1. business and industrial
2. energy
3. oil

j, Cosmet.
Sci., 54, 175-192 (March/April 2003)
Effect of mineral oil, sunflower oil, and coconutoil on
preventionof hair damage
AARTI S. RELE and R. B. MOHILE, Research
and Development
Department,
Nature CareDivision,MaricoIndustries
Ltd.,
MumbaL India.
Accepted
for publication
April 29, 2002,
Synopsis
Previously
publishedresultsshowedthat bothin vitroandin vivococonutoil (CNO) treatments
prevented
combingdamageof varioushair types.Using the samemethodology,an attempt wasmadeto studythe
propertiesof mineraloil and sunfloweroil on hair.
Mineral oil (MO) wasselectedbecauseit is extensivelyusedin hair oil formulationsin India, becauseit is
non-greasy
in nature,andbecause
it is cheaperthanvegetableoilslike coconutandsunfloweroils.The study
wasextendedto sunfloweroil (SFO)because
it is the secondmostutilized baseoil in the hair oil industry
on accountof its non-freezing
propertyandits odorlessness
at ambienttemperature.
As the aim wasto cover
differenttreatments,andtheeffectof thesetreatmentsonvarioushairtypesusingthe aboveoils,the number
of experimentsto be conducted
wasa veryhigh numberand a techniquetermedasthe TaguchiDesignof
Experimentation
wasused.The findingsclearlyindicatethe strongimpactthat coconutoil applicationhas
to hair as comparedto applicationof both sunflowerand mineraloils.Amongthreeoils, coconutoil was
the onlyoil foundto reducethe proteinlossremarkablyfor bothundamaged
anddamagedhair whenused
as a pre-washand post-washgroomingproduct.Both sunflowerand mineral oils do not help at all in
reducingthe protein lossfrom hair.
This differencein resultscould arisefrom the compositionof eachof theseoils. Coconutoil, being a
triglycerideof lauricacid(principalfatty acid),hasa high affinityfor hair proteinsand,because
of its low
molecularweight and straightlinear chain,is able to penetrateinsidethe hair shaft.Mineral oil, being a
hydrocarbon,
hasno affinityfor proteinsand thereforeis not ableto penetrateand yield betterresults.In
the caseof sunfloweroil, althoughit is a triglycerideof linoleicacid,because
of its bulky structuredue to
the presence
of doublebonds,it doesnotpenetratethe fiber,consequently
resultingin nofavorable
impact
on protein loss.
INTRODUCTION
Morphologically,a fully formedhair fiber containsthree and sometimesfour different
unitsor structures.At its surface,hair containsa thick protectivecoveringconsistingof
layersof fiat overlappingscale-likestructurescalled the cuticle. The cuticle scales
surroundthe cortex,which containsa major part of the fiber mass.The cortex,the
secondunit, consists
of spindle-shaped
cellsthat arealignedalongthe fiberaxis.Cortical
cellscontainthe fibrousproteinsof hair. Thickerhairsoftencontainoneor moreloosely
packedporousregionscalledthe medulla,locatednearthe centerof the fiber. The fourth
175
176
JOURNAL OF COSMETIC SCIENCE
unit is the intercellularcementthat gluesor bindsthe cellstogether,forming the major
pathwayfor diffusioninto the fibers.
The cuticleconsists
of flat overlappingcells(scales).The cuticlecellsareattachedat the
proximalend(rootend),and they point towardthe distalend (tip end)of the hair fiber.
However,cuticledamageevidencedby brokenscaleedgesthat canusuallybe observed
severalcentimetersawayfrom the scalpis causedby weatheringand mechanicaldamage
from the effectsof normalgroomingactions,suchascombing,brushing,and shampooing. Because
of extensivecross-linking,cuticlecellstend to be brittle and, therefore,are
susceptible
to damageby groomingprocedures,
especiallywet combing(1). In long hair
fibers(25 cm or longer),progressive
surfacedamagemay be observed.
The lossof cuticle
cellsby gradualchippingimpairsthe structuralintegrity of hair, leadingultimately to
split endsand fracture.This limits the lengthand the cosmeticqualitiesof hair suchas
Table
I
Designof ExperimentUsing the TaguchiModel
No.
Oils
Hair type
Hair treatment
Oiling sequence
Shampooing
1
2
3
4
5
6
7
CNO
SFO
MO
MO
CNO
SFO
MO
Straight
Curly
Wavy
Permed
Straight
Curly
Wavy
Undamaged
Undamaged
Undamaged
Undamaged
Bleached
Bleached
Bleached
Before
Before
Before
Before
Before
Before
Before
Once
Once
Twice
Twice
Once
Once
Twice
8
MO
Permed
Bleached
Before
Twice
9
10
11
SFO
CNO
MO
Straight
Curly
Wavy
Boiled
Boiled
Boiled
Before
Before
Before
Twice
Twice
Once
12
MO
Permed
Boiled
Before
Once
13
14
15
SFO
CNO
MO
Straight
Curly
Wavy
UV-treated
UV-treated
UV-treated
Before
Before
Before
Twice
Twice
Once
16
MO
Permed
UV-treated
Before
Once
17
18
19
20
21
22
23
MO
MO
CNO
SFO
MO
MO
CNO
Straight
Curly
Wavy
Permed
Straight
Curly
Wavy
Undamaged
Undamaged
Undamaged
Undamaged
Bleached
Bleached
Bleached
After
After
After
Afier
After
After
After
Once
Once
Twice
Twice
Once
Once
Twice
24
SFO
Permed
Bleached
After
Twice
25
26
27
MO
MO
SFO
Straight
Curly
Wavy
Boiled
Boiled
Boiled
After
After
Afier
Twice
Twice
Once
28
CNO
Permed
Boiled
After
Once
29
30
31
MO
MO
SFO
Straight
Curly
Wavy
UV-treated
UV-treated
UV-treated
After
After
After
Twice
Twice
Once
32
CNO
Permed
UV-treated
After
Once
Treatmentsweresequential.
