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Dairy Products Safe and True

Part B     Standards

MRD Standard 4

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Standard for Checking the Operation of Pasteurisers (Superceded)

1. Purpose
2. Scope
3. References
4. Definitions
5. Responsibilities for checking and reporting
6. Checking and testing HTST pasteurisers
7. Checking batch pasteurisers (Holding Method)
8. Independent pasteuriser evaluation
9. Reporting pasteuriser checks

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1.     Purpose

This standard defines:

• the checks that need to be carried out, and provides a guide to the frequency of checks, to ensure that pasteurisers operate correctly and that no unpasteurised product goes forward for further processing; and

• the information on the operation of pasteurisers that must be reported to MAF Reg so:

- it can be assured that product is safe, and

- it is able to provide export certificates for dairy product as needed.

2.     Scope

This standard applies to the use of all pasteurisers that operate according to the standards listed in Section 3. Companies which use other heat treatment processes to ensure product safety must establish other checking and reporting procedures, which must be approved by MAF Reg.

3.     References

3.1     Pasteuriser equipment

Equipment for pasteurisation must be designed and constructed according to one of the following standards, or with an alternative approved by MAF Reg:

• MQD 1B Dairy Food Manufacturing Equipment, Chapters 5 and 7

• MQD 12 Market Milk Code of Practice, Part C, Sections 5 and 7

• AS 39931.1: 1992. Equipment for the pasteurisation of milk and other liquid dairy products. Part 1: Continuous-flow systems

• 3-A Accepted Practices for the Sanitary Construction, Installation, Testing and Operation of High-temperature Short-time and Higher-heat Shorter-time Pasteuriser Systems, Revised, Number 603-06.

3.2 Pasteuriser installation

Pasteurisers must be installed according to one of the following standards:

• MQD 1A Sanitary Design of Dairy Food Factories, Chapters 6 and 9
• MQD 12 Market Milk Code of Practice, Part B, Sections 6 and 9.

3.3 Pasteuriser commissioning

Refer to IDF Bulletin 200 (1986) Monograph on Pasteurised Milk, Chapter IX, and MQD 1B, Section 5.2.5.

3.4 Pasteurisation requirements

Minimum temperature/time combinations are given in MRD-Stan 3. Pasteuriser operating requirements and pasteurised milk quality standards for export dairy products are contained in the Dairy Board's procedures and specifications manuals. For products sold on the domestic market they are contained in the Food Regulations 1984, and in MQD 12 Market Milk Code of Practice, Part D, Section 3.3 and Part F, Section 3.1.

3.5 Records

Records must be kept to demonstrate that no unpasteurised milk passes forward for further processing, and of the checks laid down in this standard. Records of pasteuriser operation must be kept as required by MQD 1B, Chapter 5, and MQD 12, Part D, Section 3, and they must be available for inspection.

4.     Definition

Pasteurisation is defined in MRD-Stan 3.

5.     Responsibilities for Checking and Reporting

This standard shall be adopted by a product factory as part of its product safety programme, unless the factory has MAF Reg approval for alternative standards which might be defined in the factory's quality documentation.

For every pasteuriser, the product factory shall prepare a programme of checking and testing, including the frequency with which they will be carried out, and the procedure for reporting to MAF Reg.

The product factory may delegate checking and reporting work to another competent organisation. The delegation should be made clearly in writing.

6.     Checking and Testing HTST Pasteurisers

6.1     General

The programme of checking and testing shall ensure that the pasteuriser is always operated for the specified product in a manner that complies with the standards in Section 3.

When deficiencies occur, the frequency of checking shall be increased until the problem has been proven to be remedied.

The frequency of checking may be decreased where historical data proves excellent reliability, accuracy and maintainability, provided the decreased frequency still ensures control.

Any change that could affect any performance characteristic of the pasteuriser for the specified product, and the reasons for it, shall be documented.

New and modified pasteurisers shall be checked before they are put into normal use for treating product (see 3.3), and then frequently until a record of proven calibration and reliability has been established. All the checks, tests, and calibrations which were done during commissioning shall be repeated at appropriate intervals, as well as other maintenance operations and checks that become necessary to confirm the reliability of the pasteuriser to meet the standards.

Sections 6.2 to 6.5 specify the checks and tests which are required. The frequencies are indicative, and should be adjusted as indicated above.

This standard includes the checks specified in manual MQD 1 Part C, Good Manufacturing Practice and manual MQD 12.

6.2     Daily checks

The recording thermometer shall be checked daily against the indicating thermometer (which is calibrated against a reference thermometer - see 6.3), and adjusted if necessary to keep it within the standard for pasteuriser instrumentation. For some automated pasteurisers a specific test mode or programme may be required. The recording thermometer shall record the true temperature of pasteurisation, i.e., it must include any recorded correction to the indicating thermometer, with an annotation of the correction applied. Recording pens shall be kept inked.

The divert set point shall be checked daily to ensure that it is set at the desired value. The divert mechanism shall be test activated each day, to confirm that it operates and to estimate the diversion temperature. This may be done during the cleaning cycle or during pre-use chemical sanitation. It is good practice to set the pasteuriser at the normal pasteurising temperature and then lower the temperature of the heating medium in 0.5 ^oC steps of 30 seconds duration until diversion occurs. The recording chart will show the corresponding falls in temperature in the holding tubes and the precise temperature at which the diversion took place. The temperature at which diversion takes place shall not be less than the set-point. Note that a more rigorous test usingcontrolled conditions, for both diversion and resumption of forward flow, shall also be done less frequently.

