NGHIEN CU'U ANH HU'QNG CUA CHE PHAM TAO MANG SINH HOC CHU'A CHITOSAN VA NAM MEN D6| KHANG
TOI N A M M 6 C G A Y THOI H O N G Q U A THANH LONG
Le Thien Minh\ Phung Thj Tuydt Mai^
Dd Tat Thuy\ Nguyin Duy Lam^
Vien Co dien Ndng nghiep vi Cdng nghg Sau thu ho^ch
^Truong Dai hge Hong Dd'c Thanh Hda
Tom tat
Nghien cieu ndy nhdm ddnh gid tde dimg cua che phdm tgo mdng sinh hoc chira chitosan vd ndm men ddi khdng Candida sake TLl de kiem sodt cdc ndm mdc Penicillium vd Aspergillus niger gdy thdi hong qud thanh long trong qud trinh bdo qudn. Nong dp ire chi tdi thieu (MIC) ciia chitosan len ndm mdc Penicillium vd Aspergillus niger Id 0,3%. Chung ndm men Candida sake TLl ddi khdng phdt trien tdt tren mdi trudng chiea 0,5% chitosan vd 0,5% CaCh, cho gid trj OD cao nhdt 0,766 sau 90 h nudi cdy. Chi phdm ndm men ddi khdng Candida sake TLl kit hpp vdi 0,5%
chitosan vd 0,5% CaCh cd tde diing uc che cao nhdt tdi suphdt trien ciia ndm mdc Penicillium vd Aspergillus niger ty l^ thdi hdng Id 18% vd 16% theo thir tu.
Tie khod: Chitosan, bdo qudn, thanh long, Candida sake, ddi khdng, ndm mdc.
I. OAT VAN oe
Thanh long la loai trdi cdy xudt khdu cd the manh, la cay Idm giau vd man^ lai thu nhdp cao cho ngudi ndng ddn. Hom 70% sdn lupmg thanh lon^ nudc ta dugc xuat khdu sang nhieu nudc trong khu vuc, Tdy Au vd Bdc My. Ciing nhu da sd cdc loai cdy dn qud khdc, qud thanh long thu hoach theo thdi vu, vdo mua thu hoach san lupmg thu hoach rdt Idn. Trong khdu xft ly, bdo qudn thanh long trudc khi xuat khau, cdc dom vi thu mua thudng sft dung hda chat khdng rd nguon goc dl xft Iy. Do dd, cd thl tao ra nguy ca tdn du hda chat ddc hai tren trai cdy vugt qud mftc cho phep. Ben canh dd, do thanh long xudt khau thudng dugc van chuyin ddi ngdy bdng dudng bp vd dudmg biln nen khi din nai trai thudng bi kem chdt lugng vd hu hdng. Vi vdy, vi?c nghiin cftu kdo ddi thdi gian bao qudn thanh long de duy tri dugc cdc ddc tinh tu nhien ve mdu sde, cdu trftc, huomg tham, gid tri dinh dudmg vd an todn cho ngudi sft dung Id hit sftc cdn thilt (Hoa & CS., 2006).
Hi?n nay tren thl gidi, cdng nghe sft dung mang phft trong bdo qudn rau qua tuai dang dugc phi biln d rat nhilu nudc vdi nhilu loai qua khdc nhau. Mang phu cd the tao ra vung vi khi quyln dilu chinh xung quanh qud, ldm thay ddi sir trao ddi khi vdi khdng khi xung quanh. Do dd h?in chl s\r hd hdp cua rau qud, lam gidm tdn thdt khdi lugng va lam chdm su nhdn nheo cfta qua do hfin chl qud trinh mat nudc, ngdn can su xdm nhdp cua vi sinh vdt, chdng lai su mat mdu cfta qud, d$c bi?t IJidng gdy dpc h^i cho ngudi sft dung. Bdo qudn qua bdng ndm men ddi khdng Id mpt phuang phdp sinh hpc cd uu dilm trdnh dugc ngd ddc hda chdt vd khdng gdy d nhiem mdi trudng. Nguyen Iy cfta phuomg phdp ndy Id tao ra nhihig chiing nam men an todn, khdng hodc rdt it khd ndng phdn gidi thdnh tl bao th\rc v^t. Khi phdt triln tren bl mdt ndng sdn nhu rau qua tuoi, do tde dvmg c?inh tranh md chftng h ^ chl dugc s\r phdt triln cua cdc vi sinh veit gdy hdng qud (Shama & CS., 2008; Meng & CS., 2010).
