Research Article Investigation of Solar Drying of Ginger ...downloads.hindawi.com/journals/cje/2014/305823.pdf · Research Article Investigation of Solar Drying of Ginger ( Zingiber

Research ArticleInvestigation of Solar Drying of Ginger (Zingiber officinale)Emprical Modelling Drying Characteristics and Quality Study

A Waheed Deshmukh12 Mahesh N Varma2 Chang Kyoo Yoo3 and Kailas L Wasewar23

1 Priyadarshini Institute of Engineering and Technology RTMN University Nagpur Maharashtra 440018 India2 Advanced Separations and Analytical Laboratory Department of Chemical EngineeringVisvesvaraya National Institute of Technology (VNIT) Nagpur Maharashtra 440011 India

3 Environmental Management amp Systems Engineering Lab (EMSEL) Department of Environmental Science and EngineeringCollege of Engineering Kyung Hee University Seocheon-dong 1 Giheung-gu Yongin-Si Gyeonggi-Do 446-701 Republic of Korea

Correspondence should be addressed to Kailas L Wasewar k wasewarrediffmailcom

Received 13 December 2013 Accepted 9 February 2014 Published 13 March 2014

Academic Editors Z Li and I Ortiz

Copyright copy 2014 A Waheed Deshmukh et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Drying is a simultaneous heat and mass transfer energy intensive operation widely used as a food preservation technique In viewof improper postharvest methods energy constraint and environmental impact of conventional drying methods solar dryingcould be a practical economical and environmentally reliable alternative In the present paper applicability of mixed mode solarcabinet dryer was investigated for drying of commercially important and export oriented ginger Freshly harvested ginger sliceswere successfully dried from initial moisture content of 62150 to 1219 (db) and their drying characteristics quality parametersand kinetics were evaluated The results showed that present solar dryer could be successfully applied for drying of ginger in viewof quality reduced drying time and zero energy requirement as compared to conventional open sun drying and convective dryingtechniques respectively Drying curves showed that drying occurred in falling rate period and no constant period was observedThe effective moisture diffusivity was determined by using Fickrsquos second law and found to be 1789times10minus9m2sThe drying data wasfitted to five thin layer drying models and compared using statistical criteria Page model was found to be most suitable to describethe drying kinetics of ginger in solar dryer under natural convection among the tested models

1 Introduction

Drying has a vital role in postharvest processing It hasalways been of great importance for conserving agriculturalproducts and for extending the food shelf life [1] Many of themoisture-mediated deterioration reactions and reproductionof micro-organisms causing decay can be prevented byremoval of moisture by appropriate dryingmethod Howeverlimited resources of fossil fuels and extensive usage areresponsible for adverse effects on environment and also eco-nomic viability Open sun drying of various crops is the mostwidespread conventional method for food preservation prac-ticed in many urban and rural areas of developing countriesThe major disadvantage of this technique is low quality andhygienic problems of the product The product gets contam-inated from dust insects rodents and other animals which

seriously degrade the food quality and ultimately resultsin a negative trade potential and economical worth Laborrequirement long drying time (2-3 days) and direct exposureof the produce to sun and wind are the further difficultieswith this method In order to ensure continuous food supplyto growing population and to enable the farmers to producehigh quality marketable products efficient and at the sametime affordable drying methods are necessary Varieties ofmechanical energy driven dryers are available for preventingthe deterioration of products and to reduce the drying timeThese conventional dryers and drying techniques are not eco-nomical due to high energy cost [2] Commercially variousenergy based drying techniques such as forced convectivedrying fluidized bed drying heat pump drying microwavedrying freeze drying and many more are available andwidely practiced Diminishing reserves of fossil fuels and

Hindawi Publishing CorporationChinese Journal of EngineeringVolume 2014 Article ID 305823 7 pageshttpdxdoiorg1011552014305823

2 Chinese Journal of Engineering

increased cost havemade drying as an energetically expensiveand unaffordable technique for farmers Studies have shownthat even small and most simple oil-fired batch dryers arenot applicable for most farmers due to lack of capitalinvestment and insufficient supply of energy for the operationof dryers Therefore the introduction of low cost and locallymanufactured solar dryers can offer a promising alternative toreduce the tremendous postharvest losses The opportunityto produce high quality marketable products seems to be achance to improve the economic situation of the farmersHowever taking into account the low income of the ruralpopulation the relatively high investment for energy baseddryers still remains a barrier to wide application In view ofthis solar dryers can be a good alternative over conventionaldryers and open sun drying technique Solar energy is freeabundant environmentally clean and therefore is recognizedas one of the most promising alternative energy In nearfuture the large-scale introduction of solar energy systemsdirectly converting solar radiation into heat can be lookedforward [3] Moderate amounts of fuel wood or fossil fuelscurrently used in developing countries for the process offood and crop can be replaced by proper use of solar dryingtechnologies [4] The climatic conditions in India are goodwith about 300 clear and sunny days and theoretical solarpower reception on its land area is about 5 trillion kWhyearThe daily average solar energy incident over India variesfrom 5 to 7 kWhm2 with about 1500ndash2000 sunshine hoursper year depending upon location which is far more thancurrent energy consumption [5] The study carried out byChavda andKumar [6] indicates that cost of dryingwith solarpower is only one-third as compared to the cost using a dryerbased on conventional fuels These solar dryers allow forcontrolled drying by managing the drying parameters suchas moisture content air temperature humidity and air flowrate Adequate drying helps to preserve the flavor textureand color of the food which leads to a better quality product[7] Thus solar dryers are more economical as compared toother dryers if properly employed Appropriate use of solardrying has significant potential especially in agriculturalareas which suffer from a high proportion of postharvestlosses through food spoilage

