TIU CHUN VIT NAM

TIU CHUN QUC GIATCVN 9332 : 2012ISO/TS 19036 : 2006WITH AMENDMENT 1 : 2009VI SINH VT TRONG THC PHM V THC N CHN NUI - HNG DN C LNG KHNG M BO O I VI CC PHP PHN TCH NH LNGMicrobiology of food and animal feeding stuffs - Guidelines for the estimation of measurement uncertainty for quantitative determinationLi ni u

TCVN 9332:2012 hon ton tng ng vi ISO/TS 19036:2006 v B sung 1:2009;

TCVN 9332:2012 do Vin Kim nghim an ton v sinh thc phm quc gia bin son. B Y t ngh, Tng cc Tiu chun o lng Cht lng thm nh, B Khoa hc v Cng ngh cng b.Li gii thiu

Hng dn biu th khng m bo o (GUM)[15] l phng php chun c chp nhn rng ri, c khuyn co dng c lng cc phn b phng sai ca tng ngun ring bit gy ra khng m bo o trong qu trnh o lng, nh c minh ha trong cc v d. Sau , khng m bo o tng hp thu c bng cch s dng cc nguyn tc v s lan truyn v khng m bo o. Phng php tip cn ny c m t theo cch thc tin hn v o lng phn tch, ch yu lin quan n phn tch bn cht ha hc cp trong hng dn EURACHEM/CITAC [16] v vi sinh vt cp trong Ti liu tham kho [17].

Tiu ban k thut ISO/TC 34/SC 9 cho rng phng php tng bc (step-by-step) nh trn khng c p dng tha ng khi phn tch vi sinh vt trong thc phm v kh xy dng m hnh thc s ton din v qu trnh o. Do c th khng nhn bit c mt ngun thay i ng k nn c nguy c nh gi khng ng mc gi tr khng m bo o (MU) Ngoi ra, s kh nh lng chnh xc s gp phn ca tng bc ring bit trong qu trnh phn tch vi sinh vt thc phm do:

- i tng phn tch l sinh vt sng m trng thi sinh l ca n c th thay i vi mc ln;

- mc ch ca php phn tch bao gm cc chng, cc loi hoc cc ging khc nhau.

Ni cch khc, phn tch vi sinh vt khng th l h thng o lng chnh xc v c lng ng gi tr thng k v MU.

V vy, Tiu ban k thut ISO/TC 34/SC 9 chn phng php trn-di (top-down) hay tng th (global) i vi MU, da trn lch chun ti lp ca kt qu cui cng ca qu trnh o. y l phng php da vo cc kt qu thc nghim (s lp li ca cng mt php phn tch) m trong lnh vc vi sinh vt, n dng nh c ngha hn phng php tng bc.

Phng php tng th c Ban k thut ISO/TC 69 p dng cc phng php thng k, SC 6 Phng php v kt qu o lng a vo s dng trong ISO/TS 21748. Tiu chun ny lm sng t phng php tng bc v phng php tng th khng loi tr nhau, v tt c cc thnh phn ca MU c th c tnh n trong vic thc hin tng th qu trnh phn tch, c trng bi chm v chch quan st c.VI SINH VT TRONG THC PHM V THC N CHN NUI - HNG DN C LNG KHNG M BO O I VI CC PHP PHN TCH NH LNGMicrobiology of food and animal feeding stuffs - Guidelines for the estimation of measurement uncertainty for quantitative determination1. Phm vi p dng

Tiu chun ny a ra hng dn c lng v biu th khng m bo o (MU) lin quan n cc kt qu nh lng vi sinh vt trong thc phm.

Tiu chun ny p dng cho cc phn tch nh lng s dng k thut m khun lc hoc phng php s dng thit b khc trong:

- thc phm v thc n chn nui;

- cc mu mi trng trong khu vc sn xut v ch bin thc phm.

Tiu chun ny khng p dng cho vic nh lng s dng k thut tnh s c xc sut ln nht.

Trong tiu chun ny, MU c c lng bng cch s dng phng php gin lc a vo trong tnh phn b Poisson v sau c th p dng cho bt k kt qu no, bao gm cc s m thp v/hoc s lng thp vi sinh vt1).

Phng php nu trong tiu chun ny l phng php tng th da vo lch chun ca ti lp ca kt qu o cui cng.

2. Thut ng v nh ngha

Trong tiu chun ny s dng cc thut ng v nh ngha sau:

2.1. khng m bo (ca php o) [uncertainty (of measurement)]

Thng s gn lin vi kt qu ca php o, c trng cho s phn tn cc gi tr c th quy cho i lng o mt cch hp l.

CH THCH 1: V d, thng s c th l lch chun (hoc bi s ca lch chun) hoc mt na khong vi mc tin cy c cng b.CH THCH 2: Nhn chung, khng m bo o bao gm nhiu thnh phn. Mt s trong cc thnh phn ny c th c nh gi t phn b thng k ca cc kt qu ca mt dy php o v c th c c trng bi cc lch chun thc nghim. Cc thnh phn khc, cng c th c c trng bi cc lch chun c nh gi t cc phn b xc sut c tha nhn da trn thc nghim hoc thng tin khc.

CH THCH 3: Kt qu ca php o c hiu l s c lng tt nht gi tr ca i lng o v ton b cc thnh phn ca khng m bo, bao gm cc tc ng mang tnh h thng pht sinh nh cc thnh phn lin quan n vic hiu chnh v chun chnh, gp phn vo s phn tn.

[GUM:1993(15)]2.2. khng m bo chun (standard uncertainty)u(Xi)

khng m bo ca kt qu php o c th hin nh lch chun.

[GUM:1993(15)]

2.3. khng m bo chun tng hp (combined standard uncertainty)

uc(y) khng m bo chun ca kt qu php o khi kt qu nhn c t cc gi tr ca mt s i lng khc, tng ng vi cn bc hai dng ca tng cc s hng. Cc s hng khc nhau hoc phng sai ca cc i lng khc ny tc ng ty thuc vo cc gi tr kt qu php o nh th no khi thay i chng.

[GUM:1993 (15)]

2.4. khng m bo o m rng (expanded uncertainly)

Ui lng xc nh mt khong bao quanh kt qu ca php o mong mun s cha phn ln phn b ca cc gi tr c th quy mt cch hp l cho i lng o.

CH THCH 1: Phn ny c th c coi nh xc xut bao ph hoc tin cy ca khong.

CH THCH 2: kt hp tin cy c trng vi khong c xc nh bi khng m bo m rng i hi cc gi nh hin hoc n lin quan n phn b xc sut c trng bi kt qu php o v khng m bo chun kt hp ca n. tin cy c th quy cho khong ny ch phn bit trong phm vi c th chng minh c nhng gi nh nh vy.

