MC LC

NI DUNG ................................................................................................... 1

CHNG 1:TNG QUAN V SNG SIU M V THIT B ......... 1

I. KHI NIM SNG SIU M ........................................................... 1

II. TNG QUAN V THIT B SIU M ............................................ 4

1. My pht in (Electrical Generator) ............................................... 5

2. B chuyn i (Transducer) ............................................................. 6

3. B phn pht (Emitter) ..................................................................... 7

III. NGUYN L TC NG CA SNG SIU M ...................... 8

1. Hin tng xm thc kh .................................................................. 8

2. Hin tng vi xoy ........................................................................... 9

IV. CC HIU NG VT L V HA HC KHI CHIU SIU M

LN H CHT LNG ........................................................................... 10

1. Hin tng si bng ....................................................................... 10

2. Hin tng v bng ........................................................................ 10

3. Mt s yu t nh hng n kh nng hnh thnh v v bng: ... 10

CHNG 2: NG DNG PHNG PHP SIU M TRONG CH

BIN THC PHM ................................................................................. 12

I. NH HNG LN ENZYM THC PHM .................................. 12

1. Tc ng: ........................................................................................ 12

2. ng dng: ....................................................................................... 13

II. KHUY TRN, NG HA, NH HA ..................................... 14

1. Tc ng: ........................................................................................ 14

2. ng dng: ....................................................................................... 15

III. TC DNG PH BT: ................................................................ 15

1. Tc ng ......................................................................................... 15

2. ng dng: ....................................................................................... 16

IV. QU TRNH SY ......................................................................... 17

1. Tc ng ......................................................................................... 17

2. ng dng: ....................................................................................... 18

V. TRCH LY ......................................................................................... 19

1. Tc ng: ........................................................................................ 19

2. ng dng: ....................................................................................... 19

VI. KT TINH ...................................................................................... 20

1. Tc ng: ........................................................................................ 20

2. ng dng: ....................................................................................... 21

VII. LM SCH .................................................................................... 22

1. Tc ng: ........................................................................................ 22

2. ng dng: ....................................................................................... 23

VIII. NH HNG LN VI SINH VT TRONG THC PHM ...... 23

1. C ch v hot vi sinh vt ca siu m .......................................... 23

2. ng dng: ....................................................................................... 25

IX. M BO CHT LNG .......................................................... 28

1. Sn xut phomai v u ph ........................................................... 29

2. ung .......................................................................................... 29

3. Bnh m ........................................................................................... 30

4. S ng nht ca sn phm ............................................................ 31

X. R NG, LNH NG ............................................................... 32

XI. CT THC PHM ....................................................................... 33

XII. LC ................................................................................................ 36

1. Tc ng ......................................................................................... 36

2. ng dng ........................................................................................ 36

3. Yu t nh hng qu trnh lc siu m ......................................... 36

4. Mng lc Membrane ....................................................................... 37

TI LIU THAM KHO ........................................................................ 39

BNG PHN CNG

1

NI DUNG

CHNG 1:TNG QUAN V SNG SIU M V THIT B

I. KHI NIM SNG SIU M

Siu m bao gm mt lot cc sng m vi tn s cao, bt u ti 16 kHz, m

l gn gii hn trn ca ngng nghe c con ngi (Elmehdi et al., 2003;

Hecht, 1996). Khi cho mt ngun bc x m thanh vo mt mi trng gn

c khi lng (v d, khng kh, cht lng, hoc cht rn), m thanh lan truyn

dng sng hnh sin. Mi trng phn hi li s lan truyn ca cc sng ny v

cng c th duy tr chng bng cch dao ng n hi. Nhng s rung ng n

hi ca mi trng c hai dng : s ngng t. v s lm thong ( Hecht, 1996;

Knorr v.v...., 2004). Trong thi gian ngng t, nhng phn t ca mi trng b

nn (v d nh khong cch gia cc phn t tch t li), gy nn sc p v mt

ca mi trng tng ( Gallego- Jurez v.v...., 2003; Hecht,. 1996). Trong thi

gian c s lm thong, nhng phn t trong mi trng chuyn dch mt phn, v

th mt v p lc ca mi trng gim (American Heritage, 2002; Hecht,

1996)

McClements (1995) m t su sc trng thi ca sng siu m bng cch quan

st sng t hai gc nhn : thi gian v khong cch. Ti mt v tr c nh trong

mi trng, sng m c dng hnh sin theo thi gian. Nh c th hin Hnh

2.1, khong thi gian t mt bin nh cao n bin nh cao khc l

khong thi gian ca sng hnh sin . iu ny theo vt l c ngha l mi phn

t ti su no trong mi trng (dc theo ng cch u no ) phi ch

khong thi gian trc khi tri qua sng m khc bng vi mt sng m va

tri qua. Tn s f ca ng sin i din cho s ln hon tt mt dao ng trong

mt n v thi gian v l nghch o ca khong thi gian nh trong phng

trnh (2.1) (McClements, 1995):

f = 1/ (2.1)

Hnh 1 - Trng thi ca sng siu m (McClements, 1995)

Khong cch xem xt hiu ng ca sng m ti bt k thi im c nh no

trn cc phn t trong mi trng u su hn. Ti bt k thi im no, bin

ca sng m c nhn thy mnh m bi nhng phn t gn ngun sng m,

nhng nhng phn t su hn trong mi trng tri qua sng m th km mnh

m hn. S gim bin sng m thanh theo khong cch v s suy gim t mi

trng. ng biu din ca khong cch bin sng m tht s l mt ng

hnh sin theo hm s m gim dn, nh th hin trong Hnh 2.2. khong cch

gia nhng nh bin lin tip l bc sng ().Bc sng lin quan n tn

s xuyn qua vn tc nh sng c , theo phng trnh (2.2) (McClements, 1995):

= c/f (2.2)

Hnh 2 - Biu th hin sng m dng hnh sin , khong cch i lp vi bin sng m

Kt qu l , nhng sng siu m di chuyn xuyn qua mi trng vi tc

c th o c bi vic tc dng ln cc phn t (cc ht) ca mi trng.

Nhng sng to dao ng tun hon cho nhng phn t (ht) ca mi trng ti

nhng v tr cn bng . Ti mt thi im no , nhng phn t i ch qua li

cho nhau . S thay i ny gy ra s tng gim t trng / mt v p sut . Do

, ch c mt loi nng lng truyn vo mi trng t sng siu m l c hc ,

n c lin kt vi s dao ng ca cc phn t (ht) trong mi trng (Hecht,

1996).

Vi mong i t c nng lng truyn , nhng qu trnh x l s dng

sng siu m to s khc nhau vi nhng qu trnh x l c s dng sng in t

ph (electromagnetic EM) , nh cc sng t tia cc tm (UV) , nhng sng tn

s v tuyn (radio frequency RF), v vi sng (microwaves MV) ( Kardos v

Luche , 2001), cng tt nh xung in trng (pulsed electric fields PEF).

Sng in t ph (EM) v xung in trng (PEF) to ra nng lng in t ln

mi trng , n c hp thu bi cc phn t (ht) ca mi trng . V d nh

nh sng UV t mt tri c th truyn nng lng nguyn t (4Ev) ph hy

lin kt carbon-carbon . Cc sng in t ph (EM waves) tn ti khi nhng

thnh phn ca nguyn t thay th - c phn in tch dng v in tch m di

chuyn t do trong s chuyn ng khng nh hng . Gia cc phn t mang

in tch m v dng , l ra cc vng in t . Cc vng in t ny i vo mi

trng v tc ng su vo cc nguyn t , cc ion hoc cc phn t trong mi

trng . V d, vi sng xen vo cc phn t phn cc (c mt u dng v mt

u m ) trong mi trng bi vic lm cho chng quay quanh v sp xp thng

hng vi cc vng mang in lin kt vi vi sng . Trong cc l vi sng , cc

phn t nc trong thc phm hp thu nhiu bc x vi sng , v nhng chuyn

ng quay sau c chuyn thnh nng lng nhit (Hecht, 1996). Do ,

sng in t ph (EM) truyn nng lng in t vo mi trng , trong khi sng

m ch truyn nng lng c hc .