Ginger is an important spice cash crop of the world It isone of the earliest known oriental spices and is being culti-vated in India for both as fresh vegetable and as a dried spiceGinger is obtained from the rhizomes of Zingiber officinaleThe ginger family is a tropical group especially abundantin Indo-Malaysian region consisting of more than 1200plant spices in 53 genera The area under the cultivation inIndia is 1086 thousands hectors and the total productionof the country is 5178 thousand tons [8] Ginger and itsproducts have varied applications in culinary preparationbakery products toiletry products perfume industries meatproducts wine and soft drinks making Dried ginger is usedboth as a spice and medicine It contains an essential oilwhich imparts an aroma an oleoresin responsible for thepungent smell starch gums proteins carbohydrate mineralmatter andfiber [8] InAyurveda it is termed as an importantmedicine to cure many diseases such as rheumatism pilesdyspepsia alcoholic gastritis fabric disease throat problems

cholera morbus neuralgia and pulmonary and catarrhaldiseases It is expected that the world demand of gingerwill double in the next five years [9] The quality of gingerproduced in India has high content of aroma and pungencyand it is also organic But due to improper postharvestprocessing most of the ginger is to be consumed as a freshvegetable and also some of the good qualities such as visualappeal texture aroma flavor structure and color of thematerial get affected

Several studies have been reported on a variety of solardryers for drying different fruits vegetables and grains [16]Few of them are amaranth [17] seed pumpkin [18] sweetpepper and garlic [19] tomato seed [20] grape [21] pineapple[22] fig and onion [23] sour cherry [24] date palm [25]mango slices [26] and so forth Design of different types ofsolar dryer has been reported by Phoeun et al [27] It includesdesign of solar cabinet dryers solar box dryers tunnel dryersand solar tray dryers for rural farmers Although variousattempts have been made to study the solar drying of variousagricultural products very few works are reported on thesolar drying of ginger and effect on quality parameters par-ticularly in mixed mode solar cabinet dryer In view of thisthe present study was undertaken to assess the applicabilityof mixed mode solar cabinet dryer for drying of gingerThis study includes the investigation of drying characteristicskinetics effective diffusivity and evaluation of some qualityparameters of ginger in solar drying system The experi-mental drying data was fitted to five mathematical modelsavailable in the literature and best suitedmodel for predictingdrying kinetics of ginger was determined among the testedmodels

2 Material and Methods

21 Experimental Setup A mixed mode box-cabinet naturalcirculation solar dryer was developed for the present studyas shown in Figure 1 The dryer consists of a primary solarcollector (1 times 05)m A transparent sheet was located over thecollector The fresh air was sucked and heated through theair duct and flows to the drying chamber A secondary solarcollector (075 times 05)m oriented north-south was coveredwith a single layer of 015 times 10minus6 thick UV stabilized poly-ethylene film and hinged at the top of the drying chamberIt allows the solar radiations to drying chamber and furtherenhances the drying rate by greenhouse effect The dryingchamber was coated with black paint thermally insulatedwith asbestos sheets to minimize the heat loss provided withthe support for sample holding mesh trays having area 1m2The general rule of thumb is that 1m2 of tray area is neededto layout 10 kg of produce The air is warmed up during itsflow through a low pressure drop thermosyphonic primarysolar collector The moisture is removed by natural convec-tion and greenhouse effect by secondary solar collector indrying chamberThemoist air is then discharged through theair vents provided at the top of the drying chamber Dryingstudies in solar cabinet dryer were conducted with tworeplicates Accurately weighted ginger slices (5 kg per batch)of initial moisture content 6215 db were evenly distributedon the sample holding mesh trays After predetermined time

Chinese Journal of Engineering 3

T3

T2

Sliding door

Perforated trays

Drying chamber

Ginger slices

Moist airSecondary solar collector

Solar radiations

Fresh dry air inletT1

Primary solar collector

Figure 1 Mixed mode box-cabinet natural circulation solar dryer

interval reduction of weight of material was noted by usingElectronic Weighing balance (Wensar Ltd India HPB 310least count 01 gm)The temperature of the air was monitoredat primary solar collector drying chamber and at the exitof drying chamber by PT-100 sensor thermocouples withaccuracy of plusmn05∘C at regular time intervals

22 Sample Preparations Fresh ginger was purchased fromlocal market of Nagpur India and washed thoroughly toremove surface dust and extraneous matter under runningwaterThe clean ginger was hand peeled by knife and cut intothin slices of average thickness of 6 plusmn 05mmThe slices werekept at ambient for one hour to remove surface moistureTheinitial moisture content of fresh ginger was determined byhot air oven drying method [28] Accurately weighed sample(100 gm) of ginger was placed in a laboratory oven at theconstant temperature of 60∘C until the constant weight wasachieved Five replications were taken and average value wascalculated on dry basis by following equations

Moisture content on dry basis ( db)

119872initial =119882119908

minus119882119889

119882119889

times 100 (1)

where 119872initial is the initial moisture content of ginger ondb119882

119908

is thewetweight and119882119889

is the dryweight of gingerin kg

Drying Rate The drying rates at different timing during solardrying were computed in all experimental conditions usingfollowing relationship [29]

119889119872

119889119879=119872119900

minus119872119905

119905 (2)

where 119889119872119889119905 is drying rate (kg waterkg of material min) 119905is time (min) and119872

119900

and119872119905

are the initial and finalmoisturecontent respectively

Effective Diffusivity Drying process in falling rate period forfood materials is mostly governed by diffusion mechanism[1] Fickrsquos second diffusion law has been widely used to

