Note: Descriptions are shown in the official language in which they were submitted.
WO 94/06294 2 14 4 3 4 pcr/GB93/ol823
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Microbicidal Compositions and Methods
The present invention concerns microbicidal compositions and methods.
More specifically, the present invention concerns microbicidal compositions and
methods employing aliphatic peracids as microbicide.
15 The use of aliphatic peracids as microbicides is well known in the art. Such
solutions have found favour because they offer a microbicidal system which
has reduced environmental impact and are completely biodegradable.
Many of the micro-organisms on which aliphatic peracids have an fall into
the classes of bacteria and viruses. In particular, the reduction in numbers of
20 viruses is important in controlling or reducing the spread of disease, especially
in areas where there is a risk of cross-infection, for example in hospitals and
clinics. In such areas, it is advantageous if the activity of a microbicidal
composition can be improved as it either allows greater reductions in numbers
of micro-organisms for a given treatment, thus reducing the risks of infection,
25 or allows more cost-effective use of the treatment.
In many applications of aliphatic peracids, the peracid is supplied as a
relatively concentrated solution, and is diluted just prior to use to a
concentration that will give good activity in the chosen application. In many
cases, it is convenient to dilute with mains water supplied to the site of use,
30 which, in many parts of the world, can contain significant levels of cations,particularly calcium and magnesium ions, which make the water "hard". The
presence of hardness ions has been shown in the course of the studies leading
to the present invention to reduce the stability and hence the efficacy of
aliphatic peracids, and although the effect of the hardness ions can to a certain
35 degree be ameliorated by the inclusion in the formulation of a sequestrant for
water hardness, eg EDTA, the benefit is somewhat limited. In any event, the
use of sequestrants at levels that would significantly ameliorate the problems
Wo 94/06294 2 ~ 4 43 40 PCr/GB93/Ot823
caused by hard water adds to the cost of the formulations, and is less favoured
as it can also result in the sequestrant solubilising normally insoluble toxic
heavy metals present in the natural environment, encouraging their entry into
the water system. It would therefore be advantageous to identify aliphatic
5 peracid compositions intrinsically having improved stability in hard water, in the
absence of or in addition to that obtained by the incorporation of a sequestrant.
The microbicidal activity of aliphatic peracids is believed to derive from the
oxidation of chemical components of micro-organisms, and so the peracid is
decomposed during such action. As such, the activity of solutions containing
10 peracids as the only active component is normally restricted by the stability of
the peracid in use. The mechanism of action of peracids means that they are
very suitable for use in shock treatment regimes wherein the levels of micro-
organism are reduced significantly by periodic dosing. In cases where the
substrate that has been treated with a shock dose of peracid is subject to re-
15 contamination during eg storage or further processing, the numbers of micro-
organisms can rapidly reach similar levels to those prior to the treatment, thusnecessitating further treatment. It would therefore be desirable to reduce the
frequency of these chemical treatments by providing an aliphatic peracid
system which maintains its anti-microbial activity over an extended period.
20 It is an object of certain aspects of the present invention to provide
aliphatic peracid solutions having improved activity against viruses.
It is a further objective of some aspects of the present invention to provide
aliphatic peracid solutions having improved stability when diluted with hard
water.
25 It is another objective of particular aspects of the present invention to
provide aliphatic peracid solutions having residual anti-microbial activity.
According to one aspect of the present invention, there are provided
compositions comprising an aqueous solution of an aliphatic peracid, the
corresponding aliphatic acid, hydrogen peroxide, and optionally one or more
30 other aliphatic acids, characterised in that the mole ratio of aliphatic acid to
peracid is greater than 5: 1.
According to a second aspect of the present invention, there are provided
compositions with improved activity against viruses which comprise an
aqueous solution of at least one aliphatic peracid, at least one aliphatic acid and
35 hydrogen peroxide, characterised in that the mole ratio of aliphatic acid to
peracid is greater than 5: 1.
