Tgp chi Khoa hpc Trudng Dgi hgc Can Tha Phdn B: Ndng nghiep. Thuy sdn vd Cdng nghi Sink hpc: 35 (2014): 74-82
Tap chl Khoa hpc Tru'dng Dai hpc Can ThcJ website: sj.ctu.edu.vn
ANH H i r d N G CUA KY T H U A T RANG HAT, KlfeM HOA VA CHAT NHU HOA M N CAC BAC TINH LY HOA HOC CUA BOT CA CAO
Nguyen Minh Thiiy'
' Khoa Ndng nghidp & Sinh hoc ung dung, Truong Bgi hgc Cdn Tho Thdng tin chung:
Ngdy nhgn: 23/06/2014 Ngdy chdp nhdn: 30/12/2014 Title:
Effect of roasting, alkalization and emusifiers on physico-chemical properties of cocoa powder Tit khoa:
Ba ca cao, bgt ca cao, chdt nhu tuong. kiim hoa, rang Keywords:
Alkalization. cocoa butler, cocoapowder, emulsifier, roasting
ABSTRACT
The stuify was conducted to investigate the effects of roasting temperature (105, 120, 135°C) and duration (30, 40 and 50 minutes), types of alkali (NaiCOi and K2CO3) with concentration (0.3, 0.5, 1, 1.5 and 2%), degree of fineness of cocoa powder (40. 100, 140 and 200 mesh) and cocoa butter content in cocoa powder (10, 15, 20 and 25%) on the quality of cocoa powder. The results showed that the high roasting temperature and the long time gave a poor quality in terms of color and flavor. Potassium carbonate at 0.3% gave ideal color of cocoa powder. The relationship between dispersibility of cocoa powder and degree of fineness, cocoa butter with time was found. Cocoa powder of 15% cocoa butler gave the better dispersibility. The effects of four types of emulsifiers and cocoa butler content were investigated. Optimum levels for emulsifiers were determined. Tl was found that emulsion stability and viscosity of whipped mixture increased with higher levels of emulsifiers and cocoa butler contents.
T 6 M TAT
Nghiin ciru dugc thuc hiin trin ca sa khdo sdt dnh huang ciia nhi$t do (105, 120 vd 135°C) va thai gian rang hgt ca cao (30 din SO phiit), logi chdi kiim (Na^Os vd K2CO3) vd ndng dg (0.3 din 2%) din chdt lugng bgt^
ca cao. Kit qud cho thdy nhiet dg rang cao vd thdi gian keo ddi dnh hudng khdng tdt ddi vdi mdu sdc vd miii vi hgt ca cao. Carbonate kali dugc sir dyng vdi hdm lugng 0.3% cho hot ca cao cd mdu sdc ly ludng. Tuang quan giua muc do phdn tdn cua bgi ca cao vd do min cua hgi, hdm lugmg ba ca cao (trong bgt ca cao) citng vdi thdi gian cOng dugc thiit lap. Muc do phdn tdn tdt thi hien vai bgt ca cao chiia 15% ba ca cao Anh huang ciia bdn logi chdi nhH hoa cOng dugc nghien cuu vdi muc loi uu cho lat cd cdc chdt nha hda dugc xdc dinh. Bg bin nhU tuang vd do nhdt cua hon hap ldng theo hdm lugng cda chdt nhU hod vd ba ca cao.
1 G161 THI|;U
Ca cao (Theobroma ca cao) dugc phan logi tiiupc hp Trdm (Sterculiaceae). Hgt ca cao touong mgi Id hat dd dugc Iin men va siy khd. San pham cua ca cao nib Id chocolate, bdt ca cao va bo ca
cao. Bpt ca cao Id sdn phdra tir hat ca cao rang va cung dugc sfr dung Idra nguyin lieu cho che biin chocolate. Miii vi ca cao quan frpng cho tien trinh chi biin chocolate va cd toi phat friin qua hai giai doan, trudc tiin la d giai dogn u lin men sau khi tou hogch va sau dd tiep tuc phdt friin d cdng dogn
Tgp chi Khoa hpc Trudng Dgi h(>c Cdn Tha PhAn B: N6ng nghiip, ThOy sdn vd Congnghi Sinh hpc: 35 (2014): 74-82 chi biin sdn phim (giai doan rang). Trong cdng
n ^ f che biin bdi ca cao, khoang 50% chat beo dugc ep ra khdi hat ca cao. Chit lupng bdt ca cao cd toi dugc cdi toiin bdi qua trinh rang hgt, xii Iy vdi dung dich kiim va chit nhu hda dugc ap dyr^.
