ung dung sieu am thuy phan tinh bot

8/3/2019 Ung Dung Sieu Am Thuy Phan Tinh Bot

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ng dng sng siu m trong qu trnh thy phn tinh bt GVHD: ThS. Trn Th Thu Tr

Mc lc

Kt lun ..........................................................................................................45

Ti liu tham kho ..........................................................................................46

Danh mc hnhHnh 1: SEM ca tinh bt t cc ngun khc nhau. .........................................6

Hnh 2: Lin kt Hydro loi I (tri) v loi II (phi)............................................7

Hnh 3: Cu to ca tinh bt ( Tinh bt thc phm, i hc Bch Khoa Nng)................................................................................................................8

Hnh 4: Cu trc ca chui amylose ( John F. Robyt, 2008)..............................9

Hnh 5: Cu trc ca chui amylopectin ( John F. Robyt, 2008).....................10

Hnh 6: Cu trc phn nhnh ca amylopectin (Martin v Smith, 1995)........11

Hnh 7: Cu trc phn lp ca ht tinh bt ( John F. Robyt, 2008).................12

Hnh 8: Cu trc ht tinh bt (vng kt tinh v vng v nh hnh) ( John F.Robyt, 2008)...................................................................................................12

Hnh 9: M hnh phc cht gia amylose v hai phn t monopalmitin (LesCopeland, 2009).............................................................................................15

Hnh 10: S phn loi cc enzyme thy phn tinh bt (Jzef Synowiecki,2007)..............................................................................................................16

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Hnh 11: M hnh m phng hnh thi ht tinh bt trong qu trnh thy phn.......................................................................................................................19

Hnh 12: Quy trnh thc hin thy phn tinh bt............................................20

Hnh 13: Bin i nht theo nhit ........................................................22Hnh 14: Cc mc tn s ca sng m...........................................................24

Hnh 15: Qu trnh hnh thnh, pht trin v v tung ca bt kh..................27

Hnh 16: Hnh nh SEM vi cng chiu (a) 34 W.cm-2 (b) 55 W.cm-2 (c)73 W.cm-2......................................................................................................32

Hnh 17: Hnh nh ht vi cng chiu 34 W.cm-2 trong (a) 15 pht (b) 30pht................................................................................................................32

Hnh 18: Hnh nh ht vi cng chiu 73 W.cm-2 trong (a) 15 pht (b) 30

pht................................................................................................................33Hnh 19: SEM ca ht tng ng mc thy phn 0 , 3.1, 18.4% (QiangHuang, 2007)..................................................................................................35

Hnh 20: nh hng ca sng siu m ln nht biu kin vi s thay inng dch tinh bt (Wenjian Cheng, 2010)................................................36

Hnh 21: nh hng ca sng siu m ln ha tan (Wenjian Cheng, 2010).......................................................................................................................36

Hnh 22: Hnh nh SEM ca h tinh bt khoai m (a) mu kim chng, (b)

nng lng thp (20s), (c) nng lng thp (40s), (d) nng lng cao (20s),(e) nng lng cao (40s) (Nitayavardhana, 2008)..........................................37

Hnh 23: Lng ng kh v nhit gia tng nhng iu kin siu mkhc nhau (Nitayavardhana, 2008)................................................................38

Hnh 24: nh hng ca nng tinh bt ln s thay i nht theo nhit ..................................................................................................................39

Hnh 25: Lng ng kh ca cc mu siu m mc nng lng cao trongvng 30s cc nng cht kh khc nhau.( Saoharit Nitayavardhana,2008)..............................................................................................................40

Hnh 26 : Hiu qu chiu sng siu m cng lc cao vi nng cht khkhc nhau.......................................................................................................40

Hnh 27: Hm lng ng kh sau 3h ng ha vi cc ch x l bngsng siu m khc nhau trong trng hp x l lin tc so snh vi mu ichng l ng chm gch ngang. (Melissa Montalbo-Lomboy, 2010)..........41

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Hnh 28: S h thng thit b chiu siu m lin tc (Melissa Montalbo-Lomboy, 2010)...............................................................................................42

Hnh 29: nh hng ca mt nng lng ca sng siu m n kch thcphn t (Melissa Montalbo-Lomboy, 2010).....................................................43

Hnh 30: Hm lng ng kh v mt nng lng u vo ca phngphp lin tc v gin on (Melissa Montalbo-Lomboy, 2010).......................43

Hnh 31: nh hng ca ch b sung enzyme i vi hm lng ngkh (Saoharit Nitayavardhana).......................................................................43

Hnh 32: Biu m t qu trnh x ht tinh bt c s dng sng siu m(Yasuo Iida, 2007)...........................................................................................44

Danh mc bngBng 1: c im ht tinh bt ca mt s h thng tinh bt (Trn Th Thu

Tr, Cng ngh bo qun v ch bin lng thc, 2007) ................................6Bng 2: Thnh phn ha hc ca mt s loi ht tinh bt ( John F. Robyt,2008)................................................................................................................8

Bng 3: % mch nhnh ca amylopectin t cc loi tinh bt khc nhau( John F. Robyt , 2008)....................................................................................10

Bng 4: Kh nng ha tan trong nc vi 220mg tinh bt trong 10 ml nc.13

Bng 5: Cc tnh cht ca -amylase t cc ngun khc nhau ( Tinh bt thcphm, i hc Bch Khoa Nng)...............................................................17

Bng 6: Cc tnh cht ca - amylase t cc ngun khc nhau ( Tinh btthc phm, i hc Bch Khoa Nng).......................................................18

Bng 7: Cc ng dng ca siu m nng lng cao trong cng nghip thcphm (Patist, Bates, 2008).............................................................................29

Bng 8: nht v ch s ha tan ht tinh bt vi s thay i cc thng s vthit b khi ht trng n v b ph v (Ivana Ljubi Herceg, 2010)...............33

Bng 9: Nhit huyn ph tinh bt sau qu trnh x l bng sng siu m.34

Bng 10: S thay i mc thy phn theo thi gian (Qiang Huang, 2007)

.......................................................................................................................35Bng 11: S thay i ha tan ca cc loi ht tinh bt khc nhau theo thigian................................................................................................................38

Bng 12: S thay i nht ca mt s loi tinh bt bi sng siu m trong30s..................................................................................................................39

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M U

Thc phm chng ta s dng hng ngy a phn do nhiu hp cht cu to nn. N l mth gm nhiu pha cha hn hp phc tp gia nc, polysaccharide, protein, lipid v mt sthnh phn vi lng khc nh khong, vitamin Tinh bt thng hin din trong thc phm vimt t l tng i ln, n cung cp 50 - 70% nng lng cho hot ng hng ngy ca conngi v l ngun cung cp glucose cho no v cc t bo khc trong qu trnh trao i cht. Do c th ni tinh bt nh l mt ngun nguyn liu quan trng c s dng trong cng nghip.Hng nm trn th gii c 60 tn tinh bt thu c t cc loi ht ng cc, r, c, thn v b lca cc loi cy thc vt khc, trong 60% lng tinh bt ny c a vo s dng trongngnh cng nghip thc phm nh trong qu trnh sn xut bnh ko, kem, snack, thc phm chotr em, cng ngh sn xut cc sn phm ln men nh cn, bia, ru, cn li 40% c sdng trong ngnh dc v cc ngnh cng nghip khc nh sn xut giy, nguyn liu bao gi,cht kt dnh, dt, si, vt liu xy dng

Trong nhiu thp k qua, tinh bt tr thnh mt i tng nghin cu ln ca ngnhcng nghip thc phm. c rt nhiu ngin cu v phng php phn tch, cu trc phn t,tnh cht vt l, ha hc, ha sinh, tnh cht chc nng cng nh cc phng thc s dng tinhbt trong tng sn phm thch hp. Thng qua cc phng thc x l tinh bt khc nhau chng tas thu c nhng tnh cht ring cho sn phm thc phm tng ng. Bin php k thut thngs dng nht ch bin tinh bt l tin hnh qu trnh thy phn. Qu trnh ny c thc hindi tc dng xc tc ca acid hay s dng enzyme. V h tr cho qu trnh thy phn nysng siu m c a vo trong quy trnh x l. Phn trnh by sau s gii thch r hn v cch cng nh nh hng ca sng siu m trong qu trnh thy phn tinh bt.

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1. Tinh bt

1.1. Gii thiuTinh bt l ngun carbonhydrate d tr trong r, ht ca cy v c bit cha nhiu trong

ni nh ht ng cc. N cung cp nng lng cho cc qu trnh hot ng ca con ngi (4kcal/g). Bn cnh tinh bt cn c thy phn to thnh ng glucose l ngun c cht chocc loi vi sinh vt thc hin qu trnh ln men to sn phm. Tinh bt l mt i phn t sinhhc c hnh thnh t cc tiu phn l glucose. Ht tinh bt khng tan trong nc lnh do to thnh huyn ph gia tinh bt v nc. Khi ht tinh bt cng hp thu mt lng nc nh

v trng n nh. Sau khi tin hnh gia nhit ht s ht nc mnh hn cho n lc trng ncc i dn n nht t cc i. Chnh nh c tnh ny m tinh bt c s dng nh chtto c trong thc phm. c tnh ca sn phm ph thuc vo nhiu yu t: ngun tinh bt,nng tinh bt, nhit qu trnh gia nhit, tc gia nhit, ha cht s dng (acid, ng,mui,). Vi cc c tnh hu ch ca tinh bt, chng c s dng kh nhiu trong qu trnhsn xut thc phm lm tng nht, ngn cn qu trnh ng t, n nh tnh cht cc snphm lnh ng,Bn cnh ngun tinh bt thng, ngy nay con ngi cn s dng ngun tinhbt bin tnh vi cc c tnh u vit hn gp phn to ra cc sn phm vi cht lng ngy mtcao hn.

1.2. Ngun tinh btTinh bt l polysaccaride ch yu c trong ht, c, thn cy v l cy. Tinh bt c nhiu

trong cc loi cy lng thc do cc loi lng thc c coi l ngun nguyn liu ch yu sn xut tinh bt. Ngun tinh bt rt a dng, trong ph bin nht l t cc ht ng cc nh lam, bp, go, khoai ty, hay t cc loi c nh khoai ty, khoai lang, khoai m Ngoi ra mtlng ng k tinh bt cng c trong cc nhm cy h u nh u nnh, u xanh v trongmt s loi tri cy nh chui,. Tinh bt t cc loi thc vt khc nhau, hay cng mt gingcy trng nhng pht trin di cc iu kin khc nhau th u khc nhau c v hnh thi, tnhcht cng ngh v cc tnh cht chc nng tng ng. Do cn c ch n nhng tnh chtny m bo cht lng n nh v ng nht cho sn phm.

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Hnh 1 : SEM ca tinh bt t cc ngun khc nhau.(a)go ; (b) la m ; (c) khoai ty ; (d) bp (Narpinder Singh, 2002)

1.3. Cu trc ht tinh btTrong thc vt, tinh bt thng c mt di dng ht khng ho tan trong nc lnh gm

nhiu si lin kt vi nhau. Cc carbonhydrate u tin c to ra lc lp do quang hp,nhanh chng c chuyn thnh tinh bt. Tinh bt mc ny c gi l tinh bt ng ho,rt linh ng, c th c s dng ngay trong qu trnh trao i cht hoc c th c chuynho thnh tinh bt d tr trong ht, qu, c, r, thn v b l.. Ty thuc vo ngun gc m tinhbt c kch thc thay i, trong dao ng t 2 150 m. Ht tinh bt c th c dng hnhtrn, hnh bu dc hay hnh a din. Cu to v kch thc ca ht tinh bt ph thuc vo gingcy, iu kin trng trt cng nh qu trnh sinh trng ca cy. C th chia tinh bt thc phmthnh ba h thng:

H thng tinh bt ca cc ht ng cc.

H thng tinh bt ca cc ht h u.

H thng tinh bt ca cc c.

