Microwave assisted extraction: An Advanced extraction technique

Microwave assisted extraction in food processing

1. Microwave-assisted Extraction Process
COURSE TITLE: UNIT OPERATIONS IN FOOD ENGINEERING
By
Abhishek Bahadur (16BTFT066)
Harsh Srivastava(16BTFT068)
Rajat Gupta (16BTFT069)
Abdul Rehman (16BTFT070)
Madhoop Pratap Tomar (16BTFT072)

2. Microwave assisted extraction:
An Introduction
•Microwaveassistedextractionisanefficient
methodwhichinvolvesderivingnatural
compoundsfromtherawfoodsamples.
•Thetechniqueallowsorganiccompoundsto
beextractedmorerapidlywithsimilarwith
similarorbetteryieldascomparedto
conventionalextractionmethods.

3. Introduction (in contd)
•Microwaveenergyconsistsofelectromagnetic
wavesandhenceresultsfromelectricand
magneticfieldsthatarenormaltoeachother.
•Thistypeofnon-ionizingenergypromotes
molecularmotionthroughmigrationofions
androtationofdipoleswithoutaltering
molecularstructure;asaresult,itgenerates
heatbyfriction.

4. Mechanism of Microwave assisted
extraction process
•Microwaveenergycanbeconvertedintoheat
viatwodifferentmechanisms,namely ̶
ionic conduction, and
dipole rotation.
•Bothoccursimultaneouslyinmost
applicationsofmicrowaveheating.

5. Ionic conduction
•Ionicconductionistheconductivemigrationof
dissolvedionsintheappliedelectromagnetic
fieldthatresultsinI2Rlosses(whereIdenotes
currentintensityandRdenotesresistance)
throughresistancetoionflow.
•Whereasallionsinsolutioncontributeto
conduction,lossesthroughionmigrationdepend
onthesize,charge,andconductivityofthe
dissolvedmolecules

6. Dipole rotation
•Dipolerotationreferstothealignment,by
effectoftheelectricfield,ofmoleculesina
samplehavingpermanentorinduceddipole
moments.
•Astheelectricfieldofmicrowaveenergy
increases,italignspolarizedmolecules;asthe
fielddecreases,thermallyinduceddisorderis
restored.

7. Types of Microwave Extractors
Components of a Microwave-Assisted Extractor
Microwavesystemsforsamplepreparationingeneral
andextractioninparticularcanbeoftwodifferent
typesdependingonthewaymicrowaveenergyis
appliedtothesample,namely:
(1)multimodesystems,inwhichmicrowaveradiationis
randomlydispersedinacavityandthesampleit
containsisevenlyirradiatedasaresult;and
(2)single-modeorfocusedsystems,inwhichmicrowave
radiationisfocusedonarestrictedzonewherethe
sampleismorestronglyirradiatedbymicrowave
energythaninmultimodesystems

8. Closed-and Open-Vessel Microwave-
Assisted Extractors
•In closed-vessel microwave-assisted devices,
which are usually of the multimode type, the
microwave treatment is conducted at a high
pressure.
•In open-vessel devices, which are generally of
the focused type, microwaves are applied at
atmospheric pressure and no overpressure is
produced as a result.

10. Advantages of Closed-vessel MAE
•Theycanreachhighertemperaturesbecausetheboiling
pointsofthesolventsusedareraisedbytheincreased
pressureinsidethevesselandhightemperaturesdecrease
thetimeneededformicrowavetreatment.
•Lossesofvolatilesubstancesduringmicrowaveirradiation
arealmostcompletelyavoidedbyvirtueoftheabsenceof
vaporlosses.
•Theyrequirelesssolventastheabsenceofevaporation
dispenseswiththeneedforcontinuousreplenishmentand
avoidtheriskofcontaminationasaresult.
•Thefumesresultingfromanacidmicrowavetreatment
remainwithinthevessel,sonoprovisionforhandling
potentiallyhazardousfumesneedbemade.

11. Disadvantages of Closed-vessel MAE
•Thehighpressuresusedposesafety
(explosion)risksderivedfromtheproduction
ofhydrogeninacidtreatmentsofmetalsand
alloys.
•Theamountofsamplethatcanbeprocessed
islimited(usuallylessthan100g)by
exception,thedynamicversioncommercially
availablefromCEMcantreatapproximately1
kgofsample.

12. Advantages of Open-vessel MAE
•Increasedsafetyresultingfromoperatingatatmospheric
pressurewithopenvesselscontaining,forexample,gas-
formingspecies.
•Theabilitytoaddreagentsatanytimeduringtreatment,
whichenablessequentialacidattacks,ifrequired.
•Theabilitytousevesselsmadeofdifferentmaterials
includingPTFE,glass,andquartz.
•Theabilitytooperateathightemperatureswithquartz
materialwhenusingsulfuricacidnearitsboilingpointto
destroyorganiccompounds.
•Theeasewithwhichexcesssolventcanberemovedto
ensurecompletedrynessofthedigestorextract.
•Theabilitytoprocesslargesamples.

13. Usefulness of open-vessel systems
•Highly efficient transfer and precise control of the energy deposited
into the sample.
•Fully automatic operation.
•Digestion of samples of 10 g or moredespeciallythose with a high
carbon contentdproduces large amounts of gas and vapors. In
open vessels, these are released by the reaction mixture and
continuously swept from the headspace above the sample. Thus, in
contrast to closed vessels, completion of gas-forming reactions is
favored as per Le Chatelier’sprinciple.
•Open-vessel operation is better suited to thermolabilespecies (eg,
organometals) because it uses low temperatures relative to closed-
vessel systems.
•Easy connection of the sample extraction step to other steps of the
analytical process.

14. Disadvantages of Open-vessel MAE
•The ensuing methods are usually less precise
than those developed with closed-vessel systems.
•Sample throughput is usually lower because most
open-vessel systems cannot process many
samples simultaneously.
•The operation times required to obtain results
similar to those of closed-vessel systems are
usually longer.
•Digestion is especially cumbersome with some
samples owing to the difficulty in reaching the
drastic conditions they require.

15. Types of Food Components Benefiting
From Microwave-Assisted Extraction
•Thetwomajortypesofmicrowave-assistedtreatmentfor
foodsamplesaredigestionandextraction(leaching).
•Bothofwhicharewidelyusedinfoodanalysis.
•IncontinuousMAE,slurrysamplescanbecirculated
throughadynamicmanifoldundermicrowaveirradiation
(Terigaretal.,2010).
•Usingthisprocedurewithsemisolidsamplessuchasyogurt
couldopenupnewprospectsforthecontinuoustreatment
ofcommonfoodsamples.
•Solvent-freemicrowave-assistedextractiontreatment,
whichisespeciallyindicatedfortheremovalofessential
oilsfromaromaticplants.

16. Reference
•InnovativeFoodProcessingTechnologies,
2016ElsevierLtd.,Microwave-Assisted
ExtractionofFoodComponentsM.D.Luque
deCastro,L.S.Castillo-Peinado,Universityof
Cordoba,Cordoba,Spain