21443~
W O 94/06294 PC~r/GB93/01823
According to a third aspect of the present invention, there are provided
compositions with improved stability when diluted with hard water which
comprise an aqueous solution of at least one aliphatic peracid at least one
aliphatic acid and hydrogen peroxide, characterised in that the mole ratio of
5 aliphatic acid to peracid is greater than 5: 1.
According to a fourth aspect of the present invention, there are provided
compositions with improved residual activity which comprise an aqueous
solution of at least one aliphatic peracid, at least one aliphatic acid and
hydrogen peroxide, characterised in that the mole ratio of aliphatic acid to
10 peracid is greater than 5: 1.
According to a fifth aspect of the present invention, there is provided a
virucidal process in which a virus is contacted with an aqueous solution which
comprises at least one aliphatic peracid at least one aliphatic acid and hydrogen
peroxide, characterised in that the mole ratio of aliphatic acid to peracid is
15 greater than 5: 1.
According to a sixth aspect of the present invention, there is provided a
process for producing a dilute aqueous solution of an aliphatic peracid having
improved stability in which a concentrate containing an aliphatic peracid,
aliphatic acid and hydrogen peroxide is diluted with hard water, characterised
20 in that the mole ratio of aliphatic acid to peracid is greater than 5: 1.
According to a seventh aspect of the present invention, there is provided a
microbicidal process having improved residual activity in which a substrate
which may be contaminated by micro-organisms is contacted with an aqueous
solution which comprises at least one aliphatic peracid at least one aliphatic
25 acid and hydrogen peroxide, characterised in that the mole ratio of aliphatic acids to peracid is greater than 5: 1.
According to an eighth aspect of the present invention there is provided a
process for the disinfection of fruit and vegetables, employing as a disinfectant
an aqueous solution which comprises at least one aliphatic peracid at least one
30 aliphatic acid and hydrogen peroxide, characterised in that the mole ratio of aliphatic acids to peracid is greater than 5: 1.
The aliphatic peracid can be any aliphatic peracid that has a disinfectant
effect. However, in many embodiments, the aliphatic peracid is selected from
the group containing soluble peracids, which may include low molecular weight
35 aliphatic peroxyacids, for example containing up to 6 carbon atoms, of which
especially preferred examples comprise peracetic acid and perpropionic acid.
Other examples include perbutyric acid, persuccinic acid, perglutaric acid and
W094/06294 2'1-443~ pcr/GB93/ol823
peradipic acid, particularly mixtures of persuccinic, perglutaric and peradipic
acids. The peracid may alternatively be selected from hydroxy-peracids, for
example percitric or pertartaric acid. In most preferred embodiments, the
peracid is peracetic acid.
5 The other aliphatic acids which are optionally included in the compositions
according to the present invention are selected from the group containing from
1 to 6 carbon atoms, and are preferably acet~c or propionic acid.
The compositions according to the present invention and employed in
processes according to the present invention are often solutions comprising an
10 equilibrium mixture of an aliphatic peracid, the corresponding aliphatic acid,
hydrogen peroxide, water and, when optional additional aliphatic acids are also
present, the corresponding peracid.
In many embodiments, aliphatic peracids comprise greater than about 0.1%
by weight of the composition, often from about 0.5% to about 20% by weight,
15 and most often from about 1 to about 15% by weight.
In compositions according to the present invention, the mole ratio of
aliphatic acid to peracid is greater than 5: 1. In many embodiments, the mole
ratio is from about 10: 1 to about 40: 1, and some preferred embodiments,
the mole ratio is from about 13: 1 to about 25: 1.
