Development of a Compact Vacuum Freeze Drying for Jelly Fish (Schypomedusae)

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1 Jurnal Teknologi Full paper Developent of a Copact Vacuu Freeze Drying for Jelly Fish (Schypoedusae). Idrus Alhaid *,. Yulianto, Nasruddin, Engkos A. Kosasih a Refrigeration and Air-Conditioning Laboratory, echanical Engineering Departent - Faculty of Engineering - University of Indonesia, Kapus UI Depok, 1644, Indonesia *Corresponding author: aak@eng.ui.ac.id Article history Received :15 June 01 Received in revised for :1 August 01 Accepted :8 August 01 Graphical abstract Abstract A new design of a vacuu freeze drying with internal cooling and heater fro condenser s heat loss was built and tested. The dryer was used to dry jelly fish (scyphoedusae) to study the effect of drying paraeter such as teperature within the drying chaber on ass losses (evaporation) during freezing stage and oisture ratio at the end of drying process and also the drying rate of vacuu drying process. The cold trap teperature rise in when activated the heating fro condenser s heat loss. The idili thin layer atheatical drying odel was used to estiate and predict the oisture ratio curve base on different drying chaber teperature. The result of this experient show that ass loss during freezing stage decreased with a decrease in drying chaber teperature with constant pressure. Drying tie reduced with an increase in drying teperature. Drying chaber teperature decreasing has a result pressure saturation of aterial lower than drying chaber pressure have an effect ass transfer should not occurs. Keywords: Vacuu freeze drying, ass losses, oisture ratio, jellyfish (Scyphoedusae), thin layer odels, internal cooling, condenser s heat loss 01 Penerbit UT Press. All rights reserved. 1.0 INTRODUCTION Vacuu Freeze drying (VFD) is an optial drying technology ethod because it aintains the structure, nutrients, and color of the original substance [1,, and 3]. Vacuu freeze drying has also been described as a ethod of drying that achieves a high drying rate because the boiling point of water in the product, held under the vacuu, is lower than atospheric pressure and water vapor is reoved by a vacuu pup [4]. Characteristic of this drying technique such as high drying rate, low drying teperature and oxygen deficient drying environent ay help to aintain the qualities such as shape, color, aroa and flavor and nutritive value of the dried product [5]. The developent of vacuu freeze drying there are two serious probles, aintain the quality of product and then reduce the energy use for the vacuu freeze drying operation. Vacuu freeze drying process consists of three processes that are freezing process, priary drying and secondary drying [6]. In freezing process, actually use vacuu freezing ethod. It is a freezing process based on the rapid evaporation of oisture fro the surface and within the products due to the low surrounding pressure below triple point (pressure below 6.1bar). Teperatures of product begin to decrease when the water starts to evaporate which is latent heat of evaporation reove sensible heat of product due to pressure reducing [7]. Vacuu freezing caused high evaporation and ass loss, this phenoenon for any product ake a serious daage [8]. any experients have been investigated by any researchers to reduce ass loss during vacuu freezing. The innovation in vacuu freeze drying to reduce ass loss and product daage by cobine between vacuu freezing with air blast freezing and iersion freezing [8, 9, 10]. The next process of vacuu freeze drying is priary drying. Priary drying is a process of ass transfer or change phase of product fro ice (solid) directly at low pressure below triple point condition. In this process need a lot of energy to sublie and reove unbound water in the product. any experients have been investigated by any researches to reduce energy consuption and drying tie of product. In general, prolonged drying tie can be reduced by techniques such as increasing teperature or decreasing pressure in the chaber. An experient with VFD using a icrowave heat source was developed for drying potato slices [11], and the total drying tie was reduced by 37% as a result of icrowave freeze drying and not conventional freeze drying. Results of another experient using icrowave freeze drying for drying sea cucubers indicated that the technique can effectively replace conventional freeze drying because it greatly reduces drying tie and energy consuption while producing the sae product quality. In order to avoid corona discharge during icrowave freeze drying, the cavity pressure should be applied within the range of Pa [1, 13]. An experient using an electrical heat source in the top position of a freeze vacuu dryer was conducted for drying 58 (01) eissn ISSN