Cdc kit qua nghien cftu da cdng bd trong vd ngoai nudc vl su kit hgp chl phdm tao mang vdi ndm men ddi khang den nay van cdn rat it. Sir ket hgp thdnh cdng se cho tac dung kep cua cd hai ky thudt rieng re. Trong qua trinh kit hgp dd, ngodi viec tao ra hieu lire cfta chl phdm t?o mang, hieu luc ddi khang cua ndm men bo sung, cdn phai nghien cftu sir thich nghi, tdq tai va phat triln cfta ndm men trong cac'chl phdm tao mdng (Rahmau & CS., 2009). Vi y|iy, nghien cftu nay nhdm dk cap din kha nang phat trien cfta chung ndm men ddi khang Candida sake TLl trong mdi trudmg chfta chitosan. Tft dd, danh gia hieia qua fte chl cfta chl phdm ndm men ddi khang kit hgp vdi chitosan len su phat trien nam mdc gay thdi hdng thanh long trong qud trinh bao quan.
II. VAT LIEU VA PHU'aNG P H A P
• •
2.1. Odi tu'O'ng, vat lieu nghien CLFU
Gidng thanh long vd dd ruot trang dugc trdng d Hodi Dftc, Ha Ndi.
Chftng nam men Candida sake TLl ddi khdng dugc tuyen chpn tft bd suu tap gidng ciia be mdn nghien cftu cdng nghe sinh hpc sau thu hoach. Chftng nam men nay cd khd ndng fte che hodn todn su phdt trien nam mdc Penicillium vd Aspergillus niger gay thdi hdng thanh long sau 6 ngdy nudi cay tren dia thach. Cac^chftng ndm mdc Penicillium va Aspergillus niger gay thoi hong dugc phan lap tft qua thanh long.
^^^. Mdi trudmg nudi cay:
(1) Mdi trudng PDA (g/I): Dich chilt khoai tdy 1000 ml; Glucose 20 g; Agar 15 - 2 0 g/I;
pH dieu ehinh den 5,5 - 6. Khft trung d 0,8 at trong 30 phftt.
(2) Mdi trudmg malt - thach: Dich chiet malt 1000 ml; Agar 20 g/l; pH dilu chinh din 5,5 - 6. Khft trung d 1 at trong 30 phftt.
Chitosan do cdng ty TNHH sdn xudt kinh doanh chitosan Viet Nam san xudt, trpng lugng phdn tft 100.000 dalton, dp dk axetil hda 90%>.
2.2. Phu'O'ng phap thip kha nang ddi khang nim mdc cua nim men Candida tren qua
Tien hanh theo phuomg phap cua Wilson vd cdng sir (2002). Qua sau khi phan loai, dupc rfta sach bdng nudc may. Rfta lai bang nudc cat, de khd tu nhien. Trong, qua trinh rfta va lau trdnh say sdt hodc Iam tdn thuomg qud. Sau dd, tren mdi qua tao 4 vet thuomg bang dung cy d\ic Id vd triing dudmg kinh 5 mm, sdu 2 - 3 mm sao cho khdng cham den thit qua. Qud d 16 thi nghiem nhilm 20 pi ndm moc gay thdi hdng d mat dp 1 x lO'' CFU/ml. Sau 2 h d nhift dp phdng, nhilm tiep 50 ul ndm men ddi khdng mat dp 1 x lO' CFU/ml vao Io d phia tren. Qua d 16 ddi chftng dugc xft Iy tuomg tu nhu d Id thi nghiem nhung khdng lihiem ndm men ddi khang ma thay bdng 50 pi nudc cat tiet trftng. Qua dugc xep vdo cdc khay nhua, sau 7 ngdy d nhiet d6 25°C, kiem tra va tinh ty I? cdc Id bi thdi tren tdng sd cdc Id.