Bng 1 : c im ht tinh bt ca mt s h thng tinh bt (Trn Th Thu Tr, Cng ngh boqun v ch bin lng thc, 2007)

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Loi Hnh dng Kch thc ( m) Nhit h ha (0C)

La m Cu, elip 2 50 53 65

Mch en Elip 12 40 57 70

i mch Elip 2 5 56 62Ng Cu, a din 5 25 62 70

Ng ng Cu, a din - 67 87

Ng np Cu, a din - 63 72

Yn mch a din 5 15 56 62

Go a din 3 8 61 78

Np a din - 55 65

K Cu, a din 4 12 69 75

Cao lng Cu, a din 4 24 69 75

Maurice (1986) m t ht tinh bt gm nhiu vng v nh hnh v vng kt tinh xen knhau. Quan st di nh sng ca quang ph hng ngoi, ngi ta nhn thy c s tn ti lin kthydro gia cc phn t tinh bt, cc lin kt hydro ny ng vai tr quan trng, quyt nh mt stnh cht ca ht tinh bt. Bn trong ht c cc rnh v nh hnh ko di t b mt ti tm tothnh cc l xp. Chnh cc l xp ny gip nc thm nhp lm trng n ht tinh bt, ph vcc lin kt hydro gia cc phn t bn trong ht trong qu trnh thy phn. Khi khng c mtcc phn t nc, tinh bt s lin kt vi nhau theo loi I. Loi lin kt ny lm gim kh nnghot ng ca nhm -OH. Theo kiu lin kt ny, cc nhm -OH b kha cht lm cho hot tnhca chng gim r rt. Thng thng tinh bt tn ti dng ny khi b sy kh qu mc hoc bthoi ha, trong c hai trng hp, nc b tch ra ngoi. Khi trong tinh bt c s hin din ca

nc, cc phn t tinh bt lin kt nhau theo loi II. y l dng lin kt thng thng ca tinhbt trong t nhin, dng ny cc nhm -OH ch yu carbon th 6 nm cnh nhau s lin ktnhau thng qua phn t nc. Bng phng php sy kh thng thng, ta khng th tch honton m ra khi tinh bt, m thng cn li khong 8 -12% m, c gi kh bn trong cu trcphn t tinh bt, nc ny gi l nc lin kt, tng ng vi lng nc to thnh dngmonohydrate (C6H10O5.H2O)n, vi n c th t vi trm n vi triu.

Hnh 2 : Lin kt Hydro loi I (tri) v loi II (phi)

1.4.Thnh phn cu to

Tinh bt khng phi l mt cht ring bit m l mt polymer sinh hc bao gm hai thnhphn chnh l amylose v amylopectin c to thnh t cc n v l glucopyranose lin kt vi

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nhau bng lin kt -D-1,4 glycoside v -D-1,6 glycoside. Hai cht ny khc nhau v nhiutnh cht l hc v ha hc. Da vo s khc nhau c th phn chia c hai thnh phn trn iu ch dng tinh khit. Hu ht tinh bt cha khong 60 90% amylopectin nn t lamylose / amylopectin trong ht thng thy xut hin t l xp x . Trong khi cng c tinh

bt c amylose vi hm lng cao (hn 50% khi lng tinh bt) nh tinh bt u xanh, dongring...v hm lng amylopectin xp x 100% khi lng tinh bt nh tinh bt bp np, gonp...T l ny thay i ph thuc ging loi, thi tit, ma v v cch chm bn. Amylose vamylopectin c cu to cha nhiu nhm hydroxyl do c th kt hp vi nhau (lin kt hydtroloi 1) v vi cc phn t khc (lin kt hydro loi 2) to nn mng li khng gian 3 chiu t to nn nhng tnh cht c trng cho cc sn phm.

Hnh 3 : Cu to ca tinh bt ( Tinh bt thc phm, i hc Bch Khoa Nng)

Ngoi hai thnh phn chnh l amylose v amylopectin th trong ht tinh bt cn cha mt

hm lng nh cc cht khc nh: lipit t 0.1 0.8% khi lng, protein t 0.1 0.4% khilng, phosphate 0.09 0.63% khi lng.

Bng 2 : Thnh phn ha hc ca mt s loi ht tinh bt ( John F. Robyt, 2008)

Tinh bt Amylose (%) Amylopectin (%) Lipid (%) Protein (%) Phosphate (%)

Bp 25 75 0.8 0.35 0.09

Bp np 0 100 0.2 0.25 0.024

Amylomaize-5 53 47 0.7 0.3 0.09

Amylomaize-7 70 30 0.75 0.3 0.06

Khoai ty 22 78 0.01 0.1 0.21

La m 23 77 0.9 0.4 0.18

Go 19 81 0.59 0.3 0.09

Khoai m 17 83 0.02 0.1 0.009

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Chui 20 80 0.48 0.32 0.06

Cu to bn trong ca ht tinh bt kh phc tp. Ht tinh bt c cu to lp, trong mi lpu c ln ln cc amylose v amylopectin xp xp theo phng hng tm. Nh phng phphin vi in t v nhiu x tia X thy rng trong ht tinh bt nguyn thu cc chuipolyglucoside ca amylose v amylopectin to thnh xon c vi su gc glucose mt vng.Trong tinh bt ca cc ht ng cc, cc phn t c chiu di t 0,35-0,7 m, chiu dy ca mtlp ht tinh bt l 0,1 m. Hn na, cc phn t li xp xp theo hng tm nn cc mchglucoside ca cc polysaccaride c dng gp khc nhiu ln. Cc mch polysaccharide sp xphng tm to ra vng tinh th: cc mch bn ca mt phn t amylopectin ny nm xen k giacc mch bn ca phn t kia. Ngoi cch sp xp bn trong nh vy, mi ht tinh bt cn c vbao pha ngoi. a s cc nh nghin cu chng t rng v ht tinh bt khc vi tinh bt bntrong ch l cha t m hn v bn i vi cc tc ng bn ngoi. Trong ht tinh bt c l xp

nhng khng u. V ht tinh bt cng c l nh do cc cht ha tan c th xm nhp vo bntrong bng con ng khuch tn.

1.4.1. Amylose

Hnh 4 : Cu trc ca chui amylose ( John F. Robyt, 2008)

Amylose c khi lng phn t xp x 105 106 g, chui di t 500 - 2000 n v glucose.Amylose nguyn thy c mc trng hp khng phi hng trm m l hng ngn. C hai loiamylose:

Amylose c mc trng hp tng i thp ( khong 2000) thng khng c cu trcbt thng v b phn ly hon ton bi -amylase.

Amylose c mc trng hp ln hn, chiu di mch di hn v cu trc xon phc tphn do kh tip xc vi trung tm hot ng ca -amylase nn ch b phn hykhong 60%.

Phn t amylose c cu to mch thng, gm nhng n v glucose lin kt vi nhau bnglin kt -1,4 glycoside trong c khong 0.5% s phn t glucose lin kt vi nhau bng lin

kt -1,6 glycoside. Amylose thng c dng cun xon c, ng knh ca xon c l 12.97A0

,chiu cao ca vng xon l 7.91A0, mi vng xon c 6 n v glucose. Cc nhm hydroxyl cacc gc glucose c b tr pha ngoi xon c, bn trong l cc nhm C-H. Khi tng tc viiod, amylose s cho phc mu xanh c trng. Khi phn t iod c sp xp bn trong cutrc xon c ca phn t amylose. Amylose d ha tan trong nc m to thnh dung dch c nht khng cao. Khi nhit dung dch h thp, amylose d b thoi ha v to ra cc kt takhng thun nghch.

1.4.2. Amylopectin

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Hnh 5 : Cu trc ca chui amylopectin ( John F. Robyt, 2008)

Cu to ca amylopectin ln v c t l phn nhnh kh ln. Khi lng amylopectinkhong 108 vC v DP ln hn 1 triu.Amylopectin l polyme mch nhnh, ngoi mch chnh clin kt -1,4 glycoside cn c nhnh lin kt vi mch chnh bng lin kt -1,6 glycoside.Amylosepectin c khong 5% s lng phn t glucose lin kt bng lin kt bng -1,6glycoside.

Bng 3 : % mch nhnh ca amylopectin t cc loi tinh bt khc nhau ( John F. Robyt , 2008)Amylopectin % mch nhnh

Ng 4.2

Khoai ty 4.5

La m 4.8

i mch 5

Yn mch 5.2

Ng np 5.9

Mch nhnh ca amylopectin c th c chia lm 3 phn:

Loi A: khng c nhnh, mt u ca mch A lin kt vi cc mch khc bng linkt - 1,6

Loi B: dng mch nhnh do mt hay nhiu mch A ni vo.

Loi C: mch duy nht trong phn t amylopectin c mang gc glucose c nhmkh.

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Hnh 6 : Cu trc phn nhnh ca amylopectin (Martin v Smith, 1995)

Mi lin kt nhnh ny lm cho phn t cng knh hn, chiu di ca chui mch nhnhny khong 25-30 n v glucose. Phn ng gia amylopectin v iod cho phc mu nu tm.Amylopectin ch ha tan trong nc nng v to dung dch c nht cao. Do cu trc cngknh lp th nn cc phn t amylopectin trong dung dch khng c khuynh hng kt tinh linn thng khng b hin tng thoi ha. S khc bit gia amylose v amylopectin khng philun lun r nt bi l cc phn t amylose cng thng c mt phn nh phn nhnh do cng c nhng tnh cht gn ging nh amylopectin. S khc nhau ny c gii thch l do skhc nhau trong qu trnh sinh tng hp tinh bt di tc dng ca nhiu loi enzyme khc nhau.

1.5. Nhng tnh cht ca tinh bt1.5.1. c tnh cu trc ca ht tinh bt

T l vng kt tinh ca ht tinh bt l 15% i vi ht giu amylose v khong 45 50% ivi ht tinh bt np. Ht tinh bt c cu trc c sp xp theo mt trt t xc nh ty loi ht.Cu trc bn trong ca ht gm nhng lp vi cc vng trn ng tm c sp xp theo th tkch thc tng dn t tm n b mt ht, c dy tng t 120 400 nm ln lt cha ccvng kt tinh v v nh hnh vi mc tng dn vng kt tinh v gim dn vng v nh hnh

tng ng.

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Hnh 7 : Cu trc phn lp ca ht tinh bt ( John F. Robyt, 2008)

Vng tinh th c hnh thnh chnh bi mch amylopectin gc cn vng v nh hnhc hnh thnh t cc nhnh ca phn t amylopectin, amylose v cu trc amylopectin sp xpkhng trt t.

Hnh 8 : Cu trc ht tinh bt (vng kt tinh v vng v nh hnh) ( John F. Robyt, 2008)i vi ht c hm lng amylose cao, mch xon c ca amylose cng c th gp phn

vo qu trnh kt tinh ca ht to nn cu trc bn tinh th vi tnh cht lng chit (khc x kp)khi c quan st di knh hin vi nh sng phn cc. Cc tinh th to bi mch amylopectinc phn thnh 2 loi: loi A vi cu trc cht ch hn loi B. Vic sinh tng hp tinh th loiA v loi B khc nhau trong sut qu trnh hnh thnh ht t dn n s khc nhau v cu trcphn t amylopectin v t l amylose/amylopectin trong ht. Tinh th loi B c cu trc mchamylopectin ngn hn. Cc ht tinh bt ng cc c khuynh hng c nhiu tinch th loi A trongkhi tinh bt t cc cy thn c v cc ht tinh bt giu amylose cha nhiu cu trc loi B

hn. Bn cnh cn xut hin mt dng trung gian gia loi A v loi B l tinh th loi C.Loi tinh th th ny xut hin nhiu mt vi loi tri, thn cy. Thng trong ht xut hin chai loi tinh th trn nhng vi t l khc nhau ty ngun gc cng nh iu kin trng trt. V di vi ht tinh bt la m tinh th loi A chim t l cao hn nhng c s lng t hn ht loi B.Do dn n s khc nhau trong cu trc v tnh cht chc nng ca sn phm sau ny.

Amylose c kh nng to phc vi iod to thnh phc amylose iod, do chng tathng s dng phng php ny xc nh amylose trong ht. Mc d phng php nynhanh v thun tin nhng n khng cho kt qu chnh xc bi v bc sng hp thu cc i ca

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phc amylose iod khc nhau ph thuc vo DP. Bn cnh amylopectin cng c th to thnhphc vi iod to thnh phc amylopectin iod v cng c th b hp thu bc sng ny.Phng php quang ph cng l mt phng php hiu qu thay th cho phng php nynhng b hn ch ch khng th s dng vi s lng ln. Do , vic kt hp cc k thut

phn tch xc nh s sp xp, t chc cc phn t trong ht, c lng dy vng tinh thv s nh hng ca amylose i vi amylopectin trong ht tinh bt nguyn thy. Hin nay c rtnhiu phng php phn tch xc nh cu trc tinh bt nh l k thut nhiu x ( xc nh skt tinh ca nguyn liu), phng php o gc phn tn ( xc nh s phn b mt electron),phng php o nhit lng ( DSC) xc nh kh nng ha tan, kt tinh v nhit chuyn itinh th. Cc k thut hnh nh nh knh hin vi quang hc, knh hin vi in t qut, knh hin vinguyn t, phng php quang ph cng c s dng rng ri nhn bit hnh dng v cutrc ht tinh bt.

