N TT NGHIP GVHD: NGUYN TH M L

N TT NGHIP GVHD: NGUYN TH M L

CHNG 1. TNG QUAN

1.1. c im v nguyn liu thy snc im ca nguyn liu thy sn l theo ma v v xa ni a nn vic bo qun thy sn sau khi khai thc hoc thu hach l rt quantrng. Ty theo iu kin c th m bo qun sn phm thy sn sau thu hoch tt nht. Bo qun v ch bin nhit thp l mt trong nhng phng php c s dng ph bin hin nay.Thnh phn c bn ca nguyn liu thy sn gm c: protein, lipid, glucid, vitamin, nc, khong, cht ngm ra, sc t, ng thi cn cha ng h thng cc Enzyme,Vi sinh vt v cc cht hot ng sinh hc khc.Cc nguyn liu thy sn thng c cu trc a bo, c bit li cha ng cc lp t bo sng, m sng kt cu lng lo, nc chim t l cao,li cha cc cht xc tc sinh hc v h t bo vi sinh vt hin hu t nhin. Do nguyn liu thy sn rt d b bin i. Chnh v vy m vic bo qun v ch bin nguyn liu thy sn l rt cn thit hn ch v bo m cho nguyn liu khng b bin i.Nhn chung nhit bo qun c nh hng rt ln n tc phn gii v n hng do vi sinh vt. Nhit bo qun gim, tc phn hy gim v khi nhit thp s h hng hu nh b ngng li. Trong , phng php bo qun v ch bin nhit thp c s dng rng ri, ph bin.Ngun li hi sn ca nc ta:1.1.1. C C 2.038 loi vi 4 nhm sinh thi ch yu: nhm c ni 260 loi, nhm c gn tng y 930 loi, nhm c y 502 loi v nhm c san h 304 loi. Nhn chung ngun li c bin c thnh phn loi a dng, kch thc c th nh, tc ti to ngun li cao. C bin vng bin VN thng sng phn tn, t kt n; nu c kt n th kch thc n khng ln. T l n c nh (c kch thc di 100m2) chim ti 82% tng s n c, cc n c va (200 m2) chim 15%, cc n c ln (trn 1.000 m2) ch chim 0,1%. S n c mang c im sinh thi vng gn b chim 68%, cc n c mang tnh i dng ch chim 32%. Trong :- Vnh Bc b: tr lng 681.200 tn, kh nng cho php khai thc 272.500 tn/nm;- Vng bin min Trung: tr lng 606.400 tn, kh nng cho php khai thc 242.600 tn/nm;- Vng bin ng Nam b: tr lng 2.075.900 tn, kh nng cho php khai thc 830.400 tn/nm;- Vng bin Ty Nam b: tr lng 506.700 tn, kh nng cho php khai thc 202.300 tn/nm.

Hnh 1.1: Mt s loi c bin

C bin kinh ta. H c thu (Cybiidae)C thu c hnh thon di, mnh dt hai bn. H c thu c 5 loi thuc hai ging, loi ta thng gp l c thu vch, thu chm v thu nht. Thu vch sn lng cao v sau l thu chm.Kch thc khai thc ca c thu l 300-700 mm. C thu l loi c c gi tr kinh t cao, sng tng ni, thng s dng : lnh ng, n ti, hp, kh gia v, nc mm,...nc mm c thu l mt tuyt tc ca vn ha m thc Vit Nam.

Hnh 1.2: C thub. H c ng (Thunnidae)C ng c thn hnh thoi hi dt. C ng c nhiu loi, nc ta xc nh c 3 loi: ng b, ng ch, ng chm, trong ng b c sn lng cao nht. Vng bin no xut hin ng b (b ng, ng i dng) l vng bin c c mp, c nhm.C ng sng tng ni v tng gia, ma v chnh l ma xun v ma h. C ng c kch thc khai thc l 300-600 mm. C ng dng : n ti, lnh ng, ng hp, hun khi...Trong c ng hun khi l mn truyn thng ca cc dn tc Bc u v cng l mn n khoi khu ca ngi Nht Bn.

Hnh 1.3: C ngc. H c chim trng (Stromateidae)C chim c thn hnh thoi, mnh rt dt. H c chim c 4 loi thuc 2 ging khc nhau, trong c chim gai l c sn lng cao nht.C chim gai l loi c qu, tht thm nhng kt cu c tht khng chc.Ma v nh bt c chim l t thng 11-4 nm sau, kch thc khai thc 200-300 mm, khi lng 200-600 gram. C chim c bc o Bch Long V, Qung Nam, Thun Hi, Kin Giang.

Hnh 1.4: C chimd. H c chim n (Nomeidae)C chim n c thn hnh bu dc, mnh bt. C c quanh nm nhng tp trung vo thng 10 m lch cho n thng 4 nm sau. Kch thc khai thc l khong 125-160 mm, khi lng ti a 300 gram.e. H c trch (Clupeidae)C trch c thn di hnh bu dc, hai bn dt, a s sng bin nhng mt s sng sng. C trch c nhiu loi, nc ta xc nh c 21 loi thuc 10 ging trong trch b, trch xng, c nhm, c mi c, c cm l c sn lng cao.C trch thng i thnh tng n v c hin tng di c. C trch c vng bin Qung Ninh, Thun Hi, Cn o. C trch t thng 3-7 v ma v khai thc t thng 9-11. C trch c nhiu m, tht chc thm, thng dng n ti, du c, ng hp.C trch b: l loi c ngon, c nhiu Hi Phng, Thi Bnh, v khai thc t thng 2-4. C trch b c chiu di khi thc t 280-550 mm, khi lng ti a 750 gram, dng n ti, kh p mui.C mi c: thng tp trung ven b bin, cc ca sng, phn b t Hi Phng n Ninh Thun. C c v khi thc chnh t thng 3-9 v 10-4 nm sau. C mi c c nhiu m, tht thm nhung nhiu xng dm, chiu di khai thc 160-230 mm, trng lng ti a 340 gram.

Hnh 1.5: H c trchf. H c mi (Synodidae)C mi l loi c thng tng nc gn y, thn trn v di, chiu di gp 8 ln chiu cao. Vit Nam xc nh 9 loi thuc 4 ging, trong c 5 loi l gi tr kinh t cao: mi vch , mi thng, vy lng di, vy lng ngn, mi hoa.C mi vch: sng khp vng bin, xut hin quanh nm, chiu di khai thc 140-250 mm, khi lng ti a 500 gram.C mi vy lng di: c quanh nm, chiu di khai thc 200-300 mm, khi lng ti a 700 gram.C mi c nhiu tht nhng t chc c tht lng lo, dng n ti, kh gia v, nc mm, surimi...