[GUM:1993 (15)]CH THCH 3: khng m bo o m rng U c tnh t khng m bo o chun tng hp uc(y) v h s ph k theo cng thc

U = kuc(y)

2.5. H s ph (coverage factor)k

H s c s dng lm s nhn vi khng m bo chun tng hp c c khng m bo o m rng.

CH THCH: H s ph k thng trong phm vi t 2 n 3.

[GUM:1993(15)].

2.6. chch (bias)

Mc sai khc gia gi tr k vng ca cc kt qu th nghim v gi tr quy chiu c chp nhn.

CH THCH: chch l sai s h thng tng hp khc vi sai s ngu nhin. C th c mt hay nhiu thnh phn sai s h thng ng gp vo chch. S sai khc h thng so vi gi tr quy chiu c chp nhn cng ln th chch cng ln.

[TCVN 8244-1:2010 (ISO 3534-1:2006)].

3. Nguyn tc

3.1. Phng php tng th c lng khng m bo o (MU)

Tiu chun ny a ra phng php tng th c chp nhn c lng khng m bo o. khng m bo o da trn bin thin chung ca c qu trnh dn n kt qu phn tch. bin thin chung ny bao gm c chm thy c (thnh phn ngu nhin) v chch (thnh phn h thng). Trong thc t ca lnh vc vi sinh vt trong thc phm, ch c chm c a vo tnh ton (xem 3.2).

Phng php tng th c lng MU trong tiu chun ny thu c t c lng thc nghim lch chun ti lp kt qu cui cng ca qu trnh o hon chnh. lch chun ny tng ng vi khng m bo chun tng hp (xem 4.1).

Phng php tng th c th c coi nh mt h thng hp en (nh c minh ha trong Hnh 1) xc nh cc ngun chnh ca khng m bo khi phn tch vi sinh trong thc phm. S nh vy c th gip ch trong vic xc nh cc ngun ca khng m bo, c bao gm hoc khng bi quy trnh th nghim chn.

Hnh 1 - S v cc ngun chnh ca khng m bo o khi phn tch vi sinh vt trong thc phm, v phng php hp en v khng m bo o

Trong Hnh 1, vic ly mu (ly ra cc n v mu th nghim t l c kim sot) ni ln mt phn ngha (nu khng phi l ch yu) ca sai s tng nhng khng phi l phn khng m bo gn lin vi chnh php o. Mu con c ngha l phn mu th ly ra t mu phn tch (mt trong nhng n v ly ra t l). Phn mu th ny c dng chun b dung dch huyn ph ban u cc k thut nh lng vi khun theo TCVN 6507-1 (ISO 6887-1). Cc ngun chnh ca khng m bo trong qu trnh phn tch l ngi phn tch/thi gian v thit b/mi trng nui cy/thuc th. Cui cng, cc sai s ngu nhin h thng thng d l ci khng c gii thch bi cc yu t trc v thng c nh gi trong phng th nghim trong cc iu kin lp li.

Trong khi , s chp nhn phng php tng th ny i hi cc kt qu ca qu trnh o phi chng minh l c kim sot.

3.2. Xem xt chch

iu thng c cn nhc l khng a chch vo trong tnh khng m bo o theo kinh nghim v bn cht nh lng vi sinh vt. Ni cch khc, quy trnh phn tch xc nh trc tip kt qu ca php o, v d s khun lc trn n v mu. V vy, trong thc t khng th xc nh gi tr thc cn thit cho quyt nh chch. Thm ch khi s dng cc mu chun c chng nhn, hoc cc gi tr nhn c t cc th nghim lin phng cng ch nh gi c mt phn chch tng.Trong khi , iu c tha nhn l phn chch c th nh gi qua cc nghin cu lin phng c s dng trong hai la chn cn li ca tiu chun ny nh gi lch chun ti lp (xem iu 6 v iu 7). Phng php tnh n thnh phn chch ca khng m bo khng c m t trong tiu chun ny. Tuy vy, ngay c khi thnh phn chch ca MU khng c nh gi chnh thc th cng c th ch ra chch ca phng th nghim bng cch kim sot n v tham gia, v d: trong th nghim thnh tho lin phng hoc bng cch th nghim cc mu chun ( c chng nhn).

4. Cc kha cnh chung

4.1. khng m bo chun tng hp

Khi cc thnh phn chnh ca khng m bo o c kim sot (xem 3.1), thng thng th khng m bo chun tng hp uc(y) (2.3) l s kt hp khng m bo chun lin quan n chm v ti chch, nu thch hp.

khng m bo chun tng hp c lng trong tiu chun ny bng lch chun ti lp thc nghim kt qu cui cng ca php o, tng hp vi mt thnh phn bng phn b Poisson.

CH THCH: Phng php kt hp khng m bo chun lin quan n chch khng c m t y.

4.2. lch chun ti lp

Ba kh nng khc nhau c la chn c tnh lch chun ti lp (sR) theo th t u tin sau:

- S la chn th nht: lch chun ti lp trong phng th nghim;

- S la chn th hai: lch chun ti lp ca phng php nhn c t nghin cu lin phng;

- S la chn th ba: lch chun ti lp nhn c t th nghim thnh tho lin phng.

u tin hon ton cho s la chn th nht v c th nghim vi mt quy trnh c m t chi tit.

Cc nguyn tc chung c lng lch chun ti lp c a ra trong 4.4 v mi s la chn c m t chi tit t iu 5 n iu 7.

4.3. khng m bo m rng

khng m bo m rng U (c nh ngha bi GUM) c c t khng m bo o chun tng hp uc(y) vi h s ph k c chn trong tiu chun ny l 2 (tng ng vi tin cy xp x 95 %):

U = 2uc(y)

4.4. Nguyn tc chung cho c lng lch chun ti lp

Thut ng hp en c m t trong tiu chun ny cn c tnh n ti mc c th cc ngun khng m bo theo Hnh 1. C th, phng th nghim cn am hiu v s phn b cc vi sinh vt bn trong cc nn mu th nghim a vo c lng khng m bo ca thnh phn mu con (xem 3.1).

lch chun ti lp s c c lng cho mi loi vi sinh vt ch (hoc nhm cc vi sinh vt ch thch hp) v i vi mi nn mu (hoc nhm cc nn mu tng t) theo phng php phng th nghim s dng a ra cc kt qu thng ngy.

CH THCH 1: Thut ng tng t c ngha l nhm cc vi sinh vt/cc phng php hoc nhm cc nn mu a ra cc gi tr tng ng ca MU.

CH THCH 2: c lng MU lin quan vi phng th nghim v mi lin kt gia kt qu th v MU, c xc nh vi cc iu kin nh r nh ngi phn tch, quy trnh th nghim, thit b, thuc th... c lng MU khng th hin c trng ca phng php phn tch m th hin c trng cho phng th nghim thc hin phng php phn tch.

