It is important that the washing of fabrics, dishes etc. and the cleaning of surfaces achieve an acceptable degree of
sanitization of biological soils, especially as wash temperatures decrease.
A combination of factors can be responsible for the destruction of microorganisms: their physical removal along with
other soils, the action of wet heat, chemical attack, and oxidation as an indirect result of the presence of oxidative
bleaching agents like perborate.
Washing and surface cleaning will, like the removal of other soils, also detach micro-organisms and permit their disposal.
At temperatures over 40ºC and especially over 60ºC, the wet heat of the washing cycle will itself have a biocidal effect
by denaturing proteins, especially enzymes and cell wall constituents.
While anionic surfactants are only mildly bactericidal, cationics such as quarternary ammonium compounds are very much
more effective. They react with lipids in cell membranes, altering surface features and their permeability so allowing
cell contents to escape.
Hydrogen peroxide and other available oxygen components are highly reactive with organic matter and their deactivation
of proteins and enzymes, like wet heat, produces a strong disinfectant effect.
In addition to their powerful bleaching action, the hydrogen peroxide and especially peracetic acid formed via (activated)
perborate in hot solution also oxidize biological matter strongly. The superoxide radical O2- forms from peroxide in the
presence of metal ions (usually present in cell cytoplasm) and reacts with, and denatures proteins which leads to the
inactivation of vital metabolic pathways.
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At high enough concentrations, borates themselves exhibit significant bacteriostatic and fungistatic activity. The effect
is exploited particularly in hard surface cleaning. Products for this application can contain high levels of borate and
deposit active borate residues on surfaces.
Deodorizing is another function displayed by borates. The ability of borates to inhibit urease enzyme activity, which
otherwise results in the release of ammonia from fabrics stained with bodily soils, has prompted their use as pre-soaking
additives in, for example, the cleaning of re-usable towelling nappies / diapers.
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| Fig G1: borates inhibit microbial growth |
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