A bulletin for the Australian Food Industry June 1997
Contents: Food poisoning and the regulatory response | Cutting boards - is plastic better than wood? | Hygiene monitoring by ATP luminometry | AQIS Director defends food inspection system | Cheese from unpasteurised milk banned | Oysters and Hepatitis A | Farmers seek compensation over chemical residue in meat | Australian Smallgoods Food Safety Guidelines
Hygiene monitoring by ATP luminometry
The proposed Standard A of the national food hygiene standards requires that food business proprietors comply with the following obligations:
- to have a written food safety program;
- to ensure that all food handlers have skills and competencies in food hygiene matters commensurate with work activities;
- to develop appropriate sanitation programs; and
- to provide for the recall of unsafe food as appropriate.
In order to evaluate a sanitation program, it is desirable to obtain results quickly. Evaluation of the effectiveness of a sanitation program may be carried out in a number of different ways, e.g. visual inspection which is not usually regarded as adequate; swabbing followed by microbiological analysis; contact plates on exposed surfaces; or ATP (adenosine triphosphate) bioluminescence.
Two recent papers (Trends in Food Science and Technology 8 1997 pp.79-84 and Food Science and Technology Today 11 (1) 1997 pp.15-24) discuss the use of ATP luminometry for assessing sanitation procedures and comment on the potential increase in its use as HACCP based food safety plans become mandatory.
ATP is present in all living organisms and is present in foods as non-microbial ATP. The technique as used does not discriminate between microbial and non-microbial ATP but this is not viewed as a serious disadvantage. Product residues remaining on poorly cleaned surfaces will act as a source of nutrients for bacteria and may protect them from the action of sanitizers.
ATP bioluminescence is based on the reaction that gives the firefly its name. The enzyme luciferase, which is present in the firefly, uses the chemical energy in the ATP molecules to drive oxidative decarboxylation of luciferin with the resultant production of light. The amount of light produced is directly related to the microorganisms and food residue present. The light output for this reaction is then measured in arbitrary units in a luminometer.
Several different companies now market test kits based on taking a sample by swabbing a surface and then taking a simple, prescribed procedure to bring the ATP into contact with the enzyme system. The light emitted is then measured and a result of the 'pass-marginal-fail' type given.
Results in the papers cited above and experience gained by some larger processors indicate that, when used correctly, the technique provides an initial aid to food manufacturers in assessing the efficiency of sanitation programs. Its main advantage is of course that it provides results rapidly and can be used to assess cleaning procedures before a processing line is brought back into operation. Its main disadvantage to date has been the relatively high cost of the equipment which has limited its use to larger manufacturers.
However with research and development proceeding rapidly and prospective markets expanding, the cost of commercial systems in the future seems likely to fall and the specificity of the technique may also be refined. The technique, and similar ones in development, will not replace traditional microbiological testing of surfaces but can be used to complement it on a routine basis.
Food Science Australia
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