If the treatmentis designated
asCNO-Permed-Boiled-After-Once,it means
permedhair wasfirst put in boilingwaterfor 120 min andair dried,and then 0.2 ml of CNO wasapplied
to it. This treatmentwascarriedout for all 25 hair tresssamples.Twenty-fivereplicatetresses
wereused
for each treatment.
EFFECT
OF COCONUT
OIL ON HAIR
Table
DAMAGE
177
II
Analysisof VarianceData for Half-Head Treatmentsfor ProteinLoss
Sourceof
variance
Hair type
Normal
Between
Oil type MO
Experimentalerror
treatments
Degreesof
freedom
1
38
Sum of
squares
Mean square
F-Value at 95%
confidence
level
34.8
2234.6
34.8
58.8
o.6
1.1
Bleached
Between
1
42.8
42.8
Oil type MO
Experimentalerror
38
1545.7
40.7
Normal
Between
Experimentalerror
1
38
39.6
1345.6
39.6
35.4
1.1
Oil type SFO
Bleached
Between
48.6
1195.6
1.5
Experimentalerror
1
38
48.6
Oil type SFO
1
38
31.6
195.6
31.6
5.1
6.2
1
36.5
36.5
4.9
38
286.5
7.5
treatments
treatments
treatments
Normal
Between
Oil type CNO
Experimentalerror
treatments
Bleached
Between
Oil type CNO
Experimentalerror
treatments
31.5
F theoreticalfor 1.38 degreesof freedomat 95% confidencelevel = 4.08.
smoothness
and shine.Groomingmethodsinvolvingabrasiveprocedures
are known to
damagehair and its appearance.
Historically,coconutoil hasbeenusedasa hair dressingin the developingcountriesin
the tropicalregionsof the globewherethe coconutis cultivatedextensively.Prolonged
useof coconutoil hasbeenknownto lead to healthylookinglong hair, suggestingthat
it may prevent damageto the cuticle in groomingproceduresinvolving abrasion.
Obviousis the lubricatingeffectof oil on fiberfriction,whichreduces
abrasivedamage,
especially
in combing.However,in moderntimes,the trendin hair oil formulationsis
more towardsthe useof non-stickyoils suchas mineral oil or lessgreasyoils suchas
sunfloweroil. This is doneprimarilybecause
of costdifferentialsaswell asto overcome
theundesirable
properties
of coconutoil suchasgreasiness,
its strongsmell,andfreezing
at ambienttemperatures.
This investigationis aimedat comparingthe effectsof thesetwo oils alongwith that of
coconutoil in preventinghair damagewhenusedasa preconditioner.
Althoughseveral
methodsinvolvingscanningelectronmicroscopy
(SEM)measurement
of combingforces
andtensilemechanical
properties
havebeenusedearlierto characterize
hair damage,we
haveusedprotein lossand water uptakemethodsfor this purpose.Furthermore,these
methodshavebeenextendedto studythe beneficialeffectsof theseoils in preventing
chemical,thermal,andUV damage.Efficacyof thesemethodshasbeenestablished
in an
earlierpaperfrom this laboratory(3).
MATERIALS
AND
METHODS
MATERIALS
Samples
of straight,curly,wavyandpermedhair of Indian originwereusedin thiswork.
The length of the Indian hair strandswas 25 cm.
178
JOURNAL OF COSMETIC SCIENCE
200-
i
176
173
17 165
i
160 -
120PROTEIN
LOSS
ug/g OF HAIR
}92
IN
92 86
135&116
80-
40-
i
COCONUT
OIL
SUNFLOWER
OIL
COCONUT
OIL
PRE-WASH
TYPES OF OILS
IBWITHOUT
SUNFLOWER
OIL
POST-WASH
EIWITH
Figure 1. Comparison
of proteinlossfrom undamaged
hair.
The reagentsfor protein estimationwereobtainedfrom SigmaChemicalCo. (St. Louis,
MO). The otherreagentssuchasbuffersand saltswereof analyticalgrade,whereasthe
oil sampleswereusedas they are availablecommercially.
METHODS
Sample
preparatio,.Hair tressesof 3+0.5 g were preparedfor this investigation.They
were securedat the root end by a crochetsothat they remainedfirmly in place,and not
a singlehair cameout of the tressduringexperimentation
(eitherbecause
of combingor
during the procedure).They were cleanedby soakingin 0.01% (w/v) of polysorbate80
(30 min at 28øC), de-ionized water at room temperature (severalrinses),and 0.01%
(w/v) of aceticacid (15 min at 28øC), in that order.Finally, they were extensivelyrinsed
in water and air dried.