2 6 Idrus et al. / Jurnal Teknologi (Sciences & Engineering) 58 (01) Suppl, 5 3 foodstuff; the surface teperature of the saple initially increased quickly due to the higher initial teperature difference between the saple surface and electrical heater, resulting in an increase in the drying rate and a reduction in drying tie []. Other experients using electrical heat sources have been perfored to copare differences attributable to placeent of Aloe Vera in either top or botto positions, resulting in a faster drying rate at the botto position [14]. This phenoenon occurred because the theral conductivity of ice or a frozen layer, if using a botto position heater, is 45 ties higher than the theral conductivity of a dry layer if using a top position heater. An innovative experient using infrared radiation as a heat source when drying peaches was copared to icrowave freeze drying, and results showed that less energy was consued using infrared radiation [15]. Recently, chili peppers were freeze dried using a heat pup inside a product container and a dehuidifier and blower to reduce huidity at the drying chaber, resulting in reduced drying tie accoplished fro either reducing drying pressure or fro increasing drying teperature. The oisture content of 0 kg of fresh chilies was reduced fro 34% to 15% when dried for 7 h [16]. Due to the probles above, the ai of this research is to investigate the characteristics of vacuu freeze drying of jelly fish (scyphoedusae) and the effect cobination internal cooling on ass loss and condenser s heat loss on final oisture ratio, drying rate and also the influence on the cold trap teperature. trap chaber with a diaeter and a length of 0 c. Cold trap is a cascade refrigeration with refrigerant at High stage R and at low stage HCR. Cold coil installed at drying and cold trap chaber. Heat fro condenser s heat loss also installed at drying chaber with sae coil. To shut on and shut off cold and heat coil using shut off valve. A pressure transitter PTX 1400 with an accuracy of 0.4% and easure range bar was used to easure pressure in the drying chaber. A tray of aterial used fro Teflon and insulated to keep the heat transfer during process. The teperature at drying chaber, cold trap, aterial and also cascade refrigeration syste were onitored by therocouple type K with accuracy 0.4%. Dial pressure used to onitor pressure in cascade refrigeration syste. The therocouple and pressure transitter connected to Data Acquisition which is have nuber of slot 4, total power 15 w and operating teperature - 0 o C until 55 o C..0 ATERIALS AND ETHOD.1 Saple Preparation Jelly fish (scyphoedusae) a sea anial coonly grown in Indonesia as aritie country were used as the test aterial in this research. The tentacles of jelly fish used as basic edical ingredient to reduce the growth cell of cancer. Due to that use need extraction by vacuu freeze drying to retain nutrition content, color, taste, and biological structure. Initial oisture contents of jelly fish is 95.91% (w.b), respectively. Before tested using vacuu freeze drying, jelly fish is first stirred as seen in Figure 1. Initial and final ass easured using digital balance with range g and accuracy of 0.4%. For each experient, 50 g of saples was used on vacuu freeze drying process Figure Copact vacuu freeze drying. Experiental Set-up Figure 1 Stirred of jelly fish tentacle A copact vacuu freeze drying with internal cooling and heat fro condenser heat loss was designed, built and installed at Departent of echanical Engineering, University of Indonesia (Fig and 3). It consist of Insulated cylindrical, drying and cold Figure 3 A Scheatic diagra of copact vacuu freeze drying. Blue line is cold refrigerant and red line is hot refrigerant. At High stage: (1) Copressor, () condenser, (3) needle valve as expansion valve, (4) PHE as evaporator. At low stage: (5) Copressor, (6) condenser, (7) Check Valve, (8) PHE as condenser, (9) Needle valve as expansion valve, (10) Cold/hot coil, (11) Cold trap coil, (1) Drying chaber, (13) Cold trap chaber, (14) Tray of aterial, (15-1) Shut off valve. easureent equipent: (-6) dial pressure gauge, (7) pressure transitter, (8-40) Therocouple type K, (41) Vacuu Pup

