Thin Layer Drying Kinetics for Osmotic Dehydrated Coconut Slices in Salt Solution

ISSN: 2395-0560

International Research Journal of Innovative Engineering www.irjie.com

Volume1, Issue 3 of March 2015

______________________________________________________________________________2015 ,IRJIE-All Rights Reserved Page -41

Thin Layer Drying Kinetics for Osmotic Dehydrated Coconut Slices in Salt Solution

G.Kamalanathan 1 , Dr.RM.Meyyappan2

Department of Chemical Engineering, Annamalai university, Annamalai nagar, Tamil nadu,India. _________________________________________________________________________________________

Abstract: This work was carried out to determine the most appropriate thin layer drying model and the effective moisture diffusivity of coconut slices for both without treatment of osmotic dehydration and osmotic dehydration of coconut slices in salt solution .The coconut slices were dried in conventional Tray Drier at different temperatures such as 50 0c, 600 c and 700 c. The Drying data found through the experimental studies were fitted to eight thin layer drying models. The Midilli model was found to be the best one for describing the thin layer drying kinetics of the coconut slices for both without treatment of osmotic dehydration and osmotic dehydration of coconut slices in salt solution. the effective moisture diffusivity was calculated by using Ficks second law, which varied from 6.296739x10-10 to 1.035369x10-09 m2/s for without treatment of osmotic dehydration of coconut slices and 8.029399x10-10 to 1.225539x10-09 m2/s for osmotic dehydration of coconut slices in salt solution. The relation between moisture diffusivity and temperature was described by Arrhenius type equation .The D0 and Ea for without treatment of osmotic dehydration was 3.2908*10-6 m2/s and 22.963 KJ/g mol and for osmotic dehydrated coconut slices, it was 1.10344*10-6 m2/s and 19.454 KJ/g mol.

Keywords: Salt solution, Dryer, Osmotic dehydration, Coconut slices

________________________________________________________________________________________

Introduction

The coconut palm (cocos nucifera ) is a member of the family Aeraceae (palm family). Botanically, a

coconut is a simple dry nut known as fibrous drupe. Coconut is grown in more than 90 countries worldwide. India

holds a premier position in the world with a total production of 10,824,100 tonnes (faostat. 2013) .Drying is one of

the oldest methods of food processing. Drying preserves food by removing enough moisture from food to prevent

decay and spoilage by bacteria, yeasts and moulds. The osmotic dehydration is a method for the partial dehydration of

foods, such as fruits and vegetables, by immersing them in a concentrated sugar or salt solution. The intermediate

moisture content product obtained after osmotic dehydration is not shelf stable. It must be preserved by any other

means. As an example, it can be further dried, canned or frozen .osmotic dehydration was done to improve colour and

flavour, to reduce shrinkage of the food material and potential energy savings up to 50% of initial moisture is

removed from the food material without undergoing a phase change. Drying is an important operation in the food

and pharmaceutical industries and accomplished by techniques such as air drying, vacuum drying, spray drying and

freeze drying (Banga, J.R. & Singh, R.P, 1994). Hot air drying is widely used commercial technique for drying

biological products (Mazza, G. & Le Maguer, M,1980).

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The theoretical model considers only the internal resistance to moisture transfer between product and

heating air whereas semi-theoretical and empirical models consider only the external resistance (Midilli A et al,

2002). Empirical model neglects the fundamentals of drying process and presents a direct relationship between

average moisture and drying time by means of regression analysis (Wang CY& Singh RP, 1978). The semi theoretical

model is derived from the Ficks second law of diffusion. Drying of many food products such as rice (Ece, M. C., &

Cihan, A., 1993), soya been (Suarez ,c.et al, 1980) and rapeseed (Crisp, J., & Woods, J. L,1994) has been successfully

predicted using Ficks second law with Arrhenius type temperature dependent diffusivity.