Bleachedhair was preparedby using a bleachingkit containing30 vol. hydrogen
peroxideandammoniasolutionto adjustthe pH to -10. Fivemillilitersof thissolution
wasusedper tress(cleanedby the procedurementionedearlier),and the treatmenttime
was120 min at roomtemperature.With this treatmentthe tresses
becamelight brown
with
a red tone.
A boiling water treatmentwascarriedout for 120 min. The hair tresses
wereplacedin
EFFECT OF COCONUT
OIL ON HAIR
227
DAMAGE
179
.....................................
240
200
145
160-
PROTEIN
LOSS
uglg OF HAIR
139 145140
IN
120-
80
40
0
COCONUT
OIL
SUN FLOWER
PRE-WASHTYPES
BWITHOUT
COCONUT
OIL
SUN FLOWER
OIL
OF OILS
OIL
POST-WASH
DWITH
Figure 2. Comparisonof protein lossfrom bleachedhair.
a beakercontainingboiling distilledwater. The hair tresses
were immersedin it. This
wasnot doneto simulateany real-worldprocessbut in orderto createextremestressful
conditions.This was primarily done to assess
any impact on hair in water at high
temperature,as Indian consumers
largely usea hot water bath for hair.
In the caseof UV treatment,the hair tresses
wereexposed
to simulatedsunlightin a
xenostat,whereineachhair tresswasexposedat 50øCand 65% relativehumidity for a
periodof 300 hr. The tresses
wereturnedoverduringtheperiodof exposure
to attempt
a uniform exposureof all fibersto the radiant source.
In some caseshair tresses were treated with 0.2 ml of coconut oil/mineral
oil/sunflower
oil beforeexposure,
with the oil spreaduniformlyacross
the hair tressbeforeexposure
to UV light. In a few cases,the treatmentwith oil wascarriedout afterUV exposure.
The tresses
werestoredat roomtemperaturefor 48 hr beforethey were subjectedto
proteinlossdetermination.
This wasdesignedto simulatedensityof hair on scalpand
scalptreatments.
For the oil application,to eachhair tresswasapplied0.2 ml of oil (the quantity of oil
normallyappliedby an Indian hair oil user).It wasallowedto remainon the hair for at
least14 hr to simulateovernightapplication(the normalhabitof the Indianconsumer).
Thesehair tresseswere then subjectedto both protein lossand WRI tests.
The entire studyinvolvedsamplesof straight,curly, wavy,and permedhair of Indian
origin. Because
the numberof variableswashigh, i.e., the type of oil, type of hair,
180
JOURNAL OF COSMETIC SCIENCE
360 -
306
320 280240 -
PROTEIN
LOSS
ug/g OF HAIR
IN
200 160 120 8040-
0
•
COCONUT
OIL
I
I
SUNFLOWER
OIL
PRE-WASH
TYPES
l
[]WITHOUT
I
I
COCONUT
I
OIL
OF OILS
I
SUNFLOWER
OIL
POST-WASH
[]WITH
Figure 3. Comparison
of proteinlossfrom hair treatedwith boiling water.
sequence
of oiling, the total numberof oil applications,
and the numberof shampoo
applications,the studyhad becomequite complexin nature.In orderto simplifythe
complexityof the experiment,
i.e., to reducecost,time, andenergywithoutcompromising on the quality of results,a statisticaltool wasselected,termedthe Taguchi
Designof Experimentation.
Thisis a toolusedin research
anddevelopment
of products
in an engineeringindustrywherein,dependingupon the levelsand factors,an appropriatedesign,eitherorthogonal
arrayor factorialdesign,is selected.
Thishelpsto reduce
the numberof experiments
withoutaffectingthe result.Usingthis statisticalmodel,it
waspossibleto completethe entirestudyin the stipulatedtime framewithout losing
vital information,asit cut the numberof experiments
to be conductedfrom 14400 to
800 (considering
25 hairtresses
pervariable).As the experiment
wasquitecomplex,we
had to selectthe designof an orthogonalarray,L32, to conductthe experiment.The
designof experimentwasaspresentedin Table I.
The tresseswere wetted under running tap water (28øC) and washedwith a 20%
solutionof sodiumlaureth(3 molesof EO) sulfate(SLES).One milliliter of the solution
wasappliedper tress,and the tresses
wereworkedbetweenfingersto producea lather.
Followingthis, they wereextensivelyrinsedto removeall the SLESresidues.After this
treatmentthe tresses
were subjectedto the followinginvestigations.
Combingdamage.
