STUD IES ON HEAT PUMP DRY ING OF THOMSON SEED LESS GRAPES (Vitis Vinifera) FOR THE PRO DUC TION OF RAI SINS

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1 Progressive Research An Inernaional Journal Prin ISSN : , Online ISSN : Volume (Special-V) : 7-77, (25) Sociey for Scienific Developmen in Agriculure and Technology Meeru (U.P.) INDIA STUD IES ON HEAT PUMP DRY ING OF THOMSON SEED LESS GRAPES (Viis Vinifera) FOR THE PRO DUC TION OF RAI SINS G. Kaveri and V. Thirupahi 2 Assisan Professor, Don Bosco College of Agriculure, (Affiliaed o Tamil Nadu Agriculural Universiy), Sagayahoam, Takkolam, Vellore Professor, Dryland Agriculural Research Saion, Tamil Nadu Agriculural Universiy, Cheinad. ABSTRACT Sudies were uced wih Thompson seedless grapes wih differen prereamens NaOH (.5%), Olive oil (2.5%) plus K2CO3 (6.%) and Ehyl oleae (2.%) plus K2CO3 (2.5%). Drying was carried ou under sun and also a 45, 55 and 65 C in cabine dryer and hea pump dryer. The iniial moisure conen of per (db) have been reduced o a final moisure conen of 5 percen (db). The ime aken for drying varies wih respec o differen reamen and drying emperaure. Drying a and 65 C ook 33 and 23 hours for Ehyl Oleae plus K2CO3 prereamen. The highes drying rae observed in hea pump dryer was. kg/kg min. a 65 C. The iniial drying rae was found o be higher in case of hea pump dryer followed by cabine dryer were found o be 35 per cen less han ha of he cabine dryer. The efficiency of he oraor and enser coils was found o be 68 and 6 per cen respecively. Moisure exracion rae (MER) and Specific moisure exracion rae (SMER) values were less in cabine dryer because of he increased drying ime. The coefficien of performance of he hea pump dryer a 45, 55 and 65 o C were.89, 4.3 and 6.58 respecively. The COP increased wih emperaure as lower he oraor emperaure, higher he hea released a he enser. From he saisical analysis, i was found ha he samples prereaed wih Ehyl Oleae (2.%) plus K2CO3 (2.5%) dried a 55 C in hea pump drier was bes in erms of low acidiy and high viamin C reenion. Grape is one of he frui crops mos widely grown in he world. Indian Grapes occupies fifh posiion amongs frui crops in he world wih a producion (2689 housand ons) from an area of 25 housand ha in he year The major varieies of grapes grown in India are Thompson Seedless, Sonaka, Anab-e-Shahi, Perlee, Banglore blue, Pusa seedless, Beauy seedless ec., Maharashra occupies he firs posiion wih a producion of.68 MT of grapes, followed by Karnaaka. The oher saes growing grapes are Punjab, Andhra Pradesh and Tamil Nadu. The preservaion of grapes (Viis vinifera) in he form of raisins is a major profi making business in differen counries where grapes are grown. In India, a rapid developmen on raisin producion has aken place as he producion of grapes has increased significanly from 22, onnes in o 5, onnes during (Kaariya e al., 27). During he year 26 he average producion of grapes was 65, onnes. ( Approximaely, 85 per cen of he oal producion, irrespecive of he variey is consumed as fresh. Abou 2, onnes of Thompson Seedless and is muans, namely, Sonaka, Tas-A-Ganeh and Manik Chaman are dried for raisins. The area of Thompson seedless grapes is around 22, ha and producion is 55, onnes in India.( Shikhamany. S. D. 23). To minimize he wasage (25-3 %), he surplus producion has o be processed and preserved properly. Food processing plays a vial role in increasing he shelf life of he producs besides considering he nuriional aspecs. Drying is one of he mos cos-effecive means of preservaion of agriculural and horiculural produce. The main purpose of drying is o reduce he moisure conen o such a level where spoilage due o various reacions is minimized. Various drying mehods are employed in India in which hea pump drying was ried for he producion of raisins from Thompson seedless grapes. Hea pump drying is an alernaive mehod for drying producs wih lower energy consumpion, less relaive humidiy and low emperaure. This can be achieved by ensing moisure from he drying air and followed by reheaing. Produc qualiy in erms of color and smell could be improved. (Prasersan and Saen-saby, 998). Hence, an aemp was made o find ou he suiabiliy of hea pump drying for geing good qualiy raisins. MATERIALS AND METHODS Preparaion of Grapes for Drying : Thompson seedless (Viis vinifera) variey of grapes was used for he producion of raisins. Fresh grapes were obained from he local frui marke a Coimbaore and Theni disrics of Tamil Nadu. The bunches were carefully chosen by removing he infeced or damaged pars. Afer careful soring, he grapes were washed horoughly in running waer and wiped wih a issue paper.