Van di chii yiu cda quy trinh chi biin bdt ca cao la san phira lao thanh co toi dugc chdp nhan theo yiu cau cua thi trudng voi miii vi thom ngon, mau sac dep va miic dp phan tdn ldi Uong nude. Ca cao dugc xii ly vdi chit kiira cd toe cai toiin dugc chat Iugng, man ca cao dara ban, tang cudng raiii, giam vi dang va tang miic dd phan tan ciia bpt ca cao Uong cdc dgng nude uong tii ca cao (Miller el al., 2008). Chat nhu hda dugc su dung cung nham dn dinh dp bin nhu tucmg ciia bo ca cao cdn lai frong bdt ca cao frong nude. Myc tiiu ciia nghien cfru nham xac djnh cac bien phap xu Iy ca cao tdi uu frong tiin Uiito chi biin nham cdi thien chdt Iugng san phim bang viec nang cao gia Ui cam quan va tdng khd nang phdn ldn ciia bpt ca cao trong sdn phim nude ca cao udng.
2 PHLTONG PHAP NGHIEN CUtJ 2.1 Anh hudng cua ky thudt rang va kiem hoa den cac chi tieu chat lugng cua bdt ca cao
Nghiin ciiu dugc touc hien fai phdng toi nghiim Bp mdn Cong nghi thuc phdm, Khoa Ndng nghiep va Sinh hoc U'ng dyng, Trudng Dai hpc c i n Tho va Vien Kj? thudt Chau A (AIT), Thailand.
2.1.1 Chudn bi nguyen lieu
Hat ca cao da len men sii dung cho nghien cfru dugc tou nhan tai vudn ca cao tinh Bin Tre. Hdm lugng dm cua hgi ca cao khoang 5-6% (can ban udt). Hgt ca cao dugc siy khd d nhiet dp 70-75''C din khi dd im dat khoang 3%. Hat ca cao khd dugclis ddng bao kin va trtt d nhift dp phdng. Trudc khi rang, hat dugc kiim tta mau cua ndi nhii bdng may do mau.
2.1.2 Rang hat
Mau hat ca cao dugc rang toeo tiing me 10 kg bing thiit bi siy toiing quay vdi nhiit dp dugc kiim sodt tii 105 din I35°C vdi todi gian rang tir 30 din 50 phiil (cdch nhau 10 phiit).
2.1.3 Ddnh gid chdt luang hgt ca cao rang Xdc dinh dp Sm (Phuang phap AOAC, 1971).
Xdc dinh cdc thdnh phdn hda hoc: ham lugng ni-ta ting so (%) (phuong phdp Micro-Kjeldahl), ham lugng acid (%) (phuong phap chuin dp dua vao gia fri pH dimg), ham lugng dudng khu (%)
(phuang phap Munson va Walker, 1970), ham Iugng acid arain tu do frong hat ca cao (phuong phap Ninhydrin frac quang cdi tien cua Troll va Cannan, 1953).
- Bo mdu sdc bgt. mdu hat ca cao dugc do bang dyng cu do Model TC-P3 frong khdng gian mdu CIE 193IX YZ.
Phan ti'ch todng k i ANOVA dugc sfr dung so sanh mau hat trong qua trinh rang'va phan tich hii quy da biin dugc iing dung di xac dinh tuomg quan gitta cac gia tti mdu ctia bdt ca cao theo raiic do min va ham Iugng ba ca cao cdn lgi ttong bdt.
2.1.4 Kiem hda
Phdn ca cao (dgng mdng sau khi ep tach bo) dugc kiem hda ttong dung dich kiim (NaaCOs va K2CO3) vdi cac ham lugng toay ddi tis 0,3 din 2%.
Nhiit dd kiiiii sodt cho cac nghien cuu nay dugc touc hiin frong khoang 70 den 80''C. Sau do, mlu dugc sdy khd frong khoang 24 gid de ham dm gidm den 3,5%. Sau dd, kiem tra pH, mau sac, miii vi va khd nang phan tan ciia bdt ca cao.
2.2 Anh hudng cua cac chat nhu tuong hoa 2.2.1 Chudn bi mdu
MSU bpt cacao 1 kg dugc sii dung cho nghien cuu vdi hdra lugng bo ca cao thay ddi tu 10 din 25% va miic dp min cua hgt tii 40 din 200 mesh.
2.2.2 Phdn tich mdu
Kiem tra dd phan tan cua bpt ca cao Phdn trdm nu&c tdch ra (Y) dugc xac dinh la lugng nude tdch ra tfr hdn hgp. Thi nghiim duoc bd tti ngau nhiin. Can 3 g bdt ca cao va cho vao binh chfra 25 ml nude ndng, hdn hgp duoc khuiy : ^ F ^ P ^ ^ e m ^ ^ c h o din khi bdt'phdn tdn hodn ,
todn, sau dd chuyin hdn hop qua dng dong c6 vach. The tich nude tach ra tir hdn hgp dugc ghi nhdn frong khodng 50 phiit (dgc dft lieu sau moi 5 phut). Kiem fra rafrc dp phdn tan cua bdt ca cao kiem hda va so sanh vdi mau ddi chfrng ciing dupe touc hien ddng todi.
