Forward osmosis for the concentration of
apple juice
Netsanet Shiferaw Terefe, Isabelle Desmons, Filip Janakievski,
Kirthi De Silva
IFOS 2016
AGRICULTURE AND FOOD
Introduction
• Fruit juices are commonly concentrated
• Improve shelf-life stability and off season availability
• Reduce transport and storage costs
• Multi-stage vacuum evaporators commonly used
• High temperature = degradation of juice flavour, colour and
nutritional quality
• Energy intensive
• Forward osmosis potentially better alternative
• Low temperature process- better quality retention
• Reduced operating and capital cost
2 | FO of Apple juice
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Why Apple Juice?
•Apple Juice one of the most consumed
juices in the world
•Most of it processed into concentrate
•World production- ~1.6 million
tonnes per year (2012)
3 | FO of Apple juice
What is FO Technology?
Pmax ~16psi
∆P = <8psi
Milk
Feed side
Draw solution side
Jw = A∆π
Js = B∆C
Regeneration
Water
TFC-Thin Film
Composite
solutes
Active Layer
0.2µm
0.3-0.5nm
Support Layer
119.8µm
Draw
Solution
4 | Forward Osmosis Technology Showcase - December 2016 | Kirthi De Silva
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Research Objectives
• Evaluate the feasibility of FO for the
concentration of apple juice
• Draw solute type and concentration
• Processing temperature
• Study the effect of the process on juice quality
• Colour, titratable acidity
• Total polyphenol content
• Individual polyphenols
• Flavour volatiles
5 | FO of Apple juice
Experimental Set Up
Commercial TFC membrane- 014 m2
Flow rate- 2 L/min
Feed to draw solution ratio- 1:10
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Experimental Conditions
• Draw solutions
• Selection based on GRAS status, osmotic pressure, reverse solute
flux
• NaCl, 2.2M, MgSO4, 2.4M, MgCl2, 2.2M, 1.0 M
• Operating Temperatures
• 20˚C, 30˚C, 40˚C, 50˚C
• FO concentration trials at selected conditions for
quality evaluation
• 40˚C, 50˚C
• Different temperatures on draw solution (40 °C) and feed side
(~16 °C)
7 | FO of Apple juice
Physiochemical properties of the draw solutions
(20 °C)
DS
NaCl
MgCl2
MgSO4
Density
(kg/m3)
Molarity
Relative
Osmotic pressure
Viscosity (cP)
(atm)
2.2
1.0857
1.26496
112.66
1.07
1.1189
1.336123
96.198
2.2
1.449
2.302725
289.679
2.4
1.2574
4.787171
103.393
• Osmotic pressure
8 | FO of Apple juice
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Effects of draw solute type on flux (20 °C) at
approximately the same osmotic pressure
10
9
8
Flux (L/m2h)
7
6
5
4
2.2M NaCl
3
1M MgCl2 1M
2
2.4M MgSO4
1
0
1
1.2
1.4
1.6
1.8
MCF
2
2.2
2.4
2.6
9 | FO of Apple juice
Effects of draw solute concentration on flux
(20 °C)
12
Flux (L/m2h)
10
8
6
4
2.2M NaCl
2.2M MgCl2
2
1M MgCl2 1M
0
1
1.2
1.4
1.6
1.8
MCF
2
2.2
2.4
2.6
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Effects of temperature on flux with 2.2 M
MgCl2 as draw solution
20
18
16
Flux (L/m2h)
14
12
10
8
6
20 °C
4
30°C
40 °C
2
50 °C
0
1
1.5
2
2.5
3
3.5
4
4.5
MCF
11 | FO of Apple juice
FO concentration of apple juice with 2.2M MgCl2
as draw solution
50
45
40
Concentration (° Brix)
35
30
25
20
15
10
40C
5
50C
0
0
60
120
180
240
300
360
420
480
Time (min)
12 | FO of Apple juice
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Reverse solute diffusion-differential increase in juice
conductivity over that due to concentration
3.5
Increase in conductivity (mS/cm)
20 °C
30 °C
40 °C
3
2.5
2
1.5
1
0.5
0
2.4M MgSO4
1.07 M MgCl2
2.2M MgCl2
2.2M NaCl
MgCl2 selected for further FO concentration experiments due to the lower back diffusion
13 | FO of Apple juice
Effect of FO on total polyphenol content
Samples
Average GAE (mg/ml)
std dev
Control
0.664
0.01
40 °C
0.563
0.04
50 °C
0.566
0.02
16 °C, 40 °C
0.607
0.07
Slight but significant reduction in total polyphenol content
14 | FO of Apple juice
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Effect of FO on individual polyphenols
Polyphenol
(mg/L)
Untreated
control
FO 40 °C
Gallic Acid
3,11
0
0
0
std dev
2.2
5.11
FO 16 °C, 40 °C
FO 50 °C
Catechin
6.23
6.55
7.04
std dev
0.12
1.16
2.8
1.7
Epicatechin
13.02
21.5
16.2
21.5
std dev
Chlorogenic
Acid
std dev
1.98
0.2
2.7
0.3
42.8
108.4
111.6
106.1
6.2
2.9
15.9
1.6
Phloridzin
2.52
6.03
6.2
5.6
std dev
0.27
0.27
0.6
0.08
Quercetin
std dev
0.01
0
0
0
0.0
15 | FO of Apple juice
Effect of FO on major flavour volatiles
350.00
300.00
Concentration (µg/kg)
250.00
200.00
Ethanol
Methyl butanoate
Ethyl butanoate
150.00
Hexyl acetate
Acetic acid
100.00
50.00
0.00
0
30
60
180 240 360 420
50°C
0
30
60
180 240 360 420
40°C
0
30
60
180 240 360 420
16°C
Significant reduction dependent on processing temperature in hexyl acetate over the first 30 min
16 | FO of Apple juice
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Conclusion
• This study showed that FO can be used to concentrate apple juice
to 45 °Brix or higher
• The best draw solute among the investigated both in terms of flux
and reverse solute diffusion was MgCl2
• Moderate temperature (30 to 40 °C) significantly improved the FO
process whereas further increase to 50 °C did not have a significant
effect
• Significant changes in quality attributes (colour, TPC, flavour
volatiles) was observed during FO concentration at moderate
temperature
• However, this is mainly due to exposure to oxidative changes during
the long process and will not be expected under commercial FO
process of short duration
17 | FO of Apple juice
Acknowledgement
• Isabelle Desmons
• Filip Janakievski
• Tanoj Singh
• Amanda Bergamin
• Kirthi Desilva
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Thank you
AGRICULTURE AND FOOD
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