Hnh 1.6: C mig. H c phn (Mullidae)C c thn hnh bu dc di, ln hi dt, chiu di gp 4-6 ln chiu cao, l loi c y v phn b khp ni. Vit Nam xc nh 10 loi thuc 4 ging, trong phn khoai, phn 1 sc, phn 2 sc l c sn lng cao.C phn khoai: L loi c nh nhng sn lng cao, chim 5% tng sn lng nh bt. C c chiu di khai thc 80-120 mm, khi lng ti a 120 gram.C phn 1 sc: C c mu hng v 1 sc bn, phn b kh rng ri, v chnh t thng 8 n 3 nm sau. C c chiu di khai thc l 10-120 mm, khi lng ti a 120 gram.C phn 2 sc: tng t c phn 1 sc, ch khc l c 2 sc 2 bn.Cc loi c phn dng n ti, kh, gia v, nc mm.

Hnh 1.7: C phnh. H c (Sciaendae)H c sng gn y thuc vng nhit i v nhit i. Vit Nam c 20 loi thuc 9 ging, trong : c , c s... l c gi tr.C : C c sn lng chim 2% so vi tng sn lng nh bt. C c thn hnh bu dc, chiu di gp 3,5-3,8 chiu cao. C c chiu di khai thc 150-170 mm, khi lng ti a 1100 gram. H c dng n ti, phi kh, ng hp.

Hnh 1.8: C C nc ngt kinh ta. C m trng Vit Nam (Hypophthalmichthys harmandi)Thn c dp bn, u ln, mt thp, mm t ngn v hng trn. C c khong cch hai mt rng, mt t do khng c mng da che. Mng mang c rng. Lng c mu xm en, bng trng, c c nui ph bin min Bc v nay vo Nam. C c nui ao, h, m, sng ct... C n thc vt ph du ln nhanh, c ln thng thu hoch c 2-5 kg.

Hnh 1.9: C m trng Vit Namb. C tri (Cirrhina molitorella)C tri thn dp va, kh cao. C c ngc v bng trn, u ngn v rng, ming di nm ngang hi un cong, c mt i ru mm v mt i ru hm, i ru hm rt nh v i khi thiu. C c mt hai bn, khong cch hai mt rng v hi li. ng bn thng gn nh thng, vy to, c t 7-8 vy pha trn vy ngc mu xanh en. C c mu xm v nht dn v pha bng, cc vy mu xm. C tri c nhiu sng sui ln min ni v c nui ph bin trong h, ao, m ng bng. C c kch thc nh tht ngon thm, dng n ti, ng hp, thc n gia v.

Hnh 1.10: C tri

c. C chp (Cyrinus carpio)Thn c dp bn, u c thun cn i. C c hai i ru, ming kh rng hng ra pha trc, gai cng vy lng v vy hu mn u c rng ca mt trong. C c mu thm trn lng, bng trng, cnh cc vy mu . C chp l loi c nui ph bin nc ta, chng sng c hu ht cc loi thy vc, khp cc vng a l. Do vng phn b v iu kin mi trng sng nn c chp hay bin d, ni bt l bin d v hnh dng, mu sc c ln v s lng vy. Hin c c chp trng, , tm, vng. C chp tht chc thm ngon, dng n ti, ng hp, thc n gia v. C chp c trng lng thu hoch t 1-3 kg.Hnh 1.11: C chpd. C chui (Ophiocephalus maculatus) v c xp (Ophiocephalus striatus)Chng c thn di, gn trn pha ui, dp bn. Ton thn ph vy lc ln, ming rt ln v c th co dui c, mt ln hai bn u, khe mang ln. C chui c ng bn gin on, u hi nhn. C xp c ng bn gy khc, nh u rt rng v dp bng. C xp c kch thc ln hn c chui. C chui c mu xm nu en, xen k cc vch en c cc vn chm en. C xp c mu sng hn c chui, c c mu xm thn, bng trng, mt s c rt nhiu chm en bng. C chui v c xp c vng phn b kh rng khp cc min ao, h, m rung... Chng c th sng nc l, thuc loi c d. C c khi lng trung bnh 400-800 gram. C chui v c xp c tht chc thm ngon dng n ti v thc n gia v.

Hnh 1.12: C chui v c xpe. C r phi (Tilapia mosambica) v c r (anabas testudineus)C r phi c dng hnh bu dc, u hi to, mt to trn, ton thn ph vy, c mu hi en lng, bng c mu sng bc, vy c pht hng l loi c nhp v nui ph bin nc ta v pht trin mnh. C r trn hn c r phi, mu vng nht, lng thm hn bng, sau np mang v cun ui c chm en trn. C r c khp ni, tht c thm v chc hn c r phi. Mt dng ca c r phi hay cn gi l c iu hng.

Hnh 1.13: C r phi v c rf. C tra v c ba saC c hnh thoi dt bn, chiu di gp 4 ln chiu rng. C tra khng c vy. Vy lung th nht c 5 tia, vy lng th hai l vy m, vy hu mn c 39 tia.C tra l i tng nui ph bin min Nam nc ta v Campuchia. C c kch thc ln, dng n ti, hp, ng lnh, kh, gia v, hun khi... chiu di khai thc vo c 800-1000 mm.C ba sa tng t c tra nhng vy c mu nht hn, bng trng v to hn, u nh hn. C ba sa ang l i tng xut khu hng lot vo th trng M (ang gp kh khn).

Hnh 1.14: c tra v c ba sa

1.1.2. Gip xc: C 1640 loi, quan trng nht l cc loi trong h tm he, tm hm, cua bin.Tm l i tng quan trng ca ngnh v n chim 70-90% kim ngch xut khu ton ngnh. Tm c gi tr dinh dng cao, t chc c tht rn chc, mi v thm ngon d tiu ha. Ngh ch bin tm, c bit l tm ng lnh v cc dn xut t tm v ang l ngnh mi nhn.Kh nng khai thc 50.000-60.000 tn/nm.

Hnh 1.15: Mt s loi gip xcH tm he (Penaeidae)a. Tm s (Penaeusmonodon) Cn gi l tm c l loi tm c kch thc ln, khi cn ti v u ngc tm c vn ngang. Tm s phn b rng t m nc l ra vng bin su khong 400m, tp trung nhiu su 10-25 m. Tm c quanh nm, nhng ma v chnh t thng 2-4 v thng 7-10. Tm c chiu di khai thc 150-250 mm vi khi lng t 50-150 gram. Tm s l loi tm ngon, tht chc, thm c gi tr kinh t cao (ch sau tm he).

