Chapter 6: Refrigerated Fish and Fishery Products

Updated 9/21/00

Contents

Potential Food Safety Hazard

Pathogen growth and toxin formation as a result of time/temperature abuse of fish and fishery products can cause consumer illness. This hazard is limited to bacterial pathogens since viral pathogens (viruses) are not able to grow in food. Temperature abuse occurs when product is allowed to remain at temperatures favorable to pathogen growth for sufficient time to result in unsafe levels of pathogens or their toxins in the product. Chapters 10-21 provide guidance about the conditions under which certain pathogens are able to grow. The pathogens listed are those of greatest concern in fish and fishery products (FDA, 1998b).

1. Raw fish and fishery products to be cooked before consumption

    Pathogens can enter the process on raw materials. They can also be introduced into foods during processing from the air, unclean hands, insanitary utensils and equipment, unsafe water, sewage, and through cross-contamination (FDA, 1998b).

2. Raw fish that is intended to be eaten raw

    Pathogens can enter the process on raw materials. They can also be introduced into foods during processing from the air, unclean hands, insanitary utensils and equipment, unsafe water, sewage, and through cross-contamination (FDA, 1998b).

3. Raw molluscan shellfish that may be eaten raw

Pathogens found in waters from which molluscan shellfish are harvested can cause disease in consumers. Molluscan shellfish include 1) oysters; 2) clams; 3) mussels; and, 4) scallops, except where the final product is the shucked adductor muscle only. The pathogens of concern include both bacteria and viruses.

Pathogens from the harvest area are of particular concern in molluscan shellfish because: 1) environments in which molluscan shellfish grow are commonly subject to contamination from sewage, which may contain pathogens, and to naturally occurring bacteria, which may also be pathogens; 2) molluscan shellfish filter and concentrate pathogens that may be present in surrounding waters; and, 3) molluscan shellfish are often consumed whole, either raw or partially cooked (FDA, 1998i).

4. Fish and fishery products sensitive to scombrotoxin (histamine) formation

Scombrotoxin formation as a result of time/ temperature abuse of certain species of fish can cause consumer illness. The illness is most closely linked to the development of histamine in these fish. In most cases histamine levels in illness-causing fish have been above 200 ppm, often above 500 ppm. However, there is some evidence that other chemicals (e.g., biogenic amines, such as putrescine and cadaverine) may also play a role in the illness.

Scombroid poisonings have primarily been associated with the consumption of tuna, mahi mahi, and bluefish. However, FDA's Hazards and Controls Guide, Chapter 3, Table 3-1 (FDA, 1998n) lists a number of species that are also capable of developing elevated levels of histamine when temperature abused.

Certain bacteria produce the enzyme histidine decarboxylase during growth. This enzyme reacts with free histidine, a naturally occurring chemical that is present in larger quantities in some fish than in others. The result is the formation of histamine.

Histamine-forming bacteria are capable of growing and producing histamine over a wide temperature range. Growth is more rapid, however, at high-abuse temperatures (e.g., 21.1ºC (70°F) than at moderate-abuse temperatures (e.g., 7.2ºC [45°F]). Growth is particularly rapid at temperatures near 32.2ºC (90°F). Histamine is more commonly the result of high temperature spoilage than of long term, relatively low temperature spoilage. Nonetheless, there are a number of opportunities for histamine to form under more moderate conditions.

Once the enzyme histidine decarboxylase has been formed, it can continue to produce histamine in the fish even if the bacteria are not active. The enzyme can be active at or near refrigeration temperatures. The enzyme is likely to be more stable than the bacteria in the frozen state and may be reactivated very rapidly after thawing. Recent studies suggest that if histamine production is advanced (i.e., high levels of histidine decarboxylase), histamine formation can continue even in frozen storage.

Freezing for an extended period of time (e.g., 24 weeks) may inactivate the enzyme-forming bacteria. Cooking can inactivate both the enzyme and the bacteria. However, once the toxin is formed, it cannot be eliminated by heat (including retorting) or freezing. After cooking, recontamination of the fish with the enzyme-forming bacteria is necessary for additional histamine to form. For these reasons, histamine development is more likely in raw, unfrozen fish.