Theo cc nguyn tc ca TCVN ISO/IEC 17025, cc yu t quyt nh lin quan n phng php hoc phng th nghim c kh nng nh hng n kt qu php o cn c xc nh v chng minh l c kim sot. V d v cc yu t quyt nh nh vy l ngun gc v phn loi nh mi trng nui cy v/hoc cc thuc th khc (nh cc thuc th dng khng nh), cc k thut m (th cng hay t ng), ngi phn tch hoc nhm ngi phn tch... Vic tip tc gim st c lng MU cn phi cho thy n vn thch ng v cc kt qu th nghim u c kim sot. nh gi li c lng MU l cn thit khi c s thay i ca bt k yu t quyt nh no.

5. lch chun ti lp trong phng th nghim

5.1. Yu cu chung

lch chun ti lp trong phng th nghim l phn thng hay c la chn a ra khng m bo o gn vi cc kt qu bo co ca phng th nghim, v vy, l nguyn tc xc nh khng m bo o. iu ny ph hp vi trng hp in hnh ca chm trung gian c a ra trong TCVN 6910-3 (ISO 5725-3). Mt hn ch v l thuyt ca s la chn ny l khng th a chch vo tnh ton.

5.2. Quy trnh th nghim

5.2.1. Yu cu chung

Vi sinh vt trong thc phm, khng th loi tr nh hng ca nn mu ti khng m bo o; do quy trnh th nghim phi tnh n nh hng ca vic ly phn mu th t mu phng th nghim (v d: mu thc phm c kim tra).i vi mi vi sinh vt ch [hoc nhm vi sinh vt thch hp 2)] v loi nn mu, quy trnh th nghim (5.2.2) cn tin hnh t nht 10 mu trn cng mt loi nn. Vic thc hin quy trnh nn lp li trong nhiu ngy khc nhau bao trm nhng bin i cc iu kin th nghim theo thi gian. Qu trnh ny cng tp hp li cc d liu tng thi im mt.

S loi nn mu th nghim ph thuc vo tnh a dng ca nn mu do phng th nghim phn tch hng ngy. Cn la chn cc nn mu i din cho cc gi tr MU, vi kiu nn mu phng th nghim phn tch v c lin quan ti cc vi sinh vt th nghim. Ph Ic A a ra hng dn v s la chn ny, qua vic cung cp kt qu ca cc th nghim c thc hin nhiu quc gia vi mc ch nh gi thnh phn MU gn vi mu con ca phn mu th phng th nghim v chun b huyn ph ban u. Hng dn thm c cp trong Ph lc B ca ISO 16140:2003.

Vic tnh ton lch chun bng d liu dng log n nh s dao ng ti lp nhiu mc nhim v cc kt qu c s m thp khng c s dng trong tnh ton (xem 5.3). V vy khng cn phi c lng lch chun ti lp cho tng mc nhim. Tuy nhin, khi c th, nn chn cc mu v/hoc cc dung dch pha long sao cho bao ph dy nng vn th nghim hng ngy.

Nn dng mu b nhim t nhin khi c th, v chng lm cho c tnh khng m bo o st vi cc kt qu c trng ca nhng mu ny hn. Ngoi ra, trng thi sinh l ca vi sinh vt (v d: b c ch) c th cng nh hng n bin thin ca cc kt qu do vy nn ging vi cc iu kin c tnh trong th nghim hng ngy.

Nu cn gy nhim th phi kim sot cht ch sao cho khng a thm vo yu t lm bin thin ti cc kt qu. Vic gy nhim nn thit k sao cho ging vi nhim thc ti mc c th (v d. bng cch s dng cc vi sinh vt b c ch v bao gm c vi sinh vt cnh tranh/qun th nn).

5.2.2. M tQuy trnh c m t trong Hnh 2.

i vi mi mu th, mi ngi phn tch ly mt phn kim tra v chun b mt dung dch huyn ph ban u, thc hin mt ln phn tch. Tin hnh phn tch nh thng l (v d: chun b mt dy cc pha long thp phn, cy 1 hoc 2 a cho mi pha long).

CH THCH 1: Trong thc t, ngi phn tch c th l mt nhm cc nhn vin k thut, mi ngi thc hin mt phn ca quy trnh. Trong trng hp , nhm ny c coi l mt ngi phn tch v bt k s thay i v phn cng nhim v ca thnh vin u c coi nh mt ngi phn tch khc.

CH THCH 2: Quy trnh ny theo phng php hp en c m t trong 3.1. Cc ngun khc nhau ca khng m bo nh mu con, bn cht ca nn mu, sai s ngu nhin thng d, ngi phn tch/thi gian c coi l ng thi nhng khng nh gi ring r.

Hnh 2 - Quy trnh th nghim tnh lch chun ti lp phng th nghim

Cc iu kin A v B nn khc hn nhau n mc c th chp nhn c v l tng l gm nhiu s thay i nht t ngy ny qua ngy khc trong phng th nghim, nh cc k thut vin, cc m mi trng nui cy v cc thuc th, my trn mu, my o pH, cc t m, thi gian phn tch... Nu cc mu thc phm b nhim c chng minh l n nh (iu ny l trng hp him trong vi sinh vt thc phm), cc iu kin A v B cng nn gn lin vi cc ngy phn tch khc nhau.

5.2.3. S dng

Hnh 3 ch ra cc ngun chnh ca khng m bo c bao hm trong quy trnh ny cng nh cc ngun c loi tr (ly mu v chch).

CH THCH: Cc ngun loi tr c nh du gch cho.

Hnh 3 - Cc ngun chnh ca khng m bo o c bao ph hoc loi tr trong th nghim v ti lp ni b phng th nghim

Nh gii thch trong 4.2.1, quy trnh ny kt hp nh hng ca vic ly phn mu th trong c lng khng m bo tng. Ngoi ra, thc t l vi sinh vt trong thc phm l do b nhim t nhin vo cc sn phm thc phm (c bit l cc sn phm rn, sau qu trnh ch bin, lm chn...) thng ng nht khng cao. Vic tnh n bin thin ca cc kt qu do s khng ng nht ny l quan trng khi nh gi mc ph hp ca mu th t kt qu phn tch (nh cc ch tiu vi sinh vt) so vi gii hn qui nh.

CH THCH: Nu thc hin gy nhim nhn to dung dch huyn ph ban u (mt kh nng trong quy trnh Hnh 2), thnh phn ca khng m bo o do gy nhim khng ng nht trn nn mu khng c tnh n.

Tuy nhin, trong mt s trng hp, tnh kh thi ca quy trnh ny c th khng cao. Vic phn b trong tnh hung b nhim t nhin gn cht ch vi loi nn mu gii thch v sao quy trnh th nghim cn c lp li vi mi loi nn mu (hoc nhm cc nn mu thch hp) thng c phn tch phng th nghim. iu ny c th dn n cc th nghim c phm vi qu rng khi phng th nghim phn tch rt nhiu loi nn mu.

Cui cng, nh cp trong 3.2, kh nng gp phn ca chch vo khng m bo o khng c cp trong quy trnh ny.