Cng rt quan trng ghi nh trong vic so snh cc sng siu m vi

nh sng l ch c sng m khng cha nhng phn t (ht) ca chnh n. Sng

m ch lm gin on s yn tnh ca mi trng to dao ng cc phn t

thuc mi trng . Khng nh m thanh , cc nh vt l hc dng nh lm sng

t mt iu b n cha c gii quyt , sng m lan truyn ng thi c hai

dng l dng tp trung nng lng ging phn t (ht) v nhng sng khng tp

trung . S khc bit ny tr nn hin nhin trong mt khong khng. Khi nhng

khong khng khng cha nhng phn t (ht) mi trng , nhng sng m

khng tp trung khng th truyn bi v chng khng th to s tp trung hay

phn tc cc phn t (ht) .

p lc tc dng ln tai ngi bi nhng m thanh ln l rt nh (

Thit b siu m gm c my pht in (electrical power generator) , b chuyn

i (transducer) v my pht (emitter) , n c nhim v pht sng siu m vo

mi trng (Povey v Mason , 1998). Ngoi tr ting hut t cht lng, chng

s dng nng lng c hc thun ty m khng c pht in sinh ra siu m

(Mason et al. , 1996) , v nhng h thng lm thong khng kh (airborne

systems), chng khng yu cu c my pht (Gallego Jurez et al., 2003; Povey

v Mason, 1998).

Hai loi h thng siu m c bo co thng c s dng trong cng ngh

thc phm , mt loi s dng thanh siu m (horn) nh mt my pht m thanh

v loi khc s dng b (bath) . Loi b c s dng mt cch truyn thng

trong cng ngh thc phm v d dng s dng (Povey v Mason, 1998). Trong

nghin cu gn y , h thng dng thanh siu m c trch dn thng xuyn

nh dng b (Aleixo et al. , 2004 ; Duckhouse et al., 2004; Mason et al. , 1996;

Neis v Blume , 2003; Patrick et al., 2004; Tian et al., 2004). H thng s dng

thanh siu m c s dng tt nh dng b trong nhiu ng dng , t qu trnh

ch bin thc phm dng siu m n vic ra cc b mt ca thit b ch bin

thc phm .

1. My pht in (Electrical Generator)

My pht in l mt ngun cung cp nng lng cho h thng siu m ,

n phi lm cho b chuyn i (transducer) hot ng (Povey v Mason , 1998).

Tm li , mt my pht in sinh ra dng in vi mt mc nng lng c xc

nh r . Hu ht nhng my pht nng lng c hiu chnh mt cch gin tip

qua vic ci t hiu in th (V) v ci t cng dng in (I). Hiu in

th biu th th nng c d tr trong cc electron (o bng volts); cng

dng in biu th bng in tch ca cc electron di chuyn qua mt n v din

tch trong mt n v thi gian (o bng amps); v nng lng c to ra t hai

gi tr trn c biu th trong phng trnh (2.3) (Hecht, 1996).

P = IV [W] , [volt . amps ] , [VA] (2.3)

Cc my pht in c thit k c bit cho siu m ch yu tp trung

trong vic v sinh cng nghip , v nhng ng dng x l , kt ni v nhng

ng dng kh trng, v c tc dng trong khong tn s thp hn (10-40 kHz).

Nhng tn s thp thng khng phi kim tra vic khng ph hy cu trc thc

phm , nhng siu m nng lng c nhiu ng dng tim nng trong qu trnh

ch bin thc phm s trnh by trong phn ny.

2. B chuyn i (Transducer)

Mi h thng siu m bao gm mt b chuyn i nh mt chi tit trung

tm, vai tr ca n l pht siu m thc t. B chuyn i chuyn in nng

(hay c nng, trong trng hp to ting hut cht lng) thnh nng lng m

thanh bng vic rung ng c hc ti nhng tn s siu m (Povey v Mason

1998). Lee et al. (2003) gii thch rng mt b chuyn i c nh km vi

mt my pht in s to ra s chuyn i , v d, 20 kHz c chuyn t in

nng ca my pht thnh nng lng siu m ca cng tn s bng vic rung

ng ti 20.000 chu k c hc trong mi giy .

Povey v Mason (1998) tng kt ba kiu b chuyn i chnh: dn ng

cht lng (liquiddriven), t gio (magnetostrictive), v p in (piezoelectric-

pzt). Nhng b chuyn i c iu khin bi cht lng da trn nng lng c

hc thun ty to ra siu m, nhng nhng b chuyn i t gio v nhng b

chuyn i p in chuyn i in nng v t tnh thnh c nng, nng lng

siu m. Trong khi vic to ting hut trong cht lng lm cho cc qu trnh trn

v ng ha din ra tt hn, ngy nay a s thit b siu m nng lng s dng

nhng b chuyn i p in hay t gio ( Knorr et al., 2004; Povey v Mason,

1998).

Hnh 3 - My pht t gio (Magnetostrictive transducer)

B chuyn i p in (pzt) l kiu chung nht v c s dng trong hu

ht nhng b x l v nhng b phn ng siu m v trch dn thng trong ti

liu tham kho ( Aleixo et al., 2004; Gallego- Jurez et al., 2003;. Povey v

Mason, 1998). B phn bin i p in cng c hiu qu nht, t c tt hn

95% hiu sut, v n c da trn mt vt liu ceramic trong sut p ng

nng lng in.

Hnh 4 - My pht in p (Piezoelectric transducer)

Tm ca my pht in p l mt hoc hai a mng lm t vt liu

ceramic . Vt liu ceramic ny b nn gia hai khi kim loi (mt bng nhm ,

mt bng thp) . Khi in p c t vo ceramic , ceramic s gin ra , ph

thuc vo chiu phn cc , do nhng thay i trong cu trc li ca n . Chnh

s dch chuyn vt l ny lm cho sng m lan truyn vo bn trong dch c

x l .

3. B phn pht (Emitter)

Mc ch ca b phn pht l ta ra sng siu m t b chuyn i vo

trong mi trng. Nhng my pht cng c th hon thnh vai tr ca vic

khuych i nhng s rung ng siu m trong khi pht ra chng. Hai dng chnh

ca nhng b phn pht l b phn pht dng b v b phn pht dng thanh (v

d, nhng u d); nhng my pht dng thanh thng c nh km mt

sonotrode (Povey v Mason, 1998).

Nhng b phn pht dng b thng thng gm c mt b (tank) vi mt

hoc nhiu b chuyn i c gn lin. B cha mu cn x l v nhng b

chuyn i ta ra siu m trc tip vo trong mu (Povey v Mason, 1998).

Trong h thng dng thanh , mt thanh c gn vi b chuyn i n b

khuych i tn hiu v truyn vo cho mu . u ca thanh , thng c gn

ring bit c bit nh l mt sonotrode, pht ra sng siu m vo trong mu .

Hnh dng ca thanh to nn ln ca s khuch i . Do , cng pht ra

siu m c th c iu khin bng cch la chn nhng thanh c hnh dng

khc nhau . S khc bit chnh trong thit b c s dng trong phng th

nghim so vi thit b cng nghip trn th trng l loi b phn pht. Nhng b

phn pht mnh hu nh khng b gim dn cht lng sau nhiu gi s dng

c yu cu trong sn xut thc phm

III. NGUYN L TC NG CA SNG SIU M

1. Hin tng xm thc kh

Khi sng siu m c truyn vo mi trng cht lng, cc chu trnh ko

v nn lin tip c to thnh. Trong iu kin bnh thng, cc phn t cht

lng rt gn nhau nh lin kt ha hc. Khi c sng siu m, trong chu trnh

nn cc phn t gn nhau hn v trong chu trnh ko chng b tch ra xa. p

lc m trong chu trnh ko mnh thng cc lc lin kt gia cc phn t v

to thnh nhng bt kh nh. Bt kh tr thnh ht nhn ca hin tng xm thc

kh, bao gm bt kh n nh v bt kh tm thi

Bt kh n nh l ngun gc ca nhng bong bng kh nh, kch thc

ca chng dao ng nh trong cc chu trnh ko v nn. Sau hng ngn chu trnh,

chng tng thm v kch thc. Trong sut qu trn dao ng, bt kh n nh c

th chuyn thnh bt kh tm thi. Sng siu m lm rung ng nhng bt kh

ny, to nn hin tng sc sngv hnh thnh dng nhit bn trong cht lng.