2.3. Phu'O'ng phap nghien CCFU tac dung cua chitosan t&\ vl sinh vat gay hong qua
Thuc hien theo phuang phap ndng do fte che tdi thieu (MIC). Sft dung dng nghif ni vd trung chfta 10 ml mdi trudng PDA Idng vd chitosan vdi cdc ndng do: 0%; 0,1%; 0,2%;
0,3%; 0,4%) vd 0,5%» dugc hdp khft trung. Moi dng nghiem sau dd dugc cho vao 100 \il hon dich chfta vi sinh vdt gay hdng qua thanh long lO' CFU/ml. Moi cdng thfte 8 dng nghiem, I|p l?i 3 ldn. Xdc dinh sir nay mdm cua bdo tft sau 48 h d nhiet dp 28 - 30°C trong tft nudi. Tinh ph^
tram sd dng nghiem cd nam moc mpe dl xdc dinh khd ndng fte chl nam mdc cua chitosan d ndng dp khdc nhau.
200
2.4. Nghien CLPU tac dung cua chitosan tm SIP phat trien cua nim men ddi khang
Cdc chftng ndm men Candida spp. cd khd ndng ddi khdng cao nhdt da dugc tuyin chgn tft muc 2.2 dugc nudi cdy trong mdi trudng nudc maU chfta chitosan (ndng do chitosan > MIC) cd bd sung va khdng bd sung 0,5% CaCb, tren may ldc 200 vdng/phftt, d 28°C. Lay mdu sau moi 12 h'higt lan trong 5 ngay nudi cdy. Do mdt do quang OD dk xdc dinh su phat triln ndm men tfen mdy do mdu Zuzi 411OED d buac sdng 660 nm.
2.5. Nghien CLPU tac dung cua chitosan va nim men ddi khang co bd sung CaCb din SIP phat triln nim gay thdi hong tren qua thanh long
Nudi cdy ndm men trong mdi trudng maU sau 48 h thu hdi bdng ly tdm 10.000 vdng/phftt trong 5 phftt, hda tan lai bdng nudc tiet trftng rdi ly tdm lai Idn nfta. Ndm men sau ly tdm dem pha vdi dung dich 0,5% chitosan vd 0,5% CaCb dilu chinh din lO' CFU/ml. Tao vit thuomg tren bl mat qud bdng dvmg cii due Id vd trftng dudng kinh 5 mm, sdu 2 - 3 mm. Dl ddnh gid hieu qua bao ve cfta hon hgp (chl phdm mdng sinh hpc), tiln hdnh xft ly theo 5 cdng thfte: (I) Cdng thfte 1 - Dich tl bao nam men lO' CFU/ml; (2) Cdng thfte 2 - Dung dich chitosan 0,5% trong axit axetic; (3) Cdng thfte 3 - Dung dich chitosan 0,5% bd sung 0,5% CaCb; (4) Cdng thfte 4 - Dich tl bao nam men lO' CFU/ml chfta 0,5% chitosan; (5) Cdng thfte 5 - Dich tl bdo ndm men 10^
CFU/ml chfta 0,5% chitosan va 0,5% CaCli. Due Io tren qud, sau dd cho 20 pi tl bdo nam mdc gdy hdng qua ndng dp 10'* CFU/ml. Sau 2 h nhilm them vdo 50 pi dich chl phdm theo 5 cdng thfte tren. Qua d Id ddi chftng dugc xft ly bdng 50 pi nudc cdt vd trftng. Bdo quan qud d nhiet do I thudng tren khay hodc thftng cdt tdng hodc cd the xep trong tfti PE de duy tri dp dm cao. Theo
doi vd dem sd Id bi nhiem sau 7 ngdy.
