LI CM NEm c c kin thc v s trng thnh nh ngy hm nay l nh cng lao rt ln ca cc thy c Khoa Cng ngh Ho hc & Du kh, nht l cc thy c thuc B mn Cng ngh Thc phm, Trng i hc Bch Khoa Tp. HCM. Do vy, li u tin em xin by t lng bit n chn thnh n qu thy c nhng ngi ht lng du dt em trn con ng hc vn. c bit, em xin t s ghi n su sc n Tin s Li Mai Hng, c tn tnh hng dn, quan tm ch dy em hon thnh lun vn ny.

Tp. HCM, ngy 02 thng 01 nm 2008

Li cm nGVHD: T.S Li Mai HngNguyn Thy Nh PhngTrang 133TM TT LUN VNThc phm l yu t quan trng song hnh vi s sinh tn ca loi ngi. Theo qu trnh tin ho v pht trin ca loi ngi, thc phm cng pht trin theo. Cng vi s tin trin ca khoa hc cng ngh, cng ngh ch bin thc phm cng pht trin. Tuy nhin thc phm khng ch cung cp ngun dinh dng m cn cha nhng nguy c tm n c th nh hng khng tt n sc khe ngi tiu dng, chnh l cc loi c t d tn ti trong thc phm vi hm lng rt nh cng c th gy nh hng rt ln n c th.Nhu cu v mt thc phm p ng khng nhng v dinh dng m cn v tnh an ton v khng gy hi cho sc kho i vi ngi tiu dng l cn thit. Nu nh cc loi c t c sn trong nguyn liu hoc b nhim vo sn phm trong qu trnh ch bin th c th kim sot v phng nga, cn cc loi c t hnh thnh trong qu trnh ch bin th a dng v kh kim sot hn nhiu. Tuy nhin cc ti liu v c t xut hin trong qu trnh ch bin nc ta cn rt hn ch. V vy vic tp hp ti liu v ti ny l mt yu cu cp thit nhm tm ra k thut ch bin thc phm an ton nht v gim thiu n mc thp nht nhng nguy c tc hi n sc khe ngi tiu dng. Mc ch ca lun vn ny l tp hp tt c ti liu v c t xut hin trong qu trnh ch bin, thng nht v sp xp thnh mt h thng r rng, y . Ni dung lun vn c chia thnh 6 chng nh sau:- Chng 1: Gii thiu chung v c t- Chng 2: Tng quan ti liu v acrylamide - Chng 3: Tng quan ti liu v nhm hp cht amine vng thm (HAAs) - Chng 4: Tng quan ti liu v nhm hp cht hydrocarbon nhiu vng thm (PAHs)- Chng 5: Tng quan ti liu v nhm nitrosamine- Chng 6: Tng quan ti liu v nhm 3 MCPDTrong mi chng ca lun vn l phn tm hiu v cng thc cu to, ngun gc, tc hi, c ch sinh ra c t, cc yu t nh hng, cc phng php phn tch v bin php gim hm lng c t.Hy vng ni dung lun vn p ng c cc yu cu ra. Do thi gian thc hin lun vn qu ngn, kinh nghim v kin thc ca em vn cn hn ch, cc sai st gp phi l khng th trnh khi. Mong cc thy c gip chnh l lun vn ca em c hon thin hn. Tm tt lun vnGVHD: T.S Li Mai Hng

