Make those bacteria do the 100m hurdles

When I was a kid (last century) at Grammar School in the UK, taking part in athletic activities was compulsory.  One event that sticks in my mind is the 100m hurdles.  It's important to get a rhythm going and take the same number of steps between the landing and takeoff for each hurdle.  This seemed to go well for the first two or three hurdles, but it often became apparent that I was progressively falling short of my takeoff point for the later hurdles.  Eventually, I either stumbled or had to take a couple of extra steps.

This principle is applied to modern food preservation.  "Hurdle Technology" is a term coined by Lothar Leistner in about 1985.  The concept is simple.   Set up a series of "fences" and force bacteria to jump over them; if they don't fall at the first one, a later fence may trip them.  In food, the fences are low levels of preservatives, modified atmospheres, special packaging, low temperatures, acid pH and so on.  Some bacteria will be able to grow at refrigerator temperatures, but not in acid, or without oxygen etc.

There is a tendency among consumers to regard food processing as something sinister thought up by food technologists and done by manufacturers; fresh food is somehow better.  In fact, by use of multiple hurdles, food can be kept for longer and the amounts of preservatives in the food are reduced without compromising safety.