20 Hydrogen peroxide typically comprises from about 0.5 to 20% by weight of
the compositions according to the present invention, often from about 0.75 to
about 15%, and most often from about 1 to about 10% by weight. It will be
recognised by one skilled in the art that for an equilibrium peracid solution
having a high ratio of aliphatic acid to peracid, the concentration of hydrogen
25 peroxide necessary to give an equilibrium composition is often very much lower
than for an equilibrium composition having a lower ratio of aliphatic acid to
peracid. This means that for compositions having equivalent available oxygen,
a greater proportion of the active oxygen is present in the more microbicidally
active component ie the peracid if there is a lower concentration of hydrogen
30 peroxide than if there is a higher concentration of hydrogen peroxide. Thus,
compositions according to the present invention will usually have a greater
microbicidal activity for a given active oxygen concentration than compositions
not according to the present invention.
The compositions according to the present invention often additionally
35 comprise one or more stabilisers to further prolong the storage stability of the
peracid. Such stabilisers are well known in the art, and often comprise
alkyleneaminopolymethylene phosphonic acids, eg cyclohexyldiaminomethylene
WO 94/06294 2 14 43 4 0 PCI-/GB93/01823
phosphonic acid and its salts or hydroxyethylidene diphosphonic acid or salts
thereof.
Other optional components of compositions according to the present
invention are mineral acids, especially sulphuric, phosphoric and nitric acid,
5 which are often employed as catalysts to speed the equilibration of the
compositions during manufacture, corrosion inhibitors, wetting agents,
thickeners, dyes and perfumes.
Suitable corrosion inhibitors can be selected from the group consisting of
alkali metal phosphate salts, especially disodium and dipotassium
10 hydrogenphosphate, triazoles, phosphonates, especially
cyclohexyldiaminomethylene phosphonic acid and its salts.
These optional components can also be employed separately from the
compositions according to the invention by supplying a two pack system in
which one solution is a composition according to the present invention and the
15 other is a solution of other components. These two packs can then both be
diluted in the same solution to form a further composition, also according to the
present invention. Such an approach has the advantage that it is possible to
include in the diluted composition components with desirable properties that
would adversely affect the storage stability of the peracid solution over an
20 extended period, but which do not significantly affect the stability of the
peracid over the storage period of the diluted solution, which is often less than
that of the non-diluted compositions, or at the concentration in the dilution.
Wetting agents can be either anionic, cationic, amphoteric or nonionic.
Particularly suitable wetting agents are alkaryl sulphonic acids or their salts,25 and alcohol ethoxylates.
The compositions according to the present invention can conveniently be
prepared by mixing an organic acid or anhydride with hydrogen peroxide in
aqueous solution, in the presence of any additional components, at a
temperature in the region of from 10C to about 50C and allowing to reach
3 o equilibrium.
The compositions according to the present invention can be employed as
anti-viral agents, especially in the field of medical instrument disinfection.
When employed in such an application, the compositions are often diluted just
prior to use. The dilution is chosen to be such that the concentration of
35 peracid can often be up to about 2% by weight, although the concentration is
usually from about 0.001% to about 1%, preferably from about 0.002% to
about 0.75%. Often, the dilution is by a factor of from about 10 times to
Wo 94/06294 2~ 443 ~ pcr/GB93/ol823
about 10,000 times, more often from about 25 times to about 5,000 times,
depending on amongst other factors, the concentration of peracid in the
starting composition.
The temperature employed for use of the composition is often greater than
5 about 10C, often between about 15C and 75C, more often between about
1 7C and 35C. It is particularly preferable that the compositions are
employed at ambient temperature, and so it will be recognised that this can
vary significantly, although the temperature is often likely to be controlled to a
certain extent by the use of, for example, air conditioning.
10 The compositions can be employed as virucidal agents on or in a wide
range of articles, surfaces or media that are contaminated with viruses, and
may also be employed on objects where there is a risk of virus contamination.
They are particularly suited to the disinfection of hard surfaces and objects
containing metal, especially aluminium, brass, copper and steel. The
15 compositions are also suited to the disinfection of cloth articles, for example
medical dressings, and aqueous media.