Bt kh n nh c th li ko nhng bt kh khc vo trong trng sng, kt

hp li vi nhau v to thnh dng nhit nh

Cc bt kh tm thi c kch c thay i rt nhanh chng, ch qua vi chu

trnh chng b v ra. Trong sut chu trnh ko/nn, bt kh ko gin v kt hp li

cho n khi t c cn bng hi nc bn trong v bn ngoi bt kh. Din

tch b mt bt kh trong chu trnh ko ln hn trong chu trnh nn, v vy s

khuych tn kh trong chu trnh ko ln hn v kch c bt kh cng tng ln

trong mi chu trnh. Cc bt kh ln dn n mt kch c nht nh m ti

nng lng ca sng siu m khng duy tr pha kh khin cc bt kh n

tung d di. Khi cc phn t va chm vi nhau mnh lit to nn hin tng

sc sng trong lng cht lng, kt qu l hnh thnh nhng im c nhit v

p sut rt cao (5000oC v 5x104kPa) vi vn tc rt nhanh 106 oC/s

Hin tng xm thc kh m u cho rt nhiu phn ng do c s hnh

thnh cc ion t do trong dung dch; thc y cc phn ng ha hc nh c s

trn ln cc cht phn ng vi nhau; tng cng phn ng polymer ho v

depolymer ha bng cch phn tn tm thi cc phn t hay b gy hon ton cc

lin kt ha hc trong chui polymer; tng hiu sut ng ho; h tr trch ly cc

cht tan nh enzyme tt bo ng vt, thc vt, nm men hay vi khun; tch

virus ra khi t bo b nhim; loi b cc phn t nhy cm bao gm c vi sinh

vt

Hnh 5 - Qu trnh hnh thnh, pht trin v v ca bt kh

2. Hin tng vi xoy

Sng siu m cng cao truyn vo trong lng cht lng s gy nn s

kch thch mnh lit. Ti b mt tip xc gia 2 pha lng/rn hay kh/rn, sng

siu m gy nn s hn lon cc do to thnh nhng vi xoy. Hin tng ny

lm gim ranh gii gia cc pha, tng cng s truyn khi i lu v thc y

xy ra s khuych tn mt vi trng hp m khuy trn thng thng khng

t c

IV. CC HIU NG VT L V HA HC KHI CHIU SIU M

LN H CHT LNG

1. Hin tng si bng

Sng siu m c to ra bng cc dao ng c hc tn s cao hn

15kHz. Khi truyn trong mi trng lng, cc phn t trong trng siu m tri

qua cc chu trnh nn (compression) v dui (rarefaction) v nhng dao ng ny

s lan truyn cho cc phn t k cn. Khi nng lng ln, ti chu trnh dui,

tng tc gia cc phn t s vt qu lc hp dn ni ti v cc l hng nh

trong lng cht lng c hnh thnh. Hin tng trn cn c gi l hin

tng si bng. Nhng bng si ny s ln dn ln bi qu trnh khuch tn mt

lng nh cc cu t kh (hoc hi) t pha lng trong sut pha dn n v khng

c hp th hon ton tr li trong qu trnh nn.

2. Hin tng v bng

Khi chng t n mt th tch m chng khng cn c th hp thu c

nng lng, chng v ra mt cch t ngt v nhanh chng. Trong sut qu trnh

v, nhit v p sut s tng ln rt cao (khong 4000K v 1000atm). Th tch

cht lng b gia nhit l rt nh v nhit nhanh chng b tiu tan, mc d nhit

ti vng ny th rt cao trong vi s. Mt khc, nhit v p sut cao to ra khi

nbong bng s dn ti s to thnh cc gc t do nh l H+ v OH-

3. Mt s yu t nh hng n kh nng hnh thnh v v bng:

Tn s: S hnh thnh cc l hng hay bng kh c th b gii hn tn s

cao hn 2,5 MHz. Kch thc bong bng kh thu c tn s thp hn 2,5

MHz l ti a v do nhng bong bng kh ny s to ra nng lng ln khi v

Bin ca sng siu m: Siu m vi bin cao hn s hnh thnh hin

tng si bong bng vi cng mnh hn. Bong bng c hnh thnh nhanh

hn nhit cao hn do tng p sut hi v gim sc cng. Tuy nhin sc cng

hi cao hn s lm yu i cng n bong bng. nht ca cht lng cng

nh hng n hin tng si bong bng

nht ca mi trng: Trong mi trng c nht cao, s lan truyn

ca cc phn t trong trng siu m bcn tr v do lm gim mc si

bong bng. Trong trng hp ny, siu m c tn s thp hn v nng lng cao

hn c kh nng xuyn thu vo thc phm tt hn l siu m c tn s cao hn

CHNG 2: NG DNG PHNG PHP SIU M

TRONG CH BIN THC PHM

I. NH HNG LN ENZYM THC PHM

Tc ng ca sng siu m n enzyme: sng siu m khng ch c kh

nng lm tng hot tnh enzyme, v hot enzyme m trong mt s trng hp

hot tnh enzyme khng h b thay i

1. Tc ng:

a) Tng hot tnh enzyme

nng lng tng i thp, khi m cc tc ng vt l t ra u th hn

cc tc ng ho hc th sng siu m c tc dng lm tng hot tnh ca

enzyme. Nh qu trnh si bng m tc chuyn ng ca cc phn t nhanh

hn dn n tng kh nng tip xc ca c cht n trung tm hot ng ca

enzyme lm tng hot tnh ca enzyme:

i vi ch phm enzyme, sng siu m lm tng hot tnh ca

nhm enzyme hydrolase do lm tng s o trn t :

Hnh thnh phc cht hot ng enzyme-c cht

Cc cht khuych tn tt hn

Gim s kt t enzyme.

i vi enzyme thu phn dng th, sng siu m c tc dng,

ph v t bo, gip enzyme thot ra ngoi t bo, tip xc vi c cht d dng

hn v do hiu sut thu phn s cao hn.Thc y qu trnh trao i cht,

sinh tng hp nhiu enzyme hn

Tu vo bn cht ca enzyme m sng siu m s tng hot tnh ca

chng nng cao hay thp; s thay i cc thng s ti u nh nhit , pH

b) V hot

Di tc ng ca sng siu m, enzym b bt hot do s bin tnh ca

protein l ch yu bng cch to cc gc t do t cc phn t nc (ha hc)

hoc lc ct do s hnh thnh v sp ca cc bt bng (vt l)

Ha hc: nng lng cao, sng siu m v hot enzyme ch yu

thng qua tc ng ho hc. Cc gc t do to thnh t s phn ly nc: H2O

OH- + H

+ tng tc vi enzym, chuyn enzym thnh gc t do mi v do

lm thay i cu trc ca enzyme. S thay i din ra ngay ti trung tm hot

ng v mt s im nm ngoi trung tm hot ng lm v hot enzyme

Vt l: Cc vi tia cht lng c to thnh t s v bt i xng

ca bt kh, lc ko trong lng cht lng v nhng vi xoy to thnh lm xo trn

mi trng xung quanh enzym, ph v tnh nguyn vn trong cu trc protein.

Gradient p sut cao lm cho phn t protein b v ra thnh tng mnh v

gradient nhit ln c th b gy cc lin kt hydro trong phn t protein, gy

tng tc k nc v bin tnh nhit

V hot enzym bng sng siu m ph thuc vo thi gian truyn sng,

pH mi trng, tn s v cng sng, b phn truyn sng, hm lng kh tan

trong mi trng. Vic sng siu m kt hp vi x l nhit nhit ln

gy v hot enzym lm s v hot hiu qu hn

Sng siu m l tc nhn gy v hot enzyme khng thun nghch. Sau

mt thi gian bo qun, nhng enzyme c x l khng ti hot tr li.

c) Khng tc ng n hot tnh enzyme

Chun b ch phm enzyme: Kh nng gy kt t enzyme trn nhng bong

bng kh khin sng siu m o trn lm tng tnh ng nht trong ch bin

thc phm m khng lm mt i hot tnh ca enzyme c li

2. ng dng:

Vi ch phm -amylase

Tng hot tnh enzyme: sng siu m mt 0.35 W/ml lm tng

hot tnh enzyme nng c cht thp

Gy v hot enzyme: sng siu m tn s khng i 30 kHz v

nng lng cc i 50 W gy v hot enzyme do to thnh nhng gc OH-- tn

cng vo cc n v tyrosine trong phn t protein(ngha l chng khng h tn

cng vo trung tm hot ng ca enzyme) ;

Khng gy nh hng n hot tnh enzyme: Sng siu m cng

150 W/cm2 truyn trong 3 pht 20oC li khng gy nh hng g n hot

tnh enzyme do cc gc t do c to thnh tng tc vi cc n v cysteine

nm ngoi trung tm hot ng ca -amylase v do ch lm -amylase kt

ht li vi nhau

Rau qu, nc p rau qu, sa:

Pectinmethylesterase: Pectinmethylesterase ( PME ), mt loi

enzyme trong thc vt gy s thy phn pectin gim s n nh b mt v gim

nht do chui pectin suy thoi .