The protein loss method of Sandhuand Robbins was used in the
followingmanner.Eachof the wet tresses
wascombedwith a fine-toothnyloncomb
(20-22 teeth/inch)50 times,rathervigorouslyalongthe entirelength of the tresson
EFFECT
OF COCONUT
OIL ON
HAIR
DAMAGE
181
440400
36O
32O
253
280
240
PROTEIN
LOSS
ug/g OF HAIR
IN
200
160
120
80
400
COCONUT
OIL
i
SUNFLOWER
COCONUT
OIL
PRE-WASH
TYPES
SUNFLOWER
OIL
OF OILS
[]WITHOUT
OIL
POST-WASH
[]WITH
Figure 4. Comparison
of proteinlossfrom hair exposed
to UV treatment.
bothsides.After everyfive strokes,the combwasdippedin 50 ml of watercontained
in a beakerto dislodge
the debris.The same50 ml of waterwasusedto collectall the
loosely
heldproteinelutedfromthecombfora giventress.Theentiretresswasdipped
in wateraftereveryfivestrokes
to collectthe damaged
anddislodged
cuticlecells.The
watersuspension
wastestedfor proteincontentusingthe Lowrymethod.It wascomparedagainststandard
bovineserumalbuminprocured
fromSigmaChemical
Co.This
bovineserumalbuminwasdilutedsoasto getreadings
withinwhichthemaximumand
minimumreadingfor the samplewouldfall. The methodinvolves
the formationof a
copper-protein
complex
in alkalinesolution
that,in turn,reacts
withphosphomolybdicphosphotungstate
reagent(Folin-Ciocaltaeu
Phenolreagent)to yieldan intensebluecoloredsolution,whichis analyzed
spectrophotometrically.
It waschecked
that the blue
colordevelopment
occurring
in bothstandard
andsamplewasof the samecolorwith
differentintensity,depending
on the amountof proteinbeingelutedfrom the hair
fibers,therebyindicatingthatnoneof theoilswasinterferingin the colordevelopment.
The methodology
is discussed
to a greatextentin reference
(2).
Water fete,rio, i,dex (WRI). The SLES-washed
tresseswere soakedin a 0.01% solution
ofpolysorbate
80 for 30 min.Followingthisprocedure,
theentiretresswasplacedover
a hollowglasscylinderwith a glasslid with perforations
to holdthetressproperlyand
to separate
the hair fromcapillarywaterin the glasscentrifuge
tubeof diameter3 cm
andheight8 cm.It wascentrifuged
at 8000 rpmfor 15 min to removecapillarywater
182
JOURNAL OF COSMETIC SCIENCE
PROTEIN
LOSS
IN
ug/g OF HAIR
200
COCONUT
OIL
MINERAL OIL
SUNFLOWER
OIL
TYPES OF OILS
[] NORMAL WITHOUT
[] NORMAL
[] BLEACHED
[] BLEACHED
WITHOUT
WITH
WITH
Figure 5. Comparison
of proteinlossfrom normalandbleached
hair in a salontrial.
andthenweighed.In thenextstep,thedryweightof thehairwasdetermined
bydrying
the tress in a vacuum oven at 50øC for 90 min, and then weighing it again. The
percentage
waterretentionindex(WRI) is givenby:
WRI -- (Wwe
t - Wary) 100/Wary
Half-headtests,
Eachhalf-headtest involved20 clientseachwith normalandbleached
hair.The hairwaspartedin the middleandhalfthe headwastreatedwith the respective
oil (3 ml approx.)and massaged
thoroughly,while the other half wasleft without
treatment.The oil wasleft on the hair for approximately8 hr. Then the hair waswashed
with warmwater(28øC,200 ppm hardness)
using20% SLES,andrinsedwell to remove
anyresidue.To avoidinherentdifferences
in damagefromleft to right side,the application of the treatment was randomized. Panelists with odd numbers were treated on the
left side, while thosewith even numberswere treated on the right side.
After shampooing
andrinsing,the hair wascombedwith a fine-toothcomb(separate
EFFECT OF COCONUT
OIL ON HAIR
Table
DAMAGE
183
III
Pair-Wise ComparisonData for Treatment Effectsfor Protein Loss(t-valuesat 95% confidencelevel)
Treatment
Undamaged--with and without MO (MO aspost-wash)
Undamaged--with and without CNO (CNO as
post-wash)
Undamaged--with and without SFO (SFO aspost-wash)
Undamaged--with and without MO (MO aspre-wash)
Undamaged--with and without CNO (CNO as
pre-wash)
Undamaged--with and without SFO (SFO as pre-wash)
and without MO
Treatmentwith boiling water--with
(MO aspost-wash)
Treatmentwith boiling water--with and without CNO
(CNO as post-wash)
and without SFO
Treatmentwith boiling water--with
(SFO as post-wash)
and without MO
Treatmentwith boiling water--with
(MO as pre-wash)
and without CNO
Treatment with boiling water--with
(CNO as pre-wash)
and without SFO
Treatmentwith boiling water--with
(SFO as pre-wash)
Treatmentwith bleachingagent--with and without MO
(MO as post-wash)
Treatmentwith bleachingagent--with and without
CNO (CNO as post-wash)
Treatmentwith bleachingagent--with and without SFO
(SFO as post-wash)
Treatmentwith bleachingagent--with and without MO
(MO as pre-wash)
Treatment with bleachingagent--with and without
CNO (CNO as pre-wash)
Treatmentwith bleachingagent--with and without SFO
(SFO as pre-wash)
Exposureto UV light--with and without MO (MO as
post-wash)
Exposureto UV light--with and without CNO (CNO as
post-wash)
Exposureto UV light--with and without SFO (SFO as
post-wash)
Exposureto UV light--with and without MO (MO as
pre-wash)
Exposureto UV light--with and without CNO (CNO as
pre-wash)
Exposureto UV light--with and without SFO (SFO as
pre-wash)
Straight
0.452
---
Wavy
--
0.106
1.779
--
-0.431
---
1.814
--
Curly
--
--
Permed
---
0.461
0.103
--
0.515
--
0.507
1.312
--
--
--
1.762
--
1.108
--
--
--
0.484
--
0.354
1.738
--
1.565
0.139
0.092
1.728
0.210
0.583
0.407
2.012
1.588
0.345
0.098
1.780
0.345
0.265
0.087
1.850
0.684
t theoreticalfor 48 degreesof freedomat 95% confidence
level = 1.645.