DANH SCH HNH VHnh 2.1: Cng thc cu to v cu trc mng tinh th ca acrylamide 3Hnh 2.2: Phn ng ca acrylamide (1) chuyn ho thnh glycidamide (2) bi cytochrome P450 6Hnh 2.3: Cc phn ng minh ha cc c ch to acrylamide (1) theo phn ng kiu Maillard (A) v oxy ho cht bo (B) 7Hnh 2.4: Qu trnh to thnh acrylamide t Asparagine vi ng kh ( hydroxy carbonyls) 8Hnh 2.5: Kt qu tm tt ca phng php nh du phn t 9Hnh 2.6: S to thnh ca acrylamide (1), 3 aminopropanamide (9), v andehyde 3 oxopropanamide (8) t asparagines vi s tham gia ca nhm carbonyl 11Hnh 2.7: nh hng ca nng asparagine v glucose ln s hnh thnh acrylamide trong khoai ty chin 1650C trong 4 pht 16Hnh 2.8: Anh hng ca thi gian v nhit du chin n hm lng acrylamide trong khoai ty chin di iu kin chin thng thng 17Hnh 2.9: nh hng ca thi gian chin v nhit ln hm lng acrylamide c trong khoai ty chin p sut chn khng (10 Torr) 17Hnh 2.10: Hm lng acrlamide cc iu kin nhit v thi gian khc nhau 18Hnh 2.11: nh hng ca phng php chin v thi gian chin n hm lng ca acrylamide trong khoai ty chin 19Hnh 2.12: Mi tng quan gia hm lng acrylamide v hm m ban u ca nguyn liu 19Hnh 2.13: Hm lng acrylamide to thnh trong qu trnh chin bp - c x l vi dung dch acid citric nng 0, 0.1, 0.2% 20Hnh 2.14: Hm lng acrylamide trong khoai ty chin sau khi ngm trong dung dch acid citric nng 0, 1, 2% 21Hnh 2.15: nh hng ca pH ln s hnh thnh acrylamide vi s c mt ca asparagine (0.5 mmol) v glucose (0.5 mmol) trong 1 mL phosphate trong sut qu trnh gia nhit 1500C trong 30 pht 21Hnh 2.16: nh hng ca cc cation ho tr 1, 2, 3 n hm lng acrylamide sau khi gia nhit vi hn hp glucose v asparagine (mi loi 10L) 1500C trong 20 pht 23Hnh 2.17: nh hng ca cc cation ho tr 1, 2, 3 n hm lng hydroxymethylfurfural sau khi gia nhit vi hn hp glucose v asparagine (mi loi 10L) 1500C trong 20 pht 24Hnh 2.18: nh hng ca cc cation ho tr 1, 2, 3 n hm lng furfural sau khi gia nhit vi hn hp glucose v asparagine (mi loi 10L) 1500C trong 20 pht. 24Hnh 2.19: S hnh thnh acrylamide trong qu trnh nhit phn hn hp glucose v asparagin 25Hnh 2.20: Qu trnh trch ly, tinh sch v tin x l mu trc qu trnh chy sc k GC MS, LC MS/MS 27Hnh 2.21: Qu trnh tinh sch in hnh dng ct c cht mang rn SPE dng trong phn tch hm lng acrylamide 28Hnh 2.22: Qu trnh pht hin acrylamide bng phng php LC/MS/MS 34Hnh 2.23: Hm lng acrylamide sinh ra sn phm khoai ty chin khi x l nguyn liu trc qu trnh ch bin bng nc v dung dch acid citric nng 0, 1, 2%. 37Hnh 2.24: Anh hng ca Lysine (A) v Glycine (B) n hm lng acrylamide sn phm chip khoai ty chin. 38Hnh 2.25: Anh hng ca cc loi acid amine khc nhau (nng 0.5%) n lng acrylamide sinh ra trong h thng th nghim vi 50 mM glucose v 50 mM asparagine x l nhit 1500C, 20 pht. 39Hnh 2.26: Biu din s nh hng ca dung dch lysine (A), glysine (B) v cystein (C) ln hm lng acrylamide c trong mu chin 1800C 40Hnh 3.1: C ch ca qu trnh to imidazo quinoline v quinoxaline 47Hnh 3.2: C ch hnh thnh ca PhIP v MeIQx 49Hnh 3.3: Cu trc ca mt s cc bin d DNA ca IQ v PhIP 50Hnh 3.4: C ch hnh thnh bin d DNA ca Norharman 51Hnh 3.5: th biu din hm lng MeIQx, PhIP v dn xut ca chng trong nc tiu sau ba n 51Hnh 3.6: Cc hp cht PhIP trong tht v nc tiu, c ch loi b c t v phn ng thun nghch ca chng trong mi trng acid 52Hnh 3.7: th biu din hm lng MeIQx v PhIP tht b bt tch c ch bin theo ba phng php khc nhau bn mc (thi gian) khc nhau 54Hnh 3.8: th biu din hm lng MeIQx v PhIP tht b hamburger c ch bin theo ba phng php khc nhau bn mc (thi gian) khc nhau 54Hnh 3.9: Hm lng MeIQx v PhIP tht heo c ch bin theo ba phng php khc nhau ba mc (thi gian) khc nhau 55Hnh 3.10: Anh hng ca hm lng nc n lng c t sinh ra trong phn ng gia hn hp 0.2 M glucose, 0.4 M glycine v 0.4 M creatinine trong dung mi diethyleneglycol nc 1200C trong 2 gi 56Hnh 3.11: Hm lng HAAs sinh ra vi cc nng glucose khc nhau 56Hnh 3.12: Anh hng ca cc loi ng kh khc nhau, glucose (A), fructose (B), lactose (C) v sucrose (D) n lng c t hnh thnh trong qu trnh ch bin tht bo 57Hnh 3.13: Hm lng HAAs sinh ra vi cc nng creatinine khc nhau 58Hnh 3.14: Hm lng HAAs sinh ra vi cc nng glycinie khc nhau 58Hnh 3.15: C ch hot ng ca cc cht chng oxy ha/cht km hm i vi cc cation t do pyrazine 60Hnh 3.16: Hm lng HAAs to thnh trong sn phm hamburger (tht b nc) ch bin 2000C, 20 pht khi c b sung cht chng km hm l ascorbate () v erythorbate (^)60Hnh 3.17: Qu trnh trch ly v tinh sch HAAs bng phng php s dng ct vi cht mang rn SPE 61Hnh 3.18: Cu trc phn t ca blue cotton 62Hnh 3.19: Hm lng creatine cn li sau cc ch x l nhit bng b l vi sng khc nhau 66Hnh 3.20: Cu trc ca mt s cc cht chng oxy ha 69Hnh 3.21: Anh hng ca cc cht chng oxy ha khc nhau n hm lng MeIQx v tng lng HAAs sinh ra trong phn ng gia creatine, glycine v glucose 70Hnh 4.1: Cu trc ba chiu ca mt phn t PAHs 73Hnh 4.2: Cu trc mng tinh th ca mt phn t PAHs 73Hnh 4.3: Cu trc phn t ca mt s cc hp cht PAHs 75Hnh 4.4: Phn loi cc hp cht PAHs theo thuyt cu trc Clar 76Hnh 4.5: Cu trc phn t ca lin kt gia DNA vi BaP v tr C8 v N7 ca guanine v N7 ca adenine 82Hnh 4.6: C ch to thnh 3,4 benzopyrene 83Hnh 4.7: S to thnh cc hp cht PAHs c nhiu vng thm t naphthalene 83Hnh 4.8: Hm lng BaP sinh ra cc loi sn phm khc nhau 85Hnh 4.9: Hm lng PAHs sinh ra phng php nng vi nhiu loi nhin liu khc nhau 86Hnh 4.10: Hm lng BaP tht b hamburger v tht b bt tch theo 3 phng php ch bin nhiu thi gian nu khc nhau 87Hnh 4.11: Cu to ca thit b trch ly gia tc ASE 300 88Hnh 5.1: Mt s cu trc phn t ca cc hp cht N-nitrosamine 99Hnh 5.2: C ch bin dng ca cc hp cht N nitroso 100Hnh 5.3: Cc phn ng to nitrosamine (M/M+ l kim loi chuyn tip nh Fe2+/ Fe3+)102Hnh 5.4: Kh nng gim lng NDMA i vi cc nng epicatechin monomer v epicatechin dimmer khc nhau 107Hnh 5.5: Cng thc cu to ca mt s hp cht hu c c cha lu hunh 109Hnh 5.6: th nh hng ca hp cht hu c c cha lu hunh n hm lng N - pyrrolidine (NPYR) 109Hnh 5.7: th nh hng ca hp cht hu c c cha lu hunh n hm lng N piperidine (NPIP) 110Hnh 5.8: th nh hng ca hp cht hu c c cha lu hunh n hm lng N morpholine (NMOR) 110Hnh 6.1: C ch to chloropropanol di iu kin thy phn bng acid 115Hnh 6.2: S hnh thnh monochloropropanol di xc tc ca enzym lipase 116Hnh 6.3: nh hng ca nng mui NaCl (16, 67% nc; 2000C) ln s hnh thnh 3-MCPD 118Hnh 6.4: nh hng ca mui n hm lng 3-MCPD trong cc loi thc phm 119Hnh 6.5: nh hng ca nc n hm lng 3-MCPD (3,47%NaCl, 2000C). 120Hnh 6.6: nh hng ca nc ln hm lng 3-MCPD trong cc thc phm khc nhau 120Hnh 6.7: nh hng ca nhit n hm lng 3-MCPD (3,47%NaCl, 2000C) 121Hnh 6.8: nh hng ca bo ln hm lng 3-MCPD trong cc thc phm khc nhau 122Hnh 6.9: Hm lng 3-MCPD (mg/kg) trong mt s nhm thc phm khc nhau 123Hnh 6.10: Anh hng ca thi gian ch bin n hm lng 3 MCPD. 123Hnh 6.11: (a) Phn ng ca 1,3-DCP v (b) 3-MCPD vi HFBA 125Hnh 6.12: Phn ng phn hy ca 3-MCDP 128Danh sch hnh vGVHD: T.S Li Mai Hng

