Forward osmosis for the concentration of apple juice Netsanet Shiferaw Terefe, Isabelle Desmons, Filip Janakievski, Kirthi De Silva IFOS 2016

Transcription

1 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 1

2 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? P max ~16psi P = <8psi Feed side Draw solution side Milk J w = A π J s = B C Regeneration Water TFC-Thin Film Composite Active Layer 0.2µm nm Support Layer 119.8µm solutes Draw Solution 4 Forward Osmosis Technology Showcase - December 2016 Kirthi De Silva 2

3 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 6 FO of Apple juice 3

4 Experimental Conditions Draw solutions Selection based on GRAS status, osmotic pressure, reverse solute flux NaCl, 2.2M, MgSO 4, 2.4M, MgCl 2, 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 Molarity Density (kg/m 3 ) Relative Osmotic pressure Viscosity (cp) (atm) NaCl MgCl MgSO Osmotic pressure 8 FO of Apple juice 4

5 Effects of draw solute type on flux (20 C) at approximately the same osmotic pressure Flux (L/m 2 h) M NaCl 1M MgCl2 1M 2.4M MgSO MCF 9 FO of Apple juice Effects of draw solute concentration on flux (20 C) Flux (L/m 2 h) M NaCl 2.2M MgCl2 1M MgCl2 1M MCF 10 FO of Apple juice 5

6 Effects of temperature on flux with 2.2 M MgCl 2 as draw solution Flux (L/m 2 h) C 30 C 40 C 50 C MCF 11 FO of Apple juice FO concentration of apple juice with 2.2M MgCl 2 as draw solution Concentration ( Brix) C 50C Time (min) 12 FO of Apple juice 6

7 Reverse solute diffusion-differential increase in juice conductivity over that due to concentration Increase in conductivity (ms/cm) C 30 C 40 C 0 2.4M MgSO M MgCl2 2.2M MgCl2 2.2M NaCl MgCl 2 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 C C C, 40 C Slight but significant reduction in total polyphenol content 14 FO of Apple juice 7

8 Effect of FO on individual polyphenols Polyphenol (mg/l) Untreated control FO 40 C FO 50 C FO 16 C, 40 C Gallic Acid 3, std dev 2.2 Catechin std dev Epicatechin std dev Chlorogenic Acid std dev Phloridzin std dev Quercetin std dev FO of Apple juice Effect of FO on major flavour volatiles Concentration (µg/kg) Ethanol Methyl butanoate Ethyl butanoate Hexyl acetate Acetic acid C 40 C 16 C Significant reduction dependent on processing temperature in hexyl acetate over the first 30 min 16 FO of Apple juice 8

9 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 MgCl 2 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 18 FO of Apple juice 9

10 Thank you AGRICULTURE AND FOOD 10