The kinds of bacteria that are associated with histamine development are commonly present in the salt-water environment. They naturally exist on the gills and in the gut of live fish, with no harm to the fish. Upon death, the defense mechanisms of the fish no longer inhibit bacterial growth, and histamine-forming bacteria start to grow and produce histamine. With some harvesting practices, such as longlining, death can occur before the fish is removed from the water. Under the worst conditions histamine formation can already be underway before the fish is landed on the vessel. This condition can be aggravated when the fish is allowed to struggle on the line for a period of time, a situation that in certain tuna species may cause its internal temperature to increase to a more favorable growth range for the enzyme-forming bacteria.

The potential for histamine formation is increased when the flesh of the fish is directly exposed to the enzyme-forming bacteria. This occurs when the fish are processed (e.g., butchering or filleting) (FDA, 1998h).

5. Acidified (pickled), fermented, salted, and smoked fish and fishery products

Pathogens can enter the process on raw materials. They can also be introduced into foods during processing from the air, unclean hands, insanitary utensils and equipment, unsafe water, sewage, and through cross-contamination (FDA, 1998b). Pathogen growth can occur if the % salt, water activity, water-phase salt, pH, and/or level of preservatives are not adequate.

6. Cooked fish and fishery products

Pathogens can enter the process on raw materials. They can also be introduced into foods during processing from the air, unclean hands, insanitary utensils and equipment, unsafe water, sewage, and through cross-contamination from raw to cooked products (FDA, 1998b).

Proper cooking kills most pathogens, but cross-contamination, vacuum packaging and time/temperature abuse can result in pathogen growth and, possibly, toxin production.

Contents

Control Measures

1. Raw fish and fishery products to be cooked before consumption

For many products (e.g., raw fish fillets) there is no cooking, pasteurizing, or retorting step performed by the processor. For most of these products, the consumer or end user cooks the product before consumption (FDA, 1998i).

Normal cooking procedures (e.g., heating all parts of the food to 63ºC (145ºF) or above for 15 s (FDA, 1997a)), will kill most pathogens.

2. Raw fish that is intended to be eaten raw

For fish and fishery products intended to be eaten raw, there is no cooking, pasteurizing, or retorting step performed by the processor or the consumer. HACCP controls are necessary to prevent time-temperature abuse that could result in pathogen growth during receiving, processing, and storage.

3. Raw molluscan shellfish that may be eaten raw

To minimize the risk of molluscan shellfish containing pathogens of sewage origin, State and foreign government agencies, called Shellfish Control Authorities, classify waters in which molluscan shellfish are found, based, in part, on an assessment of water quality. As a result of these classifications, molluscan shellfish harvesting is allowed from some waters, not from others, and only at certain times or under certain conditions from others. Shellfish Control Authorities then exercise control over the molluscan shellfish harvesters to ensure that harvesting takes place only when and where it has been permitted.

Significant elements of Shellfish Control Authorities' efforts to control the harvesting of molluscan shellfish include: 1) a requirement that containers of in-shell molluscan shellfish (shellstock) bear a tag that identifies the type and quantity of shellfish, harvester, harvest location, and date of harvest; 2) a requirement that molluscan shellfish harvesters be licensed; 3) a requirement that processors that shuck molluscan shellfish or ship, reship, or repack the product be certified; and, 4) a requirement that containers of shucked molluscan shellfish bear a label with the processor's name, address, and certification number.

These controls serve to minimize the risk of molluscan shellfish containing pathogens of sewage origin, but do not fully eliminate the risk. As a result, consumption of raw molluscan shellfish may not be safe for individuals with certain health conditions, such as liver disease, chronic alcohol abuse, diabetes, and stomach, blood, and immune disorders. For this reason Shellfish Control Authorities require that shellstock bear a tag that instructs retailers to inform their customers that cooking reduces the risk of food-borne illness, and that individuals with these health conditions are at higher risk of illness if they consume the product raw.

Processors can also eliminate the hazard of "pathogens from the harvest area" by properly cooking or retorting the product. Guidance on cooking controls is provided in Chapter 3. Mandatory retorting controls are described in the low-acid canned foods regulation (21 CFR 113). It should be noted that neither cooking nor retorting will eliminate the hazards of "natural toxins" or "chemical contamination" that may be associated with molluscan shellfish that are harvested from closed waters (see Chapters 23 and 26). Additionally, the laws and regulations of states that participate in the National Shellfish Sanitation Program currently require that all molluscan shellfish be harvested from waters approved for harvesting by the Shellfish Control Authority, regardless of how it will be processed.