2 72 G. Kaveri e. a. Table- : Soaking emperaure and ime of prereamens for Thompson seedless grapes Sl. No. Prereamens Thomson seedless Temp. ( o C) Time (min.) i. Na OH (.5 %) sec ii. Olive oil (2.5 %) + K 2 CO 3 (6 %) 6 3 iii Ehyl Oleae (2 %) + K 2 CO 3 (2.5 %) 6 3 iv. Conrol (Unreaed) - - Table-2 : MER and SMER a differen emperaures in hea pump dryer. MER (g/h) SMER (g/kwh) Prereamens Drying emperaure ( o C) % NaOH %Olive oil+ 6 % K 2 CO %Ehyl oleae+2.5 % K 2 CO Conrol Table-3 : Waer aciviy (aw) of Thompson seedless raisins Prereamens Temperaure ( o C) Na OH (.5 %) Olive oil (2.5 %) + K 2 CO 3 (6 %) Ehyl Oleae (2 %) + K 2 CO 3 (2.5 %) Conrol (Unreaed) Fig.. Schemaic diagram of hea pump dryer Plae. Hea pump dryer wih Prereamens : Prereamen of he grapes prior o drying is inended o reduce he drying ime and also improve he qualiy of he dried produc. Also prereamens eliminae he adhered foreign paricles and remove he waxy layer and hus reduce resisance o he diffusion of waer hrough he grape skin. Thompson seedless grapes were is Componens subjeced o he following prereamens wih differen combinaion of soaking emperaure and ime given in he (Table-). The reaed sample was rinsed wih ap waer afer removal from he soluion. The surface moisure of

3 G. Kaveri e. al. 73 Drying rae (Kg/kg.min.) % NaOH Prereamen Avg. moisure conen (%db) Drying rae(kg/kg.min.) % Olive oil + 6% K 2 CO 3 Prereamen Avg. moisure Conen (%db) Drying rae (kg/kg.min.) 2%Ehyl oleae +2.5% K 2 CO 3 Pre reamen Avg. moisure conen (% db) Drying rae (kg/kg.min.) Conrol Avg.moisure conen (% db) 55 C 65 C Fig. 2. Drying rae curve for hea pump dried raisins wih differen prereamens a differen emperaures of Thompson seedless grapes % NaOH Prereamen C 65 C 2.5% Olive oil+6% K 2 CO 3 Prereamen C 65 C % Ehyl oleae +2.5%K2CO3 Prereamen 55 C 65 C Conrol C 65 C Fig.3. curve for hea pump dried raisins wih differen prereamens of Thompson seedless grapes

4 74 G. Kaveri e. a. he reaed sample was removed wih issue paper and spread over a 4 x 3 cm perforaed ray Drying in he Hea pump dryer Hea pump dryer : Hea pumps have been known o be energy efficien when used in conjuncion wih drying sysems. Any dryer ha uses convecion as he primary mode of hea inpu can be fied wih a suiably designed hea pump. Shelf or ray dryers or kilns are he mos commonly repored dryers used in conjuncion wih hea pumps. Drying chamber : The drying chamber of size 72 x 8 x 92 cm was made of mild seel shee of 3mm hickness. The drying chamber could accommodae 3 rays of size 4 x 3 x 2 cm. The oule opening of he hea pump is conneced o he drying chamber by a duc of size 43 x 5 cm made of mild seel and insulaed ouside wih asbesos rope. Aluminum rays wih 2 mm diameer perforaions were used for drying. The emperaure and relaive humidiy inside he chamber was measured using he emperaure/relaive humidiy meer. Working of he hea pump dryer : One way of reducing he energy loss of open-circui drying chambers is o use a closed circui sysem incorporaing a hea pump. In a hea pump waer is ensed from he moisened air and he laen hea released is ransferred o he resuling dehumidified air which is recirculaed (Fig.). Air recirculaion enables he use of higher air speeds, lower air emperaures han open-circui chambers wihou large increase in energy coss. I can hus reduce he risk of irreversibly damaging he dried produc hrough physical aleraion or chemical reacions boh of which are favored by higher emperaures. I also faciliaes conrol of emperaure of he drying air (Vazquez, 997). The working fluid (refrigeran) a low pressure is vaporized in he oraor by hea drawn from he dryer exhaus air. The compressor raises he enhalpy of he working fluid of he hea pump and discharged i as superheaed