Gelatin and shellac properties and characteristiscs

Gelatin and shellac properties

1. GELATIN
Gelatinisamixtureofreversiblegel-formingproteins
derivedfromcertainanimaltissues,particularlyskin
andboneswithhotwater.

2. PREPARATION
Pretreatmentstomaketherawmaterialsreadyforthe
mainextractionstepandtoremoveimpuritieswhich
mayhavenegativeeffectsonphysiochemicalproperties
ofthefinalgelatinproduct,
Themainextractionstep,whichisusuallyperformed
withhotwaterordiluteacidsolutionsasamulti-stage
extractiontohydrolyzecollagenintogelatin,and
finally,

3. Therefiningandrecoveringtreatmentsincluding
filtration,clarification,evaporation,sterilization,
drying,grinding,andsiftingtoremovethewater
fromthegelatinsolution,toblendthegelatin
extracted,andtoobtaindried,blendedandground
finalproduct.

4. Theprocessconvertsinsolublecollagensinto
solublegelatinthesolutionofwhichisthen
purifiedandconcentratedtoasolidform.
Iftherawmaterialusedintheproductionof
thegelatinisderivedfrombones,diluteacid
solutionsareusedtoremovecalciumandother
salts.
Pretreatments

5. Hotwaterorseveralsolventsmaybeused
inordertoreducethefatcontent,which
shouldnotexceed1%beforethemain
extractionstep.

6. HYDROLYSIS
Collagenhydrolysisisperformedbyoneofthree
differentmethods:acid-,alkali-,andenzymatic
hydrolysis.
Acidtreatmentisespeciallysuitableforlessfully
crosslinkedmaterialssuchaspigskincollagenand
normallyrequires10to48hours.

7. Alkali treatment is suitable for morecomplex
collagensuchasthecollagenfoundinbovine
hidesandrequiresmoretime,normally
severalweeks.Thepurposeofthealkali
treatmentistodestroycertainchemical
crosslinkagesstillpresentincollagen.

8. Enzymatichydrolysisofcollagenforgelatin
extractionisrelativelynew.However,thetreatment
timeisshorterthanthatrequiredforalkali
treatment,andresultsinalmostcompleteconversion
tothepureproduct.
Thephysicalpropertiesofthefinalgelatinproduct
arebetter.

9. Twotypesofgelatinarecharacterizedin
theBP
typeAisobtainedbypartialacid
hydrolysis of animal collagenand
typeBbypartialalkalinehydrolysis;
Mixtures of both types are alsopermitted.
Two types ofgelatin

10. Characters
Sheetgelatinpreparedasabovemaybecutinto
strips or made into a granularpowder,
Gelatin is colourless or pale yellow, is translucent
and has little odour ortaste,
Itisinsolubleincoldwaterbutabsorbsa
considerable volume ofliquid;
it dissolves on heating and a 2% solution forms a
jelly oncooling.
Thegelatinizingpowerofgelatinisreducedby
longboiling.

11. Thequalityofgelatinislargelyjudgedbyits'jelly
strength'or'Bloomstrength'whichisdeterminedbya
Bloomgelometer.
TheBPspecifiesjellystrengthforgelatinwhichisto
beusedinthepreparationofsuppositoriesand
pessaries.

12. CONSTITUENTS
Gelatin consists mainly of the protein glutin andtherefore
gives the usual tests forproteins,
Tests
1.itevolvesammonia
(distinction fromagar);
whenheatedwithsodalime
2.withmercuricnitratesolutiongivesawhiteprecipitate
that turns brick-red onwarming;
3.it gives a precipitate with a solution oftrinitrophenol.

13. APPLICATIONS
Gelatinisusedinthepreparationofpastilles,pastes,
suppositories, pessaries, capsules, pill-coatings and gelatin
sponge,
Speciallypurifiedandpyrogen-freegelatinsareavailable
for intravenousinjection,
andagradewithhigh'Bloomstrength'isusedformaking
gelatin capsules and for bacteriological culturemedia.

14. It is used profusely in food products e.g., fruitjellys;
inthepreparationsofpharmaceuticaldosageforms
e.g.,soft-gelatinecapsulesforVitaminE,garlic
pearlsetc.,
andhard-gelatinecapsulesforchloramphenicol,
tetracycline,acetamenophen(paracetamol).

15. Gelatinisalsoemployedasavehicleforsomehighly
specificpharmaceuticalinjectionse.g.,Pitkin’s
menstrum—whichcomprisesofheparin,gelatin,
dextrose,aceticacidandwater.(anticoagulant
therapy)
Gelatinisalsousedforthetreatmentof‘brittle
fingernails’,and‘non-mycoticdefects’ofthenails
inhumans.

