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Optimisation and modelling of aroma recovery by pervaporation

Olsson, Jenny LU (2001)
Abstract (Swedish)
Popular Abstract in Swedish

Vid framställning av koncentrerade fruktjuicer utsätts produkten för värmebehandling i form av indunstning och pastörisering. Värme-behandlingen försämrar produktens sensoriska kvalitet, dels eftersom aromerna är flyktiga och snabbt avdunstar, och dels eftersom värmen påskyndar kemiska förändringar av aromämnena. Några viktiga fördelar uppnås dock genom tillverkning av koncentrerade juicer, såsom billigare och mer miljövänliga transporter samt förlängd hållbarhet.



Med membrantekniken pervaporation erbjuds möjligheten att utvinna aromen direkt från den färskpressade juicen. Aromkoncentratet kan därefter återföras till den slutliga produkten. På så sätt kan värmebehandling av... (More)
Popular Abstract in Swedish

Vid framställning av koncentrerade fruktjuicer utsätts produkten för värmebehandling i form av indunstning och pastörisering. Värme-behandlingen försämrar produktens sensoriska kvalitet, dels eftersom aromerna är flyktiga och snabbt avdunstar, och dels eftersom värmen påskyndar kemiska förändringar av aromämnena. Några viktiga fördelar uppnås dock genom tillverkning av koncentrerade juicer, såsom billigare och mer miljövänliga transporter samt förlängd hållbarhet.



Med membrantekniken pervaporation erbjuds möjligheten att utvinna aromen direkt från den färskpressade juicen. Aromkoncentratet kan därefter återföras till den slutliga produkten. På så sätt kan värmebehandling av aromen undvikas.



Syftet med avhandlingen var att modellera och optimera pervaporationsprocessen för utvinning av arom från fruktjuicer, med fokus på äppeljuice. Studien visar att pervaporation är ett lovande alternativ för aromåtervinning från äppeljuice eftersom tekniken erbjuder mycket hög selektivitet vid milda processbetingelser.



Utvinningen av arom kan förbättras drastiskt genom ökad temperatur, ökad flödeshastighet och/eller sänkt permeattryck, vilket måste balanseras mot en större energiåtgång. Eftersom aromerna är värmekänsliga, måste temperaturen fortfarande hållas på en rimlig nivå. Därutöver kan sammansättningen av aromkoncentratet styras genom lämpligt val av processbetingelser. Membranets tjocklek och materialegenskaper har naturligtvis också ett stort inflytande över separationsförmågan.



En modell utvecklades, vilken kan förutsäga hur transporten genom ett membran av modifierat silikongummi påverkas av permeattrycket för karakteristiska äpplejuicearomer. Modellen ökar förståelsen för fenomenet plasticering inuti membranet, samt hur det påverkar transporten av olika aromer genom membranet. Med hjälp av några fysikaliska och kemiska egenskaper hos enskilda aromämnen var det möjligt att förutsäga generella trender för deras individuella separationsförmåga samt hur den påverkades av temperaturen för de ämnen som studerades. (Less)
Abstract
During production of concentrated fruit juices, both physical and chemical losses of aroma compounds occur due to heat treatment such as pasteurisation and evaporation. This leads to an inferior quality of the final product. By recovering the aroma complex from fresh juice and then adding it back to the processed juice, heat treatment can be avoided.



Hydrophobic pervaporation is an emerging membrane technique, which provides an interesting alternative when volatile organic compounds are to be separated from dilute aqueous mixtures. The intention of this thesis was to model and to optimise the pervaporation process for the application of aroma recovery from fruit juices, with focus on apple juice.



... (More)
During production of concentrated fruit juices, both physical and chemical losses of aroma compounds occur due to heat treatment such as pasteurisation and evaporation. This leads to an inferior quality of the final product. By recovering the aroma complex from fresh juice and then adding it back to the processed juice, heat treatment can be avoided.



Hydrophobic pervaporation is an emerging membrane technique, which provides an interesting alternative when volatile organic compounds are to be separated from dilute aqueous mixtures. The intention of this thesis was to model and to optimise the pervaporation process for the application of aroma recovery from fruit juices, with focus on apple juice.



