Tobacco Documents Online

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E !i Experiments ¢ayrled out in the laboratory uslng V~io~s ~hemIc~l compound8 ~ n~1 m~t~lal6 as ~oten~lal smoke-s~oothlng agents indicated ~entho1 as the moat p~omlsing additive. However the use of free menthol at any level of doa~ge Involves heavy 1o8~es due to its high d~gree of volatility resulting in unpredictability of the actual l~vel in the flnlshed product, Attempts to use ~he ~iorc stable I~enthyl d~rivatlv~s ~ menthol~h~ectant m~xt~res were unsatisfactory and in most ~xte~ive t~st8 ca~ied out ~ith micro-~n~apB~late~ Blurricd menthol o~ tobacco in the 5-~0 mic~on~ ra~l~e Sh~d ~tability appreciably grea~er than fr~e menthol and gaveJhighly ~Igni~ica~.t results for both 11I~tI~ ~ tb~oa~ ~'Ir~It~tlo~'t in cigarettes u~ing a tralne~ panel - th~ t~eate~ ciga~tt~ being Considered lower fo~ both th~$~ ~acto~ duriD~ ~moki~g~ A "s~b-~cOg~lltioz threshold" valu~ fo~ ~ncaps~lat~d m~thol was ~tab]i~he~ and i~ repo~ted ~ere fop th~ ~ir~ time. There l~ ~o~ evidence to ±hdlcate that application at th~ s~b-recogn±tion threBhold level viz. 150 p~ts per million intended, ~e~ults in a predictable level o~ a~prox~mately ~G0 p-p.m, of menthol in the finished product at which point a significant reduction in ~o~e irritant ~ensations is indlcated. ~±h¢~ t~ capsule wal~ is nonvo1~t11~7~caps~lated flavo~r~ wo~ld be cla~d as additives ~n~or th~ p~es~n~ 570~3952S

IN=~T~OD~CTION T~c ~se Of "smoke-smoothlng'~ a~ents a~ additives in tob&c~o p~oduct~ is of inoPeasin~ Importance ~o the tobecco Industry. Ovsp a period of %Im~ VaP~oll8 additive~ n~tupal 8~d Bynthetlc~ were tested in ~he laboratory as potentlal ~ok~- s~oothing agents, amon~ the~ me~thol~ which at low leve~s was c~nsidePed the most promlsing. The us~ Of ~pee mentho~ at sr4y level of addition ha~ several dlsadvanta~es - its hlghdegree of vol~tility, oontamlnatlon in cigarette manufact~rin~ pooms~ etc, A s~PVey of th~ patent litep~tu~ showed vaPio~s ~e~hods Of stabillsing menthol (I-7) by way of d~rlvativ~s which are claimed to overcome these disadvantages ~nd uniformly ~el~ase menthol ~rln~ smoking thus implying that the aopllcatlon of free menthol PesulSs in n non-unlform r~lease duPin~ ~moking. ~om~ ~xRmples of ~tented mel!thyl d~Pzvative$ ape ~thyl ethers, ¢aPbO~tes~ C]~t~P~tcs# s~eci~ates~ be~tes~ acct.]8 8~d !~o~st~p~, Tests carried ou~ in this l~boPa~oPy with free menthol, free menthol-h~ect~nt mixture~ and selected menthyl estep~ did no~ i~di~ato any improved@n% oP ovid~ Of f~xation. T~ Vas~ majority o~ patc~ted menthyl dorlvstlves were discounted o~ the basis Of ~conomic~1 preparation (commercially not ~vailabl~). ~Jero-enc~p~l~tlo~, b~s~cslly ~ process o~ wrapping fine psrtlcle~ or dPopiet~ in a prot~otiv~ jacket was first introduced in ~he I 950's by N~tion~l Cssh ~egister }I,C.R,) in the form of N.C.~.~S copy psper sJ.so eal~cd N.C.R. No carbon required) under their basic U.~,i, patents ~,800,&57 and ~#800,~58, Coverln~ scvor~l processes and prod~c~s, By 1963 ~r~ynew ~pplic~tions weP~ found for mioro-8~¢apsulstion Of widc variety of ~aterlals, The application of micro-enaap~ul~tion to flsvours both in powder and slurry form ~s s~en ~t first hand International Flavours & VrsgPauc~e (T.P.P.), New York[~) and the potential of this form of additive and in particular encapsRlated mentho~ as a tobacco additive waB noted. A throe-stage approach to the study of micro- encapsulated menthol was pla~ed. The firststag@ Involved actual preparation u~ micro-~nc~psulated menthol in the laboPato~ in sluprl~d form within the S-40 microns ra~g~. Afte~ a st~d~~ o~ varlou~ patented pPoce~s~ of eneapsulatlo~ (9-15), an aqueous phase separation proce~ ~ras selected as bein£ the mo6t suitable for menthol as per N~C.R,'s British patent 1,171,~3. The second stage involved micro-encapsulation of • ~It~hol ~d ~ 8~ta~e R~seapch D~p~pt~e~t ~o~aPin s~bstit~t~ in the same micPoca~s~l~. ~h~ final stage involved ~pplicat~o~ OT encapsul~ted menthol in slurried fol~ %0 cigaPette~ with a View ~o establishiD~ a "~ub~r~ce~n[tion threshold" v~lue. I. ~r 570.5395Z6