1.5.2. Tnh trng n v h ha ca ht tinh btPhn ln ht tinh bt b h ha khi nu v trng thi trng n c s dng nhiu hn

trng thi t nhin. Cc bin i ha l khi h ha nh sau: ht tinh bt trng ln, tng trong

sut v nht, cc phn t mch thng v nh th ha tan v sau t lin hp vi nhau tothnh gel. nhit bnh thng, tinh bt khng ha tan trong nc, tinh bt cng khng hatan trong ether, ancohol, sunfua carbon Khi ngm ht tinh bt trong nc nhit thng, tanhn thy c s tng th tch ca tinh bt l do nc c hp th vo trong, lm ht tinh bttrng phng ln, y chnh l hin tng trng n ca ht tinh bt. Kh nng trng n caht trong nc tng khi nhit tng v n mt lc no to thnh dung dch keo gi l htinh bt. Khi tinh bt c gia nhit vi s tham gia ca nc hay s dng phng php hp sdng autoclave hay trn tinh bt vi nc c nhit 1000C, cu trc ht b ph v v lc nynhm OH ca nc to lin kt hydro vi vi nhm OH ca phn t amylose v amylopectin.iu ny lm tng kh nng ha tan v trng n ca ht. Trong cc loi ht, tinh bt khoai ty lc trng n v kh nng ha tan ln nht v gi tr nh nht tinh bt la m.

Bng 4 : Kh nng ha tan trong nc vi 220mg tinh bt trong 10 ml nc

bng bin php hp bng autoclave nhit 1210C trong 20 pht ( John F. Robyt, 2008)

Tinh bt ha tan (mg/ml)

Ng np 18.7

Khoai m 17.4

Khoai ty 12.4

Ng 12.4

Go 7.9

Amylomize-7 5.5

La m 5.2

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Lc trng n cao bp np, khoai m, khoai ty c gii thch l do c cha hm lngcao cc nhm phosphate thng gn cui mch phn t amylose (bao gm monoeste phosphatev phospholipid), lc y gia cc nhm phosphate cc mch lin k s lm tng s kt hpnc do lm yu mc lin kt trong vng kt tinh. Ngoi thnh phn cc hp cht phospho

nh hng n trng n ca tinh bt th s hin din ca lipid trong ht cng nh hng nkh nng trng n. Kt qu n lm gim kh nng trng n ca ht. Nguyn nhn l do lipidtham gia to phc vi amylose lm cu trc tinh th cng cht ch hn nn lm gim s xmnhp ca nc vo trong ht. trng thi t nhin, tinh bt khng b ha tan trong nc lnh ldo nng lng tng tc phn t trong iu kin vt xa nng lng hydrat ha. Khi hp thnc, tinh bt trng n dn, 25 50% ht tinh bt vn cha b trng, khi tng nhit nmt gii hn no , cc ht trng n mt cch nhanh chng, hnh dng ht s thay i t ngtn thi im b ph v hon ton to thnh dng keo dnh. Kh nng trng n ca cc ht tinhbt t cc ngun khc nhau s khc nhau ty vo thnh phn ha hc (t l amylose/amylopectin,hm lng nhm phosphate), kch thc ht, chiu di nhnh, s sp xp trt t cc ht... Vd bp v la m c th trng n n th tch ln gp 30 ln th tch ht ban u m khng b r

ra. Vic tng kh nng trng n hay tnh tan ca ht dn n vic lm tng trong ca huynph tinh bt nc. Hin tng trng n ny xy ra trc tin cc khe lm ca ht tinh bt,sau lan rng c b mt, lm cho th tch ca chng tng ln nhiu ln cho n khi ht b rchv tr thnh ci ti khng nh hnh, hoc ngng tng th tch, lc tinh bt bt u h ha,nhit tng ng lc ny tinh bt trng n v gii phng cc si amylose v amylopectinc gi l nhit h ha. Nhit h ha khng phi l mt im m l mt khong nhit nht nh. Ty iu kin h ha nh nhit , ngun gc tinh bt, kch thc ht v pH m nhit ph v v trng n ca tinh bt bin i mt cch ng k. Da vo thuyt ca Jenkins vDonald, nc u tin vo vng v nh hnh trc, khi n s trng n mt mc nhtnh, di tc dng ca p lc ph v, nc s di chuyn t vng v nh hnh n vng kt tinh.Nhit h ha ca hu ht tinh bt nm trong khong 60 80 0C. Thng qua nht ca h tinhbt chng ta c th nh gi c mc h ha ca ht.

1.5.3. nht ca h tinh btMt trong nhng tnh cht quan trng ca tinh bt, nh hng n cht lng v kt cu ca

nhiu sn phm thc phm, l nht v do. Phn t tinh bt c nhiu nhm hydroxyl, ckh nng lin kt c vi nhau lm cho cc phn t tinh bt tp hp li, gi nhiu nc hn,khin dung dch c c, dnh, do v nht cao hn. Yu t chnh nh hng n nht ca dung dch tinh bt l ng knh biu kin ca cc phn t hoc ca cc ht phn tn,c cu trc phn t tinh bt nh kch thc, th tch, v s bt i xng. Nng tinh bt, pH,nhit , tc nhn oxi ha, cc ha cht ph hy lin kt hydro u lm cho tng tc ca ccphn t tinh bt thay i do lm thay i nht ca dung dch tinh bt. nht thay i lintc trong sut qu trnh thy phn tinh bt: gi tr s tng n cc i sau gim dn giai ondch ha v ng ha do s gy ca cc phn t amylose v amylopectin. S thay i ny phthuc vo qu trnh x l ht. xc nh nht ngi ta thng s dng thit b phn tch nht Rapid Visco Analyser ( RVA), thng qua gip cho vic iu chnh lc x, nn cng nhdng qu trnh khi t nht xc nh. RVA l mt thit b thun tin nghin cu nhhng ca ph gia to nn tnh cht lu bin ca sn phm. Cc thng s do RVA a ra c thgip d on kt cu v cht lng sn phm.

1.5.4. Kh nng to gel v s thoi ha gelTinh bt sau khi h ha v ngui, cc phn t s tng tc nhau v sp xp li mt cch

c trt t to thnh gel tinh bt vi cu trc mng khng gian 3 chiu. to c gel th

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dung dch tinh bt phi c nng m c va phi, phi c h ha chuyn tinh bt thnhtrng thi ha tan v sau c ngui trng thi yn tnh. Trong gel tinh bt ch c cc linkt hydro tham gia, c th ni trc tip gia cc mch amylose v amylopectin hoc c nigin tip qua phn t nc.

Khi gel tinh bt ngui mt thi gian di s co li, cc phn t amylose c th b tchnc v lin kt li vi nhau thng qua lin kt hydro, qu trnh ny gi l qu trnh thoi ha.Trong sut qu trnh thoi ha, cc mch xon amylose lin kt li vi nhau gia 40 70 n vglucose. Kt qu amylose s tch lp lng xung. Qu trnh thoi ha din ra mnh trong h tinhbt t nhin giu amylose. Hm lng amylose c xem l mt trong nhng nhn t nh hngln n qu trnh thoi ha. Amylose c chiu di mch cng ln th mc thoi ha cng tng.Qu trnh ny s cng tng mnh nu gel lnh ng ri sau cho r ng. i vi tinh btgiu amylopectin th thng khng xy ra hin tng thoi ha do cu trc cng knh kh li gn kt li vi nhau. Cc loi ht khc nhau th c mc thoi ha khc nhau v d nh tinh btkhoai ty c mc thoi ho cao hn so vi go, bp, la m. Do cn c ch x l ph hpcho tng loi sn phm tinh bt c th trnh xy ra hin tng thoi ha lm nh hng n

tnh cht cng ngh sn phm.1.5.5. Qu trnh to phc gia tinh bt v lipid

Trong ht tinh bt ngoi cc thnh phn chnh l amylose v amylopectin cn tn ti mtlng nh khong 1% cc cht bo nh acid bo, lisophospholipids v monoacylglycerides c thlm thay i c tnh v tnh cht chc nng ca tinh bt. S to phc gia tinh bt v lipid mch yu l amylose vi hm lng khong 15 45% khi lng amylose trong ht lm gim khnng ha tan ca tinh bt trong nc, thay i tnh cht lu bin ca h tinh bt, gim kh nngtrng n, tng nhit h ha, gim bn vng ca gel ng thi lm gim qu trnh thoiha ca ht tinh bt. Phc ny c ng dng kh ph bin trong thc phm: lm gim nhtthc phm t tinh bt, tng s n nh khi r ng thc phm lnh ng, cht n nh bt nho v

lm mm trong bnh m, thay th cht bo v l cht to c trong thc phm...Cc acid bo ckhuynh hng lin kt mch xon ca amylose v thng nm cui mch phn t amylose.

Hnh 9 : M hnh phc cht gia amylose v hai phn t monopalmitin (Les Copeland, 2009)

2. Qu trnh thy phn tinh bt

2.1. Gii thiu

Qu trnh thy phn l qu trnh xy ra di tc dng ca cc phn t nc tham gia phnng ct t mch cc phn t c kch thc ln. Trc y qu trnh thy phn tinh bt s dng

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xc tc acid. Xc tc ny i hi nhiu nng lng hn cho qu trnh gia nhit v kh khn trongkim sot. Hin nay thng s dng xc tc l enzyme bi yu cu gi li mu sc v cc thnhphn trong nguyn liu do ch x l nh nhng hn qu trnh thy phn bng acid. Trong httinh bt, do c cc vng kt tinh nn gy kh khn cho enzyme trong qu trnh thy phn bi v

cu trc lin kt cht ch nn enzyme kh xm nhp. Hu ht cc enzyme u c hiu cho linkt -1,4 glycoside, nhng thy phn hon ton tinh bt cn phi ct ht cc lin kt -1,6glycoside ny. Do c th b sung cc enzyme ct c hiu cho lin kt -1,6 glycoside.

2.2.Enzyme thy phn tinh bt

Enzyme ch thy phn hiu qu tinh bt khi tip xc trc tip vi phn t tinh bt hay nicch khc l tinh bt c ha tan mt phn. Mt s enzym thng dng l -amylase, -amylase, glucoamylase a phn cc enzyme u thy phn c hiu cc phn t tinh bt. ctrng ca phn ng thy phn l s gim nhanh nht dung dch v sinh ra cc dextrin phn tlng nh. S xm nhp ca nc, enzyme vo ht tinh bt u tin xy ra vng v nh hnh.u tin emzyme tn cng vo b mt ht hnh thnh nhng l nh, cc l ny to dn v hnh

thnh knh dn, knh ny dn n tm ht dn n s ph v ton b ht. Cc enzyme thy phnc chia thnh hai nhm ln l exo- v endo- enzyme. Exo- enzyme thng tc dng vo phnt v tr u mch ca u khng kh. Endo- enzyme tc ng vo v tr gia mch ca ccphn t nn lm cho nht dung dch gm nhanh hn.

Hnh 10 : S phn loi cc enzyme thy phn tinh bt (Jzef Synowiecki, 2007)

2.2.1. Nhm enzyme c hiu vi lin kt - 1,4 glycoside

Enzyme - amylase (EC.3.2.1.1)

Enzym - amylase l protein phn t lng thp, thng nm trong khong 50000 n60000vC. Cc nh nghin cu cho thy hu ht cc chui mch axit amin ca enzym -

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amylase u c cu trc bc 3 tng t nhau. Enzyme - amylase c th c ngun gc t thcvt (mm ht ny mm), ng vt (tuyn ty ca heo, b) hay t vi sinh vt (vi khun v nmmc). Trong ngun cung cp - amylase thng s dng l t vi sinh vt do c kh nngchu nhit cao. Hiu qu thy phn cao nht l - amylase thu c tuyn ty heo, k n l

- amylase t mm ht ny mm v cui cng l t vi khun v nm mc. Enzyme -amylase tc ng ch yu ln lin kt -1,4 glycoside v tr gia mch nn lm gim nhanh nht do cn c gi l enzyme dch ha. Khi - amylase tip xc ht tinh bt v tin hnhthy phn ht tinh bt s to ra cc sn phm chnh l dextrin thng c t 2 7 n v glucose.Cch thc tc dng ca - amylase ph thuc ngun gc enzym v bn cht ca c cht.

Mt iu hay nhm ln l - amylase ct ngu nhin vo mch tinh bt nhng thc chtn c tnh cht ct c hiu. Tnh cht ct ny ph thuc vo ngun gc enzyme m s c tnhc trng ring cho tng loi. pH ti u ca - amylase ph thuc vo ngun gc enzyme. Nichung, pH ti u nm trong khong axit yu 4,8 - 6,9. Tuy nhin c mt s - amylase chu axitcao nh - amylase t Bacillus acidocaldarious (pH ti u 3,5) v chu kim mnh nh -

amylase t Bacillus licheniformis ( pH ti u 9,0). S c mt ca ion canxi cho php ci thin n nh ca enzyme i vi s thay i ca pH. Nhit hot ng ti u ca - amylasecng ph thuc vo ngun gc enzyme. Ni chung nhit ti u nm trong khong 40-500C,nhng c th t ti gi tr gn 70-800C i vi -amylase t vi khun nhB. sterothermophilus,B. subtilis, B. licheniformis.