Pervaporation was shown to be a promising alternative for the application of aroma recovery from natural apple juice, as it offers very high separation efficiency at mild process conditions. The operating conditions were shown to have a major impact on the performance of the process. Improved hydrodynamic conditions in the feed channel, increased feed temperature and decreased permeate pressure favour the aroma recovery. However, this has to be balanced with the energy input. Furthermore, due to the heat sensitivity of the aroma compounds, the temperature has to be kept at a reasonable level. There is also a possibility of controlling the composition of aroma compounds in the permeate via the process conditions. Optimum separation properties could be obtained when applying membranes designed with relatively thin selective layers using a modified silicone rubber polymer with a low degree of crosslinking in combination with a porous support of low resistance.



A model for a poly[octylmethyl siloxane] membrane, which can predict the influence of permeate pressure for any permeant within the chemical groups of alcohols, aldehydes and esters was developed. The model provides a better understanding of the plastication phenomena inside the membrane and its effect on permeabilities. By use of the hydrophobicity, the molecular size and the ability to form hydrogen bonds, it was possible to predict the general trends regarding the permeabilities and their influence on temperature for the organics studied. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Professor Crespo, Joao, Portugal
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Food and drink technology, optimisation, mass transfer, modelling, pervaporation, aroma recovery, Livsmedelsteknik
pages
164 pages
publisher
Gun Trägårdh, Dept. Food Engineering, Lund University
defense location
Room K:B at the Center of Chemistry and Chemical Engineering
defense date
2001-02-02 10:15
external identifiers
  • Other:ISRN: LUTKDH/(TKLT-1032)1-164
ISBN
91-7874-109-2
language
English
LU publication?
yes
id
dcf0a25d-3171-452c-bb85-33d55fe7a2ff (old id 41255)
date added to LUP
2007-10-14 16:33:14
date last changed
2016-09-19 08:45:13
@phdthesis{dcf0a25d-3171-452c-bb85-33d55fe7a2ff,
  abstract     = {During production of concentrated fruit juices, both physical and chemical losses of aroma compounds occur due to heat treatment such as pasteurisation and evaporation. This leads to an inferior quality of the final product. By recovering the aroma complex from fresh juice and then adding it back to the processed juice, heat treatment can be avoided.<br/><br>
<br/><br>
Hydrophobic pervaporation is an emerging membrane technique, which provides an interesting alternative when volatile organic compounds are to be separated from dilute aqueous mixtures. The intention of this thesis was to model and to optimise the pervaporation process for the application of aroma recovery from fruit juices, with focus on apple juice.<br/><br>
<br/><br>
Pervaporation was shown to be a promising alternative for the application of aroma recovery from natural apple juice, as it offers very high separation efficiency at mild process conditions. The operating conditions were shown to have a major impact on the performance of the process. Improved hydrodynamic conditions in the feed channel, increased feed temperature and decreased permeate pressure favour the aroma recovery. However, this has to be balanced with the energy input. Furthermore, due to the heat sensitivity of the aroma compounds, the temperature has to be kept at a reasonable level. There is also a possibility of controlling the composition of aroma compounds in the permeate via the process conditions. Optimum separation properties could be obtained when applying membranes designed with relatively thin selective layers using a modified silicone rubber polymer with a low degree of crosslinking in combination with a porous support of low resistance.<br/><br>
<br/><br>
A model for a poly[octylmethyl siloxane] membrane, which can predict the influence of permeate pressure for any permeant within the chemical groups of alcohols, aldehydes and esters was developed. The model provides a better understanding of the plastication phenomena inside the membrane and its effect on permeabilities. By use of the hydrophobicity, the molecular size and the ability to form hydrogen bonds, it was possible to predict the general trends regarding the permeabilities and their influence on temperature for the organics studied.},
  author       = {Olsson, Jenny},
  isbn         = {91-7874-109-2},
  keyword      = {Food and drink technology,optimisation,mass transfer,modelling,pervaporation,aroma recovery,Livsmedelsteknik},
  language     = {eng},
  pages        = {164},
  publisher    = {Gun Trägårdh, Dept. Food Engineering, Lund University},
  school       = {Lund University},
  title        = {Optimisation and modelling of aroma recovery by pervaporation},
  year         = {2001},
}