Dear colleagues,
In the USA you do not have the problem to find an appropriate supplier of
temperature monitoring, recording or control, but just the opposite, the
problem is to select among a very large number of companies and solutions. To
find most of the possibilities you have at hand, you can for instance explore
the ThomasNet web page, a site that consolidate (I guess) most of the
suppliers of this type of monitoring/ recording and control industry devices
(a very useful page):
http://www.thomasnet.com/nsearch.html?cov=NA&which=prod&what=Recorders%3A+Tem
perature&heading=66430208&pos=2&next=25
A number of that companies provide some technical support, and some companies
have "Food control departments" or similar, that can assist you.
After saying that it would be better to clarify that selection of equipment
could be no so straightforward as it could seem. Temperature measurement
equipment for control purposes are broadly of two types; for automatic
control and for manual control. It could be that you read food temperature
with the purpose, for instance, to control quality and economics (e.g.
quality, cooking losses), but most of the time if you read temperature it
would be for safety purposes (particularly when linked to a CCP in a HACCP
system).
Manual control happens when a human operator after reading a strip chart or a
computer screen, or be alerted by a sound or light signal (attached to the
reading/ recording system) acts in the way to correct the deviation in
temperature detected. Automatic control happens when the action is taken
automatically (in a programmed way) by a mechanical (or electronic or
pneumatic) "controller" that receives the signal of the T lecture
continuously (or in a continued way; in which case the last lecture is taken
as the "true" temperature until the new temperature measurement arrives).
We have a number of these systems in our processing plants even if very often
we do not realize that. For instance the system for temperature control in
modern shrimp cookers is one of them; plate freezers also contains
temperature controllers, the same cold storage rooms. More sophisticated
temperature controllers are installed in modern can sterilizers, driers and
cookers.
Time is a very important variable in measurement (and of course control). The
reason is that under continuous/ or continued operations of utmost importance
are the dynamics of the process and measurement equipments utilized to detect
relevant changes (that deserve/ require correction) in the process. Some
processes (e.g. shrimp cooking) have a quick dynamic (very few seconds)
whereas others like cold storage rooms have a slow dynamics (hours); others
like freezing (or thawing), drying and smoking are in-between (depending on a
number of technical aspects).
For a cold storage room usually we could utilize a heavy duty (slow dynamic)
measurement device, because the frozen mass inside the cold storage room has
an appreciable "thermal inertia" and therefore the thermometer will detect
changes well before they will really affect the frozen fish. If we choose a
very sensible device (quick dynamic) and place it near the cold storage door
(the most critical place to detect increases in temperature inside the cold
storage room) we are going to have a saw-like records, every time the door is
open the record will drop (perhaps well below it has to be according the
HACCP plan) and will go up immediately down once the door is closed. Of
course if we have cold air or plastic curtains and/ or pre-chambers before
the cold-storage room then the effect will be less noticeable.
The problem here is that temperature measurements are not related to the
temperature at the surface of the mass of frozen fish (that is our true
objective) but to the temperature of the air at the door place (or where we
placed the sensible part of the measuring device). If we measure the
temperature at the surface of the frozen fish (actually at the surface of
cartons and masters or just packaging), e.g. with a radiation thermometer, we
are going to see that such a temperature did not changed appreciable during a
single opening of the door.
Probably if the cold storage room is well designed and operated, most of the
normal "perturbations" entering the cold storage room, will leave unaffected
the temperature of the frozen fish. Large deviations (e.g. increase in
temperature, in all the cold storage room, above minus 18 degree C will be
noticed well in advance. A saw-like record will give only the wrong idea that
things are not working well and perhaps masking when the true problem could
arrive.
We can take an opposed example with shrimp cooking, here the dynamics is very
quick and we need a instrument with a very quick dynamic (quicker than the
shrimp cooking process). Shrimp has usually a very short residence time in
shrimp cookers (either working with steam or with water baths); therefore
relatively small fluctuations of temperature in the cooking media could have
a relevant impact on the shrimp safety (also on quality and yield).
It does not make sense to think that we are going to measure the temperature
inside the individual shrimp (*); we are going to measure, for instance, the
temperature of the steam in the cooking chamber. A nude thermocouple may do
the job. If we have a steam cooker, probably it will be a steam pressure
system to assure the right temperature in the steam. There may be "hick-ups"
in the steam line (depending on what the plant is doing with steam) which in
turn could introduce noticeable perturbations in the cooking chamber. How to
control in this case is another thing, and will depend on the type of
deviation; deviations in the sense of an increase of temperature will not
have an effect on shrimp safety (they may have effects in terms of quality
and yield); deviations in the sense of a drop in temperature could have a
impact on safety (control of L. monocytogenes in ready-to-eat foods).
Residence times are normally adjusted, adding some "safety time", this means
that usually shrimp will stay longer in the cooker than the minimum time at a
given temperature, to be considered "safe" from a regulatory point of view.
If deviation is covered by the "safety time", then there is no problem; but
if it is not, the shrimp processed during the time of the "perturbation"
should be, for instance, segregated and re-processed appropriately as soon as
possible. Control is exerted, in this case, through the "corrective actions"
, according to the HACCP plan.