2.6. Phu'O'ng phap XLP ly sd lieu Microsoft Excel 2003 va Irristart 4.0.
III. K^T QUA vA T H A O L U A N
3.1. Xae djnh kha nang LPC chl cua Candida sake TLl ddi v6i nim mdc gay thdi hdng qua thanh long
Kit qud nghidn cftu thdm dd cho thdy chung ndm men Candida sake TLl cd khd ndng fte chl hodn todn sy phat triln cfta ndm moc gdy thdi hdng thanh long sau 6 ngay nudi cdy tren dia th^ch chfta mdi trudilg PDA. Vi vdy, kha nang ddi khdng cua chftng nay doi vdi ndm moc gay hdng ngay tten qua thanh long tilp tvic dugc nghien cftu. Cdc qud thanh long dugc chia thdnh 6 16 thi nghiem, mdi Id 20 qua, moi qud dvic 4 Id bdng dvmg cvi diic Id vd trftng d cac vi tri khdc nhau trdn qud. Kit qua dugc trinh bdy d bdng 1.
Bang 1. Khi ndng CFC chl nSm mdc cua nim men Candida sake TL1 tr&n qua thanh long sau 7 ngay o nhiet d$ thuang
STT Ld thi nghidm
DC (d6i chCpng) Candida sake TL1
Ty \g nhilm mdc (%) A.niger
100 30
Penicillium 100
34
Tft bang 1 ta Ihly, dr Id ddi chftng cdc vit thuang fren qua thanh long dugc nhiem ndm m6c Aspergillus niger va nSm mdc Penicillium vdi lugng tl bdo Id 1 x 10'* CFU/ml dlu cd ty le bi
thdi hdng Id 100%). CJ Id thi nghiem, vdi ndm mdc A.niger va Penicillium cd bd sung 1 x lo^
CFU/ml tl bdo ndm men Candida TLl ty le vit thuang bi hdng la 30%. va 34% theo thft ta. Kit qud nghien cftu nay phu hgp vdi kit qua nghien cftu cfta Wilson va cdng sur (2002) thft kha nang doi khdng cua nam men Candida saitoana ddi vdi nam mdc Penicillium expansum gay thdi tren qud tao. Kit qua chi ra rang, khi bd sung Candida saitoana cd tac dung fte phi ndm mdc Penicillium expansum sau 7 ngdy d nhiet dp 24°C vdi ty Id vet thuang bi hdng Id 47%. Tuy nhien, theo mdt sd tac gia thi kha nang fte che cfta nam men ddi vdi nam moc phvi thudc vdo nhilu ylu td nhu loai qua, nhiet dp, dp am bao qudn va kieu lam tdn thuomg qud.
3.2. Tac dung cua chitosan td'i SIP phat trien cua nim mdc gay hong qua thanh long dien hinh
Tien hdnh thi nghiem su phdt trien cfta ndm mdc peniciliiim vd A. Niger tren mdi trudng PDA cd bo sung chitosan tiieo cac nong dp khdc nhau: 0,1%; 0,2%; 0,3%.; 0,4% vd 0,5%
chitosan. Nudi cay d 28°C khoang 3 - 5 ngay, sau dd kiem tra svr phdt trien cua nam mdc (bang 2).