Hnh 1.16: Tm sb. Tm th (Penaeus semisulcatus)Cn gi l tm s vn. Tm c mu c trng xanh thm, vn ngang bng, ru c khoang vng nht. Tm phn b t nng ra su n 60m nhng tp trung nhiu su 20-40 m. Tm c nhiu ni Trung B, tp trung nhiu Ph Yn, Ngha Bnh. Tm c ma v t thng 2-4 v thng 7-9, chiu di khai thc khong 120-250 mm, vi khi lng 40-145 gram.

Hnh 1.17: Tm thc. Tm he (Penaeus teraoi)L loi tm c kch thc kh ln, chiu di khai thc 150-240 mm v khi lng t 30-80 gram.

Hnh 1.18: Tm heH tm hm (Homaridae)a. Tm hm sao (Panuliurs ornitus)Cn gi l tm hm bng. Tm c kch thc ln , phn b rng, xut hin quanh nm, chiu di khai thc trung bnh l 150-450 mm, khi lng 1230-2320 gram.

Hnh 1.19: Tm hm saob. Tm hm (Panulirus longipes)Phn b t bin Qung Bnh n Bnh Thun, tp trung nhiu Cam Ranh, xut hin quanh nm, nhng ma v tp trung l thng 7-9. Tm c chiu di khai thc trung bnh 160-280 mm, khi lng 245-495 gram.

Hnh 1.20: Tm hm c. Tm hm si (Panulirus homarus)Cn gi l tm hm . Tm phn b rng, xut hin quanh nm nhng tp trung cc thng 11-1 nm sau. Tm c chiu di khai thc 165-350 mm, khi lng 275-585 gram.

Hnh 1.21: Tm hm d. Tm hm Thompssoni (Nephrops thomppsoni)Phn b pha Bc, l loi tm c tht ngon, tm c chiu di khai thc trung bnh t 120-160 mm, khi lng 45-85 gram.H tm cng (Palaemonidae)Theo iu tra th h tm cng nc ta c 4 ging Palaemon, Macrobrachium, Letocarpus, Leandrites. Trong ging Palaemon gp 4 loi v ging Macrobrachium gp 3 loi v l loi c gi tr kinh t cao nht.a. Tm cng xanh (Macrobrachium) L i tng nui v khai thc t nhin ln trong sng ngi, knh, rch,...vng Nam B. Tm sng c c nc l v nc ngt. Tm c chiu di khai thc trung bnh l 110-200 mm v khi lng 30-120 gram. Tm c quanh nm nhng tp trung t thng 10-12. Thn tm trn c mu xanh l m, chy pht trin, nhn cong vt ln t b trn c 11-15 rng v di c 12-15 rng. Tm c i ng tc th hai pht trin thnh cng ln mu xanh l m, phn di mu vng nu hoc da cam. Theo thng k n nay th s lng khai thc tm cng xanh ng bng Nam B khong 65.000 tn/ nm.

Hnh 1.22: Tm cng xanhCc loi gip xc khca. Cua, ghTrn th gii v khu vc ng Nam th cua, gh bin gi vai tr th hai v sn lng khai thc hng nm. nc ta, n nay ngh nui v khai thc cua vn cha pht trin.Cua, gh c khp b bin Vit Nam v c quanh nm nhng tp trung vo nhng thng ma ma. Theo s b thng k th sn lng khai thc ca ta hin nay t khong 3.500 tn/ nm. Cua, gh nc ta c nhiu loi nhng loi nh bt ph bin l Portunis, Neptunus, Chorydis,...Cua, gh dng n ti, ng hp, i lc lm mm.Hnh 1.23: Cua v Gh

b. Moi binMoi cn gi l con ruc. Moi l i tng ang c ch nhiu trn th gii v sn lng ln khong 160 triu tn/ nm. l gun cung cp protein tim nng cho loi ngi. Hin nay Nga v Nht l hai nc dn u khai thc ch bin moi Thi Bnh Dng. Theo thng k s b th nc ta mi khai thc khong 20.000 tn/ nm. Moi c ch bin thnh mm tm, phi kh hoc chit rt protein.

Hnh 1.24: Moi bin1.1.3. Nhuyn th: C trn 2500 loi, quan trng nht l mc, s, ip, nghu, v.v. Kh nng khai thc mc 60.000-70.000 tn/nm, nghu 100.000 tn/nm.

Hnh 1.25: Mt s loi nhuyn thNhuyn th chn uNhuyn th chn u bao gm mc v bch tuc. Mc phn b khp ni v c tr lng ln, mc thng tp trung cc vng gp nhau ca hai dng hi lu lnh.a. Mc mai (Sepia subaculeata)Cn gi l mc nang hay mc tm. Mc mai c c th ln, thn hnh bu dc bp. Trn lng c mt thanh trng xp hnh bu dc gi l mai mc, trong thn mc c ti nc mc mu en, lng c nhiu hoa vn, on cui ca nang mc bin thnh gai th. Mc nang phn b rng khp min Nam Thi Bnh Dng, sng tng gia v tng y. Ma v phi Bc l t thng 10-12 v 1-2 cn phi Nam l thng 7-9 v ko di n thng 2 nm sau. Mc mai c kch thc khai thc trung bnh 180-300 mm v khi lng t 200-500 gram.

Hnh 1.26: Mc maib. Mc mai vn h (Sepia tigris)Mc mai vn h gn ging mc mai thng, c kch thc ln hn mc mai v mt lng phn thn c nhiu vn ging da h nn gi l mc mai vn h. Mc phn b rng nh mc mai t vnh Bc B n vnh Thi Lan, vng Trung B tp trung nhiu t Nng n Thun Hi, ma v tng t mc mai. Mc mai vn h c chiu di trung bnh t 200-320 mm v khi lng khong 200-600 gram.c. Mc ng (Logigo formosana)Mc ng c thn hnh nh ci ng, trn lng c mt thanh mnh cu to bng cht sng, trong bng c ti mc, ton thn nh mt ha tin. Mc c chiu di gp 6 ln chiu rng, ui nhn. Mc ng sng tng mt v tng gia vng xa b, tnh hng quang ln nn ng dn dng nh sng tp trung mc v vy bt.Mc ng phn b t min Nam bin Nht Bn n Vit Nam v Malaysia. Thng 5-10 mc p lng sinh sn t thng 12-4 nm sau th ra khi, Vit Nam mc tp trung nhiu Thun Hi, Qung Ninh, Thanh Ha, Ph Yn, Khnh Ha. Mc c chiu di khai thc 200-400 mm, khi lng 20-150 gram.