Polyphenoloxidase l mt enzyme c cha ng gy ra mu nu

trong tri cy ti v sn phm rau qu nh cc loi nc p

Peroxidase: peroxidase (POD) gy mi kh chu h hng v mu

nu sc t. pH =7 200C cho thy cc enzym peroxidase c th b c ch 90 %

khi chiu siu m trong 3 gi.

S gim hot tnh ca enzyme peroxidase do tc ng ca siu m

c gii thch bi s phn tch nhm heme (prosthetic) ca enzyme bi nng

lng bc x siu m ny. cc bt kh nh s pht trin v b v mnh lit. chng

l nguyn nhn gy ra nhng bin i xu lm to thnh mt s mi khng mong

mun v lm rau tri ho nu

Cc enzyme pectin methylesterase t nhng enzyme c trong cam

v c th gy c cho cc sn phm nc p trong qu trnh ch bin v bo qun

Trong sn xut yogurt, phng php siu m gip ln men gim

40% thi gian sn xut

II. KHUY TRN, NG HA, NH HA

Phng php s dng sng siu m cng cao l mt phng php c

hiu qu trong vic khuy trn cc phn t nh, tng kh nng truyn khi

1. Tc ng:

Khi tc dng sng siu m vo cht lng, s to ra l trng xut hin khi

p sut ca sng t n mt gi tr xc nh ti thiu no , gi tr ny c gi

l ngng to l trng. Trong h thng du/nc, qu trnh nh ha xy ra khi

t n ngng ny

Sng siu m s dng trong khong tn s: 18-30 KHz. Di tc dng ca

sng siu m, cc ht phn tn s b tc ng nn v ko xen k nhau lin tc.

Ngoi ra hin tng xm thc kh cng xut hin:

Giai on ko, cc bt hi tr nn cng phng. Giai on nn: th

tch bt hi b gim ti thiu v chng s b v i

S xm thc kh cng gp phn lm gim kch thc ht phn tn

Kch thc ht sau qu trnh ng ha khong: 1-2 micromet

2. ng dng:

Sng siu m c th cung cp mt nng lng cho vic hnh thnh

b mt mi, v th n c th lm cho qu trnh nh ha xy ra ngay c khi khng

dng cht nh ha

Nu bong bng b v ra gn lp bin ca hai cht lng khng tan ln th

sng va chm c to ra c th cung cp s o trn cc lp rt hiu qu

Vi s h tr ca sng siu m, kch thc ht nh tng s nh hn rt

nhiu so vi ht t c bi qu trnh khuy trn c hc cng iu kin

H nh tng to thnh bng phng php s dng sng siu m n nh

hn v qu trnh ny cng cn t hoc khng cn cht hot ng b mt. Do

c p dng trong ch bin mt s thc phm nh:

Khuy trn, ng ha trong nc tri cy, nc st c chua, v

mayonnaise vi th tch c th ln n12.000 lt/gi

ng nht sa: Sa b ti ti sng siu m 20 kHz gim ng k

kch thc git cht bo ln n 81,5%ca git cht bo nh hn 1 m t

c, cc ht cht bo phn b ng u hn so vi phng php ng ha

thng thng

III. TC DNG PH BT:

1. Tc ng

Khi s dng phng php siu m cht lng, cc sng m truyn t b

mt vo mi trng lng dn n lun phin p sut cao (qu trnh nn) v p

sut thp (qu trnh gin) theo chu k. Trong chu k p sut thp, sng siu m

c th to ra bong bng chn khng nh hoc khong trng trong cht lng. S

lng ln cc bong bng nh to ra mt tng din tch b mt bong bng ln.

Cc bong bng c phn phi tt trong cht lng. Kh ha tan di c vo cc

bong bng chn khng (p sut thp) thng qua din tch b mt ln v tng kch

thc ca cc bong bng

Cc sng m h tr s va chm v s hp nht ca cc bong bng lin k

dn n s tng trng mnh ca cc bong bng. Sng m cng s gip lm rung

bong bng ra khi b mt v s p bong bng nh di b mt cht lng xuyn

qua b mt v gii phng cht kh ra

C ch ph bt ca sng siu m lin quan n:

Chn khng c to nn trn b mt bt bi p sut m thanh cao

Va chm ca cc dao ng p sut trn b mt bt

S cng hng ca cc bong bng bt to nn s ma st lm nhp

cc bng bt vi nhau

Qu trnh to l hng bi sng siu m

S tn nh hay s phun t b mt mng cht lng

2. ng dng:

Trong mt s trng hp, s to bt c xem l qu trnh khng mong

mun trong ch bin thc phm nh bt sinh ra trong qu trnh ln men c th

lm gim nng sut bn kn men, gy tp nhim, gy tr ngi cho cc qu trnh

sau, s dng trong nc tri cy, nc st hoc ru vang, gim tng trng

vi khun v tng thi hn s dng

Hnh 6 - Thit b siu m ph bt trong sn xut

IV. QU TRNH SY

1. Tc ng

Qu trnh sy kt hp sng siu m c th tin hnh nhit thp hn

nhng phng php thng thng lm gim kh nng gy oxi ha v h hng

nguyn liu bi cc phn ng ha hc nhit cao

Khi dng sng siu m c cng cao tc ng n vt liu cn sy, n

di chuyn xuyn sut mi trng rn to ra mt lot cc qu trnh nn v dn

nhanh v lin tc. Nhng lc ny cao hn sc cng b mt vn duy tr m bn

trong cc mao qun ca vt liu, c th gip hi m di chuyn d dng. Sng siu

m to ra cc l hng thun li cho vic di chuyn m mnh m. Tng tc

truyn nhit gia cht rn c gia nhit b mt v cht lng

Hnh 7 - So snh gia phng php sy siu m vi phng php sy bng hi nng (Comparison between contact Ultrasonic and hot-air drying)

2. ng dng: Sy cc loi rau, c, qu v nhiu thc phm khc vi

mc ch s dng, bo qun, tng hng v

Mt s loi rau (nm, gi, sp l) khi sy siu m c c tnh hydrat ha

li tt hn

Chui sy siu m trc khi sy bng khng kh lm thi gian sy gim

n 11%, khng nh hng nhiu n cc m ca chui

Hnh 8 - Thit b siu m sy c rt

V. TRCH LY

1. Tc ng:

To ra p lc ln gip thm thu dung mi tt hn v tc ng n t bo vt liu

Tng kh nng truyn khi ti b mt phn cch

Ph v thnh t bo trn b mt v bn trong ca vt liu, gip thot cht tan

c d dng

2. ng dng: Sn phm tinh khit hn nhng thng ch p dng

quy m nh rt ngn thi gian trch ly, nng sut trch ly cao, dch chit

Tr sau khi c ct nh khong 1- 1,5 mm c cho vo b ngm

vi nc trong thi gian 20-40 pht. Sau tin hnh x l trong b sng siu

m (40W v 500 kHz) khong 15 pht. Tin hnh trch ly tr bng nc nhit

30oC. Lp li qu trnh trch cho n khi nc tr hu nh khng thay i v

mu sc. Thi gian trch ly l 60 pht, tng ng vi khong 3-4 ln trch

C ph khng cafein: Trch ly cafein ra khi c ph c thc hin

trc khi thc hin qu trnh rang v nghin nhm hn ch s tht thot v hng

cng nh mt s hp cht khc, t thay i v trng thi ngoi quan, s thay i

v hng, v ng c chiu hng tt v to sn phm c ph khng hay t c

cafein (p ng xu hng tiu dng: cho ngi b d ng vi cafein hay khng

th s dng c ph vi hm lng cafein cao c, t nh hng n sc khe

nh tng huyt p, tng nhp tim, gim c mt phn v ng)

Trch ly enzyme renin sn xut phomai

Bng: Mt s nghin cu chit xut cc cht c hot tnh sinh hc h tr bng

phng php siu m (Kamaljit Vilkhu v cng s, 2008)

