Food > Fish and Seafood > Product Inspection > Facilities Inspection Manual CHAPTER 13, SUBJECT 2 To download in Adobe PDF 1. INTRODUCTION These guidelines have been formulated jointly by Agriculture Canada, Fisheries and Oceans Canada and Health Canada. They represent important elements to be considered when carrying out a temperature distribution study1 for any product to be thermally processed in steam-still retorts excluding crateless retorts. When appropriate, temperature distribution studies will be evaluated by these departments using the elements given in these guidelines. Only persons experienced and knowledgeable on thermal processing in steam-still retorts should carry out and evaluate the results of such studies. 1 Adapted from Temperature Distribution Protocol for Processing in Steam-Still Retorts, from the Institute for Thermal Processing Specialists, P.O. Box 2764, Fairfax, Virginia, U.S.A. 22301-0764, (703) 591-1108.2. APPLICATION Temperature distribution studies should be done to: develop or validate a venting schedule; to locate cold or slow heating zones in preparation for heat-penetration studies; in the case of new installations; and for any changes to an installation which may influence the temperature distribution in the product zone. Examples are: changes to steam spreaders, decreased steam pressure in lines, changes to the product loading patterns, changes to the basket and/or dividers, etc. 3. INVENTORY OF THE THERMAL PROCESSING SYSTEM Prior to the selection of the test retort(s) a survey should be made of the following: 3.1 Lay-out Diagram A detailed diagram identifying all equipment for which the use of steam is required (including the numbering system used to identify each retort) and the steam supply line arrangement should be made as prescribed in this section. (Note that it is recommended that all steam lines from the main line to the retort(s) be clearly identified in the diagram from those steam lines feeding other equipment). 3.2 Steam Supply to the Retorts 3.2.1 Boiler(s) Capacity (psi or kPa) Record potential and actual settings, amount of steam developed and available, i.e., pounds or kilograms of steam produced per unit time. 3.2.2 Retort Header Pressure It is important to insure that adequate steam pressure and volume is being delivered to the retort(s). This measurement should be taken when maximum operational demand is made on the steam supply. 3.2.3 Headers, Manifolds, Lines and Valves Record pipe size and length, valve size and types, of the main steam line from the boiler(s) immediately before the pressure/steam regulator to the retort(s). 3.2.4 All Connecting Steam Lines Other than to the Retort Record size of all connecting steam lines to the main steam line noting other equipment using steam (e.g., blanchers, exhaust boxes, etc.). 3.3 Retort(s) A detailed diagram of each retort, including associated operational equipment as identified below, should be made. Where identical retort configurations exist, one diagram is sufficient. The designated retort number(s) must be shown on the diagram. The system should include the full manifold system. 3.3.1 Retort shell Record retort type and internal dimensions. For vertical retorts, note the presence of centring guides and/or baffle plates. 3.3.1 Retort Crates Record maximum number of crates used in each run as well as their design and dimensions. 3.3.3 Steam Supply from Pressure/Steam Regulator to Retort Record pipe sizes, valve type and sizes, pressure/steam regulators or reducers and all pipe fittings including steam by-pass lines and steam spreaders (shape, pipe size, length, location; number, size and location of holes in pipe). 3.3.4 Steam Control Record type of controller (i.e., pressure to air, temperature to air) and location of sensor. 3.3.5 Air System for Controls (if applicable) Record size of air compressors, air dryer capacity, filter type and location(s). Include the line pressure that must be maintained for operation of the controls and how this pressure is controlled. 3.3.6 Other Piping and Required Equipment Record the following information:
3.3.7 Recording Device Note type of recording device (recorder or recorder/controller). For more information consult section 7.6.2.2 of the Recommended Canadian Code of Hygienic Practice for Low-acid and Acidified Low-Acid Foods in Hermetically Sealed Containers (Canned Foods). 3.4 Loading Equipment Record the following information:
Note: It is important to document the survey findings correctly in order to enable a proper evaluation before selecting the test retort(s). The documented survey should be maintained on company's file and updated when necessary. 3.5 Selection of Test Retort(s) All information required in section 3 above must be taken into consideration when selecting the test retort(s). The retort(s) selected should represent the worst possible condition that could influence the delivery of the venting procedure. Note that under certain conditions (i.e., when the plumbing and equipment configuration is not identical for all retorts), it may be necessary to carry out a temperature-distribution study of a number of retorts in a system in order to determine which one represents the worst case. Where all plumbing and equipment configurations are identical, it is generally advisable to select as the worst possible case the retort which is located at the end of the steam line. However, this is not always the case. This is an area where the knowledge and experience of the specialist supervising the study are of upmost importance. 4. TEST EQUIPMENT 4.1 Data Logger Note if data logger has a sufficient number of channels to monitor adequately and record temperatures during the temperature-distribution study. 4.2 Thermocouples Note if thermocouples and lead wires, or other temperature-measuring devices used are of an appropriate type, size, length and number to adequately monitor the temperatures within the retort. 4.3 Temperature-Indicating Device(s) Note which type used (Mercury-in-glass thermometer or other) see 3.3.6 item 8. 4.4 Pressure-Indicating Device(s) Note which type used (if required) see 3.3.6 item 9. 4.5 Stuffing Box (packing gland) Note if diameter is sufficient to accommodate number of lead wires (if thermocouples are used as the temperature measuring device) and specify its location on the retort. 5. STANDARDIZATION OF TEST EQUIPMENT 5.1 Retort Mercury-in-glass (MIG) Thermometer (or equivalent temperature-indicating device) The MIG shall conform with section 7.6.2.1 of the Recommended Canadian Code of Hygienic Practice for Low-acid and Acidified Low-Acid Foods in Hermetically Sealed Containers (Canned Foods). Prior to performing a temperature-distribution test, the MIG thermometer (or equivalent) shall be certified by a recognized authority as meeting the stated accuracy according to specifications, such as set out by the National Research Council of Canada (NRC), and calibrated. If it has been calibrated and certified in the past 12 months, then it should not have to be done again unless there is doubt as to its accuracy. 5.2 Temperature-Measurement System (e.g., data logger, thermocouples, extension wires or other temperature-measuring devices (TMD), etc.)
2 For more information consult the "Standard Guide for Use in the Establishment of Thermal Processes for Foods Packaged in Flexible Containers" ASTM F 1168-88, 1988.6. PLACEMENT OF THE TEMPERATURE MEASURING DEVICES IN THE RETORT A minimum of 12 TMDs (or equivalent) should be used. However, the number of TMDs depends upon many factors, for example, size of the retort chamber zone, container size, number and configuration in the baskets, etc. TMDs shall be placed in the following locations in the retort vessel:
4. For determining the initial temperature (IT), TMDs should be placed in a sufficient number of medium-filled testing containers. Generally two containers have been found to be acceptable. Alternatively, a hand-held thermometer may also be used to make that determination. Ideally all containers in the retort should be equilibrated to a previously identified IT. 7. PREPARING THE TEST CRATES OR BASKETS WITH CONTAINERS
8. TEMPERATURE-DISTRIBUTION TEST 8.1 Set-up
8.2 Critical Items The following are critical and should be monitored and recorded during the test.
8.3 Important Items In addition, the following points are important and are highly recommended to be monitored and recorded during the test.
8.4 Conducting the Test
8.5 Required Parameters for the Determination of a Vent Schedule
For more information on vents and venting system refer to sections 7.6.3.1.7. and 7.6.3.1.8 of the Recommended Canadian Code of Hygienic Practice for Low-acid and Acidified Low-acid Foods in Hermetically Sealed Containers (Canned Foods). |
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