Bng 5 : Cc tnh cht ca -amylase t cc ngun khc nhau ( Tinh bt thc phm, i hcBch Khoa Nng)

Enzyme - amylase (EC.3.2.1.2)

Nhng hiu bit v - amylase cn rt hn ch. Ch c cc enzyme c ngun gc thc vtc bit n nhiu nht. Cc enzyme ny c sinh tng hp trong cc ht di dng timn, sau c hot ha trong qu trnh ny mm nh enzyme protease. Gn y ngi ta tchchit c - amylase t vi khun nh Bacillus pseudomonas, B. streptomices. Enzyme -amylase c to ra t mt chui mch polypeptide duy nht, c khi lng phn t 60000 vC.Cc enzym - amylase c pH ti u nm trong khong 5 - 6 v nhit ti u khong 50 0C. Tuy

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nhin cc - amylase vi khun thng c tnh bn nhit hn so vi - amylase c ngun gcthc vt.

Bng 6 : Cc tnh cht ca - amylase t cc ngun khc nhau ( Tinh bt thc phm, i hcBch Khoa Nng)

C ch tc ng ca amylase ch yu vo cc lin kt - 1,4 glycoside t u khng

kh ca mch gii phng ra ch yu cc phn t maltose. Tc ng ca enzyme s ngng li ch st vi lin kt - 1,6 glycoside. Amylose gn nh b thy phn hon ton trong khi ,trong cng iu kin th ch c 55% amylopectin c chuyn thnh - maltose. Phn cn lica s thy phn amylopectin l dextrin c phn t lng nh hn v c cha tt c cc lin kt- 1,6 glycoside ca phn t ban u.

2.2.2. Nhm enzyme c hiu vi lin kt - 1,6 glycoside

Pullulanase (EC.3.2.1.41)

Enzyme ny c th thy phn cc lin kt - 1,6 glycoside ca tinh bt, glycogen, pullulanv cc dextrin. iu ng ch l s nh v ca lin kt - 1,6 glycoside c nh hng ln n

tc ng ca enzym. c bit s c mt ca hai lin kt - 1,4 glycoside nm k bn lin kt -1,6 glycoside l iu kin cn thit cho enzyme phn ct lin kt ny.

Isoamylase (EC.3.2.1.68)

Enzyme ny khng c kh nng thy phn pullulan v khng th ct t lin kt - 1,6glycoside ca cc phn t cha t hn ba lin kt - 1,4 glycoside.

2.2.3. Nhm enzyme c hiu vi lin kt - 1,4 glycoside v - 1,6 glycoside

Amyloglucosidase (EC.3.2.1.3)

Amyloglucosidase t nm mc l cc protein c khi lng phn t dao ng ln t 27000n 112000 vC ty thuc vo ngun gc ca enzym. Tnh cht ca amyloglucosidase ph thucvo ngun gc ca enzyme. Hot ng ti u ca enzyme nm trong khong pH 4,5-5,5 v nhit 40-600C. S c mt ca cc oligosaccharide trong mi trng c tc dng n nh enzyme.Ngc li s c mt ca ion canxi km hm v lm bin tnh enzyme. Enzyme ny c xem lenzyme duy nht c kh nng chuyn ha hon ton tinh bt thnh glucose.

2.3. Qu trnh thy phn tinh bt

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C 3 giai on trong qu trnh thy phn tinh bt: h ha, dch ha v ng ha. Qu trnh hha l qu trnh cc ht trng n km theo s gii phng cc cc si amylose v amylopectindi tc dng xc tc ca -amylase. Trong qu trnh h ha, nht dch tng dn v khi qutrnh kt thc nht dch s t gi tr cc i. Sau cc si amylose v amylopectin tip tc

c gii phng trong qu trnh dch ha v sau s b ct ngn to thnh cc dextrin phn tlng nh. Kt qu nht ca dch gim xung. Qu trnh ng ha l qu trnh ct ngn ccphn t dextrin phn t lng nh to ra sn phm l cc loi ng n gin nh glucose,maltosedi tc dng xc tc ca enzyme glucoamylase. nht ca dch khi ny c xeml c gi tr thp nht.

Hnh 11 : M hnh m phng hnh thi ht tinh bt trong qu trnh thy phn

v s bin i nht.

Nhng cng ty khc nhau c phng php h ha tinh bt khc nhau nhng trn nguyn

tc l ging nhau. Sau y l mt v d c th v quy trnh x l ca mt s cng ty hin nay.

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Hnh 12 : Quy trnh thc hin thy phn tinh bt

u tin tinh bt s c trn vi nc theo t l 30-40% (w/w) pH 6.0-6.5, 20-80 ppmCa2+ (n nh v hot ha hot tnh ca enzyme -amylase). T l ny c th thay i ty loitinh bt s dng (ph thuc vo quy trnh x l ca tng sn phm tinh bt). Sau -amylasec b sung vo thc hin qu trnh h ha. Khi mi trng phi iu kin thch hpcho enzyme xc tc. Thi gian lu trong jet cooker rt ngn, mt phn tinh bt h ha s ca qua h thng ng duy tr nhit 100-1050C trong khong 5 pht qu trnh h ha xy rahon ton. Sau qu trnh thy phn tip tc vi qu trnh dch ha trong thng cha nhit

90-1000

C v kt thc sau 1 2 gi. Cui cng nhit s c h v 550

C thc hin tip qutrnh ng ha, qu trnh ny s ko di cho n lc dch thy phn t n DE cui theo yucu. Tinh bt sau qu trnh dch ha thng c a qua qu trnh ng ha nhng mt phnnh c th c sy phun to thnh maltodextrin. Trong trng hp ny th chng ta phi cch enzyme bng cch gim pH (xung gi tr thp hn gi tr ti thch ca enzyme) khi kt thcqu trnh x l nhit.

2.3.1. S h ha tinh bt

Ht tinh bt khng tan trong nc lnh nhng c xu hng trng n trong nc phthuc vo kiu v thnh phn cu to trong ht tinh bt. Ti nhit thng v pH trong khong4 10, ht tinh bt t nhin khng tan m ch hp th nc khong 30% khi lng ca n. Hnhp thu c gi l huyn ph tinh bt. Tht ra, nhit ny, mt s phn t nc chuic vo bn trong cu trc ca ht tinh bt nhng vi s lng khng nhiu. Nc hp th vov lm ht trng n khong 5% th tch. Di nhit h ha, xy ra qu trnh ht nc vtrng n thun nghch. Khi c un nng, nhit nng cung cp s ph v hng lot lin kthydro rng buc cc phn t nc, gip cc phn t nc ny tr nn linh ng hn, d dng tncng vo cu trc micelle ca ht tinh bt, dn n xy ra qu trnh hydrat ha. Khi cc phnt nc s chuyn ng nhanh hn v c nhiu phn t khuch tn vo bn trong ca ht tinhbt. Do , ht tinh bt s trng n ng k, tng th tch v kch thc. Di tc dng canhit, mt s phn t amylose v v amylopectin phn t lng nh s khuch tn vo mi

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trng xung quanh. Cc phn t tinh bt ny s b hydrate ha to thnh cc micelle nh. Ccmicelle ny v cc ht tinh bt trng n s kt hp li vi nhau bng lin kt hydro, hnhthnh cc lin kt ba chiu mi, lm nht tng ln. Khi nhit tng, ng knh ht tng nkhi lp ngoi ca ht b ph v, lc ny hn hp t nh nht. S gia tng nht cui ca mu

h ha gia nhit c cho l gii phng cc si (ch yu l amylose) v on nhnh (s bindng) ca ht tinh bt trng n. Do , h tinh bt l mt dung dch bao gm cc ht trng n l lng trong nc nng, cc phn t amylose cng b phn tn trong ny. Nhng tcng qua li trong dung dch khi ny lin quan n lin kt hydro ni phn t gia cc ht tinhbt vi nhau v gia cc ht tinh bt vi nc(Tako v Hizukuri, 1999).

Tm li qu trnh h ha c nh ngha l s t gy khng thun nghch trong cu trccc phn t ht tinh bt khi c gia nhit vi lng nc ly d (Sivak v Preiss, 1998). Do xy ra cc hin tng l chuyn t huyn ph sang dng dung dch keo, v t dng dung dch keochuyn sang dng gel (Gomi v cng s, 1998; Chatakanonda v cng s, 2000) cng nh s phhy cu trc lin kt trong mng (Hsu v cng s, 2000). Vng c h ha u tin l cc vngv nh hnh, ti lin kt hydro yu hn nhng vng c cu trc tinh th, do vy lin kt hydro

gia cc phn t tinh bt vng d b phn hy, gip cho hin tng hydrat ha d dng hn.Mt khc, nhit cao cng ph hy cc lin kt hydro gia cc phn t tinh bt, gip cc phnt nc d dng hydrat ha. Trong qu trnh h ha, mt s phn t tinh bt b hydrat ha mnhm s tch khi mng li micelle, khuch tn vo mi trng nc gy nn hin tng ha tantinh bt vo nc nng.

Thng thng, cu trc mng li micelle khng n nh, ngoi ra kch thc ca htcng khng n nh, nn qu trnh h ha khng xy ra mt nhit nht nh, m dao ngtrong mt khong nhit ty vo vic cung cp thm nng lng cho s ph v lin kt nhng vng c cu trc cht ch trong mng li micelle to nn lin kt mi gia tinh bt vnc. Qu trnh h ha cc loi tinh bt thng xy ra nhit nh hn nhit si ca nc.Nu sau khi h ha xong m qu trnh gia nhit vn ko di cho n nhit si, th nng lngc cung cp tha do gia nhit li tip tc ph hy lin kt hydro va mi to ra gia phn tnc v cc nhm -OH ca tinh bt, lm cho kt cu ca tinh bt h ha tr nn lng lo,gim nht v do ca h tinh bt.

Nhit h ha ca cc ngun tinh bt khc nhau th khc nhau. Tinh bt khoai m cnhit h ha trong khong 58.5 700C, so vi 56 660C khoai ty v 62 720C tinh btbp. Cc dn xut ca tinh bt c to ra nh cc lin kt ngang hay khi thm cc cht c hottnh b mt c th lm thay i nhit h ha. Nhit h ha cng nh hng n cht lngnu ca tinh bt, nhit h ha thp thng c cht lng nu thp do tinh bt d b ph v.Nng huyn ph tinh bt, tc un nng, m ban u ca tinh bt u c nh hng nnhit h ha. Khi tng nng huyn ph tinh bt th nhit h ha gim. Nhit h haph thuc nhiu vo kch thc ht tinh bt, kch thc ht nh th c nhit h ha cao hn so

vi tinh bt cha ht c kch thc ln.Nh vy nhit h ha v kh nng h ha ca mt loi tinh bt no s ph thuc rt

ln vo cu trc ca mng li micelle trong ht tinh bt, cu trc ny c c trng bi hnhdng, kch thc phn t, khi lng phn t, t l gia amylose v amylopectin, mc phnnhnh v chiu di ca nhnh amylopectin. Ngoi ra nhit h ha cn ph thuc vo tnh chtl ha ca cht khuch tn v mi trng khuch tn. Biliaderis v Tonogai (1991) nghin cunhng nh hng khi cc ht tinh bt lin kt vi lipid vo nhng c tnh nhit, nht, do cagel tinh bt v nhn thy vic thm cc lysophospholipid lm gim enthalpy h ha ca tinh bt

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cng vi s gia tng v nhit ti im chuyn i amylose lipid xy ra. Nguyn nhn l docc lipid to phc vi amylose trn b mt ht do ngn cn s xm nhp cc phn t nc vht tinh bt lm hn ch qu trnh trng n ca ht.

Garcia, V. v cng s (1997) nghin cu nhng thay i v cu trc ca ht tinh bt

sau khi gia nhit trong nc vi hm lng nc khc nhau. Hnh nh hin vi quang hc cho thyht khi b gia nhit di nhit bt u hp thu nhit (T o) khng lm nh hng n ht. Saukhi gia nhit n cc nhit khc nhau, hnh nh hin vi quang hc cho thy, tng ng vihm lng nc khc nhau trong sut qu trnh, c 4 hnh thi ring bit trong tp hp ht: htnguyn, ht b mt mt phn tnh lng chit, ht khng c tnh lng chit nhng cn dng hnhcu v ht khng cn nguyn vn. S thay i cng r rng khi thc hin qu trnh gia nhit vihm lng nc v nhit cao hn.

