STUDIES ON DRYING OF BITTER

GOURD SLICES IN MICROWAVE

ASSISTED FLUIDIZED BED DRYER

Presented by

SHAHWAR SIDDIQUI

M.Tech IV sem (APFE)

Under The Supervision

Of

Dr. MOHAMMAD ALI KHAN

(Associate professor)

INTRODUCTION

Momordica charantia Linn. commonly known asBitter melon or Bitter gourd is tropical andsubtropical climber of the family Cucurbitaceae.

It is widely distributed in China, Malaysia, India

and tropical Africa.

In Ayurveda, various parts of Momordica charantia(Karela) are recommended for many diseases like;cholera, bronchitis, anaemia, ulcer,diarrhea,dysentery.

Bitter gourd contains an array of biologically active

plant chemicals including triterpene,proteins,

steroids, alkaloids, saponins, flavonoids and acids

due to which plant possesses anti-fungal, anti-

bacterial, anti-parasitic, anti-viral, anti-tumorous,

hypoglycemic and anti-carcinogenic properties.

BITTERGOURD CULTIVATION

Annual Bittergourd Cultivation in

ASIA

BOTANICAL CLASSIFICATION

Kingdom Plantae

Division Magnoliophyta

Class Magnoliosida

Order Violes

Family Cucurbitaceae

Genus Momordica

Species Charantia

GREEN FRUITS OF

DIFFERENT MOMORDICA

SPECIES.

BENEFITS OF BITTER GOURD

Bitter gourd is worldwide known for its

effectiveness in treating diabetes. Bitter gourd

chemically contains a compound that is very much

similar to insulin and sometimes also referred as p-

insulin.

Bitter gourd is also good digestive agent and helps

in stimulating the secretion of gastric juices. It is

very helpful in stimulating liver for secretion of bile

juices that are very essential for metabolism of fats.

THERAPEUTIC USES

Bitter gourd is an appetite stimulant. Hence it is

used in the treatment of anorexia, a disorder in

which a person is unable to eat the required amount

of food.

Bitter gourd is used as a blood purifier due to its

bitter tonic properties. It can heal boils and other

blood related problems that show up on the skin.

BITTER GOURD – Functional

Uses

OBJECTIVES

To study the effect of inlet air temp, inlet airvelocities and microwave powers on drying behaviorand quality attributes of bitter gourd.

To study color change kinetics of bitter gourd duringmicrowave assisted fluidized bed drying.

To determine the best mathematical model describingthe kinetics of the drying process.

To study the effect of MAFBD on drying kinetics ofbitter gourd.

Materials and Methods

RAW MATERIALS USED

Good quality, fresh bitter gourds which had similar

skin color were procured from the local market. The

damaged, infected ones were removed manually by

visual inspection.

After cleaning with tap water, wiping and slicing,

200g of fresh sample of bitter gourd was weighed

and subjected to drying in a laboratory microwave-

assisted fluidized bed dryer.

DETAILS OF PARAMETERS &

THEIR LEVELS USED IN MAFBD

OF BITTERGOURD

S.NO.Types of

parametersParameters Levels Description

1

Independent

drying

parameters

Inlet air

temperature

Inlet air

velocity

Microwave

power

3

3

3

50, 55 &600C

25,30&35 m/s

180, 360 &

540 W

2Measuring

parameters -------

Weighing of

sample at

every 5 min.

FLOW SHEET FOR MAFBD OF

BITTER GOURD

DETERMINATION OF

PROCESS PARAMETERS

COLOUR ANALYSIS

MATHEMATICAL

MODELLING

MAFBD DRYING DATA FITTED TO THE

FOLLOWING DRYING MODELS

S.No Name of Model Model Equation

1 Lewis Model M.R.=exp(-k*t)

2 Henderson & Pabis Model M.R= a*exp(-k*t)

3 Wang & Singh Model M.R= 1+a*t+b*t2

4Approximate Diffusion

Model

M.R=a*exp(-k*x)+(1-

a)*exp(-k*b*x)

5 Page model M.R=exp(-a*x^b)

VALIDITY OF MODELS

For MAFBD, lowest R2 value (0.90400) was obtained for

approximate diffusion model fitted to the drying condition:

55°C inlet air temperature, 25 m/s inlet air velocity and 540W

microwave power with the highest chi-square and RMSE

values (0.02901 and 0.12044, respectively) for sample 6.

The highest value of R2 (1.000) was obtained for Page model

fitted to the drying condition: 60°C inlet air temperature ,

35m/s inlet air velocity and microwave power of 540W,

which had lowest chi-square and RMSE values (1.02204E-

23 and 2.61029E-12 respectively) for sample 27. Thus Page

Model is the most acceptable one and fitted best to the given

set of experimental data for MAFBD.