The study done on pomegranate arils showed that the drying rate increased with the drying air temperature,

thus reducing drying time. Entire drying process of the pomegranate arils occurred in the falling rate period. The page

model was found to be suitable to predict the moisture ratio of pomegranate arils in a thin layer drying

(A.R.P.Kingsly&D.B.Singh, 2007). similar result were reported in strawberry where modified page model was found

to be the suitable model (Ebru Kavak Akpinar &Yasar Bicer, 2006).osmotic dehydration is a method to aid removal

of coconut kernel from the shell without much difficulty. They have proposed a semi-empirical model to predict the

moisture content of the coconut at any point of immersion time(N.K.Rastogi & K.S.M.S.Raghavarao. ,1994).A

considerable amount of work has been carried out on thin layer drying of different food and vegetables products

.some of the thin layer models were reported for drying of litchi (Janjaia et al.,2011), potato(Akpinar, E. K et

al.,2003a), sweet potato (Diamente, L. M., & Munro, P. A. ,1991).) and wheat (Kassem, A. S.,1998). In this study, the

thin layer drying characteristics for untreated coconut slices and osmotic treated coconut slices in salt solution were

investigated. In addition, the Effective Diffusivities and Activation Energy in the convective drying process of

coconut slices were also calculated.

Materials and Methods

The commercially available salt was used to prepare osmotic solution. The desired quantity of salt was mixed with

required amount of distilled water to prepare desire range of osmotic salt solution. The concentration of salt solution

was measured by using refractometer. The mature coconuts of 10 month after flowering were purchased from local

market. The average moisture content of coconut slices was found to be 123.713 % on Dry basis. The initial moisture

content of coconut slices was measured by drying coconut slices in hot air oven at 105 0 c for 5hrs. The kernel portion

of the coconut was taken and washed with water to remove other debris. The kernel was cut into pieces of 5 mm

thickness and 20 mm length. The coconut slices of 100 g were weighed and initially undergoing pre treatment such as

blanching and immersing in 2% citric acid solution to increase the shelf life of the coconut slices. For without

treatment of osmotic dehydration, the coconut slices after pre treatment dried in a tray dryer at different

temperature such as 50 0c , 60 0c and 70 0c. The drying process was continued until the drying rate reached zero.

Similarly for osmotic dehydration, The coconut slices were weighed, pre-treated, treated in osmotic salt solution and

dried in tray dryer at different temperature such as 50 0c, 60 0c and 70 0 c until drying rate reached zero.

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Osmotic treatment

Coconut slices of 100 g were weighed and then blanched at 90 C for 2 minutes to inactivate the enzymatic activity and immersing in 2% citric acid solution to increase the shelf life of the coconut slices. The slices were placed

in a 500 ml Erlenmeyer flask comprised of osmotic salt solution. The osmotic solution to sample ratio was maintained

as 5:1 (w/w). Osmotic dehydration was performed under constant agitation of 200 rpm, to maintain a uniform

constant temperature throughout the experiment. After osmotic dehydration, the samples were removed from osmotic

solution and blotted with adsorbent paper to remove the excess salt solution. The coconut slices were dehydrated in

osmotic salt solution at process conditions of parameter such as 16.27 % w/w salt concentration, 34.74 0 c temperature

and 2.01 hours processing time. The experiment was conducted at this process conditions and the experimental values

were obtained for response variable such as WR, SG and WL were 14.380.025, 1.77 0.052 and 16.160.048

respectively.

Hot air drying Equipment

Hot air drying was performed in a tray dryer operating at air velocity of 1.5 m/s which was measured using anemometer. The tray dryer consists of trays made of stainless steel. The dryer consisted of temperature controller

(50-250 0 c dry bulb temperature) and a centrifugal fan for air flow. The dryer was run without sample for about 30

minutes to set desired conditions for each drying experiment. The coconut slices after pre treatment, they were

subjected to hot air drying in tray dryer at 50, 60 and 70 C for without treatment of osmotic dehydration of coconut

slices .Similarly for osmotic dehydration of coconut slices, the coconut slices after pre treatment, partially dehydrated

in salt solution and then osmotic dehydrated coconut slices were subjected to hot air drying in tray dryer at different

temperature such as 50, 60 and 70 0 c. Moisture loss was measured using digital balance and recorded each 5 minute

with an accuracy of +0.001 g. Air drying was continued until the constant weight was obtained. The experiments were

conducted with 3 replicates and average values were taken.

