Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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A METHOD OF DISINFECTING HARD SURFACES
The present invention relates to a method of
disinfecting hard surfaces using disinfectant compositions,
in particular, compositions comprising an aqueous solution
of a lower alcohol and an anti-microbial compound. The
method is suitable for, although not restricted to food-
processing disinfection and kitchen hygiene.
Hard-surface contamination by bacteria, yeasts and
moulds represents a hazard in food processing and kitchen
hygiene; and may result in food-poisoning micro-organisms
being transferred to food product~.
Accordingly, there is a need for disinfectant product~
which reduce the numbers of micro-organisms on food-contact
surfaces to acceptable levels and help to prevent those
surfaces from being re-contaminated.
Effective biocidal compositions are known in the art.
In general, in order to achieve the necessary level of
disinfecting action, they contain either high levels of
alcohol, which is undesirable in view of the evident safety
hazards during processing, storage and application, or they
contain relatively high levels of one or more biocidal
compounds, which i8 also undesirable for application to
surfaces coming into contact with food products.
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It has now been found that in compositions based on
aqueous solutions o~ alcohol and conventional amino- or
an~onium-based anti-microbial compounds, the inclusion of
(preferably organic) acids in amounts sufficient to yield
acid pH-values, allow a considerable reduction in the
levels of both the alcohol component and the biocidal
compound. This is particularly surprising since the
biocidal compounds of this type are generally thought to be
more effective at neutral or alkaline pH values.
Accordingly, the present invention provides a method
of disinfecting hard surfaces by application thereto of an
aqueous disinfectant composition comprising:
a) at least 10% by volume of a lower alcohol
selected from the group consisting of ethanol,
isopropanol and mixtures thereof;
b) 5 to 500 ppm of an anti-microbial agent which is
a di(C8-C18) alkyl di(C1-C4)alkyl ammonium
chloride, and
c) 0.1 to 10~ by weight of an acidic compound; said
composition having a pH of 2-4.
Thus, we have found that the method according to the
present invention, not only avoids the aforementioned
disadvantages, but also provides both disinfecting action
at application and preservative action after application,
i.e. protecting the treated surface from re-contamination.
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An example of a suitable anti-microbial agent is
didecyl dimethyl a~monium chloride such as Bardac 22 (a
registered trademark by Lonza, Switzerland).
In general, the anti-microbial compounds are included
in amounts of from S to 500 ppm, in particular 5 to 100
ppm. Preferred levels of the anti-microbial compound range
from 20 to 50 ppm.
The second essential component of the composition is a
lower alcohol, namely ethanol or isopropanol, the latter of
which, optionally in admixture with the first, is
preferred. Where both are present, the volume ratio of
ethanol to isopropanol ~s preferably from 1:1 to 1:3.
The concentration of the alcohol component is at least
10~ v/v and normally lies within the range of from 10 to
50% v/v. Preferred are concentrations in the range of from
15 to 40% v/v, in particular 20 to 40% v/v.
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The third essential component of the composition is an
acidic compound. Although both mineral and organic acids
capable of providing this pH may suitably be included, when
intended for the particular field of application referred
to above, it is preferred to use food-grade alkyl
carboxylic acids or hydroxyacids. Suitable such acids
include acetic,
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citric, fumaric, lactic, malic and tartaric acid, the
preferred members of which are citric and lactic acid.
The acidic compound is included in an amount of from
0.1 to 10~ by weight, and preferably in an amount of from 2
to 5% by weight. The amount should be sufficient to
provide the composition with a pH-value of from 2 to 4.
The composition may include water and,
optionally, minor ingredients to improve its effectiveness
and/or consumer acceptability. More in particular, the
composition may contain minor amounts of surfactants,
wetting agents, colouring agents and perfumes.
The method will normally involve application of the
composition by spraying or sprinkling thereof onto the
surface to be treated, in view whereof the composition may
be fixed with a propellant to provide a formulation
suitable for use as an aerosol spray.
Alternatively, the compositions may be applied to the
surface being impregnated in a substrate of woven or
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~315196
non-woven (e.g. paper) material to form a disinfectant wet wipe.
The invention will now be further illustrated by way of
example.
Example 1
Compositions were tested having the following basic formulation:
10 isopropanol 30% v/v
acid 0.1 or 1% by
weight
didecyl dimethyl ammonium chloride 25 or 50 ppm
water balance
The compositions were adjusted to pH = by HC1 or NaOH.
The anti-microbial activity was measured against two yeasts,
Saccharomyces cerevisiae and Zygosaccharmoyces rouxii, using the
20 quaternary ammonium compound at a level of 50 ppm, and against
one type of bacterium, Escherichia coli, using the quaternary
ammonium compound at a level of 25 ppm. The anti-microbial
activity was measured by way of a standard suspension test at
25C and using a contact time of 5 minutes.
The data in Table 1 demonstrate the significant enhancement
of the activity of the quaternary ammonium compound by organic
acids, in particular at the 1~ by weight levels.
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TABLE 1
Logl0 reduction in viable counts
in the presence of 50 ppm (yeasts)
or 25 ppm (E. coli) didecyl dimethyl
ammonium chloride
S. Z. E.
Acid % cerevisiae rouxii coli
None added 2.18 0.002.10
Orthophosphoric 0.1 2.170.00 2.11
0.1 3.87 0.404.70
Sulphamic 0.1 2.72 0.082.20
1.0 3.45 0.094.05
Glycolic 0.1 3.42 0.462.47
1.0 >4.60 3.46>5.10
Acetic 0.1 - - 2.44
1.0 - - >5.73
Acetic:Formic(1:1)
0.1 - - 3.74
1.0 >4.60 >4.60>5.10
Example 2
A composition was formulated comprising 30% v/v
isopropanol, 1% by weight acetic acid, 25 ppm of didecyl
dimethyl ammonium chloride and water. This composition
was compared with the same composition without the
ammonium compound to test its anti-microbial activity when
sprayed onto Staphylococcus aureus bacteria dried on PCV
tiles. The Staphylococcus aureus bacterium has been found
to be one of the most resistant vegetative when dried onto
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hard surfaces and it also constitutes a food-poisoning
risk. From Table 2 it is evident that the composition
containing both the acid and the ammonium compound is
highly effective.
TABLE 2
Spray composition Logl0 Bacteria recovered
2 hours after spraving
lO Water 4.2
30% isopropanol + l~ acetic acid4.1
30% isopropanol + 1% acetic
acid and 25 ppm QAC <2.3
Example 3
Compositions containing 30%v/v of isopropanol, 25 ppm of
didecyl dimethyl ammonium chloride, the amounts and types
of acids indicated in Table 3 and water were tested in the
same manner as in Example 2. The results in Table 3
clearly indicate that also other types of food-grade
organic acids can suitably be used to achieve satisfactory
anti-microbial action.
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TABLE 3
Spray liquid Log10 reduction in
viable bacteria
after: 5 min 2 h
Water 0.1 1.5
Isopropanol 0.8 2.6
lO Isopropanol + 2% lactic acid 3.7 4.9
Isopropanol + 5% lactic acid 4.7 >5
Isopropanol + 2~ citric acid 4.2 >5
Isopropanol + 5% citric acid >S >5
Isopropanol + 2% acetic acid >5 >5
15 Isopropanol + 5% acetic acid >5 >5
