Mối quan hệ giữa độ ẩm à hoạt độ nước của chè đen thành phẩm trong quá trình bảo quản - Đỗ Văn Chương

Nội dung text: Mối quan hệ giữa độ ẩm à hoạt độ nước của chè đen thành phẩm trong quá trình bảo quản - Đỗ Văn Chương

1. KHOA HOC CdHG NGH£ MOI QUAIM H$ GILTA DD AM VA HDAT DO IVUDC CUA CHE DEIM THAIXIH PHAM TRDIMG QUA TRIIMH BAD QUAIM Dd van Chuong^, D^nglhilTianh Quydn^ T6MTAT D? dm va hogt dO nude ciia san phdm c6 quan h# chat che vdi nhau vi c6 y nghia rdt 16n trong c6ng ngh§ bao quan. Kdt qua nghifen ciiu cho thdy khi d§ dm ch^ tSng thi ho^t dO nu6c cQng tang. Ciing m0t loai ch6 CO do dm ban dau nhu nhau ndu bao quin trong m6i trudng c6 dO dm khdng khi thdp thi kha nang hiit dm chSm va thdi gian dat dupe dp dm cSn bing dai hon so vdi ch6 dugc bao quan trong m6i truong cd dp dm khong khi cao vi khi ch6 da d^t dupe dO dm cSn bang tuong ung voi gii tri ho^t d^ nude thi trong mdi truong bao quan dd che khdng xay ra hidn tupng but dm hiit nha dm. Khi bao quan ch^ phai dupe dua vd hpat do nuoc an toan hay chinh li dO dm cin bing cua chd thi chdt lupng ch6 mdi dn djnh trong thdi gian bao quan, nSn bao quan ch^ trong m6i trudng c6 dO dm khdng khi <70%. Da xay dyng dupe dudng hdp phy dang nbi^t cCia ch6 den thinh phdm tai nhidt dO 28''C±3. Dudng hdp phy ding nhi^t dO dm ciia che den thanh phdm cho thdy khi bidt mOt trong hai gii tri dd dm ho$c hoat dO nude (Aw) ciia ch6 thi qua dd thi se bidt dupe gii tn kia, ddng thdi xic dinh dupe khoing gidi h^n d$ dm an toin khi dua vao bao quan. Do ^ che <6,5% tuong ling Aw< 0,4 li viing an toan cho chd khi bio quin. Tir khda: Bao quan, che thanh phim, dd^m, d^im mdi trudng kh&ng khi, boat denude, LMTVANB^ L VAT L^ VA PHUONG PIUP NGlM Ciiu Thuc td da cho thdy, sdn pham che sau mpt thdi l.Vit lidu gian luu kho thi ciing vdi dp dm cua chd ting ddn Idn Che den: OP, P (che cap cao); PS, BPS (che cap till chat lupng cic loai san pham nay ciing giam ddn. thdp) ciia Xi nghidp Tinh chd Chd Kim Anh - Ddng Chdt lupng che gidm thd hidn df cho mdu nude pha hi Anh, Ha Npi, dat 9 didm khi nhap kho [1]. tdi, khdng cdn giir dupe miu nau do cd vidn vang nhu 2. Phirong phip nghidn ciiu ban dau nira; che hi mat miii vi chuydn sang miii chd - Thidt ke thi nghidm theo phuong phip yeu td cu; vi che thd va nhat [2], [4]. Chat lupng che cing vi ngau nhidn hoin toin. giam neu dp am cua chd cdng tang cao trong khodng - Kem ti-a gid thidt theo ANOVA tiidi gian bdo qudn ddi. Dp dm cua mdi trudfng vi - Xu ly sd lidu theo phuong phip tdi im kd hpach hoat dp ntrdc ciia sdn phdm cd quan