Pathogens, such as V. parahaemolyticus, V. cholerae, and L. monocytogenes that may be present in low numbers at the time that molluscan shellfish are harvested, may increase to more hazardous levels if they are exposed to time/temperature abuse. To minimize the risk of pathogen growth, Shellfish Control Authorities place limits on the time between harvest and refrigeration. The length of time is dependent upon either the month of the year or the average monthly maximum air temperature (AMMAT) at the time of harvest, which is determined by the Shellfish Control Authority.

Additionally, to minimize the risk of illness from the consumption of molluscan shellfish containing V. vulnificus, Shellfish Control Authorities place certain controls on the harvest of molluscan shellfish harvested from waters which have been associated with V. vulnificus infection. V. vulnificus is a naturally occurring bacterial pathogen that is frequently associated with the consumption of raw oysters harvested from the Gulf of Mexico during the warm weather months. The controls for V. vulnificus discussed in this chapter only apply to such molluscan shellfish if they are intended for raw consumption. For example, they would not be applied to oyster shellstock from the Gulf of Mexico if tags on the containers of shellstock indicate that they must be shucked and cooked before consumption.

In most cases, control for V. vulnificus involves limits on the time from harvest to refrigeration. The length of time is dependent upon the average monthly maximum water temperature (AMMWT) at the time of harvest, which is determined by the Shellfish Control Authority. This is an interim control measure, which is contained in the National Shellfish Sanitation Program Manual of Operations. FDA and the Interstate Shellfish Sanitation Conference (ISSC) plan to re-evaluate the effectiveness of this control measure.

As with pathogens of sewage origin, the above controls for naturally occurring pathogens, such as V. vulnificus and V. parahaemolyticus, minimize the risk of molluscan shellfish containing these pathogens, but do not fully eliminate the risk. For this same reason, Shellfish Control Authorities require that shellstock bear a tag containing a warning relative to raw consumption (described above).

Cooking, pasteurizing, and retorting can also eliminate V. vulnificus. Guidance for these control mechanisms can be found in Chapters 3 (cooking) and 5 (pasteurization) and the low-acid canned foods regulation (21 CFR 113) (FDA, 1998i).

4. Fish and fishery products sensitive to scombrotoxin (histamine) formation

Rapid chilling of fish immediately after death is the most important element in any strategy for preventing the formation of scombrotoxin. For fish other than tuna above 20 lbs., if the fish have not been exposed to water temperatures above 28.3ºC (83°F), the fish should be placed in refrigerated seawater or brine at 10ºC (50°F) or less within 9 h of death, or placed in ice within 12 h of death. For tuna above 20 lbs., or if the fish have been exposed to water temperatures above 28.3ºC (83°F), the internal temperature of the fish should be brought to 10ºC (50°F) or less within 6 h of death. This will prevent the rapid formation of the enzyme histidine decarboxylase. Once this enzyme is formed control of the hazard is unlikely.

Further chilling towards the freezing point is also desirable to safeguard against longer-term, low-temperature development of histamine. Additionally, the shelf life of the fish is significantly compromised when product temperature is not rapidly dropped to near freezing.

The time required to lower the internal temperature of fish after capture will be dependent upon a number of factors, including:

 Once chilled, the fish should be maintained as close as possible to the freezing point (or held frozen) until it is consumed. Exposure to ambient temperature should be minimized. The allowable exposure time is dependent primarily upon the speed with which the fish were chilled on-board the harvest vessel and whether the fish has been previously frozen (e.g., on-board the harvest vessel).

Unfrozen scombrotoxin-forming fish has a safe shelf life, which is dependent upon the storage temperature. Table 6-1 shows an approximate safe shelf life for fish stored at various temperatures. The safe shelf-life periods in the table include the time aboard the harvest vessel.

Any time above 4.4ºC (40°F) significantly reduces the expected safe shelf life. For this reason, fish should not be exposed to temperatures above 4.4ºC (40°F) for more than 4 h, cumulatively, after chilling on board the harvest vessel. The safety of this limit is dependent upon proper handling at sea.

Fish that have been handled particularly well on-board the harvest vessel may be able to safely withstand somewhat more exposure to elevated temperatures during post-harvest handling.

 Table 6-1. Approximate safe shelf life for scombrotoxin-forming species at various storage temperatures (FDA, 1998h).
 