It is very important to realise that despite the existence of an automatic
control (e.g. on temperature); the final objective is the safety of the
product, and this may be not achieved, just by the action of the automatic
control. Some years ago when I was assisting in the introduction of HACCP in
the fishery industry of developing countries, we found, for instance, in some
cases industries that kept the records of the temperature at the shrimp
cookers, and when we performed mock HACCP audits, and asked what happened
with the shrimp at the time of large deviations of temperature, they look at
us and say: "Nothing, this is an automatic system!". Of course the automatic
system restored the temperature (not instantaneously), but what about the
shrimp under processed?
It looks a bit no sense, but the "red light" device at the corner in the
street is an automatic device too, nevertheless, we look right and left
before to cross, even if the light is green.
This two different examples is just to say that there is a bit more than just
to select an equipment to monitor temperature. We should be sure about what
we really want to measure (most of our measurements are indirect, sometimes
two or more times indirect) and how is the chain till control (e.g
implementation of the HACCP plan in practice). To have a continuous or
continued measurement could be important or not, it will depend on the
dynamics of the process and measurement equipment. Which is important is to
have a clear idea for what it is necessary to monitor, and which are going to
be our "corrective actions" when necessary.
I take the opportunity to say again that all these things are the
responsibility of the industry, not of inspection services. Not only because
HACCP regulations say that, if not because all the actual alternatives are
very difficult to figure out. HACCP turns into the industry the
responsibility to know more about its own processes than any other else
(including inspection services). HACCP is basically more knowledge.
Automatic controls are going into the fishery industry (and all the food
industry) and they are becoming more and more important. They are
particularly important in developed countries, but the use of automatic
controls is spreading to developing countries too. Robots seem to be more
reliable than humans (not necessarily always); but definitely we can not get
rid of human thinking (yet?). In any case, to think in terms of automatic
control is a very good exercise to analyze how a plant, line or equipment
should be operated for safety (particularly at CCPs), in all details, even if
we are going to operate the plant manually anyway.
Kind regards.
Hector M. Lupin
FAO Consultant
(*) Verification measurements (to check if what are we reading and what we
are achieving, e.g. in the shrimp) and calibrations will be always necessary.
In the case of quick dynamic systems probably the verification of the "time
constant" (the proper technical expression, to identify the dynamic
characteristic of a system) of the measuring device, would be necessary in
systems where the media can create fouling on the surface of the measuring
sensible device (e.g. in shrimp cooking baths). Fouling (and dirtiness in
general) would make the "answer" of the measuring device slower than if the
surface be clean.
-----Original Message-----
From: owner-seafood@ucdavis.edu [mailto:owner-seafood@ucdavis.edu] On
Behalf Of Rippen, Thomas E.
Sent: 01 November 2006 22:11
To: Enrique Reinoso Pin; Strang, Mike; HACCP mailing list (HACCP
mailing list)
Subject: RE: continuous monitoring
Mike and Enrique,
It really comes down to how short of a recording time interval will
satisfy the "continuous" monitoring expectation of FDA. The agency generally
accepts datalogging instrumentation which record at preset intervals
(hopefully, appropriate for the process) and are not truly continuous. These
devices would appear to remove the human element but a distinction should be
made between continuous monitoring and continuous record-keeping. Even a
cook recorded by an ink-on-paper continuous chart must be periodically
monitored by the operator. If, by nature of the process, the smokehouse
operator must check every five minutes to determine the end of cook (product
endpoint temperature), then an argument can be made that any record verifying
this activity, or even just the final endpoint temperature, should satisfy
the record-keeping requirement of the HACCP regulation. The record must
document that critical limits are met, or if not, that appropriate corrective
actions are taken. Nothing in the regulation mandates the use of continuous
record-keeping devices to satisfy this requirement. Someone from FDA, care
to weigh in?
Tom
Thomas E. Rippen
Seafood Technology Specialist
Sea Grant Extension Program
Center for Food Science and Technology
University of Maryland Eastern Shore
Princess Anne, MD 21853
410-651-6636
410-651-8498 fax
terippen@umes.edu
-----Original Message-----
From: owner-seafood@ucdavis.edu [mailto:owner-seafood@ucdavis.edu] On
Behalf Of Enrique Reinoso Pin
Sent: Wednesday, November 01, 2006 2:42 PM
To: Strang, Mike; HACCP mailing list (HACCP mailing list)
Subject: Re: continuous monitoring
Mike
If you monitoring every time it is continuos. If you monitouring
every 5 minutes it is imtermitent.
Enrique Reinoso
enriquereinoso@hotmail.com
----- Original Message -----
From: Strang, Mike <mailto:Mike.Strang@us.fjordseafood.com>
To: HACCP mailing list (HACCP mailing list)
<mailto:seafood@ucdavis.edu>
Sent: Wednesday, November 01, 2006 2:11 PM
Subject: continuous monitoring
Another question concerning continuous temperature
monitoring.
We are monitoring internal fillet temperatures during a cook.
We probe 3 of the thickest fillets with thermocouple probes, we read and
record the fillet temperature every 5 minutes during the cook once all of the
3 fillets have reached the critical temperature.
Why would this not be considered continuous monitoring?
Mike Strang, QC Manager
Ducktrap River of Maine
57 Little River Drive
Belfast, Maine 04915
mike.strang@us.fjordseafood.com
Ph: 800-508-7968
Fax: 207-338-6288
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