The compositions can be applied to the article or surface in a large number
of ways. For example, they can be sprayed or can be wiped using a suitable
distributor, eg a cloth. In many embodiments, however, the compositions are
20 employed as a soak bath in which the article to be disinfected is immersed inthe bath, and then rinsed after treatment to remove substantially all of the
disinfectant.
The contact period employed can vary widely depending on the area of
application, and the concentration of disinfectant. In many embodiments, the
25 contact period is greater than about 30 seconds. In certain preferred
embodiments, the contact period is from about 1 minute to about 60 minutes,
although it will be recognised that periods significantly longer than this may be
employed in cases where the compositions are employed as a soak bath, for
example, up to 24 hours or more.
30 In many applications where the peracid solution is in the form of a relatively
concentrated solution which is diluted with water prior to use, it is desirable
that the dilute solution produced is employed within a reasonably short period
after dilution because, unless the dilution water has been treated to remove
impurities prior to use as a diluent, the impurities present in the water can
35 cause a significant reduction in the peracid concentration, and thus reduce the
effectiveness of the solution. Typical of the impurities which can cause such a
WO 94/06294 2 I ~4 34 0 pcr/GB93/ol823
decomposition are those which are the cause of water hardness, f,or example,
divalent metal carbonate or bicarbonate salts.
It has been surprisingly found that when compositions according to the
present invention are diluted with hard water, ie water containing greater than
5 about 75ppm and up to about 1500ppm (expressed as CaC03) of hardness,
the solutions produced have improved stability when compared to similar
dilutions of peracid compositions not according to the present invention.
It will be recognised that less attention has been paid to improving the
stability of solutions that are diluted just prior to use compared with solutions
10 prepared for long term storage, where the peracid should desirably be retained
for several months. In many cases, it is preferable for the peracid in solutionsdiluted just prior to use to be stable for a period of several days depending onthe application, sometimes up to 10 days, often up to 6 days and in many
instances up to 3 days.
15 The peracid solutions prepared just prior to use can have a very wide range
of peracid concentrations depending on the application, and the conditions
under which they are to be applied. The concentration of peracid can often be
up to about 2% by weight, although the concentration is usually from about
0.001% to about 1%, preferably from about 0.002% to about 0.75%.
20 In many applications for peracid solutions, particularly disinfectant
applications, the solution is employed as a shock treatment and is required to
have a rapid biocidal effect without any need for residual activity. However, incertain applications, particularly where the substrate is subject to re-
contamination, for example when the substrate is recycled aqueous process
25 liquors as in the paper industry or in cooling water treatment, it is
advantageous if the solution has activity which remains beyond the normal
activity period of the peracid alone. In many instances, the recycled process
liquors are subject to regular shock treatment, but there are often periods whenthe shock treatment biocide is less effective and so unless all the micro-
30 organisms have been killed, the microbial numbers can increase. Also in theseless effective periods, the disinfectant can often be insufficiently active to
control fresh microbial contamination. In these cases, it is often not necessary
for the residual activity to be sufficient to have a significant biocidal effect; it is
sufficient for the residual activity to be sufficient to prevent or inhibit significant
35 increases in the microbial population, ie to be biostatic.
It has been surprisingly found that the peracid compositions according to
the present invention have superior residual microbicidal activity, and also that
WO 94/06294 PCr/GB93/01823
~43~Q
their performance as a shock treatment are improved when compared to similar
peracid compositions not according to the present invention.
It will be recognised that the concentration of peracid employed in
applications as a shock treatment with residual activity can vary widely
5 depending on application and the conditions under which it is employed. The
concentration of peracid is often up to about 2% by weight, although the
concentration is usually from about 0.001% to about 1%, preferably from
about 0.002% to about 0.75%.
There are many areas of application for compositions according to the
lO present invention where the improved residual activity is of advantage.