[ £. a. f, F !" In all experimental trials menthol captiff slurry VC-20~006 obtained from I•F.F. New York, was used. ~e ~ethod of prepaPing micro-encapsulants is covered by ±nternatione~ pa±entB (~.C.R.). Briefly the I.F.F. neat slurry comprises of 81% water. 2% wall material and 17% internal phase, the latter eontainlng the menthol and representing I0.~ w/w of the total slurry* Since the capsule wall is non volatile encapsulated flavours would be classed as additives 1~Judez, the present Customs ~nd Excise rules. T~EORETIC~ CONSID~LTION8 ~ubjective test~ r~ther than objectlve methods were considered desirable in order to establish that the encapsulated menthol was released during smoking and also to obtain a 'threshold' level. Objective measurements were not carried out because it has already been established that the capsule wall is stable up to 300~ and releases the internal phase i.e. menthol, on pyrolysis during smoklnE (14) , Although a consldera~le amount of work published in th~ literature has been devoted to threshold val~e determinations of flavour compound8 Inost a~thors do not qualify or define ~threshold~ in their papers, For the purpose of this iuvestigation it was decided to establish a "sub-recognition threshold~ for encapsulated meuthol because of the eharacteristlc "cool~ property of menthol which m~kes It insLsntly recognizable and identifiable, "~ub-~ecogn~tion threshold" is therefore defined here as the lowest concentration (p.p°~.) of an additive ot which a statistically significant a~ITerence is obtained between the treotedand control tobacco product without rceegn~tlon of the additive itself o~ ire specific and characteristic effect being commented on by a wane! of smokers. ~V~th regard to menthol, this is best represented as ~er;- Npn-mentholated~ I~ )l~enthol~ No j: Differenoe Differenoe Obvious clgaPet~ (0 p.p.m.) difference without with dlffere~o~ ( recognition recogniti~ and ) recogn~on Sub-re ¢ o~I i t ion ~scognlti on Po~t ~r~cog~itio~ threshold ~bre~hold threshold AS C~l be seen f~om the obeys t~e objective was to determine the level Of menthol required to impsrt ~ s~oke- smouthing effect ~.e. ~ ~ed~ctlon in ~rr~tati0n or h~rslules$, without the menthol, being rec~nli~d ~s such or ~ts coolin~ e~f~et experienec~ by th¢ s~okcP. A further consid~r~tio~ was to ensure that the s%abillty of encapsulated menthol ~e appreciably ~reater than that of free menthol. 2.

