Rheological properties of microfluidized oil-in-water emulsions stabilized by
dairy
components
e-~ gembloux ~ facultéuniversitaire
~ dessciences agronomiques
Caroline Va
nd
e
rgh
e
m
,
S
ab
ine Danthi
n
e
,
Cla
u
de Deroann
e
,
C
hris
t
o
p
he B
l
ecke
r
Gembloux Agricultural University, Department cf Food Technology (Head: Prof C.Deroanne)
PassagedesDéportés2,B-5030 Gembloux, Belgium •.Contact e-mail: bleckerc@/sagx.ac.be" URL: http'/ /www.fSagx.ac.belta
Introduction
Recombineddairyemulsions are end products in themselves (culinary crearns,coffee crea mers),orcan beused as ingredients,contributingto the structure ofmore complex products (iœ-cream, cheese, whippedcream). The indusuy of recombined milk productshas notstop10growand the range of recombined emulsions continues ta expand. Reœntly, recombining has expanded itshorizons lO "added value andspecialryproducts" like dairy based ready-to-drink beverages, sportssupplements, cultured milks and fortifiedmilks (recombined dairy emulsionscould be considered as suitable deliveryvehicles for a rangeofnutritionaland functional ingredients).Subsequently,different textures arerequired for the diverserange of products, Interaction ofemulsion drapiers can leadtothe creation of structures in foods and hence10theperception of textures asmeyare consumed(Dalgleish, 2006).Thecomposition ofthe interfacial layer, deterrninedbythe nature of the emulsifier, remarkably influences theproperlies ofemulsions(stability, rheology).The aimoflhiswork wasto invesugate the effectof different commercial dairy components(wheyprotein concentrate (WPC), skimmed milk(SM)andlWOkindsof butrermilk (BM1and BM2)havingdifferentphospholipids contents) on thefinalstructureof microfluidized-emulsions. Oil-in-water emulsionswere characterized byparticle size, microstructure,dynamic rheological rneasurernentsandstability.
Composition analysis ofthe dairy powders
Comoosition (%) WPC SM BMI BM2
Proteins(l) 75.93 ±0.29 37.02 ± 0.17 31.99 ± 0.23 28.14 ±0.24 Fats(2) 5.12 ± 0.14 0.71±0.18 7.44 ± 0.21 12.99 ± 0.10 Phospholipidst" 2.05±0.03 0.23 ± 0.01 2.28 ± 0.02 7.53 ± 0.34
l2I:)cIDaner 9660+ 018 9544+017 9574+004 9615 + 004
Formulation and elaboration ofrecombined creams
Emulsion composition was fixed at 30% (w/w) fat, 2% (w/w) protein. No n-fatdry matter ofthe emulsion was set at 5.91% (w/w) with lactose. The pH of the dispersions was adjusted to6.6.
Anhydrous milk fatwas completely melted at75D
e
and incorporated in the dairy dispersions using an Ultra-Turrax T45atJO000 rpm.Emulsions were then homogenized at 50D
e
by a Microtluidizer M ilOT at400bar.
(I)Kjeldahl, (2)Rose-Goulieb, (3)Total phosphorus dosageoftheextracted lipid
Effect ofmicrofluidization on dairy emulsions
Dmpletsizcmcasurement by
laserüght scattering
Structure of produced cmulsionswas visualizcdbyanoptical microscope
Dynamicviscosityanalysiswas usedto
compare the different creamsamples
Ultra-TIlITlLI
DropletllialDd« SpedfiCJur!an (".J) hua) ana(m2/I)
SM 7.36 tO..25 t.~ Jo0.05
WPC 5.1710.10 L75t0.06
BMI 5.17,.0.09 1.62 10.01
BM2 J.51sO.11 2.J3tO.OS
Emulsions obtained by the Ultra- Turrax showed non aggregated large droplets. At low shear rates, emulsions had a little shear thinning profile. AlI emulsions exhibited quite
low viscosity.
Arepresentative microscopyimage or an emulsioncbtained by theUura-Turrax
Viscosity plottedYS.shear rate profiles
SM(O),BM)(â),BM2(O), WPC (e)
Microtluidized emulsions showed very small
droplets which formed c!usters.
Microtluidization increased the apparent viscosity and produced a change in the rheological behaviour of the emulsions.
However, SM and BMl samples showed a
more shear thinning profile over the entire
shear rate applied indicative of extensive
interaction between particles. MKT"oO.t4iuf
ChllltallianKlt'r Dropld4ialDett'r (1I4.~(JIJ1l) (1II4•l)(j.ua) SM 3O.()6:i.0.22 0.96:i.O.o1 WPC 1.02:00.03 0.75:i.O,03 BMI Il.61,.1.29 0..l6,.0.01 BM2 J~1 tO.25 O." :t.0.().:I Cll.l!llCf wamell'"r$ were oblaincd dircctJy by dlspcn.inC emulsions intheumple cdl 0(the
panjdt J.izranal)~. 0r0pIct wamctcr \o\.'CfC obWned.with s.ampics dlal weredilulCd (1/1)Îna 1%SOS JOIulionbcli:n musuremcnlS.
Representativesmicroscopy imagesor emulsionsobtained bytheMicrcûvidizer
Viscosity ptonedYS.sbearrate profiles SM(O), BM)(â), BM2(O).WPC(e)
AUmicrotluidized emulsions were stable, since thedroplet size considerably diminished.
Oscillationfrequency sweeptestsover afrequencyrange from0.1 to
10Hzatastress of1Pa were peIformedfor microfluidized emulsions
Creaming was monitored with an optical scanning instrument
(TurbiscanMA2(00)
wrc SM BMl BM2
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At low frequencies, the loss modulus (G") is higher than the storage modulus (G') for WPC and BM2 (higher phospholipid content than
BMI) indicating a more viscous than elastic response ofthe system. These emulsions show a weak structure having a more liquid
character.
For extensive tlocculated emulsions (SM and BMI) both moduli increased considerably. The storage modulus is higher than the loss modulus indicating the presence of a gel-like structure.
Conclusions
Bychanging the kind ofthe interfacial material (buttermilk, skim milk, whey protein), the particle-particle interactions can be modified leading
from viscous liquid to untlowable creams.
Further investigation on the qualitative composition of the interface should be led inorder ta gain understanding on the interaction between
particles.