Mc tiu

trch ly

Sn phm Dung mi Phng

php

iu kin

thc hin

Lng gia

tng hiu

sut thu

hi, %

Beta-

carotene

C rt Nc

Ethyl-

acetate

Phng th

nghim,

24kHz, 20-

75 Ws/ml

Xung

quanh

15-25

8-20

Polyphenols B nho Nc Phng th

nghim,

24kHz, 20-

75 Ws/ml

Xung

quanh

11-35

Polyphenols Tr en Nc Phng th

nghim,

24kHz, 8-

10 Ws/ml

90oC 6-18

Polyphenols To Nc Phng th

nghim,

40kHz, 20-

75 Ws/ml

80oC 6

Gingerols Gng CO2 siu

ti hn

Phng th

nghim,

20kHz

160 bar 30

VI. KT TINH

1. Tc ng:

Tc dng quan trng nht ca siu m trn hnh thnh tinh th l s kch

thch to mm, ch yu da vo hin tng xm thc . Trong qu trnh si bt

bng, n c th ph v cc tinh th v ht nhn thnh tinh th nh to mm tinh

th:

Qu trnh kt tinh c th c kim sot bng bin v tn s ca tn

hiu siu m v thi gian tip xc, do cho php kch thc tinh th cng nh

khi no kt tinh xy ra

Kt cu ca sn phm thc phm s b nh hng bi kch thc ca tinh

th ng khng tan phn tn trong vt liu.

nh hng ca phng php siu m n kt tinh ca dung dch ng:

Dung dch Lng tan ra 10 ml Nhit tinh th rn xut hin (oC)

ca nc 50oC (g) iu kin i chng Phng php sng siu m

D-xylose 25 36 46

D-sucrose 18

Mt ong l mt dung dch ng c xu hng kt tinh. y l mt qu

trnh khng mong mun cn phi trnh c trong bc tng th ca qu trnh

sn xut mt ong lng. Phng php siu m gip ha tan cc tinh th

monohydrat D- glucose, loi b cc tinh th xut hin trong mt ong, lm chm

qu trnh kt tinh nhng khng nh hng tiu cc n g c tc dng ng k

trn cc thng s cht lng ca mt ong nh m, dn in hoc pH,

cm quan: mu, hng v ca mt ong, gip gi mt ong trng thi lng lu

hn

Kt tinh ca cht bo c s quan tm ng k trong sn xut chocolate,

b, kem... V d: Phng php siu m 20 kHz v 100 -300 W trn tripalmitoyl

glycerol v b ca cao c nghin cu cho thy n c hiu qu kim sot

kt tinh a hnh ca cht bo v thi gian cm ng c rt ngn

VII. LM SCH

1. Tc ng:

Lm sch cc vt liu cng rn

Kh nng lm sch c cc vt liu cng rn ca phng php siu m

ch yu l do nhng tc ng n mn lin quan n s to bt

Hnh 9 - Thit b bn ra siu m

2. ng dng:

Lm sch dng c, b mt my mc thit b ch bin kh lm sch bng

phng php thng thng. Siu m (40kHz) c th c s dng loi b

mng sinh hc (biofilm), i khi l nguyn nhn gy tch t bi bn trong thit b

thc phm

Siu m kt hp cc cht dit khun lm sch b mt trng t tri p

Trong cng nghip sa, s tch t bn trong cc ng thanh trng, tit trng

l nguyn nhn gy nhim bn, vi sinh vt c th bm vo thnh ng.

VIII. NH HNG LN VI SINH VT TRONG THC PHM

1. C ch v hot vi sinh vt ca siu m

C ch tc ng ca siu m c nhiu nghin cu nhng hin nay vic

a cc gi thuyt v cc kt qu nghin cu cn nhiu vn cha r rng.

Nhng nguyn nhn chnh ca vic tiu dit vi sinh vt l s ph v mng t bo,

cu trc t bo (c xc nhn bi thc t rng mt s vi khun ca cc loi c

bit c kh nng chng xm thc kh hn nhng loi khc trong cc iu kin x

l tng t) bng hin tng xm thc, s bin thin v p sut ca bt kh lm

bin dng mng t bo, co gin mng t bo, rch mng. Tuy nhin phng php

siu m ch lm gim lng vi sinh vt, khng tiu dit hon ton vi sinh vt c

trong thc phm. Do n khng c xem l phng php bo qun thc phm

tt, phng php ny ch c dng h tr cho qu trnh ch bin thc phm.

Nhng t bo c hnh ovan th d b tc ng hn t bo hnh cu. Vi

khun gram(+) c kh nng chu ng tt hn vi khun gram (-). Vi khun hiu

kh bn hn vi khun ym kh v cc bo t th bn vng hn vi sinh vt sng.

Nhiu tc gi cng nhn hin tng xm thc c tc dng n hiu ng

gy cht vi sinh vt.

S ph hy :Siu m gy ra dao ng mnh ln cht lng trong thc phm,

to bt kh. Khi sng m tc ng mnh hn vo lng cht lng, kch thc

cc bt kh tng ln. Bt kh lc ny chu tc ng ca p sut thy tnh, khi

p sut tng, bt b nn p v v sinh ra mt lc c hc tc ng vi sinh vt,

lm rch thnh t bo v vi sinh vt cht.

Lm nng :Khi cc bt kh b n, nhit sinh ra trong lng xung quanh cc l

hng. Th tch ca lng c gia nhit l rt nh v rt nhanh Nhit ca

vng ny c th tng ln rt cao, ln n 50000C, trong vi microgiay. S

tn ti nhit ny c th gii thch t l gy cht dng m ca siu m ging

dng nhit. Nhng a s cc tc gi ni rng nhit sinh ra t siu m khng

gp phn vo hiu ng gy cht t bo v thi gian lm cht 90% vi sinh vt

ca phng php siu m l rt ln.

Sinh ra gc t do :Khi nhit cao t ngt v p sut nn p cc bt kh

tng cng to ra s phn chia hi nc thnh cc gc t do OH v nguyn

t H, cc gc ny cng c tc ng lm v hot t bo ging nh hin tng

to ra cc gc t do peroxid.

Nng lng siu m thng ph thuc vo nhiu yu t :loi vi sinh vt,

enzyme c x l, bin v tn s ca cc tn hiu siu m, thi gian cht

thp phn, th tch thc phm v kiu thc phm. Sc mnh siu m khng c

tc ng nhiu n vic tiu dit vi sinh vt hoc lm bt hot cc enzym tr khi

chng c cng cao (v d, tn s trn 18kHz). Mt s ti liu bo co v hot

vi sinh vt vi tn s thp nh 14kHz, mc d tn s ph bin nht l 20 v

24kHz. Tuy nhin, n c chng minh rng siu m vi tn s thng

khng gim s lng vi sinh vt V th siu m thng c kt hp vi

cc k thut khc nh p sut (manosonication), nhit (thermosonication), hoc

c hai p sut v nhit(manothermosonication) tng thm hiu qu tiu dit vi

sinh vt v v hot cc enzyme.

Mt s nghin cu bng knh hin vi sau khi x l bng siu m- nhit

cho php mt s trong nhng hiu ng cp trc quan st. Vic s dng

hin vi in t qut (SEM-Scanning Electron Microscopy) c hin th cho

L.Innocua sau 30 pht x l 24 kHz, 400W, 120m v 63oC trong sa. Trc

tin, s t on ca thnh t bo c th c quan st thy trong cc t bo b

ph hy. y, t bo cht thot ra ngoi t bo, gy ra ci cht ca vi sinh vt.

Mt c tnh thng thng c quan st trong mt t l cao cc t bo ny l s

hnh thnh ca cc l nh trn lp ngoi ca vi khun. Cc l hng ny, trong

mt s trng hp xut hin l l hng ln, c to ra trong t bo v p lc cao

trong mi trng v s bng n mnh lit ca cc bong bng. Mt s t bo x

l bng siu m- nhit c phn tn thnh nhiu phn nh hn, trng ging nh

cc t bo nh ct thnh cc hnh dng khng t nhin. Cc thnh t bo khng

c xc nh bi mt hoc nhiu bn do s ph v sut trong qu trnh siu m.

Ngoi ra, cc thnh t bo c th l yu hn do x l nhit, lm cho cc t bo

nhy cm hn vi s hnh thnh ca l.