combfor eachside).After eachof the ten combingstrokes,both the hair and the comb
weredippedin 200 ml of distilledwater to recoverbrokencuticledebris.A total of 100
strokes(50 on eachside)wereapplied.The suspension
with cuticledebriswasusedfor
protein estimation.Analytical controlswere run in the form of determinationof the
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JOURNAL OF COSMETICSCIENCE
Table
IV
Analysisof VarianceData for Treatment Effectsfor ProteinLoss
Hair type
Sourceof
variance
Degreesof Sumof Mean F-Valueat 95%
freedom squares square confidence
level
Undamaged
Oil typeMO (straight,curly)
Between treatments
2
22.2
11.1
Experimental error
2
4.2
2.1
Undamaged
Oil type MO (wavy,permed)
2
12.4
6.2
Experimentalerror
2
7.2
3.6
Between treatments
Undamaged
Oil type CNO (straight,wavy) Experimentalerror
2
92.8
46.4
2
2.0
1.0
Between
treatments
5.3
1.7
46.4
Undamaged
Oil type SFO (curly, permed)
Between treatments
2
80.0
40.0
Experimentalerror
2
10.0
5.0
Boiled
Between treatments
Experimental error
2
2
32.4
4.6
16.2
2.3
7.1
Oil type MO (straight,curly)
8.0
Boiled
Between treatments
Experimentalerror
2
2
16.9
6.5
8.5
3.3
2.6
Oil typeMO (wavy,permed)
5.6
Boiled
Between
2
20.4
10.2
Oil type SFO (straight,wavy)
Experimental error
2
3.6
1.8
Boiled
Between
Experimental error
2
2
34.8
1.4
17.4
0.7
24.8
Oil type CNO (curly, permed)
treatments
treatments
Bleached
Between
Experimental error
2
2
4.2
4.2
2.1
2.1
1.0
Oil typeMO (straight,curly)
Bleached
Between treatments
2
12.5
6.8
1.2
Oil type MO (wavy,permed)
Experimentalerror
2
11.5
5.8
Bleached
Between
Experimentalerror
2
2
38.0
7.8
19.0
3.9
5.0
Oil type SFO (wavy,straight)
Bleached
Between
19.5
treatments
treatments
treatments
Oil type CNO (curly,permed) Experimental error
2
43.0
21.5
2
2.2
1.1
2
UV-Treated
Between
Experimental error
2
15.4
7.6
7.7
3.8
2.0
Oil type MO (wavy,permed)
UV-Treated
Between
2
22.2
11.1
6.5
Oil typeMO (curly,straight)
Experimentalerror
2
2.3
1.7
UV-Treated
Between
2
10.4
5.2
Oil type SFO (wavy,straight)
Experimental error
2
2.1
1.1
UV-Treated
Between
2
44.6
22.3
2
1.2
treatments
treatments
treatments
treatments
Oil type CNO (curly,permed) Experimental error
4.7
37.2
0.6
F theoreticalfor (2.2) degrees
of freedomat 95% confidence
level = 19.0.
residue
ofoilonthescalp
oftheclientafterrinsing,
andonlyafterensuring
zeroresidue,
the rinsingswere collectedin the mannermentionedabove.
Theoutcome
of theseexperiments
wasanalyzed
statistically
(takingintoaccount
the
meanandthestandard
deviation
ofthenumber
of replicates
forthesignificance
of the
treatment
effects
withinthe confidence
limits).SeeTableII for analysis
of variance
(ANOVA)
data.