vapor a high pressure. Hea is removed from he working fluid and reurned o he process air a he enser. The working fluid is hen hroled o he low-pressure line (using an expansion valve) and eners he oraor o complee he cycle (Plae.). In he dryer sysem, ho and dry air a he exi of he enser is allowed o pass hrough he drying chamber, where i gains laen hea from he maerial. This humid air from he dryer passes hrough he cooling coil mainained below dew poin emperaure, where ensaion of moisure occurs and he air ges dehumidified. Drying rae : The drying rae of he produc dried under sun, cabine and hea pump drier was calculaed using he following equaion (Chakravery, 988) Amoun of moisure removed R Time aken (Toal bone dry weigh of sample in g / )...() Moisure Raio : The moisure raio was calculaed as: where, MR M Me M Me MR = moisure raio M M = = moisure conen a any ime, (% db) iniial moisure conen, (% db) M e = equilibrium moisure conen, (% db) Bye pass facor :...(2) The bye pass facor provides an indirec measure of he efficiency of hea ransfer a he coil. Bye pass facor of he apparaus represens he fracion of unconaced air. The fracion of air by passed hrough he oraor (b ) and enser coils (b ) can be deermined from he following equaion. where, b b (3)...(4) ( b )...(5) ( b )...(6) and 2 = emperaure of air enering and leaving oraor coils, C 3 and 4 = emperaure of air enering and leaving enser coils, C and = emperaure of oraor and enser coils, C and = efficiency of oraor and enser coils, per cen Moisure exracion rae MER = Amoun of waer removed, kg Time, h...(7) Specific Moisure Exracion Rae : For drying, a more appropriae efficiency parameer is he specific moisure exracion rae (SMER) defined as Amoun of waer oraed, kg SMER Energy used, kwh...(8) Coefficien of performance : The dryer efficiency is a measure of he quaniy of energy used in removing a uni mass of waer from a produc. The efficiency of hea pump

5 G. Kaveri e. al. 75 can be expressed in erms of coefficien of performance which is defined as he raio of hea recovered a he enser o he work required by he compressor. useful hea oupu, kw COP...(9) power inpu, kw Waer aciviy : The concep of waer aciviy is imporan in deermining produc safey and qualiy mainenance in a paricular sorage environmen. An auomaed insrumen (M/s Aqua lab, USA) model XT-2i, was used o deermine he waer aciviy of grapes. Waer aciviy was measured by placing he sample in a conainer which is placed in a sealed chamber and hen he knob is closed o read he waer aciviy of he sample. The waer aciviy of he grapes and raisins were recorded wih respec o amospheric emperaure. Colour : Colour flex meer (Huner Associaes Laboraory, Inc., model : 65/ ) was used for he measuremen of colour of he grapes and raisins. I works on he principle of collecing and measuring he energy from he samples refleced across he enire visible specrum. The Huner lab s colour flex specro colorimeer is a versaile, compac colour measuring insrumen consising of measuremen (sample) por, opaque cover and display uni. 'L' Values Ascorbic acid : Ascorbic acid oherwise known as viamin C is one of he imporan componens, which deermines he qualiy of he produc. Generally, i is presen in larger quaniy in fresh fruis and vegeables. The ascorbic acid conen in he grapes was deermined by he dye mehod adoped by Ranganna (986). Quaniy of ascorbic acid (mg) presen in g of he sample was calculaed as follows: Ascorbic acid (mg/g) =.5 mg V2 ml...() V 5ml w. of sample Hea Pump dryer -Thompson P P2 P3 P4 Treamens Fig.