A part of the backyard is devoted to vegetables, fenced to keep out all the herbivores that wander through the yard. This year I am learning to make pickles, lots of different kinds of pickles. I comb through the cucumber vines every other day or so, looking for cukes just the right size for pickles, but apparently, one of them got away, escaped through the fence and grew like Alice in Wonderland after she ate one side of the cake she found in the rabbit hole.
Mega-cucumbers don’t make great pickles, but my mother-in-law taught me to make the most of what you have, so I’ll take out the seedy center and make pickles out of the rest of it.
What does this have to do with biology, you might ask?
I though it might be appropriate to talk about some of the backyard life we can’t see but are absolutely essential players in the ecology of the backyard, as well as the biochemistry of food preparation (and preservation), and that would be the bacteria.
Pickling food is an ancient art, probably first done 4000 years ago in Asia and India, where food tended to spoil quickly due to high daily temperatures. Real pickling is a fermentation process that encourages the growth of lactic acid producing bacteria and discourages the growth of the bacteria that produce decomposition and rot. This is accomplished simply by soaking the food in a salty solution for a period of weeks. The taste of a pickle comes from the concentration of lactic acid and other fermentation products the bacteria churn out while consuming the carbohydrate stored in cucumber cells, and of course the combination of spices added to the pickling solution.
(photo from http://www.thehungrymouse.com/2009/06/10/quick-fresh-pickles/. Check out the quick pickle recipe on their website)
But why doesn’t this leave us with mushy, fermented goo? How do you get crisp pickles, why is the addition of just the right amount of salt, water, and vinegar essential for that crisping process? Too little salt = mush; too much salt = inedible.
This is where the biochemistry comes in (really technically it would be chemistry 101, but since we are working with living plant tissue, I call it biochemistry instead). Salt and water will move across plant cell walls and membranes to reach an equilibrium with the medium outside the cell. So, after soaking the cucumber slices in salty water for some time, salt will have diffused into the plant cell (from the brine) and it will have dragged additional water with it (osmosis) to equalize the concentration inside and outside the cell. This addition of salt and water inside the cell makes them swell up, but cells have a cinch around them (the cell wall) which disallows infinite expansion. And that’s why the cucumber slices now taste salty and crunch when you bite them.
One extra trick to make those pickles extra crispy: soak the cucumber slices in ice water for several hours before adding the pickling solution. The refined process goes something like this: (L to R; top to bottom) 1) slice the cukes; 2) put them in a big bowl; 3) add ice water for several hours; 4) drain off ice water and pack slices into jars with appropriate spices; 5) add boiled pickling solution and then cap; 6) can them or refrigerate them.
(photo from http://aliceandthemockturtle.blogspot.com/2009/08/how-to-make-crispy-pickles.html Another good recipe for quick and easy pickles.)
Really easy, really tasty, and look at all the work those fantastic little microscopic creatures are doing for you.