3 7 Idrus et al. / Jurnal Teknologi (Sciences & Engineering) 58 (01) Suppl, ethods To start the process, the cascade refrigeration syste in high stage was turned on until the Plate Heat Exchanger (PHE) as evaporator reached a teperature of -35 o C. And then the low stage was turned on until cold trap reached a teperature of -35 o C. For the using of internal cooling for freezing stage and condenser s heat loss as heater for drying stage, the shut off valve varied into position (Partially and Fully). The vacuu pup was then turned on until the substance reached a freezing teperature and appeared stable. The variants of experient show at Table 1. Table 1 Experient variation Experient Freezing Stage Drying Stage Internal Cooling Condenser s Heat loss Internal Cooling Condenser s Heat loss Valve Run no. 1 Off Off Off Off Run no. Fully Off Off Fully Open Open Run no. 3 Partially Off Off Partially Open Open Run no. 4 Off Fully Open Off Fully Open Run no. 5 Fully Open Off Fully Open Off.3.1 Characteristics of Vacuu Freeze Drying Teperature Characteristics of vacuu freeze drying on jelly fish based on the reading of therocouple type K for easure teperature which is installed at product. Teperature should describe three areas that are freezing, priary and secondary drying. The phenoena of change phase will be describes in Pressure and teperature graphic to know aount of water evaporate at freezing stage..3. ass Loss During Freezing Stage In this section, a siple theoretical analysis of vacuu freezing process based on therodynaic principle is presented. This analysis is liited to the ass loss based on teperature drop observed during vacuu freezing process. The heat required to lower the teperature of 1 kg jelly fish could be calculated by the following expression: t R (3) in Where R is the oisture ratio, in is the initial saple ass (kg), and t is the saple ass at tie t (kg) Curve of oisture ratio was describe using idilli thin layer odels as below [18] : n R a.exp k t bt (4) Where a, b is epirical constants in drying odels, k is epirical coefficients in the drying odels (h -1 ), n is drying exponent and t is tie (h). The epirical constants ( a, b), epirical coefficients (k) and also drying exponent (n) have been described with variant of teperature by calculation below [16]: k P x (5) a P P P (6) n P P P (7) b P P 971 x10 P x Drying Rate 3 3 Drying rate is one of iportant paraeter to know energy consue of vacuu freeze drying. The higher drying rate will reduce drying tie and finally reduce energy consue of vacuu freeze drying process. The equation to calculate drying tie described as below [1, ] with the schea at Figure 4 : (8). h C.. T (1) fg avg Where is ass loss (kg), hfg is latent heat evaporation (J/kg), is ass of jelly fish (kg), T is = the change in product teperature (K). Average specific heat (C avg ) of product can be calculated by following expression [7]: C 3349a J / kg. K avg () Where a is the water content of jelly For instance, water content of jelly fish is 95.91% by ass..3.3 oisture Ratio oisture ratio or rehydration ratio was siplified to t in instead of t e in e because relative huidity of the drying air continuously fluctuated in vacuu freeze drying process [17]. The oisture ratio is of the saple was then calculating by [11, 16]: Figure 4 Schee of heat and ass transfer in vacuu freeze drying N w Substitution. L. V w s x x t t t t (9) N. (10) s w w. L dx (11) V dt

4 8 Idrus et al. / Jurnal Teknologi (Sciences & Engineering) 58 (01) Suppl, 5 3. L. X. o s dx dt (1) And the heat flux that occurs to the aterial can be calculate based on conduction heat transfer since the condition at drying chaber is low vacuu below (Chakraborthy et al. 006) Substitution q Td T L L (13) L 1 x L (14) q Td T xl 3.0 RESULTS AND DISCUSSION 3.1 Characteristics of Vacuu Freeze Drying Teperature (15) The characteristics of vacuu freeze drying teperature of jelly fish under different drying chaber teperature are given in fig 5 and 6, respectively. As expected, fro Figure 5 can be seen that drying teperature consists of 3 area, freezing area, priary drying area and secondary drying area. As expected, fro Figure 6 drying tie decrease with an increase drying chaber teperature siilar tendency is also observed in study of Apichart and Sonuk (010) in vacuu drying of shiitake ushroo and jinda chilli and George and Data (00) in vacuu drying of vegetable slices. Characteristics for adding cobination internal cooling and condenser s heat loss the drying tie longer than without internal cooling due to freezing process reach lower teperature. 