14 replies to this topic

[foodsafetyboy]

Just an out of the blue question:

What is the best way to check / acquire the temperature of a frozen item, especially when there is an equipment breakdown in the cold unit?

what about for frozen bulk items? do you use food contact or non-food contact thermometer?



Regards,
FSB

[KTD]

I have used a small rechargeable drill fitted with a drill bit just smaller in diameter than the body of the probe tip. If you have to go larger than the tip, don't drill as deep, so you have to gently push the last little bit to get to the appropriate depth. Make sure to use a dedicated drill and wash/sanitize the drill bit. If holding a small item, make sure that an unexpected product break of probe push-through does not skewer your hand or fingers - been there...done that.

[foodsafetyboy]

I have used a small rechargeable drill fitted with a drill bit just smaller in diameter than the body of the probe tip. If you have to go larger than the tip, don't drill as deep, so you have to gently push the last little bit to get to the appropriate depth. Make sure to use a dedicated drill and wash/sanitize the drill bit. If holding a small item, make sure that an unexpected product break of probe push-through does not skewer your hand or fingers - been there...done that.

Hi KTD,

Nice one there.
In the previous company (Meat production) I've worked for, we discourage the use of drill for us to prevent risks you have mentioned and there were also instances where a drill was found inside a frozen pork supplied to us by a particular supplier. What we did is to just place the probe in between packets of two frozen items / use non-food contact thermometer (infrared).

regards,
FSB

[onsolution]

I will run through some assumptions and my reasoning on this issue. I sell temperature loggers so most of my "research" is listening to others.

You are talking about a frozen item which is thawing. This means that the inside will be colder than the outside. So the external temperature is more critical than the internal.

Especially on larger items, the risk of part of the item perishing due to partial thawing is highest on the outside.

In the case of a broken freezer, walking in with a thermometer will just confirm the equipment is dead. Measuring the outside will just confirm what you already feel - it's getting warmer. Measuring the inside will confirm that it used to be colder.

But cooling or freezing an item is the exact opposite. The outside will drop in temperature before the middle. So the need to measure the internal temperature is critical but usually neglected.

If your concern is about the item's temperature but the equipment has been repaired and you are investigating hours or days later, then any type of thermometer won't help you. It's the realms of a temperautre logger. Most people will just have a single logger for the freezer which will give a reasonable indicator of the chance of damage.

But I know some people who will place the loggers inside their product. In some case this means piercing or cutting the product (which can make that item unusable) but the compromise of between packed items (as mentioned by FSB) is totally legitimate.

Practically, I would recommend a logger with a probe (and most of the manufacturers offer one) but if you want an incredibly small logger that fits anywhere then I think the Thermocron logger is currently the smallest on the market (about the size of a coin and looks like a coin-cell battery).

So to me it's obvious. You are talking about a process of thawing and potentially refreezing which means a one-off reading isn't of great value. It's the job best done by a logger.

But I would say that, because that's my job.

[onsolution]

Also, just a comment about infrared thermometers.

Great product if used correctly, but many people don't know how to use them correctly.

They are not like lasers taking the temperautre at a specific point. You do not point them at a spot and see the temperature at that spot. It is more like a flash light where the area it covers spreads out.

So imagine shining a flash light from your freezer door into the freezer and having half the room light up. That's what you are measuring the temperature off with the infrared.

Cheaper ones have a much wider spread while the more expensive ones have a narrower beam. The narrower beam allows you to be more selective in what you are measuring (a single item or part of a a larger item) or be further away. But chances are the average user has no idea about this, stands a comfortable distance away and is measuring an item and half a dozen things around it.

They also have the risk of reflection with certain materials.

Like I said, great product if used correctly.

Cheers,
SV

[GMO]

As we have an expert here... I also heard IR thermometers were difficult to calibrate; possibly because of the limitations you've stated? Is this true?

[BarrieT]

There is a special gadget you can buy which enables you to check the IR device against a calibrated probe - a sort of metal cannister where the probe is inserted at the base to read temperature, then you point the IR probe into the cannister and take a reading.

[onsolution]

This possibly highlights the issues involved.

The calibration device is basically a black metal cup. You point the gun in one end and place a thermometer into the base (literally into the base, not through the base) to measure the temperature of the unit.

So you are talking about incredibly short distances, with no outside interference, and into an enclosed space to stop reflection. With all these conditions met you can make a consistent and reliable reading. Consequently you can "calibrate" your IR unit.