Modelling of the thin layer drying curves

The experimental values obtained for without treatment of osmotic dehydration and osmotic dehydration of coconut slices in salt solution were fitted to eight thin layer drying models and listed in Table 1. The eight thin layer

drying models were investigated to find the most suitable one. In these models, MR represent the dimensionless

Moisture Ratio namely MR = (Mt Me)/(M0 Me), where Mt is the moisture content at any time t, M0 is the initial

moisture content and Me is the equilibrium moisture content. In these models, the moisture ratio was simplified to

Mt/M0 instead of MR= (Mt Me)/(M0 Me) as the value of Me is relatively small compared to Mt or M0 (Pala et

al.,1996) ;( Doymaz. I .2004).

In this present study, the non linear regression analysis was performed using the software MAT LAB 7.0.

The statistical parameters such as correlation coefficient (R2) were one of the primary criteria to select the best model.

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Other statistical parameters such as Chi- squared (2) and the root mean square error (RMSE) were used to determine

the quality of the fit. The fit showing the higher R2, the lowest 2 and RMSE was considered as the suitable model.

(Demir, V et al.,2004); (Erenturk, S et al.,2004); (angavhane, D. R et al.,1999); ( Togrul, I. T., & Pehlivan, D. 2002).

The 2 and RMSE values were evaluated as,

(1)

RMSE = (, ,)

(2)

Where MRexp is the ith experimentally observed moisture ratio, MRpred is the ith predicted moisture ratio, N is the number of observations and z is the number of constants in models.

Calculation of Effective diffusivity and Activation energy

Ficks diffusion equation (Crank, 1975) was used to describe the drying characteristics in the falling rate

period. The Eq.(3) could be used for various regularly bodies such as rectangular ,cylindrical and spherical product

and form of equation (3) can be applicable for particles with slab geometry by assuming uniform initial moisture

distribution and for long drying time.

= () exp () (3) The Eq( 3) can be further simplified to only the first term of the series and can be written as Eq.(4).

=

exp

(4)

where Deff is the effective moisture diffusivity (m2/s); L is the half thickness of slab (m). then Eq.(4) can be written in logarithmic form as follows .

=

t (5)

The effective moisture diffusivity (Deff ) were determined by plotting Experimental drying data in terms of ln MR versus drying time(t) in eq (5).

Calculation of activation energy The effective moisture diffusivity could be related with temperature by simple Arrhenius equation as given below (Lopez, A et al .,2000); (Carbonell, J.Vet al .,1986).

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= (6) Where D0 is the constant equivalent to the diffusivity at infinitely high temperature (m2/s), Ea is the activation energy

(kJ/mol), R is the universal gas constant (8.314 J/ (mol K) and T is the absolute temperature. The activation energy

and the constant (D0) could be determined by linearization of equation (6) and by plotting ln(Deff) versus 1/T Eq. (7).

Results and Discussion The coconut slices (100 g) were dried in the tray dryer with thickness of about 5 mm. The initial average moisture content of the coconut slice was about 123.713 % (Db) for without treatment of osmotic dehydration of

coconut slices. The final moisture content obtained for without treatment of osmotic dehydration of coconut slices

was about 4.453, 4.453 and 4.392 % on Dry basis at 50, 60 and 70 C respectively and shown in Fig (1). The drying

time required for without treatment of osmotic dehydration of coconut slices to reach the equilibrium moisture

content was found to be 195, 155 and 130 minutes at 50, 60 and 70 C respectively. The moisture ratio versus drying

time at three different drying temperatures such as 50, 60 and 70 0 c were shown in Fig. (2). The drying time was

decreased with increase in drying temperature to reach the equilibrium moisture content of the coconut slices for

without treatment of osmotic dehydration of coconut slices, it may be due to increase in water vapour pressure within

the coconut slices. Obviously, increasing drying temperature speeds up the drying process and hence shortens the

drying time.

