A bulletin for the Australian Food Industry August 1999
Contents: Refrigerated retail cabinets | Cheese from unpasteurised milk and listeriosis | Alicyclobacillus spp. - a source of flavour taints in acidic foods | Dioxins in food | Volatile nitrosamines in food and drink | Disinfection of seeds for sprouting
Refrigerated retail cabinets
As the result of an initial request by the Australian Supermarket Institute, Standards Australia is revising the existing Australian Standard (AS 1731) for frozen food retail cabinets. At the same time it is expanding the scope of the Standard to incorporate cabinets designed to display chilled foods. The new Standard is to be titled Refrigerated Display Cabinets. The Standard will contain a number of cabinet classifications based on a combination of climate class and maximum package temperature category. A draft Standard will be available for public comment in September.
Proposed national food safety standards place no temperature requirements on frozen food. This is seen as a quality factor not a food safety matter. While this makes for simple standards, it does nothing to assist manufacturers and retailers meet consumer requirements. Nor do the proposed safety standards place any temperature requirements on chilled foods which are not potentially hazardous.
For the display of potentially hazardous foods, however, there is a requirement that the food must be stored below 5°C or at another temperature if the food business demonstrates that the time-temperature history of the food will not adversely affect the safety of the food.
The Australian Food and Grocery Council is also to release a revised Cold Chain Code of Practice. This revised Code maintains the recommendation of earlier versions that chilled foods should never be stored (displayed) above 4°C and frozen foods should never be stored above minus 18°C.
Committee ME/8 of Standards Australia, which is working on the revised Standard, has decided to use the British Standard BS EN 441 as a model for the new Australian Standard. The objective of the Standard is to standardise construction requirements and performance assessment procedures for cabinets for use by manufacturers, suppliers, purchasers, operators and regulators of these systems. The Standard will have the same multi-part format as the British Standard to facilitate updating and future review.
Of particular importance to all parties is Part 6: Classification according to temperature. AS 1731 recognized that the traditional -18° C product temperature requirement in the top or visible layer of a frozen food retail cabinet was impractical. It could only be achieved with a different type of refrigeration plant from the one commonly used and the cost could not be justified for the minimal gain in quality likely to be achieved. This was partly because field experiments showed that frozen foods spent a small proportion only of their life in the visible layer of a cabinet. It was also recognized that the compromise reached in the Standard was not entirely satisfactory to ice cream manufacturers as relatively brief temperature abuse could seriously damage ice cream and similar products. The compromise reached was that, under test conditions, the average temperature in the visible top layer should not exceed -13°C. A case could be made for special lower temperature cabinets for ice cream.
BS EN 441 also recognizes this fact, as the European experience in this regard is exactly the same as the Australian experience. BS EN 441 has two separate classes for frozen food cabinets again under test conditions. One class accepts a greater temperature fluctuation between the highest temperature of the warmest test package and the lowest temperature of the warmest test package. The British Standard also accepts that the highest temperature of the warmest package may exceed -18°C in both cabinet classes.
Since the Australia New Zealand Food Authority has asserted that food quality should be a matter for fair trading law rather than food law, the Cold Chain Code of Practice will be the major factor in shaping commercial arrangements between cabinet suppliers and retailers. It is therefore important that all parties, but especially retailers, are aware of the revision of the Standard and place their views before the Committee.
It is important to note that the performance standards of cabinets which comply with the requirements of either the existing AS 1731 or BS EN 441 are dependent on factors other than the cabinet construction. Some of these factors are: foods must be loaded into the cabinet at the recommended temperature; the cabinet must be loaded, particularly with respect to the air inlet and load line, so that the desired air flow pattern is not impeded; the cabinet should be situated within the store so that it is not subject to unreasonable ambient temperature variations.
Chill temperature refrigerated cabinetsPublished and unpublished data obtained from surveys in Australia and overseas consistently show the retail cabinet as a weak link in the cold chain. This is particularly the case with chilled foods.
Chilled foods frequently arrive at the retail dock in compliance with the Cold Chain Code of Practice and proposed food safety legislation. This is partly due to the high standard of most distribution cold stores and partly due to the widespread practice by retailers in Australia of transporting mixed loads of chilled and frozen foods to retail outlets. The use of mixed loads protects the temperature of chilled foods at the expense of the temperature of frozen foods.
Australia does not currently have a Standard for chilled food retail cabinets but manufacturers face similar problems to those faced with maintaining recommended temperature for frozen foods. The greatest problems arise in retail display where marketing requirements for open multi-deck display cabinets are in conflict with optimum design requirements for low food temperatures.
Visible products are subject to incident radiation causing rises in temperature. However because of the closeness of the required product temperature (<5°C) to the refrigeration air temperature, design difficulties are increased. If refrigerated air temperatures are reduced much below 0°C, product freezing will occur, often ruining the product.
British and European retailers work under different legal restraints from those which will be contained in the proposed national food safety standards. The current BS EN 441 allows for three classes of chilled food cabinet based on the highest temperature of the warmest test package and the lowest temperature of the warmest test package. The highest test package temperatures are 5°C, 7°C and 10°C with corresponding lowest test temperatures of -1°C, -1°C and +1°C respectively.
Compliance with food safety standards in Australia is to be determined by audit. Although the frequency of audit is yet to be determined, for many retailers it may well be twice per year. It is inevitable that if accurate records of temperature in retail cabinets are kept, some fluctuation will occur including fluctuation above 5°C. While the draft standards nominate a product temperature maximum of 5°C for potentially hazardous foods, most cabinet monitoring systems measure air temperature only.
When high temperature fluctuations do occur, the time for which a food is exposed to such air temperature fluctuations will only be available to an auditor if the monitoring system automatically records the data. Two questions then emerge. Will retail operators be required to retain all records of logged temperatures between audits or will they be required to retain only what is termed 'exemption data' where temperature has moved above 5°C?
The second question is how does a food business, including a retailer, demonstrate that the time-temperature record of a food, where the air temperature has risen above 5°C, has not adversely affected the safety of the food.
This is important because the draft standards do not in any sense propose a food safety objective or end point for this temperature control (Dairy, Food and Environmental Sanitation 16 1996 374). Is the food safety objective, e.g. not permitting more than two generations of Listeria monocytogenes or not permitting more than 10 generations of Salmonella spp., to be decided by individual auditors? This should not be the role of auditors.
Food safety, food quality and the refrigerated retail display cabinet Standard are all interdependent. The draft Standard for the cabinet deserves careful study by participants in the cold chain while opportunity for public comment remains.
Australian Standards are not legal documents although they may be called up in Commonwealth or State legislation. Subject to approval by Standards New Zealand, the final document on refrigerated display cabinets will be published as a joint Australian/ New Zealand Standard.
Contact:
Vincent Aherne,
Standards Australia
tel: 02 9746 4700 fax: 02 9746 8450
Food Science Australia
PO Box 52, North Ryde 1670. Tel +61 2 9490 8397 Fax +61 2 9490 8499
Email enquiries@csiro.au