Preservative Trends in Wet Wipes

Abstract

The topic of preservation is always of importance to formulators and finished goods marketers. Formulators are aware of the necessity to adequately preserve their products in order to ensure product safety and be in compliance with legislation. This task is made much more difficult when marketing requirements are added to the factors influencing the preservative choice. Demands such as global approval, soft preservation, »free of…«, etc. have limited the number of acceptable actives.

Full text

5-2011
English Edition
International Journal for Applied Science
• Personal Care • Detergents • Specialties
W. Siegert
Preservative Trends in
Wet Wipes

44 SOFW-Journal | 137 | 5-2011
COSMETICS
PRESERVATIVES
sisting of good raw material quality,
good production hygiene and a vali-
dated
preservative system (1). The influ-
ence of the non-woven, the production
process, the choice of preservatives,
preservative efficacy testing, responsible
care and hygiene measures have to be
taken into consideration.
The Guidelines for Good Manufacturing
Practice of Cosmetic Products (GMPC)
from the Council of Europe are recom-
mendations for the guidance of cosmet-
ic manufacturers. The microbiological
quality
management (MQM) is a part of
GMPC.
The Need of Preservation
Microorganisms can grow on almost
every substance existing in nature and
are often able to attack or even decom-
W. Siegert*
Preservative Trends in Wet Wipes
Introduction
The wet tissues market is a growing busi-
ness. Besides cleansing tissues like wet
toilet paper, baby wipes or hard surface
wipes other products such as sun pro-
tection lotion or deodorants are offered
as wipes.
The wet tissue liquids are mostly aque-
ous, the cellulose is a good nutrient, the
non-woven is always moderately conta-
minated with microorganisms and the
storage temperature is nearly optimal
for microbial growth. All factors for mi-
crobial attack (Fig. 1) are fulfilled.
To produce microbiological faultless wet
tissues, an integrated microbiological
quality management is necessary, con-
The topic of preservation is al-
ways of importance to formu-
lators and finished goods
marketers. Formulators are aware
of the necessity to adequately
preserve their products in order to
ensure product safety and be in
compliance with legislation. This
task is made much more difficult
when marketing requirements are
added to the factors influencing
the preservative choice. Demands
such as global approval, soft
preservation, »free of…«, etc. have
limited the number of acceptable
actives.
Abstract
-
Fig
.1
Factors for microbial attack
Growth
Organisms
Nutrient
Temperature
Moisture
-
Fig
.2
Microbial degradation of ethanol

pose them. The biological degradation
has to be stopped for a certain period. A
preservative must be added, but for en-
vironmental reasons the preservative
should be biodegradable, too. This is no
conflict; for example a concentration of
ethanol between 50 and 90 % it is a good
disinfectant, between 13 and 50 % it
acts as preservative, but below 13 %
ethanol will be biologically degraded to
acetic acid (Fig. 2).
For wet wipes the need for preservation
can be summarised as follows:
•Wet tissues are an excellent environ-
ment for the growth of bacteria, yeasts
and moulds.
•The demand for flushable wipes and
the increased use of natural fibres
make mould growth with its easily
visible staining more likely.
•
Environmental requirements (e.g. from
the EU Detergent Directive) to use on-
ly biodegradable detergents increase
the susceptibility of the wet tissues to
microbial growth.
•The demands for flushable wipes and
the increased use of natural fibres
make mould growth with its easily
visible staining more likely.
•To ensure product and consumer safe-
ty, the addition of preservatives is
necessary.
Parameters which Influence the
Performance of the Preservation
The performances of the preservatives
are mainly influenced by:
•Formulation of the wet tissue liquid
•Type of nonwoven
•Quality of raw materials
•Quality of nonwoven
•Type of preservative
•Amount of liquid per tissue
•Production process
•Distribution of the wet wipe liquid
onto the wipe
Trends within Preservatives in
Wipes
In a study from Biocide Information Lim-
ited about biocides in wipes the most
sought after properties of preservatives
in wipes are:
•Broad spectrum of activity (bacteria &
fungi)
•Effective over a wide pH range
•Easy to use and handle
•Compatible in raw material and for-
mulation
•Cost effective at low concentrations
•Practically free from odour and colour
•Extremely low toxicity to humans
•Environmentally acceptable
•Approved for use by many regulatory
bodies world-wide
Selection of Preservation
When selecting preservatives for wet tis-
sues a number of factors have to be con-
sidered.
Legislation is an essential issue (Fig. 3).
SOFW-Journal | 137 | 5-2011 45
COSMETICS
PRESERVATIVES
-
Fig
.3
Different regulations for cosmetic wipes
-
Fig
.4
CIR Database