The drying time required for osmotic dehydrated coconut slices in salt solution to reach the equilibrium

moisture content was fund to be 140, 120 and 95 minutes at 50, 60 and 70 C respectively. The final moisture content

of osmotic dehydration of coconut slices in salt solution was found to be 5.057, 5.045 and 5.023 % on Dry basis for

50, 60 and 70 C respectively and shown in Fig (4). In Fig (5), it implies that the moisture ratio versus drying time at

three different drying temperatures such as 50, 60 and 70 0 c. For the osmotic dehydrated coconut slices, the drying

time was decreased to approach the equilibrium moisture content with increase in drying temperature maybe due to an

increase in vapour pressure of osmotic solution within the coconut slices. Drying of coconut slices for both without

treatment of osmotic dehydration of coconut slices and osmotic dehydrated coconut slices in salt solution occurred in

falling rate period and due to rapid removal of moisture. There is no constant rate period was observed on entire

drying process .Similar findings have been reported by many researchers for the drying of apricots (Doymaz., 2004)

and drying of red chillies (Chandy et al., 1992).

Further it can be observed that the drying air temperature has an important effect on the drying rate and the total drying process was found to be occurred in falling rate period only. Therefore diffusion governed for drying

behaviour of coconut slices. To remove the first half of moisture at 50, 60 and 70 C, it took about approximately 40,

27 and 20 minutes for without treatment of osmotic dehydration of coconut slices. Similarly, for osmotic dehydration

of coconut slices, it took about approximately 33, 29 and 23 minutes respectively. To remove moisture further it

took longer time due to slower diffusion. The rate of migration of moisture from the inner surface to outer surface

decreases and hence lowers the drying rate. It may be due to the internal mass transfer resistance, which control the

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drying time and hence the falling drying rate period was dominate in entire drying process. When compared without

treatment of coconut slices and osmotic dehydrated coconut slices, the drying time required to reach the equilibrium

moisture content was less in osmotic treated coconut slices and shown in fig (2 & 5)

Fitting of drying models Eight thin layer drying models were fitted to the experimental data of moisture ratio of coconut slices at three

different drying temperatures and fitted thin layer models were given in Table (1). Parameter values of R2, 2 and

RMSE and the drying model coefficients were listed in Table (2-7). It is assumed that the model which has highest R2

and the lowest 2 and RMSE could be considered as the best fit. According to these criteria, the Midilli model was

found to be the best one in all cases. The predicted data of moisture ratio for drying coconut slices for both without

treatment of osmotic dehydration of coconut slices and for osmotic dehydration of coconut slices in salt solution were

shown in Fig (3&6).It may be observed from the figure(2,3) and (5,6) that the agreement between experimental

values and predicted values of this Midilli model was found to be excellent.

Determination of Effective Moisture Diffusivity The effective diffusivity for without treatment of osmotic dehydration and osmotic dehydration of coconut

slices at different drying temperatures was evaluated by plotting ln(MR) versus time and shown in Fig (7- 12) and

data were presented in Table( 8-9). The values of effective diffusivity varied from 6.296739x10-10 to 1.035369x10-09

m2 /s for without treatment of osmotic dehydration and for osmotic dehydration of coconut slices were 8.029399x10-

10 to 1.225539x10-09 m2/s and it could be obviously found that effective diffusivity increased with increase in drying

temperature.

Determination of Activation Energy

The logarithm of Deff as a function of the reciprocal of drying temperature was plotted in Fig (13&14). The

results showed a linear relationship between ln(Deff) versus 1/T showing an Arrhenius type relationship. The R2 for

the regression was 0.9901 for without treatment of osmotic dehydration of coconut slices and osmotic dehydration of

coconut slices was 0.9855.Diffusivity constant ( D0 ) for without treatment of osmotic dehydration of coconut slices

and osmotic dehydration of coconut slices were found to be 3.2908 10-6 m2/s and 1.10344 10-6 m2/s. The activation

energy for without treatment of osmotic dehydration of coconut slices and osmotic dehydration of coconut slices were

evaluated as 22.963kJ/gmol and 19.454 kJ/gmol. Similar results were obtained for apple pomace 24.512 KJ/mol for

overall falling rate period was reported by wang et al. (2006).

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Fig-1: Thin layer drying curves for without treatment of osmotic dehydration of coconut slices at different

Temperatures.

Fig 2: Experimental values of Moisture ratio versus drying time of coconut slices (without treatment of osmotic

dehydration) at different temperatures.