DANH SCH BNG BIUBng 2.1: Tnh cht ca acrylamide iu kin l tng 250C, 100 kPa 3Bng 2.2: ha tan ca acrylamide (g/L) trong mt s dung mi 300C 4Bng 2.3: Hm lng acrylamide trc v sau thi gian bo qun 4Bng 2.4: Hm lng acrylamide mt s thc phm 5Bng 2.5: T l lng tiu th acrylamide bnh qun cc loi thc phm khc nhau t nm 1994 1998 5Bng 2.6: Hm lng acrylamide hnh thnh cc hn hp tc nhn khc nhau 9Bng 2.7: Hm lng acrylamide hnh thnh trong phn ng gia ng kh v cc loi acid amine khc nhau 10Bng 2.8: Acrylamide c tng hp t L aspargine vi s c mt ca nhm carbonyl di xc tc nhit (1800C, 5 pht, 20L nc) 11Bng 2.9: Cc h s ca phng trnh ng hc biu din qu trnh hnh thnh acrylamide trong khoai ty chin p sut kh quyn 12Bng 2.10: Cc h s ca phng trnh ng hc biu din qu trnh hnh thnh acrylamide trong khoai ty chin p sut chn khng (10 Torr) 13Bng 2.11: S thay i ca hm lng ng kh nhit bo qun < 80C 15Bng 2.12: Hm lng acrylamide (ng/g) khi chin vi cc loi du khc nhau 22Bng 2.13: Thnh phn cc acid bo c trong cc loi du m thng dng chin khoai ty v chn g 22Bng 2.14: Kh nng ngn cn ca cc cation ho tr 1, 2, 3 ln s to thnh base Schiff ca aspargine 23Bng 2.15: Tm tt mt s cc phng php sc k dng trong phn tch hm lng acrylamide cc loi thc phm khc nhau 29Bng 2.16: Mt s cc chng trnh chy sc k kh kt hp vi phng php khi ph (GC MS) khi phn tch hm lng acrylamide trong cc loi thc phm khc nhau 32Bng 2.17: Mt s cc chng trnh chy sc k lng cao p kt hp vi phng php khi ph (LC MS/MS) khi phn tch hm lng acrylamide trong cc loi thc phm khc nhau 35Bng 2.18: nh hng ca dung dch lysine, glysine v cystein ln hm lng acrylamide trong qu trnh ch bin bnh snack 40Bng 3.1: Tn vit tt v tn y ca mt s phn t HAAs ph bin 43Bng 3.2: Hm lng Quinolines v Quinoxalines cc loi thc phm khc nhau 46Bng 3.3: Tc nhn v iu kin th nghim ca cc phn ng to HAAs trong qu trnh x l nhit gia createine v acid amine c hoc khng c s tham gia ca ng 47Bng 3.4: Kt qu th nghim ca mt s hp cht HAAs trn chut 50Bng 3.5: Hm lng MeIQx v dn xut trong nc tiu sau ba n 51Bng 3.6: Hm lng PhIP v dn xut trong nc tiu sau ba n 52Bng 3.7: Anh hng ca cc cht chng oxy ha n hm lng cation t do pyrazine v lng c t HAAs ni chung 59Bng 3.8: Mt s cc phng php dng trong phn tch hm lng HAAs cc loi thc phm khc nhau bng phng php sc k lng cao p 63Bng 3.9: Mt s cc phng php dng trong phn tch hm lng HAAs cc loi thc phm khc nhau bng phng php sc k kh hoc phng php mao dn in t 64Bng 3.10: Hm lng HAAs sinh ra trong qu trnh ch bin tht b (chin 200 hoc 2500C) th hin qua c tnh i vi Salmonella thuc ging TA98 khi c v khng c qu trnh x l nhit s b bng thit b l vi sng 66Bng 3.11: Thnh phn ha hc v hot lc chng oxy ha trung bnh ca mt s loi mt ong 67Bng 3.12: Anh hng ca cc loi mt ong khc nhau n hm lng HAAs (ng/g) sn phm tht b 67Bng 3.13: Anh hng ca cc loi nc st khc nhau n hm lng HAAs (ng/g) sn phm tht b chin 68Bng 3.14: Anh hng ca hn hp cc loi nc st khc nhau n hm lng HAAs (ng/g) sn phm tht b chin 68Bng 3.15: Anh hng ca cc hp cht hu c cha lu hunh n hm lng HAAs (ng/g) sinh ra trong qu trnh ch bin tht b 71Bng 4.1: Cng thc cu to ca mt s hp cht PAHs 74Bng 4.2: Tm tt tnh cht ca mt s PAHs 76Bng 4.3: Hm lng 3,4 benzpyrene cc sn phm xng khi 77Bng 4.4: Hm lng BaP nhm cc sn phm tht b 78Bng 4.5: Hm lng BaP nhm cc sn phm tht g v thy sn 78Bng 4.6: Hm lng BaP nhm cc sn phm tht heo 78Bng 4.7: Hm lng BaP nhm cc sn phm t sa, cht bo 79Bng 4.8: Hm lng BaP nhm cc sn phm bnh m, snack, ng cc 79Bng 4.9: Hm lng BaP nhm cc sn phm ko v thc n trng ming 79Bng 4.10: Hm lng BaP nhm cc loi rau, qu 80Bng 4.11: Cc hp cht PAH c kh nng nh hng n cu trc gene v gy ung th 81Bng 4.12: Anh hng ca Benzo[a]pyrene khi th nghim trn ng vt nhiu con ng hp thu khc nhau 82Bng 4.13: Hm lng BaP cc loi thc phm c ch bin bng nhiu phng php khc nhau 84Bng 4.14: Hm lng PAHs (ng/g) hnh thnh cc nhit khc nhau vi cc loi du khc nhau 87Bng 4.15: Tm tt mt s phng php phn tch PAHs trong thc phm 90Bng 5.1: Mt s cc hp cht N nitroso trong thc phm 96Bng 5.2: Mt s hp cht N nitrosamine v hm lng cao nht ca chng trong mt s thc phm 98Bng 5.3: Lng tiu th hng ngy ca N nitrosodimethylamine (NDMA) v ngun thc phm chnh cc quc gia khc nhau 100Bng 5.4: Mt s tc hi ca cc hp cht Nitrosamine trn ng vt 101Bng 5.5: Mt s cc chng trnh v phng php sc k dng trong phn tch hm lng nitrosoamine trong thc phm 105Bng 5.6: pH, mn, thnh phn ha hc trung bnh ca mt mu nc st 108Bng 5.7: Hm lng N nitrosamine (g/kg) trong mu sau khi chiu x vi liu chiu x khc nhau 108Bng 5.8: Anh hng ca nc p hnh n hm lng NPYR, NPIP v NMOR 111Bng 5.9: Anh hng ca nc p ti n hm lng NPYR, NPIP v NMOR 111Bng 6.1: Hm lng 3 MCPD mt s loi thc phm 114Bng 6.2: Nng ti a 3-MCPD cho php trong mt kg nc tng ca cc nc 118Bng 6.3: Thnh phn ha hc ca cc loi thc phm khc nhau 122Bng 6.4: Cc ion ch th trong phng php quang ph EI 126Danh sch bng biuGVHD: T.S Li Mai HngBng 6.5: Tm tt mt s chng trnh chy sc k thng c s dng trong phn tch 3-MCPD nhm sn phm nc chm u nnh. 126DANH SCH CC T VIT TTHAAs (heterocyclic aromatic amines): cc hp cht amine c vng thm.PAHs (Polycyclic aromatic hydrocarbons): nhng hp cht hydrocarbon cha nhiu vng thm.HPLC (high pressured liquid chromatography): sc k lng cao pGC (gas chromatography): sc k kh3-MCPD: 3-monochloropropane-1,2 diolLOD (limit of detection): gii hn pht hinLOQ (limit of quantification): gii hn phn tch WR (working range of concentrations): khong nng phn tchIS (internal standard): cht ni chun.SPE (solid-phase extraction): Tinh sch bng ct vi cht mang rnLC (liquid chromatography): phng php sc k lngMS (mass spectrometry): phng php khi phDanh sch cc t vit ttGVHD: T.S Li Mai Hng

CHNG 1: GII THIU CHUNG1.1. Gii thiu chung v c t:1.1.1. Khi nim c t: c t hay cht c ho hc trong thc phm l cc hp cht ha hc c trong nguyn liu, sn phm thc phm mt nng nht nh gy ng c cho ngi hay ng vt s dng chng.

1.1.2. Phn loi con ng c t xm nhp vo thc phm: c t tn ti nhiu trng thi khc nhau, c hnh thnh v ln vo thc phm bng nhiu con ng khc nhau. Cc c t c a vo thc phm bng nhng con ng c bn sau: c t to thnh trong thc phm do vi sinh vt nhim vo thc phm gm vi khun, vi nm Trong qu trnh nhim v pht trin trong thc phm, vi sinh vt c kh nng chuyn ho cc cht dinh dng c trong thc phm v to ra c t. c t c sn trong ngun nguyn liu thc phm nh cc loi thc vt v ng vt c cha cht c, chng khng b bin i hoc b bin i rt t trong qu trnh ch bin v bo qun thc phm. c t do thc phm b nhim ha cht: Do vic s dng ba bi, khng tun th nhng qui nh v s dng cc cht ph gia thc phm. Do s dng bao b c cht lng km hoc khng ph hp vi loi thc phm. Do nhim kim loi nng: ch, asen, km, thic Do d lng thuc bo v thc vt: thuc tr su, phn bn, thuc dit c, dit cn trng c t do thc phm b bin cht, i, hng: S bin cht ca cc acid amine to thnh cc cht gy c cho c th nh: Tryptophane -> Tryptamine, Histidine -> Histamine v cc acid hu c, amoniac, indol, scatol, phenol ...thng gp cc thc phm giu protein nh tht c v cc sn phm ca tht c ch bin (tht kho, tht xo, tht luc, tht bm, ch, pate, lp xng, xc xch, hay ch c, c kho ...). S thy phn v oxy ha cht bo hnh thnh nn cc sn phm glycerin, acid bo t do, cc peroxyt, hydroperoxyt, aldehyd v cetone ... gy nn mi i kht v v ng cho sn phm, thng gp cc lai thc phm ch bin vi du m nh cc mn xo, rn nh tht quay, c rn ... Thng thng cc thc phm b bin cht thng gim gi tr dinh dng v c s thay i v tnh cht cm quan nh mi v khng ngon, thay i mu sc ...nhng d nhn bit c v c th kim sot c. c t hnh thnh nn trong qu trnh ch bin thc phm do s tng tc gia cc tnh phn c sn trong nguyn liu vi nhau v vi cc iu kin ca qu trnh ch bin. y l nhm c t rt a dng v kh kim sot [2].Trong khun kh lun vn ny em ch tm hiu tng quan v cc nhm c t xut hin trong qu trnh ch bin thc phm m c kh nng gy c lu di i vi c th con ngi v c hnh thnh do cc phn ng c trng trong qu trnh ch bin nh cc nhm: acrylamide, HAAs, PAHs, 3-MCPD v N nitrosamine.