Cosmetic wipes marketed in the Euro-
pean Union have to be in compliance
with the Cosmetics Directive 76/768/EEC
http://eur-lex.europa.eu/LexUriServ/Lex
UriServ.do?
uri=CONSLEG:1976L0768:20
090225:EN:
PDF and the New Cosmetic
Products Regulation 1223/2009 http://
eur-lex.europa.eu/
LexUriServ/LexUriServ.
do?uri=OJ:L:2009: 342:0059:0209:EN:PDF,
which applies latest
from 11 July 2013.
The EU regulation is similar adopted
from many countries as e.g. the ASEAN
Cosmetics Directive. Beside this, the
most important regulation is related to
the USA. Most producers of a cosmetic
product follow the CIR recommenda-
tions (Fig. 4).
Wet tissues that are claimed for cleans-
ing of hard surfaces have to be preserved
according to the Biocidal Product Direc-
tive (BPD) http://eur-lex.europa.eu/Lex
UriServ/LexUriServ.do?uri=CONSLEG:20
03R2032:20070104:EN:PDF. The scope of
the BPD is very wide and covers disin-
fectants for home and industrial use as
well as preservatives for manufactured
and natural products.
Difference in Regulations on
the Example of IPBC
Fig. 5 shows the different evaluations in
the EU compared to the CIR recommen-
dation.
The lowest use concentrations in the dif-
ferent regulations are the recommended
ones for international formulations.
Fig. 6 shows an example of an acid based
preservative.
Preservative Actives in Focus
Most preservative actives are in a certain
public discussion. In most cases scientif-
ic assessment of the suspected risks is not
completed yet. Typical examples are:
Formaldehyde/Formaldehyde-donors
DMDMH, imidazolidinyl urea,
diazolidinyl urea
•suspected of carcinogenic potential
Organic Halogen Compounds
Isothiazolinones, methyldibromo
glutaronitrile, IPBC
•sensitisation potential
46 SOFW-Journal | 137 | 5-2011
COSMETICS
PRESERVATIVES
-
Fig
.5
Different evaluations in the EU compared to the CIR recommendation
-
Fig
.6
Observance of different regulations

Bronopol
•avoid nitrosamine formation
Parabens
Methyl-, propyl-, ethyl-, butyl-,
isobutylparabens suspected of
•pseudo-oestrogenic and androgenic
potential
•association with breast-cancer
•association with skin aging
(methylparaben)
Benzyl Alcohol
•listed on Annex III CPD as perfume
»allergen«
Phenoxyethanol
•glycol ether discussion in France
Possibilities for Future
Developments
Most new developments are based on
following actives and preservative en-
hancer:
Organic acids
•sorbic acid
•benzoic acid
•dehydroacetic acid
Alcohols
•benzyl alcohol
•phenoxyethanol
Cationics
•polyaminopropyl biguanide
Multifunctional additives
•ethylhexylglycerin
•glycol (butylene glycol, pentylene
glycol, etc.)
Chelating agents
•EDTA
•tetrasodium glutamate diacetate
Synergistic Mixtures
To minimise the amount of preservative
actives, synergistic mixtures have been
developed (2-6):
•Combinations of preservative actives
•Addition of multifunctional actives to
boost the antimicrobial effect
•Addition of chelating agents
•Combination of multifunctional ac-
tives to achieve self-preserving sys-
tems
Synergistic Combinations of
Preservative Actives
The efficacy of a simple acid / alcohol
mixture (Product A) was compared with
euxyl® K 702 (Product B) using the syn-
ergistic effect described in the patents
DE4026756 and US5670160 with fol-
lowing compositions:
The testing was performed using a ser-
ial dilution test to compare the minimal
inhibition concentrations (MIC values),
a germ count reduction test to compare
the biocidal effect and also a repeated
challenge test to evaluate the efficacy
as preservative under practical condi-
tions.
Determination of the minimum in-
hibitory concentration in serial dilution
tests produced the following values at
pH 5.5:
Dilutions of product A and Product B
are prepared with sterile tap water and
adjusted with sodium hydroxide to pH
5.5. 50 ml portions of the end solu-
tions are inoculated with 0.5 ml mi-
croorganism suspension (initial micro-
organism count approx. 108cfu/ml) and
stirred.
The solutions are streaked out onto tryp-
tone soya agar or sabouraud-dextrose
4% agar after 3, 6, 24, 48, 72 and 168
hours, depending on the test organism.
47 SOFW-Journal | 137 | 5-2011
COSMETICS
PRESERVATIVES
Product A Product B
Phenoxyethanol 74% 74%
Benzoic acid 12% 12%
Dehydroacetic acid 7% 7%
Aqua 7% 4%
Ethylhexylglycerin 2%
Polyaminopropyl biguanide 1%
Test organisms ATCC N°
Pseudomonas aeruginosa 15442
Escherichia coli 11229
Candida albicans 10231
Aspergillus niger 6275
Product A Product B
Species ATCC N° MIC value [%]
Gram-negative:
Burkholderia cepacia 17759 0.50 0.25
Enterobacter gergoviae 33028 0.75 0.06
Escherichia coli 11229 0.25 0.06
Klebsiella pneumoniae 4352 0.50 0.12
Pseudomonas aeruginosa 15442 0.50 0.25
Pseudomonas fluorescens 17397 0.25 0.06
Pseudomonas putida 12633 0.50 0.12
Gram-positive:
Staphylococcus aureus 6538 0.50 0.12
Staphylococcus epidermidis 12228 0.50 0.06
Mould fungi:
Aspergillus niger 6275 0.25 0.12
Penicillium funiculosum 36839 0.25 0.12
Yeasts:
Candida albicans 10231 0.25 0.12