Hnh 1.27: Mc ngd. Mc th (Loligochinensis)Mc th c dng tng t mc ng nhng kch thc nh hn, mc c chiu di gp 3-4 ln chiu rng, u bng khng nhn. Mc sng tng mt v tng gia, tnh hng quang mnh, phn b khp Vit Nam v tp trung nhiu Trung Trung B n vnh Thi Lan. Ma v gn nh mc ng.Nhuyn th hai mnh va. Vm (Mytylus)Vm c kh nng khai thc th hai trong cc loi nhuyn th. Khp vng bin Vit Nam ni u c vt bm l c vm nhng tp trung ch yu Qung Ninh, Hi Phng, Bnh Tr Thin. Vm Vit Nam c 10 loi nhng c ngha hn c l vm xanh (Mytylus smarasgdinus), vm v dy (Mytylus crassitesta)...Tht vm c nhiu glycogen v nhiu cht ngm ra nn hng v ngon ngt.Hnh 1.28: Vmb. S (Arca anardar)S c nhiu loi nhng gi tr l s huyt (A.A Granosa) s Anty (A.A Antiquata). S c nhiu ni nhng tp trung nhiu Thun Hi, C Mau.c. Ngao (Meretrix)Ngao cn gi l nghu c sn lng xp th 3 trong nhuyn th. Ngao c nhiu loi nhng gi tr nht l ngao du (Meretrix meretrix) ngao mt ( Milui usoria) ngao vn (Venerupis), tt c bi triu Vit Nam u c ngao, nhng vng c sn lng cao l: Thanh Ha, Hu, Bn Tre, G Cng.

Hnh 1.29: Nghud. ip (Amussium)ip sng bin su ni c dng chy mnh v y c bn ct. Vit Nam c nhiu ip nhng ln nht l ip Nht Nguyt (Amussium Japonica). ip tp trung nhiu Thun Hi, Ngh Tnh.Hnh 1.30: ip1.1.4. ToBin Vit Nam c trn 200 loi to rong nhng c gi tr khong chc loi, trong ni bt l rong cu, rong m, rong mt, rong bn v vi loi to. So vi thc vt trn cn rong bin c xellulose t hn nhng ng nhiu hn.a. Rong cun nay xc nh c 20 loi, trong rong cu ch vng l c gi tr nht. Rong cu phn b khp ni nhng cng vo Nam th mt cng cao. Vng c tim nng khai thc cao l Qung Bnh, Hu, Thun Hi, Nha Trang. Sn lng rong kh hin t 4.000 tn/ nm. Rong cu cho Agar v hm lng ny thay i theo ging loi, thi k sinh trng.

Hnh 1.31: Rong cu ch vngb. Rong m Vit Nam c khong 30-40 loi rong m, chim sn lng t nhin hng u trong cc loi rong bin khp Vit Nam, tp trung nhiu Thun Hi, Ph Yn, Khnh Ha. Rong m dng sn xut Alginate l mt loi vt liu qu, hm lng Alginic trong rong m Vit Nam khong 25% trng lng kh.

Hnh 1.32: Rong mNhn chung ngun li thy sn ven b (di 30m su ni chung v 50m vngbin min Trung) b khai thc trong khi ngun li thy sn xa b cn ln nhng cha khai thc ht.1.2. Thnh phn ha hc ca nguyn liu thy snThnh phn ha hc gm: nc, protein lipid, mui v c, vitamin... Cc thnh phn ny khc nhau rt nhiu, thay i ph thuc vo ging, loi, gii tnh, iu kin sinh sng,... Ngoi ra, cc yu t nh thnh phn thc n, mi trng sng, kch c c v cc c tnh di truyn cng nh hng n thnh phn ha hc, c bit l c nui. Cc yu t ny c th kim sot c trong chng mc no .S khc nhau v thnh phn ha hc ca c v s bin i ca chng c nh hng n mi v v gi tr dinh dng ca sn phm, vic bo qun ti nguyn liu v qui trnh ch bin.

Bng 1.1: Thnh phn ha hc ca c tng c quan, b phn c s khc nhauThnh phn ch tiuNcProteinLipidMui v c

Tht c48 85,110,3 24,40,1 5,40,5 5,6

Trng c60 7020 - 301 - 111 2

Gan c40 758 - 183 - 50,5 1,5

Da c60 707 - 155 - 101 - 3

Bng 1.2: Thnh phn ha hc ca mt s loi thy sn

Thnh phn LoiProtein%Lipid%Glucid%Tro%Canxi%Phosphat%St%

Mc17-200,8--54-1,2

Tm19 -230,3 121,3 1,829 - 3033-671,2-5,1

Hu11-131 - 2-2,20,21--

S8,80,43437821,9

Trai4,61,12,51,96681071,5

c11-120,3-0,73,9-8,31 4,3310-66051-1210-

Cua161,51,5-40-1

nh hng ca thnh phn ha hc n cht lngYu t nh hng r nht n thnh phn ha hc ca c l thnh phn thc n. Thng thng c nui thng c cho n thc n cha nhiu lipid c pht trin nhanh. Tuy nhin, khi hm lng lipid cao d cung cp nng lng th lipid d tha s c tch ly cc m lm cho c c hm lng lipid rt cao. Ngoi nh hng khng tt n cht lng ni chung, n cng c th lm gim nng xut ch bin v lipid d tr c xem nh ph liu, b loi b cng vi ni tng sau khi moi rut v phi l.Cch thng thng gim hm lng lipid ca c nui trc khi thu hoch l cho c i mt thi gian. Ngoi ra, cho c i cn c tc dng gim hot ng ca enzym trong ni tng, gip lm chm li cc bin i xy ra sau khi c cht.1.2.1. LipidThnh phn ch yu ca cht bo trong ng vt thu sn l triglycerit do acid bo bc cao ha hp vi glycerin. Cht bo trong ng vt thy sn c vai tr quan trng trong hot ng sng ca chng. Cht bo trong ng vt thu sn thng c mu vng nht, mt s loi c mu , thng th lng Vitamin A trong du cng nhiu th du cng c mu thm.Ngi ta thng da vo lng m c chia c ra nhm c bo khi lng m c cao hn 10% nh c trch, h c Scomber sp. v nhm c gy c lng m c thp hn 2% nh nhm c thu (lipid d tr ch yu trong gan c th t 50%). Gia hai nhm trn l nhm c trung gian c m c trong khong 2-6% Acid bo ca ng vt thy sn thuc loi mch thng c mt gc cacboxin, chui cacbon di nht 28 C, ch yu l C18-C22. Trong du c acid bo cha bo ha (nhm n-3 v n-6) chim ti 84% do d b oxy ha v thi ra, qu trnh oxy ha du c sn sinh ra rt nhiu cht thuc loi andehit, ceton, loa acid bo cp thp lm cho du c mi hi kh chu.Bng 1.3: Thnh phn ha hc ca mt s loi ng vt thu sn (% lipid)

LoiNucProteinLipidKhongCacbohydrat

Gip xc76.017.82.102.10-

Nhuyn th81.013.01.501.602.90

Trm c74.017.45.801.50-

Tm s75.2221.041.83-

Hnh 1.4: S phn b lipid c Thu v c t.1.2.2. ProteinProtein l thnh phn ha hc ch yu trong tht ng vt thy sn, chim khong 60- 75 % (trng lng kh).Protein trong c th ng vt thy sn thng lin kt vi nhm cht hu c khc nh lipid, acid nucleic, glycogen to thnh cc phc cht phc tp c nhng tnh cht sinh hc c trng khc nhau.Protein trong t chc c tht ng vt thy sn c chia lm 2 nhm chnh: cht c ha tan (Mucle plasma) v cht c c bn ( Mucle stroma). T l cht c ha tan v cht c c bn trong tht c khc nhau theo ging loi nhng so vi ng vt trn cn th t l cht c ha tan ln hn rt nhiu cht c c bn. Protein ca cht c c bn chim khong 3-15% tng lng protein c tht.

