if you have master temperature probe which is calibrated and certified with NIST.
So, contact a certified calibration body who can help you out for doing the Annual calibration - after calibration they provide
certificate with information of the master standard traceable to NIST - which you can check in net for its validity. Also, they put a
calibration sticker with details in the front of your oven. So, you have to calibration once in every year before the expiry period of the certificate.
Some calibration companies give certificate which is having validity for 2 years.

After this yearly calibration, its mandatory for you to do monthly and daily calibration and maintain the records. This is to ensure that
your instrument is working properly. If you have any breakdown/ problem in the oven after the calibration, but within the calibration validity period - you have to calibrate it again.

Dear mck,

Have no idea what you mean by kill rate ? > 6D bacterial reduction factor ?? The question of baking a CCP or not is probably debatable, see the parallel thread (GMO) now running here.

Presumably the temperature is >> 100degC. Presumably you also know where yr current probe is located.
(The only primary temperatures standards which are readily available for self-calibration are 0,100degC)

To calibrate the oven you probably need a certified (or traceable to a certified) thermometer to be placed adjacent to the one currently in use. The usual way is to purchase a suitable, portable, “master” thermometer (presumably a thermocouple) and have it officially calibrated (eg certified traceable to NIST) at appropriate points (including 100degC for yr own later cross-checking) followed by annual (or less) re-calibration. This can be used to “sub-certify” other units if you wish. Not necessary to be portable but normally convenient. May involve long lines so suitable sheathing materials will be required.
Assuming the TC can be manually reset, the calibrating company will often ask if you want it set to be perfect at some specific point, eg close to the usual baking temperature with other points requiring (supplied) correction factors (depending on the thermocouple) or simply left unchanged so that all points will hv their own correction factors. Purchased TCs which can be reset usually come pre-adjusted to ice temperature. The magnitude of the correction factors will depend on the unit.

Will obviously be of some interest to determine if the oven temperature is uniform ?

Rgds / Charles.C

PS Sorry anish, didn't see yr post. I guess mck can compare ideas.

PPS to mck Welcome to the forum!

Will obviously be of some interest to determine if the oven temperature is uniform ?

Yep, most gas ovens need to be balanced.

Depends on what you're baking, if it's chicken I'd say yes to it being a CCP and I'd measure the temperature using a manual temperature probe calibrated on a minimum weekly basis then calibrate the oven probes minimum yearly (but not rely on them for the CCP control iyswim.)

Are you stating that the core of the item that you are baking has to be to reach a set temperature and therefore safe or are you placing all the control on the oven?
The core temperature is the "control" , not the oven and therefore only the probe that you check the product with needs calibration and certificated.
If the oven is being serviced correctly and you are achieving the correct temperature within the correct time and to the quality required you do not need the oven to be calibrated as this should be checked when the oven is serviced.

I do think that the oven should be on a calibration and service schedule, butI would agree with Ian that time and temperature of the product should be the CCP.

Dear IanR / QLD,

One reason for final setup may be simple logistics, eg operational skill/convenience/generality. I guess it also depends on the scale / magnitude of the process.

I agree that the core parameters are "at the core" but IMEX (not for ovens), usually (ideally?), HACCP prefers a continuous system monitoring methodology. This typically necessitates the use of an "overall" gauge rather than a specific probing (used more as an operational verification.) The problem can get more complicated with a range of sizes in the same lot, etc. Hence calibration and, sometimes, conservatism.

From memory, some US references for chicken also closely define a preferred area of the chicken to be probed. I occasionally wondered how long the home bimetallic units will survive being left in an oven at 100 - 200degC.

Rgds / Charles.C

PS - obviously the microbiological status IN/OUT is somewhat relevant also !!

Hi mck,

The question we have forgotten to ask: what products are being produced?

Meat? Dairy? Bread? Cakes?

Hi! We are currently doing our HACCP Plan. We had identified baking as one of our CCPs but one of our coordinator is insisting that we can omit and that we just have to validate the kill rate(temperature and time) for microorganisms during baking. We did the validation and all our products passed the kill rate and even go beyond it. Our worry now is that we don't have any calibration procedure for our ovens which we think is essential during the certification process. We plan on doing the calibration, thus I am searching for the procedure on how to calibrate the oven. Ours is a rack type of oven. Thanks.