During processing of dairy products, volatile aromacompounds may be lost due to evaporation or thermaldegradation.
Traditional methods of recovery of aroma compounds:distillation, gas stripping, solvent extraction. But theyinvolve high temperature, high energy consumption orintroduction of other chemicals.
Pervporation - no damage to aromas, no additives, goodselectivity to aromas.
Mass transport mechanism: solution-diffusion model
Pervaporation setup
Conclusions
Recovery of aroma compounds from dairy products by pervaporationBoya Zhang1 and Xianshe Feng1, *
1 Membrane Separation Laboratory, Department of Chemical Engineering, University of Waterloo, Waterloo, ON, Canada N2L 3G1
Acknowledgements
Background
Motivation
0
1
2
3
4
5
0 500 1000 1500 2000 2500 3000
Aro
ma
flu
x,
g/(
m2.h
)
Aroma concentration in feed, ppm
Nonanal
Diacetyl
Hexanoic acid
Indole
Dimethyl sulfone
(b)
0.1
1.0
10.0
100.0
1000.0
10000.0
2.9 3.0 3.1 3.2 3.3 3.4 3.5
Perm
eati
on
flu
x, g
/(m
2.h
)
1000/T, K-1
50 500 1000 2500
Diacetyl concentration in feed, ppm
} Water
Diacetyl}
(a)
0.1
1.0
10.0
100.0
Rati
o o
f fl
ux,
dri
vin
g f
orc
e o
r
perm
eab
ilit
y a
t 65 ℃
an
d 2
5 ℃
J65℃/J25℃DF65℃/DF25℃P65℃/P25℃
0.0
0.3
0.6
0.9
1.2
1.5
0 200 400 600 800 1,000
Mass
of
aro
ma
co
mp
ou
nd
inth
eo
rgan
icp
hase
of
the
accu
mu
late
dp
erm
eate
,g
Operating time, h
0%
20%
40%
60%
80%
100%
0 100 200 300 400
Reco
very
rate
of
dia
cety
l
Operating time, h
F0/A=226 kg/m2
F0/A=50 kg/m2
F0/A=15 kg/m2
Organophilic membrane
Investigate the effectiveness of pervaporation on recoveryof aromas from dairy solutions.
Polymer used as membrane material: PEBA 2533
Aroma compounds Formula Odor MW (g/mol)
TB (°C) Solubility in water, 25 °C (g/kg)
Esters
Ethyl hexanoate
Pineapple 144 228 0.46
Ethyl butanoate
Pineapple 116 120 5.75
Ketones
2-Heptanone
Banana 114 151 4.3
Diacetyl
Buttery 86 88 250
Acid
Hexanoic acid
Goat 116 206 10.82
Aldehyde
Nonanal Grass 142 191 0.096
Sulfur compound
Dimethyl sulfone
Hot milk 94 240 Miscible
Aromatic compound
Indole
Jasmine 117 253 1.9
Characterization of PV performance
Permeation flux (Ji), g/(m2.h)
Enrichment factor (β)
Ni: permeation rate, g/h
Xi: Aroma concentration in feed, g/g
Yi: Aroma concentration in permeate, g/g
𝛽 = 𝑌𝑖/𝑋𝑖
0
50
100
150
200
250
0 500 1000 1500 2000 2500 3000
Aro
ma
flu
x,
g/(
m2.h
)
Aroma concentration in feed, ppm
2-Heptanone
Ethyl butanoate
Ethyl hexanoate
(a)
Effect of feed concentration
0
5
10
15
20
25
30
0 500 1000 1500 2000 2500 3000
En
rich
men
tfa
cto
r
Aroma concentration in feed, ppm
Diacetyl
Hexanoic acid
Indole
Dimethyl sulfone
(b)
0
50
100
150
200
250
300
0 500 1000 1500 2000 2500 3000
En
rich
men
tfa
cto
r
Aroma concentration in feed, ppm
Ethyl butanoate
Ethyl hexanoate
2-Heptanone
Nonanal
(a)
Effect of temperature
0
5
10
15
20
25
15 25 35 45 55 65 75
En
ric
hm
en
t fa
cto
r
Temperature, ºC
50 5001000 2500
Diacetyl concentration in feed, ppm
Arrhenius-type equation:
J0: preexponential factor for flux,
g/(m2.h);
R: universal gas constant，J/(K.mol); T: absolute temperature, K.