Bng 1.4: Hm lng mt s acid amin trong c th c chp (% Protein).Acid aminHm lngAcid aminHm lng

AlaArgAspGluGlyHisIso6.96.010.916.63.702.205.10LeuLisMetPheProTreTri9.2011.63.305.103.105.05.90

C th chia protein ca m c c ra thnh 3 nhm:* Protein cu trc (Protein t c)Gm cc si myosin, actin, actomyosin v tropomyosin, chim khong 65-75% tng hm lng protein trong c v khong 77-85% tng hm lng protein trong mc. Cc protein cu trc ny c chc nng co rt m nhn cc hot ng ca c. Myosin v actin l cc protein tham gia trc tip vo qu trnh co dui c. Protein cu trc c kh nng ha tan trong dung dch mui trung tnh c nng ion kh cao (>0,5M).* Protein cht c (Protein tng c)Gm myoglobin, myoalbumin, globulin v cc enzym, chim khong 25-30% hm lng protein trong c v 12-20% trong mc. Cc protein ny ha tan trong nc, trong dung dch mui trung tnh c nng ion thp (72

-10672

-15648

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C chp (Cyprinus carpio)-08-

-1060-

-2016-

B sc01-

Khng b sc06-

Ni chung, ngi ta tha nhn rng iu kin nhit cao th thi im t cng n sm v thi gian t cng ngn. Tuy nhin, qua nghin cu, c bit i vi c nhit i, ngi ta thy rng nhit li c nh hng ngc li i vi s bt u ca qu trnh t cng. Bng chng l i vi cc loi c ny th s t cng li bt u xy ra sm hn nhit 0oC so vi nhit 10oC cc loi c khc, m iu ny c lin quan n s kch thch nhng bin i sinh ho 0oC. Tuy nhin, Abe v Okuma (1991) qua nghin cu s xut hin qu trnh t cng trn c chp cho rng hin tng t cng ph thuc vo s khc bit gia nhit mi trng ni c sng v nhit bo qun. Khi c s khc bit ln th khong thi gian t khi c cht n khi xy ra hin tng t cng tr nn ngn hn v ngc li.Hin tng t cng xy ra ngay lp tc hoc ch sau mt thi gian rt ngn k t khi c cht nu c i v ngun glycogen d tr b cn hoc c b sc (stress). Phng php p v git cht c cng nh hng n thi im bt u hin tng t cng. Lm cht c bng cch gim nhit (c b git cht trong nc lnh) lm cho s t cng xut hin nhanh, cn khi p vo u c th thi im bt u t cng s n chm, c th n 18 gi. ngha v mt cng ngh ca hin tng t cng l rt quan trng khi c c phil vo thi im trc hoc trong khi t cng. Nu phil c trong giai on t cng, do c th c hon ton cng nn nng sut phi l s rt thp v vic thao tc mnh c th gy rn nt cc ming phil. Nu c c phil trc khi t cng th c c th co li mt cch t do v ming phil s b ngn li theo tin trnh t cng. C mu sm c th co li n 52% v c mu trng co n 15% chiu di ban u. Nu luc c trc khi t cng th cu trc c tht rt mm v nho. Ngc li, luc c giai on t cng th c tht dai nhng kh, cn nu luc c sau giai on t cng th tht c tr nn sn chc, mm mi v n hi.C nguyn con v c phi l ng lnh trc giai on t cng c th s cho ra cc sn phm c cht lng tt nu r ng mt cch cn thn chng nhit thp, nhm mc ch lm cho giai on t cng xy ra trong khi c vn cn c ng lnh.Nhng bin i c trng v cm quan sau khi c cht rt khc nhau ty theo loi c v phng php bo qun. bng 3.1, EEC a ra m t khi qut hng dn nh gi cht lng ca c. Thang im t 0 n 3 trong im 3 tng ng vi mc cht lng tt nht.3.1.2. Bin i cht lngC th pht hin v chia cc kiu n hng c trng ca c bo qun bng nc theo 4 giai on (pha) nh sau:- Giai on (pha) 1: C rt ti v c v ngon, ngt, mi nh rong bin. V tanh rt nh ca kim loi.- Giai on (pha) 2: Mt mi v v c trng. pH ca tht c tr nn trung tnh nhng khng c mi l. Cu trc c tht vn cn tt .- Giai on (pha) 3: C du hiu n hng v ty theo loi c cng nh l kiu n hng (hiu kh, ym kh) m s to ra mt lot cc cht d bay hi, mi kh chu. Mt trong nhng hp cht bay hi c th l trimethylamin (TMA) do vi khun sinh ra t qu trnh kh trimethylamin oxyt (TMAO). TMA c mi c tanh rt c trng. Ngay khi bt u giai on (pha) ny, mi l c th l mi hi chua, mi nh tri cy v mi hi ng, c bit l cc loi c bo. Trong nhng thi k tip theo ca giai on ny, cc mi tanh ngt, mi nh bp ci, mi khai, mi lu hunh v mi i kht tng ln. Cu trc hoc l tr nn mm v sng nc hoc l tr nn dai v kh.- Giai on (pha) 4: c trng ca c c th l s n hng v phn hy (thi ra).Bng 3.2: nh gi ti: Qui ch ca Hi ng (EEC) No. 103/76 OJ No.L20(28-01-1976) (EEC,1976).

Cc b phn c kim traCc tiu ch

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Dch nht trong sut nh c nc.Dch nht hi c.Dch nht trng c.Dch nht m c.

MtLi (phng ln).Li v hi trng.Phng.Lm gia.

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Cc c quanThn v phn cn li ca cc c quan khc phi sng nh mu trong ng mch ch.Thn v phn cn li ca cc c quan khc phi c, mu b bin mu.Thn, phn cn li ca cc c quan khc v mu phi c mu nht.Thn, phn cn li ca cc c quan khc v mu phi c mu nu nht.