Table 1 Thin layer drying models applied to drying data of ginger

Model name Model equation ReferencesNewton MR = exp(minus119896119905) [10 11]Page MR = exp(minus119896119905119899) [12]Modified Page MR = exp[(minus119896119905)119899] [13]Henderson and Pabis MR = 119886 exp(minus119896119905) [14]Wang and Sing MR = 1 + 119886119905 + 1198871199052 [15]

describe the moisture removal in falling rate periods Theeffective diffusivity of the material can be calculated byassuming constant moisture diffusivity temperature andnegligible shrinkage during drying process using the follow-ing equation

ln MR = ln ( 81205872

) minus1205872

119863eff119905

1198712

(3)

where 119863eff is the effective diffusivity 119871 is the half of thethickness of ginger slice in meter and 119905 is the correspondingdrying time in sec The Effective diffusivity can be calculatedby plotting experimental ln(MR) versus drying time gives astraight line with slope of

Slope =1205872

119863eff1198712

(4)

Mathematical Modeling of Drying Data Thin layer dryingprocedure is generally practiced for characterizing the dryingparameters [30] The empirical models present the directrelationship between the average moisture content and dry-ing time by means of regression analysis neglecting thefundamental of drying process Full scale experimentation ofdehydration processes for different products is not econom-ically feasible hence employing the simulation model fordrying rate predication may be an easy and valuable tool [31]To select a suitable model for describing the drying processof ginger experimental results were fitted to various thinlayer drying models which are summarized in Table 1 Themoisture ratio of ginger during the drying was calculated byusing the following equation

MR =119872119905

minus119872119890

119872119900

minus119872119890

(5)

where119872119905

119872119900

and119872119890

are the moisture content on dry basisat any time initial and equilibrium respectively The valueof dynamic equilibrium moisture content is relatively smallas compared to119872

119905

and119872119900

hence the error involved in thesimplification is negligible [32] and hence moisture ratio wascalculated as

MR =119872119905

119872119900

(6)

Suitability of the best model was determined by statisticalcriteria namely coefficient of determination (1198772) reduced


chi-square (1205942) root mean square error (RMSE) and percentrelative error described as [23]

1205942

=

sum119873

119894=1

(MRexp119894 minusMRpre119894)2

119873 minus 119899

(7)

RMSE = 1119873

[

[

sum119873

119894=1


119873

]

]

12

(8)

120576 () =10038161003816100381610038161003816100381610038161003816100381610038161003816

(MRpre119894 minusMRexp119894)

MRexp119894times 100

10038161003816100381610038161003816100381610038161003816100381610038161003816

(9)

whereMRexp119894 andMRpre119894 are the experimental and predictedmoisture ratio for the same measurement respectively 119873 isthe number of observation and 119899 is the number of constantsin drying model The best model was chosen as the one withhigher coefficient of determination least reduced chi squareroot mean square error and percent relative error [33]

Rehydration Study Rehydration study was carried out byadding 3 gm of dried ginger in 100mL distilled water at roomtemperature (34plusmn1∘C) the samples were weighed at a regulartime interval until the constant weight was achieved by thesample After rehydration samples were taken out surfacemoisture was absorbed carefully with tissue paper and thenweighed The rehydration capacity was calculated as follows[10]

Rehydration capacity =119882119903

119882119889

(10)

where 119882119903

is the weight after rehydration kg and 119882119889

is theweight of dried ginger kg

Color Analysis Color analysis for fresh open sun-dried andsolar-dried ginger sample was done on three randomlyselected slices at 10 different locations The color of bothsamples was determined by using Chromameter CR-400(Minolta Japan) Three parameters for the dried samples119871lowast (lightness) 119886lowast (redness) and 119887lowast (yellowness) were used

to study the changes in color 119871lowast represent the lightness ordarkness of the sample on the scale of 0ndash100 where white =100 and dark = 0 Hunter 119886lowast represent redness (+) orgreenness (minus) Hunter 119887lowast represent yellowness (+) or blueness(minus)The total color difference (Δ119864) was determined using thefollowing equations [34]

Δ119864 = radic(Δ119871lowast

)2

+ (Δ119886lowast

)2

+ (Δ119887lowast

)2 (11)

Δ119871lowast

= 119871lowast

minus 119871lowast

119900

Δ119886lowast

= 119886lowast

minus 119886lowast

119900

Δ119887lowast

= 119887lowast

minus 119887lowast

119900

(12)

Higher value of Δ119864 indicates greater color change fromreference material 119871lowast

119900

119886lowast119900

and 119887lowast119900

are the color parametersof fresh samples used as the reference

0

10

20

30

40

50

60

70

80

0 100 200 300 400 500 600Drying time (min)

Temperature inside solar dryer (mean 57 plusmn 85)∘C

Tem

pera

ture

(∘C)

Ambient temperature (mean = 31 plusmn 45)∘C

Figure 2 Comparison of ambient and dryer temperature withdrying time

3 Results and Discussion

31 Drying Characteristics Figure 2 compares the tempera-ture developed inside the solar cabinet dryer and ambienttemperature throughout the drying period It was observedthat the temperature developed in the dryer is always greaterthan the ambient temperature The temperature in the driervaried between 38∘C and 70∘C and a considerable differencewas observed between ambient and dryer temperature Thetemperature in the dryer increases after 200min (approx-imately 12 to 1 pm) remarkably as the sun attained thehighest position in the sky The angle of insolation at thisstage became closest to 90∘ this leads to the intense solarradiations The average temperature inside the dryer wasfound to be 57 plusmn 85∘C For most of the food materialsthe recommended drying temperature is 60ndash70∘C [35] Thisconfirms that the present solar cabinet dryer can be effectivelyused for drying of agricultural product such as ginger Thedrying curve for ginger slices is shown in Figure 3 wherethe moisture content decreases continuously with time Thedrying rate was found to be faster initially up to 200minAs the drying progressed the drying rate decreased withtime It is typical drying behavior for agricultural materialsreported by many researchers [9 36] Ginger with initialmoisture content 62150 (db) was successfully dried up to1219 (db) The maximum drying period required for thiswas observed to be 480min (8 hours) which is quiet less ascompared to conventional open sun drying (2-3 days) [9]