-4 : Colour value for hea pump dried raisins wih differen reamens dried a differen emperaures RESULTS AND DISCUSSION The average weigh, radius and lengh for Thompson seedless grapes was observed as 2.25 g,.95 and.5 cm respecively. The composiion of fresh grapes was analyzed before drying and he resuls viz., iniial moisure conen of Thompson seedless grapes was 75-8 (% wb), he oal soluble solids conen for Thompson seedless grapes was 2.7ºBrix, he waer aciviy for Thompson seedless grapes was.93 and he viamin C level was.5 mg/g for he Thompson seedless grapes. Effec of prereamens and drying emperaure on drying ime Drying of Grapes in Hea Pump Dryer : Thompson seedless grapes subjeced o various prereamen was dried a emperaures of 45, 55 and 65 o C in hea pump dryer. The ambien emperaure and relaive humidiy were recorded as 35ºC and 7 per cen respecively. I was observed ha he hea pump dryer showed a reducion of per cen relaive humidiy, when compared wih cabine dryer. The reducion in relaive humidiy was due o he dehumidificaion and heaing of air in hea pump dryer. Drying characerisics of grapes in hea pump dryer : Drying of Thompson seedless grapes was carried ou a 45, 55 and 65 o C air emperaure in hea pump dryer. The drying rae vs average moisure conen curves for Thompson seedless grapes dried in hea pump drier are presened in Fig.2 & 3. Effec of prereamens and drying emperaure on drying ime : Thompson seedless grapes prereaed wih ehyl oleae (2%) plus poassium carbonae (2.5%) ook 33, 27 and 2 hours for drying from is iniial moisure conen of o he final moisure conen of around 5 per cen dry basis a 45, 55 and 65 o C. I was repored ha grapes dried in a bach drier ook 2.5 hours o dry from iniial moisure conen of per cen dry basis o final moisure conen 2 per cen dry basis a 6 o C (Doymaz and Pala, 22). The prereamen which ook maximum ime was olive oil (2.5%) plus K 2 CO 3 (6%) followed by NaOH (.5%) for boh he varieies. Drying ime aken for unreaed grapes (conrol) was maximum up o 5 hours for boh varieies in his dryer. Effec of prereamens and emperaures on drying rae : The maximum drying rae for Thompson seedless grapes variey was observed when prereaed wih Ehyl oleae (2.%) plus K 2 CO 3 (2.5%). The drying rae was observed as.799,.44 and.39 kg/kg min. a emperaures 45, 55 and 65 o C respecively. Similar resuls were repored by Doymaz (26). The drying rae was more a higher drying emperaures because more moisure was los in less ime and in due course, he free moisure available in grapes was less and hence he drying rae sared o decrease. From he beginning he consan rae period was absen and he drying ook place under he falling

6 76 G. Kaveri e. a. rae. These resuls are in agreemen wih he observaion for Sulana seedless grapes by Pahlavanzadeh e al., (2). Effec of emperaure on moisure raio : The moisure raio of grapes reduced exponenially as he drying ime increased. Reducion of moisure raio from o around.6 for Thompson seedless grapes occurred a 45, 55 and 65 o C drying emperaures. The moisure raio of grapes reduced as he drying ime increased. The moisure raio of grapes reduced coninuously wih drying ime and no consan rae period exiss in he hea pump dryer. Effec of drying mehods on energy requiremens for drying : The energy requiremens for drying of grapes in hea pump dryer was calculaed. The compressor power of he hea pump dryer was found o be 2TR (7.334 kw) and he oal hea load in he cabine dryer was aken as 9.37 kw. The energy requiremen for drying of grapes in hea pump dryer was found o be 35 per cen less han he cabine dryer. The reducion in energy in he HPD was achieved by re-circulaing he air coming ou of he dryer exhaus. Bye Pass Air Raio and Efficiency of Cooling and Heaing Coils : The bye pass facor of he hea exchanger represened he fracion of unconaced air wih cooling and heaing coil. The bye pass air raio for he oraor (cooling coil) and enser (heaing coil) were observed, when he