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0 50 100 150 200 250

Moi

stur

e co

nten

t (g

Wat

er/g

Dry

solid

Drying Time (Min)

Moisture content (g Water/g Dry Solid) vs Drying Time (Min)

Temperature 70 degree celsius



0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 50 100 150 200 250

Moi

stur

e ra

tio (M

/M0)

Drying time (min)

Moisture ratio(M/M0) VS Drying time (min)




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Fig 3: Predicted values of Moisture ratio versus drying time of coconut slices (without treatment of osmotic

dehydration) at different temperatures

Fig-4: Thin layer drying curves for osmotic dehydration of coconut slices in salt solution at different Temperatures.

0

0.2

0.4

0.6

0.8

1

1.2

0 50 100 150 200 250

Moi

stur

e Ra

tio (M

/M0)

Drying Time (Min)

Moisture ratio (M/M0) vs Drying Time (Min)

Predicted values at 70 degree celsius



00.10.20.30.40.50.60.70.80.9

0 50 100 150

Moi

stur

e co

nten

t (g

Wat

er/g

Dry

Sol

id)

Drying Time (Min)

Moisture content (g Water/g Dry Solid) vs Drying Time (Min)




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Fig 5: Experimental values of Moisture ratio versus drying time of coconut slices (treated with osmotic dehydration

in salt solution) at different temperatures.

Fig 6: Predicted values of Moisture ratio versus drying time of coconut slices (treated with osmotic dehydration in

salt solution) at different temperatures.

0

0.2

0.4

0.6

0.8

1

1.2

0 50 100 150

Moi

stur

e Ra

tio (M

/M0)

Time (Min)

Moisture Ratio (M/M0) vs Time (Min)

temperature 70 degree celsius



00.20.40.60.8

11.2

0 50 100 150Moi

stur

e Ra

tio (M

/M0)

Drying Time (Min)

Moisture Ratio(M/M0) vs Drying Time (Min)




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Fig-7: Logarthemic Moisture ratio vs Drying Time at 50 0 c temperature (without treatment of osmotic dehydration)


y = -0.0149x - 0.209R = 0.9768

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

00 50 100 150 200 250

ln(M

R)

Drying Time (Min)ln (MR) vs Drying Time(Min)


Linear (temperature 50 degree celsius)

y = -0.0201x - 0.209R = 0.9921

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

00 50 100 150 200

ln(M

R)

Drying time (Min)ln (MR) vs Drying time (Min)



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Fig-10: Logarthemic Moisture ratio vs Drying Time at 50 0 c temperature ( treatment with osmotic dehydration )

y = -0.0245x - 0.209R = 0.9958

-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

00 50 100 150

ln(M

R)

Drying Time (Min)ln( MR) vs Drying time(Min)



y = -0.0190x - 0.2090R = 0.9868

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

00 50 100 150

ln(M

R)

Drying Time (Min)ln(MR) vs Drying Time (Min)


Linear (Temperature 50 degree celsius)

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y = -0.0226x - 0.209R = 0.9847

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

00 50 100 150

ln(M

R)

Drying Time(Min)ln(MR) vs Drying Time (Min)



y = -0.0290x - 0.2090R = 0.9809

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.00 20 40 60 80 100

ln(M

R)

Drying Time (Min)ln(MR) vs Drying Time (Min)



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Fig -13 : Arrhenious type relationship between effective diffusivity and drying temperature ( without treatment of osmotic dehydration)

Fig -14 : Arrhenious type relationship between effective diffusivity and drying temperature ( treatment with osmotic

dehydration )

y = -2762.1x - 12.624R = 0.9901

-21.3

-21.2

-21.1

-21

-20.9

-20.8

-20.7

-20.60.0029 0.00295 0.003 0.00305 0.0031 0.00315

Ln(D

eff)

1/T (1/K)Ln(Deff) vs 1/T (1/K)

y = -2339.6x - 13.717R = 0.9855

-21-20.95

-20.9-20.85

-20.8-20.75

-20.7-20.65

-20.6-20.55

-20.5-20.45

0.0029 0.00295 0.003 0.00305 0.0031 0.00315

Ln(D

eff)

1/T (1/K)Ln(Deff) vs 1/T(1/K)

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Table-1: Thin layer drying models

Table-2:Drying models for without treatment of osmotic dehydration of coconut slices were dried at 50 C in tray drier