EXEMPLARY FITTING CURVE

OF VARIOUS MODELS

EFFECTS OF MAFBD ON

MOISTURE CONTENT OF BITTER

GOURD

CHANGE IN MOISTURE CONTENT OF

BITTER GOURD SAMPLES DURING

DRYING

Average initial moisture content was 12.3015 (g of water/g of drymatter). Depending on the drying treatment, during MAFBD dryingat 25 m/s inlet air velocity, the final moisture content rangedbetween 0.1101-0.1834 in 45 -100 mins as the microwave powerlevels varied from 180W to 540W (Fig.4.1).

At 30 m/s inlet air velocity, the final moisture content rangedbetween 0.1170-0.1748 in 40-90 mins, when the microwave powerlevels varied from 180W to 540W (Fig. 4.2). Similarly, at 35 m/sinlet air temperature, the final moisture content ranged between0.1108-0.1684 in 30-80 mins, when the microwave power levelsvaried from 180W to 540W (Fig. 4.3).

Drying time progressively decreased with the increase in inlet air velocities from 25m/s to 35m/s at a given microwave power level and drying temperature. Hence above findings suggests that the applied inlet air velocities and drying air temperature had a crucial effect on the drying rate during MAFBD drying.

EFFECTS OF MAFB DRYING ON L

VALUES OF BITTER GOURD

SAMPLES

L values decreased with drying time. In general, L also decreasedwith an increase in microwave power as well as the inlet airtemperature.

At 25m/s, it could be seen that the average minimum reduction to39.3000 was observed at 360W, 55°C inlet air temperature andaverage maximum reduction to 37.3850 was observed at 540W and50°C inlet air temperature.

At 30 m/s, the average minimum reduction to 39.2600 was observedat 360W microwave power and 55°C inlet air temperature andaverage maximum reduction to 37.2950 was observed at 540Wmicrowave power and 50°C inlet air temperature.

At 35m/s, the average minimum reduction to 39.2525 was observedat 360W microwave power and 55°C inlet air temperature andaverage maximum reduction to 37.2500 was observed at 540Wmicrowave power and 50°C inlet air temperature. The decrease in Lduring drying followed exponential decay law with coefficient ofdetermination ranging between 0.9968 and 0.8627.

EFFECTS OF MAFB DRYING ON “-a*”

(GREENNESS) VALUES OF BITTER GOURD

SAMPLES

The initial color of samples showed a negative a

values ranging from -5.0200 to -7.0750 indicating

greenness while the final -a value varied from -

0.5200 to -1.9700 as the microwave power levels

were increased.

When the bitter gourd was dried by MAFBD at

varying temperatures (50°C, 55°C, 60°C), the

average minimum reduction to -0.52 in –a value

was observed at 180W microwave power, 50°C inlet

air temperature and 30m/s inlet air velocity whereas

the maximum reduction to -1.9700 was observed at

540W microwave power 60°C inlet air temperature

and 35m/s inlet air velocity. -a values also exhibited

exponential decay law with coefficient of

determination ranging between 0.9964 and 0.8417.

EFFECTS OF MAFB DRYING ON “b”

(YELLOWNESS) VALUES OF BITTER

GOURD SAMPLES

The b value in fresh samples ranged between 35.47 to 28.12. The bvalue decreased with the increase in drying time and also with theincrease in microwave power and inlet air temperature.

At 25m/s it could be seen that the average minimum reduction to25.1135 was observed at 360W microwave power and 60°C inlet airtemperature and average maximum reduction to 22.0300 was observedat 50°C inlet air temperature and 540W microwave power.

At 30m/s, the average minimum reduction to 25.1020 was observed at360W microwave power and 60°C inlet air temperature and averagemaximum reduction to 22.0150 was observed at 540W microwavepower and 55°C inlet air temperature.

At 35m/s, the average minimum reduction to 24.0142 was observed at360W microwave power and 50°C inlet air temperature and averagemaximum reduction to 22.0112 was observed at 540W microwavepower and 50°C inlet air temperature. b values also exhibitedexponential decay law with coefficient of determination rangingbetween 0.9949 and 0.8197.

EFFECT OF MAFB DRYING ON ∆E

VALUES OF BITTER GOURD

SAMPLES

At 25m/s inlet air velocity, it could be seen that the average minimumchange in color to 15.8215 was observed at 60°C inlet air temperatureand 540W microwave power also average maximum change in color to51.6622 was observed at 50°C , and 360W.

At 30m/s inlet air velocity , it could be seen that the average minimumchange in color to 15.1202 was observed at 60°C inlet air temperatureand 360W microwave power also average maximum change in color to24.5598 was observed at 55°C inlet air temperature and 180Wmicrowave power.

At 35m/s inlet air velocity , it could be seen that the averageminimum change in color to 6.3575 was observed at 60°C inlet airtemperature and 360W microwave power also average maximumchange in color to 24.4198 was observed at 50°C inlet airtemperature and 360W microwave power. The color change datawere fitted to exponential growth model with coefficient ofdetermination ranging between 0.9584 and 0.9999.