As shown in Figure 4 drying rate decreases continuouslywith decreasing moisture contentThis is due to high amountof free moisture availability which was easily removed inthe initial stage of drying [37] The entire drying processwas occurred in falling rate period and constant rate periodwas found to be absent in the present drying study This isdue to the fact that material surface is no longer saturatedwith water and drying rate is controlled by diffusion ofmoisture from interior of solid to the surface It was alsoobserved from Figure 5 that rate of drying shows fluctuations


0

100

200

300

400

500

600

0 100 200 300 400 500 600

Moi

sture

cont

ent (

d

b)

Drying time (min)

Figure 3 Variation of moisture content of ginger with drying time

0

0005

001

0015

002

0025

003

0035

004

0 100 200 300 400 500 600Moisture content ( db)

Dry

ing

rate

(kg

wat

erk

g dr

y m

ater

ialmiddotm

in)

Figure 4 Variation of drying rate of ginger with moisture content

at some instants and decreases with time These fluctuationsin the drying rate may be due to change in intensity of solarradiations falling on dryer Hence drying rate will depend onmoisture content as well as intensity of solar radiationsTheseresults are in agreement with the observations of the earlierresearchers based on the thin layer drying studies [17]

32 Effective Diffusivity Present study reveals that dryingmainly occurred in falling rate period During the fallingrate drying period the mass transfer is governed by internalresistance In this case Fickrsquos second law can be used tocalculate effective diffusivity of the material The effectivediffusivity of the ginger in present solar dryer was calculatedby plotting ln(MR)with drying time as shown in Figure 6 andusing (3) where slope of the straight line gives the effectivediffusivity of the sampleThe effective diffusivity of the gingerslices in present solar dryer was found to be 1789times10minus9m2swhich is within the range of 10minus9 to 10minus11m2s reported inthe literature for drying of food material

33 Mathematical Modelling of Drying Data The regressionanalysis was done for five selected models from Table 1 byrelating the drying time and dimensionless moisture ratioThe suitability of the model was decided based on value of

0

0005

001

0015

002

0025

003

0035

004

0 100 200 300 400 500 600Drying time (min)

Dry

ing

rate

(kg

wat

erk

g dr

y m

ater

ialmiddotm

in)

Figure 5 Variation of drying rate of ginger with drying time

0

05

0 100 200 300 400 500 600Drying time (min)

y = minus00049x + 03131

R2 = 09814

minus05

minus1

minus15

minus2

minus25

ln (M

R)

Figure 6 Plot of ln(MR) versus drying time for determination ofeffective diffusivity

coefficient of determination (1198772) should be close to one lowvalue of chi-square (1205942) root mean square error (RMSE)and percent relative error [17] The model coefficients andparameters are presented inTable 2 From regression analysisit can be seen that the Page model satisfactorily describes thedrying kinetics of the ginger with 1198772 of 09823 1205942 of 0003RMSE of 00538 and 120576 () of 178

Figure 7 presents the variation of experimental and pre-dicted moisture ratio using the Page model with drying timefor ginger It was observed the Page model shows the bestagreement between experimental and predicted values ofmoisture ratio The experimental moisture ratio was plottedagainst the predicted value of moisture ratio to validate thePage model as shown in Figure 8 The result showed smoothand scattered data points around the fitted lineThis confirmsthe goodness of the tested developed model to estimate themoisture content of ginger in drying process for present solardryer

34 Quality Analysis The success of any drying method lieson quality of product dried Rehydration capacity and alter-ation in color are the major deciding parameters The rehy-dration capacity and total color change index value Δ119864 forsolar and open sun-dried ginger was calculated by using (10)


Table 2 Statistical results and model coefficients obtained from selected thin layer drying models for solar cabinet drying of ginger

Model number Model Model coefficients andconstants 119877

2 RMSE 1205942

120576 ()

1 Newton k = 00039 09269 1008 00106 114

2 Page k = 00074n = 1675 09823 00538 0003 178

3 Henderson and Pabis k = 00047a = 1305 09638 0014 00049 527

4 Wang and Singh a = minus00025b = 1 times 10minus6 0946 00731 00058 683

5 Modified Page model k = 00034n = 1675 09753 0055 00034 347

0010203040506070809

1

0 100 200 300 400 500

Moi

sture

ratio

Drying time (min)

Moisture ratio (experimental)Moisture ratio (predicted)

Figure 7 Comparison of experimental moisture and predictedmoisture ratio with drying time by Page model

0010203040506070809

1

0 02 04 06 08 1

Pred

icte

d m

oistu

re ra

tio

Experimental moisture ratio

Figure 8 Comparison of experimental and predictedmoisture ratioby Page model

and (11) respectively The results obtained show that solar-dried ginger yields a better quality in terms of color andrehydration capacity as compared to open sun drying TheΔ119864 and rehydration capacity was found to be 3105 5232 and365 and 212 for solar and open sun dried ginger respectivelyThis confirmed the appropriate drying without considerableshrinkage and color and present solar drier gives betterproduct quality as compared to open sun drying and quietcomparative to some other well developed techniques [11]

4 Conclusion

In the present study solar cabinet dryer exhibited sufficientability to dry ginger reasonably rapidly to a safe moisturelevel without any energy investment and positive environ-mental impact Simultaneously it ensures a superior qualityof the dried product over the conventional open sun dryingmethod The maximum drying time required to dry gingerfrom 62150 to 1219 (db) was found to be 450 to 480minutes The drying time was found to be drying rate andmoisture content dependent Thin layer drying studies showthat constant rate period is absent and the entire dryingprocess occurred in falling rate period The experimentaldrying data was fitted to five different mathematical modelsand compared using statistical criteria Page model wasfound to be best suitable to describe the drying kinetics ofginger among the tested modelsThemoisture ratio obtainedexperimentally and predicted by Page model shows goodagreement and fitted smoothly to straight line The modelattained the highest value of1198772 lowest value of1205942 and RMSE(1198772 098231205942 0003 RMSE 00538) Lowest value of percentrelative error ( 120576 178) further confirmed its superiorityover the other models In view of low capital investmentzero emission and energy requirement as compared toother conventional drying methods the results confirmed thepotential of solar cabinet dryer for drying of ginger and otheragricultural products