5.3. Tnh kt qu

Cc th nghim cn c thc hin sao cho m bo c rng s lng khun lc ln thch hp a vo tnh kt qu. Nn loi b kt qu m di 10 khun lc. Cc kt qu m t 10 n 30 khun lc cng ch c tnh n khi lch chun ti lp sR mong mun ln hn 0,2 log10 (cfu/g) hoc 0,2 log10 (cfu/ml).

CH THCH 1: Gii hn ca 10 (hoc 30) khun lc p dng cho tng s khun lc m c trn tt c cc a, (C.

CH THCH 2: Gii hn ny ch lin quan n cc trng hp c th trong thc nghim v lch chun ti lp ni b phng th nghim (ngha l cc th nghim c mc ch c bit nh gi khng m bo o) v khng s dng lch chun ny tnh khng m bo o i vi mu th mi (xem iu 8).

Thng thng, trc khi tnh ton, d liu (cc kt qu m vi sinh vt) theo cfu/g hoc cfu/ml s c chuyn thnh dng log10(cfu/g) hoc Iog10(cfu/ml).

CH THCH 3: Theo TCVN 6398-11 (ISO 31-11), k hiu cho cc loga thp phn l lg. Tuy nhin, trong cu trc ca tiu chun ny, k hiu log10 thng c dng rng ri trong cc phng th nghim vi sinh vt thc phm.

Tnh ton lch chun ti lp sR i vi n mu ca mt nn mu c a ra nh sau:

Trong :

yij l d liu c chuyn thnh dng log, di dng log10(cfu/g) hoc log10(cfu/ml);

i l ch s mu, i = 1 n n (n ( 10);

j l ch s ca iu kin ti lp, j = A hoc B.

V d nh lng vi sinh vt hiu kh a m trong tht gia cm trn c nu trong Bng 1.

Bng 1 - Tnh lch chun ti lp - V d v nh lng vi sinh vt hiu kh trong tht gia cm trn

iXiAXiByiA = log10(XiA)yiB = log10(XiB)

16,7 x 1048,7 x 1044,834,940,0064

27,1 x 1066,2 x 1066,856,790,0017

33,5 x 1054,4 x 1055,545,640,0049

41,0 x 1074,3 x 1067,006,630,0672

51,9 x 1071,7 x 1077,287,230,0012

62,3 x 1051,5 x 1055,365,180,0172

75,3 x 1084,1 x 1088,728,610,0062

81,0 x 1041,2 x 1044,004,080,0031

93,0 x 1041,3 x 1044,484,110,0659

101,1 x 1082,2 x 1088,048,340,0453

S dng d liu c chuyn di dng log yif, lch chun ti lp l:

6. lch chun ti lp ca phng php thu c t nghin cu lin phng

6.1. Yu cu chung

Nu phng php s dng thng xuyn ti phng th nghim c a vo nghin cu lin phng xc nhn gi tr s dng th phng th nghim c th s dng lch chun ti lp ca phng php c lng khng m bo o trong cc iu kin nht nh (xem di y). iu kin tin quyt ny c nh gi bi thc t rng lch chun nhn c t nghin cu lin phng gn lin vi phng php v khng lin quan n phng th nghim a ra bo co khng m bo o ca cc kt qu ca phng th nghim .Cc iu kin ny nh sau:

- chch phng th nghim phi tng ng vi d liu k vng trn c s ca cc c lng lp li v ti lp nhn c t nghin cu lin phng;

- chm t c bi cc php o trong phng th nghim phi tng ng vi d liu k vng t nhng c lng lp li v ti lp nhn c t nghin cu lin phng;

- nghin cu lin phng bao ph hp l tt c cc ngun ca khng m bo o (c bit l vic chun b mu v ng ha mu).

Quy trnh kim tra cc iu kin ny c ph hp hay khng v lm th no kt hp c lng khng m bo o tng hp thm vi cc yu t khng bao hm trong nghin cu lin phng, c m t chi tit trong ISO/TS 21748.

6.2. S dng cho vi sinh vt trong thc phm

Hnh 4 ch ra cc ngun chnh ca khng m bo o c cp trong quy trnh ny cng nh ngun c loi tr (ly mu).

CH THCH: Cc ngun loi tr c nh du gch cho.

Hnh 4 - Cc ngun chnh ca khng m bo o c bao gm hoc loi tr bi ti lp gia cc phng th nghimM rng ra, vic ly mu con, chun b dung dch pha long ban u cng nh nh hng ca nn mu c cp ph thuc vo m hnh b tr th nghim.

Phng php ny cho php mt phng th nghim tham gia nghin cu lin phng nh gi chch phng th nghim ca mnh, chch l mt ngun ca MU. y l kha cnh khng c nu chi tit trong tiu chun ny.

Tuy nhin, i vi vi sinh vt trong thc phm, phng php ny c mt vi hn ch c trnh by di y. iu ny gii thch v sao n ch c cn nhc nh s la chn th 2.

Ngoi ra, cn kim sot chm v chch ca phng th nghim ph hp vi cc gi tr tng ng ca nghin cu lin phng ca phng php. y l iu cn thit ghi nhn rng ch c mt s gii hn cc thng s ti lp nhn c t cc nghin cu lin phng chun ha cc phng php tham chiu [v d: c lng B. cereus trong TCVN 4992 (ISO 7932). C. perfringens trong TCVN 4991 (ISO 7937), Staphylococci dng tnh coagulase trong TCVN 4830-1 (ISO 6888-1) v TCVN 4830-2 (ISO 6888-2) v L. monocytogenes trong TCVN 7700-2 (ISO 11290-2)].

Hn na, kh c th khi qut ha nt c trng trong phn tch mu hng ngy ca phng th nghim. Cc gi tr chm t nghin cu lin phng s c th hin di gii hn chm c xc nh khi tng hp vi nn mu, chng vi sinh vt, mc nhim... v cho qun th vi sinh vt nn (nu c mt).

Cui cng l a ra yu cu v tnh ng nht i vi nhng mu c s dng cho cc nghin cu lin phng th nghim. Vic cn phi gi n cc phng th nghim cc mu c lm ng nht v n nh nhm lm gim s bin i t nhin trong mu b gy nhim c th thy trong th nghim v l nguyn nhn dn n c lng di ngng ca khng m bo.

7. lch chun ti lp t th nghim thnh tho ni b phng th nghim

Nu phng th nghim tham gia th nghim lin phng, th phng th nghim c th s dng lch chun ti lp t kt qu so snh lin phng suy ra khng m bo o, theo cc iu kin sau:

- trong qu trnh th nghim lin phng, phng th nghim s dng cc phng php vn phn tch thng ngy;

- cc mu s dng trong chng trnh so snh lin phng c th so snh c (loi nn mu v mc b nhim) vi cc mu c phn tch hng ngy;

- cc phng th nghim tham gia khng s dng cc phng php khc nhau, hoc c s lng thch hp cc thnh vin tham gia s dng phng php nh nhau, cho php c lng chnh xc lch chun ti lp.Hnh 4 ch ra cc ngun chnh ca khng m bo o c th hin bi quy trnh ny cng nh quy trnh loi tr vic ly mu.