Product Temperature
Safe Shelf-life (d) with Rapid Cooling
Safe Shelf-life (d) with Delayed Cooling
ºC
ºF
-17.8  0
No limit
No limit
0 32 14 8
3.3 38 10 7
4.4 40 7 5
10 50 3 0
21.1 70 0 0
32.2 90 0 0
Fish that have undergone extended frozen storage (e.g., 24 weeks) can safely withstand considerably more exposure to elevated temperatures during post-harvest handling. Such fish should not be exposed to temperatures above 4.4ºC (40°F) for more than 12 h, cumulatively, after chilling on board the harvest vessel. An uninterrupted period of exposure should not exceed 6 h. Intermittent refrigeration breaks the cycle of rapid bacterial growth and slows the formation of histamine. The safety of these limits is again dependent upon proper handling at sea.

Extended frozen storage (e.g., 24 weeks) or cooking minimizes the risk of additional histamine development by inactivating the enzyme-forming bacteria and, in the case of cooking, the enzyme itself. As previously mentioned, recontamination with enzyme-forming bacteria and significant temperature abuse is necessary for histamine formation under these conditions. Such recontamination may not be likely if the fish is processed under a conscientious sanitation program (FDA, 1998h).

5. Acidified (pickled), fermented, salted, and smoked fish and fishery products

Hazards from C. botulinum can be controlled by inhibiting growth of the bacteria or by destroying it in seafood. Proper thermal processes for canned seafood destroy the bacteria. Heavy salting or drying to reduce the water activity below 0.93 and fermentation or acidification to below pH 4.7 are effective means of preventing C. botulinum growth. Maintaining proper storage temperatures alone is not considered an adequate control measure for C. botulinum Type E because of its ability to grow at low temperatures and because of the severity of the illness. Nonetheless, in many products, it is an important second barrier to growth (Ward et al., 1997).

6. Cooked fish and fishery products

Generally, after cooking, fishery products are referred to as cooked, ready-to-eat. Examples of cooked, ready-to-eat products are: crabmeat, lobster meat, crayfish meat, cooked shrimp, surimi-based analog products, seafood salads, and hot-smoked fish.

Controlling pathogen survival through the cook step is accomplished by:

A thorough hazard analysis is important when evaluating a thermal process. In some cases, a cooking or heating step will not present a potential health hazard even if it is sublethal to pathogens. Examples include a blanching step to inactivate enzymes and a par-fry operation to set the breading on products to be fully cooked by the consumer (Rippen, 1998).

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FDA Guidelines

1. Raw fish and fishery products to be cooked before consumption

FDA is not aware of any HACCP controls that may exist internationally for the control of pathogens in fish and fishery products that are intended to be fully cooked by the consumer or end user before consumption, other than a rigorous sanitation regime as part of either a prerequisite program or as part of HACCP itself. The Seafood HACCP Regulation requires such a regime. The proper application of sanitation controls is essential because of the likelihood that any pathogens that may be present in seafood products are introduced through poor handling practices (e.g., by the aquacultural producer, the fisherman, or the processor) (FDA, 1998i).

Processing battered fish and fishery products:

  • Hydrated batter mix temperatures should not exceed 10ºC (50°F) for more than 12 h, cumulatively; and
  • Hydrated batter mix temperatures should not exceed 21.1ºC (70°F) for more than 3 h, cumulatively (FDA, 1998c).
    •

    2. Raw fish that is intended to be eaten raw

    Receiving:

    3. Raw molluscan shellfish that may be eaten raw

    Shellstock temperature control:

    The NSSP approves the following options for shellfish temperature control before delivery (ISSC, 1997): Table 6-2. Option 1 for receiving live shellfish (Mandatory for confirmed V. vulnificus problem) (ISSC, 1997).
    Water Temperature
    Time to
    Refrigeration
    November through March
    Options 2 or 3
    18.3-23.3ºC (65-74ºF)
    14 h
    23.9-28.9ºC (75-84ºF)
    12 h
    >28.9ºC (84ºF)
    10 h

    Table 6-3. Option 2 for receiving live shellfish (ISSC, 1997).
    Months
    Time to
    Refrigeration
    April through November
    20 h
    December through March
    36 h

    Table 6-4. Option 3 for receiving live shellfish (ISSC, 1997).
    Average monthly
    Maximum air
    Temperature
    Maximum h from harvest to
    temperature control
    >27ºC (81ºF)
    20
    19-27ºC (66-80ºF)
    24
    11-18ºC (51-65ºF)
    36
    <10ºC (50ºF)
    48

    Shellstock transportation:

    Shellstock shall be transported in adequately refrigerated trucks when the shellstock have been previously refrigerated or when ambient air temperature and time of travel are such that unacceptable bacterial growth or deterioration may occur.