Examples include the disinfection of sugar beet process liquors, cooling water
and other circulating water systems, aqueous pulp and paper process liquors,
animal feed and grain.
The peracid compositions may be dosed manually, but in many
15 embodiments, the dosing is automatically controlled by the use of a metering
pump and a suitable control system which can deliver the peracid according to
a pre-determined programme. The peracid can be dosed in a number of
different ways, for example as a liquid or as a spray by using suitable
equipment known in the art.
20 Another area of application for compositions according to the present
invention is in the area of fruit and vegetable disinfection. Peracid systems are
well known for disinfection in this area, either alone or in a two stage processin combination with a reducing agent which prevents excess peracid from
oxidising and discolouring the fruit or vegetable being disinfected. The
2S concentration of peracid is often up to about 0.2% by weight, although the
concentration is usually from about 0.0001% to about 0.1%, preferably from
about 0.0005% to about 0.05% by weight.
Typical reducing agents include alkali metal salts of sulphite, metabisulphite
and thiosulphate, ascorbic acid and such like, with the most preferred reducing
30 agent being sodium thiosulphate. The concentration of reducing agent
employed is typically chosen to ensure adequate removal of excess peracid and
so the concentration can vary quite widely depending on, for example, the
concentration of peracid employed. In many cases, the concentration of
reductant solution is in the range of from about 0.5g/l to about 50g/l,
35 preferably from about 1g/l to about 10g/l.
It has surprisingly been found that peracid compositions according to the
present invention give superior disinfection and residual activity compared to
WO 94/06294 2 14 4 3 4 0 pcr/GB93/ol823
peracid compositions not according to the present invention. Use of
compositions according to the present invention in a two stage process with
sodium thiosulphate as reducing agent also surprisingly gives superior fruit andvegetable appearance after storage for up to 5 days, particularly in the case of5 lettuce disinfection.
The treatment time for use of compositions according to the present
invention in fruit and vegetable disinfection is often from about 1 minute to
about 60 minutes, and is most often from about 2 minutes to about 30
minutes. When a reductant is employed, the contact time for the reductant is
10 often from about 1 minute to about 30 minutes, most often from about 2
minutes to about 15 minutes. The temperature at which the disinfection and
any subsequent reduction stage take place can vary over a wide range, but is
often ambient temperature, and so is usually likely to range from about 10C to
about 30C in the United Kingdom, but may differ in other countries.
15 Having described the invention in general terms, embodiments of the
invention will now be described more fully by way of example only.
W O 94/06294 2 ~ 4 ~3 4 PC~r/G B93/01823
ExamDle 1. Preparation of Peracid Composition according to the present
invention.
50.859 of glacial acetic acid, 38.059 of demineralised water, 11.19 of 35%
w/w hydrogen peroxide solution, 1.09 50% w/w hydroxyethylidenedimethylene
5 phosphonic acid solution, 0.159 of dipicolinic acid solution ~10% w/w in 5%
w/w NaOH solution) and 0.79 of 98% w/w sulphuric acid solution were mixed
at room temperature. After 1 week, the solution was analysed as having the
following composition (all % by weight):
lo Peracetic Acid 3.89%
Hydrogen Peroxide 2.21 %
Acetic Acid 52.52%
Mole Ratio of 17: 1
Peracid: Acid
ExamDle 2. Activity against Viruses
A stock of Polio 2 virus containing 1.8 x 108 plaque forming units per ml
(pfu/ml) was treated in a disinfection suspension test at room temperature
(about 20 - 25C) in the presence of horse serum (10%v/v) with a solution of
20 peracetic acid according to the present invention of formula A below, and also