Hnh 13 : Bin i nht theo nhit

y chng ta cn phn bit s h ha v qu trnh hydrat ha ca ht tinh bt. Qu trnhhydrat ha l qu trnh ht tinh bt ht nc lm ht trng n dn n tng nht ca hn hp,cn s h ha ch mc hp thu nc ti a lm ht trng n cc i dn n nht t cci. Mc trng n s ph thuc vo cu trc bn trong ca ht. Cu trc phn t bn trongcng cng, nhit cho qu trnh h ha cng cao. Trong qu trnh h ha chng ta cn quan tmti hin tng h tinh bt sau khi gia nhit v c lm ngui, cc phn t amylose s tch ra, tikt hp v hp nht vi cc ht tinh bt trng n theo mt cu trc c th t lm cho nhttng ln (Lai v cng s, 2000). Hin tng ny c xem nh l qu trnh kt tinh hoc ti kt

tinh (ngha l s hnh thnh v s kt hp ca hai on xon c) ca amylose (Seow v cng s,1996).

2.3.2. Dch ha v ng ha

Sau giai on h ha ht tinh bt trng n nhng vn cn nguyn vn. Khi ta tip tc gianhit hn hp, s chuyn ng hn lon ca cc phn t tinh bt trong hn hp di tc dng canhit s lm cho lin kt gia cc phn t tinh bt vi nhau, gia tinh bt vi nc tr nnlng lo. Kt qu l cc phn t amylose v amylopectin c gii phng t dng lin kt trong

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cu trc ht tinh bt sang dng t do. Qu trnh ny c gi l qu trnh dch ha. Sn phmto thnh ca qu ng ha l maltodextrin, cc oligosacarit, ng glucose, maltose vmaltotriose. Lc ny tinh bt tr nn ha tan trong nc, nht ca hn hp gim i ng k.Qu trnh ny c thc hin di s c mt ca enzyme -amylase v -amylase hnh thnh

cc phn t c chiu di mch ngn hn. Enzyme ny c th c trong bn thn ht tinh bt hayc b sung t ngoi vo. Tip theo enzyme glucose-amylase s c b sung vo tin hnhthy phn hon ton cc phn t mch ngn hnh thnh ng glucose. Ty theo loi snphm mong mun qu trnh chuyn ha ny c th c xc tc bi mt hay kt hp nhiuenzyme. Khi s dng enzym amiloglucosidase s cho ra cc sn phm giu glucose. Cn thyphn bng mt hn hp cc enzym - amylase v pululanase th cho sn phm giu maltose(90%). tch ring hai qu trnh dch ha v ng ha th cn s dng nhng iu kin nhit v pH ti u tng hot ca enzym cng nh c cht c trng thi ha tan tt.

3. Sng siu m

3.1.nh ngha

Sng siu m l sng m thanh c tn s ln hn tn s gii hn trn ngng nghe cangi bnh thng, tc l c tn s ln hn 20 kHz. Sng siu m c nhng c tnh ca sng mnh phn x, nhiu x, giao thoa v c th lan truyn trong mi trng kh, rn, lng.

3.2.Phn loi

Da vo tn s, sng siu m c chia lm 3 loi:

- Siu m tn s thp (siu m nng lng cao) (20 100 kHz): khi c s hnh thnh vv ra ca cc bong bng kh c kch thc ln s lm cho nhit v p sut tng cao. Do ckh nng lm thay i tnh cht ha l ca nguyn liu. V vy c s dng ph v t bohay lm bn h nh tng. Ngy nay siu m tn s thp c ng dng trong iu khin qu

trnh kt tinh, loi kh khi thc phm dng lng, v hot enzyme, tng hiu qu qu trnh trchly cng nh tng tc cc phn ng ha hc (Knorr v cng s 2004, McClements 1995,Roberts 1993, Zheng v Sun 2006).

- Siu m tn s cao (siu m nng lng thp) (100kHz-2MHz): khi tn s cao, kch thccc bong bng kh kh nh nn qu trnh si bt din ra nh nhng hn. Do khng lm thayi nhng tnh cht ha l ca nguyn liu nn c thng c dng trong phn tch, c bittrong phn tch thc phm nhm xc nh tnh cht ha l ca thc phm cng nh thnh phncu trc v trng thi vt l ca thc phm (Fellows 2000, Jayasooriya v cng s 2004, Knorr vcng s 2004, McClements 1995). So vi cc phng php phn tch truyn thng vi tc dngtng t th vic p dng sng siu m em li hiu qu nhanh v chnh xc hn.

- Siu m chn on (5-10MHz): lc ny khng cn hin tng si bong bng v c chchnh ca siu m trong khong tn s ny l dng m thanh, dng o h s tc v hp thca sng trong mi trng, dng trong y hc, phn tch ha hc.

Phn ln, nhng nghin cu v sng siu m trong thc phm thng gii hn trong khong 20-40kHz (thuc vng tn s thp, nng lng cao).

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Hnh 14 : Cc mc tn s ca sng m3.3.Cc thng s cn xc nh trong qu trnh x l bng sng siu m

Ba thng s thng c xc nh trong cc th nghim siu m l vn tc siu m, h ssuy gim v m tr. Nhng thng s ny lin quan ti tnh cht vt l ca thc phm nh thnhphn, cu trc v trng thi vt l (McClements, D.J., 1995)

3.3.1. Vn tc siu m

Vn tc (c) sng siu m di chuyn qua nguyn liu ph thuc vo module n hi (E) v ttrng ( ) ca n:

Module s dng php ton trn ph thuc vo loi nguyn liu l kh, lng hay rn, vc sng nn hay sng ct tc ng (Hnh 1.13). Module n hi v t trng ca nguyn liu phthuc cu trc, thnh phn v trng thi vt l ca n, do vn tc siu m c th s dng cung cp thng tin cho cc tnh cht ny. Vn tc siu m ca mt nguyn liu c th c xcnh bng mt trong hai cch: hoc o chiu di bc sng ca sng siu m ti mt tn s f bit c = f, hay o thi gian t cn sng di chuyn qua mt khong cch xc nh d t tnhc c = d/t.

3.3.2. H s suy gim

H s suy gim () l php o gim bin ca sng siu m khi n di chuyn quanguyn liu. Nhng nguyn nhn chnh ca s suy gim l s hp ph v s phn tn. S hpph c to nn do c ch vt l bin i nng lng tch tr c khi siu m thnh nhit, vd nh nht lng, s dn nhit v gim khi lng phn t. S phn tn xut hin trongnguyn liu khng ng nht, nh nh tng, huyn ph v bt, khi sng siu m tc ng ginon v c phn tn c hng khc vi sng ti. Khc vi trng hp hp ph, nng lngvn c tch tr khi siu m, nhng khng nhn ra c do s lan truyn c hng v pha can thay i. Php o s hp ph v phn tn ca sng siu m cung cp thng tin v tnh cht ha

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l ca nguyn liu thc phm, bao gm nng , nht, gim khi lng phn t v cu trcvi m.

H s suy gim ca nguyn liu c biu th bng neper trn mt (Npm-1) v c nhngha bng php ton sau:

Trong Ao l bin ban u ca sng, v x l khong cch di chuyn. H s suy gimc xc nh bng cch o s ph thuc ca bin sng siu m vo khong cch v iuchnh php o vo cng thc trn. H s suy gim thng c biu th bng decibel trn mt(dBm-1), vi 1Np = 8.686 dB

3.3.3. m tr

Khi sng siu m ti b mt chung gia hai nguyn liu khc nhau, n b phn x mt phnv truyn qua mt phn. T l ca bin ca sng phn x (A r) vi sng ti (Ai) c gi l hs phn x (R). Vi sng phng thng n bin phng:

Trong , Z l m tr (tng ng vi c), v k hiu 1 v 2 ch hai nguyn liu khcnhau. Rt t sng siu m phn x t b mt ca nguyn liu c m tr ging xung quanh. Ngcli, t l phn trm ln sng siu m b phn x khi hai nguyn liu c m tr rt khc nhau.

Ging vi vn tc siu m v h s suy gim, m tr l mt ch tiu vt l c bn, ph thucvo thnh phn v cu trc vi m ca nguyn liu. Do m tr c th c s dng cung cpcc gi tr ny ca thc phm.

3.4.C ch tc ng ca sng siu m

3.4.1. C ch xm thc kh

Tc ng c s ca sng siu m ln mt mi trng lng lin tc l do tc ng ca mtp sut m thanh (Pa) v mt p sut thy tnh sn c trong mi trng. p sut m thanh l sngdng sin, ph thuc vo thi gian (t), tn s (f) v bin p sut ln nht ca sng (P a max)(Muthukumaran v cng s, 2006):

Bin p sut ln nht ca sng (Pa max) t l thun vi nng lng u vo ca ngun pht sium (transducer). cng (bin ) thp, sng p sut to ra s chuyn ng v trn ln bn

trong cht lng, c gi l dng m thanh (acoustic streaming). cng cao hn, p sutcc b trong pha gin n ca chu k ri xung di p sut hi ca dung dch, hnh thnh nnnhng bong bng nh (l s hnh thnh nhng bong bng kh bn trong cht lng). Ti mtkhong kch thc ti hn, s dao ng ca cc bong bng s tng ng vi mt khong tn ss dng ca sng m do s lm cho bong bng n.

3.4.1.1. M t hin tng

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Sng siu m, ging nh cc sng m khc, bao gm cc chu k nn v gin. Cc chu knn tc ng mt p sut dng ln cht lng, y cc phn t cht lng li gn nhau, cc chu kgin tc ng mt p sut m, ko cc phn t cht lng ra xa nhau. Trong sut chu k gin, sngsiu m c cng ln c th to ra cc bong bng. Cc phn t cht lng c lin kt vi

nhau nh lc hp dn, do mt bong bng hnh thnh, sng m phi to ra mt p sut mtrong chu k gin ln hn cc lc hp dn ca cht lng.

Lng p sut m to ra cn ph thuc vo:

Loi cht lng: lc lin kt gia cc phn t cng cht ch th p sut m cn to ra cngln v ngc li khi lc lin kt gia cc phn t cht lng lng lo th p sut m chcn t mt gi tr nh.

tinh khit ca cht lng: i vi cc cht lng tinh khit, sc mnh lin kt ca chtlng qu ln n ni sng siu m khng to ra c p sut m ln hnh thnhbong bng. i vi cht lng khng tinh khit, sc mnh lin kt ca cht lng b gim

do cc kh c by vo trong cc rnh ca cc phn t rn nh. Khi mt rnh y kh btc ng bi mt p sut m, lc ny p sut trong rnh kh gim, lm cho kh trong rnhc ko gin ra cho n khi mt bong bng nh c hnh thnh trong dung dch. Huht cc cht lng u cha cc phn t nh to iu kin cho s si bong bng.

Khi bong bng c hnh thnh n s tip tc hp th nng lng t cc chu knn v gin di tc ng ca sng siu m. iu ny lm cho cc bong bng tiptc ln ln. Khi cc bong bng pht trin t n mt kch thc ti hn, n khngc kh nng hp th nng lng t sng siu m na. Do khi khng c nnglng vo, cc bong bng khng chu c p sut bn trong v cui cng bongbng n tung to ra s cn bng ng gia p sut bn trong v bn ngoi cht

lng (Suslick, 1989).Hin tng ny gi l hin tng si bong bng (hay cn gi l hin tng xmthc kh cavitation). y cng l tc ng quan trng nht ca sng siu mnng lng cao. Thng qua hin tng ny, nng lng c hc ca sng siu mc bin i v truyn qua dung dch lng. (Suslick, 1988; Laborde, 1998).

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Hnh 15 : Qu trnh hnh thnh, pht trin v v tung ca bt kh

trong mi trng lng (Mason, 1998)

3.4.1.2. Phn loi qu trnh si bong bng

- Si bt kh n nh(stable cavitation): l s si bt kh t sng siu m c mc nnglng thp to ra nhng bt kh c kch thc nh v t thay i trong sut cc chu trnh nn vgin n.

- Si bt kh nht thi(transient cavitation): i vi sng siu m c mc nng lng cao,kch thc ca nhng bt kh thay i rt ln. Din tch b mt ca bt kh tng trong sut chutrnh gin n. V vy s thot khi cng tng theo. Kt qu l kch thc ca bt kh tng ln sau

mi chu trnh. Sau nhiu chu trnh nn v gin n, bt kh s t kch thc gii hn m nnglng m khng cn kh nng gi pha hi bn trong. n chu trnh nn tip theo, hi bt chtngng t v nhng bt kh s v. Nhng phn t xung quanh bt kh va chm nhau mt cchmnh lit, to ra nhng vng c nhit v p sut cao ln n 5500oC v 50MPa.