2. ng dng:

Siu m kt hp vi cc phng php bo qun khc trong vic c ch hot

ng, tiu dit vi sinh vt.

ng dng kt hp ca siu m vi nhit v / hoc p lc c ngh cho

cc vi sinh vt sau : Bacillus subtilis, Bacillus coagulans, Bacillus cereus,

Bacillus sterothermophilus, Saccharomyces cerevisiae, v Aeromonas

hydrophila,

Siu m kt hp nhit

Guerrero et al.(2001) bo co khng c thay i v nhy cm ca

Saccharomyces cerevisiae khi siu m v nhit c p dng trong mi

trng canh vi gi tr pH khc nhau. Nhng trong mi trng canh Sabouraud

broth, pH 5.6, vic b sung chitosan lm tng s v hot nm men di tc

dng ca phng php siu m kt hp vi nhit . Cc bo co v vic s

dng siu m v nhit cho thy lm th no kt hp mt s cc yu t nh hng

n cc vi sinh vt khc nhau theo nhng cch khc nhau. V d, Knorr et al.

(2004) bo co rng s v hot Bacillus stearothermophilus v E.coli K12 DH5a

c ci thin vi vic s dng hi nc trc tip a vo qu trnh x l

bng siu m, dn n gim nhit v thi gian qu trnh. Phng php ny l

phng php nhit c h tr siu m (UST- Ultrasound- assisted thermal). Tuy

nhin, mt loi vi sinh vt khc, Lactobacillus acidophilus, n nh hn vi qu

trnh kt hp UST. Theo nghin cu ca Guerrero et al. (2001) vi S.cerevisiae

cho kt qu tt: cho thy mt hiu qu ng b gia nhit v siu m trong v

hot nm men. Hn na, khi nhit thng xuyn duy tr cc gi tr di gi tr

gy tiu dit, s gia tng cng ca sng siu m l gi tr quan trng nht

trong v hot cc vi sinh vt

Siu m kt hp p sut

Trong k thut siu m, mt lnh vc mi gi l mano- sonication hin

ang c th nghim, trong vic s dng p lc trung bnh v cao, kt hp

vi siu m lm gim mt cch hiu qu mc ban u ca s lng vi sinh

vt. Mt s cc vi sinh vt c nghin cu nhiu nht trong k thut khng s

dng nhit c gi l vi sinh vt gy bnh ni bt, chng hn nh E. coli,

Salmonella v Listeria monocytogene, v tm nh hng quan trng ca chng

trong vi sinh thc phm v tc ng ln s an ton ca thc phm. Cc bo co

cho thy nhng ci tin trong v hot E.coli qua vic kt hp phng php siu

m v p sut cao, cng tt nh vic s dng kt hp nhit, m thanh , p sut,

t c s gim hot tnh enzime ca mt s vi sinh vt gy bnh a nhit V

vy, v d, s dng p sut trong qu trnh x l bng siu m lm tng t l

ngng hot ng ca vi sinh vt trong mt lot cc vi sinh vt, ngay c nhit

di nhit si ca mi trng. Hnh 6.2 cho thy hiu qu ca qu trnh ny

nhit thp khi p lc thay i 0-400 kPa. Tt c cc qu trnh ny c

nghin cu v c m t trong chiu su ca mt s nh nghin cu (Ordonez

et al 1984;.. Raso

v cng s nm

1998;. Manas v

cng s nm 2000;

Manas v Pagan

2005).

Hnh 10 - Hnh 6.2 D-gi tr ca cc vi khun khc nhau c x l bng siu m (20 kHz, 117 mm bin ) 40C khi p lc thay i 0-400 kPa.

Siu m kt hp nhit v p sut

Nhng kt qu ca mano-thermo-sonication (siu m, nhit, p sut) p

dng trn bo t B.subtilis cho thy, khi p sut tng ln, kt hp vi nhit v

siu m, kh nng v hot c nng cao. Tuy nhin, khi qu 500kPa, p lc

khng cn l mt yu t quan trng bi v kh nng v hot khng tng ln,

khng c tc dng hn na trong vic v hot bo t c quan st di cc iu

kin th nghim (70oC, 117m v 20kHz)

Siu m kt hp nhit, p sut v pH

Raso v Barbosa- Casnovas (2003) bo co rng vic s dng siu m, p

sut v nhit cng vi hot ca nc thp l mt s kt hp tt cho vic gim

s lng vi sinh vt trong thc phm. . Tuy nhin vic s dng siu m vi hot

ca nc cao cng cho kt qu tng t v hot nc cao c ngha l s

hin din ca nc t do trong mi trng cao, lm tng s to thnh cc gc t

do v s phn hy ca cc phn t nc c to ra bi cc sng m thanh, tng

tnh gy cht ca cc vi sinh vt .

Tuy nhin nh hng ca pH c v l t quan trng hn khi kt hp vi

siu m, v ch c mt vi bo co tp trung vo hiu qu ca n. Jimenez-

Fernandez et al. (2001) nghin cu tc ng ca pH trong Aspergillus flavus

trong sut qu trnh x l bng siu m kt hp vi nhit, ty thuc vo cc iu

kin khc ca mi trng nh aw, nh hng do pH c tm thy l c lin

quan ch trong mt s trng hp. Khi aw khng i v pH c gim, cc gi

tr D thp hn, nhng khi pH khng i, gi tr D thp hn t c vi gi tr

aw cao nht (0,99).

Bo qun mt, mt cam hoc lp ph trn b mt, v d nh cho kem, nc

tri cy v nc st, cc sn phm tht, sa.

V d : ng dng ca siu m dng trong nc p tri cy v nc st

ko di thi gian bo qun. Hin nay, bo qun bng cch s dng nhit cao

trong khong thi gian ngn (thanh trng) vn l phng php x l ph bin

nht cho vi khun nhm ko di thi gian s dng . V tip xc vi nhit cao,

phng php nhit ny thng bt li cho nhiu sn phm thc phm. Di xc

tc ca phn ng nhit, cc cht mi c to ra, s thay i cc phn t cng

nh s bin dng ca cu trc thc vt v ng vt do lm gim cht lng

ca chng. V vy, x l nhit c th gy ra nhng thay i khng mong mun

v gi tr cm quan, tc l cu trc, hng v, mu sc, mi, v cht dinh dng,

tc l vitamin v protein. Siu m l phng php phi nhit x l thay th hiu

qu.

Nhit sinh ra do s to bt v to ra cc gc t do c th gy bt hot cc

enzym bi siu m (El'piner 1964). mc thp, siu m ch lm thay i cu

trc v kh nng trao i cht ca t bo m khng ph hy ca chng. Hot

ng ca peroxidase, c tm thy trong hu ht tri cy ti, tri cy cha luc

(unblanched) v rau qu. c bit peroxidase c th kt hp vi siu m tng

hng v ng thi gim ng k sc t mu nu ca tri cy.

Tr hon s thi ra tri cy v duy tr cht lng qu.

V d, siu m c s dng ti nhng tn s khc nhau (ti a 59kHz)

v nhit 20oC x l du ty ngm trong nc. S thi ra c tr hon

v s lng vi sinh vt gim. cng ca qu v tng cht rn ha tan, chua

v hm lng vitamin C cng c gi li sau khi ch bin.

IX. M BO CHT LNG

Siu m th hin hu ch trong vic kim sot cht lng ca sn phm

thc phm. Trong siu m cng thp c s dng nh gi cht

lng ca cc qu b,xoi v da hu theo chn bng cch nh gi cc thng

s siu m nh vn tc v gim m lin quan n cc c tnh vt l ca mi

trng. Cht lng ca tht b, tht g, c tuyt, tht ln, sa, ru vang, cc

dung dch ng v cc loi du c thm nh cc thng s siu m, bng

cch p dng l thuyt v trng thi sng nh th no (v d, vn tc v gim

m) lin quan n cc thnh phn vt l ca mi trng. Kt cu ca sn phm

nh phomai, rau c nu chn v chn ca tri cy, tt c c xc nh bng

vic s dng sng siu m.

1. Sn xut phomai v u ph

Sn xut phomai bao gm cc cng on khc nhau nh ng t, tch

huyt tng, p mui v chn. Siu m cng thp c s dng

theo di cc giai on khc nhau ca qu trnh. V d, trong vic nh gi cc vt

nt bn trong do qu trnh ln men khng tt v trong vic xc nh thi gian

ng t ti u. Ngoi ra, cc thnh phn v cu trc ca hng trm loi phomai

trn th gii c th c nh gi bng cch k thut khng gy ph hy ny

ci thin trong ng gi v lu tr .Cng vi vic gim st cc phomai khi chng

c sn xut, siu m c trc tip tham gia vo vic to ra loi mm bng

cch thc y s ng t ca protein v du.