hd chit che vdi hda hpp thanh true giao. nhau va cd y nghia rat Ion trong cdng nghd bao qudn. - Xic dinh cic chi tidu cdm quan theo TCVN Hem nira ddi vdi che cd rat nhidu loai san phdm che 3218-1993 [1]. Difas6 CO chat lupng khic nhau nhu che PO, P Id che cap TT X^p hang chSt living cao, chd BPS, PS (che cdp thap) thi dO dm cin bing 1 Tot 18.2-20 la bao nhidu vd gid tri hoat db nuoc la bao nhidu giiia 2 Kha 15.2-18,1 ch6 cdp cao vd che cdp thap, gii tri ndy cd thay ddi 3 Bat 11,2-15.1 hay khong? Diy la nhimg van dd can nghidn cim dd 4 Kta 7.2-11.2 khuyen cio cho nhd san xuat khi bdo qudn chd phai 5 HonK 0-7.2 CO gii tri boat dp nudfc an todn dd giu chat lupng che - Xac dinh do am theo phuong phap say khfl tot nhat ti'ong qui trinh bao qudn. Muc tidu nghidn d^n khoi lu<?ng kh6ng doi. ciiu Id phdi xic dinh dupe tai thdi didm ndo trong mdi - Do hoat do nuoc bang miy AW&3 (Anh) va tiTiong cd dp dm khdng khi khdc nhau thi dp dm ciia Pawkit (My). Tir ket qua do hoat do nuoc cOa cac che dat gid til cin bing vi gid tri ho^t dp nude an mau chi, dua trta phan mem cua thiet bi xay dung toin, tii dd giup cho cic nhi cdng nghd vi qudn ly duimg hip phu dSng nhljt dua ra chd dp cdng nghd bio qudn che phii hpp - Dung nong dd HjSO, d^ tao d6 am hiong doi nhSm keo dai thdi gian bao quan cting nhu gidm ciia khong khi theo bang 1 [8]. thi^u su xudng cdp chat lupng cua chd thdnh pham. Truong D^i hjc Kinh te KJ thuat Cong nghi?p Si. N6NG NGHIEP VA PHAT TRIEN NONG THON - KY 2 - THANG 5/2012
2. KHOA HQC C6N0 HOHt Bing 1. Ndng dO HjSOj dS t?o d* Im m6l 1. Xic dlnhddlm cin bing dia ch4 tru^g khdng khi DO in cua mdi tmimg inh huong tn;c tiip d& N6ngd0 Dd im tuong ddi khdng khi chSt lu(mg cia chi trong qui trinh bao quin. B( (X) H^0 12.75' 0.662* 40 4.44" 0.24- 5.31' 0.313- 5.%- 0.350- 7.27' 0.434' 10.81' 0.631' 12.87- 0.670" 50 4.18' 0.21' 5.20" 0.30* 5.86' 0.342' 7,32' 0.441" 10.89* 0.635" 12.87- 0.670" 60 3.93« 0.20" 5.13' 0.291' 5.78* 0.337" 7,36- 0.447" 10.89" 0.635" 12.87- 0.670' 70 3.84" 0.20» 5.11' 0.290* 5.78' 0.337' 7,36- 0.447- 10.89- 0.635- 12.87- 0.670- 80 3.84' 0.20 5.11' 0.290 5.78' 0.337' 7,36- 0.447" 10.89* 0.635' 12.8?- 0.670 90 3.84" 0.201 5.11' 0.290 5.78« 0.337' 7,36- 0.447* 10.89' 0.635' 12.87- 0.670* cvpo 3.10* 0 2.10' 0 3.10« 3.10' 3.10* 0 0 0 3.10* 0 LSD.