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Sunday, January 29, 2012

Food Preservation

Candied lemon slice.
Modern media has a remarkable love-hate relationship with preservatives. It's a paradox: on the one hand, we can only consume so much food at any one time, on the other, alarmists condemn food that has been preserved for later consumption. It's a decidedly first world issue: in cultures where starvation is a very real threat, and food availability is a concern, the skills and technology of refrigeration-free food preservation are valued.

You've heard those alarmist claims about how a Hostess Twinkie (or was it a McDonald's french fry?) is so synthetic that it doesn't rot. Basically, preservation involves retarding the growth of micro-organisms for as long as we can, applied right, a sandwich can last two years on the battlefield.

One technique is modifying the physical conditions: remove oxygen, keep the temperature too high or too low for microbes to grow. The problem with these is that it's energy intensive and fragile to keep around. Dehydration is another method, which is more stable, but it changes the chemical properties of the food item (just compare dried cilantro to fresh).

And then there's chemical preservation - but this is where lots of the bogeymen live. The very term preservatives carry some sort of stigma, but most of the claims are overblown. Demonizing nitrates in meat curing continues apace, despite few confirmed scientific evidence to any health effects. And how about those big three chemical preservatives that no one seems to object to: salt, sugar and alcohol.

Those things are so accepted that they aren't listed as preservatives, when in fact, they are in every sense chemical preservatives. High concentrations of salt or sugar dehydrate microbes, preventing their growth - that is how honey can keep at room temperature indefinitely, or how fish sauce is stable.

Or is it that artificial preservatives are the problem? Pure crystalline sucrose (table sugar) doesn't exist outside of human intervention - fitting the definition of artificial. If you call the compounds in a cup of tea by their formal chemical names, you'll come up with a bunch of fearsome sounding words - but it doesn't change their truly innocuous nature.

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