1.2. Gii thiu v c t xut hin trong qu trnh ch bin: c t xut hin trong qu trnh ch bin chnh l cc hp cht ha hc c to ra trong qu trnh ch bin t nguyn liu ra n sn phm. Rt kh c th d on ht cc loi hp cht c to ra trong qu trnh ch bin thc phm v c th gy hi n sc khe ngi tiu dng. Nhng cng khng th ph nhn rng cc c t xut hin trong qu trnh ch bin thc phm khng tn ti. c mt s cc nhm c t xut hin trong qu trnh ch bin thc phm c pht hin cho n nay gm: Acrylamide: Acrylamide c pht hin ln u tin vo nm 2002, c tm thy nhiu cc sn phm khoai ty chin, nng v cc sn phm ng cc khc. Acrylamide c kh nng gay ung th, gy tn hi h thn kinh v cc nguyn liu di truyn khi th nghim trn ng vt. Tuy nhin vn cha c bng chng r rng t cc th nghim dch t hc rng acrylamide c th gy ra nhng tc ng ny i vi con ngi. Cc hp cht amine c vng thm (HAAs): Cc hp cht HAAs thng c tm thy cc sn phm nng, chin giu protein nh cc cc loi sn phm tht, c v c cc loi nc p tht ... Hu ht cc phn t HAAs sinh ra trong qu trnh ch bin u cho thy l c kh nng gy ung th trn ng vt. Cc hp cht hydrocarbon c nhiu vng thm (PAHs): PAHs thng tn ti nhiu trong mi trng nh l sn phm ca qu trnh t chy khng hon ton nhin liu v cng c to thnh trong qu trnh ch bin thc phm c lin quan n x l nhit v xng khi thc phm (c bit l cc sn phm tht). Cc hp cht ny c kh nng gy ung th cho ngi v ng vt. Trong cht c c t mnh nht v ph bin nht trong thc phm l benzo[a]pyrene [BaP]. Ngoi ra cc PAHs cn tn ti nhiu trong cc sn phm du tinh luyn v cc dn xut ca du m nh b (hm lng BaP khong 0.06 g/kg) do b nhim bn trong qu trnh sy kh ht du bng khi l. Cc hp cht N nitrosamine: N nitrosamine c hnh thnh cc sn phm thc phm m thnh phn nguyn liu c cha nitrite/nitrate (c bit l sn phm tht, c c s dng cht bo qun l cc mui nitrite/nitrate). y l nhng hp cht c cho l gy ung th trong khong rng khi th nghim trn ng vt, trong c c tnh mnh nht chnh l hp cht N-nitrosodimethylamine (NDMA). Hp cht 3-MCPD (3-monochloro-propane-1,2-diol): y l hp cht c tm thy ph bin cc sn phm thy phn bng acid ca protein thc vt c bit l cc sn phm nc chm u nnh. 3-MCPD thuc nhm chloropropanol l mt cht c khng gy hi n nguyn liu di truyn nhng li c kh nng gy ung th trn ng vt. Ngoi ra 3-MCPD cn c tm thy trong mt s loi nc gii kht b nhim trong qu trnh x l nc.Chng 1 : Gii thiu chungGVHD: T.S Li Mai Hng

CHNG 2: ACRYLAMIDE2.1. Cng thc cu to, tnh cht:2.1.1. Cng thc cu to: Acrylamide thuc nhm amide c cng thc phn t l C3H5NO, C=CC(=O)N v c tn theo IUPAC l 2-propenamide [125]. Cng thc cu to [108] v cu trc mng tinh th ca acrylamide th hin theo trc a vi cc lin kt hydro c th hin bng nt m [86]:

Hnh 2.1: Cng thc cu to v cu trc mng tinh th ca acrylamide Ngoi ra acrylamide cn c mt s tn gi khc ng ngha nh [122]: Acrylic acid amide; Acrylic amide; Acrylamide monomer; Akrylamid; Ethylene carboxamide; Propenamide; Propeneamide; Propenoic acid amide.

2.1.2. Tnh cht: Bng 2.1: Tnh cht ca acrylamide iu kin l tng 250C, 100 kPa [125]Tn tnh chtThng s

Khi lng phn t71.08 g/mol

Trng lng ring1.13 g/cm

Nhit nng chy84.50C

p sut bay hi0.009 kPa

Khi lng ring1.222 g/cm3

Nng lng cn cho qu trnh polymer ha19.8 kcal/mol

ha tan trong nc204 g/100 ml (250C)

im chp sng1380C

im t bc chy4240C

Bng 2.2: ha tan (g/L) trong mt s dung mi 300C [102] Tn dung mi ha tan (g/L)

Acetone631

Benzene3.46

Chloroform26.6

Ethanol862

Ethyl acetate126

n-heptane0.068

Methanol1550

Nc2155

Acrylamide tn ti dng tinh th mu trng, khng mu, khng mi c nhit si rt cao v rt ho nc, c s dng nhiu ngnh cng nghip khc nhau. ng dng ph bin nht ca acrylamide l c dng tinh sch nc ung v x l rc thi sinh hot (acrylamide s lin kt vi cc tp cht rn trong nc v lm tng hiu sut ca qu trnh lc). Acrylamide cng c s dng trong ngnh nhum, m phm v bao b, ngnh nha do v cng nghip xy dng ... [125]. Phn t acrylamide tn ti trong thc phm vi bn rt cao hu nh khng i sau thi gian di bo qun.

Bng 2.3: Hm lng acrylamide trc v sau thi gian bo qun [49]Tn thc phmThi gian bo qun (thng)Hm lng acrylamide (g/kg)

TrcSau

Ng cc n sng12238238

Ng cc rang9265225

C ph rang7203147

Rau c sng5214174

Rau c rang540153395

Ca cao3180177

Chocolate nhn hnh o29473

Bt chocolate ha tan15741

2.2. Ngun gc: Acrylamide ln u tin c c th gii bit n thng qua bo co ca mt nh khoa hc Thy in vo thng 4 nm 2002, thu ht c s quan tm c bit do n c pht hin c mt lng ln cc thc phm chin, rn hoc nng l [8]. Acrylamide thng c tm thy vi hm lng ln cc thc phm giu tinh bt nh: khoai ty chin, bnh m chin gin... v cng c tm thy cc loi thc phm khc nh: cc loi tht rn heo, g, b... cc loi nc st, hamburger nhng vi mt lng nh. Do ngi ta cho rng cc loi thc phm giu tinh bt chnh l ngun to ra acrylamide ch khng phi l nhm thc phm giu protein. Ngoi ra acrylamide cng c tm thy nhiu mt s loi ng cc v c ph rang do ngi ta cng cho rng s tn ti ca acrylamide c mi lin h vi phn ng Maillard xy ra cc loi thc phm ny [36]. Acrylamide cng c tm thy hn 86 sn phm ca ht hnh nhn nh hnh nhn rang, nng, trong bnh m ...Acrylamide nhng thc phm chin hay nng c to ra do phn ng gia asparagine v cc ng kh (fructose, glucose ). Mt s nghin cu khc cho thy cc phn ng t nhin trong mi trng nh phn ng phn hy ca cc loi thuc dit c cng l ngun to ra acrylamide [108]. Acrylamide cn c to ra trong sut qu trnh ch bin thc phm bng l vi sng nhng khng c tm thy nhng thc phm nu bng hi nc hay cha qua nu nng. S rn vng trong sut qu trnh chin, nng hoc chin su u to ra acrylamide v thi gian nu thc phm di s to ra lng ln acrylamide [125].