„ 0 0 334.10 19.10* 431.10 0 0 545.10 0 273.10* 236.10* 0 (Trong Cling mdt cdt, cic kdt qui cd cimg it nhit mdt chd gidng nhau thi khdng cd ^ nghia khic nhau taip< 0,05) Ket qui d bing 1 chi ra ring: Chi OP: dO im chi tugng tang din. Sau 30 ngiy bio quin. d RH 70%, dp ban dau 6,79%, bao quan d RH 40% sau 10 ngiy dd im im chi tang lin 7,20%, d RH 80%: 10.72% va RH 9(»l: che giam xudng cdn 5,41%, sau 60 ngiy 3,93%, 70 12,75%. Cimg thdi gian dO im chi tang nhanh khi ngay la 3,84% vi bat diu tir ngiy thii 80 - 90 ngiy dd RH tang 70%, 80%, 90%. Dd Im chi tang din iin * im chi khdng giam (3,84%); tai thdi di^m niy dd im im cin bing 7,36% d mfii trudng RH 70% sau 60 ngiy chi da dat dupe dd im cin bang vdi dd im ttrong ddi bao quin, dp im cin bing 10,89% d RH 80% sau 50 ctia mdi trudng khdng khi, do v^y hidn tugrng nha Im ngiy vi d mdi trudng RH 90% thdi gian dd im chi dat khong xay ra niia. Bio quan chi d RH 50%, 60% dd do im cin bing 12,87% ngin nhat 40 ngay. Ket qua Im che cung giam so vdi dd Im ban diu ngay d nghiin cim nay ciing triing vdi kdt qui nghien aiu E nhiing ngiy diu Bin. Song 6 RH 60% da im chi giam A Leniger vi W.Spoon[9] chim hon so vdi RH 50%. Sau 60 ngay bio quan, d Dd im, hoat dd ntrdc, chit luong ciia che va cic RH 60% dd im chi giim xudng cdn 5,78% vi dat dd tinh chit bao quan liin quan chjt chi vdi nhau. DiSu im can bing 5,78% sau 60 ngiy bio quan, nhtmg d nay da chung minh ring inh hudng bitlpiciiasugia RH 50% do Im chi giim cdn 5,13% vi dat dd Im can tang do im cua chi tir 3% lin tdi 7% ddi vdi chit bing 5,11% d ngay thii 80. Nguipc lai, bio quin chi d lupng, ngudi ta nh§n thay cd mOt quan hd tuyen tinh RH cao hon 70%, 80%, 90% thi d6 im chi cd hi$n giaa dd im vdi si; siit giira vd gii ca (Norris) 64 NONG NGHI?P VA PHAT TRIEN N6NG THON - K^ 2 - THANG 5/2012
3. KHOA HOC CdNO NGH£ Bing 2. Mdi quan hd gitia dd Im vi hoat dO nude ciia chi P tai RH khic nhau T1l« EH RH RH RH RH RH gian 40% 50% 60% 70% 80% 90% (ngiy) W(V aw fr(V aw HW aw W(V aw WW aw WW 0 6,59a 0,395a 6.59a 0.395a 6.59a 0.395a 6.59J 0,395] 6.59i 0.3951 6.591 0.395d 10 5.82b 0.347b 6.37b 0.380b 6,44b 0.381b 6.821 0.403i 9.141 0.5301 11.221 0.620c 20 5.53c 0.340c 6,16c 0.358c 6.33c 0.379c 7,02h 0.423h 10.58h 0.596h 12.68h 0.680b 30 5,29d 0.310d 6.00d 0.356d 6.25d 0.370d 7.17K 0.4271! H.63K 0.648K 12.93K 0.700a 40 5.06e 0.290e 5.86e 0.342e 6.18e 0.365e 7.28f 0.436f 12.12f 0.660f 12.93f 0.700a 50 4.89f 0,260f 5.77f 0.3321 6.13f 0.360f 7.34e 0.415e 12.82e 0.690e 12.93e 0.700a 60 4.72(! 0.253(! 5.73K 0.325K 6.10B 0.360K 7.42c 0.450c 12.82c 0.690c 12.93c 0.700a 70 4.60h 0.250h 5.69h 0.320h 6.07h 0.358h 7.42a 0.450a 12.82a 0.690a 12.93a 0,700a 80 4.60i 0.250h 5.69h 0.320h 6.071 0.3581 7.42d 0.450d 12.82d 0.690d 12.93d 0.700a 90 4.60] 0.250h 5.69h 0.320h 6.07J 0.358i 7.42b 0.450b 12.82b 0.690b 12.93b 0.700a even) 0 2.10« 2.10* 3.10* 0 0 0 0 0 0 0 410* 1SD.,» 0 85.10" 193.10'' 19.10'" 0 0 0 0 0 0 0 42.10^ (Troag Cling mdt c^t, dc kdt qua cd ciing it nhit mdt chu-gidng nhau thi khdng cd y nghia khic nhau taip 10'^ dat dp im can bing. NONG NGHIEP VA PHAT TRIEN NONG THON - KY 2 - THANG 5/2012 65
