applied for sterilisingpackagingmaterial prior to filling(Mohr and Duggal,
1997), sterilising contact lenses and sterilising the surface of fruit and
vegetables.Hydrogenperoxide is bothbactericidaland sporicidal(Hugoand
Russell, 1999),in generala concentrationof 6% is bactericidal. Peroxygensare
generally more active against Gram-positive bacteria than Gram-negative
bacteria (Russell,1990;McDonnell and Russell, 1999).To achievea sporicidal
effect, concentrationsbetween10 and 30%are necessary. Peracetic acidis
commercially available in 15% solutionsas a mixture of water, hydrogen
peroxide and acetic acidand acts fasterthanhydrogen peroxide. It has a broad
spectrum of efficacyagainstviruses, bacteria,yeastand spores(Bernstein,
1990).Compared withhydrogenperoxide, the activity of peracetic acid is hardly
influencedby organic matter (Russell, 1990;McDonnelland Russell,1999).
Disadvantages are that peroxygenscorrode on toolsand equipmentand are
aggressiveto, e.g., human tissues(Reuter, 1998).However the development and
use of anticorrosiveshas reduced this concern(Marquiset al., 1995).Modeof action
The modeof actionof peroxygensis basedon free-radical oxidation(e.g.
hydroxyl radicals)of essentialcell componentssuchas lipids, proteinsand DNA
(McDonnelland Russell, 1999).Peraceticacidnot onlyattacksthe proteinsin
the cell wall but also migrates into the cell and disruptsinner cell componentsas
well(Donhauseret al., 1991).4.2.4 Alcohols
The mostwidelyused alcoholsfor disinfection are:ethyl-alcohol(ethanol,
alcohol), isopropylalcohol(isopropanol, propane-2-ol) and n-propanol, the
latter especially in Europe(Mohr and Duggal,1997;McDonnell and Russell,
1999). In food production areas, alcohols are particularly used for the
decontamination of hardsurfaces of equipment (e.g. fillingmachines). The
most effectiveconcentrationis between 60 and 70%v/v (Mohr and Duggal,
1997). The concentrations to achieve reduction of growth or complete
inactivationare higherthanfor chorinesolutions or organicacids.Alcohols
are quickreacting,havea broadspectrumof antimicrobialactivityand inhibit
growth of vegetativebacteria,virusesand fungi.Sporesare ratherresistant
against the effects of alcohol; however, a combinationof 70%v/v concentration
withtemperaturesup to 65 ÎC resultsin inactivation of spores,for example
Bacillussubtilisspores (Setlowet al., 2002).Compared withother disinfectants
the concentrationsappliedare much higher (50±100 times)and in fact alcohols
are onlyeffectiveif usedas the substance itself,insteadof a low-concentration
solution.This propertymakes alcoholmoreexpensive in use compared with
chlorine and QACs, and therefore is not frequentlyappliedon a large,industrial
scalebut is usedmostlyfor applicationssuchas small,difficult to reachspotsin
equipment,temperatureprobesand quick wipe-downsof working surfaces and
scales.
74 Handbookof hygiene controlin the foodindustry