ambien emperaure and relaive humidiy were 35 C and 7 per cen. The bye pass air raios a he oraor and enser coils were found o be.32 and.4 respecively. Using he bye pass air raio, he efficiencies of he cooling and heaing coils were found o be 68 and 6 per cen respecively. Recirculaion sysem was considered o be bes han open sysem as he bye pass air released from drier recovers energy a he oraor. Coefficien of performance : The efficiency of he hea pump dryer can be expressed in erms of coefficien of performance. The coefficien of performance of hea pump dryer increased wih increase in emperaure and was calculaed using he psychromeric char. The power required by he compressor was aken o be 2TR. The coefficien of performance a 45, 55 and 65ºC were.89, 4.3, and 6.58 respecively. The COP increased wih emperaure, because lowers he oraor emperaure, higher he hea released a he enser. Moisure Exracion Rae (MER) and Specific Moisure Exracion Rae (SMER) of Hea Pump Dryer for Thompson seedless Grapes : The main parameers used o evaluae he Hea Pump Dryer performance are he MER and SMER. The MER (kg waer/h) indirecly indicaes he dry produc hroughou rae. Moisure removal from he produc was driven by he emperaure induced driving force and hus he MER increased wih he emperaure. Table-2 shows he MER a differen emperaures in cabine dryer and hea pump dryer respecively. The MER values were less in cabine dryer when compared o he hea pump dryer, because of he increased drying ime in cabine dryer. SMER reflecs he energy efficiency in he drying process in erms of kilogram of waer removed from he produc per uni energy (kg waer/kwh). Table.2. shows he SMER a differen emperaures in cabine and hea pump dryers, where he compressor capaciy in hea pump dryer was given as 2 TR (i.e., kw) and he oal load in he cabine dryer was given as 9.37 kw. I shows ha he SMER value declined wih ime. This was due o he fac ha as he drying proceeded, he moisure removal rae decreased. As expeced, he SMER values were direcly proporional o he weigh of he produc being dried. Effec of Prereamen and Drying Temperaure on Qualiy of Raisins Effec of prereamen and drying emperaure on viamin C : During drying, he emperaure was increased o supply energy necessary o ransform waer o vapor phase. This acceleraed reacions beween differen consiuens in he food suff. In case of Viamin C, here was degradaion in he dried produc when compared wih he fresh. From he able i was observed ha he sample dried a 45ºC showed higher viamin reenion (.28 mg/g), where as he sample dried a 65ºC showed less viamins C conen (.9 mg/g) in hea pump drying. From he saisical analysis i was found ha here was no significan effec of prereamen on viamin C conen for Thompson seedless variey dried in hea pump drier. Viamin C decreased wih increase in drying emperaure (above 6 C) of hea pump drying. This may be due o degradaion of viamin C a elevaed emperaure. Effec of prereamen and drying emperaure on waer aciviy (a w ) of raisins : The waer aciviy of he samples dried in hea pump dryer is presened in Table-3. The iniial waer aciviy of Thompson seedless grapes was.93. The final waer aciviy for raisins was in he range of for he Thompson seedless variey. These resuls correlaed wih he Pahlavanzadeh e al. (2) sudies deerminaion of parameers and prereamen soluion for Iranian seedless grapes drying. Effec of prereamen and drying emperaure on colour of raisins : The color of raisins was deermined using Huner color lab. The prereamens given o he grapes had a significan effec on he color of he dried produc. The lighness values L for differen prereaed samples dried a differen emperaures in hea pump drier. The iniial color value L of he fresh grapes is for Thompson (Fig.-4).