Siu m tn s cao cng c s dng nh gi cht lng ca u

ph trong sut qu trnh sn xut. u ph l mt dng gel da trn nc vi

thnh phn ch yu ca protein u nnh; cht lng ca n ph thuc rt nhiu

vo cu trc cui cng ca sn phm. Siu m c th c s ng gim st

s pht trin ca cu trc u ph trong qu trnh ng t. S truyn sng siu

m qua cu trc ca gel ca u ph c cung cp thng tin v ton b qu

trnh, nh trong trng hp lm phomai, lin quan n vic dng cc thng s

kh bin ca siu m hot ha enzime trong sa trong sut qu trnh ng t.

2. ung

Mt s ung chng hn nh sa, nc p tri cy v ru to khng

ln men s t c cc tiu chun thanh trng nh s dng siu m cng

cao; nhng siu m cng thp cng c th hu ch cho mc ch nh gi

cht lng. Siu m c s dng bi kh (loi b oxy) trong nc p cam,

chng minh rng hm lng vitamin A cui trong sn phm cao hn trong sut

thi gian lu tr nc tri cy c siu m so vi nc tri cy theo

phng php x l nhit thng thng. Trong mt nghin cu khc, hm lng

limonin, nhng cht mu nu v mu sc c nh gi trong nc cam sau khi

x l bng siu m (500kHz; 240W; nhit thp, 5 v 14oC), tm kim nhng

thay i th yu ca nhng c tnh ny trong sn phm. Siu m c s

dng thnh cng x l nc qu du ty v ru to cho kt qu tt. Nhng

enzime nh pectin methylesterase v polyphenol oxidase b v hot song song

vi tiu dit vi khun gy bnh. Nhng bin i rt nh trong acid ascorbic v

anthocyanins cng c pht hin vi vic p dng siu m vo u qu trnh

nu. Vic ci thin hiu sut ny khng ch xy ra vi bia m cn tt trong sn

xut phomai, vi s gia tng sn lng sau khi sa thanh trng cng vi siu m

nng lng, th hin li ch kinh t cho cc ngnh cng nghip sa v bia. Ngoi

ra, siu m c th ci thin mt s c im cc sn phm nh mu sc, cu trc

v thi gian bo qun, cng nh duy tr tt mt s gi tr dinh dng ging nh

c tm thy trong cc sn phm ti. Mt v d l qu trnh oxy ha s dng

rng ri trong ngnh cng nghip ung c cn. Qu trnh c s h tr ca

siu m v n tng cng qu trnh oxy ha trong cc sn phm ln men dn to

hng v c trng v lm chn sm. Siu m l 1MHz lm thay i cn bng

ru ester to ra s lm chn r rng trong sn phm. N c s dng cho

cc loi ru vang, ru whisky v ru c cn.

3. Bnh m

Cht lng bnh m lun lun l mt ch v mt yu t m cc nh

khoa hc thc phm ang c gng i mi v ci thin. Hin nay nhng s la

chn khc nhau nh bnh m ng lnh v sy thng hoa c sn trn th trng,

cu trc ca sn phm cui cng l mt thng s quan trng. K thut truyn

thng nh gi cu trc thng lm h hng mu. Siu m cung cp cc li

th l mt k thut khng ph hng mu nhng vn bit c cu to ca bnh

m thng qua cc thng s m thanh. Nghin cu v cu trc vt l ca thc

phm th kh khn v tnh khng ng nht ca thc phm (bnh m) nhng sng

m thanh c th cung cp thng tin v cu trc ca rut bnh m. Cc t bo cha

kh xc nh tnh ng nht v cu trc ca rut bnh m v thng qua mt s

thng s siu m, cu trc vt l c th c nh gi. Vn tc v gim m

ca sng siu m (ti 54kHz) c s dng m t cc yu t cht lng

nht nh ca bnh m. V d, gy ra mt thay i nh trong cu trc ca rut

bnh m sy thng hoa do s thay i tnh dy c (100-300 kg/m3) c nh

gi, cho thy kch thc v hnh dng ca cc t bo cha kh trong bnh m rt

nhy cm vi cc php o siu m, trong khi bin tnh hiu tng tuyn tnh

vi dy c. K thut khng gy ph hy mu ny l mt cng c rt hu ch

trong ngnh cng nghip cc sn phm ng cc trn th gii, cho php cc nh

sn xut hiu c cu trc ca sn phm cui m khng cn iu chnh.

4. S ng nht ca sn phm

Mt lnh vc trong m bo cht lng thc phm l cp n vic pht

hin cc vt th l trong sn phm cui cng. Trong mt n lc m bo s an

ton ca thc phm, tt c cc ngnh cng nghip thc phm phi pht hin t m

i vi kim loi, thy tinh, xng v cc vt liu khc m c th c kh nng

xm nhp vo thc phm trong dy chuyn ch bin. Knorr et al. (2004) cho thy

cc vt th l nh thy tinh, nhng mnh nha v vt liu c th c pht hin

trong sa chua, nc p tri cy v nc st c chua bng cc tn hiu siu m

trong mt phn tch thi gian- tn s. Cc vt th ct t nguyn liu nh , thy

tinh, g, nha, xng v nhng mt cu bng thp c pht hin trong

phomai v mt bng siu m m khng ph hy mu ,phng php c nhy

cao thch hp s dng trong mt sn phm ng nht vi su thm d 20-

75mm. Nn xung siu m (UPC- Ultrasonic Pulse Compression) c s dng

pht hin cc bin i trong st ca mt s cht lng, mc cht lng trong

chai dng polymer cha thc ung v cc vt th l trong cc thng cha. y c

th nhng thay i trong cc thuc tnh m thanh ca mi trng, ch yu l s

truyn vn tc v tr khng m hc, c th lin quan n nhng thay i trong

thnh phn ca sn phm thc phm. Siu m lin kt vi khng kh l mt k

thut mi c s dng c lng mc nc trong mt chai nc ung

polymer. Cc t l khi lng cc thnh phn trong thc phm nh syrup nc

qu v ung c cn cng c th c xc nh bng sng siu m v o lng

hm lng ca cht bo bn bo ha cng c th nghim thnh cng vi

siu m. Mc dy c ca mt s loi thc phm bao gm c phomai

Cheddar, tht hp v nc st vit qut, c o bng k thut siu m xc

nh tc m thanh trong sn phm , phng php ny cho kt qu tng t .

Mt ng dng trc tip ca loi siu m ny l trong sut qu trnh ln men,

trong nng ng thay i cho ph hp vi vic to ethanol nm men

hot ng. Nng ethanol v ng c th c c tnh da trn vn tc sng

m i qua mi trng. y quan trng l phi nhn xt cc c tnh ca sng

siu m, chng hn nh tn s v cng , hoc cc thng s m thanh lin

quan n mi trng - nh vn tc, tr khng m thanh hoc mt - phi c

la chn thm nh mt cch cn thn xc nh cc tnh cht c th ca cc

loi thc phm m cc nh nghin cu ang tm kim. Siu m cng ang c

th nghim v kim sot cht lng vi sinh vt: mt s nghin cu thc hin trn

sa ng chai v trng cho thy s to dng m thanh gy ra bi siu m trong

cht lng b nh hng bi cc hot tnh vi sinh vt, do , nhng vi khun lm

thay i cc thng s ha l c th c pht hin thng qua vic s dng sng

siu m.

X. R NG, LNH NG

Siu m nng lng cao c s dng h tr lm r ng tht b, tht

ln vi tn s v cng khong 500kHz v 0.5 W/cm2. Vi bc x siu m ,

cc vn thng gp trong r ng bng vi sng- lm nng b mt- c gim

thiu, trong mu c r ng n su 7.6cm trong khong 2.5h.