p~ ,PARTI t EXPERImeNTAL P~eD~ration of micro-encapsulated menthol (A) Commercial method (N.C.R.I In aqueous phase s~paration processes, a polymeric or macr~olec~lar wall material is dissolved, Qr dispersed as a sul, in water• The core mat~ria! to be encapsulated, which must be immiscible with water, is dispersed in partlculate form throughout the aqueous phase by s~irrlng. Wall formation occurs when the wall material is caused to chase out and envelop the core purtlcle~ by s suitable change in the system e.g. temperature, ~.d, dilution, etc. In the encapsulation of menthol the walk material, a mixture of gelatin and gum acacia (gum arabic) is phased out of aqueous solution by dilution, as a concentrated liquid phase or coacervate which forms a unifcrm liquid coatinE around the menthol. On further processing the gelatin-gum arabic complex is hardened to form a soli~ wall around the menthol. Th1~ method is given in British patent 1,171,043 and is diagramatically represented overleaf.

i w AQU¢O~ phase ~aration Process a~ per N,C.R, Patent - | lhexadec~lol mixture.~ Emulsify 5-&O~) s~irred until particle size I297 g ef gum "I aeocin diesolved in ~03 ml of deionieed w~ter. Mix pH of resultent mixture adjusted to solution 4.8 with I~ Na0H I v6OOe0r mlt °~8 od~i.°nlsed] All ingredients ............................................... above ~hls line ,~aintalned at p!ixture cooled on a] 38 - 40°C, water bath ~o 27°C [14S.5 ml o~ a 25% ]i ' "' solution of glutar- aldehyde in ~ ater v , 1 CAPSULES (Separations and drying (Slurry) atagea optional) $705S952{)

i* !, v, (BI P~pch D~Da~tm~t triable Na{crials used~- F4entho] C~lat in Gu~: acacia Veg~ L~blc oil Hoxadscanol Glut sraldehyde B.D.H. crys ~al llne ~.D.H. powder Hopkins ~ !&llls~$ powd@r B.D.H. tecbnleel cetyl alcohol Xoch-Li~h~ 25~ glutar~ldehyde in l~itl~l ex~i~e~%z were c~rried Out fcll~#li~ %he N,C.R. method~ using 1/50 of the quantlti~e given in the patent. A ratio of 90:10, Nazola oi~ to cetyl ~Icohol ~as fo~d to be the best combination for the mentho~ solution. A top-drive macerator was used fez, preparing t~e C~ulsiou ~nd subse~le~t ~ixing, Par~icl~ size was ~oqitor~d by microscopic ~x~n&tien. ~ollowin!~ th~ pz~oc~s it was fon~d th~ after th~ ~m ac~cla had been added ~o the emulsion, the pH Of the resultant mixtur¢ wa~ already 4.9 which m~d~ ad~ustmen% with 10% NaOH u~nece~sary. After completion of the p~.oc~s~ ~he prodllct w~s e~ed ~d~r the mic~co~ ~nd ~o~a~ed with ~he I,~,~, c~p~nl~s. The latter, ~hlch fell ~ithln the 5-~Q microns razg~ ~r~ distlnctly ~'oran~ and lemon~ shaped and with gent~ pressure o~ the cover slip tended 50 r~ture~ t~o contents oozing o~t l~aving ~he ~m~ty capsule shell behind, ~ix~uni~at~on of the ~se~rch D~p~rz~ilt p~duct ho~o~cr showed that enc~s~latio~ was not ~chieved but had r~slllt~d i~ spherienl globules only, which i~nder ~entle p~ssuro ~crged together to fo~ la~e~ glob~l~s° The ~lOb~les iz ~act r@pre~nSed emulsio~ o~ly, wall f~rmation ~ot ]~ving taken place. On a~andln~, th~ ~es~ar~h Department p~oduct g~ll~d to a solid mass T~ich COUld not b~ broken up On stirring. cover slip a~d viewi~ the ¢onte~ts ~uuder the ~leroscop~ w~ ~dopted as a simple b~ ~ff~ctive t~chnique ~o~ determining w~ether Or not enoa~sul~tioz had t~k~n ~lac@. (G) ~pdifled ~cseaFqh DeDartmg~t method ,~ 71~Dn~ the sev~r~l factors Coil$i~K'~d PesponSl~i8 9Op tNe non-encapsulation in the ini%isl t~ials above, the following two were p~psued:- (I) Type and souses el gelatin end gum acecis. (2) ~. (I) Gelatin and ~pm ~ca~ia Samples of various types and grades of gelatin ~d ~] acacia w~re purchased from different chemical 8~ppl~ers ~d each Was ~se~ i~ ~n i~ the e~cspsulstlon process, r@plaoIng $~¢cessf~l ¢~capsulatlo~ to be achieved. The pH of th@ yaPPers m~x~s were similar to ~hose obtained in earlier @xp~r~m@~ts and fell w~thin th~ range &.9-5.0.