Ph&n Uch thong ki: phan tich thong ke (STATGRAPHIC) dugc su dung de chpn md hinh phu hap cho cdc dtt lieu tou thgp. Md hinh 3 dugc di xuit (gia tti Y) ttong trudng hgp nay
^^K+YK^.+fb x=+ y b X X^ (3)
Trong do: bo la hi sd; 6„, bm, vd bm la cac he sd bac 1, bac 2 ciia phuong trinh hii quy; X„, Xm Id cdc gia tti ciia biin ddc lap.
Tap chi Khoa Ape Tnrdng Dgi hpc Cdn Tha • Phdn B: Ndng nghiep, Thuy sdn va Cdng nghe Sinh hoc: 35 (2014): 74-82 _ De chpn dugc cdc diiu kiin tii uu, phan tich
hdi quy da biin dugc dp dung dien la sy thay ddi mfrc do phan tan (hay sy tach nude) cda bdt ca cao dugc xac diito la biin phu toudc vdo hdm Iugng bo ca cao (frong bdt ca cao), kich cd hgt va todi gian ghi nhan (ky hieu la Xi, X2 vd X3, tuang iing). Md hinh dugc chgn Id md hinh cd R^ cao so vdi cac md hirto khac. Ngoai ra, di kiim tra su tuong quan
^tta dp phan tan cua b$t ca cao va ham Iugng hodc chdt kiem su dung, md hinh frin dugc xdy dung dua fren cdc biin ddc Igp la ning dd chdt kiim va todi gian xii ly.
Bo d^ nhdt: hdn hgp nhii tuang dugc cho vao coc toiiy tinh vd i n dinh d nhiit 20°C frong khoang 20 phiit. Sau do do dp nhdl ciia hdn hgp nay frong 40 giay bdi^ Brookfield Viscometer.
Lyc can toiit tac ddng lin tryc quay ci dinh la 60 rpm, nhiit dd frong suit tiin tiinh do Id 20±1''C.
L^p lgi qud ttinh do 3 Ian cho mii mdu.
- Bg ben nhu tuang (ES).- ES la kha nang tao nhu tuomg bin va khdng toay ddi ttong cac diiu ki^n xu I^. Sfr dyng phuai^ phap cua InKIaar va Fortuin (1969), Hutton va Caraphbell (1977). Cdc chit nhii hda dugc stt dyng (Polysorbate, Sorbiiane monostearate va bai logi Lecitoin-dgng trich tfr Idng do tning va ddu d§u nanh) vdi ndng dp toay doi 0,25 din 0,7% (cdch nhau 0,15%). Hai mdu bdt ca cao chiia 15 va 20% ba ca cao dugc bd sung Bang 1: Thay ddi thanh phan hda hpc (*) cua hgt ca
cdc chat nhu hda va dugc khuiy frdn vdi tdc dp 20.000 rpm frong 2 phiit Ki tiip, hdn hgp nhii tuong dugc chuyin qua dng Iy tara va u a nhiit dd phdng frong 30 phiit. Sau todi gian nay, cac dng mau dugc cho vao may ly tam va qua frirto iy tam dugc touc hiin frong khoang 30 phiit vdi tic dp la 3.000 rpm. Mdu dugc ghi nhan ham Iugng nude tach ra, dp ben nliu tuong dugc tinh toeo cdng tofrc: K = (mL nude ttong man san pham ban dau - mL nude tach ra) x 100%/mL nude ttong mlu sdn phim ban ddu.
Phan tich thdng kS
Dd nhdt va dp bin rtou tirong dugc phdn tich toeo phuomg phap hdi quy da bien (phuoi^ ttiito 3). Trong irudng hgp nay, ham Iugng ba ca cao cd ttong bdt ca cao vd hdm Iugng chat nhu tuong hda Id cdc bien ddc lap.
3 KET QUA VA THAO LUAN 3.1 Anh hirdng ciia qua trinh rang din chit Iugng (thanh phdn hda hoc) ciia hat ca cao
Cac toanh phin hda hpc cua hat ca cao nhu hdm Iugng nito tdng sd, acid arain, ham lugng duang, acid dugc xac dinh. Anh hudng ciia nhift dp va todi gian rang din sy toay ddi thanh phan cdc chdt duoc trinli bay d Bang I.
cao trong qua trinh rang Nbi^t d$
raDB(±2"C) 0 105 105 105 120 120 135 135
Thjyi gian rang (phiit) 0 30 40 50 30 40 30 40
Kkxa liromg ni- ttf tong so (%)
2,099' 2,107*
2,100' 2,150' 2,100' 2,100"
2,120' 2,140'
Acid amin Ham lugug Leucine (%) duong
0,466' 0,276' 0,145' 0,129' 0,125' 0,120' 0,100' 0,098'
liliii (%) 5,300' 2,300' 0,520' 0,450' 0,500' 0,500' 0,420' 0,430'
pH.