SOFW-Journal | 137 | 5-2011 48
COSMETICS
PRESERVATIVES
-
Fig
.7
Reduction of microorganism for produt B in comparison to product A

The cultures are incubated for 48 hours
at 37 °C, except in the case of Aspergillus
niger, which is incubated for 72 hours at
25 – 27 °C. The evaluation is made on the
basis of a semi-quantitative assessment
of the microbial growth of the streaks.
In Fig. 7, the microorganism reduction
achieved for product B in comparison to
product A at pH 5.5 as a function of the
contact time and use-concentration is
presented for the various test organisms.
Product B has a more efficient germ re-
duction, as evidenced by the greater kill
rate at earlier time readings. This is es-
pecially useful for pre-contaminated
raw materials, such as the production
water or the non-woven, as they may be
more easily sanitised with product B.
The Importance of pH Control
The pH value is a critical control point for
the efficacy of preservatives based on
organic acids. The pH value has not only
be checked in the wet tissue liquid, but
in a liquid squeezed from the tissue. As
typical example a wet tissue liquid pre-
served with 1% phenoxyethanol, benzyl
alcohol, potassium sorbate mixture
(
euxyl® K 700) is demonstrated in Table 1.
Particularly Airlaid showed a severe in-
fluence of the pH.
Phenoxyethanol is a familiar and well
accepted cosmetic preservative. The ad-
dition of ethylhexylglycerin enhances
the efficacy of phenoxyethanol (euxyl®
PE 9010). The innovative, multifunction-
al additive affects the interfacial tension
at the cell membrane of microorganisms,
improving the preservative activity of
phenoxyethanol. Due to its water solu-
bility it can be used in clear solutions,
which is often a problem with paraben
based preservatives. Several hundred ef-
49 SOFW-Journal | 137 | 5-2011
COSMETICS
PRESERVATIVES
Wet wipe liquid itself Wet wipe liquid squeezed from the tissue
Immediately after After one month Immediately after After one month
production storage production storage
pH 5.1 pH 5.1 pH 5.5 pH 5.5
Table
1
Influence of the nonwoven on the pH value
Phase INCI Name Function % w/w
A Water (Aqua) 43.00
B Hydroxyethylacrylate (and) sodium Thickener, emulsifier 0.60
acryloyldimethyl taurate copolymer
(and) squalane (and) polysorbate 60
Isopropyl palmitate
Binder, emollient, solvent
5.00
Mineral oil 5.00
C Water (Aqua) q.s.
D Sodium palmitoyl proline (and) Lipo-amino soothing 0.50
nymphaea alba flower extract agent
Tocopheryl acetate Antioxidant 0.10
Fragrance Fragrance 0.10
Phenoxyethanol/ethylhexyl- Preservative 1.00
glycerin (9:1)
100.00
250% of solution based on the dry weight of the wipe for the substrate SPUNLACE viscose/polyester
65/35 55 g/m2
Table
2
Example of a wet wipe formulation passing challenge testing
-
Fig
.8
Effect of EDTA on combination phenoxyethanol/ethylhexylglycerin