with a solution of peracetic acid not according to the invention of formula B
below. The two solutions were each diluted to give applied peracetic acid
concentrations of 800ppm and 1600ppm. Contact times of both 5 and 10
minutes were evaluated. Neutralisation after the contact time was by 1 /10th
25 dilution in 5% w/v sodium thiosulphate solution also containing 0.025%w/v
catalase. Surviving polio virus was then evaluated by plaque assay according
to the method given by Morris and Waite, "Evaluation Procedures for the
Recovery of Viruses from Water. ll Detection Systems", Water Research, 1980,
Vol 14, pp795-8 on the Buffalo Green Monkey cell line and the Logarithmic
30 Reduction Factor (LRF) calculated. The results are given in Table 2 below.
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11
Table 1 Peracetic Acid Formulations (All % w/w)
Formulation % PAA %AA %H202 Mole Ratio AA: PAA
A 4 47 2 15: 1
B 5 8 20 1.6: 1
AA = acetic acid; PAA = peracetic acid
5 Table 2 Activity of Peracetic Acid Solutions against Polio virus
Formulation Concentration LRF after time (minutes)
A 800 4.1 5.4
A 1600 Total Kill Total Kill
B 800 1.9 2.4
B 1600 3.2 4.0
The results given in Table 2 clearly show that at both concentrations of
peracetic acid, the virucidal performance of Formulation A (according to the
10 present invention) is greatly superior to that of Formulation B (not according to
the invention).
Example 3 Stability of Peracetic acid in Hard Water Dilutions
Samples of hard water containing 192 ppm permanent hardness, and 202
15 ppm temporary hardness (expressed as CaC03) were inoculated to a
concentration of peracetic acid of 20 ppm by dilution by 2,500 and 2,000
times respectively of peracetic acid samples of formulations A and B in Example
2 above. The concentration of peracetic acid in each of the samples was
measures at intervals over 24 hours by iodometric titration in ethane-1,2-diol at
20 <-10C with sodium thiosulphate solution. The results are given in Table 3
below.
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~i~4~
12
Table 3 Stability of Peracetic Acid in Hard Water
Peracetic Acid Concentration (ppm)
Formulation A B
-0 20 20
1 min 16.2 5.3
30 min 14.8 4.2
120 min 14.5 1.8
24 hrs 7- 1
The results in Table 3 clearly show that for 20 ppm peracetic acid, the
5 stability of formulation A (according to the present invention) is superior to the
stability of formulation B (not according to the present invention) when the
formulations are diluted with hard water.
Example 4 Residual Activitv of Peracetic Acid
10 The residual activity and disinfection performance of the formulations given
in Table 4 below were evaluated in a suspension test against a mixed culture of
4 asporogenous bacteria, Escherichia coli. Pseudomonas aeruginosa,
StaDhvlococcus aureus and StreDtococcus faecalis, as an initial inoculum of 1.3
x 106 colony forming units/ml (cfu/ml), and as a rechallenge inoculum of 2.6 x
15 103 cfu/ml after 2 days, and 2.1 x 103 cfu/ml after 9 days. The conditions
employed were a temperature of 20C, water having 100 - 120 ppm hardness
as CaC03, and in the presence of 4 g/l yeast extract.
The viable cell counts were determined after contact times of 10 minutes,
and then at intervals over 14 days by one tenth dilution into a universal
20 neutraliser containing 0.25% w/w catalase to prevent further activity and then
by decimal dilutions of the neutraliser with Maximal Recovery Diluent. The
dilutions were plated out on Plate Count Agar, incubated for 48 hrs at 37C,
and the plate counts measured. The results are given in Table 4 below.