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Ct sngGy, thay v ri ra.Dnh.Hi dnh.Khng dnh.

Mng bngDnh han ton vo tht.Dnh.Hi dnh.Khng dnh.

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C th dng thang im nh gi cm quan i vi c luc nh trnh by bng 3.2. Thang im c nh s t 0 n 10. im 10 ch ti tuyt i, im 8 ch cht lng tt, im 6 ch mc cht lng trung bnh, tht c khng c v c trng v im 4 ch mc b loi b. Khi dng thang im ny, th c dng ch S cho thy giai on u tin, cht lng ca c gim nhanh chng, giai on 2 v 3 tc gim cht lng chm hn, cn giai on cui cng, tc gim cht lng xy ra nhanh mt khi c b n thi

Hnh 3.2: Bin i cht lng ca c tuyt p (0oC)3.1.3. Bin i t phn giiNhng bin i t phn gii do hot ng ca enzym gp phn lm gim cht lng ca c, cng vi qu trnh n hng do vi sinh vt gy nn.3.1.3.1. S phn gii GlycogenGlycogen b phn gii di tc dng ca men glycolysis trong iu kin khng c oxy bng con ng Embden Meyerhof, dn n s tch ly acid lactic lm gim pH ca c tht c. i vi c tuyt, pH c tht gim t 6,8 xung mc pH cui cng l 6,1-6,5. Vi mt s loi c khc, pH cui cng c th thp hn: c thu c ln th pH c th gim xung n mc 5,8-6,0; c ng v c bn li nga th pH gim xung n 5,4-5,6; tuy nhin pH thp nh vy t khi thy cc loi c xng bin. pH ca c tht c him khi thp bng pH ca c tht ng vt c v sau khi cht. V d c tht b th pH thng gim xung n 5,1 trong giai on t cng. Lng axit lactic c sn sinh ra c lin quan n lng cacbohydrat d tr (glycogen) trong m c khi ng vt cn sng. Ni chung, do c tht c c hm lng glycogen tng i thp so vi ng vt c v nn sau khi c cht th lng acid lactic c sinh ra t hn. Trng thi dinh dng ca c, hin tng sc v mc hot ng trc khi cht cng c nh hng ln n hm lng glycogen d tr v do nh hng n pH cui cng ca c sau khi cht.Theo quy lut, c n nhiu v ngh ngi nhiu s c hm lng glycogen nhiu hn c b kit sc. Mt nghin cu gn y v c chch Nht Bn cho thy rng ch vi pht gy giy gia khi nh bt c lm cho pH ca c gim 0,5 n v trong 3 gi so vi c khng giy gia khi nh bt th pH ca n ch gim 0,1 n v trong cng thi gian nh trn. Ngoi ra, cc tc gi ny cn cho thy vic ct tit lm gim ng k s sn sinh axit lactic sau khi cht.PH ca c tht c gim sau khi c cht c nh hng n tnh cht vt l ca c tht c. Khi pH gim, in tch b mt ca protein si c gim i, lm cho cc protein b bin tnh cc b v lm gim kh nng gi nc ca chng. M c trong giai on t cng s mt nc khi luc v c bit khng thch hp cho qu trnh ch bin c x l nhit, v s bin tnh do nhit cng lm tng s mt nc. S mt nc c nh hng xu n cu trc ca c tht c cho thy gia dai c tht v pH c mi quan h t l nghch, dai mc khng th chp nhn c (mt nc khi luc) s xy ra c tht c pH thp (Hnh 3.3).Hnh 3.3: Mi quan h gia cu trc ca c tht c tuyt v pH

Du chm en tng ng vi c nh bt St. Kilda, bin i Ty Dng.Du tam gic tng ng vi c nh bt Fyllas Bank, Davis Strait .S bin i pH ca c sau khi cht ph thuc rt ln vo nhit mi trngT th hnh 3.4 ta thy khi pH gim xung thp nht th c cng v khi pH tr li trung tnh th c mm v sau khi mm th tin n t phn gii ri thi ra.Khi pH gim, s ht nc ca c th c cng gim. Khi pH = 7 lng nc ht vo bng dung tch ca c tht. Khi pH = 6 th di 50% v khi pH = 5 th gn n im ng in ca protein nn lng nc ht vo b nht ch khong 25%.Tm li: C bt ln mt thi gian ri cht c pH = 7, sau gim xung n pH thp nht, c tr nn cng. pH gim n mt mc no li tng ln gn trung tnh, c lc ny tr nn mm.

Hnh 3.4: S s bin i pH ca c sau khi cht

A. Thi gian khi nh bt B. Thi gian khi cht, bt u t cng C. C c pH thp nht D. C cng nht E. C bt u mm F: C bt u n hng G: C n hng 3.1.3.2. S phn hy ATPSau khi cht, ATP b phn hy nhanh to thnh inosine monophosphate (IMP) bi enzym ni bo (s t phn). Tip theo s phn gii ca IMP to thnh inosine v hypoxanthine l chm hn nhiu v c xc tc chnh bi enzym ni bo IMP phosphohydrolase v inosine ribohydrolase, cng vi s tham gia ca enzym c trong vi khun khi thi gian bo qun tng. S phn gii ATP c tm thy song song vi s mt ti ca c, c xc nh bng phn tch cm quan.ATP b phn hy xy ra theo bi cc phn ng t phn:Hnh 3.5: S phn hy ATPTrong tt c cc loi c, cc giai on t phn xy ra ging nhau nhng tc t phn khc nhau, thay i ty theo loi.Glycogen v ATP hu nh bin mt trc giai on t cng, trong khi IMP v HxR vn cn duy tr. Khi hm lng IMP v HxR bt u gim, hm lng Hx tng ln. pH gim xung n mc thp nht giai on t phn ny.ATP nh l cht ch th ha hc v ti:Ch s ha hc v ti ca c l biu hin bn ngoi bng cch nh lng, nh gi khch quan v cng c th bng cch kim tra t ng. Mt mnh ATP khng th s dng nh gi ti bi v ATP nhanh chng chuyn i to thnh IMP. Sn phm trung gian ca s phn hy ny tng v gim lm cho kt qu khng chnh xc. Khi xc nh kt qu, cn ch n inosine v hypoxanthin, cht chuyn ha cui cng ca ATP.Hypoxanthine c dng nh mt tiu chun nh gi mc ti ca c. Tuy nhin, iu ny c th dn n s nhm ln khi so snh gia cc loi vi nhau. mt s loi qu trnh phn hy to thnh HxR trong khi cc loi khc li sinh Hx. V vy, nhn bit mc ti ca c mt cch chnh xc ngi ta a ra tr s K. Tr s K biu din mi lin h gia inosine, hypoxanthine v tng hm lng ca ATP thnh phn::Trong , [ATP], [ADP], [AMP], [IMP], [HxR], [Hx] l nng tng i ca cc hp cht tng ng trong c tht c c xc nh ti cc thi im khc nhau trong qu trnh bo qun lnh. Tr s K cng thp, c cng ti.3.1.3.3. S phn gii ProteinBin i t phn ca protein trong c t c ch . H enzym protease quan trng nht l men cathepsin, trong c chng hot ng rt thp, nhng ngc li hot ng mnh cc loi tm, cua v nhuyn th.a. Cc enzym cathepsinCathepsin l enzym thy phn nm trong lysosome. Enzym quan trng nht l cathepsin D tham gia vo qu trnh thy phn protein ni ti ca t bo to thnh peptide pH = 2-7. Sau peptide tip tc b phn hy di tc ca men cathepsin A, B v C. Tuy nhin, qu trnh phn gii protein di tc dng enzym thy phn trong tht c rt t. Enzym cathepsin c vai tr chnh trong qu trnh t chn ca c pH thp v nng mui thp. Enzym cathepsin b c ch hot ng nng mui 5%.Hnh 3.6: Mt s enzyme Cathepsin