5,43"
5,49' 5,56' 5,67' 5,60' 5,62' 5,64' 5,69'
\cid acetic Acid lactic 0,135'
(%)
0,127' 0,074' 0,054' 0,072' 0,069' 0,052' 0,049'
0,202'
(%)
0,191' 0,121' 0,082' 0,120*
0,106' 0,080' 0,078' Ghi chii *Gid Iri trung binh ciia 3 ldn lap tai - Cdc gid Iri irung binh di kem cdc chU gidng nhau trong ciing mpt cpl thi hien su khdc biit khdng cd y nghia d muc y nghia 1%
Kit qua cho toay hdm lugng ni-to tdng sd ciia hgt ca cao khodng 2,1% (d tit cd cac raau toi nghifm). Nhu vay khdng cd su mil mat ham Iugng nay frong qud frinh rang cd Ie do sy hinh toanh cdc chit phfrc ni-to va dudng khu hien diin Uong hgt.
Ham lugng acid amin ciia hat ca cao dugc do bang phucmg phdp quang phd vd dugc xdc dinh tfr dudng chuin (stt dung hgp chit Leucine tinh khiit da dugc xdy dgng ttudc). Ham Iugng nay Uong hat gidm ttt 0,47% din 0,098% khi rang din nhiet dg
135*^ trong 40 phiit. Trong todi gian rang tir 30 din 50 phiit (cimg nhi^t dp 105*'C) hara Iugng nay toay ddi rd rit vd toi hiin su khdc biet cd y i^hia.
(y nhiet dp rang cao hem (120 vd 135"C ttong 40 phut) cho toiy khdng khac biit ^ nghTa so vdi rang d 105°C frong 50 phiit. Nguyin nhdn chinh la do su hinh toanh dimetoyi sulfide ttt metoyl-S- methionine (Fermema, 1996). Rang d nhiit dp 120*^ frong 40 phiil dS phat trien hodn loan raiii vi cua chocolate. Thdi gian rang hat ngan va nhiit dd rang toap cd thi cho hat co gia fri chat Iugng kem.
Tgp chi Khoa hgc Trudng Dgi hpc Cdn Tha Phdn B: Nang nghiip. Thuy sdn vd Cong nghi Sinh hgc: 35 (2014): 74-82 Hdm Iugng dudng khtt giam khodng 57% sau
khi rang 30 phut d 105°C. Hiu hit hdm lugng dudng bi mit di (85-95%) sau khi rang d nhiit do cao (BS^C). Su toay ddi mui vi cd y nghia do su toam gia cua dudng khu frong phdn iing Maillard vd sy phan huy sfrecker (acid amin) (Yaylayan, 2003). Trong qua ttmh rang phdn frng Maillard ciing phat ttiin mau nau va miii thom vdi ham lugng dudng khfr la tien chit tham gia chii yiu vao phdn ling nay.
pH cua hgt ca cao chua rang la 5,43 vd hara lugng acid acetic, acid lactic tuang ung !a 0,135 va 0,202%. pH ciia hgt ca cao rang lang sau 50 phut rang, nguyin nhan chu yiu do su gidm ham lupng cdc acid bay hoi frong qua trinh rang, ddc biet la acid acetic, Id loai acid chu yiu frong hgt ca cao, toi hi|n su khac biet cd •^ nghia giua cdc nghiim
9
toiic. Hdm Iugng acid acetic gidm 56,42% d todi gian rang ddi so vdi mdu ca cao chua rang, gidm dugc vi chua ciia sdn pham ca cao. Acid lactic ciing gidm khodng 61% sau qua frinh rang. Nguyen itoan chu yiu do su phan huy hgp chdt ndy a nhiit do cao (120-140''C) va cho thiy anh hudng cd y ngbia tu cdc diiu kifn rang hgt. Do acid ndy cung hien dien vdi ham Iugng Idn trong hat ca cao, vi vdy giam ham lugng acid nay ding todi cung Iam giam mui acid ciia bdt ca cao.
3.2 Anh hudng cua qua trinh rang din mau sac cua hat ca cao
Kit qud khao sdt cho thay mau sac sdn phim cang dam (cdc gia tii X, Y, Z diu giam) khi rang hat d nhiet dd cang cao vd todi gian keo dai (Hinh i).