Bng 2.4: Hm lng acrylamide mt s thc phm [24]Loi thc phmHm lng acrylamide (ppb)

Bnh m 12 3200

Bnh cracker v biscuit30 2000

Ng cc 30 2300

Cc loi lng thc khc < 30

Chip khoai ty150 1280

Cc loi snack mn khc 122 416

Khoai ty chin85 1104

Cc loi rau, qu khc10 50

Ko v thc phm trng ming20 110

Tr v c ph170 700

Thc ung c cn30

Thc ung khng cn khc < 30

Cc sn phm t sa 10 100

Cc loi gia v v nc st38 54

Bng 2.5: T l lng tiu th acrylamide bnh qun cc loi thc phm khc nhau t nm 1994 1998 [27]Thc phmLng dn s s dng (%)Lng thc phm tiu th (g/kg/ngy)Nng acrylamide (g/kg thc phm )Lng acrylamide ngi s dng tiu th (g/kg/ngy)Lng acrylamide tiu th trung bnh (g/kg/ngy)

Ng cc n sng77.40.84133.30.110.09

Chip khoai ty75.80.17548.00.090.07

Thc phm rang, r ti27.01.14207.80.240.06

Khoai ty chin48.90.35321.80.110.06

Snack khoai ty20.60.35663.80.230.05

Bnh bisque66.50.27221.60.060.04

Bnh m73.01.1444.40.050.04

C ph57.54.808.50.040.02

2.3. Tc hi: Khi tin hnh th nghim cho ng vt tiu th acrylamide liu lng ln, trong thi gian di th acrylamide c th gy hi n h thn kinh, lm gim kh nng sinh sn, tn hi cc nguyn liu di truyn v tng nguy c gy ung th cc b phn nh: tuyn gip, ming, ung th v ph n v tinh hon nam gii ... [125]. Bi v acrylamide gy ung th ng vt vi liu lng ln nn n c t chc IARC (International Agency for Research on Cancer) xp vo nhm cht c kh nng gy ung th tim n ngi [64]. Theo c tnh ca t chc WHO nguy c ung th i vi ngi tiu th 1.0g acrylamide/kg th trng/ngy l 1/1000, theo i hc Stockholm l 10/1000. V trong na gram chip khoai ty hoc trong hai gram khoai ty chin c th cha 1.0 g acrylamide, do nhng ngi thng xuyn n nhng thc phm ny c th tiu th n 35 40 g acrylamide/ngy [54]. C ch loi b acrylamide ca h thn kinh ca con ngi v ng vt din ra theo s sau [49]:

Hnh 2.2: Phn ng chuyn ho ca acrylamide (1) thnh glycidamide (2) bi cytochrome P450 v thioether (3), (4a), (4b)

u tin khi vo c th ngi acrylamide s b chuyn ha thnh epoxide glycidamine (2) nh enzyme P450 cytochrome monooxygenase CYP 2E1, sau epoxide glycidamine (2) s kt hp vi glutathione (R SH) to thnh cc thioether tan trong nc (4a), (4b) thng qua phn ng Michael. T acrylamide cng trc tip to thnh thioether (3) khi kt hp vi glutathione qua phn ng Michael [49]. Acrylamide v cc sn phm trao i cht ca n c bit l glycidamine c th gy c v gy ung th khi th nghim trong phng th nghim v trn c th sng liu lng ln. Khi nghin cu trn t bo acrylamide v glycidamine c nh hng ln n qu trnh phn chia cc nhim sc th v t l t bin c th l lm bin i cc base Nit A thnh G, G thnh C v G thnh T. Ngoi ra acrylamide v glycidamine cn c th lin kt vi cc protein v chui ADN lm thay i thng tin di truyn v lin kt vi phn t hemoglobin, lm gim kh nng vn chuyn oxy n t bo. V gia acrylamide v glycidamine th glycidamine c hot tnh cao gp 100 1000 ln so vi acrylamide [49]. Theo khuyn co ca t chc FAO v WHO lng acrylamide trung bnh mi ngy (ADI average daily food intake) cho dn tc trn ton th gii l t 0.3 0.8 g/kg th trng/ngy. Theo nhiu nghin cu chut th mc tiu th acrylamide m khng gy nn bt k tn thng no (NOEAL no observed adverse effect) l 0.2g/kg th trng/ngy [27]. Tuy nhin cho n nay vn cha c mt bng chng no r rng v tc ng ca acrylamide c th gy ung th ngi hoc c th tc ng xu n h thn kinh khi tiu th acrylamide liu lng thp hn liu lng nghin cu [64]. V ch c acrylamide tn ti dng monomer mi gy c n con ngi cn cc cc polymer ca acrylamide c xem l khng gy c [122].

2.4. C ch hnh thnh acrylamide:2.4.1. C ch : Cho n nay c nhiu gi thuyt c t ra gii thch c ch to thnh acrylamide cc loi thc phm khc nhau, c chia lm 3 nhm ln nh:1. S phn hy nhit ca mt s cc acid amine t do nht nh nh: asparagine, methionine...2. Phn ng gia mt s acid amine t do nht nh nh: asparagine, methionine, cysteine, glutamine... vi cc loi ng kh thng qua con ng phn ng Maillard. Gm cc phn ng sau: S ng vng ni phn t ca cc base Schiff to thnh oxazolidin-5-one v CO2, s gii phng cc hp cht beta-elimination cc hp cht Amadori b decarboxyl ha to hoc s to sn phm deamine ca 3- aminopropionamide to thnh acrylamide. Methionine (hoc cc acid amine khc) tr nn linh ng sau qu trnh decarboxyl ha v deamine ha to thnh methional, c kh nng phn ng nh aldehyde vi asparagine to thnh acrylamide.3. S oxy ha cht bo khi c mt cc sn phm phn hy nhit ca cc acid amine t do (NH3). Gm cc phn ng sau: Acrolein (t triolein) + NH3/Asparagine Acrylamide hay Acrylic acid + NH3 Acrylamide (NH3 t phn ng phn hy nhit ca cc acid amine) phn ng ny ch c hiu sut bng 5% so vi hiu sutca Asparagine [80]. Cc phn ng minh ha cc c ch phn ng trn c cho hnh sau [49]:(B) Phn ng oxy ha cht bo(A) Phn ng Maillardng khP. MaillardP. Strecker

Hnh 2.3: Cc phn ng minh ha cc c ch to acrylamide (1) theo phn ng Maillard (A) v oxy ho cht bo (B) vi asparagine (5), base Schiff (7), 3-oxopropanamide (8), 3-aminopropionamide (9), cht bo (12), acrolein (11) v acid acrylic (10). S chuyn ho (5) -> (8), (7) -> (1) v (12) -> (11) l kt qu ca nhiu phn ng trung gian. Theo nhiu nghin cu th trong cc c ch trn, c ch to acrylamide gia Asparagine vi ng kh thng qua phn ng Maillard (A) l con ng chnh to acrylamide [49]: C ch ny gm mt chui cc phn ng khc nhau c minh ha hnh bn di [8]:

Hnh 2.4: Qu trnh to thnh acrylamide t Asparagine vi ng kh ( hydroxy carbonyls, R l gc hydrocarbon). I - S to thnh hp cht Amadori, II Qu trnh decarboxyl ha, III Qu trnh tautomerize ha, IV Qu trnh deamine ha.