16. TypesofGelatin:Gelatinisnormallyavailable
intwodistinctforms,namely:
(a)AbsorbableGelatinSponge:Itisasterile,
white,tough,andfinelyporousspongy,water
insoluble,andabsorbablesubstance.
Eventhoughitiswater-insolublebutitis
adequatelyabsorbedinbodyfluids.
Nevertheless,itusuallytakesuptonotlessthan
30foldsitsequivalentweightofwater.
Ithasbeenobservedthat9gofabsorbable
gelatinspongetakesupto405g(i.e.,45times)
ofwell-agitatedoxalatedwholeblood.

17. Thevarioususesofabsorbablegelatin
spongeareasfollows:
Asaneffectivehaemostatic,asalocalized
anticoagulant,andWhenplacedupona
surgicalincisionafterbeingdulymoistened
withsterileNaClsolution,itgetsslowly
absorbedwithinaspanof4-6weeks.

18. (b)AbsorbableGelatinFilm:
Absorbablegelatinfilmreferstoalight
ambercoloured,sterile,non-antigenicthinfilm
invariablyproducedfromanespecially
preparedgelatin-formaldehydesolutionby
carefuldryingfollowedbysubsequent
sterilization.

19. Shellac

20. Synonyms Lacca;Lac.
BiologicalSources
ShellacistheresinousexcretionoftheinsectLaccifer
(Tachardia) laccaKerr,
belonging to family:Coccidae.
Theinsectsusuallysuckthejuiceofthetreeand
excrete ‘stick-lac’ more or lesscontinuously.
Shellac

24. The various host trees are, namely: Buteafrondosa
Koen. ex. Roxb. (Family:Leguminosae)
and Butea monosperma (Lam.) Kuntze; Aleurites
moluccanna (L.) Willd. (Family:Euphorbiaceae)-
Varnish Tree; Ficus benjamina Linn.,(Family:
Moraceae);
Zizyphus jujuba (Lam.) (Family:Rhamnaceae).
However, the whitest shellac is produced whilethe
Kusum tree is the host i.e., Schleichera trijuga
(Willd.) (Family:Sapindaceae).

25. PREPARATION
Theresinwhichisstuckonthesmallertwigsand
branches is normally scrapped by means ofknives.
Theresultingresinissubsequentlypowderedand
extractedeitherwithwaterorwithalkalinesolution
soastoremovethecolouringmatter.
Theresidualproductisdried,meltedinnarrowbags
suspendedoverafire.

26. Thecontentsofthebagsi.e.,themolten
shellac,aresqueezedoutmechanicallysoasto
forcetheliquidshallacthroughtheclothonto
apreviouslycleanedsurfaceoftilestoobtain
theproductasflatcakes.

27. The product may also be obtained as thinsheets
by stretching the semi-cooled product on the
tiles with the help of a scrapper (orspreader).
The thin sheets thus obtained get hardened
after cooling and are subsequently broken upto
obtain the flakes of shellac for the commercial
market.

28. Shellac is a brittle, yellowish,transparent/translucent
sheets or crushed pieces orpowder.
It does not has any specific odour andtaste.
Its mp is 115-120°C and d 1.035-1.140.
Itssolubilityinalcoholis85-95%(w/w)(veryslowly
soluble);inether13-15%;inbenzene10-20%andin
petroleumether2-6%.
CharacteristicFeatures

29. It is sparingly soluble in oil ofturpentine.
Itispracticallyinsolubleinwater,butsolublein
alkalinesolutions,inaqueoussolutionof
ethanolaminesandinboraxsolutionswithslightly
purplecolouration.

30. CHEMICALCONSTITUENTS
Themajorcomponentofshellacisaresinthaton
beingsubjectedtomildhydrolysisyieldsacomplex
mixtureofaliphaticandalicyclichydroxyacidsand
theirpolyestersrespectively.

31. Themajorcomponentofthealiphaticfractionis
aleuriticacid,
whilethemajorcomponentofthealicyclicfractionis
shellolicacid.
However,italsocontainstheisomersofshellolicacid
alongwithsmallamountsofkerrolicacidand
butolicacid.
Thecolouringmatterisduetothepresenceoflaccaic
acid, which is watersoluble.

32. Uses
It is used chiefly in laquers andvarnishes.
It is also employed in the manufacture of buttons, sealing
wax, cements, inks, grinding wheels, photographrecords,
paper.
Italsofindsits
stiffeninghats.
useinelectricalmachinesandfor

34. It is also used for finishingleather.
It is extensively used for coating tabletsand
confections.
It has also been used for preparingsustained
release medicamentformulations.