3. ass Loss During Freezing Stage Fro Figure 7-11 can be seen that vacuu pressure in the drying chaber decreased rapidly fro atosphere to below triple point pressure, then decline slightly. When it reaches to set pressure it starts to fluctuate around it. When the pressure is lower or equal to the saturation pressure at local teperature, water evaporates (change phase fro liquid to gas). After that the cooling effect coes fro water evaporating fro the saple and saple becoe freezing start fro the surface. However, with decreasing the pressure, evaporation and freezing occur through the jelly fish and teperature decrease together. There are different teperatures decreasing of jelly fish due to different teperature drying chaber. For Run no. 1 teperature of jelly fish should decrease fro 4 o C to -5 o C, Run no. 3 fro 4 o C to -3 o C, Run no. 4 fro 4 o C to -.5 o C and Run no. 5 fro 4 o C to -0 o C. But for Run no. there is inforation that the vacuu freeze drying process occurs with pre freezing by internal cooling. This event does not involve the evaporation process due to different pressure between saturation pressure product and drying chaber pressure to reduce product teperature. The next process is drying or subliation process which is change phase fro ice to gas. For Run no. 4 there is al function of vacuu freeze drying, the phase change at drying process occurs fro liquid to gas (evaporation) due to the teperature of condenser s heat loss in activated. Fro Figure 1 there is inforation for Run no. 5 which is does not occurs subliation or ass transfer so that the aterial not to dry. This event occurs due to drying chaber pressure higher than saturation pressure of aterial. When internal cooling activated until the on of drying stage Figure 7 Diagra P-T on run no. 1 Figure 5 Characteristic of aterial teperature consist of 3 area Figure 8 Diagra P-T on run no. Figure 6 Profile teperature versus drying tie of aterial

5 9 Idrus et al. / Jurnal Teknologi (Sciences & Engineering) 58 (01) Suppl, 5 3 cooling does not take high effect to the experient due to between internal cooling and vacuu freezing run concurrently. Should be note that to reduce ass loss due to evaporation, teperature of drying roo should be reduce first and then running vacuu pup. It is will give high effect to the process. Table ass losses for every experient run no. Figure 9 Diagra P-T on run no. 3 Experient Initial ass ass Loss Percentages (%) (g) (g) Run no Run no Run no Run no Run no oisture Ratio Figure 10 Diagra P-T on run no. 4 The oisture ratio curves of jelly fish under different drying teperature are given in Figure 13. As expected, oisture ratio reached axiu value at the beginning of the drying process due to a high oisture content in the substance during the first subliation. After reaching EC (Equalibriu oisture Content), its oisture content reained in bound water condition; therefore, the oisture ratio decreased. In other words, the oisture ratio decreased with drying tie in all drying processes. We observed that the processes which affect the oisture ratio internally are porosity and bulk density. Figure 11 Diagra P-T on run no. 5 Figure 13 oisture Ratio of Jelly Fish Figure 1 Grapich between saturation pressure of product with drying chaber pressure ass loss occurs during vacuu freezing since cooling effect directly coes fro water evaporation fro jelly fish and cobination internal cooling. ass losses of jelly fish with Run no.5 is given in table. The highest ass loss coes fro Run no. 1, due to the process without internal cooling. An internal In this research is using idili odel to know the oisture ratio. idili odel is one of odel for predicting the oisture ratio at a product, The predicting of this odel is in a thin layer. Thin layer drying generally eans to dry as one layer saple particles or slices. Because of its thin structure, the teperature distribution can be easily assued as unifor and thin layer drying is very suitable for luped paraeter odels. The advantages of using idili odel is suitable for drying kinetics which is the condition of the product and the surrounding environent change over tie. The correlation between idilli thin layer odel with Constanta (k, a, b, n) fro Artnaseaw and experient, 010 can be seen at table 3 and Figure 14. The data fro experient copare with idilli odel have differences with the value of R Square and not linear. The error (not linear) occurs due to the Constanta (k, a, b, n) use fro aterial which is have oisture content 80%, jelly fish have oisture content 95.91%. However, the idilli odel was validate to estiate the oisture ratio but need to redefine the Constanta (k, a, b, n) especially for jelly fish used. For run no 5 the oisture ratio cannot be calculate due to in