Trong sut qu trnh siu m, s si bt kh n nh c th tr thnh s si bt kh nht thi haychng cng c th ng thi xy ra (Atchley v Crum,1988).

3.4.1.3. Cc yu t nh hng

- Tn s: tn s t l nghch vi kch thc bong bng. Do , siu m c tn s nh s tora cc bong bng ln, khi hin tng si bong bng din ra mnh m. Ngc li khi tn s gia

tng, khu vc si bt bong bng tr nn t d di hn v khi tn s nm trong gi tr MHz thkhng cn quan st c hin tng si bt bong bng na v c ch chnh l dng m thanh(acoustic streaming).

- Cng : siu m cng cao c th lm gin bong bng qu nhanh trong sut chu kp sut m do lm cho bong bng khng c c hi co rt trong chu k p sut dng. Ngcli khi cng siu m nh hn th s ln bong bng gin ra v nn li s tng ln. Do thigian x l s di hn.

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- Bin dao ng: khi bin dao ng tng th s lng bong bng kh cng tng ln do cng gp phn lm tng cng hin tng si bt kh.

- p sut: p sut thy tnh cao c th chng li s khuch tn kh ra khi bt kh, lm gims si bt kh. Do s gia tng p sut ngoi (c iu khin bng p sut i) s lm tng

ngng ca s v bt kh v gim lng bt kh to thnh. Tuy nhin s gia tng p sut ngoili lm tng p sut bn trong nhng bt kh khi chng v ra, kt qu l s v bt kh s din ranhanh hn v mnh m hn. Do s gia tng p sut i l mt phng php lm gia tng hiuqu ca qu trnh x l vi sng siu m thay v thay i bin dao ng.

- Nhit : nhit tng s lm gia tng s lng bt kh to thnh, tuy nhin cng sv bt kh s b gim do nh hng ca p sut hi tng ln v ng vai tr nh lp m, ngncn s va chm ca cc phn t xung quanh khi bt kh v. Ngc li, s v bt kh s kh khnkhi nhit gim, v nht mi trng tng cao. S gia tng nhit s lm gim nht, qutrnh v bt kh din ra mnh m hn. Do , nhit phi c iu chnh sao cho nht thp lm gia tng mnh ca s v bt kh, tuy nhin nhit cng khng qu cao khnglm gim mnh ca s v bt kh bi p sut hi cao.

3.4.2. Khuch tn chnh lu

Trong nhiu trng hp, s phn phi kch thc cc bong bng l thng s ch cht kim tra tc ng m hc. Qu trnh khuch tn chnh lu biu hin bng s khng n nh cakh ha tan trong dung dch v kh vo bong bng lm tng bn knh ca n trong trng sium. Do , nu khng c sng siu m hay bt k mt c ch n nh no, cc bong bng s hatan dn dn (Gupta v Kumar, 1983). V vy c ch n nh thch hp l: khi cn bng, thnhbong bng b lm, do p sut ph thuc sc cng b mt gip cho vic n nh cc bong bngkh v chng li s ha tan ca chng. S khuch tn chnh lu trc tip t bn trong xoaychuyn thng qua vic bm kh ha tan ban u trong cht lng vo trong bong bng, s dngnng lng siu m. C hai yu t ng gp vo qu trnh ny: tc ng din tch v tc ng v.

- Tc ng din tch: l do s tng ng gia phng dng chy v din tch thnh bongbng. Khi bn knh bong bng nh hn bn kinh cn bng, kh bn trong c p sut cao hn gitr cn bng, do khuch tn ra ngoi cht lng. Ngc li, khi bn knh bong bng cao hnnhiu so vi bn knh cn bng, p sut kh bn trong thp hn gi tr cn bng nn kh khuchtn t cht lng vo bong bng. Tuy nhin, tc dng chy thc ca kh khng cn bng trongsut pha nn v pha gin ca s dch chuyn bong bng do din tch thnh bong bng (b mttng tc trao i) ca trng hp sau cao hn trng hp u. Do , theo thi gian s c strn kh vo trong cht lng.

- Tc ng v: xut hin do tc khuch tn kh trong cht lng t l vi gradient nng kh ha tan. Khi bong bng dao ng, v hnh cu ca cht lng bao quanh bong bng s thay i

th tch nn gradient nng s thay i theo. Xt bong bng iu kin cn bng vi hai lp vbao quanh n. Khi bong bng gin ra, mi lp v cht lng s co li. Nng kh ha tan trongcht lng st bong bng nh hn gi tr cn bng (nh lut Henry) nhng v mng hn so vibong bng bn knh cn bng dn n gradient gia hai bn v s cao hn. Do tc khuch tn kh i vo v i ra khi bong bng cao. Khi bong bng co li, lp v cht lng xungquanh bong bng s gin ra mc d nng ca kh gn thnh bong bng cao hn so vi khibong bng gin (theo nh lut Henry) nhng dy gia tng ca thnh bong bng c ngha lgradient nng thp hn so vi khi bong bng gin ra. Hai yu t ny (nng kh thnh

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bong bng v dy v) kt hp vi nhau khi bong bng gin ra, nhng chng li nhau khi bongbng co li.

Kt qu l c din tch b mt thnh bong bng v tc khuch tn kh ha tan u bt i xngv phng din gin ra v co li: tc ng din tch v tc ng v tng cng ln nhau. Tc

ng kt hp c ngha l trong sut qu trnh si bong bng phi tuyn trong trng siu m vacng va , bn knh cn bng m bong bng dao ng s c khuynh hng tng ln(Eller v Flynn, 1965; Eller, 1972; Crum, 1984; Church, 1988a,b). S khuch tn chnh lu canhit c th xy ra, trong s dao ng ca bong bng gy nn s hnh thnh vi phn nhit davo gradient tn ti trong mi trng khng c siu m (Wang, 1974).

p sut m hc ngng ca s ln ln ph thuc vo kch thc bong bng v tn s mhc. Ngng p sut m hc t mc ti thiu cc b cng hng iu ha v cng hngiu ha di nc (Church, 1988a). Tc ln ln ti thi im ngng b vt qu do nhhng mnh m bi s hin din ca tc nhn hot ng b mt v vi dng, tc ng ln vic vnchuyn kh ra khi thnh bong bng (Church, 1988b). Tc ng ca vi dng n gin v mt nhtnh. Khi bong bng ln ln nh khuch tn chnh lu, kh ha tan c ly t cht lng gn bong

bng. Nu khng c dng chy, tc thiu ht ph thuc vo tc kh ha tan c thkhuch tn t nhng vng xa bong bng. Do y l mt qu trnh chm, cht lng bn ngoithnh bong bng s b tho kit kh ha tan. S thay i v gradient nng lm gim tc lnln nhiu hn. Tuy nhin, cc dng chy vi dng c khuynh hng em cht lng t xa n gnthnh bong bng. S i lu ca kh ha tan lm gim s tho kit kh v lm tng tc ln ln.Vi dng s np lin tc cht lng thnh bong bng, cung cp cho n mt nng kh ha tangn vi nhng vng xa bong bng. Hin tng i lu thch hp: nu mt bong bng ang hatan, vi dng s c khuynh hng dch chuyn t nhng vng bn ngoi thnh bong bng. Do ,nng kh ha tan d lm tng tc ha tan.

3.5.ng dng ca sng siu m trong cng ngh thc phm

Bng 7 :Cc ng dng ca siu m nng lng cao trong cng nghip thc phm (Patist, Bates,2008)

ng dng C ch Li ch

Trch ly Tng qu trnh truyn khi, gii phng cc

thnh phn c trong t bo

Lm tng nng sut v hiu qu

trch ly

Nh ha S v nhng bt kh s gip cho 2 pha

khng tan ln vo nhau c trn ln vo

nhau hiu qu hn

S hnh thnh h nh hiu qu hn

Kt tinh To mm v iu chnh s hnh thnh tinh

th

Hnh thnh nhng tinh th nh

Lc Lm nhiu lon lp bin Gia tng tc dng chy, gim tc

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nghn

Thay i

nht

Thay i cu trc thun nghch hoc khng

thun nghch, dn n s hnh thnh lin kt

ngang hoc ti cu trc li

Lm gia tng bn cht ca cc qu

trnh, gim ph gia

Ph bt p sut m s lm v nhng bt kh Tng nng sut, lm gim hoc loi

b nhng cht ha hc chng to

bt

p n Dao ng c hc, gim ma st Tng nng sut

V hot

enzyme v

VSV

Tng qu trnh truyn nhit cng nh lc

trt. S v nhng bt kh s nh hng ln

thnh t bo VSV

V hot enzyme nhit thp

nhm nng cao cht lng sn phm

Ln men Tng qu trnh truyn c cht, kch thch cc

qu trnh sng

Tng sn lng ca cht chuyn

ha, tng tc qu trnh ln men

Truyn

nhit

Tng qu trnh truyn nhit do s v bt kh Tng tc qu trnh truyn nhit, lm

lnh, sy nhit thp.

4. nh hng ca sng siu m n qu trnh thy phn tinh bt

Di tc ng ca sng siu m cc ht tinh bt s trng n, ph v ht, gii phng ra ccsi amylose v amylopectin, sau cc si ny tip tc b ct ngn mch gii phng ra ccdextrin v cui cng l cc ng n gin nh maltose v glucose... Cc phn ng ny phthuc vo nguyn liu, thit b s dng cng nh iu kin phn ng (lin tc hay gin on).i vi nguyn liu ngoi yu t quan trng nht l t l amylose / amylopectin hay ni cchkhc l t l vng kt tinh / vng v nh hnh th nng mu cng nh hng n hiu qu xl ca sng siu m. Loi my pht siu m ( b siu m hay thanh siu m), cng v thi

gian siu m l nhng yu t lin quan n thit b. Thng qua vic kho st cc thng s nychng ta c th xc nh c hiu sut cng nh gip cho vic iu chnh qu trnh ti u hn a vo ng dng trong thc tin.

Cc thng s tc ng n qu trnh

4.1. Yu t thit b

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Hin nay c hai loi thit b c s dng pht siu m l b siu m v thanh siu m.B siu m thng c s dng vi cng chiu nh hn do din tch pht siu m ln hnthng qua thnh thit b so vi thanh siu m. Mc d vy thanh siu li cho tc dng cao hn dovic lan truyn ca sng cao nn d dng va chm v tc ng vo ht hn. T lm ht trng

n v b ph hy nhiu hn. i vi cc thit b ging nhau thng qu vic iu chnh cng chiu hay thi gian chiu cng s nh hng ln n qu trnh x l nu s thay i ny cxem l ng k. Khuynh hng chung hin nay vi cng siu m cng ln, thi gian chiucng di, mc thy phn s cng nhiu. i vi cc th nghim ch yu cu ht trng n thvic tng cng cng nh thi gian chiu s khng cho hiu sut ti a, cn vi yu cu phv ht mc ph v s tng t l vi cng v thi gian chiu sng siu m. Nhng tc hiu qu nng lng cao th chng ta cn kho st thng qua thc nghim tm cthng s ti u nht hiu sut phn ng cao nht ng thi nng lng s dng l thp nht.Bi v trong qu trnh ph v s lm cho nht dch tng ln n mt lc no khi nhtqu cao sng siu m khng th gy ra c cc rung ng cho cc si tip tc ph v n nath hiu sut phn ng s tng chm li hay gn nh l khng tng. Nhit qu trnh x l cngc th c iu chnh. Nhit cng cao gy ra cc chuyn ng nhit hn lon cng vi tcng gy rung ng ca sng siu m cng lm ht d dng b ph v hn.

Chng ta s cng kho st s thay i cc thng s ny i vi tng qu trnh c th khitinh bt b thy phn. u tin di tc ng ca c ch khuyt tn chnh lu cc phn t ncchuyn ng v xm nhp vo bn trong ht. Khi chng s lin kt vi cc si trong ht thngqua cc lin kt hydro lm ht tng th tch hay ni cch khc ht b trng n. ng thi lc nc cng li ko cc si amylose v amylopectin ra bn ngoi lm cu trc ht tinh bt b phv. Kt qu lm gim kch thc ht nu thi gian x l di, cng chiu ln th ht khng cn

nguyn vn na m s b r ra. Khi nht ca dch tng ln v vic gii phng ra cc si nys lm tng kh nng ha tan so vi dng nguyn ht ban u.