b. Cc enzym calpainGn y, ngi ta tm thy mi lin h gia mt nhm enzym proteaza ni bo th hai c gi l "calpain" hay "yu t c hot ha bi canxi" (CAF) i vi qu trnh t phn gii c tht c c tm thy trong tht, cc loi c c vy v gip xc.Cc enzym calpain tham gia vo qu trnh lm gy v tiu hy protein trong si c.Hnh 3.7: Mt s enzyme Calpain

c. Cc enzym collagenaseEnzym collagenase gip lm mm t bo m lin kt. Cc enzym ny gy ra cc vt nt hoc b gy cc myotome khi bo qun c bng trong mt thi gian di hoc khi bo qun ch trong thi gian ngn nhng nhit cao. i vi c hi i Ty Dng, khi nhit t n 17oC th s nt rn c l khng th trnh khi, c l l do s thoi ha ca m lin kt v do s co c nhanh v nhit cao khi xy ra qu trnh t cng.Hnh 3.8: Mt s enzyme Collagenase3.1.3.4. S phn ct TMAOTrimetylamin l mt amin d bay hi c mi kh chu c trng cho mi thu sn n hng. S c mt ca trimetylamin trong c n hng l do s kh TMAO di tc dng ca vi khun. S gia tng TMA trong thy sn ph thuc ch yu vo hm lng ca TMAO trong nguyn liu c. TMA c dng nh gi cht lng ca c bin. Tin trnh ny b c ch khi c c lm lnh. (CH3)3NO (CH3)3N TMAOVi khunTMATrong c tht ca mt s loi tn ti enzym c kh nng phn hy TMAO thnh dimethylamin (DMA) v formaldehyde (FA). (CH3)3NO (CH3)3NH + HCHO TMAOenzymeDMAFormaldehydeEnzym xc tc qu trnh hnh thnh formaldehyt c gi l TMAO-ase hoc TMAO demethylase, n thng c tm thy trong cc loi c tuyt. c lnh ng formaldehyde c th gy ra s bin tnh protein, lm thay i cu trc v mt kh nng gi nc ca sn phm. S to thnh DMA v formaldehyde l vn quan trng cn quan tm trong sut qu trnh bo qun lnh ng. Tc hnh thnh formaldehyde nhanh nht khi nhit lnh ng cao (lnh ng chm). Ngoi ra, nu c b tc ng c hc qu mc trong cc khu t khi nh bt n khi lm lnh ng v nu nhit trong qu trnh bo qun lnh ng b dao ng th lng formaldehyde hnh thnh s tng.Bng 3.3: Tm tt nhng bin i trong qu trnh t phn gii ca c p lnhEnzymC chtCc bin i xy raNgn chn/Km hm

Enzym phn gii glycogen

Glycogen- To ra acid lactic, lm gim pH ca m, lm mt kh nng gi nc trong c.- Nhit cao khi xy ra t cng c th dn n s nt c tht.- Trn thc t, nu c th nn qu trnh t cng ca c din ra nhit cng gn 0oC cng tt.- Phi trnh gy cng thng cho c giai on trc khi xy ra t cng.

Enzym gy ra t phn gii, lin quan n s ph hy nucleotidATP, ADP, AMP, IMP.- Mt mi c ti, dn dn xut hin v ng do Hx ( nhng giai on sau).- Tng t nh trn.- Bc d vn chuyn mnh tay hoc nn s lm tng s ph hy.

CathepsinCc protein, Cc peptid.- M b mm ha gy kh khn hoc cn tr cho vic ch bin.- Trnh mnh tay khi thao tc lc bo qun v bc d.

Chymotrypsin, trypsin, cacboxypeptidaseCc protein, Cc peptid.T phn gii khoang bng ca cc loi c tng ni (gy hin tng v bng).- Vn s gia tng khi ng lnh/r ng hoc bo qun lnh trong thi gian di.

CalpainCc protein si c- Lm mm m c v gip xc lt xc.- Loi b canxi ngn chn qu trnh hot ha.

Collagenase - S thoi ha ca m lin kt lin quan n thi gian v nhit bo qun lnhM lin kt- Vt nt trn ming phil.- Gy mm ha.- S thoi ha ca m lin kt lin quan n thi gian v nhit bo qun lnh.