But then a pimply gen-Y takes it into the freezer and plays Star Wars shooting it across to the other side. Or it is pointed at the plastic wrapped ice-cream pallet which will reflect or give you the surface temperature of the wrapping.

The standards state that 1° accuracy or better is required within the food industry. This can easily be met by good IR guns, the problem is that the user needs to know their limitations and work within them.

Personally I think they are a great lazy check. It would be great to hear when people are prepared to use them and when they aren't.

And the usual disclosure, I sell temperature loggers. I have previously tried to sell IR sensors but pulled out of the market because of these types of issues.

Cheers,
SV

P.S. No insult was intended towards any pimply Gen-Y. I am sure there are some hardworking ones out there.

[clover]

An off topic : For cold storage temperature readings, what should be the correct way? Is it .... : - 

 

a) Record readings reflected on LED panel of temperature display OR;

b) Use an IR thermometer to record temperature readings

[Charles.C]

An off topic : For cold storage temperature readings, what should be the correct way? Is it .... : - 

 

a) Record readings reflected on LED panel of temperature display OR;

b) Use an IR thermometer to record temperature readings

 

Product ? Air ? location ? Instrument ?

[clover]

Product ? Air ? location ? Instrument ?

 

Hi Charles, 

 

as I've mentioned the temperature reading is for cold storage (chiller, freezer) storing raw food and cooked food respectively. So, I'm just wondering if it's acceptable or okay to have them just read the temperature readings from the display panel located outside the chiller,freezer or must they actually use a IR thermometer to measure and take the temperature readings of chiller, freezer? 

[Charles.C]

Hi Clover,

 

I think it partly depends on what you mean by cold room (CR) "temperature", or freezer temperature, etc.

 

The display outside  a CR (<= -18degC)  is usually monitoring air temperature, sometimes via TC, sometimes bimetallic.

 

The display outside a plate freezer typically monitors refrigerant temperature (I think).

 

The display outside an air-blast freezer typically measures air temperature similar to the CR.

 

CR  product temperature is typically estimated by putting a TC between 2 tightly adjacent food containers. Reason is non-invasive and reasonably well-validated (Codex).

 

I've never used an  IRT but i believe it measures surface temperatures only, like walls, ceilings, ice, outside of cartons. If so, i guess it does not exactly measure any of the above characteristics. I get the impression that IRT's are less accurate than TCs but no data either way.

 

IMEX the reliability of CR displays is usually checked by portable TCs.

 

Perhaps any IRT users here would like to comment.

[clover]

Hi Clover,

 

I think it partly depends on what you mean by cold room (CR) "temperature", or freezer temperature, etc.

 

The display outside  a CR (<= -18degC)  is usually monitoring air temperature, sometimes via TC, sometimes bimetallic.

 

The display outside a plate freezer typically monitors refrigerant temperature (I think).

 

The display outside an air-blast freezer typically measures air temperature similar to the CR.

 

CR  product temperature is typically estimated by putting a TC between 2 tightly adjacent food containers. Reason is non-invasive and reasonably well-validated (Codex).

 

I've never used an  IRT but i believe it measures surface temperatures only, like walls, ceilings, ice, outside of cartons. If so, i guess it does not exactly measure any of the above characteristics. I get the impression that IRT's are less accurate than TCs but no data either way.

 

IMEX the reliability of CR displays is usually checked by portable TCs.

 

Perhaps any IRT users here would like to comment.

What's TC? Probe thermometer ? 

I believe the panel displays monitoring the air temperature as I've used the IRT and randomly shoot at the "fan" area where blows out cold wind inside chiller/freezer and it gave a close reading to that displayed on the temperature reading panel outside the chiller/freezer..

 

Same question for monitoring truck temperature. Can the temperature readings be taken from the display panel located at the drivers' seat? 

[clover]

I guess my main question is can the temperature readings be taken from the display panels INSTEAD OF the temperature measured & recorded using a thermometer? 

[Charles.C]

Hi clover,

 

Sorry, TC = thermocouple

 

Yr questions IMO are all related to the specific characteristic required to be measured.

For example, MEX is with containers of frozen goods. These all have a temp.readout chart on outside but it is never regarded as a valid measure of the product temperature.

However it does show that the air temperatue in the container has been properly maintained below the target limit, ie no refrigeration system failure.

 

So if yr post had stated "can the display temperature be taken as a measure of the temperature of the product" my answer would be NO.

 

The fixed probe generating the display reading is ideally placed at the warmest reprentative point in the room, definitely not in front of the fan.

 

I'm unsure what the IRT is actually measuring, case of fan temperature maybe ?