Re: gum preservatves
Suitable choice of preservative depends on many factors, such as whether you want to protect from gram negative bacteria, gram positive bacteria, fungi, etc., as well as the storage condition, particularly the pH. Sodium benzoate is an effective bactericide in acidic material (such as soda beverages) but not so effective for materials that are only modestly acidic or not acidic at all. http://silvergrain.com/labs/Biocides A good general purpose biocide with a broad range of protection is 2-phenylphenol (for alkaline pH) and methyl paraben (mildly acidic to neutral pH), thymol, p-chloro-m-cresol, and isothiazolones. Benzoic acid (benzoate) has more narrow spectrum of effect and usage, although it may work ok if you use it at such a high level as 1%. Generally speaking, biocide with carboxyl groups (such as benzoic acid, parabens, etc.) are effective in the pH range where the carboxyl group is undissociated. This limits their useful pH range to the acidic side of the corresponding pKa. Biocide like 2-phenylphenol or p-chloro-m-cresol would be still very effective at 0.1% of the solid material in the solution. Incidentally, I recall that this is probably 2nd or 3rd or 4th time this topic came up, and I've also posted all these and probably some more info in the past. -- Ryuji Suzuki "Strange how people who suffer together have stronger connections than people who are most content." (Bob Dylan, Brownsville Girl, 1986)
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