No air, no bugs… right?
Posted by Andrew Wadge on 14 September 2009 in Science, safety and health
Unfortunately, it’s not that simple. Even in the absence of air, some types of bacteria can grow on food – Clostridium botulinum is one of these. We know this nasty bacterium multiplies, without air, even on chilled food stored at temperatures as low as 3°C. Because this bacterium produces a very harmful toxin that causes severe, and sometimes fatal, food poisoning known as botulism, it’s vital that appropriate controls are in place to make foods safe.
Vacuum packing and modified atmosphere packing are two processes that are used to inhibit the growth of bacteria and make food stay fresher for longer. While shopping, you may have noticed that some foods, such as bacon and smoked salmon, are vacuum packed. The packing process involves removing air from the packaging that surrounds the food and preventing its return by an airtight seal. Other foods, such as prepared salads that resemble an extended pillow, are packed in something known as a modified atmosphere. These foods have the air in the packet replaced with an inert mixture of gases after packing.
But because removing air is not enough to safely apply a shelf-life of more than 10 days at chill temperatures (3°C to 8°C), the two packing processes should be used in combination with one or more controlling factors. These controls include, among others, the level of acidity and the sodium chloride (salt) concentration of the food.
But, as with the application of any process, there are risks. So I welcome today’s launch of an online training course about vacuum packing and modified atmosphere packing. This food safety tool aims to give local authority food law enforcement officers who are responsible for food hygiene an enhanced understanding of these packing processes and the importance of the microbiological risks. The course complements the existing vacuum packed chilled foods guidance and factsheet for small businesses and enforcement officers, and supports the classroom-based version of the training available to enforcement officers.
The recent outbreak of E.coli on a Surrey farm, although not a food safety issue, reminds us of how seriously unwell people can become from bacteria. So I must emphasise that during the development of this tool, we have not forgotten the outcomes of the Pennington report that was published in March. This report on the public inquiry into the 2005 outbreak of E.coli O157 in Wales, highlighted concerns about the dual use of vacuum packing machinery for raw and ready-to-eat foods because of the risk of transferring harmful bacteria if the equipment is not cleaned properly. As part of our response to that lucid report, we are reviewing what further guidance is needed in this area, and this includes commissioning new research. Currently, there are no specific rules prohibiting the use of the same piece of vacuum packing equipment for raw and ready-to-eat foods.
I hope enforcement officers, as well as anyone else wanting to learn more about Clostridium botulinum and food safety, find the online course useful.
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BA Festival of Science
I would be interested to know if anyone has the answers to the following questions
Can the organism E.coli 0157 (from prior contamination of the equipment) be introduced inside the food packaging during the vacuum packing process?
Can E.coli 0157 survive inside the food packaging on the food?
Can E.coli 0157 survive on the outside of the food packaging and for how long?
What would be the answer to the above questions in relation to other low
infective dose pathogens such as campylobacter.
Frank Feechan
Environmental Health and Trading Standards
Posted by Frank Feechan on September 14, 2009 at 04:19 PM BST #
I am familiar with the risks posed by Clostridium botulinum generally and the specific threat which can arise with vacuum packing.
I am less clear about the ability of E.coli O157 to survive on food which is vacuum packed.Presumably it must survive on vacuum packed raw foods and contaminated cooked foods.
Also is there a risk that the organism may survive on the outside of food packaging ?
Posted by Frank Feechan on October 26, 2009 at 02:34 PM GMT #
There is some evidence to suggest that food poisoning bacteria, which could include E. coli O157, could be introduced inside the packaging of vacuum packed foods from other sources. Whether the bacteria survive, inside or outside the packaging, and for how long, would be dependent on a number of factors, for example, the temperature of heat treatment and storage of the food and its pH and salt content. But what is more important is to clean equipment and surfaces thoroughly to stop bacteria contaminating food in the first place.
Posted by Andrew Wadge on November 05, 2009 at 03:53 PM GMT #