potential application of microwaves in neem industry

Potential Application of Microwaves in Neem Industry

Potential Application of Microwaves in Neem Industry

G.S. Vijaya Raghavan

Department of Bioresource Engineering, McGill University, Montreal, Canada

IntroductionIntroductionIntroduction

The neem plant Source of biological pesticides

Medicinal components from different parts of the neem plant

IntroductionIntroductionIntroduction

Important processes of neemindustry

Extraction

Drying

X-rays u.v. i.r.

100A

3x1016

1 μm

3x1014

100 μm

3x1012

Radio frequencies

1 cm

3x1010

1 m

3x108

100 m

3x106

10 km

3x104

M.W.

Wavelength

Frequencies (Hz)

Microwave

1 cm

30 GHz

1 m

300 MHz

10 cm

3 GHz

2450 MHz 915 MHz

MicrowavesMicrowavesMicrowaves

Polar molecules - dipoles

-+

+-

+

- +-+-

-++

+--

Non-polar molecules

+ - -+

+ - -+

+- - +

Ions

Effect of alternating electric field on polar molecules

Microwave-matter interactionMicrowaveMicrowave--matter interactionmatter interaction

Parameters• Dielectric constant (ε’)

• Loss factor (ε’’)

Power absorption

Pv=2πf εoε’’E2

Microwave-matter interactionMicrowaveMicrowave--matter interactionmatter interaction

Characteristics of microwave-matter interaction

• Instant effect

• Volumetric heating

• Based on molecular rotation or ion conduction

• Selective effect

Microwave-Assisted ExtractionMicrowaveMicrowave--Assisted ExtractionAssisted Extraction

Mechanism involving glandular-level micro-explosion (Proposed by J.R.J. Pare)


Create high temperature working region within cold environment


Facts about microwave-assisted extraction (MAE):

Extraction of compounds from seeds, food, and feed samples (Ganzler et al., 1986)• Soxhlet extraction: 3 hrs3 hrs• MAE : 3.5 minutes3.5 minutes


Obtaining essential oil from peppermint leaves (Paré, 1995)

• Steam distillation: 2 hrs2 hrs with a yield of 0.277%0.277%

• Extraction under microwave irradiation: 40 s40 s with a yield of 0.371%0.371%


Extraction of glycyrrhizic acid from licorice (Pan et al., 2000)

• Heat reflux extraction: 4.5 hrs4.5 hrs

• Ultrasonic extraction: 20.5 hrs20.5 hrs

• Soxhlet extraction: 10 hrs10 hrs

• Room temperature extraction: 20 hrs20 hrs

• MAE: 4 min4 min


0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 20 40 60

Extraction time (min)

lnA

MAE RTE RFX

Linear regression of lnA vs. extraction time for total ginsenosides using the three extraction methods.


0.99080.02083.71RFX

0.99430.013.78RTE

0.99210.04083.78MAETotal ginsenosides

0.96750.01892.20RFX

0.86120.00972.19RTE

0.95410.02482.24MAE

mRb1

0.99640.02523.23RFX

0.99860.00633.19RTE

0.96420.03753.27MAE

Rb1

0.99940.02342.15RFX

0.99320.01262.29RTE

0.96850.02051.86MAE

Re

R2|k|C


96%31%49%-13%MAE vs. RFX

106%95%300%86%RFX vs. RTE

TotalmRb1Rb1Re

The enhancement factor for:RFX vs. RTE = (kRFX - kRTE)/ kRFX * 100%; MAE vs. RFX = (kMAE - kRFX)/kMAE * 100%; (kMAE, kRTE, and kRFX are extraction constants for MAE, RTE, and RFXrespectively)

0

20

40

60

80

100

Seed Seed shell Leaf Petiole

Rec

over

y (%

)MAE RTE RFX

Percentage recovery of AZRL from different parts of neemby MAE, RTE, and RFX methods (20 min, methanol)

0102030405060708090

100

Seed Leaf Seed Shell

Rec

over

y (%

)

MeOH DCM PE

Effect of solvent types on the % recovery of AZRL by MAE (150W, 20 min). DCM = dichloromethane, PE = petroleum ether.