Bing 2. Anh hirang cua chitosan t6i si^ phat triln cOa nim m6c giy hdng qua thanh long diln hinh sau 5 ngay nudi cly
STT
1 2 3 4 5
Ndng d$ chitosan (%)
0,1 0,2 0,3 0,4 0,5
7^ lg dng nghidm cd nim mdc phit triln (%) Penicilium
100 0 0 0 0
A.niger 100
50 0 0 0
Tft bang 2 ta thdy rdng, khi bd sung chitosan d ndng dp 0,2% trong mdi trudmg PDA Idng, tdt cd cdc dng nghiem nudi cdy Penicillium dlu khdng phat triennhung 50% ong nghipm cay.^^.- Niger van cd khd nang phdt triln. Khi ndng dp chitosan tang len 0,3% hodc Idm horn thi tdt cd cdc dng nghiem khdng cd svr phdt trien cua ndm mdc, chftng td d ndng dp 0,3% chitosan cd khd ndng fte che svr phat trien cfta ndm mdc hodn toan sau 5 ngdy gdy nhiem.
Kit qud nghien cftu nay tuomg ddi phu hgp vdi kit qud nghien cftu trudc cfta Nguyin Duy Lam (2000, 2002) nghidn cftu khd ndn^ fte chl hodn toan nam moc trong mdi trudmg ldng ciia chitosan d ndng dp 0,15% doi vdi ndm mdc A. fumigatus va 0,2% chitosan vdi nam moc Fusarium dimerum. Kit qud cung phft hgp vdi kit qua cua Yu vd CS (2007) dd nghien cftu dnh hudmg cua ndng dp chitosan ddi vdi nam mdc gdy thdi Penicillium expansum trdn tdo, ket qud cho thay nong dp chitosan > 0,3% cd kha ndng fte chl hoan toan svr phat triln cua ndm moc P.
expansum gay thdi tren tao.
3.3. Anh hu'd'ng cua chitosan va chitosan phdi hp'p vd'i CaCl2 td'i s\f phdt trien ciia nim men ddi khang
Cdc chftng ndm men Candida sake TLl dugc nudi cay trdn mdi trudng nudc malt c6 bo sung chitosan ndng dg 0,5%. cd bd sung va khdng bd sung 0,5% CaCh. Nudi tren mdy ldc 200 vdng/phftt d 28°C. Ldy mau do OD dl kiim tra svr phat triln cfta ndm men sau m5i 6 h nudi cay trong 5 ngay. Dvra vao bdng 3 chung ta thay rdng trong mdi trudmg malt chiing nam men C.sake TLl phdt triln tot, m$t dp quang tang ddn sau 3 ngay nudi cay. Khi b6 sung 0,5%
chitosan khd ndng phat triln cfta Candida sake TLl thap hon, m$t dO quang thdp hon do chitosan
202
vd axit hftu ca cd tinh chat khang nam da Idm gidm svr phdt triln cfta ndm men.. Nhung khi kit hgp 0^%. chitosan vdd 0,5% CaCla vao mdi trudng nudc mah thi svr phdt triln cua ndm men tang ISn, tuy khdng phat triln manh bdng khi nudi cdy trong mdi trudng nudc malt. Chftng td khi bd sung 0,5% GaCl2 (chdt lam mim cation hda tri 2) cd tac dung giftp chd tl bao ndm men cd sftc dk khang vdi tac dvmg bat Igi cfta chitosan, giup cho ndm men phdt triln tot ban trong mdi trudmg CO chitosan. Kit qua nay phft hgp vdi kit qud nghien cftu cua Wilson va cdng svr (2002). Chftng ndm men Candida sake TLl thich ftng tdt tren cdng thfte thft nghiem. Vi vdy, chftng tdi se sft dung chung ndm men Candida sake TLl cftng vdi cac thanh phan la chitosan 0,5% va CaCla 0,5% cho cac nghien cftu tiep.theo.