EFFECT
OF COCONUT
OIL ON
Table
HAIR
DAMAGE
185
V
Analysisof VarianceData for Treatment Effectsfor Water RetentionIndex
Hair type
Source
variance
Degreesof
freedom
Sum of Mean F-Value at 95%
squares square confidencelevel
2
29.2
14.6
2
4.7
2.4
2
19.1
9.6
2
7.8
3.9
2
93.6
46.8
2
2.9
1.5
2
2
83.0
13.1
41.5
6.6
6.3
Experimentalerror
Boiled
Between
2
35.5
17.8
7.4
Oil type MO (straight,curly)
Experimentalerror
2
5.3
2.7
Boiled
Between
2
19.1
9.6
Oil type MO (wavy, permed)
Experimentalerror
2
7.8
3.9
Boiled
Between
Experimentalerror
2
2
20.4
4.2
10.2
2.1
4.8
Oil type SFO (straight,wavy)
Boiled
Between
2
33.7
16.9
21.1
Oil type CNO (curly permed)
Experimentalerror
2
1.7
0.8
Bleached
Between
Experimentalerror
2
2
4.2
4.5
2.1
2.3
0.9
Oil type MO (straight,curly)
2
2
15.3
12.3
7.6
6.2
12.4
4.2
Between
treatments
Undamaged
Oil type MO (straight, curly)
Experimentalerror
Undamaged
Oil type MO (wavy, permed)
Experimentalerror
Between
treatments
Undamaged
Oil type CNO (straight,wavy) Experimentalerror
Undamaged
Oil type SFO (curly, perreed)
Between
Between
treatments
treatments
treatments
treatments
treatments
treatments
treatments
Bleached
Between
Oil type MO (wavy perreed)
Experimentalerror
treatments
Bleached
Between
2
40.0
20.0
Oil type SFO (wavy, straight)
Experimentalerror
2
9.5
4.8
Bleached
Between
treatments
6.2
2.4
31.2
2.4
2
40.0
20.0
Oil type CNO (curly, permed) Experimentalerror
2
1.8
0.9
UV-Treated
Between
2
17.4
8.7
Oil type MO (wavy, permed)
Experimentalerror
2
8.2
4.1
UV-Treated
Between
2
23.4
11.7
Oil type MO (curly, straight)
Experimentalerror
2
2.8
1.4
UV-Treated
Between
Experimentalerror
2
2
12.4
2.8
6.2
1.4
4.4
Oil type SFO (wavy, straight)
UV-Treated
Between
Experimentalerror
2
2
41.6
1.6
20.8
0.8
26.0
Oil type CNO (curly, permed)
treatments
treatments
treatments
treatments
treatments
22.2
2.1
8.3
F theoreticalfor (2.2) degreesof freedomat 95% confidencelevel = 19.0.
RESULTS
PROTEIN
AND
DISCUSSION
LOSS
The process
of cuticlechippingthat resultsfrom abrasionof hair againstobjectssuchas
groomingdevicesor evenotherhair is a major factorin hair damage.The proteinsthat
constitutethe cuticle cells are lost during wet combing.It is well known that wet
186
JOURNAL OF COSMETIC SCIENCE
15.3
5.•13.8
•'t14.1
14.9
145
12
% WATER
RETENTION
INDEX
• :::: ß .•_,?..'..•,•
•'-•..
•:.
i
i
OIL
OIL
PRE-WASH
TYPES
ltllWITHOUT
,}•{•'
.
SUNFLOWER
COCONUT
.
I
COCONUT
OIL
OF OILS
I
SUNFLOWER
Oil
POST-WASH
[3WITH
Figure 6. Comparison
of waterretentionindexfor undamaged
hair.
combingis accompanied
by the breakingof the surfacecuticlecell because
of its
brittleness.Histologically,the major componentof the cuticle cell consistsof the
exocuticleandthe endocuticle.
The exocuticle,beinghighlycross-linked
is not swollen
by water.The endocuticle
and the cell membranecomplex,on the otherhand,areless
cross-linked
andaremorevulnerableto swellingdamage.This leadsto the lifting of the
surface
cuticlevia bending.Suchcuticlecellscanbe brokenin the process
of combing
or teasing.The proteinlossobserved
in thesemeasurements
resultsmostlyfrom the
cuticularregion.Because
of theshorttimeinvolvedin thecombingandbriefimmersion
of the combedtressin water,it is unlikelythat proteinsfrom the bulk of the fiber are
involved
in this measurement.
The datafor proteinlossmeasurement
for undamaged
anddifferentlydamaged
hair are
shownin Figures1-4. The barson theleft referto testswhereoil wasusedasa pre-wash
conditioner,whereasthoseon the right arefor the testsinvolvingpost-washtreatments
whereoil wasappliedafterdryingthe hair.The datain Figures1-4 clearlyshowthat
theperformance
of coconut
oil in reducingproteinlosswasbetterthanthat of mineral
andsunfloweroils.Coconutoil performedbetterasa pre-washratherthan a post-wash
conditioner.
This showsthe importance
of lubricationvs reductionin the swellingof
the cuticlecellsthat leadsto their breakingin wet combing.The differencebetween
EFFECT
60-(
OF COCONUT
i•
ß
45
52 3
OIL ON
•[• 52 4
.?•
.
•
ß
'•
SUNFLOWER
OIL
PRE-WASH
TYPES
J
'50.9"",
•
COCONUT
OIL
187
52 3
' 0.4 'i'
{
INDEX
DAMAGE
•
.{
RETENTION 30
HAIR
COCONUT
OIL
SUNFLOWER
OIL
OF OILS POST-WASH
BWITHOUT
E3WITHJ
Figure 7. Comparisonof water retentionindex for bleachedhair.
coconutoil andmineraloil is probablydueto the differencein their ability to penetrate
the hair (4). The smallereffectof sunfloweroil may be due to the presence
of unsaturationin the molecule.No informationregardingthe penetrabilityof sunfloweroil in
the hair is available.The sameeffectwasseenin the half-headtest in a salontrial, asseen
in Figure 5.