Influence of total irradiation time on % recovery of AZRL

0102030405060

0 100 200 300 400 500 600Total irridiation time (s)

Reco

very

(%)

Seed Leaf

0102030405060

0 50 100 150 200 250 300Power (W)

Reco

very

(%)

Seeds - 3 Minutes Seeds - 10 minutesLeaves - 3 Minutes Leaves - 10 minutes

Influence of microwave power on % recovery of AZRL

Scale-up Simulation of MAEScaleScale--up Simulation of MAEup Simulation of MAE

MAE Scale-up SimulationMAE ScaleMAE Scale--up Simulationup Simulation

Microwave-Assisted DryingMicrowaveMicrowave--Assisted DryingAssisted Drying

Microwaves are suitable method to combine with:

• Hot air (microwave-convective drying)

• Low pressures (microwave-vacuum drying)

• Heat pump


Microwaves convective drying

• Heat is generated within the commodity, causing a pressure gradient towards the surface

• The surface water is carried away by flowing hot air

• The temperature increase in the carrier enhances its ability to store moisture

Note: It can be also used for MW/convective and convective drying

Microwave-Assisted DryingMicrowaveMicrowave--Assisted DryingAssisted DryingDrying curves for grapes under convective and combined convective and microwave drying (air

at 50°C):

Microwave-Assisted DryingMicrowaveMicrowave--Assisted DryingAssisted DryingDrying of strawberries by convection alone and by

microwave at three power levels:


Microwaves/vacuum drying

• Instead of hot air, a subatmosphericpressures is applied

• Surface water is evaporated even without any heat introduction when vacuum reaches certain value


Microwaves/vacuum drying

• Low pressure offers lower temperature of the process, giving a product with higher quality

• This is a good process for heat sensitive products, used in pharmaceutical and food industry


Vacuum pumpVacuum pump

DesiccatorDesiccator

Vacuum meterVacuum meterScaleScale

PCPC

MW generatorMW generator

MW chamberMW chamber

Vacuum chamberVacuum chamber

Data collectorData collector

Microwave-Assisted DryingMicrowaveMicrowave--Assisted DryingAssisted DryingReal-time temperature profiles of convective,

MW/convective and MW/vacuum dried cranberries under similar conditions

Temperature profiles

0

40

80

120

0 10 20 30 40 50

Time (min)

Tem

pera

ture

(o C

)

MW/convective MW/vacuum Convective

Microwave-Assisted DryingMicrowaveMicrowave--Assisted DryingAssisted DryingEnergy efficiency comparison

0.3021.330/451.25

0.3518.330/301.25vacuum0.1361.130/451.00MW/

0.1844.330/301.00

0.1158.630/601.25

0.1065.430/301.25convective

0.1271.830/601.00MW/

0.1175.330/301.00

Drying efficiency (kgwater/MJ)

MW power-on time (min)

MW mode(s on/s off)

MW density (W/g)

Drying method

SummarySummarySummaryCompared to conventional extraction methods, microwave-assisted extraction has the following benefits:

Reduced processing timeHigher yield of extractsBetter quality productsEspecially beneficial to heat sensitive products

SummarySummarySummary

Simulation study indicated that it is possible to scale-up the extraction process in the batch mode

Microwave-assisted extraction technology can be potentially used in the neem industry

Biological pesticides extraction mainly from the seeds

Medicinal components extraction from various parts of the neem plant

SummarySummarySummaryAdvantages of microwave drying

• Fast and volumetric heating

• Higher drying rate

• Shorter drying time

• Higher product quality

• Reduced energy consumption

• Overall cost savings

SummarySummarySummaryDisadvantages of microwave drying

• High initial equipment cost

• Aroma loss

• Physical damage caused by local heating

• Specific size and shape of the product dried

potential application of microwaves in neem industry

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