4. KHOA HQC CONO WCH j Bing 4. Mdi quan h$ giOa dO Im vi boat dO nude cda chi PS tai RH khic nhau ThM RH40% RH50% Riiomi RH70* RH80% RH90% gian aw aw aw aw aw aw wot) WOO WW WW WW WOO 0 6.27a 0.372a 6.27a 0.372a 6.27a 0.372a 6.271 0,372i 6.27e 0.372] 6.27d 0.3721 10 5.34b 0.300b 6.07b 0.350b 6.1411 0.370b 6.66e 0.398] 8,67d 0.510i 10.92c 0.6191 20 4.75c 0.24 .'ic 5,84c 0.347c (i.0,5c 0.:),58i- 6.87d 0,418h 9,94c 0.583h 12.25b 0.672h 30 4.41d 0.220d 5.27d 0.298(1 5.TM 0.333d 7.03c 0.420K 10.35b 0.594B 12.54a 0.6S0e 40 3.97e 0,210i- 4,86e 0.274P 5,67c 0.330c 7,46b 0,452f 10.61a O.OOOe 12.54a 0.680f 50 3.78f 0.200f 4.72f 0.250f 5.4)1 0.307f 7,52a 0.460c 10.61a 0.600c 12.54a 0.680c O.OOOd 12.54a 60 3.71E 0.2001 4.61K 0.243B •5.12g 0.290h 7,52a 0.460<1 10.61a 0.680d 70 3,70i 0.200f 4.54h 0.235i 5.12g 0.2901 7,52a 0.460a 10.61a 0.600a 12.54a 0.680a 80 3.70] 0.200f 4.54h 0.235] .5.12K 0.290i 7,52a 0.460e 10.61a O.OOOf 12.54a 0.680s 90 3,70li 0.20O1 4.54h 0.235h 5,12K 0.290s 7,52a 0.460b 10.61a 0.600b 12.54a 0.680b CVPi) 0 2 10* 3.10* 0 2 10' 0 3,10* 0 4,10* 0 3.10* 0 l.SD„5 0 8.^.10'" 305.10" 0 2;i(i HI" 0 431.10" 0 668.10" 0 668.10" 0 (Trong Cling mdt cdt, cic kdt qua cd cung it nhit mpt chd gidng nhau thi khdng cd y nghia khic nhau taip < 0.05) Bing 5. M^i quan h^ giQa dQ dm vi hoat dQ nu6c ciia ch^ BPS tai RH khic nhau Thdi RH RH RH RH RH RH gian 40% 50% 6m 7(« 8(H 90% (ngiy) WW aw WW aw woo aw W(%) aw W(%) aw HW aw 0 6.34a 0,385a 6.34a 0.385a 6.3(a 0.385a 6.341 0.3851 6.34] 0.385J 6.34e 0.385] 10 6.08b 0.360b 6.20b 0.365b 6,30b 0.380b 6.94e 0.424e 8.841 0.5271 11.06d 0.622i 20 5.81c 0,341c 6.11c 0,360c 6,26c 0.365c 7.16d 0.429d 10.17h 0.538h 12.46c 0,678h 30 5.55d 0.320d 5.82d 0.344d 6.18d 0.360d 7,52c 0.455c 10.52s 0.5948 12.74b 0.687B 40 5.42e 0.313e 5.71e 0.330e 6.05e 0.356e 7.67b 0460a 10.76f 0.6121 12.85a 0.696e 50 5.36f 0.300f 5.65f 0.326f 5.97f 0.35 It 7.78a 0.470b 10.89c 0.619c 12.85a 0.696c 60 5.27s 0.296K 5.52K 0.318K 5.84K 0.350K 7.78a 0.470b 10.89d 0.619d 12.85a 0.696d 70 5.18h 0.292h 5.44h 0.310h 5.76h 0.3321 7.78a 0.470b 10.89a 0.619a 12.85 0.696a 80 S.lSh 0.292h 5.44h 0.310h 5.7611 0.332] 7.78a 0.470b 10.89e 0.619e 12.85a 0.6961 90 5.18h 