TMAO demethylase

TMAO- To ra formaldehyt lm cng c ca h c tuyt khi ng lnh .- Bo qun c nhit 5%, oxymyoglobin c hnh thnh t myoglobin, to cho m c c mu sng v c ch s bin i khng thun nghch ca myoglobin thnh metmyoglobin. S dng nng O2 > 50%, ci thin c mi v ti ca sn phm bao gi.* CO2Vi sinh vt cn CO2 cho qu trnh t trao i cht ca chng. nng CO2 cao (>10%) vi sinh vt b c ch. Kh nng c ch vi sinh vt ph thuc vo loi vi sinh vt, nng CO2 , nhit bo qun, hot ng ca nc trong sn phm. Thay th O2 trong bao gi bo qun s c ch c s pht trin ca vi sinh vt hiu kh. Mt s nghin cu cho thy rng kh nng khng vi sinh vt ca CO2 ch yu ph thuc vo s tc ng qua mng t bo. Cc kin khc cho rng tin trnh tc ng ln mng t bo ch b c ch v cu trc mng t bo khng b ph hy nghim trng. CO2 c nh hng trc tip n h enzym v vy c tc dng c ch s pht trin ca vi sinh vt.3.4.4.2. Vi sinh vt trong bo qun bng phng php MAPMt trong nhng tc dng quan trng nht ca vic ng dng phng php MAP trong bo qun c v cc loi thy sn khc l c ch s h hng do vi sinh vt. V vy s ko di thi gian bo qun.Hot ng khng li vi sinh vt ca CO2 ph thuc vo hot ng ca pha khi u v dng ban u ca vi sinh vt. Ko di giai on u (pha lag) l vn rt quan trng nhm c ch c ch hot ng ca vi sinh vt. Gim tc pht trin sau pha khi u c tc dng ko di thi gian bo qun. Gim nhit s lm gim tc pht trin ca vi sinh vt.CO2 c tc dng chnh trong vic c ch vi khun gram m. y l loi vi khun gy h hng nhit thp. Ngc li vi khun gram dng t b c ch v vi khun lactic t nhy cm nht. Nm mc v nm men cng b c ch.Mi nguy ca s pht trin ca vi khun gy bnh trong MAP c gim n mc thp nht nu dy chuyn ch bin c kim sot cn thn trong iu kin lnh. Vi l do ny, kim tra nhit trong sut qu trnh bo qun, phn phi v tiu th l vn rt quan trng. Vi s hin din ca CO2, s pht trin ca Staphylococcus aureus, Salmonella v Listeria b c ch nhit thp, nhng nhit cao, s pht trin c th xy ra. Bo t Clostridium botulinum pht trin p lc CO2 < 1atm. p lc CO2 > 1atm c ch s hnh thnh bo t v sn sinh c t. p sut cao cng tiu dit t bo sinh dng. Nhm vi sinh vt c bit c ch l vi sinh vt chu lnh Clostridium botulinum nhm B v c bit l nhm E (trong c). Loi vi khun ym kh ny c th pht trin v sinh c t nhit > 3,3oC. iu ny ch ra rng c t c th hnh thnh 10oC trc khi s n hng xut hin.3.4.4.3. ng dng MAP trong bo qun c v cc loi thy sn khcThnh phn hn hp kh s thay i ph thuc vo loi c c bo hay c gy.C gy c th bo qun trong bao gi c cha 65% CO2, 25% N2 v 10% O2. Tuy nhin, c bo khng th bao gi trong hn hp kh c cha O2 bi v phn cht bo ca c rt nhy cm vi O2, chng s b oxy ha to ra cc gc t do. Vi c loi ny nn bo qun trong bao gi vi hn hp kh cha 60% CO2 v 40% N2C bo qun trong mi trng kh quyn iu chnh c th ko di thi gian bo qun ln n 50%, khi nhit bo qun thp.Tuy nhin, CO2 ha tan nhiu trong cht bo v nc hn N2. Tc ha tan tng khi nhit gim. Cc yu t ny lm gim p sut trong bao gi, kt qu lm cho bao gi b h hng (collapse).S ha tan CO2 trn b mt m c c lm gim pH sn phm, dn n lm cho kh nng gi nc ca protein gim.ng dng MAP trong bo qun cc loi nhuyn th c tc dng c ch s to thnh ccm en trn v, khi nhit bo qun t 5 10oC.3.4.4.4. Mt s nhn t quan trng cn ch khi s dng MAP- Ch s dng cho c ti.- m bo nhit c di 2oC trc khi bao gi.- Bao gi trong iu kin lnh v vn chuyn sn phm ng gi n kho bo qun lnh (< 2oC) cng nhanh cng tt sau khi bao gi.- Kim tra hn hp kh s dng trong bao gi c ph hp khng: 65% CO2 + 25% N2 + 10% O2(c gy); 60% CO2 + 40% N2 (c bo).- Kim tra hn hp kh thng xuyn.- Cn phi gi nhit sn phm t 0-2oC trong sut qu trnh vn chuyn v phn phi.- Kim tra nhit d sn phm thung xuyn, phi dao ng trong khong t 0-2oC khi n kho bo qun.

CHNG 4. KT LUN V NGH

4.1. Kt lunVi ngn li thy sn phong ph v di do nh nc ta. Thu sn l mt trong nhng ngnh kinh t mi nhn ca Vit Nam, c gi tr ngoi t xut khu ng hng th 4 trong cc ngnh kinh t quc dn (sau du, go, v hng may mc).Th nhng vi nhng g ti trnh by trong cun bo co n tt nghip ny, mong 1 phn no c th gip ngi c c th hiu r hn v c tnh v bin i cht lng ca nguyn liu thy sn sau khi cht v mt cm quan cng nh v mt cht lng nhm hn ch s bin i n mc thp nht khi n tay ngi tiu dng trong nc v xut khu sang th trng nc ngoi.Qua bi bo co ny, cng gii thiu v c im ca mt s loi thy sn ph bin Vit Nam gip ta hiu hn v chng v t gip ta rt c nhng phng php bo qun v ch bn chng tt hn.4.2. nghThu sn ng vai tr quan trng trong vic cung cp thc phm cho con ngi. Thc phm thu sn c gi tr dinh dng cao rt cn thit cho s pht trin ca con ngi. Vi nhng vai tr ht sc to ln nh trn v nhng thun li, tim nng v cng di do ca Vit Nam c v iu kin t nhin v con ngi, pht trin ngh nui trng, khai thc v ch bin thu sn phc v tiu dng trong nc v xut khu. Nguyn liu hi sn c nh bt t nhiu loi tu v ng c khc nhau do sn phm nh bt c cng c nhng c tnh khc nhau. i vi cc tu i di ngy, sn phm nh bt thng c bo qun bng , c tp th p mui, rt t phng tin c hm bo qun. Cc loi tu nh thng i v trong ngy nn nguyn liu hu nh khng qua x l bo qun .Nguyn liu hi sn thng b xung cp cht lng do phng tin v u t cho khu bo qun cn qu t, qu th s. Sau khi hi sn c nh bt thng qua nhiu bn, cng c cha c xy dng hon chnh do v ma nng cc loi hi sn thng b xung cp nhanh chng, gi tr tht thot sau thu hoch ln.Khi phn phi lu thng nguyn liu phi tri qua nhiu khu trung gian nn cht lng cng b gim st. Phn ln cng c thiu trang thit b, thiu nc sch v nc .Mt s gii php nhm nng cao cht lng thy sn. u t trang thit b hin i hn trong qu trnh ch bin v bo qun ti cc nh my thy sn. Hn ch vn chuyn nguyn liu thy sn qua cc khu trung gian khng cn thit. Trang b y cc vt liu cn thit khi i nh bt xa b: nc , nc sch... Gia tng dng trn bin, cng c v qu trnh vn chuyn gim mt mt v ci thin cht lng sn phm. Hn ch s dng nhng ha cht khng cn thit trong qu trnh ch bin v bo qun. p dng tt cc chng trnh v sinh ti nh my nh: HACCP, SSOP,...

SVTH: T TRUNG HIU 13