30-105 40-105 50-105 30-120 40-120 30-135 40-135 Thdi gian (phut) - nhiet do rang (°C)
• Gia tti Z a Gia fri Y S Gia fri X Hinh 1: Mdu sac ciia hgt ca cao dugc rang
Phan tich toong ki cho tody sy khac biet cd ^ nghia gitta hgt ca cao dugc rang frong thdi gian 30 den 50 phdi. Nhiit dp vd todi gian diu dnh hudng quan frpng din sy toay dii mdu sac hgt, tuy nhien khdng cd su khdc biit y nghTa khi rang d 120 va 135*^0 trong 40 phiit.
3.3 Anh hirovg ciia mfrc dp min (ldch thudc hgt) vd bim lirgog b<r ca cao (trong b$t ca cao) din kha nang phdn tdn cua bdt ca cao
3.3.1 Anh huang cua kich thuac hgt Kit qua toe hien d Hinh 2 cho toiy tuong quan giiia dp phdn tdn ciia bdt ca cao toeo thdi gian dugc xac djnh bdng lugng nude tach ra (bdt ca cao chiia
fr cdc nhift dp vk thdi gian khdc nhau 15% ba ca cao), lugng nude tach ra tang toeo' todi gian. Sau 50 phiit, Iugng nude tach ra nhiiu nhat toe hien d man bpt ca cao cd kich toudc 40 mesh (tuong iing 0,4 rmn) (24,74%) vd it nhat doi vdi radu cd kich toudc 200 mesh (tucmg umg 0,074 mm) (12,48%). Cac miu bgt ca cao chiia ba ca cao vdi ham Iugng 10, 20 va 25% diu xdy ra khuynh hudng tuang tu (dtt lieu khdng dua ra day dd d day). Kit qud khdng dinh ring tirto chat quan frpng cda bdt ca cao la miic dp min cua chiing. Hgt cd kich thudc Idn si nhanh chdng frim Idng va tgo gid tri cdm quan kem cho san pham sfta bdt ca cao uong hogc san phim kem.
1'op chifOioahf>c Tnrang Difi Ape Cdn Tha
30 a 25
I 20
| , 5
5
Phdn B: Ndng nghiip. Thity sdnvd Cdng nghi Sinhhoc: 35 (2014)- 74-82
0
0 5 10 15 20 25 30 35 40 45 50 55 Thai gian (phiit)
• 200 mesh • 140 mesh * 100 mesh x 40 mesh Hinh 2: Anh hudng ciia kfch thudc hot ca
3.3.2 Anh huang cua hdm luang ba cd cao Hinh 3 cho ket qua khdo sdt hdm Iugng nude tdch ra cda bdt ca cao cd kich toudc 200 mesh (0,074 mm) vdi ham Iugng ba ca cao khac nhau.
Sau 50 phijt, ham Iugng nude tach ra nhiiu nhdt (22,30%) dii vdi bdt ca cao cd chua 25% bo ca cao vd lugng nude tach ra it han dugc quan sdt doi vdi bdt ca cao cd hdm Iugng ba 10 va 15% (12.22 vd 12,48%, tuong frng). Kit qua tuomg tu dii vdi bpt ca cao cd kich toudc khdc (140, 100 va 40 mesh).
Muc dd phdn tan cua bpt ca cao d cac hdm lupng beo khdc nhau tiiudng gidm klii hdm lugng beo
25 - 20 i -.2 15
J.no^
^ 5 0
cao din Idia nang tach mifrc theo thdi gian frong bOt ca cao tang. Tinh chdt ua nude kem do su hinh toanh chit hogt ddng be mdt cda cdc nhdm CH va -CO han nhdm -OH, khi bi mdt cda timg hat dugc bao phu bdi ham Iugng ldn bo ca cao.
Tuong quan dugc xdy dung ttt phdn tich hdi quy da biin thi hien d phuang frmh 4. Mttc dp phan tdn cua hdn hgp ldng mdt each cd y nghTa vdi sy gidra hdm lugng bo ca cao va tdng mttc dp min cda bot ca cao, thi hiin d cac he sd ciia biin dpc lap (Xi, X:, X3) cho gia tti duang. Cdc he si bo vd h-n mang diu trtt (-0,001 vd -0,09, tuong ung), cho tody mttc dp phdn tan cua bdt ca cao tang khi kich toudc hgt giam hogc dd min cua hgt tdng.
0 5 10 15 20 25 30 35 40 45 50 55 Thoi gjan (phiit)
• 10% b o cacao • 15% b o cacao A 2 0 % bo cacao ^ 2 5 % bo cacao
Hinh 3: Anh hudng cua ham Iupng bu ca cao con lai trong b^t ca cao (kich thufrc hat 200 mesh) din kha nang tach nude theo thdi gian
Y = -19,84-K),32X,+1,89X2+0,096X3-K),01 Trong do: X, la todi gian (phOt), X2 la ham XiXr-0,001 X,X3-0,009 X2X3 (4) [u^ng bo ca cao (%) vd X3 la kich toudc cua hgt ca R2 = 0,90 SEE = 3,847 cao (mesh).