Conflict of Interests

The authors declare that they have no conflict of interestsregarding the publication of this paper

References

[1] I Doymaz ldquoAir-drying characteristics of tomatoesrdquo Journal ofFood Engineering vol 78 no 4 pp 1291ndash1297 2007

[2] G Gurlek N Ozbalta and A Gungor ldquoSolar tunnel dryingcharacteristics and mathematical modelling of tomatordquo JournalofThermal Science and Technology vol 29 no 1 pp 15ndash23 2009

[3] L M Bal S Satya and S N Naik ldquoSolar dryer with thermalenergy storage systems for drying agricultural food products areviewrdquo Renewable and Sustainable Energy Reviews vol 14 no8 pp 2298ndash2314 2010


[4] K Sopian A Sayigh and Y Othman ldquoSolar assisted dryingsystems innovative technologies for agricultural and marineproductsrdquo Publications of The Islamic Educational Scientificand Cultural Organization ISESCO-1427AH 2006

[5] T Muneer M Asif and S Munawwar ldquoSustainable productionof solar electricity with particular reference to the IndianeconomyrdquoRenewable and Sustainable Energy Reviews vol 9 no5 pp 444ndash473 2005

[6] T Chavda and N Kumar ldquoSolar dryers for high value agroproducts at Sprerirdquo inProceedings of the International Solar FoodProcessing Conference Indore India January 2009

[7] D E Whitfield ldquoSolar dryer systems and the internet impor-tant resources to improve food preparationrdquo in Proceedings ofthe International Conference on Solar Cooking Kimberly SouthAfrica November 2000

[8] H Rahman R Karuppaiyan K Kishor and R DenzongpaldquoTraditional practices of ginger cultivation in north east IndiardquoIndian Journal of Traditional Knowledge vol 8 no 1 pp 23ndash282009

[9] K Singh D Tiroutchelvame and S Patel ldquoDrying character-istics of ginger flakesrdquo in Proceedings of the 16th InternationalDrying Symposium (IDS rsquo08) pp 1383ndash1386 Hydrabad India2008

[10] A W Deshmukh M N Varma C K Yoo and K L WasewarldquoEffect of ethyl oleate pretreatment on drying of ginger char-acteristics and mathematical modellingrdquo Journal of Chemistryvol 2013 Article ID 890384 6 pages 2013

[11] W K Lewis ldquoThe rate of drying of solid materialsrdquo Journal ofIndustrial Engineering and Engineering Chemistry vol 13 pp427ndash432 1921

[12] G Page Factors influencing the maximum rates of air dryingshelled corn in thin layers [MS thesis] Purdue University WestLafayette Ind USA 1949

[13] S M Henderson and S Pabis ldquoGrain drying theory I tem-perature effect on drying coefficientrdquo Journal of AgriculturalEngineering Research vol 6 pp 169ndash174 1961

[14] Z Wang J Sun X Liao et al ldquoMathematical modeling onhot air drying of thin layer apple pomacerdquo Food ResearchInternational vol 40 no 1 pp 39ndash46 2007

[15] C Y Wang and R P Singh ldquoA single layer drying equation forrough ricerdquo Paper No 78-3001 American Society of Agricul-tural Engineers St Joseph Mich USA 1978

[16] A W Deshmukh K L Wasewar and M N Verma ldquoSolardrying of food materials as an alternative for energy crisis andenvironmental protectionrdquo International Journal of ChemicalSciences vol 9 no 3 pp 1175ndash1182 2011

[17] K Ronah C Knali J Mailutha and D Shitanda ldquoThin layerdrying kinetics of amaranth grains in natural convection solartent dryerrdquo African Journal of Food Agricultural and NutritionDevelopment vol 10 no 3 pp 2218ndash2233 2010

[18] K Sacilik ldquoEffect of drying methods on thin-layer dryingcharacteristics of hull-less seed pumpkin (Cucurbita pepo L)rdquoJournal of Food Engineering vol 79 no 1 pp 23ndash30 2007

[19] M Condorı R Echazu and L Saravia ldquoSolar drying of sweetpepper and garlic using the tunnel greenhouse drierrdquoRenewableenergy vol 22 no 4 pp 447ndash460 2001

[20] D S Sogi U S Shivhare S K Garg and A S Bawa ldquoWatersorption isotherm and drying characteristics of tomato seedsrdquoBiosystems Engineering vol 84 no 3 pp 297ndash301 2003

[21] C Tiris N Ozbalta M Tiris and I Dincer ldquoExperimentaltesting of a new solar dryerrdquo International Journal of EnergyResearch vol 18 no 4 pp 483ndash490 1994

[22] B K Bala M R A Mondol B K Biswas B L D Chowduryand S Janjai ldquoSolar drying of pineapple using solar tunneldrierrdquo Renewable Energy vol 28 no 2 pp 183ndash190 2003

[23] Y M Gallali Y S Abujnah and F K Bannani ldquoPreservationof fruits and vegetables using solar drier a comparative studyof natural and solar drying III chemical analysis and sensoryevaluation data of the dried samples (grapes figs tomatoes andonions)rdquo Renewable Energy vol 19 no 1-2 pp 203ndash212 2000

[24] E K Akpinar and Y Bicer ldquoModelling of thin layer dryingkinetics of sour cherry in a solar dryer and under open sunrdquoJournal of Scientific and Industrial Research vol 66 no 9 pp764ndash771 2007

