This is just sort of a note to myself about what elements are necessary in order to preserve foodstuffs. From my explorations of fermentation and other processes, a few common points seem to crop up about how to decrease the likelihood of any pathogens forming. In any case, one never knows when a situation might arise in which refrigeration becomes impossible. It is prudent to at least be aware of certain different ways to preserve foods without it.
There are a few elements then that can be used in some combination in order to produce an environment that inhibits the growth of pathogens which are the following:
-High acidity
-Salt
-Sugar
-Dryness
-Coolness
-Nitrates/nitrites
-Aerobic exposure (in most cases, preservation will be occurring under anaerobic conditions for either the sake of preserving sterility or because the bacteria that is being encouraged, as in the case of lacto-fermentation, are anaerobic, however, in some cases aerobic decomposition may be beneficial or necessary. If one is to ferment meat without the benefit of any of the other preservation techniques than aerobic exposure will be necessary in order so that pathogens do not grow. Aerobic decomposition in and of itself does not appear to pose much of a health risk in my opinion since the most virulent pathogens are anaerobic. The bad facultative anaerobic (which are able to grow in aerobic environments) bacteria will likely just give you some food poisoning but will not likely be life-threatening unless you are immune compromised or have digestive problems. In any case, they are unlikely to get a foothold on a food’s surface unless it has been previously sterilized or comes from an unsanitary environment. Also, take note of the fact that putrefaction technically only refers to the anaerobic decomposition of something)
If we consider a few of the methods used for food preservation we will see that these elements are found in them. For instance, in lacto-fermentation, the environment is salted initially and quickly becomes highly acidic. Furthermore, considering that vegetables are often the ones being fermented in this way, endogenous nitrates/nitrites may be present. In the case of sausage making you have all the ingredients for the development of pathogens since the environment is moist and anaerobic. To hedge against this, salt and nitrate/nitrites are used in order to stop the growth of pathogens. Jerky is traditionally salted and then dried thus also being exposed to air. The preservation of foods in vinegar obviously works through the highly acidic environment. The preparation of high meat chiefly functions through aerobic exposure and (often) cool conditions and refrigeration functions by cooling the environment. Also, salt and sugar can be seen as being analogous to drying as what occurs by adding them is the drawing out of fluid from whatever it is you wish to preserve.
This still leaves, however, the preservation of foods via oil of which I am less certain of as to how it works. The canning process functions by sterilizing everything and then sealing it so that nothing grows thus providing a golden opportunity for obligate anaerobes if anything is done incorrectly in the process. It would seem that oils like olive oil have some antimicrobial properties so that anything you put in them are to be preserved due to the antimicrobial properties of the oil coupled with the anaerobic environment produced by this submersion in fluid. It thus functions through sterility.
We can outline some of the general preservation strategies taken as so:
-Slow down enzymatic and bacterial activity (freezing, drying)
-Destroy bacterial activity and place in a sterile environment (canning, vinegar, oil)
-Allow bacterial activity to flourish under controlled conditions (fermentation)
It would seem to me that taking such guidelines into consideration, one should be able to experiment in many different ways to preserve food besides just the most obvious or common ones.
References:
http://www.wisegeek.com/how-do-salt-and-sugar-preserve-food.htm
Filed under: Bacteria, Canning, Fermentation, Fermented meat, Food preservation, High meat
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