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13
Table 4. Results of Disinfection and Residual Activitv Trial
In the table, AA = acetic acid; PA = propionic acid; PAA = peracetic acid
5 Formulation Number of Viable Organisms after (time) cfu/ml
Acid :PAA
Mole ratio 10 min 1 dav 3 davs 9 days 10 days 14 davs
Water only - 3.3x106 6.7x108 3.5x109 4.7x109 6.5x109 7.3x109
10 500ppm AA - 3X106 2.4x106 3.7x107 3.1x108 2.9x108 4.1x107
500ppm PA - 3.8x106 3.4x106 5x107 2.4x108 2.2x108 4.8x107
30ppm PAA 2.4:1 2.4x103 1.9x104 2.3x109 5.1x109 5.1x109 6.9x109
15 + 56ppm AA
30ppm PAA 19.5:1 460 <10 860 9.2x105 7.2x106 9x105
+ 500ppm PA
+ 56ppm AA
30ppm PAA 23.5:1 160 C10 685 7.6x103 2.5x104 3.9x106
+556ppm AA
The results given in Table 4 show that the compositions according to the
25 present invention, ie those with a mole ratio of aliphatic acid to peracid ofgreater than 5: 1 give superior initial disinfection compared to the compositionnot according to the present invention. This is surprising as the acids alone donot have any significant disinfectancy. The good residual activity of
compositions according to the present invention is clearly demonstrated by the
30 results for 3 days. These results are 24 hours after a challenge with 2.6 x 103
cfu/ml. The results for both compositions according to the present invention
are extremely low compared to the results for the other compositions. A
similar pattern of results is demonstrated for the results after 10 and 14 days,
showing the consistently better performance of compositions according to the
35 present invention.
WO 94/06294 2 ~ ~ ~3 ~ ~ PCr/GB93/01823
14
Example 5. Vegetable Disinfection.
Samples of chopped iceberg lettuce were contacted for 5 minutes at room
temperature with peracetic acid solutions prepared by diluting compositions of
formula A and B above, and formulation C below with water having 1 34ppm
5 permanent and 180ppm temporary hardness as CaC03 to give the
concentrations of peracid given in Table 5 below. After the contact time, the
lettuce was washed for 2 minutes with a 5g/l sodium thiosulphate solution
rinse. The samples were stored for 3 days at 4C, and then their physical
appearance and bacterial count determined. The bacterial count was obtained
lo by stomaching 109 of lettuce in MRD, then serial dilution in MRD, and then
plating out on Plate Count Agar for 2 days incubation at 30C. The results are
given in Table 5 below, expressed as a Log Reduction Factor (LRF) over an
untreated control.
15 Table 5. Results of Vegetable Disinfection Trial
The control had 8.4 x 105 colony forming units per cm3 after 3 days
Formulation PAA Concentration LRF after 3 Days
A 50 ppm 1.81
B 50 ppm 0.16
C 50 ppm 1.09
A 100 ppm 2.92
B 100 ppm 0.97
C 100 ppm 1.78
Formulation % PAA %AA %H202Mole Ratio AA: PAA
C 1 9 6 11.4: 1
The results of this trial show that the results obtained in vegetable disinfection
are significantly better in terms of microbial contamination and physical
condition for formulations A and C ~according to the present invention),
particularly for formulation A, than the results for treatment with formulation B
25 ~not according to the present invention).
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ExamDle 6. Bacteriostatic Performance
100 ppm peracetic acid solutions were produced by aqueous dilution of
peracetic acid formulations according to formulations A (according to the
invention) and B (not according to the invention) in Example 2 above. In
5 addition, a 100 ppm peracetic acid solution was produced by aqueous dilution
of a third formulation, D. Formulation D (not according to the invention)
comprised 15% w/w peracetic acid, 14% w/w hydrogen peroxide and 28%
w/w acetic acid, with a mole ratio of acetic acid to peracetic acid of 2.4: 1.
The solutions were evaluated in duplicate for bacteriostasis against
10 Pseudomonas aeruginosa and StanhYIococcus aureus in the German DGHM
Standard Method. The results are given in Table 6 below, where a "-"
indicates no growth and a " + " indicates growth.
Pseudomonas Staphylococcus
aeruginosa aureus
Duplicate 1 2 1 2
Formulation
A
B + + + +
D + + + +
From the results in Table 6, it can clearly be seen that the composition
according to the present invention, formulation A was the only formulation that
gave bacteriostasis.