ficacy tests in different leave-on-formu-
lations proved the mixture of phenoxy-
ethanol / ethylhexylglycerin to be far
more effective than phenoxyethanol
alone and to be comparable with tradi-
tional phenoxyethanol / paraben mix-
tures (5).
Table 2 shows an example for
a wipe formulation.
Addition of Chelating Agents
Chelating agents can enhance the effi-
cacy of »soft preservatives«. Fig. 8 shows
the effect of EDTA on the combination
phenoxyethanol / ethylhexylglycerin in
the
before described germ count reduc-
tion test.
Glutamic acid, N,N-diacetic acid, tetra-
sodium salt (GLDA) (Dissolvine® GL) →
INCI Tetrasodium Dicarboxymethyl Glu-
tamate, a readily biodegradable chelat-
ing agent, that can be used as alterna-
tive for EDTA. Especially when used to-
gether with citric acid GLDA shows a
better effect as EDTA (Fig. 9).
Self-preserving Systems
Self-preserving technology is composed
of six »hurdles«:
1. Good manufacturing practice (GMP)
I. Cold or hot aseptic filling
II. Clean-room technology
2. Hygiene-compliant packaging
3. Emulsion form
4. Water activity
5. pH control
6. Multifunctional ingredients with
biostatic effect.
Fig. 10 shows antimicrobial ingredients
used in »self-preserving« skin care prod-
ucts. Ethylhexylglycerin enhances the an-
timicrobial efficacy of these ingredients.
An optimised combination is 70% Oc-
tane-1,2-diol with 30% 3[(2-Ethylhexyl)
oxy]1,2-propandiol →INCI Caprylyl Gly-
col / Ethylhexylglycerin (sensiva® SC 10),
it is suitable to formulate wet wipes
without classical preservatives
.
SOFW-Journal | 137 | 5-2011 50
COSMETICS
PRESERVATIVES
-
Fig. 9 Effect of GLDA on a combination phenoxyethanol/ethylhexylglycerin
-
Fig
.10
Example of antimicrobial ingredients used in »self-preserving« skin care
products
General Technical Aspects
Solution versus Emulsion
The change from solutions to emulsions
is changing various aspects:
•Solutions must be preserved with
water-soluble actives
•Good physical stability
•Easy to produce
•Only one interface ==> liquid / solid
•Emulsions can be preserved with
partly water soluble systems
•Stability must be checked carefully
•One more interface ==> oil /water
•Migration of preservatives into the oil
phase might occur
•Special equipment necessary
•Single layer wetting is preferred.
The Influence of the Production Process
The main parameters influencing the mi-
crobial stability are listed (7):
•Variation in weight of impregnated

wipes dependent on the method of
manufacture.
•An impregnation of the nonwoven
prior to conversion into the finished
stack of wipes provides a more uni-
form product.
•Prevent a discharge of actives from an
immersion bath – especially cationic
compounds are adsorbed on the non-
woven.
•Stack impregnation leads to a less
uniform distribution of the wet wipe
liquid.
•The ingredients of the wet tissue liq-
uid can be separated on the tissue like
in a thin layer chromatography.
•Depending on the dosing system you
can get a non-uniform impregnation
leading to microbiological spoilage.
•Apply the wet wipe liquid uniformly
with a shower from the top.
The influence of using sustainable/
natural sources
Natural raw materials lead to changes in
the demand for microbial protection:
•Biodegradable ingredients need
better protection
e.g. sugar-based surfactants
•Flushable wipes need special
attention
51 SOFW-Journal | 137 | 5-2011
COSMETICS
PRESERVATIVES
•Natural fibres, like cotton or cellulos-
es, are changing the typical product-
spoiling microorganisms
e.g. Trichoderma viride is a typical
cellulose-degrading mould
•challenge testing has to be adapted
•Natural fibres might carry a higher
microbial load.
Summary
Safety and care for consumer and prod-
ucts are legally demanded. A cosmetic
product should not damage human
health.
The finished product has to be stabilised
against microbial growth.
Market Situation
•Limited number of preservative ac-
tives
•Almost every active under public dis-
cussion
New concepts in preservation required
•Formulators are looking for new al-
ternatives to be free of molecules un-
der discussion
•Preservation must be part of new for-
mulation concepts, not an after-
thought
•Focus on antimicrobial stabilisers
•substances not listed on any positive
list for preservatives (e.g. Europe,
Japan)
•
claims like »free of harsh preservative«,
»paraben-free« are achievable
References
(1) Karl-Heinz Diehl, The key to microbiological
quality assurance SÖFW-Journal, 03-1992
(2) K.Weber, J.Siebert: Organic acids, mild cosmet-
ic preservatives, low sensitation potential,
comparative tests, colour stability SÖFW-Jour-
nal, 06-2003
(3) W. Siegert, The Benefit of Using Synergistic
Mixtures of Preservatives SÖFW-Journal, 12-
2006
(4) W. Beilfuß, M. Leschke, K. Weber, A New Con-
cept to Boost the Preservative Efficacy of Phe-
noxyethanol, SÖFW-Journal, 11-2005
(5) M. Leschke, S. Wüstermann, A Reliable Alter-
native for Traditional Preservative Systems,
SÖFW-Journal, 04-2006
(6) W. Siegert, Can New Biodegradable Complex-
ing Agents Replace Tetrasodium EDTA to Boost
Preservatives? SÖFW-Journal, 1/2-2008
(7) W. Siegert, Microbiological quality manage-
ment for the production of wet-wipes, House-
hold and Personal Care Today, 2-2008
* Author’s address:
Wolfgang Siegert
Schülke &Mayr GmbH
22840 Norderstedt
Germany
Email: Wolfgang.Siegert@schuelke.com