The effectof variousoilsin preventingcuticledamagein laboratorytestswasestablished
statisticallyby a parametrictest,t-test. The outcomeof the analysisis shownin Table
III. The t-valuesclearlyindicatethat damagedaswell asundamagedhair benefitsfrom
applicationof coconutoil asa pre-washconditioner,whereasin the caseof sunfloweroil
and mineral oil, there was no effect.The effectsof coconutoil were alsopositivein a
salontest.In both normalandbleachedhair, treatmenteffectsin reducingproteinloss
weresignificant,whereasthe samefindingswereabsentin the caseof mineral oil and
sunfloweroil. The valuesof t for coconutoil are statisticallysignificant,whereasfor
mineral oil and sunfloweroil, they are not.
SeeTablesIV andV for ANOVA data for treatmenteffectsfor proteinlossand water
retention
index.
188
JOURNAL OF COSMETIC SCIENCE
24.2
% WATER
RETENTION
INDEX
10-
COCONUT
SUNFLOWER
OIL
OIL
PRE-WASH
TYPES
•WITHOUT
COCONUT
SUNFLOWER
OIL
OF OILS
OIL
POST-WASH
EIWITH
Figure 8. Comparisonof water retentionindexfor hair treatedwith boiling water.
WATER
RETENTION
INDEX
The waterretentionindexfor undamaged
hair is shownin Figure6. Fromthe datait can
beseenthatcoconutoil reduces
theWRI of undamaged
hairby 44%, whereas
in the case
of mineraloil and sunfloweroil, thereis hardlyany reductionin WRI, asseenin Figure
6. The ability of coconutoil to penetratehair (4) supportsthis observation.
The data for the bleached,heat-damaged,
and UV-damagedhair are shownin Figures
7-9, respectively.
For thesedamagedsamples,the WRI is muchhigherthan that for the
undamagedhair. This is mostlydue to the chemicaldegradationof proteins,generating
hydrophilicgroups.Both the cleavageand oxidationof disulfidebonds,followedby
their oxidationto cysteicacid, as well as hydrolysisof the peptide linkage, occur,
althoughthe contributionof the latter is probablyminor. All samplesshowa reduction
in the WRI asa resultof the applicationof coconutoil, whereasthe samefindingswere
not observedto a significantlevel in the caseof mineraloil and sunfloweroil. Assuming
that mostof the wateris absorbed
by the fiber, the WRI reflectsthe swellingpropensity
EFFECT OF COCONUT
i59.8
ß
OIL ON HAIR
DAMAGE
61.2
189
61.2
•,..•8.7
5
57.5
60
x::":•
% WATER
RETENTION
40
INDEX
20-
SUNFLOWER
OIL
COCONUT
OIL
PRE-WASH
TYPES
COCONUT
SUNFLOWER
OIL
OF OILS
EIWITHOUT
OIL
POST-WASH
EIWITH
Figure 9. Comparisonof water retentionindex for UV-treated hair.
of hair. Sincerepeatedswellingand contractiondamagesthe cuticle,reductionin the
WRI can be considered
as beneficialin reducinghair damage.
The datain Figures6-9 showthat the sequence
of application(whetherpre- or postwash) is important. Post-washapplicationis lesseffectivein reducingthe WRI as
comparedto pre-washapplication.The differenceseemsto be in the locationof the oil
residues
andtheir ability to counteract
surfactantdamage.In post-wash
applicationthe
oil film is on the surface,
with nopenetration
into the fiber.In pre-wash
application,
it
ispossible
that the molecules
of the oil penetrateinto the cuticleandprobablyeveninto
the cortex.This may alsobe the casewith undamagedhair, althoughthe effectis small.
The reductionin the WRI mustbe dueto the introductionof the hydrophobic
triglyc~
eride into the keratin
structure.
SeeTableVI for pair-wisecomparison
of treatmenteffectsfor waterretentionindexdata.
MECHANISM
OF PROTECTION
BY COCONUT
OIL AND
NOT
BY MINERAL
OIL AND
SUNFLOWER
OIL
The histologyof a cuticlecellandthe mechanism
of damagein wet combingisproposed
by Swift (5,6) Because
of cross-linking,
the exocuticleis brittle anddoesnot swell.The
190
JOURNAL OF COSMETIC SCIENCE
Table
VI
Pair-Wise ComparisonData for Treatment Effectsfor Water RetentionIndex (t-valuesat 95%
confidencelevel)
Treatment
Straight
Wavy
Undamaged--with and without MO (MO as post-wash)
Undamaged--with and without CNO (CNO as
post-wash)
Undamaged--with and without SFO (SFO as post-wash)
Undamaged--with and without MO (MO as pre-wash)
Undamaged--with and without CNO (CNO as
pre-wash)
Undamaged--with and without SFO (SFO as pre-wash)
Treatmentwith boiling water--with and without MO
(MO as post-wash)
Treatmentwith boiling water--with and without CNO
(CNO as post-wash)
Treatmentwith boiling water--with and without SFO
(SFO as post-wash)
0.41
--
Curly
Permed
O.O9
1.87
--
--
--
O.36
--
O.O9
O.34
--
1.98
O.34
__
0.43
1.21
1.89
1.02
Treatmentwith boilingwater--with and without MO
(MO as pre-wash)
Treatmentwith boiling water--with and without CNO
(CNO as pre-wash)
Treatmentwith boilingwater--with and without SFO
(SFO as pre-wash)
Treatmentwith bleachingagent--with and without MO
(MO as post-wash)
Treatmentwith bleachingagent--with and without
0.24
0.13
1.85
1.43
0.06
0.12
1.87
CNO (CNO as post-wash)
Treatmentwith bleachingagent--with and without SFO
(SFO aspost-wash)
Treatmentwith bleachingagent--with and without MO
(MO aspre-wash)
Treatmentw•th bleachingagent--with and without
0.12
0.46
O.47
2.12
CNO (CNO as pre-wash)
Treatmentwith bleachingagent--with and without SFO
(SFO as pre-wash)
Exposureto UV light--with
post-wash)
Exposureto UV light--with
post-wash)
Exposureto UV light--with
post-wash)
Exposureto UV light--with
pre-wash)
Exposureto UV light--with
pre-wash)
Exposureto UV light--with
pre-wash)
1.45
and without MO (MO as
0.21
0.098
and without CNO (CNO as
1.85
and without SFO (SFO as
0.32
and without MO (MO as
0.19
0.09
and without CNO (CNO as
1.97
and without SFO (SFO as
O.43
t theoreticalfor 48 degreesof f}eedomat 95% confidence
level = 1.645.