0.292h 5.44h 0.3I0h 5.76h 0.332h 7.781 0.470b 10.89b 0.619b 12.85a 0.696b CV(%) 3.10* 2.10* 2.10* 3.10' 2.10' 0 2.10' 6.10* 0 0 2.10' 0 l.SD„ 305.10* 12.10" 193 10" 15 10" 193.10" 0 193.10" 403.10" 0 0 386.10" 0 (Trong cung mdt cdt, cic kdt qua cd cung it nhit mdt chir gidng nhau thi khong co y nghia khic nhau taip < 0,05) Ket qud a bang 4 chi ra ring: moi quan h^ giiia RH cao cd Ipi cho str phat trien vi sinh vat nhung do $m khong khi vd dO ^ cua che cap thap PS cung ngupe l?i Id moi truong bit Igi cho vi^ bdo quan cdc gi6ng nhu che cap cao. N^u bio qudn che trong RH loai san ph^ khd nhu che. <60% che CO hi^n tupng nhd am. Dp im ban dau K^t qua a bdng 5 cho thay: O RH 40%, 50%, 60% 6,27%, a RH 40%, 50% vi 60% dat do am can bing li chk dat dp dm cdn bing hrong ung Id 5,18%, 5,44%, 3,70%, 4,54% vi 5,12% sau 70 ngiy, 70 ngiy, 60 ngiy 5.76% sau 70 ngiy. 0 RH 70%, 80% vi 90% chd dat do tuong ung; di^u niy c6 nghia Id bdo qudn che a RH am can bing tuong ling Id 7,78%, 10,89%, 12,85% sau cdng thap toe dp nha am ciia che manh hon vi dp am 50 ngdy, 50 ngdy vd 40 ngiy. cdn bing dat dupe thap hon so voi che bdo trong Qua so li^u nghidn cuu ciia 5 lo?i chd OP, P, moi truong RH cao hon. FBOP, PS vi BPS cho thay: Khi ting RH 70%, 80%, 90% che co hidn tupng hiit Khi bdo qudn trong d\k\x kidn m6i truong co RH am vi t6c do hiit am ting theo RH. CT RH 80% sau 40 khdc nhau, n^u m6i truong c6 RH cao thi tdc dd hiit ngiy vi RH 90% sau 30 ngdy d6 dm ciia che dd dat dO Sm ciia chd nhanh trong nhung ngay ddu vd dat do am can bing 10,61% vd 12,54% tuong ung. M6i truong 66 NONG NGHIEP VA PHAT TRIEN NONG THON - KY 2 - THANG 5/2012
5. KHOA HQC C6NG NGH£ am can bang frong thoi gian ngin. Cu th^ Id: sau 30 thdi gid hi dp am cin bing ciia che thap. Khi bdo ngay bao qudn d RH 90% va 50 ngdy a RH 80% n^u qudn d RH >70% chd co hidn tuong hiit am, dp am moi trudng cd RH th^p toe dd hiit am ciia che cham chd ting nhanh. Khi RH cang cao thi tdc do ting am va thdi gian d^ chd dat dd im cdn bing ddi hon chd cdng nhanh. Tit cd cic miu chd bao quin d RH 80%, bao quan hong mdi hudng cd RH cao. 90% ddu xuit hidn n^m mdc sau 10-20 n^^iy bao Neu che b:io f[iiaii V' \il\ tli;i|i lln t hai hitni.ii ttii (|iian him va keo d.ii llun jjjian Ixtn qu;iii htm -;ii v<n nitu 2 Danh gia chat lir(,nig duw quan che bao quin a tnrcmg CO RH am (^711%) do iini can bing Doi vol die l^iio C|u;in (r RH -. i.