[25] A Boubekri H Benmoussa and D Mennouche ldquoSolar dryingkinetics of date palm fruits assuming a step-wise air tempera-ture changerdquo Journal of Engineering Science and Technology vol4 no 3 pp 292ndash304 2009

[26] A O M Akoy M A Ismail F A Ahmed and W LueckeldquoDesign and construction of solar dryer for mango slicesrdquoInternational Renewable Energy Review vol 4 no 2 pp 1ndash92007

[27] S Phoeun N Phol O Romny P Pen and S Bun ldquoSolar dryersfor small farmers and households in Cambodiardquo in Proceedingof the Regional Conference onWorlds Renewable Energy pp 18ndash21 Jakarta Indonesia 2005

[28] S Ranganna A Handbook of Analysis and Quality Control forFruits and Vegetable Products Tata McGraw-Hill New DelhiIndia 2nd edition 1995

[29] R Shalini A Ranjan and N Kumar ldquoStudies on the dryingcharacteristics of apple pomace on tray dryerrdquo in Proceedingsof the 16th International Drying Symposium (IDS rsquo08) pp 1636ndash1640 Hydrabad India 2008

[30] N A Akgun and I Doymaz ldquoModelling of olive cake thin-layerdrying processrdquo Journal of Food Engineering vol 68 no 4 pp455ndash461 2005

[31] A Steinfeld and I Segal ldquoA simulationmodel for solar thin layerdrying processrdquo Drying Technology vol 4 no 4 pp 535ndash5541986

[32] I Doymaz O Gorel and N A Akgun ldquoDrying characteristicsof the solid by-product of olive oil extractionrdquo BiosystemsEngineering vol 88 no 2 pp 213ndash219 2004

[33] H O Menges and C Ertekin ldquoMathematical modeling of thinlayer drying of golden applesrdquo Journal of Food Engineering vol77 no 1 pp 119ndash125 2006

[34] S Phoungchandang and S Saentaweesuk ldquoEffect of two stagetray and heat pump assisted-dehumidified drying on dryingcharacteristics and qualities of dried gingerrdquo Food and Bioprod-ucts Processing vol 89 no 4 pp 429ndash437 2011

[35] R Abalone A Cassinera A Gaston and M A Lara ldquoSomephysical properties of amaranth seedsrdquo Biosystems Engineeringvol 89 no 1 pp 109ndash117 2004

[36] H R Gazor and S Minaei ldquoInfluence of temperature and airvelocity on drying time and quality parameters of pistachio(Pistacia vera L)rdquo Drying Technology vol 23 no 12 pp 2463ndash2475 2005

[37] T Garware N Sutar and B Thorat ldquoDrying of tomato usingdifferent drying methods comparison of drying kinetics andrehydration ratiordquo in Proceedings of the 16th InternationalDrying Symposium (IDS rsquo2008) pp 1427ndash1432 Hydrabad India2008

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014


Active and Passive Electronic Components

Control Scienceand Engineering

Journal of



RotatingMachinery


Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design



Shock and Vibration


Civil EngineeringAdvances in

Acoustics and VibrationAdvances in



Electrical and Computer Engineering

Journal of

Advances inOptoElectronics


Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of


Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014


Chemical EngineeringInternational Journal of Antennas and

Propagation




Navigation and Observation



DistributedSensor Networks



increased cost havemade drying as an energetically expensiveand unaffordable technique for farmers Studies have shownthat even small and most simple oil-fired batch dryers arenot applicable for most farmers due to lack of capitalinvestment and insufficient supply of energy for the operationof dryers Therefore the introduction of low cost and locallymanufactured solar dryers can offer a promising alternative toreduce the tremendous postharvest losses The opportunityto produce high quality marketable products seems to be achance to improve the economic situation of the farmersHowever taking into account the low income of the ruralpopulation the relatively high investment for energy baseddryers still remains a barrier to wide application In view ofthis solar dryers can be a good alternative over conventionaldryers and open sun drying technique Solar energy is freeabundant environmentally clean and therefore is recognizedas one of the most promising alternative energy In nearfuture the large-scale introduction of solar energy systemsdirectly converting solar radiation into heat can be lookedforward [3] Moderate amounts of fuel wood or fossil fuelscurrently used in developing countries for the process offood and crop can be replaced by proper use of solar dryingtechnologies [4] The climatic conditions in India are goodwith about 300 clear and sunny days and theoretical solarpower reception on its land area is about 5 trillion kWhyearThe daily average solar energy incident over India variesfrom 5 to 7 kWhm2 with about 1500ndash2000 sunshine hoursper year depending upon location which is far more thancurrent energy consumption [5] The study carried out byChavda andKumar [6] indicates that cost of dryingwith solarpower is only one-third as compared to the cost using a dryerbased on conventional fuels These solar dryers allow forcontrolled drying by managing the drying parameters suchas moisture content air temperature humidity and air flowrate Adequate drying helps to preserve the flavor textureand color of the food which leads to a better quality product[7] Thus solar dryers are more economical as compared toother dryers if properly employed Appropriate use of solardrying has significant potential especially in agriculturalareas which suffer from a high proportion of postharvestlosses through food spoilage

Ginger is an important spice cash crop of the world It isone of the earliest known oriental spices and is being culti-vated in India for both as fresh vegetable and as a dried spiceGinger is obtained from the rhizomes of Zingiber officinaleThe ginger family is a tropical group especially abundantin Indo-Malaysian region consisting of more than 1200plant spices in 53 genera The area under the cultivation inIndia is 1086 thousands hectors and the total productionof the country is 5178 thousand tons [8] Ginger and itsproducts have varied applications in culinary preparationbakery products toiletry products perfume industries meatproducts wine and soft drinks making Dried ginger is usedboth as a spice and medicine It contains an essential oilwhich imparts an aroma an oleoresin responsible for thepungent smell starch gums proteins carbohydrate mineralmatter andfiber [8] InAyurveda it is termed as an importantmedicine to cure many diseases such as rheumatism pilesdyspepsia alcoholic gastritis fabric disease throat problems

cholera morbus neuralgia and pulmonary and catarrhaldiseases It is expected that the world demand of gingerwill double in the next five years [9] The quality of gingerproduced in India has high content of aroma and pungencyand it is also organic But due to improper postharvestprocessing most of the ginger is to be consumed as a freshvegetable and also some of the good qualities such as visualappeal texture aroma flavor structure and color of thematerial get affected