Model a b C d R2 Chi - sq RMSE

Newton 0.01657

0.9945 0.000385 0.01939

Henderson 0.9626 0.01592 0.9963 0.000271 0.01605

Page 0.02404 0.9134 0.9977 0.000168 0.01266

Wang & Singh -0.01214 3.892e-005 0.9562 0.003206 0.05519 Modified Page model 0.3937 0.0421

0.9945 0.000406 0.01965

Logarthemic model 0.9591 0.01629

0.00735

0.9964 0.000280 0.01612

Two term model 0.8911 0.01487 0.1176

0.08491

0.9983 0.000141 0.01127

Midilli model 1.016 0.03329

0.8239 -

0.0002463 0.999 0.000008 0.00849

Table-3: Drying models for without treatment of osmotic dehydration of coconut slices were dried at 60 C in tray drier

Model a b C d R2 Chi - sq RMSE

Newton 0.02304

0.9965 0.000194 0.01372

Henderson 0.9548 0.02196 0.9973 0.000205 0.01389

Page 0.03432 0.9001 0.9988 0.000089 0.009138

Wang & Singh -0.01626 6.827E-005 0.9496 0.003799 0.05968 Modified Page model 0.1745 0.132

0.9948 0.000395 0.01925


0.01218 0.9976 0.000194 0.01327

Two term model 0.8977 0.02073 0.1036

0.1602

0.9993 0.000056 0.007037

Midilli model 0.9999 0.03906 0.8576 -0.0001665 0.9994 0.000052 0.006809

Model name Equation Reference

Newton MR = exp(-kt) Ayensu, A. (1997).

Henderson MR = aexp(-kt) Rahman et al(1998)

Page MR = exp(-ktn) Doymaz, I. (2004b)

Wang & Singh MR = 1+at + bt2 Panchariya et al(2002)

Modified Page model MR = exp(-kt)n Overhults et al .(1973)

Logarthemic model MR = a exp(-kt)+c Lahsasni et al (2004)

Two term model MR = a exp(-k0 t)+b exp(-k 1t) Madamba et al(1996)

Midilli model MR = a exp(-ktn)+bt Ertekin, C., & Yaldiz, O. (2004).

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Table-4: Drying models for without treatment of osmotic dehydration of coconut slices were dried at 70 C in tray drier

Model a b c d R2 Chi - sq RMSE

Newton 0.02964

0.9906 0.000664 0.02529

Henderson 0.9487 0.01862 0.9994 0.000044 0.006425

Page 0.05028 0.8586 0.9989 0.000081 0.008667

Wang & Singh -0.02017 0.02802 0.9938 0.000470 0.02087 Modified Page model 0.1732 0.1711

0.9906 0.000718 0.02579


0.0328

0.9963 0.000307 0.01654

Two term model 0.7584 0.02342 0.2476

0.09485

0.9994 0.000050 0.006558

Midilli model 1.009 0.05486 0.8336 -7.506E-

005 0.9991 0.000085 0.008523

Table-5: Drying models for osmotic dehydrated coconut slices in salt solution were dried at 50 C in tray drier


Newton 0.02148

0.9992 0.000060 0.007613

Henderson 0.9853 0.02115 0.9995 0.000040 0.006136

Page 0.0242 0.9703 0.9995 0.000037 0.005912

Wang & Singh -0.01634 7.158e-005 0.9824 0.001440 0.03662

Modified Page

model 0.4315 0.04977

0.9992 0.000064 0.007753

Logarthemic

model 0.9839 0.0213

0.002498

0.9995 0.000043 0.006211

Two term model 0.9732 0.02089

0.02723

0.2697

0.9997 0.000029 0.00505

Midilli model 0.9955 0.02455

0.962 -5.981E-

005 0.9996 0.000036 0.005615

Table-6: Drying models for osmotic dehydrated coconut slices in salt solution were dried at 60 C in tray drier.