    Prechilling trucks or other vehicles shall be required when ambient air temperatures are such that unacceptable bacterial growth or deterioration may occur.

    When mechanical refrigeration units are used, the units shall be:

     When mechanical refrigeration units are used, the units shall be equipped with automatic controls and shall be capable of maintaining the ambient air in the storage area at temperatures of 45ºF (7.2ºC) or less.

    The dealer shall not be required to provide thermal recorders during shipment.

    Lack of ice or other acceptable types of refrigeration shall be considered an unsatisfactory shipping condition.

    Shellstock shipping time of greater than 4 h:

    When the shipping time is greater than four h, the dealer shall ship all shellfish in:     Unless the dealer has an approved HACCP plan with an alternate means of monitoring time-temperature, the initial dealer shall assure that a suitable time-temperature recording device accompanies each shipment of shellfish.

    The initial dealer shall note the date and time on the temperature indicating device, if appropriate.

    Each receiving dealer shall write the date and time on the temperature indicating device, if appropriate, when the shipment is received and the doors of the conveyance or the containers are opened.

    The final receiving dealer shall keep the time-temperature recording chart or other record of time and temperature in his files and shall make it available to the Authority upon request.

    An inoperative temperature indicating device shall be considered as no recording device (ISSC, 1997).

    Receiving:

    Shellfish shipments shall be considered acceptable when:

    4. Fish and fishery products sensitive to scombrotoxin (histamine) formation

    Receiving by primary (first) processor:

    Option 1

    Harvest vessel records that accompany all lots received show:

    5. Acidified (pickled), fermented, salted, and smoked fish and fishery products

    Note: Fish and fishery products with a pH of 4.6 or below, a water phase salt level of at least 10%, or a water activity of 0.85 or below do not require refrigeration (FDA, 1998a).

    Receiving for storage or further processing:

  • The product must not be exposed during transportation to temperatures above 10ºC (50°F), which may be assured by:
  • A maximum refrigerated container temperature of 10ºC (50°F) throughout transit; or
  • The presence of sufficient cooling media (e.g., adequate ice to completely surround the product) upon receipt (FDA, 1998a).
    •

    Processing:

  • "Pickled," smoked, smoke-flavored, or salted fish and fishery products must not be exposed to temperatures above 10ºC (50°F) for more than 12 h nor to temperatures above 21.1ºC (70°F) for more than 4 h, excluding time above 60ºC (140°F) (FDA, 1998a).
    •

    Storage:

  • The product must not be exposed to temperatures above 10ºC (50ºF), which may be assured by:
  • A maximum cooler temperature of 10ºC (50°F); and/or
  • The presence of sufficient cooling media (e.g., adequate ice to completely surround the product) (FDA, 1998b).
    •

    6. Cooked fish and fishery products

    Receiving:

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    Critical Aspects of Processes

    Critical aspects of processes may include:

    1. Raw fish and fishery products to be cooked before consumption

    2. Raw fish that is intended to be eaten raw

    Receiving:

    3. Raw molluscan shellfish that may be eaten raw

    Receiving:

    4. Fish and fishery products sensitive to scombrotoxin (histamine) formation

    Receiving by primary (first) processor (option 1):

    Harvest vessel records for the following information:

    5. Acidified (pickled), fermented, salted, and smoked fish and fishery products

    Processing and Packaging:

    6. Cooked fish and fishery products

    Receiving of products to be stored, or processed without further cooking:

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    Labeling Guidelines

    Group A foods

    Group A foods are potentially hazardous foods, which, if subjected to temperature abuse, will support the growth of infectious or toxigenic microorganisms that may be present. Outgrowth of these microorganisms would render the food unsafe. Foods that must be refrigerated for food safety possess the following characteristics: (1) Product pH > 4.6; (2) water activity aw > 0.85; (3) do not receive a thermal process or other treatment in the final package that is adequate to destroy food-borne pathogens that can grow under conditions of temperature abuse during storage and distribution; and (4) have no barriers (e.g., preservatives such as benzoates, salt, acidification), built into the product formulation that prevent the growth of food-borne pathogens that can grow under conditions of temperature abuse during storage and distribution.