Tgp chi Khoa hpc Trudng Dgi hpc Cdn Tha Phdn B: Ndng nghiip. ThOy sdn vd Cong n^ti Sinh hpc: 35 (2014): 74-82 3.4 Anh huong cua qud trinh kiim hda den
kba nang phan tan va mau sSc ciia bSt ca cao 3.4.1 Muc do phdn tdn
Kit qua nghien cttu cho toay mttc dp phdn fan ciia bpt ca cao tang cd y nghTa so vdi mdu ddi chttng nhung lgi khdng toi hi^n su khac biit y n^Ta vi muc do phan tan khi su dung ham Iupng chat kiim Uong khoang 0,3 din 1,5%. Vdi todi gian xtt Iy 50 phut, gia tri tnmg bmh cua ham lugng nude tach ra Id cao nhit (13,73%) va khdng thi hien sy khdc biit dang ke vdi cdc ham Iugng cdn lai (5,90-6,97%). Nguyin nhan chinh la do khi
' " >5 20 25 30 35 Thdi gian (phut) Hioh 4: Anh hirdng cua h^m lugng NazCOs xir Ij t Kit qud phdn tich hdi quy da bien ttong trudng hgp stt dung chat kiem la NaiCOi dugc cho d md Hinh 3.
-11,42 X2-0,0002 X!^7,35 (6) Y2 = 3,85+^,33 X,
X2M,118XiX2
R2 = 0,88 SEE =1,70
Trong dd: Yi Id mttc dp phdn tdn ctta bdt ca cao (dugc xac dinh la % nude tach ra) tii hin hgp khi xtt Ij bdng KiCOs; Y2 la mttc dp phan tan ciia bdt ca cao (duoc xdc dinh tu % nude tach ra) ttt hdn hgp khi xtt Iy bing NajCOj; Xi Id ham Iupng ba ca cao (%) vd X2 la ndng dp ciia K2CO3 hoac N a i C O j (%).
Arto hudng cua ham Iugng NaiCOa xtt Iy din mijrc dp pban tan bdt ca cao Uong nude dugc biiu toi d Hinh 4. Kit qud tuang tu toi hifn dii vdi qua
xu Iy chit kiim, cac hat ca cao ttuang nd vat Vjf, thanh phin tinli bpt cua hat ciing iruang nd va Idm tang idid ndng phan tan ciia hat frong nude. Phdn tich toeo md hinh da biin dii vdi chit kiim su dyng la K2CO3 dugc toe hien d phuang frinh 5.
Yl = 4,087+0,319 Xi-n,832 X2-0,0002
X,^+7,558X2--0,15IX,X2 (5) R2 = 0,89 SEE =1,67
Trong truong hgp nay, cac he sd hdi quy b|c I va bac 2 diu the hi^n y nghTa cho cd hai biin todi gian va ndng dd chit kiim.
HNa2CO3 0.3%
ONa2CO3 0.5%
S N a 2 C 0 3 1%
l3Na2C03 1.5%
Q Mau ddi chfrng
40 45 50
tin khd ning mttc dp phan tdn cua hot ca cao trong nud'c frinh xtt Iy bdng K2C03 (dtt lieu khdng dua ra day du d day).
3.4.2 Quan hi giUapHva mdu sdc hgt ca cao rang theo hdm lugng chdt kiim
Dtt liiu pH vd mdu sac bdt ca cao dupe xtt ly bang cdc chat kiira Na2C03 va K2CO3 dugc frinh bay d Bdng 2. Kit qua cho tody hdm Iugng acid ciia bdi ca cao dugc xac dinh todng qua gia fri pH, la chi tiiu do ludng chat Iugng ciia bpt ca cao frin to; frudng. Gia tti pH ctta bdt ca cao xtt 1;? vdi 2 logi chit kiim hiu nhu khdng khac bi§t nhieu, tuy nhiin 0,3% K2CO3 sfr dyng cho mdu sdc bOt ca cao dep hom so vdi Na2C03 vd tuong tu vol mlu chuin (mdu bdt ca cao tdt frin toi trudng). Gia frj pH ciia bdt ca cao khdng dugc thip han 5 do d pH ndy bpt ca cao cd mui \'\ kem va khdng toi hipn mfii d$c trung cua chocolate.
