Determine Salinity and Anaerobes

[mcar]

If there would be an experiment; the medium source of bacteria lets say is anchovy sauce.(The sauce is actually a common food condiment). This sauce contain salts to keep it preserved. Now, if the goal is to determine a specific salinity point where bacteria could thrive and eventually spoil the sauce, are there good measures in determining at what point where the bacteria are able to proliferate and thus lose the ability of the sauce to prolong its preservation?

I'm thinking here that we must know what is the bacteria involved here. Now given that we already know it, is it enough to rely on the physiological, and biochemical data of the bacteria to calculate the degree of salinity necessary for the sauce to have? or at least what other useful experimentations are necessary to achieve the goal of the problem here.

Another, my friend asked me this. She has a ketchup sauce contained in a conventional small pack. After certain months, the pack somewhat looked inflated so definitely it must have air inside. In one of their ideas is that, it must be acted upon by an anerobic bacteria. Now, if they would like to identify the bacteria by getting sample from the ketchup sauce, they are worrying that after opening the package and air comes out, the anerobic bacteria might be killed or unless if it is a facultative one, possibly that will not. She asked me if there would be a good way on how to obtain sample that contain the bacteria; isn't it that the bacteria are already present on the ketchup sauce itself?

Since the ketchup pack is sealed too, no oxygen gas must be present inside, that's why they have thought that it is more likely that anaerobic bacteria are thriving there.

[canalon]

For your first question there is a whole field called "predictive microbiology" which is trying to model bacterial growth in food depending on the composition to answer this kind of questions and/or putting expiry dates on the label.

For your second question. If you could use an anaerobic chamber that would be perfect since you could work without oxygen. Since it is not exactly very common and esily available, standard microbiological techniques could be applied, provided you work quickly and put everything in an anaerobic incubation jar afterward. Or you can extract DNA and rely on molecular biology for bacterial identification, and then you do not care about survival.

[mcar]

Thank you for your informative response here.

Another, this anaerobic incubation jar must have a tight-seal cover right? Would it be just possible to make use of sterilized conventional jars?

[canalon]

Well anaerobic jars are usualy specific, because very little bottle are big enough to slide a petri dish in. But in theory as long as you have a tight seal it is OK. Of course you will also need an anerobic pouch to change the atmosphere. Something like that is probably the cheapest:
http://www.vwrcanlab.com/catalog/produc ... A90003-648

Some agar as the Brouwer agar could help you since they allow growth of anaerobes without special enclosure (but they are a pain to prepare....)

[mcar]

I'll searh for the availability of these materials here. Thanks a lot Canalon.