Newton 0.02556

0.9987 0.000102 0.009923

Henderson 1.004 0.02566 0.9988 0.000110 0.01006

Page 0.02396 1.017 0.9988 0.000103 0.009751

Wang & Singh -0.01941 0.0001003 0.989 0.000982 0.03006 Modified Page model 0.8115 0.0315

0.9987 0.000111 0.01014

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0.002571

0.9988 0.000119 0.01026

Two term model 1.038 0.02633 -

0.04428 0.08749

0.9989 0.000116 0.009906

Midilli model 0.9878 0.01937 1.079 0.00019

19 0.9992 0.000082 0.008322 Table-7: Drying models for osmotic dehydrated coconut slices in salt solution were dried at 70 C in tray drier

Model a b C d R2 Chi - sq RMSE Newton 0.03261

0.9968 0.000284 0.01644

Henderson 1.023 0.03339 0.9975 0.000248 0.01494 Page 0.02568 1.067 0.9981 0.000190 0.01308 Wang & Singh -0.0247 0.0001616

0.9922 0.000786 0.02661

Modified Page model 0.7327 0.0445

0.9968 0.000316 0.01689


0.00131

0.9975 0.000277 0.01536

Two term model 1.004 0.03307

0.01083

0.03291

0.9974 0.000326 0.01616

Midilli model 0.9932 0.01942 1.162 0.0004164 0.9995 0.000065 0.007258 Table 8: Effective diffusivities of coconut slices (without treatment of osmotic dehydration) at different temperatures

s.no Temperature (0 C)

Deff (m2/s)

1 50 6.296739E-10 2

60 8.494259E-10

3 70 1.035369E-09 Table 9: Effective diffusivities of coconut slices ( treatment with osmotic dehydration) at different temperatures

s.no Temperature(0 c)

Deff (m2 /s)

1 50 8.029399E-10

2 60 9.550759E-10

3 70 1.225539E-09

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Conclusion

The Midilli model was the best one to describe drying process of the coconut slices for both osmotic dehydrated and without osmotic dehydration of coconut slices . The effective diffusivities increased with the drying temperature and varied from 6.296739x10-10 to 1.035369x10-09 m2/s for without treatment of osmotic dehydration and for osmotic dehydrated coconut slices in salt solution , it was found to be varied from 8.029399x10-10 to 1.225539x10-09 m2/s . The temperature dependence of diffusivity follows Arrhenius type of relationship. The diffusivity constant D0 was estimated as 3.2908 10-6 m2/s for without treatment of osmotic dehydration and osmotic dehydrated coconut slices in salt solution were found to be and 1.10344 10-6 m2/s. The activation energy (Ea) for without treatment of osmotic dehydration of coconut slices and osmotic dehydrated coconut slices in salt solution were evaluated as 22.963 kJ/gmol and 19.454 kJ/gmol. REFERENCES [1] Akpinar, E. K., Midilli, A., & Bicer, Y. (2003). Single layer drying behaviour of potato slices in a convective

cyclone dryer and mathematical modeling. Energy Conversion and Management, 44(10), 16891705. [2] ang Z, Sun J, Liao X, Chen F, Zhao G, Wu J, Hu X (2006) Mathematical modelling on hot air drying of thin layer

apple pomace. Food Res Int 40(1):3946 [3] angavhane, D. R., Sawhney, R. L., & Sarsavadia, P. N. (1999). Effect of various dipping pre-treatment on drying

kinetics of Thompson seedless grapes. Journal of Food Engineering, 39, 211216. [4] A.R.P.Kingsly&D.B.Singh,2007.Drying kinetics of pomegranate arils.journal of Food Engineering 79,741-744. [5] Ayensu, A. (1997). Dehydration of food crops using a solar dryer with convective heat flow. Solar Energy, 59(4

6), 121126. [6] Banga, J.R. & Singh, R.P. (1994). Optimization of air drying of foods. J. Food Engng, 23,189-211. [7] Carbonell, J.V., Pinaga, F., Yusa, V. & Pena, J.L. (1986). Dehydration of paprika and kinetics of color

degradation. J. Food Engng., 5 (3) 179-93. [8] Crisp, J., & Woods, J. L. (1994). The drying properties of rapeseed.Journal of Agricultural Engineering Research,

57, 8997. [9] Demir, V., Gunhan, T., Yagcioglu, A. K., & Degirmencioglu, A. (2004). Mathematical modelling and the

determination of some quality parameters of air-dried bay leaves. Biosystems Engineering, 88(3), 325335 [10]Diamente, L. M., & Munro, P. A. (1991). Mathematical modeling of hot air drying of sweet potato slices.