Ivana Ljubi Herceg (2010) tin hnh th nghim vi tinh bt bp nng 10% vi sthay i thit b chiu l thanh siu m vi cng 2 W.cm -2 v b siu m vi cng 34W.cm-2 trong cng khong thi gian l 15 pht. Kt qu cho thy hnh thi ht s thay i tythuc vo thit b s dng. C th khi s dng b siu m cc ht c khuynh hng kt li nnkhng c s thay i ng k kch thc ht v ch ch yu gim mt lng nh nhng htcha b kt li cn khi s dng thanh siu m kch thc ht gim tng i nhiu hn. Bn cnh Ivana Ljubi Herceg cng tin hnh kho st s thay i cng chiu trong trng hp s

dng thanh siu m vi cng thay i 34, 55 v 73 W.cm -2 trong cng thi gian l 15 pht.Theo l thuyt cng x l cng ln kch thc ht cng gim nhiu hn. Nhng thc chtdi tc ng ca sng siu m bn cnh vic ph v ht n cng tc ng vo cc phn t ncto ra cc gc t do l H+ v OH-. Cc gc t do sau s thot ra ngoi v c khuynh hng kthp vi cc phn t ha tan khc. Do khi cng cao hn mc gii hn cc gc t docng nhiu nn cc ht d dng lin kt vi nhau thng qua cc gc t do ny dn n kch thcht tng ln v cc ht s kt li vi nhau nhiu hn.

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Hnh 16 : Hnh nh SEM vi cng chiu (a) 34 W.cm-2 (b) 55 W.cm-2 (c) 73 W.cm-2

(Ivana Ljubi Herceg, 2010)

Tng t khi thay i thi gian chiu kch thc ht cng s thay i. i vi cng chiuva phi th khi thi gian chiu tng kch thc ht s gim theo thi gian. Nhng trong trnghp cng chiu cao tng t nh phn gii thch trn kch thc ht c khuynh hng ngcli l tng ln v kt li vi nhau. Chng ta c th quan st trong cc hnh nh c chp bngSEM.

Hnh 17 : Hnh nh ht vi cng chiu 34 W.cm-2 trong (a) 15 pht (b) 30 pht


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Hnh 18 : Hnh nh ht vi cng chiu 73 W.cm-2 trong (a) 15 pht (b) 30 pht


Wenjian Cheng (2010) cng tin hnh th nghim v cho kt qu tng t. iu kin th nghim

c iu chnh vi cc bc thi gian khc nhau v cng chiu l 74 W.cm-2.

Hnh: Hnh thi ht tinh bt sau qu trnh chiu sng siu m trong thi gian (a) 0 pht, (b) 2.5pht, (c) 5 pht, (d) 10 pht, (e) 15 pht di knh hin vi quang hc c phng i l 100.

(Wenjian Cheng, 2010)

Nhn xt: trc khi x l sng siu m ht gn nh cn nguyn vn. Sau 15 pht x l tt c ccht bin mt. Di tc ng ca sng siu m (tc ng c hc v nhit ) l ph v lin ktngang gia cc polymer (ch yu l amylose v amylopectin). Khi cc ht r ra hon ton.

Khi ht b ph v v gii phng cc si nht ht v ha tan tng dn do s tng hmlng cc cht ha tan. Thi gian chiu cng di, cng cng ln, ht b ph hy cng nhiuth nht v ha tan cng tng. Cc s liu c th v nht v ch s ha tan cho trongbng sau:

Bng 8 : nht v ch s ha tan ht tinh bt vi s thay i cc thng s v thit b khi httrng n v b ph v (Ivana Ljubi Herceg, 2010)

Thit b chiu Cng chiu(W.cm-2)

Thi gianchiu (pht)

nht(BU)

Ch s ha tan(%)

- - 15

30

657

658

0.04

0.03

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B siu m 2

2

15

30

679

851

3.01

3.29

Thanh siu m 34

34

15

30

1129

1158

3.86

4.02

Thanh siu m 55

55

15

30

1452

1187

5.07

5.28

Thanh siu m 73

73

15

30

1080

1346

5.85

6.45

Nhn xt: ch s ha tan tng tng ng vi sc tng cng v thi gian chiu. nht cng

tng khi cng v thi gian chiu tng nhng khi cng t n mt gi tr no cc sis b ct ngn mch do lm nht gim v nhng khi s lng cc phn t mch ngn nhiuhn th nht cng tng ln theo. Cng tng t vi cc kt qu trn thanh siu m em li hiuqu cao hn so vi b siu m.

H qu i km vi vic chiu sng siu m l s tng nhit mu. Cng chiu cngln, thi gian cng di nhit mu cng cao. Do y cng l mt tc nhn gp phn tnghiu sut qu trnh thy phn. S liu c th c trnh by trong bng sau:

Bng 9 : Nhit huyn ph tinh bt sau qu trnh x l bng sng siu m


Thit b chiu Cng chiu

(W.cm-2)

Thi gian chiu

(pht)

Nhit mu sau chiu siu m

(0C)

- - 15

30

18.1

18.1

B siu m 2

2

15

30

20.3

21.4

Thanh siu m 34

34

15

30

40.2

50

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Thanh siu m 55

55

15

30

37.2

42.2

Thanh siu m 73

73

15

30

49.4

56.4

Tng t Qiang Huang (2007) cng tin hnh th nghim kho st thi gian x l tc ngnh th no n mc thy phn vi nguyn liu tinh bt bp m 13.5%. Kt qu cho ccng tng t nh Ivana Ljubi Herceg khi thi gian x l tng mc thy phn hay ph v ccht cng tng. Trong th nghip thi gian s c iu khin trong khong t 0 15 pht vikhong thi gian thay i ngn hn th nghim trn. Do s gip chng ta d on kt quchnh xc hn.

Bng 10 : S thay i mc thy phn theo thi gian (Qiang Huang, 2007)

Thi gian (pht) Mc thy phn (%)0 03 3.16 7.89 15.7

12 17.615 18.4

Nhn xt: mc thy phn tng nhanh khi thi gian x l bng sng siu m tng t 3 9 pht.Sng siu m c th nh hng n vng v nh hnh trong thi gian 3 9 pht trong khi vng kt tinh khng d dng b nh hng. T 9 15 pht qu trnh thy phn cc vng kt tinh

xy ra ch yu. Do c cc vng ny c cu trc kh cht ch nn mc thy phn trong khongthi gian ny tng kh chm. Khi ht cha b thy phn, b mt ht trn lng nhng khi ht bthy phn trn b mt ht bt u xut hin cc l nh trn b mt. Cc l to v nhiu hn khimc thy phn tng ln. Cc l ny phn phi u nhau v c hnh dng nh t ong.

Hnh 19 : SEM ca ht tng ng mc thy phn 0 , 3.1, 18.4% (Qiang Huang, 2007)

Wenjian Cheng (2010) cng tin hnh th nghim vi mc ch tng t. Tinh bt bp vithnh phn ha hc carbonhydrate 99.05%, proteins 0.24%, cht bo 0.45%, tro 0.12% v t lamylose l 28%. Huyn ph tinh bt vi nng 3%, 5%, 7%, 10% u tin s h ha trc 900C trong 30 pht v tc khuy l 100 rpm. Sau c lm ngui xung 60 0C v tin hnh

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chiu sng siu m trong cc khong thi gian khc nhau 0, 2.5, 5, 10, 15 v 30 pht nhit l

60 30C vi my pht siu m c tn s 20kHz v u pht ra m thanh c ng knh cui l0.6 cm, nng lng c ci t 74 W/cm 2. Mu em chiu sng siu m c t trong biu nhit trnh s tng nhit.

Hnh 20 : nh hng ca sng siu m ln nht biu kin vi s thay i nng dch tinhbt (Wenjian Cheng, 2010)

Nhn xt: kt qu cho thy nht biu kin gim nhanh i vi cc nng khc nhau ca htinh bt sau 15 pht. Sau nht gim chm v nu thi gian ko di th nht khng gimna. V sau 30 pht x l nht ca dch cc nng khc nhau gn nh xp x nhau v t

gi tr kh thp dao ng trong khong ln cn 10 mPa.s.

Hnh 21 : nh hng ca sng siu m ln ha tan (Wenjian Cheng, 2010)

Nhn xt: vi qu trnh x l sng siu m ko di, ha tan ca dch tng nhanh l do s gyv cc lin kt ca cc ht lm tng linh ng ca cc mch polymer. Sau 30 pht x l hatan gn nh t 100% i vi cc dch c nng khc nhau..

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Khi ht b ph v v ct mch to thnh cc dextrin phn t lng nh hn, nu chng tatip tc qu trnh x l th trong ht s xy ra tip qu trnh ng ha to thnh cc sn phmng n gin. Qu trnh ny c iu khin qua s kho st hm lng ng kh c giiphng. Nghin cu khc tin hnh vi nguyn liu l tinh bt khoai m vi cc ch x l khc.

Cc mu tinh bt thu c trc v sau khi nu c x l siu m trong 20 40s bin daong t 180 to 299mpp, sau em x l enzyme (-amylase v glucoamylase). Kt qu SEMcho thy cc mu siu m c tc to ra ng kh tng 3 ln so vi cc mu kim chng.(Nitayavardhana, 2008)

Hnh 22 :Hnh nh SEM ca h tinh bt khoai m (a) mu kim chng, (b) nng lng thp (20s),(c) nng lng thp (40s), (d) nng lng cao (20s), (e) nng lng cao (40s) (Nitayavardhana,

2008)

Lng ng kh tng t l thun vi nng lng v thi gian siu m (c th tng n180% so vi mu khng siu m). Cc mu h tinh bt c b sung enzyme trong sut qu trnhsiu m cho lng ng kh cao hn cc mu cho enzyme vo sau siu m. Nhit ta ra trongsut qu trnh siu m nu thp hn nhit h ha tinh bt s khng lm tng lng ng kh(Nitayavardhana).

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Hnh 23 :Lng ng kh v nhit gia tng nhng iu kin siu m khc nhau(Nitayavardhana, 2008)

Nhn xt : kt qu cho thy hm lng ng kh tng nh siu m t l thun vi nng lng vthi gian siu m. Hm lng ng kh cao nht l 51 v 46g/100g mu thu c khi enzymecho vo sau siu m 40s v enzyme cho vo trc siu m 40s, tng ng, mc nng lngcao.

4.2. Yu t nguyn liu

Cc loi nguyn liu khc nhau th c t l vng kt tinh / vng v nh hnh khc nhau.Vng kt tinh lin quan n hm lng amylose c lin kt li vi nhau to thnh mt mngli cht ch cn vng v nh hnh lin quan n hm lng amylopectin dng si t do ccu trc mch di, cng knh kh tin gn vi nhau to lin kt nn cc vng v nh hnh nys b sng siu m tc ng d dng hn. Nng tinh bt cng c nh hng n hiu qu x l

ca sng siu m. Tinh bt c nng cng cao th nht cng ln gii thch tng t nh trnkt qu lm gim hiu sut phn ng. Do khi x l chng ta cng cn kho st tm ra nng ti u nht hiu sut phn ng l cc i.

Trc ht chng ta s i vo xem xt i vi cc loi ht khc nhau th ha tan ca hts bin i nh th no theo thi gian x l. Nhng nghin cu tinh bt khc nh khoai ty, khoaim, khoai lang, tinh bt bp ca Yasuo Iida (2007) cng cho kt qu tng t nh tinh bt bphay khoai m c kho st phn trn. Kt qu c tm tt trong cc bng kt qu sau vinng tinh bt l 5%.

Bng 11 : S thay i ha tan ca cc loi ht tinh bt khc nhau theo thi gian

(Yasuo Iida, 2007)Mu Thi gian chiu

(pht)Mc ha tan (%)

Bp np

% amylopectin 100%

0

1

5

0.004

0.115

0.161

Khoai ty

% amylopectin 78%

0

1

5

0.084

0.63

0.71

Khoai m

% amylopectin 83%

0

1

0.13

0.806

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ng knh ht 5 0.843

Khoai lang

% amylopectin 90%

0

1

5

0.01

0.021

0.037

Bng 12 : S thay i nht ca mt s loi tinh bt bi sng siu m trong 30s

(Yasuo Iida, 2007)Mu nht (mPa.s)

60 C 50 C 40 C 30 C 20 C

Bp np 254 300 372 440 586

Khoai ty 528 782 2100 3110 5410

Khoai m 574 900 1420 2110 3200

Khoai lang 656 760 912 1140 1310

Nhn xt: khi chiu sng siu m nht ca cc dch t cc ngun khc nhau u c khuynhhng gim. Nhit chiu cng cao nht ca dch cng gim.

Mt khc nng cng l mt yu t tc ng khc ln n hiu sut phn ng. nng tinhbt cao (20-33.3% cht kh), h tinh bt c th ha lng nh siu m. nht tinh bt nng va phi (5-10%) c th gim thp hn 100 mPas nh siu m trong 30s. (Yasuo Iida, 2008)

Hnh 24 :nh hng ca nng tinh bt ln s thay i nht theo nhit

(Yasuo Iida, 2008)

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Nhn xt: nht dch gim ng k khi siu m 30 pht dung dch tinh bt bp np 5% v 10%trong khong nhit 20 600C. Sau 30 pht x l siu m nht ca mu hai nng gnnh xp x nhau.