7 G. Kaveri e. al. 77 L value was more for he Ehyl oleae (2.%) plus K 2 CO 3 (2.5%) reaed sample followed by Olive oil (2.5%) plus K 2 CO 3 (6%), NaOH (.5%) reaed and conrol sample a all emperaures for Thompson seedless grapes. The Ehyl oleae plus K 2 CO 3 helped in reducing he enzymaic browning during drying of grapes hereby here is an increase in colour value compared o oher prereamens. This resul agreed wih he Mahmuoglu e al., (996) ha he color value increased for ehyl oleae reamen compare wih oher prereamens as alkaline soluions gives ligher produc, since he browning rae decreased, due o he reducion in drying imes. There is no significan effec of emperaures on colour value. CONCLUSION A reducion of per cen relaive humidiy was observed in hea pump dryer. The iniial moisure conen o he finial moisure conen of he Thompson seedless grapes was dried from o 5 of per cen dry basis a all differen emperaure 45, 55 and 65 C. The drying rae was high when he emperaure was high in he hea pump dryer The energy requiremen in hea pump dryer was found o be 35 per cen less han ha of he oher ypes of dryer (cabine dryer). The efficiency of he oraor and enser coil was found o be 68 and6 per cen respecively. The Moisure Exracion Rae and Specific Moisure Exracion Rae decreased wih drying ime. The coefficien of performance a he drying emperaures of 45, 55 and 65 C were.89, 4.3 and respecively. The COP increases wih emperaure, because lower he oraor emperaure, higher he hea released a he enser. Toal soluble solids and colour values were found o increase wih emperaure in hea pump dryer. Viamin C conen increased wih increase in drying emperaure from 45 o 55 C bu more han his emperaure decreased he Viamin C conen in he Thompson seedless grapes dried in hea pump dryer. REFERENCES. Adapa,P.K., Schoenau. G.J and Sokhansanj. S.(22). Performance sudy of a hea pump dyer sysem for specialy crops Par : Developmen of a simulaion model. Inernaional Journal of Energy Research. 26(): Adapa,P.K and Schoenau. G.J. (25). Re-circulaing hea pump assised coninuous bed drying and energy analysis. Inernaional Journal of Energy Research. 29: Chakravery.A.(988). Pos Harves Technology of Cereals, Pulses and Oilseeds. 2 nd Ediion, Oxford and Publishing Co. PVT. LTD, New Delhi. 4. Doymaz, I and Pala. M. (22). The effecs of drying pre reamens on air-drying raes of he seedless grapes. Journal of Food Engineering. 52 : Doymaz.I. (24). Drying kineics of whie mulberry. Journal of Food Engineering. 6: Doymaz, I. (26). Drying kineics of black grapes reaed wih differen soluions. Journal of Food Engineering. 76 : Kaariya, S.S, Shaikh. E. I. and Chopade. J.J. ( 27). Grape dryer. Food Pack.Com Kanhakumari, N and Uma Maheswari. K. (26). Physico-chemical and sensory qualiy of raisins prepared from wo varieies of grapes by differen drying mehods. Journal of Food Science Technology. 43 (2) : Lewicki, P. P and Wolf. W. (995). Rheological Properies of Raisins: Par II. Effec of Waer Aciviy. Journal of Food Engineering. 26 : Mahmuoglu, T., F. Emir and Y. Biro Saygi.996. Sun/Solar Drying of Differenly reaed Grapes and Sorage Sabiliy of Dried Grapes. Journal of Food Engineering. 29 : Ozilgen. M, Sumnu. G. Emir. H. and Emir. F. (997). Qualiy conrol chars for sorage of raisins and dried figs. Z.Lebensm Uners Forsch A, 24 : Prasersan, S and Saen-saby. P. (998). Hea pump drying of agriculural maerials. Drying Technology. 6(&2) : Pahlavanzadeh, H., Basiri. A. and Zarrabi. M. (2). Deerminaion of parameers and prereamen soluion for grape drying. Drying Technology. 9 () : Pangavhane, D.R., Sawhney. R.L. and Sarsavadia. P.N. (999). Effec of various diing prereamen on drying kineics of Thompson seedless grapes. Journal of Food Engineering. 39 : Pangavhane, D.R., Sawhney. R.L. and Sarsavadia. P.N (2). Drying kineic sudies on single layer Thompson Seedless grapes under conrolled heaed air Condiions. Journal of Food Processing and Preservaion. 24 : Queiroz,R., Gabas. A.L. and Telis. V.R.N. (24). Drying kineics of omao by using elecric resisance and hea pump dryers. Drying Technology. 22(7) : Ranganna, S. (986). Handbook of Analysis and Qualiy Conrol for Frui and Vegeable producs. (2 nd Ediion), Taa McGraw-Hill Publishing Company Limied, New Delhi. 8. Shikhamany.S.D. (23). Grape producion in India, 6.hm. 9/ Vazquez., F. Chenlo, R. Moreira and Cruz. E. (997). Grape drying in a pilo plan wih a hea pump. Drying Technology. 5(3&4) :