Bc quan trng nht trong chui phn ng to acrylamide l s to thnh cc base Schiff v cc hp cht N- glycosyl. Khi c mt nc th base Schiff s b thy phn to thnh cc tc nhn ca phn ng to acrylamide (con ng II) hoc tham gia phn ng ng phn ha to thnh hp cht Amadori (con ng I), y l hp cht trung gian ca chui cc phn ng Maillard dn n s to thnh 1- v 3 deoxyosones, cui cng l phn ng phn hy cc hp cht ny to ra mu sc v hng v c trng cho sn phm. Do m hiu sut ca phn ng to acrylamide t Asparagine vi ng kh l rt thp, thng thng l di 1% mol. Thng qua con ng II t base Schiff qua mt trong ba phn ng s to thnh hp cht azomethine ylide, y l hp cht rt quan trng to ra acrylamide thng qua nhiu cch: trc tip t hp cht azomethine ylide, gin tip t hp cht emulation (hp cht trung gian ca phn ng Maillard) hoc sn phm deamine ca 3- aminopropionamide (c to thnh t hp cht azomethine ylide) [8]. Theo nghin cu th c asparagine v ng kh u c vai tr c bit quan trng trong phn ng to acrylamide, c chng minh qua th nghim sau:Trong cng mt iu kin ch bin, hn hp ch gm tinh bt khoai ty v nc, hay tinh bt khoai ty, nc v ng kh to ra lng acrylamide khng ng k ( 58.WR: 0.01100 mg/L.[126]

Thc phm t ng cc v khoai tyd3-acrylamide.Ct ct sc k lng cao p pha o Thermo Electron, 2.1x 50 mm (Bellafonte, PA, USA) Pha ng: nc v khun 100%, lu lng 0.4 ml/pht.Hiu in th ngun to ion: 6 kV, nhit ha hi mu: 2500C; AA: 7255, I.S: 7558, nng lng va chm 13eV.LOD: 0.25 ng/mL hay 2.5 pg, h s tng quan l r2 = 0.999 [99]

1. Tm li th phng php phn tch bng sc k lng cao p (vi ct sc k pha o) kt hp vi khi ph c nhy tng ng (LOD: 0.2 45 ppb) nhng thi gian phn tch ngn hn (do khng cn qu trnh to dn xut mu) so vi phng php phn tch bng sc k kh kt hp vi khi ph (LOD: 0.2 25 ppb) nn c s dng rng ri phn tch nhanh hm lng acrylamide trong thc phm.

1. Bin php gim hm lng acrylamide trong thc phm: 2. gim lng acrylamide trong sn phm thc phm ta c th dng cc bin php sau: loi b hoc gim cc tc nhn ca phn ng gm asparagine v ng kh, dng cc cht c ch phn ng, gim nhit v thi gian ca qu trnh ch bin, loi b acrylamide ra khi sn phm sau qu trnh ch bin [104].

1. Loi b hoc gim cc tc nhn ca phn ng bng cch ngm nguyn liu vo cc dung mi khc nhau:

0. Nc:1. Nc c xem l dung mi c tc dng nh nht trong vic gim lng acrylamide, c th gim 24.9% lng acrylamide sn phm khoai ty chin khi ngm nguyn liu trong 1 gi trc khi chin nhit 1900C trong 6 pht 30 giy. Nc ngoi tc dng lm gim lng cc tc nhn ca phn ng cn lm tng hm m ca nguyn liu trc qu trnh ch bin [76].Acrylamide (g/kg Khoai ty chin)Dung dch ngm

O Nc

Hnh 2.23: Hm lng acrylamide sn phm khoai ty chin khi x l nguyn liu bng nc v dung dch acid citric nng 1, 2% v khng x l (0).

0. Dung dch acid nh acid citric v acetic: 1. Khi ngm nguyn liu ca sn phm chip t bp ng nng (2550C, 100 giy) bng dung dch acid citric nng 0.1% v 0.2% trong vng 1 gi trc qu trnh nng c th gim 58.2 v 72.8% hm lng acrylamide to thnh. Khi s dng dung dch acid acetic c th gim n 90% lng acrylamide khi ngm trong vng 1gi. 1. Tc dng ca dung dch acid ngoi vic lm gim lng cc tc nhn ca phn ng cn c tc dng gim pH ca dung dch (gim 1.2 v 1.5 n v pH) t chuyn trung tm ht nhn khuyt in t t do ca nhm amine trong phn t Asparagine (_NH2) thnh nhm amine mang in tch dng (_NH3+) thay v to thnh base Schiff thng qua vic chuyn ht nhn ca nhm - amine sang v tr ni i carbonyl (C=C) ca phn t ng kh to thnh phn t acrylamide do lm ngng phn ng to acrylamide trong thc phm. Tuy nhin vic s dng dung dch acid rt hn ch (thng khng dng qu 1%) v c th gy ra v chua khng mong mun cho sn phm [76].

0. Dung dch kim NaOH: 1. Khi ngm nguyn liu khoai ty ming vo dung dch kim NaOH 1% trong 1 gi c th gim n 74% lng acrylamide sinh ra sn phm khoai ty chin. Tuy nhin phng php ny thng khng c s dng v gy ra mi, v khng mong mun v gim tnh cht cm quan ca sn phm [104].

0. Dung dch acid amine t do:1. Ngoi ra ta cng c th gim hm lng acrylamide sinh ra bng cch ngm nguyn liu trong dung dch ca L- glycine (B) v L- Lysine (A). Tc dng ngn cn s to thnh acrylamide sn phm l do gim i cc c cht cho phn ng to acrylamide trong qu trnh ch bin. Anh hng ca vic ngm cc ming khoai ty trc khi chin n lng acrylamide trong sn phm c cho hnh v sau [104]:Acrylamide (ug/kg)Nng (%,w/w)1 Pht3 Pht5 Pht 0

Nng (%,w/w)1 Pht3 Pht5 Pht 0Acrylamide (ug/kg)

Hnh 2.24: Anh hng ca Lysine (A) v Glycine (B) n hm lng acrylamide sn phm chip khoai ty chin.1. T th trn ta thy rng ngm cc ming khoai ty trong dung dch L- Lysine nng 0.1% trc khi chin trong 1, 3, 5 pht c th gim 45, 72, 79% lng acrylamide trong sn phm. Khi ngm trong dung dch L- Lysine nng 3% lng acrylamide gim nhiu nht l 84 v 92%. i vi dung dch L- glycine th lng acrylamide gim cao hn ngm 5 pht nng 0.1 v 3% c th gim 79 n 94% lng acrylamide trong sn phm. 1. Khi tin hnh th nghim trn sn phm snack chin v chip khoai ty cng cho kt qu tng t. Do vy y cng l mt phng php rt hu hiu gim lng acrylamide, phng php ny c u im hn so vi phng php ngm trong dung mi khc l tit kim thi gian rt ln v khng gy nh hng n mi v v cht lng ca sn phm [104].

1. Dng cc cht c ch phn ng to acrylamide: 1. Ta c th thm mt trong cc ph gia thc phm gm cc acid amine, acid citric, cht chng oxy ha, cc cht to nh hoc b sung thm enzyme asparaginase mt enzyme t nhin vo hn hp bt bnh m, khoai ty v sn phm c cha ca cao gim lng acrylamide sinh ra trong qu trnh ch bin. La chn ph gia no l ty vo tnh cht ca nguyn liu v yu cu ca sn phm [86].1. Tng hm lng acid amine:Nhiu nghin cu cho thy asparagine ng vai tr rt quan trng trong phn ng to acrylamide khi c mt ng kh cc sn phm t khoai ty, go v ng cc. Khi thay th asparagine bng cc acid amine khc th ch to ra mt lng rt nh acrylamide (lng vt) nhng khi tn ti ng thi c asparagine v ng kh th hm lng mt s acid amine t do li c nh hng ln n hm lng acrylamide trong thc phm. iu ny c chng minh qua th nghim sau [104]: 1. Phng php th nghim: thm cng mt lng (0.5%) cc acid amine t do sau: L- Lysine, L- glycine, L- acid glutamide v L- cysteine vo hn hp cha 50 mM glucose v 50 mM asparagine x l nhit 1500C, 20 pht th thu c kt qu nh sau: 0

Hnh 2.25: Anh hng ca cc loi acid amine khc nhau (nng 0.5%) n lng acrylamide sinh ra trong th nghim vi 50 mM glucose v 50 mM asparagine x l nhit 1500C, 20 pht.