Siu m nng lng, vi tn s trong khong 20-100kHz, chng t hu

ch trong vic hnh thnh cc tinh th nc trong lnh ng ca nc, v kch

thc tinh th nc ny c ci thin nn gim thit hi v t bo. C ch

tham gia l xm thc kh, trong cc bong bng c to ra ng vai tr nh

mm cho s pht trin tinh th . Siu m l mt phng php rt hu dng

trong vic kim sot cc qu trnh kt tinh v n lm tng t l to mm v tc

tng trng tinh th, do to ra cc v tr to mm mi. Tc lnh ng ca

khoai ty c h tr bi siu m th rt nhanh, vi cng sut l 15.85 W v thi

gian x l l 2 pht. Trong mt s qu trnh kt tinh, nh trong giai on u ca

lnh ng, siu m ng vai tr rt quan trng bi v n c th thc y qu

trnh. Do kch thc ca cc tinh th nh hn so vi trong lnh ng thng

thng, ng dng cho mt s sn phm nh du ty, kt qu thc t ny gim

thit hi quan trng cho vi cu trc ca sn phm. Mt s nghin cu s dng

siu m c thc hin trn kem que , s bm dnh tt, phn kem tr nn

cng hn so vi sn phm thng thng. Siu m c s dng gim st

qu trnh lm lnh gelatin, tht g, c hi, tht b v yogurt bng cch o thi gian

tip xc ca xung siu m vi b mt lm lnh. Trong cc sn phm ng u, s

chuyn ng ca lp m bng c o bng thi gian ca mt xung siu m.

XI. CT THC PHM

Ct bng siu m c th phn bit vi ct thng thng do c tnh

chuyn ng c bit ca cng c ct, nh s chuyn ng thng thng ca

thit b c chng chp bi rung ng siu m. Ni chung, h thng ct bng

siu m bao gm mt chui cc yu t to ra v truyn rung ng siu m cho

khu vc tch bit (hnh 5.1). My pht hin cung cp mt hiu in th xoay

chiu vi tn s sng siu m mong mun, thng l trong khong 20-50kHz.

Dao ng in ny c chuyn thnh chuyn ng c xoay chiu vi tn s

tng ng thng qua b chuyn i in p. Mt b phn ghp ni chuyn cc

rung ng c hc nh sng m thanh mang cht rn n u sonotrode, sau khi

khuch i hoc suy gim bin . Cc sonotrode hot ng nh mt b cng

hng c hc, m rung ng ch yu theo chiu dc ca trc rung. Cc

sonotrode thm ch c th hot ng nh mt b ghp ni cho mt li dao ct

c lp. m bo n nh nng sut vn hnh my, ton b h thng dao ng

c iu chnh tn s hot ng lin tc.

Dao ct

Ty thuc vo vic lp ca cng c ct vo sonotrode v nh hng ca

cnh ct so vi trc rung ng, c ba cu hnh chnh c th c phn bit:

Trc rung chnh v trc chuyn ng ca cc cng c ct l ging nhau,

nhng trc rung chnh phi vung gc vi cnh ct .V d, ct kiu my xn

s to ra ng sut v sc cng trn nguyn liu do s chuyn ng ca

nguyn liu th cung cp cho my c tng cng hoc gim mnh bi

mt ng sut theo chu k bng mt tn s cao (20-50kHz) v mt bin

thp. ng sut v sc cng c s dng trong khu vc ring - ni cnh

c tip xc vi mi vt nt trong sn phm.

Mt hng dao ng vung gc vi c hai trc chuyn ng v trc cnh h

tr tch sn phm khi nhng khong cch m rng do mt hng rung ng

vung gc vi khong cch ca chnh n. S m rng ny gy ra bi nhng

ng sut rt cao ti mi vt nt trong vng ring bit, do tng s truyn

vt ct. Ngoi ra, nhng c ch lin quan cng nh lc ma st hai bn

sn cng c b nh hng ng k.

Khi hng dao ng vung gc vi trc di chuyn, nhng song song vi

thnh phn biu kin thng thng c chng chp bi s chuyn ng rt

nh ca tip tuyn , gy ra chuyn ng ca hai chiu.

XII. LC

1. Tc ng

Lm sch vch lc v trnh bm cu cn.

Sng m siu c tc dng lm tch t cc ht nh v tip theo l to ra s

rung gi mt phn ht dng huyn ph, v th n lm trong dung dch sau

lc. Qu trnh ny c ng dng lc cc sn phm sau khi p nh nc p tri

cy, ung nh lm trong bia.

2. ng dng

Lc rn-lng l mt qu trnh ph bin nhiu ngnh cng nghip ngy

nay. Lc c th c p dng hoc lm r mt cht lng t cht rn hoc loi

b cc cht rn t cht lng. Bn cnh vic tng ng k t l dng chy cht

lng thng qua b lc, ng dng ca siu m cng gip cc b lc sch v ngn

nga nhim (Fairbanks nm 1973;Semmelink 1973). Lc siu m c p

dng cho mt s lnh vc ca ngnh cng nghip thc phm v nc gii kht.

Khi p dng cho cc cht chit xut tri cy v ung, k thut ny c s

dng tng nc p tri cy chit xut t b (Mason v cc cng s. 1996).

ng dng tim nng khc bao gm ng, bia, ru, v cc loi du n

(Brennan, Grandison, v Lewis 2006). V vy, v d, nc c to ra bng cch

chit xut t c ci ng c x l bng vi v lc to ra nc p sch

phc v cho giai on tip theo . Bia c lm sch bng cch lc loi b b

men v trub. Ngoi ra, ru vang v cc loi du n c c lc cc giai

on khc nhau ca sn xut.

3. Yu t nh hng qu trnh lc siu m

Trong mt nh gi m rng , Kyllnen, Pirkonen, v Nystrom (2005)

nghin cu mt s thng s nh hng n hiu qu ca lc siu m nh tn s,

cng nng lng, tnh cht thc phm, vn tc dng chy, v nhit . Nhn

chung, hiu qu ca qu trnh lc cao hn khi tn s siu m c cng thp

hn v cng sut cao. Tuy nhin, siu m rt km hiu qu cho huyn ph c

nng cao nh bn. Theo ngha ny, mt trong nhng yu cu hin ti trong

nhiu ng dng cng nghip l vic x l huyn ph nng cao ca cc ht

mn. K thut lc thng thng l khng tha ng v nhim thng xy ra,

dn n t l lc chm. H thng siu m th nghim l s m t trong hnh

6.5.

Hnh 6.5 S ca

h thng lc h tr siu m

4. Mng lc Membrane

Membrane l mt loi vt liu bn thm cho php s i qua ca mt s

phn t trong khi gi li nhng phn t cn li. Membrane c th phn loi cc

thnh phn da trn kch thc, nng hoc kh nng tch in. Mng c s

dng rng ri trn cng ngh thc phm v cc ngnh cng ngh sinh hc cho c

hai mc ch l phn tch v c c. Nhng ng dng c th bao gm :

Vi lc (MF) sa tng nng caseins.

Vi lc (MF) cc sn phm sa ln men gi li vi khun v bo t.

Siu lc (UF) whey t sa v sa tch kem c c cht kh trc khi

sy phun.

Mng phn ng sinh hc cho nui cy t bo v ln men enzime.

Tng hng v v mu sc.

Nhng phng php membrane i lc tch protein.

Thm thu ngc sn xut nc tinh khit cho cc qu trnh sinh hc

v cho s to hi nc

ng ha.

Phn loi cc loi bia v nc tri cy.

Mng lc membrane thng c cung cp nh nhng ng hoc a

phng. Ngc li, mng cao phn t c th c cung cp trong mt nh dng

xon c hoc dng si rng. Trong mi trng hp, cht lng chy tip tuyn vi

b mt mng ( Hnh 5.5).

TI LIU THAM KHO

http://www.hielscher.com/food_01.htm

http://hal.archives-ouvertes.fr/docs/00/89/57/33/PDF/hal-00895733.pdf

http://www.doko.vn/luan-van/tong-quan-tai-lieu-ve-ung-dung-ky-thuat-sieu-am-

trong-cong-nghe-thuc-pham-277402

http://www.ultrasonics.org/Proceedings_2007_UIA/Gallego_2007_UIA.pdf

http://www.vscht.cz/ktk/www_324/studium/konzervace/pdf/ultrazvuk.pdf

Applications and opportunities for ultrasound assisted extraction in the food

industry Kamaljit Vilkhua, Raymond Mawsona, Lloyd Simonsa, Darren

Batesb

Novel Food Processing : Effects on Rheological and Functional Properties- Jasim

Ahmed, Hosahalli S. Ramaswamy, Stefan Kasapis, Joyce I. Boye

http://digital.csic.es/bitstream/10261/7957/1/ult05004.pdf

http://arrow.dit.ie/cgi/viewcontent.cgi?article=1129&context=schfsehart