The constant monitoring of pressure gauge readings during the processing run can provide useful information, e.g. variations in normal operating pressures generally indicate that problems are developing. An increase in pressure in the product line between the flow controller and the plate heat exchanger is a good indicator of a milk solids build-up on the plate surface within the heating section, whereas a drop in pressure will be probably caused by a decrease in pumping efficiency.

Phosphatase measurements should be made three times per day unless there is to be a further heat treatment on the final product. Phosphatase tests should be made frequently when the pasteuriser is operating at the minimum temperature and time conditions.

If the hygiene standards for pasteurised milk (such as coliforms) are exceeded, the equipment should be checked for cracks and holes.

6.3     Thermometer calibration

The indicating thermometer provides a direct reading of pasteurisation temperature independently of the controlling mechanism. It shall normally be calibrated against a reference thermometer by a competent person such as the laboratory manager. Sensors must be calibrated in situ, and the calibration must include the full wiring loop (i.e. sensors, convertors, records, etc).

The frequency of calibration shall be as frequent as necessary to maintain it within the limits of the standard for pasteuriser instrumentation (MQD 1B, Chapter 7 or MQD 12, Part C, Section 7). Typically, the calibration frequency is monthly at first, and it may reduce to once every 3 months if results indicate the thermometer or sensor is sufficiently stable. In all cases the frequency shall be appropriate to the historical calibration results. The recording sensor may be calibrated likewise.

Where either the indicating thermometer or the recording sensor fails to regularly maintain its calibration within the limits of the standard, or where the difference between the indicating thermometers and recording sensor when checked daily is regularly such so as to necessitate readjustment or recalibration of both or either instrument, then the diversion temperature shall be permanently raised by an amount sufficient to fully compensate for the individual or combined lack of precision in these instruments. For example, the diversion temperature must take account of the design capability and calibration results of electronic thermometers.

6.4     Three-monthly check

The divert valve shall be checked every 3 months to ensure it does not leak product into the forward flow line when it is in the diverted flow position.

6.5     Annual checks

Pasteuriser equipment shall be checked annually by competent technical personnel, usually following annual maintenance.

These checks shall include:

• maximum flow rate for the specified product;

• minimum holding time. The results of the maximum flow rate check shall be used to re-determine by calculation the minimum holding time and the minimum pasteurising temperature, and re-set, if necessary, the diversion/rejection temperature set-point and the operating temperature (but refer to 6.6 for circumstances when the direct measurement method must be used);

• normal operational pasteurising temperature;

• direct measurement of the diversion/reject system response time, and re-determination of the divert valve location;

• a check that diversion occurs at a temperature not below the diversion/reject temperature set-point;

• a check that resumption of forward flow occurs only at a temperature not below the diversion/reject temperature set-point

(Note: When using computer controllers the divert and forward flow temperatures must include an extra amount to compensate for the effects of dead bands in the temperature monitoring programme. A dead band is an individual temperature variation that produces no response in the controller);

• recording systems for temperature and flow rate (where used);
• a check that the record of diversion/reject events is continuous;
• chart recorder time accuracy and synchronisation between records of temperature and divert/reject events;
• direct measurement of the divert sensor response time;
• positive pressure difference controller, where one is fitted;
• visual inspection of PHE plates for failure;
• PHE plate gaskets;
• general maintenance of pasteuriser control systems;
• safety of freezing-point depressants and anti-corrosive additives.

The required sensitivity and responsiveness may be relaxed when the time/temperature combination exceeds the minimums specified in MRD-Stan 3. For instance an increase from 72 ^oC to 73 ^oC provides a 5 second safety margin in the holding time, and the required diversion/reject system response time may be increased accordingly.

6.6     Minimum holding time check - direct measurement

The pasteuriser minimum holding time shall be checked by a competent person by direct measurement with suitable equipment:

• after any change that may affect the flow rate or volume of the holding section, such as:
• alteration or replacement of any permanent parts of the holding tube (excluding gaskets and seals);
• replacement or modification of any pumps;
• replacement or modification of any flow controller;
• any downstream alterations;
• any other modification or event which may affect the holding time; and

• at intervals of not more than 5 years, for unmodified plants.

The results of this check shall be used to redetermine the minimum pasteurising temperature, and re-set, if necessary, the diversion/rejection temperature set-point and the operating temperature.

Note: The minimum holding time shall be recalculated annually following the redetermination of the maximum flow rate, as in 6.5.

7.     Checking Batch Pasteurisers (Holding Method)

7.1     General

The general conditions in 6.1 shall apply.

7.2     Daily checks

The recording thermometer shall be checked daily against the indicating thermometer, and adjusted if necessary. The recording thermometer shall record the true temperature of pasteurisation, i.e., it must include any recorded correction to the indicating thermometer, with an annotation of the correction applied.

7.3     Thermometer calibration

The calibration requirements in 6.3 shall apply.

8.     Independent Pasteuriser Evaluation

The programme of checking and testing and the results shall be independently evaluated annually, preferably before start-up, by a competent person who is recognised by MAF Reg for "validation of pasteurisation control and calibration procedures" in terms of MPD-Stan 1. The person shall verify that the programme and the pasteuriser comply with this standard.

9.     Reporting Pasteuriser Checks

The pasteuriser checks listed in 6.4, 6.5, 6.6 and 8 shall be reported to MAF Reg. Reporting procedures are described in MPD-Stan 2, issued with Circular No 5.

Revision Status

Rev	Date	Status	By	Approved
1	17 February 1993	Issued for use	MAF Reg (Dairy)

Copies of MAF Reg Dairy Circulars, Newsletters, MPD-Stans and MRD-Stans are available from:

Publishing Solutions Ltd
P O Box 983
WELLINGTON
Phone: 04-471-0582
Fax: 04-471-0717