\{)X. iIn ,mi ciif co Sau Khi do am chr (tai den fid am can bi'mg, tien xu hiroiig giiiin dan tiico thtVi j^Maii \'A) \\\ wvu K|| tiaiih kirni Ira rbal ln<nig bang phmmg ph;ip cam cing thap thi che co hien hufw^ nh:i :uii lU'ii llidi gian (|uaii vivi :^rhilieii ngoai hmh va hmnig ciia ( ho, k^t de do ^1 che dat ttVi do am can bang » aiig ilai, dixiir qnalhohirn,n)aiig(i Bang 6 Chat Immg cho khi dat do am cin bins bao auan 6 RH khac- nhan Loaiche RH(%) AW NgOiU hmh Mill Di^m 40 0.200 C;inli I. lie jiion, dcii lir iihirii, Iho.ing tiiycl lliom diu 19,6 50 0.290 C;inli clu- jikin, den tir nhii-ii, lho,ing tiiyet 'riioin diu 19.2 60 0.337 Ciuih che gioii, den tir [ihien. tho;ing tuyel OP 'niom 18,8 70 0.447 Den tir nhien Kem tham 12.3 80 0.635 C.inh che mem, n<iin nine xuat hien Miii moc 8.7 90 0.670 Canh che mem. nam moe xii.at hien Mui moc 8,7 40 0.250 Den lir nhien Thorn din 18.4 50 0,320 Den ttr nhien Tlimn dm 18,1 60 0.358 Den tn nhien Thoin dm 17,2 P 70 0.450 Den tu nhien Tlioang thorn 14,3 80 0.690 Nam moc xuat hien tren canh che Mui moc 10,3 90 0.700 Nam moc xuat hien tren canh che Mui moc 10,2 40 0,295 Canh che gion, den tir nhien Tlrom 17,2 50 0.350 Canh che gion, den tir nhien Tlioni 17,0 60 0.370 Canh che gion, den tir nhien llioang thorn 16,5 FBOP 70 0.460 Den tir nhien llioang thorn 16,3 80 0,714 Niun moc moc nhieu Mm moc 9,7 90 0,722 Nam moc moi nlneu iMui moc 9,1 40 0,292 Canh che gion, den hin miu tir nhien Tlioni 19,5 50 0,310 Canh che gion, den hin nau tu nhien Tliom 19,5 60 0,332 Ciinh che gion, den h(vi miu tu nhien Kem thorn 17,6 BPS 70 0,470 Den hoi miu tu nhien Kem tJioin 1,5,2 80 0,619 Nam moc xuat hien tren canh che Mui moc 13,1 90 0.696 Nam moc xu.at hien tren canh che Mil! moc 14,3 40 0.200 Den tu nhien Thorn 19,2 50 0.235 Den tunlnen Tliom 18,8 60 0.290 Den tu nhien Kem thorn 16,5 PS 70 0.460 Den tunlnen Kem thorn 15,1 80 0.600 N:im nioe xuat hien Iren canh che Mm moc 11.0 90 0.680 Ni'im moc xuat hien tren canh che Mill moc 11.5 Ket qua a bang 6 chi ra riing. doi vin ca 2 loa che hiiu het canh che mem do do im che tang len v,i nam ciip cao va che cap thrip. bao quan trong KH eao 80%, mdc xuat hien nhii^u tren be mat che, luc n.iy miii W khi dat do am cjm biing (sau 70 ngtiy bao quan) thorn etia che miit diin, thay vao do lit miu IMM NONG NGHIEP VA PHAT TRIEN NONG THON - KY 2 - THANG 5/2012 67