Several studies have been reported on a variety of solardryers for drying different fruits vegetables and grains [16]Few of them are amaranth [17] seed pumpkin [18] sweetpepper and garlic [19] tomato seed [20] grape [21] pineapple[22] fig and onion [23] sour cherry [24] date palm [25]mango slices [26] and so forth Design of different types ofsolar dryer has been reported by Phoeun et al [27] It includesdesign of solar cabinet dryers solar box dryers tunnel dryersand solar tray dryers for rural farmers Although variousattempts have been made to study the solar drying of variousagricultural products very few works are reported on thesolar drying of ginger and effect on quality parameters par-ticularly in mixed mode solar cabinet dryer In view of thisthe present study was undertaken to assess the applicabilityof mixed mode solar cabinet dryer for drying of gingerThis study includes the investigation of drying characteristicskinetics effective diffusivity and evaluation of some qualityparameters of ginger in solar drying system The experi-mental drying data was fitted to five mathematical modelsavailable in the literature and best suitedmodel for predictingdrying kinetics of ginger was determined among the testedmodels

2 Material and Methods

21 Experimental Setup A mixed mode box-cabinet naturalcirculation solar dryer was developed for the present studyas shown in Figure 1 The dryer consists of a primary solarcollector (1 times 05)m A transparent sheet was located over thecollector The fresh air was sucked and heated through theair duct and flows to the drying chamber A secondary solarcollector (075 times 05)m oriented north-south was coveredwith a single layer of 015 times 10minus6 thick UV stabilized poly-ethylene film and hinged at the top of the drying chamberIt allows the solar radiations to drying chamber and furtherenhances the drying rate by greenhouse effect The dryingchamber was coated with black paint thermally insulatedwith asbestos sheets to minimize the heat loss provided withthe support for sample holding mesh trays having area 1m2The general rule of thumb is that 1m2 of tray area is neededto layout 10 kg of produce The air is warmed up during itsflow through a low pressure drop thermosyphonic primarysolar collector The moisture is removed by natural convec-tion and greenhouse effect by secondary solar collector indrying chamberThemoist air is then discharged through theair vents provided at the top of the drying chamber Dryingstudies in solar cabinet dryer were conducted with tworeplicates Accurately weighted ginger slices (5 kg per batch)of initial moisture content 6215 db were evenly distributedon the sample holding mesh trays After predetermined time


T3

T2

Sliding door

Perforated trays

Drying chamber

Ginger slices


Solar radiations







119872initial =119882119908

minus119882119889

119882119889

times 100 (1)


119908




119889119872

119889119879=119872119900

minus119872119905

119905 (2)


119900

and119872119905






ln MR = ln ( 81205872

) minus1205872

119863eff119905

1198712

(3)


Slope =1205872

119863eff1198712

(4)


MR =119872119905

minus119872119890

119872119900

minus119872119890

(5)

where119872119905

119872119900

and119872119890


119905

and119872119900


MR =119872119905

119872119900

(6)




1205942

=

sum119873

119894=1


119873 minus 119899

(7)

RMSE = 1119873

[

[

sum119873

119894=1


119873

]

]

12

(8)

120576 () =10038161003816100381610038161003816100381610038161003816100381610038161003816



10038161003816100381610038161003816100381610038161003816100381610038161003816

(9)




119882119889

(10)

where 119882119903






)2

+ (Δ119886lowast

)2

+ (Δ119887lowast

)2 (11)

Δ119871lowast

= 119871lowast

minus 119871lowast

119900

Δ119886lowast

= 119886lowast

minus 119886lowast

119900

Δ119887lowast

= 119887lowast

minus 119887lowast

119900

(12)


119900

119886lowast119900



0

10

20

30

40

50

60

70

80

0 100 200 300 400 500 600Drying time (min)


Tem

pera

ture

(∘C)







0

100

200

300

400

500

600

0 100 200 300 400 500 600

Moi

sture

cont

ent (

d

b)

Drying time (min)


0

0005

001

0015

002

0025

003

0035

004


Dry

ing

rate

(kg

wat

erk

g dr

y m

ater

ialmiddotm

in)





0

0005

001

0015

002

0025

003

0035

004

0 100 200 300 400 500 600Drying time (min)

Dry

ing

rate

(kg

wat

erk

g dr

y m

ater

ialmiddotm

in)


0

05

0 100 200 300 400 500 600Drying time (min)

y = minus00049x + 03131

R2 = 09814

minus05

minus1

minus15

minus2

minus25

ln (M

R)








2 RMSE 1205942

120576 ()

1 Newton k = 00039 09269 1008 00106 114

2 Page k = 00074n = 1675 09823 00538 0003 178




0010203040506070809

1

0 100 200 300 400 500

Moi

sture

ratio

Drying time (min)



0010203040506070809

1

0 02 04 06 08 1

Pred

icte

d m

oistu

re ra

tio




4 Conclusion




References









































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










T3

T2

Sliding door

Perforated trays

Drying chamber

Ginger slices


Solar radiations







119872initial =119882119908

minus119882119889

119882119889

times 100 (1)


119908




119889119872

119889119879=119872119900

minus119872119905

119905 (2)


119900

and119872119905






ln MR = ln ( 81205872

) minus1205872

119863eff119905

1198712

(3)