International Journal of Food Science and Technology, 26, 99. [11]Doymaz I (2004 a). Effect of pre-treatments using potassium metabisulphide and alkaline ethyl oleate on the

drying kinetics of apricots. Biosystems Engineering, 89(3), 281287. [12]Doymaz, I. (2004b)Drying kinetics of white mulberry. Journal of Food Engineering, 61(3), 341346 [13]Ebru Kavak Akpinar,Yasar Bicer (2006).Mathematical modelling and Experimental study on Thin Layer Drying

Model of Strawberry.International Journal of Food Engineering volume 2,issue 1. [14]Ece, M. C., & Cihan, A. (1993). A liquid diusion model for drying rough rice. Transactions of American Society

of Agricultural Engineers, 36, 837840. [15]Erenturk, S., Gulaboglu, M. S., & Gultekin, S. (2004). The thin layer drying characteristics of rosehip.

Biosystems Engineering, 89(2), 159166. [16]Ertekin, C., & Yaldiz, O. (2004). Drying of eggplant and selection of a suitable thin layer drying model. Journal

of Food Engineering, 63,349359. [17]FAOSTAT. Production. Crops. Coconut, 2013. http://faostat.fao.org. [18]Janjaia, S., M. Precopped, N. Lamlerta, B. Mahayotheeb,B.K. Balac, M. Nagle, and J. Mllerd, 2011. Thin layer

drying of litchi (Litchi chinensis Sonn.). Food Bioprod. Process. 89: 194-201 [19]Kassem, A. S. (1998). Comparative studies on thin layer drying models For wheat. In 13th International congress

on agricultural engineering, 26 February, Morocco, vol. 6 [20]Lahsasni, S., Kouhila, M., Mahrouz, M., & Jaouhari, J. T. (2004). Drying kinetics of prickly pear fruit (Opuntica

ficus indica). Journal of Food Engineering, 61(2), 173179. [21]Lopez, A., Iguaz, A., Esnoz, A., & Virseda, P. (2000). Thin-layer drying behaviour of vegetable wastes from

wholesale market. Drying Technology, 18(45), 9951006. [22]Madamba, P. S., Driscoll, R. H., & Buckle, K. A. (1996). The thin layer drying characteristics of garlic slices.

Journal of Food Engineering, 29, 7597.

ISSN: 2395-0560




[23]Mazza, G. & Le Maguer, M. (1980). Dehydration of onion: Some theoretical and practical considerations. J. Food Tech., 15, 181-94.

[24]Midilli A, Kucuk H, Yapar ZA (2002) New model for single-layer drying. Drying Technol 20(7):15031513. [25]N.K.Rastogi & K.S.M.S.Raghavarao , 1994. Kinetics of osmotic dehydration of coconut.Journal of Food process

Engineering.18;187-197. [26]Overhults, D. G., White, H. E., Hamilton, H. E., & Ross, I. J. (1973).Drying soybeans with heated air.

Transactions of the ASAE, 16, 112113. [27]Pala M; Mahmutoglu T; Saygi B (1996). Effects of pretreatments on the quality of open-air and solar dried

products. Nahrung/Food, 40, 137141. [28]Panchariya, P. C., Popovic, D., & Sharma, A. L. (2002). Thin layer modeling of black tea drying process. Journal

of Food Engineering, 52, 349357. [29]Rahman, M. S., Perera, C. O., & Thebaud, C. (1998). Desorption isotherm and heat pump drying kinetics of peas.

Food Research International, 30(7), 485491. [30]Suarez, C., Viollaz, P., & Chirife, J. (1980a). Kinetics of soybean drying. In A. S. Mujumdar, Drying'80 (pp.

251255). Washington, DC, USA: Hemisphere. [31]Togrul, I. T., & Pehlivan, D. (2002). Mathematical modelling of solar drying of apricots in thin layers. Journal of

Food Engineering, 55, 209216. [32]Wang CY, Singh RP (1978) Use of variable equilibrium moisture content in modelling rice drying. Trans Am Soc

Agric Eng 11:668672

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Thin Layer Drying Kinetics for Osmotic Dehydrated Coconut Slices in Salt Solution

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