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Kitchen Science - Mar 2010
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Week 2
Pickling is a method that is used to kill microorganisms and to allow the storage of food for longer periods. The low Ph Kills the microbes
http://en.wikipedia.org/wiki/Pickling
Anti microbial effects of acetic acid and mustard flour
Decrease the water activity. The water activity in a food is the water that is available for microorganisms to be active and reproduce. Drying, adding sugar and salting decrease the water activity of foods so that the microbes can not function.
Smoking: can be hot or cold. The smoke is an antioxidant and antimicrobial but is often combines with salting or drying to improve keeping qualities. Smoking can also work through reducing water activity.
All of these preservation methods (Pickling, reducing water activity, smoking) seemed pretty obvious at first, but when I read through them, "voila"! Now I understand why bread I've removed from the freezer gets moldy within a day or two.. the moisture from thawing releases water (condensation) from the chemical grips of the bread and makes it available for molds, etc to use for growth!
Also, I always assumed that smoking merely dried meats. I wondered how they acquired their flavor (and didn't taste of burnt ash), but more importantly how they didn't go bad... It makes sense now that the smoke usually contains a high amount of phenols/compounds, which are antioxidants, which slow oxidation/rotting! But how do these phenols last within the smoked meat so long?
I must say, reading the work of french chemist Herve This has also helped me understand food chemistry better. Has anyone else read Herve This?
Here is my absolute favorite picking recipe:
PICKLED SWEET ONIONS
5 large (or many small) sweet onions!
4 quarts water
4 tbs salt
Peel off papery onion skins and soak for two hours in the water and salt. Peel and discard the tough inner skin. Soak the onions for 48 hours in a brine of 1 1/2 C salt and 4 QTS water.
Drain the onions and dry well.
In a large kettle, bring to a boil, 1 C sugar and 1/2 gallon white vinegar. Add the onions and cook for 5 minutes. Pour into sterile canning jars and add to each jar: 1 tsp each celery seed and mustard seed and 4 or 5 allspice berries. Seal.
I'm always intrigued by fermentation - the idea that some of the micro-organisms produced by, basically, allowing something to rot, is what keeps other less friendly micro-organisms at bay.
The same goes for preserving with things like saltpetre (potassium nitrate) http://en.wikipedia.org/wiki/Potassium_nitrate#Uses
basically, we use poisons to preserve, which I think is pretty cool. It also makes me think that in the old days, when they were working out how to use this stuff, people must have had stomach aches really often...