1. Kt qu: L- glycine, L- Lysine v L- cysteine c th gim lng acrylamide sinh ra tng ng l 95%, 91% v 87% trong khi L- acid glutamide ch c th gim 20%. Nguyn nhn c th dn n s khc bit ny l do tnh tan ca L- acid glutamide th thp hn so vi L- glycine, L- Lysine v L- cysteine.1. Khi nghin cu trn thc phm c th l sn phm chip khoai ty chin lng acrylamide sinh ra khi thm mt s cc acid amine t do c minh ha bng hnh v sau: Acrylamide (ug/kg)Thi gian phn ng (pht)

Acrylamide (ug/kg)Thi gian phn ng (pht)

Acrylamide (ug/kg)Thi gian phn ng (pht)

Hnh 2.26: nh hng ca dung dch lysine (A), glysine (B) v cystein (C) n hm lng acrylamide c trong mu chip khoai ty chin 1800C

1. T th trn ta thy rng nh hng ca cc acid amine ln hm lng acrylamide ph thuc vo nng ca cc acid amine ny v thi gian qu trnh ch bin. C th i vi lysine (A) 0.5 pht u qu trnh chin th lng acrylamide gim n 70% cc nng lysine t 0.1 3%. Khi thi gian chin cng tng th lng acrylamide gim cng t hn so vi giai on u qu trnh nguyn nhn l do nhit cao th thi gian cng tng th cc acid amine b phn hy bi nhit cng tng. Khi tng thi gian chin ln 3 pht th lng acrylamide ch gim 3% khi s dng 0.1% lysine. Kt qu thu c tng t i vi trng hp ca L- Lysine (B) v L - cysteine (C) trong L- cysteine (C) c tc dng nh nht so vi L- glycine v L- Lysine do n c ha tan trong nc l thp nht [104].1. cc loi thc phm dng snack cng nghip c chin 1800C, 25 pht th nh hng ca acid amine L- glycine, L- Lysine v L- cysteine c cho bng sau:

Bng 2.18: nh hng ca dung dch lysine, glysine v cystein ln hm lng acrylamide trong qu trnh ch bin bnh snackDung dch x lAcrylamide (g/kg)Hm lng acrylamide gim (%)

Mu ban u1154 79

Lysine 0.1%657 443 4

0.5%353 1069 2

Glysine 0.1%795 1431 4

0.5%543 953 3

Cystein 0.1%935 619 5

0.5%1008 3913 8

1. T bng trn ta thy khi dng L- glycine, L- Lysine nng 0.5% th c th gim lng acrylamide nhiu nht 69 v 53%. iu ny c th gii thch l do cc acid amine ny cnh tranh vi cc tc nhn to acrylamide v gim s to thnh acrylamide trong qu trnh ch bin (ngn cn hot ng ca cc nhm ha tr to acrylamide). 1. Do vy y l mt phng php rt hu hiu gim hm lng acrylamide trong thc phm ch bin cng nghip c bit l sn phm snack, n c u im hn phng php b sung acid citric l khng gy nh hng n mi v v cht lng ca sn phm. [104]

1. Gim nhit v thi gian ca qu trnh ch bin : 1. H thp nhit trong qu trnh nng, s dng phng php chin chn khng h thp nhit chin, trnh dng cc hp cht ca silicone ph bt trong qu trnh chin su v c th lm lng acrylamide tng gp i [24].

1. Loi b acrylamide ra khi sn phm sau qu trnh ch bin: 1. Hin nay cc nh nghin cu ang tm phng php loi acrylamide ra khi sn phm sau qu trnh ch bin: Ngi ta th nhiu phng php nh l: s dng phng php trch ly siu ti hn vi dung mi l CO2 lng v phng php chiu tia t ngoi nhng vn cha thu c kt qu mong mun. Phng php trch ly siu ti hn vi dung mi l CO2 lng c th loi b mi c t nhng li ph hy thc phm, phng php chiu tia t ngoi khng c kh nng loi acrylamide ra khi thc phm nhiu bc sng k c bc sng kh kin [91].1. Ngoi ra ngi ta c th gim hm lng acrylamide sinh ra trong qu trnh ch bin bng cch tc ng ln cc yu t khch quan ca nguyn liu th nh: 0. Ch bo qun: i vi khoai ty th nhit bo qun khng nn h xung thp hn 80C. Khi nhit xung thp khong 40C th lng fructose tng nhanh do l tng lng acrylamide sinh ra trong qu trnh ch bin (nng hoc chin).0. Chn la nguyn liu th: S dng nhng ging khoai ty mi m sinh ra lng acrylamide thp [125]

2. Kt lun: Acrylamide l mt tp cht ha hc xut hin ch yu trong qu trnh ch bin cc thc phm chin nng ... thng qua con ng phn ng Maillard vi hai tc nhn chnh l asparagine v ngun carbonyl (ng kh). Tc hi: Acrylamide c kh nng gy ung th, gy tn hi h thn kinh v cc nguyn liu di truyn khi th nghim trn ng vt. Cc yu t nh hng n hm lng acrylamide sinh ra trong qu trnh ch bin gm: nhng yu t khng thuc bn cht bn trong nguyn liu (qu trnh x l nng nghip, loi t trng, iu kin chm sc, bo qun..), nhng yu t thuc bn cht bn trong nguyn liu (thnh phn ha hc ca nguyn liu c bit l hm lng acid amine (asparagine) v ng kh) v cc thng s cng ngh ca qu trnh ch bin: nhit , thi gian, m, p sut, pH ... phn tch hm lng acrylamide trong thc phm ch yu dng hai phng php l phng php sc k lng cao p (vi ct sc k pha o) kt hp vi khi ph hoc phng php sc k kh kt hp vi khi ph vi nhy c th t l 0.2 ppb. Mt s phng php c dng gim hm lng acrylamide trong qu trnh ch bin: loi b hoc gim cc tc nhn ca phn ng gm asparagine v ng kh (bng cc dung mi khc nhau nh nc, acid, kim, dung dch acid amine ...), dng cc cht c ch phn ng (acid amine, acid citric, cht chng oxy ha, cht to nh hoc enzyme asparaginase...) hoc gim nhit v thi gian ca qu trnh ch bin (ch bin trong iu kin p sut chn khng).

