Degassing Method

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Degassing of carbonated beverages by gas stripping
Oliveira, J.C. *, Gomes, C.S.* and O’Keefe, B. **
* University College Cork, Ireland ** Somex Ltd., Macroom, Ireland

TITLE OF CONFERENCE Copenhagen, Denmark, September 2010
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* Research partly supported by Enterprise Ireland in the framework of the National Development Plan 2007-2014

Background
Degassing is necessary for quality control CO2 interacts with the beverage characteristics Its removal can therefore induce an error insufficient removal excessive removal what else happened to the beverage as a result of the degassing process? saturation in oxygen, nitrogen, etc.

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TITLE OF CONFERENCE, September 2010

Causes
pH increase as CO2 loss causes carbonic acid loss fall of pH due to concentration by loss of water

pH
pH of solution with no CO2

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Extent of degassing
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Outline of the presentation
Thermodynamic equilibrium and the degassing curve Comparison of the robustness of different methods of degassing Importance of the control factors in gas stripping Validation

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O

C

O

CO2 and water
H H O C O O O C O

CO 2 (g ) ⇔ CO 2 (aq)

+

H O

H

CO 2 (aq) + H 2 O ⇔ H 2 CO 3

H 2 CO 3 + H 2 O ⇔ HCO 3 + H 3O + HCO 3 + H 2 O ⇔ CO 3 + H 3O H O H
− 2− +



+
O C O O

H

+
-

-

H O

H

+
H O H ENTERPRISE
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H

H

+
H O TITLE OF CONFERENCE, September 2010 H O

+

-

O

C O

+

CO2 in a beverage
carbonic acid citric acid

CO 2 (aq) + H 2 O ⇔ H 2 CO 3

H 3O + + ca − ⇔ H 2 O + citric _ acid H 3O + + ca 2− ⇔ H 2 O + ca − H 3O + + ca 3− ⇔ H 2 O + ca 2−

H 2 CO 3 + H 2 O ⇔ HCO 3 + H 3O + HCO 3 + H 2 O ⇔ CO 3 + H 3O + − 2−



phosphoric _ acid + H 2 O ⇔ pa − + H 3O + pa − + H 2 O ⇔ pa 2− + H 3O + pa 2− + H 2 O ⇔ pa 3− + H 3O + phosphoric acid
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etc...
TITLE OF CONFERENCE, September 2010

An intricate balance
etc...
HCO 3 − H3O +

CO 2 (aq)

H2CO3

ca −

etc...
HCO 3 − H3O +

CO 2 (aq)

H2CO3

ca −

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TITLE OF CONFERENCE, September 2010

Thermodynamic equilibrium
phosphoric _ acid + H 2 O ⇔ pa − + H 3O +

K1 =

a pa − × a H O +
3

a pa × a w

=

C pa − × C H O +
3

C pa × C w

×

γ pa − × γ H O +
3

γ pa × γ w

Ka1

C pa − = K a1 C pa / C H O + × Γ1
3

Note:

C pa 2− = K a 2 C pa − / C H O + × Γ2
3

C pa + C pa − + C pa 2− + C pa 3−
= total phosphoric acid

C pa 3− = K a 3 C pa 2− / C H O + × Γ3
3
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TITLE OF CONFERENCE, September 2010

Mathematical model
C
H3O+

=C

OH−

+ C − + 2C 2− + c c
ca−

+C
C
OH−

+ 2C

= Kw /C

ca2−

+ 3C
pa

ca3 −

+
pa3 −

H3O+

+C

pa



+ 2C

2−

+ 3C

C

pa−

= K p1Cpa / C
C
pa2−

H3O+

× Γp1
2

 = K p1K p2 Cpa /  C  H O+  × Γp1 × Γp2  3  etc...

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TITLE OF CONFERENCE, September 2010

CO2 removal model
− dn w = Q g dt P (y ws − y wo ) RT
PQ g (y ws − y wo ) n w = n wo − t RT

 P  Hn c   − dn c = Q g  P(n − at ) − y co dt RT  o  g   n c =  n co + (1 − bt ) b−k 
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k b



g(1 − bt ) b−k

TITLE OF CONFERENCE, September 2010

pH degassing curve
2.788 2.786

pH

considering the activity coefficients neglecting ionic strength

2.784

2.782

2.78 pH 2.778 2.776

0.25

2.774

CO2 concentration degassing time
0 2 4 6 8 10 tim e (m in) corrected for ionic strength w ith ideal solution constants 12 14 16 18 20

2.772

0.2

2.77

C CO2 (mol/L)

0.15

0.1

0.05

degassing time
0 0 5 10 15 20 25 30 35 time (m in)

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Optimum degassing point
2.786 2.784 2.782 2.78 2.778 pH 2.776 2.774 2.772 2.77 Real maximum 2.768 0 2 4 6 8 time (min) Real pH ENTERPRISE...
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