    The appropriate label statement for Group A foods is:

    IMPORTANT
    Must Be Kept Refrigerated To Maintain Safety

     Group B foods

    Group B includes those foods that are shelf-stable as a result of processing, but once opened, the unused portion is potentially hazardous unless refrigerated. These foods possess the following characteristics: (1) Product pH > 4.6; (2) water activity aw > 0.85; (3) receive a thermal process or other treatment that is adequate to destroy or inactivate food-borne pathogens in the unopened package, but after opening, surviving or contaminating microorganisms can grow and render the product unsafe; and (4) have no barriers (for example, preservatives such as benzoates, salt, acidification) built into the product formulation to prevent the growth of food-borne pathogens after opening and subsequent storage under temperature abuse conditions.

    The appropriate label statement for Group B foods is:

    IMPORTANT
    Must Be Refrigerated After Opening
    To Maintain Safety

    Group C foods

    Group C are those foods that do not pose a safety hazard even after opening if temperature abused, but that may experience a more rapid deterioration in quality over time if not refrigerated. The manufacturer determines whether to include on the label a statement that refrigeration is needed to maintain the quality characteristics of the product to maximize acceptance by the consumer. These foods do not pose a safety problem. Foods in this group possess one or more of the following characteristics to ensure that the food does not present a hazard if temperature abused: (1) Product pH £ 4.6 to inhibit the outgrowth and toxin production of C. botulinum; or (2) water activity aw £ 0.85; or (3) have barriers built into the formulation (for example, preservative systems such as benzoates, salt, acidification) to prevent the growth of food-borne pathogens if the product is temperature abused.

    The suggested optional label statement for Group C foods is:

    Refrigerate for Quality

    or some other statement that explains to the consumer that the storage conditions are recommended to protect the quality of the product. To avoid confusion between refrigeration for safety purposes and refrigeration for quality reasons, Group A and Group B statements should not be used on Group C foods (FDA, 1997d).

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    Temperature Measurement

    Contents

    Thermometers

    Liquid-in-glass thermometer

    The liquid-in-glass is made of a glass tube with a bulb on one end. On the tube are Fahrenheit or Celsius measurement marks. The glass bulb is filled with either mercury or spirits (alcohol, kerosene, xylene and pentane, etc.). When the temperature around it changes, the liquid in the bulb and tube either expands or contracts. If it is hotter, it will expand. This causes the liquid to rise in the tube. If it is cooler, it will contract. This causes the liquid to fall back down the glass tube. On both the Fahrenheit and Celsius scales, hotter is higher and cooler is lower (Anonymous, 1999).

    Some liquid-in glass thermometers are NIST certified thermometers or thermometers calibrated to NIST-traceable standards.

    Electrical resistance thermometer

    This thermometer does not actually measure temperature, but resistance in a platinum or nickel wire, whose resistance changes as temperature changes. An electrical meter measures the changes in resistance which is related to temperature using a technique called calibration. In order to use calibration, you must determine in advance exactly how the resistance of various metals vary with changes in temperature (Ruscher and Lusher, 1999).

    Thermistor thermometer

    Thermistors are electrical resistance thermometers which use ceramic materials whose resistance increases as temperature increases (Ruscher and Lusher, 1999).

    Thermocouple thermometer

    The thermocouple works on the principle that a metal will react to temperature changes by affecting the amount of electrical current which flows through it. If two different metals are connected, then their response to temperature changes will be different. By measuring the change in an electrical current which passes across these two metals, the actual temperature can be determined using calibration (Ruscher and Lusher, 1999).

    Radiometer thermometer

    This type of thermometer actually measures the amount of emitted radiation (usually infrared) and the wavelength of maximum emission of a particular substance. With calibration techniques, the amount of radiation and the wavelength of maximum emission are directly related to the temperature of that substance (Ruscher and Lusher, 1999).

    Bimetallic thermometer

    This type of thermometer consists of two different metals (usually iron and brass) which are welded together to form a single strip. As the temperature changes, one metal will expand more than the other, causing the strip to bend. This bending is amplified by a series of levers which is attached to a pointer on a scale. Your household thermostat is an example of a bimetallic thermometer. A thermograph is another type of bimetallic thermometer. The metal strip is connected to a pen which traces the temperature on a piece of paper attached to a drum which rotates with time. Bimetallic thermometers are not nearly as accurate as the thermometers discussed above (Ruscher and Lusher, 1999).