,k (2) The I.P.F. #&tent called for an adjustment in pH to h.8 with I0% ~aOH ~ndicating that the gelati~-acacla used by them resulted in a pH lower than 4.8. TO determine th8 effcct of lowerzng th8 pH of the mixture, various adjustments with I O~ acetic acid were carr&ed outF the acid being adQed to the gelatin 8ol prior to ~ixing. The following ~f adjustments were carried out with ~ acetic acid:- (1) No addition of acid #H of mix _ 4.90 (2) + I.O ml addition 4.66 (5) + 2.0 ml adattion h.~ (4) + 5.0 ml addition &.35 (5) + LL.0 m! addition 4.26 (6) + 5.0 ml additlon 4.20 These qumntitie8 of acid were based on 1/50 of the quantities o~ m~thol solution and wall mateI, l~l ~iven in the patent. The ~e&nti~ a~d ~Tum acacia used were obtained from British suppllers. Resul~s of ~ ~djuDtment5 • It ~a~ immediately evident f'rom the a~pearance of th8 mixes that the addition of acid had 801re ~fCect~ In adJuatmezt0 ~j 2 a~d 3~ the mIx~s, after the additlon cf Water appeared homogene0~s with ~o si&3u of se~apa~1on into layers, However in adjustments ~ and 6, the mixes dlSpl~ye~ a curd~like tempo~'a~ily stopped. A3"ter completion Of the process, mix~ f~om i, 2 and 5 adjustments rea~]tcd in solid ~els as were ~btained in the i~itial ttn~ccess~'~l experiments) b~t mlx~s fre~ 4~ 5 a~d ~ separated into ±we Zayers, the upper layer containing the ~solids" the lower layer ~elng e~senti&~ly weter, ~xami~ation of the products under the ~±croscope 6ho~ed that enca#sulatlo~ had b~en ~u~cessfn] with adjusllme~t 6 i.e. 5 ml. acid addition resultin~ in a pH of ~.20. The ~ap~ules had the characteristi~ "or83%ge and lemon" shapes, ~ll existed ~s discrete e~t~tles ~u~d gene~al~y fell w~$hin the 5-40 microns rang~. The ~mple slide - eoverslip pressure technique readily caused p~p~pe of the capsules, 0ozi~g o~t its ~onte~ts and leaving th~ empty Bhell~ behind thus establlshin~ that encapsulation had taken ~lace. (See Fig, i), The products from adjustments ~ and 5 appeared as large clumps of spherical globules which when subjected to the 8i~le 81&de - cov~rslip tech~lqtl~, tended to mer~e together into larger globules i.~. non-encapsulatLon, 6. 5705.395.3~

F, The various experiments outlined above clearly demonstrated that for successful encapsulation, the pH of the mix is a ¢rltlCal f~ctor, the optimuJ~ value under the experimental eonditlons eaLploy~d being ~.2Q. This finding was confirmed by several repetitions of th~ procssB Ddoptin~ th~ pH n~iterion ~nd in ~very C~SC successful encapsulation of menthol was achieved. The Rcseareh Department modlflcd me,hod ef mic~o- e~capsulatioll Gf menthol is dia~rnEnntica~ly represented overls~f~- J • 7. 5t0..3953