Hnh 25 :Lng ng kh ca cc mu siu m mc nng lng cao trong vng 30s ccnng cht kh khc nhau.( Saoharit Nitayavardhana, 2008)

Nhn xt : hm lng ng kh l 9.7, 14.4 v 22g/100g mu ng vi nng 5%, 15% v25%. nng cao hn, nhiu ht c x l siu m hn, m cu trc thnh t bo v giiphng ra nhiu ht tinh bt hn cho enzyme thy phn to thnh ng sau ny.

Xt v kha cnh cn bng nng lng, hiu sut cao nht thu c mc nng 25%.Hiu sut -64.0%, 59.0%, v 323.0% t c 5%, 15% v 25%TS, tng ng. Kt qu nytng ng vi lng ng kh to ra. Khi mt nh my c quy m ln vn hnh 25-33.3%cht kh, s kt hp sng siu m c th lm tng ng k hiu qu kinh t.

Hnh 26 : Hiu qu chiu sng siu m cng lc cao vi nng cht kh khc nhau

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( Saoharit Nitayavardhana, 2008)Melissa Montalbo-Lomboy (2010) cng thu c kt qu tng t qua th sau :

Hnh 27 : Hm lng ng kh sau 3h ng ha vi cc ch x l bng sng siu m khcnhau trong trng hp x l lin tc so snh vi mu i chng l ng chm gch ngang.

(Melissa Montalbo-Lomboy, 2010)

Nhn xt: qu trnh x l bng sng siu m lm tng cng qu trnh ng ha h tinh bt.Hiu sut x l bng sng siu m tng t 40 330% so v mu i chng. Hm lng ngkh cng tng theo nng lng v thi gian chiu sng siu m. Thi gian x l cng di, nnglng sng cng ln th hm lng ng gii phng ra cng nhiu. Trong trng hp thi gianx l 40s hm lng ng kh gii phng ra trong trng hp nng lng trung bnh v cao gnnh xp x nhau. Do ti im x l nng lng trung bnh, thi gian 40s c xem nh l iukin ti u nn khi tng nng lng hay thi gian x l th hm lng ng kh khng tng na.V im ny cng xem l im m ti qu trnh ng ha xy ra vi hiu sut cao nht. Hintng ny c th l gii l do vi nng lng tc ng cao s lm v hot gy c ch hot ngca enzyme do lm gim hiu sut phn ng.

4.3. Yu t iu kin phn ng

Chng ta c th tin hnh phn ng trong iu kin lin tc hay gin on. Trong cng

nghip phng php lin tc c s dng khc ph bin do em li hiu qu nng lng caohn phng php gin on. Ngoi ra trnh t x l mu bng sng siu m v b sung enzymecng tc ng n hiu sut phn ng thy phn. Thng thng sng siu m tc ng voenzyme theo hai hng: th nht i vi cc enzyme trong nguyn liu sng siu m c tc dngph v ht gii phng enzyme ra bn ngoi nn lm tng hot lc ca enzyme iu ny cngtng t nh enzyme c nh. Th hai i vi enzyme b sung dng t do do chng c bncht l protein nn cc mch polypeptide ca chng s b sng siu m tc ng gy ph v mch

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lm bin tnh enzyme dn n hot tnh enzyme gim. V vy ty thuc ngun enzyme s dngm chng ta c ch b sung khc nhau chng hn vi enzyme t do thng c b sung saukhi chiu sng siu m trnh lm gim hot tnh enzyme.

Hnh 28 : S h thng thit b chiu siu m lin tc (Melissa Montalbo-Lomboy, 2010)

Melissa Montalbo-Lomboy kho st s thay i iu kin th nghim i vi kch thc ht.Kt qu cho thy kch thc ht cng tng khi c chiu sng siu m trong phng phplin tc l c hiu qu cao hn. Tng t i vi hm lng ng kh. Mt nng lng caphng php lin tc ch dao ng trong khong nh t 4 14 kJ/L trong khi phng php ginon thay i t 87 260 kJ/L. Khi mt nng lng tng s dn n s tng hm lng ngkh gii phng ra. Hiu sut cao nht ca hm lng ng kh trong phng php lin tc30.2g/L tng ng vi mt nng lng l 12.6 kJ/L v phng php gin on l 61.6 g/Ltng ng vi mt l 227.4 kJ/L. Phng php gin on cho hiu sut cao hn gp 2 ln so

vi phng php lin tc nhng li tiu tn nng lng gp 18 ln. Hiu sut thu ng kh thpnht phng php lin tc l 18.1 g/L vi nng lng s dng l 4.9 kJ/L trong khi phngphp gin on phi tiu tn mt lng nng lng 87.7 kJ thu hm lng ng kh tngng ( 20.8 g/L). Do phng php lin tc c xem l c hiu qu nng lng cao hn sovi phng php gin on v ang c s dng kh ph bin hin nay.

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Hnh 29 : nh hng ca mt nng lng ca sng siu m n kch thc phn t (MelissaMontalbo-Lomboy, 2010)

Hnh 30 : Hm lng ng kh v mt nng lng u vo ca phng php lin tc v ginon (Melissa Montalbo-Lomboy, 2010)

Trong qu trnh ng ha vic b sung enzyme c th thc hin theo 2 ch sau: bsung trc khi chiu sng siu m (SD) hay b sung sau khi chiu (SA). Qua tin hnh cc thnghim, Saoharit Nitayavardhana thy rng mu trong trng hp nng lng sng siu m mc trung bnh, hiu sut gii phng ng kh khi b sung enzyme trc s cao hn nhng khinng lng tng hm lng ng kh gii phng ra gim xung do tc ng mnh ca sng

siu m s lm v hot mt phn enzyme. Do ty thuc v ngun enzyme, loi tinh bt, mc ch x l cho ph hp trnh lm v hot hot tnh enzyme.

Hnh 31 : nh hng ca ch b sung enzyme i vi hm lng ng kh (SaoharitNitayavardhana)

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Thng thng qu trnh x l bng sng siu m tin hnh sau khi ht h ha v khi mu trng thi dch nn sng siu m tc ng d dng v ng u hn. Bn cnh sau khi ht c h ha trc th qu trnh x l bng sng siu m s nh nhng hn c th cng chius thp hn v thi gian chiu c th ngn i. H qu s hn ch c s v hot enzyme s dng

trong qu trnh thy phn.

Hnh 32: Biu m t qu trnh x ht tinh bt c s dng sng siu m (Yasuo Iida, 2007)

4.4.ng dng ca sng siu m trong qu trnh ng ha

Do sng siu m lm tng hiu sut thu ng kh do c ng dng trong cc qu trnh lnmen sn xut cn, ru, bia vi c cht l glucose t cc ngun thc vt khc nhau. Vic sdng sng siu m cn c tc dng tng cng din tch tip xc gia c cht v enzyme do lm tng cng hiu sut phn ng em li gi tr kinh t cao. V hin nay phng php ny c ng dng trong vic sn xut cn sinh hc vi mc ch thay th cho cc loi nhin liu hathch. Ngoi mc ch gim gi thnh do cc nhin liu ha thnh c gi thnh ngy cng tngth cn sinh hc cn c u im l thn thin mi trng do gim i hin tng kh nh knh dovic t chy cc nhin liu ha thch sinh ra.

Hin nay cc loi bao b sinh hc ngy cng c nghin cu v ng dng rng ri trongcng nghip thay th cc loi bao b nha truyn thng trc y. Tinh bt c xem l mttrong nhng nguyn liu thay th y trin vng sn xut cc loi bao b sinh hc ny do ccc tnh sau: gi thnh nguyn liu r, thn thin mi trng do c kh nng t phn hy, tnh

chn sng cao so vi mng bao nha v c ngun cung cp kh di do . chuyn t tinh btthnh cc lp mng bao b c nhiu phng php thc hin nh l nguyn liu c n ra tmy p n v c thi to hnh hay nguyn liu c h ha trc v tin hnh to khun sau c nhng vo nc hay phun nc ln b mt v tip tc qu trnh sy kh. i vi mngthc hin bng quy trnh p n c tnh do thp v km bn vi nhit hn so vi phng phpto khun. Do phng php to khun hin nay vn cn l phng php ch yu c sdng sn xut bao b khng c v c th n c vi nng tinh bt khng qu cao hoc qu

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thp, thng ly 6%. Vn c t ra i vi mng bao l lp mng ny phi ng nht, bmt trn nhn, v phi c cu trc cht ch do tinh bt s dng phi hon ton tan trong nchay trong dung mi em s dng. Mc d tinh bt t nhin c tnh a nc cao nhng rt kh n ha tan hon tan trong nc do kch thc cc phn t kh ln v lin kt cht ch gia cc

phn t gy c ch s xm nhp ca phn t nc. Do tinh bt ha tan hon ton trongnc th ch s dng nng thp v phi cung cp mt lng nhit ln (trn 1000C) nn skhng mang tnh kinh t cao. V vy k thut siu m c s dng trong qu trnh sn xutny. Kt qu nht ca dch h tinh bt tng, tng kh nng ha tan v trong. Nguyn nhnl do sng siu m lm tng s linh ng ca cc phn t tinh bt do lm ht d dng b phv v hnh thnh nn dung dch ng nht. So snh vi phng php ha tan tinh bt truynthng th phng php ny c chi ph thp hn v hiu qu tc ng cao hn.

Qu trnh x l sng siu m thch hp hn cho phng php to khun v c th thc hinc ngay c trong iu kin nng tinh bt cao. Vic x l ny lm cho mng bao t c

nhng tnh cht tt hn nh ci thin trong, tng kh nng chng thm v tng bn camng bao. Bn cnh cn tn ti mt nhc im l s gy v ca mng khi chiu sng sium nhng n c th c khc phc bng cch thm vo cht do ha nh glycerol tngcng lin kt do lm tng bn ca mng bao.

Kt lunVic ng dng sng siu m h tr qu trnh thy phn tinh bt tuy cn kh mi m nhng

ng dng ny vn nhn c nhiu s quan tm ca cc nh khoa hc trn th gii v bc u

t c mt s thnh tu ng lu . Nu kt hp siu m - enzyme c em vo thc t snxut s lm tng tnh kinh t cho cc nh my sn xut do tc dng lm gim thi gian dch ha,

ng ha, ln men, gim lng enzyme s dng, tng ng k hm lng glucose gii phng ra

v gim bt mt vi qu trnh sn xut dn n lm gim chi ph sn xut, tng li nhun. Nh

vy, nhng im ni bt trong qu trnh x l siu m hin nay l:

- Khng s dng ha cht hay ph gia.

- n gin, nhanh chng v c ngha v mt kinh t.

- Khng c bin i ln v cu trc ha hc, c bit v c tnh ca tinh bt.Nc ta l mt nc nng nghip do c ngun tinh bt kh di do nhng nn cng nghipsn xut thc phm vn cn thc hin bng th cng l ch yu. V vy vic p dng cc binphp k thut hin i nh siu m chng hn s gp phn thc y s pht trin ca ngnh cngnghip thc phm ni ring v ngnh cng nghip ni chung. T s lm thay i nn kinh tnc ta t xu khu cc sn phm th l chnh sang xut khu cc s phm gp phn em li linhun kinh t cao v nng cao i sng nhn dn.

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6. C. Aparicio, P. Resa, L. Elvira, A.D. Molina-Garca, M. Martino, P.D. Sanz,Assessmentof starch gelatinization by ultrasonic and calorimetric techniques, Journal of Food

Engineering 94 (2009) 2952997. Farid Chemat, Zill-e-Huma, Muhammed Kamran Khan,Applications of ultrasound in

food technology: Processing, preservation and extraction, Ultrasonics Sonochemistry 18(2011) 813835

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15. Samir Kumar Khanal, Melissa Montalbo, J. (Hans) van Leeuwen, GowrishankarSrinivasan, David Grewell , Ultrasound Enhanced Glucose Release From Corn inEthanol Plants, Biotechnology and Bioengineering, Vol. 98, No. 5, December 1, 2007

16. Saoharit Nitayavardhana, Sudip Kumar Rakshit, David Grewell, J. (Hans) van Leeuwen,Samir Kumar Khanal, Ultrasound Pretreatment of Cassava Chip Slurry to EnhanceSugar Release for Subsequent Ethanol Production, Biotechnology and Bioengineering,

Vol. 101, No. 3, October 15, 200817. Wenjian Chenga, Jianchu Chena, Donghong Liua, Xingqian Yea,, Fansheng Keb,

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