Sang 3. Anh hu'dng cua chitosan t6i sy phat triln cua nim men Candida sake TLl va Candida oleophila LM5
STT
1 2 3 4 5 6 7 8 9 10 11 12 13 14
i
16 17 18 19 20
Thd'i gian lly m i u
6 12 18 24 30 36 42 48 54 60 66 72 78 84
H
96 102 108 114 120
Mat dp quang OD
Chung nim men Candida sake LTl DC
0,322 0,358 0,385 0,458 0,498 0,625 0,730 0,895 0,931 0,978 0,995 0,914 0,934 0,900
6^§4
0,952 0,965 0,948 0,940 0,940
CTI
.r.r 0,300
0,294 0,302 0,363 0,397 0,420 0,424 0,440 0,484 fS 0,610
«' 0,620 0,716 0,692 0,763 0,766 0,746 0,743 0,766 0,766 0,766
f ! . : — — ' CT2 0,276 0,276 0,302 0,363 0,378 0,399 0,401 0,440 0,427 0,412 0,449 0,575 0,598 0,635 0.622 0,652 0,625 0,595 0,659
0,640 /
3.4. Tde dung cOa chitosan va nim men d6i khdng cd bd sung CaCl2 din sv phdt triln nim m6c gdy thdi hdng tren thanh long
Sau khi nghien cftu tac dyng cua chitosan tdi svr phat triln cfta ndm men ddi khdng trong mdi frudng nudi cay c6 b6 sung CaCb Id mdi trudng bdo qudn cd khd ndiig thich ftng t6t hom doi vdi chiing nim men d6i khdng. Do dd, tilp tyc sft dvmg thdnh phdn ndy kit hgp vdi ndm men d6i
qud thl hien d bang 4. Nhin vao bang 4 thdy sau 7 ngay nudi cdy a Id ddi chftng cac vit Auong tren thanh long dugc nhiem ndm mdc Aspergillus niger va ivdm mdc Penicillium vdi lugng tl bao Id 1 X lo" CFU/ml cd ty le bi hdng Id 100%.. 6 Id thi nghiem cdng thfte CTI vdi ndm mdc.4.
niger cd bd sung 1 x l o ' CFU/ml te bdo nam men Candida sake TLl ty 1? vet thuang bi hdng Id 30%, vdi ndm mdc Penicillium cd bd sung te bao nam men Candida sake TLl ty le vit thuong hi hdng Id 34%. CJ CT2 chi sft dung 0,5% chitosan, vdi nam mdc Penicillium ty le vet thuong bi hdng Id 67%, vdi ndm mdc A. niger Id vet thuomg hi hdng Id 78%. Cdng thfte CT3:.thi nghiem bd sung 0,5% chitosan va CaCb 0,5% thi ty Id vit thuomg bi hdng d nhftng Id cd ndm mic Penicillium la 60%., A. niger la 69%. Cdng thfte CT4: cd dich te bdo nam men 10 CFU/ml va 0,5% chitosan, ty I? vit thuomg bi hdng d nhimg Id cd nam mdc Penicillium Id 23%, A. niger la 20%. d cdng thfte CT5 cd dich tl bao ndm men 10^ CFU/ml chfta 0,5% chitosan vd 0,5% CaCb, ty Id vit thuang bi hdng d nhimg Id cd ndm tndc Penicillium la 18%, A. niger la 16%. Nhu vdy, d nhirng vet thuomg dugc xft Iy bang dich te bdo nam men Candida sake LTl va 0,5% chitosan cd bd sung 0,5% CaCb cd ty le vet thuang bi hdng la thdp nhdt. Ket qua nay phft hgp vdi nghien cftu cfta Wilson va cdng sur, da sft dimg che phdm chfta 0,1%. chitosan +0,5% CaCla + Candida saitoana vec che sy phat trien cua nam mdc Penicillium expansum tren cam vd chanh ty 1? thdi hdng la 33% (Wilson et al, 2002).
