To flush or not to flush ...

This post was originally published on 7th February, 2011.  I accidentally deleted it while trying to answer a question from a reader.  Here it is again.



No, this one isn't about faecal bacteria, at least not directly.

Our major TV news broadcaster was guilty over the weekend of a dreadful beat-up on the use of gas mixtures to extend the shelf life of fresh meat.  Under the banner of "How safe is your meat?", the channel made a big deal of the use of gas mixtures containing carbon dioxide to inhibit bacteria on the meat.  They implied that suppliers were trying to pass off old meat as "fresh" and that the process was used to make the meat look redder and thus deceive the consumer into thinking that the meat was fresher.  A further implication of the banner was that gas flushed meat is unsafe.  Must have been a slow news day.

Meat technologists and microbiologists have known for many years that gas mixtures containing carbon dioxide inhibit bacteria, such asPseudomonas, which are responsible for the development of slime and odours on meat stored under refrigerated conditions.  The gas also inhibits many pathogens, which may potentially cause disease.  

Consumers interviewed in supermarkets said that the meat should be labeled to indicate that it had been gas flushed.  Of course, one supermarket chain said they would do this if customers wanted it, while another tried to take the high ground and claim that they would never gas flush meat.

This is all playing on the ignorance of many consumers about food technology and food safety.  Certainly the meat keeps longer when gas flushed. Why does meat normally have such a short shelf life?  Because some bacteria can grow under refrigeration conditions and turn the meat slimy or produce odours that consumers find objectionable.

Should we ignore and reject the many years of research on food preservation?  Should we perhaps go back to taking meat home wrapped in paper and cooking it the same day?  That's "natural".  Should we reject vacuum packaging - it's not natural, but in fact works in a very similar way to gas flushing.  Consumers have demanded longer shelf life in all sorts of foods - meat, strawberries, smoked mussels, cakes and pastries.  In response, food technologists have developed ways to deliver such foods and these techniques involve preservative chemicals, vacuum packaging, pasteurisation and gas flushing (modified atmospheres).  If we are prepared to go back to foods with a shelf life of just a few days, we can reject gas flushing and other technologies.

If consumers are really concerned about gas flushing, they can recognise flushed packs by the fact that the film is sealed to the tray, or in some cases, such as gas flushed bakery goods, the package looks like a pillow.

Me?  Well, I'll happily buy carbon dioxide flushed meat - it keeps longer and in some cases looks better.