Mc tiu ca phng php ny l gip phng th nghim tham gia vo th nghim lin phng c th nh gi thnh phn chch ti khng m bo o. Kha cnh khng c nu chi tit trong tiu chun ny.

8. Tnh ton khng m bo o m rng8.1. Gii thiuGi nh rng s n v hnh thnh khun lc trong cc a petri tun theo phn b Poisson. Sai s ngu nhin c tnh n trong c lng khng m bo m rng c m t trong 8.2.

CH THCH: Cc tnh ton c m t c lng lch chun ti lp trong phng th nghim (xem 5.3) khng cp n sai s ngu nhin theo phn b Poisson, c ngha rng chng loi ra cc kt qu nh lng da vo s m thp cc khun lc m c.

8.2. Tnh ton

8.2.1. Trng hp chung

Biu th kt qu th nghim y = log10x, khi khng m bo o m rng, U, vi h s ph l 2 (tng ng vi tin cy xp x 95 %) c tnh theo Cng thc (1):

Trong :

sR l lch chun ti lp;

0,18861/(C l thnh phn phng sai theo phn b Poisson, trong (C l tng s khun lc m c trn tt c cc a.

CH THCH: T s thu c theo tnh cht l thuyt ca phn b Poisson (s bng nhau gia mong mun v phng sai trc tip dn n h s bin thin c tnh theo Poisson, CV = 1/) v mt php tnh gn ng thnh phn phng sai Poisson trn thang logarit xp x bng bnh phng h s bin thin, (CV)2, nu dng thang logarit t nhin v (log10e)2 = 0,18861 x (CV)2 nu dng thang logarit thp phn.

khng m bo o theo Cng thc (1) ph thuc vo c lch chun ti lp c c lng t thc nghim vi cc s m cao, sR, v tng s a m ca mu c nghin cu, (C. n gin ha, nn dng Cng thc (1) khi c th.8.2.2. S khc nhau gia cc s m thp v s m cao (khng bt buc)

i vi cc s m cao, s hng th hai trong cn bc hai, s hng Poisson ph thuc vo (C, c th c b qua v Cng thc (1) c gin lc nh sau:

U = 2sR

(2)Gi tr gii hn, Clim l:

i vi tt c cc trng hp khi (C > Clim th chnh lch gia U c tnh bng cc Cng thc (1) v (2) l khng ng k (< 5 %).

Khi c lng c sR th Clim c th tnh c bng Cng thc (3) hoc c ly ra t Bng B.1.

C th phn bit hai trng hp nh sau:

Nu (C > Clim th s dng Cng thc (2) tnh U;

Nu (C ( Clim th s dng Cng thc (1) tnh U.

CH THCH Khng cn tnh Clim khi Cng thc (1) c s dng trong tt c cc trng hp.

9. Biu th khng m bo o trong cc bo co th nghim

khng m bo tnh c nh trong iu 8 c th c nu r trong bo co, cng vi kt qu th nghim, theo mt khong trn thang logarit thp phn (xem Ch thch 5.3) hoc theo cc gi tr t nhin (cfu/g hoc cfu/ml), hoc theo mt t l phn trm, c minh ha theo cc cch sau.

Kt qu th nghim c th c bo co theo mt trong cc cch sau:

a) Khong cho kt qu log:

y U [log10 (cfu/g)] hocy U [log10 (cfu/ml)];

b) Kt qu loga thp phn c lng vi cc gii hn:

y [log10 (cfu/g)]

[y - U, y + U] hocy [log10 (cfu/ml)] [y - U, y + U];

c) Kt qu c lng vi cc gii hn tuyt i:

x cfu/g [10y-U,10y+U] hocx cfu/ml [10y-U,10y+U]d) Kt qu c lng vi cc gii hn tng i:

CH THCH 1 Cc gii hn tng i ph thuc ch vo U. Cc v d ca cc gii hn tng i c nu trong Bng B.1.

CH THCH 2 Trong khi x c n v l cfu/g hoc cfu/ml th y, theo logarit, khng c th nguyn ging nh pH. nhc nh ngi s dng v n v ca d liu th v loi logarit c s dng, Iog10(cfu/g) hoc log10(cfu/ml) c th c thm vo trong du ngoc n sau kt qu bng s.

V D 1:

lch chun ti lp, sR l 0,15 [log10(cfu/g)].

Kt qu th nghim l 100 000 cfu/g, ngha I y = 5.00 [log10(cfu/g)], vi (C = 110 ( pha long -3: 102 khun Ic: pha long -4: 8 khun lc).

Do khng m bo o m rng, U, vi h s ph bng 2 (mc tin cy xp x 95 %), theo Cng thc (1), bng:

Kt qu th nghim c th c bo co theo mt trong cc cch sau:

5,0 0,3 [log10(cfu/g)];

5,0 [log10(cfu/g)] [4,7; 5,3];

1,0 x 105 cfu/g [4,9 x 104; 2,0 x 105];1,0 x 105 cfu/g [-51 %; +100 %].CH THCH: Ch p dng nu dng c hai cng thc (xem 8.2.2): Clim = 78. Sau , v (C = 110 > Clim = 78 nn c th s dng Cng thc (2) gin lc i vi cc s m cao U = 2 sR = 0,30.

V D 2:

lch chun ti lp, sR l 0,25 [log10(cfu/g)].Kt qu th nghim l 280 cfu/g, ngha l y = 2,45 [log10(cfu/g)], vi (C = 31 ( pha long -1:1 ml trn 3 a: 9 + 9 + 9 khun lc; pha long -2: 4 khun lc).

Do , khng m bo o m rng, U, vi h s ph 2 (mc tin cy xp x 95 %), theo Cng thc (1), bng:

Kt qu th nghim c th c bo co theo mt trong cc cch sau:2,4 0,5 [log10(cfu/g)]

2,4 [log10(cfu/g)][1,9: 3,0];

280 cfu/g [85: 930]

280 cfu/g [-70 %; +230 %].

CH THCH: Ch p dng nu dng c hai cng thc (xem 8.2.2): Clim = 28. Sau , v (C = 31 > Clim = 28 nn c th s dng Cng thc (2) gin lc i vi cc s m cao U = 2 sR = 0,50.

V D 3:

lch chun ti lp, sR l 0,11 [log10(cfu/g)].

Kt qu th nghim l 100 cfu/g, ngha I y = 2,00[log10(cfu/g)], vi (C = 11 ( pha long -1: 9 khun lc; pha long -2: 2 khun lc).