6. KHOA Hpc CdNG NCHfe 6 mdi trudng RH 40%, 50%, 60% chd v^n giQ dupe T "• i - - , l- '. _ r z ,:-/;- ngoai hinh vd miii vj die trung ciia timg logi chd. v'/T/'r d mdi trudng RH 70% miii thorn ciia chd da -j- - J' //.!'.-.A- gidm, kdm thorn ddi vdi chd OP, PS, BPS vd thodng - 1 thom ddi vdi chd P vd FBOP. Nhu viy k^t qui nghidn ••"• T—f' cuu 5 logi chd cho thiy: Dd Sm eOa cdc miu chd bdo .A _. . j qudn thay ddi nhidu hay it phij thuOc vio sy chdnh -'- Idch Sm giua mdi trudng khdng khi bao quanh vdi dd im CO h-ong miu chd. 6 mdi trudng RH thdp ( 70% thi chd cd hidn tupng hiit im, - Gid tri Aw khdng khdc nhau ddi vdi mdi loai che tdc dp hiit am cdng ting khi RH cang ting, sau 30-50 md nd phu thudc vao nhi^t dp va RH. Khi bi^t gid tri ngdy dp am chd dat dp am cin bing. Ndn bao quan dp im ciia chd thi cd thd bidt dupe gia tn hoat dd chd trong mdi trudng cd do am khdng khi 0,65) tir dd chii ddng bi^t duoc cho cdc phdn ung xdy ra. Su bidn doi ciia sin phdm dd Im an toin ciia chd khi dua vdo bdo quan. xay ra dupe hay khdng phu thudc nhidu vdo Aw, hay - Dudng cong hip phy ding nhidt chia thdnh ndi cich khic Aw cua san phim chinh li cdi khod nhimg vung khac nhau theo tinh trang Udn kdt ciia cho su dn dinh chit lupng ciia san pham. Do viy, xdc nude trong chd den nhu sau: dinh gid tri an todn cua Aw vi dO dm cua chd trudc + Viing A: trdn dudng cong bi^u hidn lupng nude khi dua vdo bdo qudn d^ han ch^ thip nhdt cdc phan hdp thu lidn k^t chit chd vdi phdn tii che, tuong ung irng xay ra h-ong qud trinh bao quan Id rat quan trpng cdn bing vdi Aw che thdp. vd can thi^t. + Vung B: virng cd Aw 0,2 - 0,4; ddy Id viing an Mudn kdo ddi thdi gian bao quan ciia cic san todn cho san phdm bao quan. pham thuong sii diing cdc ky thuit dd ha thip gid trj + Virng C: lupng nude ndm trong virng ndy (Av^ Aw ciia san phim xudng gid trj an todn d^ nhdm h?in 0,4). Phdn nude nay rdt linh ddng dk dang tham gia ch^ cic phan ung xdy ra. Ti^n hinh xac dinh Aw ung vio cic phan Ving lam hu hdng san pham trong bao vdi gii tri dd am cua 5 loai chd a RH khic nhau 40%, quan. Vdi dd dm Id 7,72% thi Aw 0,460. vdi Aw 0,554 50%, 60%, 70%, 80%, 90% tai nhidt dd xac dinh 28 ± 3°C. thi dd dm li 9,58%; khi dd am ting Idn 13.26 thi Aw Ket qua th^ hidn d cdc bdng 1, 2, 3, 4, 5; tir dd xdy tdng Idn Id 0,714. dung dudng hap phu ding nhidt cua chd den dianh Qua dd thi ta thiy dd am an toin cua che khi phim vd duoc trinh biy a hinh 1. dua vio bao quan tdt nhdt la < 6,5% thi Aw an todnkh i 68 N6NG NGHIEP VA PHAT TRIEN N6NG THON - KY 2 - THANG 5/2012