Reference
𝑃𝑖 =𝐽 𝑖𝑙𝑖
𝛾𝑖𝑋𝑖𝑝𝑠𝑎𝑡 −𝑌𝑖𝑝
𝑝
𝑙𝑖: membrane thickness, μm𝛾i: activity coefficient 𝑝𝑠𝑎𝑡: saturated pressure, Pa𝑝𝑝: permeate pressure, Pa
Ca,
ppm
Diacetyl-water
EJa EPa EJw EPw
50 27.3 -16.4 45.2 1.6
500 46.6 3.1 43.3 -0.3
1000 52.0 8.6 42.4 -1.2
2500 55.0 11.6 43.5 -0.1
Batch pervaporation
0%
20%
40%
60%
80%
100%
0 3 6 9 12 15
Rec
ove
ryra
te
Operating time, h
Hexanoic acidDiacetyl
Ethyl butanoate
2-Heptanone
Ethyl hexanoate
Feng and Huang’s model (well mixed binary feed):
t: operating time, h;
F0: initial feed amount, g;
A: membrane area, m2;
X0: initial aroma concentration in feed, g/g
Initial feed amount: 500 g;Initial feed conc.: 320 ppmfor ethyl hexanoate;
2500 ppm for other aromas;
Temperature: 36 ℃
So: aroma solubility in water, g/g;
Sw: water solubility in aroma, g/g.
When aroma concentration in accumulated permeate reachesaroma solubility in water, phase separation occurs.
Ethyl butanoate
2-Heptanone
Ethyl hexanoate
The ratio of initial feed mass (F0) and membrane area (A) affect recovery efficiency.
To achieve a 100% recovery,
F0/A = 226 kg/m2, t = 381 h;
F0/A = 50 kg/m2, t = 84 h;
F0/A = 15 kg/m2, t =17 h.
Effect of non-volatile dairy components on PV
Ethy
l hex
anoa
te
Nona
nal
Ethy
l buta
noate
2-Hep
tanon
e
Hexa
noic
acid
Indole
Dime
thyl s
ulfon
e
Diac
etyl
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
Norm
aliz
ed e
nrichm
ent
facto
r
NaCl 2 wt% Lactose 2wt%
Protein 2 wt% Fat 2 wt%
0 2 4 6 8 10 12 14 16 18 20 22 24 260
50
100
150
200
250
Without non-volatile components
Whey protein 3.5 wt%
Fat 3.5 wt%
NaCl 2 wt%
Lactose 5 wt%
To
tal flu
x, g
/(m
2.h
)
Time, h
1. With an increase in feed aroma concentration ortemperature, aroma fluxes increase rapidly.
2.The recovery of aroma compound from its aqueous feedsolution is influenced by F0/A for a given period of batchoperating time.
3. Lactose, whey protein and milk fat in feed negativelyaffect the pervaporative recovery of aroma compounds,due to the hydrophobic interaction between these non-volatile compounds and aromas. NaCl positivelyinfluences the recovery of more hydrophobic aromacompounds.
Feng, X., Huang, R.Y.M., 1992. Separation of isopropanolfrom water by pervaporation using silicone-basedmembranes. J. Memb. Sci. 74, 171–181.
Parliment, T.H., McGorrin, R.J., 2000. Critical flavorcompounds in dairy products, in: Flavor Chemistry:Industrial and Academic Research. American ChemicalSociety, Washington, D.C., pp. 44–71.
0 2 4 6 8 10 12 14 16 18 20 22 24 260
40
80
120
160
200
240
Enri
chm
ent fa
cto
r of eth
yl buta
no
ate
Time, h
In general, lactose,
whey protein or milk fat
in feed solutions
negatively affected the
pervaporative recovery
of aroma compounds.
NaCl positively
influenced the recovery
of more hydrophobic
aroma compounds.
No concentration polarization or membrane fouling with the
presence of lactose, whey protein, fat and NaCl was observed.