Do khng m bo o m rng, U, vi h s ph 2 (mc tin cy xp x 95 %), theo Cng thc (1), bng:

Kt qu th nghim c th c bo co theo mt trong cc cch sau:

2,0 0,3 [log10(cfu/g)];2,0 [log10(cfu/g)] [1,7: 2,3];100 cfu/g [46; 220];

100 cfu/g [-54 %; +120 %].

CH THCH: Ch p dng nu dng c hai cng thc (xem 8.2.2): Clim = 144. Sau , v (C = 11 > Clim = 144 nn khng th s dng cng thc (2) gin i vi cc s m cao.

V D 4 (ch p dng nu dng c hai cng thc).

lch chun ti lp, sR tm c l 0,22 [log10(cfu/g)].

Clim = 36. Sau , nu (C > Clim = 36, p dng cng thc (2) gin lc cho cc s m cao, U = 2 x 0,22 = 0,44.

Nguyn tc chung, ch p dng cho cc kt qu vi (C > 36, c th c biu th theo mt trong cc cch sau:kt qu log 0,44 [log10(cfu/g)];kt qu log [log10 (cfu/g)][kt qu log - 0,44; kt qu log + 0,44];kt qu cfu/g [10kt qu log - 0,44; 10kt qu log + 0,44];kt qu cfu/g [-0,64 %; +175 %]Nu (C ( 36, hoc nu mt phng trnh c th p dng mi lc mt cch n gin, th s dng Cng thc (1).PH LC A(Tham kho)

CC KT QU CA CC TH NGHIM V THNH PHN KHNG M BO O LIN QUAN N MU CON CA PHN MU TH KIM TRA V LIN QUAN N S CHUN B DUNG DCH HUYN PH BAN UA.1. Trnh by v quy trnh th nghim

Cc th nghim do AFSSA (PHP) thay mt cho Tiu ban k thut ISO/TC 34/SC 9, t chc nm 2003 v 2004. Mc tiu l c lng nh hng ca cc nn mu sn phm khc nhau ti cc thnh phn ca khng m bo o (MU). MU lin quan n vic ly mu con t phn mu th (trong mu phn tch) v vic chun b dung dch huyn ph ban u (xem Ti liu tham kho [18]).

Quy trnh bao gm tm php c lng cho mt mu, nh c nu trong Hnh A.1.

Hnh A.1 - Quy trnh th nghimTrong Hnh A.1:

- IS (A) v IS (B) l ch vit tt ca hai dung dch huyn ph ban u c chun b c lp v cng khc nhau cng tt (v d: nhng ngi phn tch khc nhau, cn khc nhau, m dch pha long khc nhau...);

- iu kin (1) v iu kin (2) l hai nhm iu kin cng khc nhau cng tt (nhng ngi phn tch khc nhau, cc m mi trng khc nhau, cc t m khc nhau...);- cc ch s A11 A12... biu th hai ln lp li trong cc iu kin lp li (ngha l hai dy dung dch pha long cho mi huyn ph ban u, cho mi tp hp cc iu kin).

Ch rng quy trnh nu trong Hnh 2 (xem 5.2.2) c gin lc t Hnh A.1; trong Hnh 2, ch c cc s c lng c ghi A11 v B21 trong Hnh A.1 c ch ra.

A.2. Kt qu

A.2.1. Yu cu chung

Tng s 79 phng th nghim tham gia trong cc chng trnh th nghim v mi phng trong s th nghim bng mt hoc nhiu phng php, trn mt hoc nhiu nn mu, kt qu thu thp c 124 h s d liu (1 phng th nghim x 1 phng php x 1 nn mu). Trong s ny, 28 h s d liu b loi bi v phn tch khng ph hp vi yu cu t ra cho cc chng trnh th nghim.Do , cn 96 lch chun ti lp (sR), mi s xc nh mt phng th nghim, mt phng php v mt nn mu. Ngoi ra, l thuyt v cc thnh phn khc nhau cho php xc nh vai tr ca ba ngun khng m bo i vi mi lch chun ti lp l:

a) cc ngun gn vi nn mu, vic ly mu con ca phn mu th v pha long ban u;b) cc ngun gn vi cc iu kin ti lp (ngi phn tch/thi gian);

c) cc sai s ngu nhin trong cc iu kin lp li.

A.2.2. Phn loi cc nn mu

Da vo cc kt qu ca cc chng trnh th nghim ny, nn mu c chia thnh bn loi theo cc c tnh vt l:

- Loi i): dng cht lng v cc loi bt (v d: sa, sa da, sa bt...)

- Loi ii): dng rn c trn u (v d: tht xay, tht c ct nh, tht xc xch, tht xay nhuyn, cream c nh bng, kem lnh thc phm, cream u nnh...)

- Loi iii): dng rn nh (hoc rt nh) (v d: mi ty kh/nm kh, bt c rt/cn ty, salad, tm, ng cc, thc n chn nui, ht qu ph ct nh...);

- Loi iv): cc dng rn khc (v d: tht nguyn ming, phomat, bt nho...)

Tnh cht vt l ny nh hng ln n sR v lch chun ca hai trong s cc ngun khng m bo; mt ngun lin quan n nn mu (bao gm vic ly mu con ca phn mu th) v mt ngun lin quan n s chun b dung dch pha long ban u. Nhng so snh cp i cho thy s khc nhau ng k gia hai loi nn mu u tin (dng lng, dng bt v dng rn trn u) v gia hai loi cui cng (cc cht rn dng nh v cht rn dng khc).

i vi hai loi u tin, nn mu gy ra khong 0,1 log10 n v (xem ch thch trong 5.3) ca lch chun chung, khng tnh n phng th nghim v qun th vi sinh vt. i vi hai loi cui cng, khng th nh gi c th t mc tc ng ring r ca qun th vi sinh vt v phng th nghim. Ch rng hu ht cc sn phm trong hai loi cui cng c th c trn bng cch s dng b trn ri c th c coi nh loi nn mu th hai.

A.2.3. Kt qu chi tit

Cc kt qu chi tit thu c t 96 h s d liu c th s dng c nu trong cc bng t Bng A.1 n Bng A.5, cho mi qun th vi sinh vt ch.

Trong mi bng:

- vic phn loi c xc nh nh trong A.2.2;

- siS l thnh phn ca lch chun do dung dch huyn ph ban u (bao gm cc nh hng ca nn mu, vic ly mu con v vic chun b dung dch huyn ph ban u);

- sR l lch chun ti lp;

- scond l thnh phn do cc iu kin (bao gm cc nh hng ca thi gian/ngi phn tch);

- sres l lch chun thng d (gm cc nh hng ca sai s ngu nhin).

Tt c cc lch chun c biu th di dng log10 (cfu/g) hoc log10 (cfu/ml).