CHNG 3: HAAs1. Cng thc cu to, tnh cht:1. Cng thc cu to: 1. HAAs (heterocyclic aromatic amines): l cc hp cht amine vng thm (nhm amine gn trn vng thm), c to thnh trong qu trnh ch bin cc thc phm giu protein. Tn gi v vit tt ca mt s phn t HAAs c cho bng sau:

Bng s 3.1: Tn vit tt v tn y ca mt s phn t HAAs ph bin [74] Quinolines

IQ 2-amino-3-methylimdazo[4,5-f] quinoline

MeIQ 2-amino-3,4-dimethylimdazo[4,5-f] quinoline

Quinoxalines

IQx 2-amino-3-methylimdazo[4,5-f] quinoxaline

MeIQx 2-amino-3,8-dimethylimdazo[4,5-f] quinoxaline

4,8-DiMeIQx 2-amino-3,4,8-trimethylimdazo[4,5-f] quinoxaline

7,8-DiMeIQx 2-amino-3,7,8-trimethylimdazo[4,5-f] quinoxaline

TriMeIQx 2-amino-3,4,7,8-tetramethylimdazo[4,5-f] quinoxaline

4-CH2OH-8-MeIQx2-amino-4-hydroxymethyl-3,8-dimethylimidazo[4,5-f] quinoxaline

7,9-DiMeIgQx 2-amino-1,7,9-trimethylimidazo[4,5-g] quinoxaline

Pyridines

PhIP 2-amino-1-methyl-6-phenylimidazo[4,5-b] pyridine

4-OH-PhIP 2-amino-1-methyl-6-[4-hydroxyphenyl)imidazo[4,5-b] pyridine

DMIP dimethylimidazopyridine

TMIP trimethylimidazopyridine

Pyrido-imidazoles and indoles

Trp-P-1 3-amino-1,4-dimethyl-5H-pyrido[4,3-b] indole

Trp-P-2 3-amino-1-methyl-5H-pyrido[4,3-b] indole

Glu-P-1 2-amino-6-methyl-dipyrido[1,2-a:3',2'-d] imidazole

Glu-P-2 2-amino-dipyrido[1,2-a:3',2'-d] imidazole

AC 2-amino-9H-dipyrido[2,3-b] indole

MeAC 2-amino-3-methyl-9H-dipyrido[2,3-b] indole

Harman1 methyl 9H pyrido[4,3 b] indole

Norharman 9H pyrido[4,3 b] indole

Furopyridines

MeIFP 2-amino-3-methylimidazo[4,5-f]-4H-1, 4-benzoxazine

Benzoxazines 2-amino-3,4-dimethylimidazo[4,5-f]-4H-1, 4benzoxazine

Cu trc khc

Lys-P-13,4-cyclopentenopyrido-[3,2-a] carbazole

Orn-P-14-amino-6-methyl-1H-2,5,10,10btetraazafluoranthene

Phe-P-12-amino-5-phenylpyridine

1. Phn loi, tnh cht:0. Cho n nay hn 20 loi HAAs c tm thy trong cc loi thc phm c x l nhit, da vo cu trc ca cc phn t HAAs chng c chia thnh nhiu nhm nh nh:1. Nhm amino imidazo quinoline hay cn gi l cc hp cht IQ gm cc cht nh: 2 amino 3 methylimidazol [4,5 f] quinoline (IQ) v 2amino3,4 dimethylimidazol [4,5 f] quinoline (MeIQ) c cng thc cu to nh sau:

1. Nhm amino imidazo quinoxaline hay cn gi l cc hp cht IQx gm cc cht nh: 2amino3methylimidazol [4,5 f] quinoxaline(IQx), 2amino3,8 dimethylimidazol [4,5 f] quinoline (MeIQx) v 2amino3,4,8 (hay 3,7,8) trimethylimidazol [4,5 f] quinoxaline (DiMeIQx) c cng thc cu to nh sau:

1. Nhm amino imidazo pyridines hay cn gi l cc hp cht IP gm cc cht nh: 2 amino 1 methyl 6 phenylimidazo [4,5 b] pyridine (PhIP) v DMIP c cng thc cu to nh sau:

Nhm amino carbolines gm cc cht nh: 1 methyl 9H pyrido[4,3 b] indole (Harman), 9H pyrido[4,3 b] indole (Norharman), 2 amino 3 - methyl 9H pyrido [2,3 b] indole (MeAC), AC, Trp P 1, Trp P 2) c cng thc cu to nh sau:

1. Nhn chung hu ht cc phn t HAAs u c cu trc phn cc v c cha 3 vng thm vi t nht mt phn t Nit nm trn vng thm v mt nhm exocyclic amino, v t mt n bn nhm th methyl. Tuy nhin vn c mt vi ngoi l nh l nhm PhIP v DMIP ch c hai vng thm trong khi th Harman v Norharman khng c mt nhm exocyclic amino no cn nhm IFP th c thm mt phn t oxygen nm trn vng ca phn t [60].

1. Nu da vo c ch to thnh trong qu trnh x l nhit th ta c th chia cc hp cht HAAs thnh hai nhm nh:1. Nhm 1: Cc hp cht HAAs hnh thnh do s phn hy nhit ca cc protein, acid amine cc thc phm giu protein thng qua c ch gc t do khi nhit qu trnh ln n 3000C. Cc hp cht HAAs hnh thnh theo c ch ny cn c gi l tc nhn gy t bin nhit phn, gm cc cht thuc nhm amino carbolines (AC, MeAC, Harman, Norharman, Trp P 1, Trp P 2).Tnh cht: Tt c cc phn t nhm 1 u c nhm amino gn vo vng pyridine, v khi x l vi dung dch nitrite 0.2mM trong mi trng acid th c tnh ca chng khng cn. Nhm 2: Cc hp cht HAAs hnh thnh do phn ng gia cc tc nhn nh: creatine (hoc creatinine), carbonhydrate v cc acid amine nhit thp hn 3000C, thng l t 1500C n 2500C. Cc hp cht HAAs hnh thnh theo c ch ny cn c gi l tc nhn gy t bin nhit, gm cc cht thuc nhm amino imidazo quinoline (IQ), amino imidazo quinoxaline (IQx) v amino imidazo pyridines (IP) [65].Tnh cht: Tt c cc phn t nhm 2 u c nhm amino gn vo vng imidazole v c tnh ca chng vn khng thay i khi x l vi dung dch nitrite 0.2mM trong mi trng acid [29]. Nu phn loi theo tnh phn cc ca phn t th ta chia HAAs ra lm hai nhm: nhm phn cc gm cc cht thuc nhm imidazoquinoline (IQ), imidazoquinoxaline (IQx), imidazopyridine (IP) v nhm khng phn cc gm cc cht thuc nhm pyridoindole, dipyridoimidazole hay nhm amino carbolines [74]. Tnh a bo/a nc: Tnh cht a bo hay a nc ca cc hp cht HAAs ph thuc vo gi tr pH. pH 0.2% (i vi c 3 loi ng kh: glucose, fructose v lactose) v khi nng ng kh >0.67% th c th gim n hn 50% lng c t. Ring i vi ng sucrose th mt lng nh khng c nh hng ng k n lng c t to ra, tuy nhin theo cc nghin cu khc th khi thm mt lng ln sucrose (1.5% w/w) c th gim n 46 54% tng lng c t. Trong cc loi ng trn th glucose c nh hng ln nht n hm lng HAAs to thnh do n l ngun hydrocarbon ch yu tham gia vo cc phn ng to HAAs v sucrose c nh hng nh nht n lng HAAs to thnh [63].1. C ch nh hng ca cc ng ln lng HAAs to thnh vn cha c lm sng t (c bit l sucrose), i vi cc loi ng kh th ngi ta gi nh mt c ch l: khi thm ng kh tng ngoi nng ti thch cho phn ng to HAAs th s c tc dng km hm cc phn ng to HAAs do cc sn phm trung gian ca phn ng Maillard c th kt hp trc tip vi creatine (hay creatinine) cnh tranh c cht vi phn ng to HAAs. Ngoi ra mt s cc sn phm trung gian ca phn ng Maillard c cho l c tnh chng oxy ha (v d nh l: 5 hydroxyl methyl 2 furfural) c tc dng km hm phn ng to HAAs [63]. 1. Hm lng creatine (hay creatinine):1. Creatine (hay creatinine) l tc nhn trc tip cho nhiu phn ng to HAAs, khi th nghim vi h thng hin i vi cc tc nhn phn ng l glucose, glycinie (i din ca acid amine) v creatinine trong dung dch l diethyleneglycol: nc (8: 2, v/v) 1200C trong 2 gi vi nng glucose v glycine c nh (0.4 M glycine v 0.2 M glucose) ta thu c kt qu nh sau:Hm lng HAAs (%)Creatine (M)

Hnh 3.13: Hm lng HAAs sinh ra vi cc nng creatinine khc nhau1. T th trn ta thy rng vi nng glucose v glycine c nh th khi nng creatinine cng tng th lng c t HAAs s tng t l. Tc phn ng s tng nhanh khi nng creatinine