T^ chi Khoa hpc Tmang Dgi hpc Cdn Tha Phdn B: Nong nghiip, Tkiiy sdn vd Cdng nghi Sinh hpc: 35 (2014): 74-82 B^pg 2: Mau sic va pH ciia bdf ca cao tbeo cac chit kiim vk nong dd su dyng (*)
C h a t k i e m s i r ly M a u doi Chung M l u chuan
G i i t r i X 13,332' 14,825"
G i a t r i Y 11,508' 11,982'
G i a t r | Z 6 , 2 9 2 ' 6,786'
p H 5 , 4 1 ' 6,40' K2CO3 (%)
0,3 0,5 1,0 1,5 2,0
14,972' 10,710' 10,4085 1 0 , 9 6 2 "
3,6701
12,832' 9 , 3 9 8 ' 9 , 2 0 8 ' 9 , 7 2 2 ' 3,112'
6,864' 5,306' 5 , 3 8 8 "
5 , 6 0 4 "
2 , 4 4 0 '
6,04' 6 , 1 9 ' 6 , 2 6 ' 6 , 3 6 ' 8,268 NajCOa (%)
0,3 0,5 1,0 1,5 2,0
13,596' 11,674' 11,030' 10,082' 4,170'
11,790' 10,382' 9,742' 8,932B 3,480'
6 , 2 6 0 ' 6 , 4 2 2 ' 5,682' 5 , 1 9 8 ' 2 , 3 9 2 '
6 , 0 1 ' 6 , 0 6 ' 6 , 2 6 ' 6 , 3 1 ' 8,19' Ghi chu: (*) Sd liiu trung binh ciia 5 ldn lap lgi - Cdc chii gidng nhau di kem Iheo cdc trung binh nghiim thuc bieu th/
Sit khdc biit khdng cd y nghTa d mite y nghia 5%
Mdi quan hi giua cdc gia tti mdu ciia bdt ca cao (X, Y, Z) vd pH dugc xdy dung dya vdo dtt Ii$u tiiu todp. Phan tich hdi quy da bien ttong phan tich toing ki dugc dp dung di dien ta mdi tuang quan nay (phuang ttinh 7 va 8) vdi tucmg quan cao dugc tim thiy (R^>0,99). Nhu vay, cd toe dg dodn de dang va chinh xdc gid tti pH bOt ca cao kiim hda toeo cdc gid trj mdu do dugc.
Yl = 16,084-6,6843 Xi+8,284 X2-3,7985 X3-K),0074 X1X2X3 (7)
R2 = 0,989 SEE = Y2 9,288-5,214 X3-K),0026 X1X2X3
0,2205
Xi+6,449 -1,766 (8) R2 = 0,997 SEE = 0,1168
Trong dd: Yi va Y2 la gia tti pH ctta bdt ca cao xtt If vdi cdc ndng dp K2CO3 va NaiCOa khac nhau, luong ttng; Xi, X2 vd X3 la cac gid tri X, Y vd Z ctta bdt ca cao xtt ly vdi cac nong dp chdt kiim (K2CO3 hoac Na2C03).
Bdng 3: Dp nhdt ciia bpt ca cao (danh khuiy) vdi cac ham lugng chat nhu hda
3.5 Anh hirong ciia cdc chat nhu boa din cdc dgc tinh ly hpc cua hon hop bpt ca cao trong nirdc 3.5.1 Anh hudng cda chdt nhU hda din do nhdt cua bgt ca cao trong nude
Kit qud nghiin cttu anh hudng ciia ham Iugng cac chdt nhu hoa din dp nhdt ciia nude udng ca cao dugc ttinh bdy d Bdng 3. Dp nhdt cua cac dung dich nhu tuong todp khi stt dung ndng dp cdc cbit 0,25 va 0,4% va cao nhit d ning dp 0,55-0,7%. DO nhdt dung djch toudng tang trudc khi chuyin pha vd su tdng dp rtodt la mdt dgc diem ciia Idp kem bo tu nhiin dugc hinh todnh. Thdi gian daito khuiy keo dai toudng dua vdo hdn hgp nhiiu bgt khi itod vd chiing kit hpp Iai tgo todnh mang bpt min uin ldp kem bi mat, kit hgp vdi khdng khi vd dnh hudng den su hgp ttoat^ be_mdl nhdn gimcua^chdt. _ beo vd nude. Kit "qud ghi hhdn^Koitnay-hau^nhfr khdng cd sy khdc biit y nghia ve dd rtodt dich ca cao khi stt dyng lecithin d cd h£u dang va dp nhdt dung dich cao nhdt dgt dugc vdi polysorbate va sorbitan monostearate.