A.3. S dng

Trong khun kh ca tiu chun ny, kt qu ca cc th nghim, ngha l 4 loi chnh c gii thch trong A.2.2 v cc kt qu chi tit trong A.2.3 c th c coi nh hng dn cho cc phng th nghim khi chn cc nn mu th nghim c lng khng m bo o (xem 5.2.1).Bng A.1 - lch chun i vi h vi sinh vt hiu kh

M phng th nghimThc phmHngsISsRsrosscond

2Civ0,360,430,230,06

2Tht b xay ng lnhii0,070,250,240,06

3Bnh ngtiv0,120,180,110,07

4Civ0,370,510,290,20

7Thc phm n ngayiv0,240,330,170,13

8Tht b xay ng gi chn khngii0,090,150,100,06

10Salad ti ng giiii0,100,450,170,41

10Bt hnh khii0,170,240,130,11

11Pa tiv0,720,780,100,29

11Bnh ngtiv0,050,190,120,13

11Nm khiii0,140,260,150,16

12Da c giv0,190,200,060,02

13c chniv0,060,130,100,05

14Bnh ngtiv0,320,350,110,08

20Da c giv0,140,160,050,06

20Tht g ty ct bng myii0,100,130,060,05

20Tht g ct bng myii0,100,140,090,05

25Pa tiv0,460,470,070,03

26Phomat t sa tiiv0,160,260,090,19

27Dm bng ct ltiv0,300,310,060,05

30Bnh ngtiv0,090,120,060,05

31C rt noiii0,090,140,080,08

32Xc xch ln tiiv0,200,240,120,05

34Tht ln tiiv0,700,700,060,05

38Kem vaniii0,030,100,090,02

41Sa bt (mi trng)i0,050,140,100,08

42Sa bti0,020,050,040,02

43Tm ng lnhiii0,190,200,050,05

44Tm ng lnhiii0,090,180,140,08

48Sai0,040,120,060,09

49Tinh bt ngi0,090,140,060,08

55Salad ti ng giiii0,150,200,060,11

72Caseinati0,030,090,080,04

76Nci0,040,100,090,03

77Tht b xayii0,070,090,050,03

79Tht gia cm trnii0,030,130,090,07

Vi phng php ng xon:

1Phomat t sa tiiv0,290,380,120,21

24Thc n kh cho chiii0,180,240,130,09

59Tht xayii0,170,230,150,05

Bng A.2 - lch chun i vi coliform

M phng th nghimThc phmHngsISsRsrosscond

1Tht b xay ng gi chn khngiv0,320,350,110,07

3Bnh ngtiv0,160,230,150,07

6Tht b tiiv0,330,350,050,09

10Salad ti ng giiii0,410,780,330,58

12Da c giv0,150,200,120,06

20Da c giv0,070,120,090,05

26Phomat t sa tiiv0,300,330,090,10

29Tht g thi bng myii0,100,150,070,08

30Bnh ngtiv0,150,190,090,07

32Xc xch ln tiiv0,150,310,210,13

44Phomat t sa tiiv0,110,210,100,14

45Tht ln tiiv0,170,220,100,09

58Sa da ng lnhi0,120,180,110,08

74Cream nh bngii0,070,200,130,13

Bng A.3 - lch chun i vi E. coliM phng th nghimThc phmHngsISsRsrosscond

9Phomat t sa tiiv0,450,470,100,06

16Phomat t sa tiiv0,090,130,070,07

17Tht gia cm (khng c da)iv0,270,350,100,20

18Phomat t sa tiiv0,250,270,070,06

19Gan gia cmiv0,120,160,090,05

35Phomat t sa tiiv0,130,180,120,03

37Tht b xay ng lnhii0,130,170,100,05

47Cream u tngii0,130,440,150,39

50Phomat t sa tiiv0,290,300,040,02

50Phomat t sa tiiv0,240,260,08 0,05

51Phomat t sa tiiv0,130,150,070,02

52Tht xc xchii0,080,110,070,03

59Tht xayii0,150,190,080,09

S m c xc xut ln nht

78Trai (hai mnh v)iii0,150,310,150,11

Bng A.4 - lch chun i vi Staphylococci dng tnh coagulaseM phng th nghimThc phmHngsISsRsrosscond

1Phomat t sa tiiv0,260,330,160,14

16Phomat t sa tiiv0,080,160,110,09

28Phomat t sa tiiv0,150,240,170,08

46M khiii0,090,130,080,05

50Phomat t sa tiiv0,150,160,050,01

50Phomat t sa tiiv0,120,140,050,04

9Phomat t sa tiiv0,430,450,100,05

36Phomat t sa tiiv0,210,220,060,04

71Phomat t sa tiiv0,200,230,090,04

73Phomat t sa tiiv0,320,480,280,03

Bng A.5 - lch chun i vi cc h vi sinh vt khc

M phng th nghimThc phmVi sinh vtHngsISsRsrosscond

10Bt hnh khnm men + nm mcii0,080,230,090,20

11Nm khBacillus cereusiii0,210,260,120,09

15Tht gia cm (khng c da)Pseudomonasiv0,200,340,140,24

20Tht g ty thi bng myvi khun kh sulfitii0,050,100,080,03

20Tht g thi bng myvi khun kh sulfitii0,090,140,090,06

21Phomat t sa tiL. monocytogenesiv0,590,600,100,05

22Bt thc n gia scEnterobacteriaceaeiii0,310,330,110,05

33Cn ty nghinh vi khun lacticiii0,080,250,140,20

39Sa btBifidobacteriumi0,090,140,080,08

40Mi ty khBacillus cereusiii0,170,270,180,12

45Tht tiSalmonellaiv0,210,240,090,07

53Tht g ty xayvi khun kh sulfitii0,070,250,120,21

54V khnm men + nm mciv0,740,750,070,01

55Bng ngnm mciii0,320,360,110,12

56Tht g tiEnterobacteriaceaeiv0,350,520,290,27

57Tht b xayEnterobacteriaceaeii0,010,040,030,02

70Qu phnm men + nm mciii0,280,290,030,07

76NcStreptococcusi0,080,170,140,03

76NcEnterococcusi0,120,160,090,02

PH LC B(Tham kho)

CC GI TR CA Clim V CC GII HN LIN QUANKhi bit sR th gi tr Clim thu c bng cch s dng Cng thc (3). Cc gi tr ca Clim cng c a ra trong Bng B.1 vi mt s gi tr ca sR. Ngoi ra, khi bit U [bng cch s dng Cng thc (1) hoc Cng thc (2)] th cc gii hn lin quan [- (1 - 10-U) x 100%,+(-1 + 10U) x 100%] c th gip biu th cc kt qu (xem iu 9). Cc gii hn lin quan ny cng c a ra trong Bng B.1 cho mt s gi tr ca U.