Slope =1205872

119863eff1198712

(4)


MR =119872119905

minus119872119890

119872119900

minus119872119890

(5)

where119872119905

119872119900

and119872119890


119905

and119872119900


MR =119872119905

119872119900

(6)




1205942

=

sum119873

119894=1


119873 minus 119899

(7)

RMSE = 1119873

[

[

sum119873

119894=1


119873

]

]

12

(8)

120576 () =10038161003816100381610038161003816100381610038161003816100381610038161003816



10038161003816100381610038161003816100381610038161003816100381610038161003816

(9)




119882119889

(10)

where 119882119903






)2

+ (Δ119886lowast

)2

+ (Δ119887lowast

)2 (11)

Δ119871lowast

= 119871lowast

minus 119871lowast

119900

Δ119886lowast

= 119886lowast

minus 119886lowast

119900

Δ119887lowast

= 119887lowast

minus 119887lowast

119900

(12)


119900

119886lowast119900



0

10

20

30

40

50

60

70

80

0 100 200 300 400 500 600Drying time (min)


Tem

pera

ture

(∘C)







0

100

200

300

400

500

600

0 100 200 300 400 500 600

Moi

sture

cont

ent (

d

b)

Drying time (min)


0

0005

001

0015

002

0025

003

0035

004


Dry

ing

rate

(kg

wat

erk

g dr

y m

ater

ialmiddotm

in)





0

0005

001

0015

002

0025

003

0035

004

0 100 200 300 400 500 600Drying time (min)

Dry

ing

rate

(kg

wat

erk

g dr

y m

ater

ialmiddotm

in)


0

05

0 100 200 300 400 500 600Drying time (min)

y = minus00049x + 03131

R2 = 09814

minus05

minus1

minus15

minus2

minus25

ln (M

R)








2 RMSE 1205942

120576 ()

1 Newton k = 00039 09269 1008 00106 114

2 Page k = 00074n = 1675 09823 00538 0003 178




0010203040506070809

1

0 100 200 300 400 500

Moi

sture

ratio

Drying time (min)



0010203040506070809

1

0 02 04 06 08 1

Pred

icte

d m

oistu

re ra

tio




4 Conclusion




References









































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











1205942

=

sum119873

119894=1


119873 minus 119899

(7)

RMSE = 1119873

[

[

sum119873

119894=1


119873

]

]

12

(8)

120576 () =10038161003816100381610038161003816100381610038161003816100381610038161003816



10038161003816100381610038161003816100381610038161003816100381610038161003816

(9)




119882119889

(10)

where 119882119903






)2

+ (Δ119886lowast

)2

+ (Δ119887lowast

)2 (11)

Δ119871lowast

= 119871lowast

minus 119871lowast

119900

Δ119886lowast

= 119886lowast

minus 119886lowast

119900

Δ119887lowast

= 119887lowast

minus 119887lowast

119900

(12)


119900

119886lowast119900



0

10

20

30

40

50

60

70

80

0 100 200 300 400 500 600Drying time (min)


Tem

pera

ture

(∘C)







0

100

200

300

400

500

600

0 100 200 300 400 500 600

Moi

sture

cont

ent (

d

b)

Drying time (min)


0

0005

001

0015

002

0025

003

0035

004


Dry

ing

rate

(kg

wat

erk

g dr

y m

ater

ialmiddotm

in)





0

0005

001

0015

002

0025

003

0035

004

0 100 200 300 400 500 600Drying time (min)

Dry

ing

rate

(kg

wat

erk

g dr

y m

ater

ialmiddotm

in)


0

05

0 100 200 300 400 500 600Drying time (min)

y = minus00049x + 03131

R2 = 09814

minus05

minus1

minus15

minus2

minus25

ln (M

R)








2 RMSE 1205942

120576 ()

1 Newton k = 00039 09269 1008 00106 114

2 Page k = 00074n = 1675 09823 00538 0003 178




0010203040506070809

1

0 100 200 300 400 500

Moi

sture

ratio

Drying time (min)



0010203040506070809

1

0 02 04 06 08 1

Pred

icte

d m

oistu

re ra

tio




4 Conclusion




References









































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










0

100

200

300

400

500

600

0 100 200 300 400 500 600

Moi

sture

cont

ent (

d

b)

Drying time (min)


0

0005

001

0015

002

0025

003

0035

004


Dry

ing

rate

(kg

wat

erk

g dr

y m

ater

ialmiddotm

in)





0

0005

001

0015

002

0025

003

0035

004

0 100 200 300 400 500 600Drying time (min)

Dry

ing

rate

(kg

wat

erk

g dr

y m

ater

ialmiddotm

in)


0

05

0 100 200 300 400 500 600Drying time (min)

y = minus00049x + 03131

R2 = 09814

minus05

minus1

minus15

minus2

minus25

ln (M

R)








2 RMSE 1205942

120576 ()

1 Newton k = 00039 09269 1008 00106 114

2 Page k = 00074n = 1675 09823 00538 0003 178




0010203040506070809

1

0 100 200 300 400 500

Moi

sture

ratio

Drying time (min)



0010203040506070809

1

0 02 04 06 08 1

Pred

icte

d m

oistu

re ra

tio




4 Conclusion




References









































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation












2 RMSE 1205942

120576 ()

1 Newton k = 00039 09269 1008 00106 114

2 Page k = 00074n = 1675 09823 00538 0003 178




0010203040506070809

1

0 100 200 300 400 500

Moi

sture

ratio

Drying time (min)



0010203040506070809

1

0 02 04 06 08 1

Pred

icte

d m

oistu

re ra

tio




4 Conclusion




References









































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation














































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation









Documents

Research Article Investigation of Solar Drying of Ginger ...downloads.hindawi.com/journals/cje/2014/305823.pdf · Research Article Investigation of Solar Drying of Ginger ( Zingiber