7. KHOA HQC CdNG NGH| bao quin che tuang ling la: 70% thi che c6 hien tugng hiit Dai hpc Bdch khoa Hd Noi. am; tdc do hiit im cdng tdng Ithi RH cdng tSng. sau e.Cao van Hung, et al. (2006)- Nghien cim cong 30-50 ngdy d6 im che dat dp dm cdn bdng. Nen bao nghe bdo quan che thdnh phdm npi tieu vd xudt quan che trong moi truing co d6 dm Ichong Ithi khdu- Bap cao khoa hpc &k tai cdp 86 NN vd PTNT <70)l. Hd Npi. - Da xay dtmg dupe duftng hdp phit dang nhlM 7.V0 Thy Thu, et al. (2001)- Cic hop chat hoi ciia che den thdnh phdm tai nhi^t dO 28°C±3. Duftng hoc cd trong chd Nhd xudt ban N6ng nghiep Ha Noi. hap phiJ ddng nhiet ciia che den thanh phdm cho 8.Le Ngpc Tii. et al. (2001) Hoi hoc tiiuc phim. thay: Idii bi^t mot trong hai gid trj dp dm ho$c hoat Nhd xuat bdn Khoa hpc Ky thuat. do nuoc (Aw) ciia chi thi qua 66 thi se bi^t dupe gid 9.H. A. Leniger vd W.Sppon, Lubuta. T. P, In kia, d6ng thfti xdc djnh dupe khoang gid tri hoat Kaanane A, Chen J. 1985. The effect of temparature do nuoc an todn doi vfti che khi bdo quan Id Aw < 0,4. on the moisture Sorption is othesms and water activity shiltdehydratedfood.]. Food Sci. 385-391. lO.Rlchard - Molard D., Lesaga L. (1985). Food Till Ku THAM nUa rnycrobilogy and water activity centiedr Hechrhes 1. Bp N6ng nghiep va PTNT (2001)- Tuydn tip agro Alimenain de Nantes -France 165-179. tidu chuan ndng nghidp Vidt Nam - Vu Khoa hpc 11. Water activity and states the current process Cdng nghe vd Chat lupng Thuc pham- Hd Npi. in relation to food hnctionality and quality cotrol (1988). Food technology. Thai Lan. 488 - 492. OCT. RELATIONSHIP BETWEEN THE MOISTUKE AND WATER ACTIVnY OF BLACK TEA FINISHED PRODUCTS DURING STORAGE Do Van Chuong, Dang Thi Thanh Quyen Summary Determining the appropriate specificapons in the preservation process in general tea and black tea in particular not finished the long time preservation, but also preserves the quality of tea products in a stable time. Results of research of equilibrium moisture content of tea was deteimined finished tea should be stored at an ambient relative humidity <70%. Has been developed absorption isotherm of finished black tea at a temperature 28°C ± 3. absorption isothemi of finished black tea that knowing one of two values of relative humidity or tea water activityb (Aw) is the graph will know the value of the other, and identify some limitations tea moisture <6.5% respectively Aw <0.4 IS a safety zone for the preseiv.i^^pf tea. In detennining the relationship between water activity (Aw) and moisture content of tea ui different ecological zones have concluded tiie safety of tea moisture when stored at delta <6.096. midlands < 6.5% and 7.0% mountainous. Keyword- Preservation, teadmslied, moisture, relativeliumidily, wateractivity, Ngtrfti phdn bi^n: TS. Nguyen Manh NONG NGHIEP VA PHAT TRIEN N6NG TH6N - KY 2 - THANG 5/2012 69