Bng B.1 - Cc gl tr ca Clim v cc gii hn lin quan

lch chun ti lp khng m bo oCc gii hn lin quanb lch chun ti lp khng m bo oCc gii hn lin quanb

sRClimaUditrnsRClimaUditrn

0,01174590,02-550,5171,02-90+947

0,0243650,04-9100,5261,04-91+996

0,0319400,06-13150,5361,06-91+1048

0,0410910,08-17200,5461,08-92+1102

0,056980,10-21260,5561,10-92+1159

0,064850,12-24320,5661,12-92+1218

0,073560,14-28380,5751,14-93+1280

0,082730,16-31450,5851,16-93+1345

0,092160,18-34510,5951,18-93+1414

0,101750,20-37580,6051,20-94+1485

0,111440,22-40660,6151,22-94+1560

0,121210,24-42740,6251,24-94+1638

0,131030,26-45820,6341,26-95+1720

0,14890,28-48910,6441,28-95+1805

0,15780,30-501000,6541,30-95+1895

0,16680,32-521090,6641,32-95+1989

0,17600,34-541190,6741,34-95+2088

0,18540,36-561290,6841,36-96+2191

0,19480,38-581400,6941,38-96+2299

0,20440,40-601510,7041,40-96+2412

0,21400,42-621630,7131,42-96+2530

0,22360,44-641750,7231,44-96+2654

0,23330,46-651880,7331,46-97+2784

0,24300,48-672020,7431,48-97+2920

0,25280,50-682160,7531,50-97+3062

0,26260,52-702310,7631,52-97+3211

0,27240,54-712470,7731,54-97+3367

0,28220,56-722630,7831,56-97+3531

0,29210,58-742800,7931,58-97+3702

0,30190,60-752980,8031,60-97+3881

0,31180,62-763170,8131,62-98+4069

0,32170,64-773370,8231,64-98+4265

0,33160,66-783570,8321,66-98+4471

0,34150,68-793790,8421,68-98+4656

0,35140,70-804010,8521,70-98+4912

0,36130,72-814250,8621,72-98+5148

0,37130,74-824500,8721,74-98+5395

0,38120,76-834750,8821,76-98+5654

0,39110,78-835030,8921,78-98+5926

0,40110,80-845310,9021,80-98+6210

0,41100,82-855610,9121,82-98+6510

0,42100,84-865920,9221,84-98,6+6818

0,4390,86-866240,9321,86-98,6+7144

0,4490,88-876590,9421,88-98,7+7486

0,4590,90-876940,9521,90-98,7+7843

0,4680,92-887320,9621,92-98,8+8218

0,4780,94-897710,9721,94-98,9+8610

0,4880,96-898120,9821,96-98,9+9020

0,4970,98-908550,9921,98-99,0+9450

0,5071,00-909001,0022,00-99,0+9900

a Clim, l gii hn cho (C cao hn th c th gin lc l U = 2sR.

b Cc gii hn trn v di lin quan ca khong khng m bo o nh phn trm ca kt qu di dng cfu/g hoc cfu/ml i vi khng m bo o U (ct u tin t tri sang).

TH MC TI LIU THAM KHO[1] TCVN 6398-11 (ISO 31-11)3), i lng v n v - Phn 11: Du v k hiu ton hc dng trong khoa hc vt l v cng ngh[2] TCVN 8244-1:2010 (ISO 3534-1:2006) Thng k hc - T vng v k hiu - Phn 1: Thut ng chung v thng k v thut ng dng trong xc sut[3] TCVN 6910-2 (ISO 5725-2), chnh xc ( ng v chm) ca phng php o v kt qu o - Phn 2: Phng php c bn xc nh lp li v ti lp ca phng php o tiu chun

[4] TCVN 6910-3 (ISO 5725-3), chnh xc ( ng v chm) ca phng php o v kt qu o - Phn 3: Cc thc o trung gian chm ca phng php o tiu chun

[5] TCVN 6507-1 (ISO 6887-1), Vi sinh vt trong thc phm v thc n chn nui - Chun b mu th, huyn ph ban u v cc dung dch pha long thp phn kim tra vi sinh vt - Phn 1: Cc nguyn tc chung chun b huyn ph ban u v cc dung dch pha long thp phn[6] TCVN 4830-1 (ISO 6888-1), Vi sinh vt trong thc phm v thc n chn nui - Phng php nh lng Staphylococci c phn ng dng tnh coagulase (Staphylococcus aureus v cc loi khc) trn a thch - Phn 1: K thut s dng mi trng thch Baird-Parker[7] TCVN 4830-2 (ISO 6888-2), Vi sinh vt trong thc phm v thc n chn nui - Phng php nh lng Staphylococci c phn ng dng tnh coagulase (Staphylococcus aureus v cc loi khc) trn a thch - Phn 2: K thut s dng mi trng thch fibrinogen huyt tng th

[8] TCVN 6404 (ISO 7218), Vi sinh vt trong thc phm v thc n chn nui - Yu cu chung v hng dn kim tra vi sinh vt[9] TCVN 4992 (ISO 7932), Vi sinh vt trong thc phm v thc n chn nui - Phng php nh lng Bacillus cereus gi nh trn a thch - K thut m khun lc 30 C[10] TCVN 4991 (ISO 7937), Vi sinh vt trong thc phm v thc n chn nui - Phng php nh lng Clostridium perfringens trn a thch - K thut m khun lc[11] TCVN 7700-2 (ISO 11290-2), Vi sinh vt trong thc phm v thc n chn nui - Phng php pht hin v nh lng Listeria monocytogenes - Phn 2: Phng php nh lng[12] ISO 16140:2003, Microbiology of food animal feeding stuffs - Protocol for the validation of alternative method

[13] ISO/TS 21748, Guidance for the use of repeatability, reproducibility and trueness estimates in measurement uncertainty estimation

[14] TCVN ISO/IEC 17025, Yu cu chung v nng lc ca phng th nghim v hiu chun[15] GUM:1993, Guide to the expression of uncertainty in measurement BIPM/IEC/IFCC/ISO/IUPAC/IUPAP/OLML

[16] EURACHEM/CITAC Guide quantifying uncertainty in Analitical Mesurement, 2nd edition, QUAM: 2000, available at http://www.eurachem.ul.pt/guides/quam.htm or http://www.mesurementuncertainty.org.

[17] NIEMEIA, SI, Uncertainty of quantitative determinations derived by cultivation of microorganisms. MIKES J4, 2003; http://www.mikes.fi

[18] AH SOON, C. and CORNU, M. Report of 2003/2004 ISO Trials about uncertainty measurement, June 2004, AFSSA, Maisons-Alfort, France

1) Di 10 khun lc m c trong t nht mt a, thng tng ng vi t hn 100 cfu/g (cfu/ml) hoc 1000 cfu/g (cfu/ml) sn phm ph thuc vo th tch nui cy (1 ml hoc 0,1 ml).

2) Xem Ch thch 1, 4.4

3) TCVN 639811 (ISO 31-11) c hy b. Hin nay c TCVN 7870-2 (ISO 80000-2) i lng v n v - Phn 2: Du v k hiu ton hc dng trong khoa hc t nhin v cng ngh.

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