Bing 4. Anh hirvng cua chitosan va nim men Candida sake TL1 cd bo sung CaCl2 0,5%
din sir phat triln cua nim mdc gay hdng tren qua thanh long d" nhiet do third'ng
Cdng thirc thi nghifm
OC CTI CT2 CT3 CT4 CTS
Ty le nhilm nim mdc sau 7 ngay bao quan (%) Penicillium
100 34 67 60 23 18
Aspergillus niger 100
30 78 69 20 16
IV. K^T LUAN
Chitosan cd khd nang fte chl hoan todn svr phdt triln cfta Penicilium va A. niger gdy thdi hdng qua thanh long d nong dp 0,3%. Chftng ndm men Candida sake TLl cd khd ndng fte chl sy phdt trien cua ndm mdc Penicilium vd A.niger. Kha nang fte chl svr phdt triln cfta Penicilium va A.niger gay thoi hdng thanh long cfta nam men ddi khdng Candida sake LTl dugc ndng cao khi
sft dvmg kit hgp vdi 0,5%. chitosan va 0,5% CaCh. Nghien cftu ndy md ra kha nang sft dvmg nam men ddi khang kit hgp vdi chitosan vd CaCb thdnh mdt chl pham sinh bgc an todn, hieu qua dung trong bdo qudn qua thanh long.
TAI LIEU THAM K H A O
1. Nguyin Duy Lam, 2000. Nghien cuu anh hudng ciia chitosan toi mpt s6 anh hudng cua vi sinh v^t gdy thoi qua trong bao quan sau thu hoach. Di truyin hoc vd img dung, 21-25.
2. Nguyen Duy Lam, Trdn Bdn^ Diep, 2003. So sanh hoat tinh khang ndm mdc cua cac lo?ii chitosan c6 nguon goc khae nhau trong dieu kien xu ly chiiu xa va moi trudng nuoi cdy khae nhau, Tgp chi sinh hqc (si 6), 7-12.
204
3. Rahman M. A., Mahmud T. M. M., Kadir J., Rahman R. A., Begum M. M., 2009. Enhancing the efficacy of Burkholderia cepacia B23 with calcium chloride and chitosan to control dnthracnose of papaya during storage. Plant Pathol., J. 25, 361-368.
4. Shama R.R., Singh D., Singh R., 2009. Biological control of postharvest diseases of fruits and vegetables by microbial antagonists. A review Biological Control. 50, 205-221.
5. Hoa T.T., Clark C.J., Waddell B.C., Woolf A.B., 2006. Postharvest quality of Dragon fruit {Hylocereus undatus) following dislnfesting hot air treatments. Postharvest Biology and Technology, 41.62-69.
^' X". T'. ^' ^^•^•' Zheng X.D., 2007. Synergistic effect of chitosan and Cryptococcus laurentii on inhibition of Penicillium expansum infections, InternationalJournal of Food Microbiology, 114, 261- 266.
7. Meng X.H., Qin G.Z., Tian S.P., 2010. Influences of preharvest spraying Cryptococcus laurentii combined with postharvest chitosan coating on postharvest diseases and quality of table grapes in storage, LWT - Food Science and Technology, 43, 596-601.
8. Wilson et al, 2002. Biological coating with a protective and curative effect for the control of postharvest decay. United States patent, pat.No: US 6 423 310 B1.
Summary
STUDY ON THE INFLUENCE OF BIO-COATING CONTAINING CHITOSAN AND YEAST ANTAGONISTS UPON THE GROWTH OF DRAGON FRUIT SPOILED FUNGI The study aimed to evaluate the effect of bio-coating containing chitosan and yeast antagonist Candida sake TLl to control the species of fungi Aspergillus niger and Penicillium that cause decay on dragon fruit during storage. The minimal inhibitory concentration (MIC) of chitosan on fungi Penicillium and Aspergillus niger is 0.3%. Yeast antagonist Candida sake TLl grow well on ihe medium containing 0.5% chitosan and 0.5% CaCh, the highest OD values of 0.766 after 90 h culture. Preparations of yeast antagonist Candida sake combined with 0.5% chitosan and 0.5%
CaCh can inhibit at high level the growth of Aspergillus niger and Penicillium leading to get the spoilage rate at 18% and 16% respectively.
Key words: chitosan, storage, dragon fruit, Candida sake, antagonistic, fungus.