H i m lirgrng cliat n h u b a a t % )
0,00 0,25 0,40 0,55 0,70
P o l y s o r b a t e 2 , 3 2 5 ' 3,250' 3 , 4 2 5 ' 3,950' 4 , 0 7 5 '
S o r b i t a n m o n o s t e r a t e 2 , 3 2 5 ' 3 , 6 3 7 ' 3 , 8 3 7 ' 4 , 1 1 2 ' 4 , 3 3 8 '
Lecithin (long d o
2,338' 2 , 8 7 5 ' 2 , 9 6 3 ' 3 , 2 7 5 ' 3,400'
t n S n s )
L e c i t h i n ( d a u t h u c vJt) 2 , 3 2 5 ' 3 , 0 6 3 ' 3 , 1 6 3 "
3 , 2 1 3 ' ' 3 , 2 6 3 ' Ghi chu: (*) So liiu trung binh cua 5 ldn lap lgi - Cdc chir gidng nhau di kem iheo cdc trung binh nghiim ihuc bieu thj su khdc bift khdng cdy nghta d mucy nghTa 5%
Tgp chi Khoa hpc Tmdng Dgi hpc Can Tha Phdn B: Nong nghiip. Thuy sdn vd Cong nghi Sinh hpc: 35 (2014): 74-82 I 3.5.2 Anh hudng cua chdi nhU hda din do ben
nha tuang (ES) cua bdt ca cao
Arto hudng cua cdc chat rtou hda din dp bin nhu tuang toeo ham Iupng bo ca cao cdn Iai ttong bpt ca cao dugc ttinh bay a Hinh 5. Su kbac biil vi ES chu yeu phy toudc vao ham Iugng ba ca cao ttong bdt ca cao. Dgc diem khac biet nay chu yiu do bo ca cao nhanh chdng dugc h ^ tou tgi bi mat phan gidi 2 pha beo va nude va tgo toanh Idp mang
bin xung quanh gipt beo, bao vi chung chdng Igi sy kit bdng hgp rtoit lai va tach beo. Do v|.y, ca bo ca cao, chit nhu hda va hdm Iugng cua chiing anh hudng quan ttgng din dp bin rtofl tuong. Dd ben nhu tuong dgt dugc cao nhdt khi bo ca cao hien diin frong bdt ca cao la 20% vdi sorbitan monostearate (ho§c polysorbate) 0,55% dugc stt dyr^ (khdng khac biit ^ nghia so vdi ndng dO 0,7%). Thdi gian khdng Jbih hudng din dO bin rtou tuang d tat ca cdc thf nghiim.
Hinh 5: Dp ben nhu tuong ciia hon hgp dugc xfr ly vdi (a) polysorbate, (b) sorbitan monostearate, (c) Lecithin (long do trung) va (d) Lecithin (diu dgu nanh)
4 KETLU4.N
Bgt ca cao cd raiii toom, mdu dfp va vi chua gidm khi hgt dugc rang d 135"C frong 40 phut va kiim hda bdng K2CO3 d ndng do 0,3%. Do phan tan cua bdt ca cao dnh hudng bdi dp min cua hat, bdm lugng ba ca cao vd ndng dp chit kiim stt dyng. Bpt ca cao cd ham Iugng ba ca cao 15% toi hi$n khd ndng phdn tan til frong nude. Dp bin nhu tuong cao khi stt dyng sorbitan monostearate va polysobaie vdi ndng dp 0,55%, sdn phim nude udng ca cao cd dp nhdt cao vd dp phan tan tit.
TAI LIEU THAM KHAO
1. Fennema, O. R. 1996. Food Chemistry, Third edition. Marcel Dekker, Inc. New York, United State of America, 1071 pages.
2. Hutton C. W. & Campbell, A. M. 1977.
Functional properties of a soy concenttate and a soy isolate in simple systems.
Nifrogen solubility index and water absoiption. Joumai of Food Science, 42, 454-458.
Tgp chi Khoa hoc Tnrdng Dgi hpc Can Tha Phdn B: Ndng nghiip. Thiiy st a Cong nghi Sinh hpc: 35 (2014): 74-82 Inklaar, PA. & Fortune, J. 1969.
Determmh^ toe emulsifyii^ and emulsion stabilizing capacity of protem meal additives. Food Technol. 23:103.
Miller, K. B.; Hurst, W. J.; Payne, M. J.;
smart, D. A., Apgar, J.; Sweigart, D. S.; Ou, B. 2008. Impact of alkalization on toe antioxidant and flavanol content of commercial cocoa powders. J. Agric. Food Chem 56:8527-33.
5. Munson and Walker's metood- AOAC. 1970, page 533 (31-038).
6. TroU, W.& Cannan, R.K. 1953. A modified photoraefric nirtoydrm metood for the analysis ofamino and imino acids L Biol. Chera., 200, pp. 803-811.
7. Yaylayan, V. 12003. Recent advances in the chemistry of Sfrecker degradation and Amadori rearrangement: implications to aroma and color formation. Joumai of Food Sci. Technol. Res. 9 (I), 1-6.