EFFECT OF MAFB DRYING ON

CHROMA VALUES OF BITTER

GOURD SAMPLES

At 25m/s inlet air velocity the average minimumchroma value reduced to 25.0574 was observed at60°C inlet air temperature and 360W microwavepower and average maximum chroma value reducedto 22.1853 was observed at 60°C inlet airtemperature and 540W microwave power.

At 30m/s inlet air velocity the average minimumchroma value reduced to 25.0186 was observed at60°C inlet air temperature and 360W microwavepower and average maximum chroma value reducedto 22.1551 was observed at 55°C inlet airtemperature and 540W microwave power.

At 35 m/s inlet air velocity the average minimumchroma value reduced to 23.8448 was observed at50°C inlet air temperature and 180W microwavepower and average maximum chroma value reducedto 22.1060 was observed at 60°C inlet airtemperature and 540W microwave power.

The exponential data on chroma were regressed toexponential decay model where the data reasonablyfit to the model and coefficient of determinationranged between 0.9955 and 0.8457.

EFECT OF MAFB DRYING ON HUE ANGLE

VALUES OF BITTER GOURD SAMPLES

At 25m/s inlet air velocity, it could be seen that the average

minimum reduction to 91.9246° was observed at 55°C inlet air

temperature and 180W microwave power and average maximum

reduction to 94.3865° was observed at 50°C inlet air temperature

and 360W microwave power.

At 30m/s (Fig.4.21) , it could be seen that the average minimum

reduction to 91.2888° was observed at 50°C inlet air temperature

and 180W microwave power and average maximum reduction to

94.2791° was observed at 60°C inlet air temperature and 540W

microwave power.

At 35m/s (Fig.4.22) , it could be seen that the average minimum

reduction to 91.1622° was observed at 60°C inlet air temperature

and 360W microwave power and average maximum reduction to

94.2386° was observed at 60°C inlet air temperature and 540W

microwave power.

ANOVA FOR THE EFFECT OF MAFBD

ON ASH CONTENT OF BITTER

GOURD

At 25m/s, the value of ash content decreased from 1.945 to 1.87when temperature increased from 50°C to 55°C at 360Wmicrowave power.

At 30m/s, the value of ash content decreased from 1.965 to 1.645when temperature increased from 50°C to 55°C at 180Wmicrowave power, also ash content decreased from 1.995 to 1.825when temperature increased from 50°C to 55°C at 360Wmicrowave power, so it was observed that ash content decreasedwith an increase in the temperature.

At 35m/s, the value of ash content decreased from 1.94 to 1.835when temperature increased from 50°C to 55°C at 180Wmicrowave power, also ash content decreased from 1.905 to 1.85when temperature increased from 50°C to 55°C at 540Wmicrowave power.

ANOVA FOR THE EFFECT OF MAFBD ON

REHYDRATION RATIO OF BITTER GOURD

It was observed that for the bitter melon dried by MAFBDmethod, at given temperature, the value of rehydration ratioincreased with the increase in microwave power and viceversa .

At 50°C inlet air temperature, rehydration value increased from4.527 (at 30m/s inlet air velocity & 180W microwave power to 5.37(at 35m/s inlet air velocity & 540W microwave power).

Similarly at 55°C inlet air temperature, rehydration value increasedfrom 4.49 (at 35m/s inlet air velocity & 360W microwave power to5.455 (at 25m/s inlet air velocity & 540W microwave power).

At 60°C inlet air temperature, rehydration value increased from4.44 (at 30m/s inlet air velocity & 180W microwave power to 5.15(at 25m/s inlet air velocity & 540W microwave power).

ANOVA FOR THE EFFECT OF MAFBD

ON VIT C OF BITTER GOURD

It can be inferred that both the inlet air temperature

and the microwave power level have significant

effect on the ascorbic acid content of the bitter

melon samples. The best ascorbic acid values

obtained in MAFBD were found at 540 MW and

60°C inlet air temperature for sample 27 which is

equal to 63.27 mg/ 100 g. The lowest value of

ascorbic acid value was obtained for sample 19 at

180 MW and 60°C inlet air temperature which is

equal to 45.54 mg/100 g.

Conclusion

Distinct differences were observed in dryingtimes according to the various conditionsapplied.

The shortest time was found for sample 27dried at 60°C inlet air temperature, 35/s inletair velocity, and 540W microwave power.

This sample also had the highest rehydrationvalue due to increased porosity of driedproduct at higher microwave power resultingin increased absorption of water duringrehydration.

Cont…

However, other factors, along with drying timeand rehydration ratio were considered in order toselect appropriate conditions for drying of bittergourd.

Judging by the color change and redness values,the sample dried at 60°C inlet air temperature,35m/s inlet air velocity, and 540W microwavepower had the least color change and the highestnegative “a” (greenness) value resulting in abetter quality product.

As this sample takes lesser time for drying byMAFBD, it resulted in better quality such as colorpreservation, higher Vit C content, and lessdestruction of the dried products.