endocuticleand the cell membranecomplexhavelesscross-linkingand thereforeswell
significantly.This effectproducesthe tendencyfor the surfacecuticle cells to curve
upwardand breakwhen pressureis appliedwith a comb.
Recentstudiesof Ruetschand Weigmann(7) confirmthat the endocuticleandthe cell
EFFECT OF COCONUT
OIL ON HAIR
DAMAGE
191
membranecomplex(CMC) are the foci of weaknessand that the cuticle cell often lifts
and fractureswhen the fiber is extended.Chemicalmethodsimpair the adhesionby
weakeningthe cell membranecomplexbetweenthe cuticlecells.The degreeof swelling
of the cuticlelayersis increased
by disulfidecleavageand oxidation.This enhances
the
combingdamageandproteinloss,especiallyin wet combing,asobservedin this study.
Coconutoil is mostly a triglycerideof lauric acid and is hydrophobic.Application of
coconutoil asa pre-washconditionercoatsthe hair andinhibitsthe penetrationof water
into the hair. A smallpart of it is alsoabsorbedinto the hair during the washwhen the
fiber is swollen.Introductionof this hydrophobiccomponentreducesthe swelling
propensityof the cuticle,which limits the upwardcurvingof the surfacecuticle.This
reducesthe chippingawayof the cuticlecells,which reduces
proteinloss,asobservedin
this work.
Becauseof the low molecularweight of coconutoil, it penetratesthe cortex,whereas
mineraloil, beinga hydrocarbon,
doesnot penetratethe hair at all. This hasbeenshown
in the earlierstudy (4). It is possiblethat sunfloweroil doesnot penetratethe fiber
becauseit hasa bulkier structureas a resultof doublebondsin the fatty acid chain.
Coconutoil triglyceridehas a linear structure,which is why it solidifiesat room
temperature,whereassunflowertriglyceridehasan irregularball-like structurebecause
the fatty acid chainsfold on themselves
due to oneor two doublebonds.This is why
sunfloweroil is a liquid at room temperature.It is likely that it doesnot penetratethe
fiber aswell asthe coconutoil. This may be the reasonwhy the WRI is low for coconut
oil as comparedto mineral and sunfloweroils.
CONCLUSIONS
This studyhasfirmly established
the superiorityof the protectiveeffectof coconutoil
on hair damagein grooming processes
when it is used as a pre-washconditioneras
comparedto mineral oil and other vegetableoils suchas sunfloweroil. It not only has
a protectiveeffecton undamagedhair but alsoon chemicallytreatedhair, UV-treated
hair, and hair treatedwith boiling water (i.e., hair in water at 100øC for 2 hr). The
ability of coconutoil to penetrateinto hair cuticleandcortexseemsto be responsible
for
this effect.Coatedon the fiber surface,it can preventor reducethe amountof water
penetratinginto the fiber and reducethe swelling.This, in turn, reducesthe lifting of
the surfacecuticleand preventsit from being chippedaway during wet combing.A
reductionin the WRI is additionalevidenceof its efficacyin decreasing
waterabsorption. The datapresentedin thiswork clearlyshowthe superiorityof coconutoil asa hair
damageprotectant,in the groomingof untreatedor damagedhair.
ACKNOWLEDGMENTS
The authorsthank the management
of MaricoIndustriesLtd. for providingan opportunity to work on this project, and Dr Yash Kamath, Director of Research,T.R.I.,
Princeton,New Jersey,for his valuableguidancein writing this paper.
REFERENCES
(1) M.L. Garcia and J. Diaz, Combabilitymeasurements
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379-398 (1976).
192
JOURNAL OF COSMETIC SCIENCE
(2) S.S. Sandhuand C. Robbins,A simpleand sensitivetechnique,basedon protein lossmeasurement,
to assess
surfacedamageto humanhair,J. Soc.Cosmet.
Chem.,44, 163-175 (1993).
(3) A. Rele, Effectof coconutoil on preventionof hair damage.Part I,J. Cosmet.
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(4) S. B. Ruetsch,Y. K. Kamath, A. S. Rele, and R. B. Mohile. Secondary
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to hair damage,
J. Cosmet.
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of
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