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    Temperature recorders

    Graphic recorders

    Graphic recorders use electric temperature measurement systems and record the time and temperature data on strip charts or circular charts. These charts are a permanent record of times and temperatures. Graphic recorders are available as stationary equipment or as portable, battery powered devices.

    Data loggers

    Data loggers use electric temperature measurement systems and periodically report the information to a computer and memory "chip" inside the logger. The data logger can be permanently connected to a computer, or connected at the end of the recording episode. Time and temperature data are displayed graphically or as a list of readings on the computer monitor. The data can be copied onto the computer’s hard or floppy disk for a permanent record. Data loggers are available as stationary equipment or as portable, battery powered devices. Data loggers can record data from one or a group of temperature measuring devices simultaneously.

    Data logger systems are available with computer-generated call up services, either via e-mail, FAX, computer-generated voice messages or digital pager messages. When the data input shows a discrepancy from a normal or expected condition, the computer generates the telephone-based message to key personnel. The message type (FAX, voice, e-mail or pager) and destination telephone number are pre-determined by the user depending upon the location and type of discrepancy (Cox, 1999).

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    Suppliers of temperature measuring/recording equipment:

    Cole-Parmer Instrument Company
    625 East Bunker Court
    Vernon Hills, IL 60061-1844
    Phone: 888-409-3663
    Fax: 847-247-2929
    Web: http://www.coleparmer.com/catalog/default.asp

    Cox Technologies
    69 McAdenville Road
    Belmont, NC 28012
    Phone: 704-825-8146
    Fax: 704-825-5128
    Web: http://www.cx-en.com/cox.htm

    Fisher Scientific
    Pittsburgh, PA
    Phone: 800-766-7000
    Fax: 800-926-1166
    Web: http://www.fishersci.com

    The Foxboro Company
    Phone: 888-369-2676
    Web: http://www.foxboro.com/index1.htm

    Hantover
    700 Karnes Blvd.
    Kansas City, MO 64108
    Phone: 800-821-2227
    Fax: 816-931-3272
    Web: http://www.hantover.com/home.html

    Taylor Precision Products, L.P.
    2311 West 22nd Street
    Oak Brook, IL 60523
    Phone: 630-954-1250
    Fax: 630-954-1275
    Web: http://www.taylor-enviro.com/

    Weber Scientific
    2732 Kuser Road
    Hamilton, NJ 08691
    Phone:800-328-8378
    Fax: 609-584-8388
    Web: http://www.weberscientific.com

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    Thermometer calibration

    See Chapter 2.

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    Temperature Measurement Monitoring Tags

    Table 6-4. Temperature measurement monitoring tags
    Test Kit
    Analytical Technique
    Supplier
    3M MonitorMarkTM Threshold Indicators 
    [Used to determine maximum temperature exposure for frozen and refrigerated products]    		 Blue-dyed chemicals with specific melting points 3M Microbiology Products 
    3M Center, Building 275-5W-05 
    St. Paul, MN 55144-1000 
    Phone: 800/228-3957 
    E-mail: microbiology@mmm.com
    ColdSNAP+ dual-temperature recorder Bimetallic sensing element that snaps at pre-determined temperatures Telatemp Corp.
    Fullerton, CA
    Phone: 800-321-5160
    Web: http://www.telatemp.com
    VITSAB® TTI
    [Temperature monitoring carton and pallet tag.]    		 Enzymatic color indictors to show the amount of temperature exposure of a stored or shipped temperature-sensitive commodity. Cox Technologies, Inc.
    Attn: James Cox
    69 McArdenville Rd.
    Belmont, NC  28012
    Phone: 704/825-8146
    Web: www.cx-en.com/default.htm

    Contents

    References

    Anonymous. "Thermometers" EarthLab Digital Library, Ross Computational Resources, http://earthlab.meteor.wisc.edu/~grb/leveltxt/advanced/wxinst/thermom.htm (26 May 1999).

    Cox. 1999. "What is RealTimeAlert™?" Cox Technologies, Belmont, NC. http://cx-en.com/RealTimeAlert.htm (27 May, 1999).

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