6 Drying Rate (g/. s) 30 Idrus et al. / Jurnal Teknologi (Sciences & Engineering) 58 (01) Suppl, 5 3 run no. 5 ass transfer not occurs. This phenoena because of saturation pressure of product lower than drying chaber pressure. The reduction of ass at final ass run no. 5 due to evaporation on product at the freezing process Table 3 Data coparison of oisture content between idilli odel and experient Experient Initial ass Final ass oisture Ratio (g) (g) Experient idilli odel Run no Run no Run no Run no Run no No ass transfer at subliation process (Reduction because of evaporation at freezing stage) No ass transfer at subliation process (Reduction because of evaporation at freezing stage) Heating Teperature ( o C) Figure 15 Drying Rate result until the end of vacuu drying process 3.5 Cold Trap Teperature 3.4 Drying Rate Figure 14 Graphic of linear correlation At Figure 16 is profile of cold trap teperature. At the beginning process, there is a fluctuate of teperature because of flashing point of product o reach freezing teperature. Activated heating fro condenser s heat loss ake the teperature of cold trap rise in, this phenoena because of activated heating fro condenser s heat loss is ean adding the cooling load of refrigeration syste. The cold trap teperature also rise in at priary and secondary drying due to load fro oisture content of aterial which is in this experient is 97% of water at aterial Heating have affect to the drying tie and because the using of heating can increase drying rate during vacuu freeze drying as seen at Figure 15. Drying rate of vacuu drying process without heating can reach drying rate until g/ s but with activated heating fro condenser s heat loss 44 o C drying rate reach g/ s. Every raise in heating teperature also can increase the drying rate of vacuu drying process siilar effect were describe by the others research with different heating source electrical heater [1,, 19) infrared heater [0, 1], but if using icrowave every rise in power of icrowave caused increase in drying rate of vacuu freeze drying [1, 13, 15] Figure 16 Profile of cold trap teperature 3.6 Final Product of Tentacle Jelly Fish At Figure 17 can be seen the final product after vacuu freeze drying process with variation fro run no 1 until 5. For variation run no until 4 can be seen that tentacle of jelly fish is dried with variant of final oisture content but for variation run no 5 the tentacle of jelly fish can t be dried but still in liquid condition because the pressure at drying chaber is higher than saturation product of jelly fish.

7 31 Idrus et al. / Jurnal Teknologi (Sciences & Engineering) 58 (01) Suppl, 5 3 N = olar Subliation rate kg. ol L = Thickness of saple () V = Specific volue of water in food 3 H kg s O = olecular ass kg kg. ol X = Fraction of initial oisture reaining (diensionless) t = Drying tie (ja) = Subliation rate X = Water content kg. H O kg. dry kg. s Figure 17 Profile of cold trap teperature q = Heat flux W 4.0 CONCLUSION The influences of cobinations internal cooling and vacuu freezing have been tested. Result show that vacuu freezing have ass loss 1.4% higher than conventional freezing or internal freezing (Run no. 1 and ), Cobination between internal cooling and vacuu freezing have effect 0.3% better than vacuu freezing due to internal cooling and vacuu freezing run concurrently. The effect of condenser heat loss can be reducing drying tie 30% (Run no. 1 and ). idilli thin layer odel can use to predict oisture ratio curve but the value of Constanta (k, a, b, n) need to redefine for jelly fish use. oisture ratio decreased with drying tie in all drying processes. When decrease drying chaber need to observe the pressure saturation of product, if pressure saturation product lower then pressure of drying chaber the ass transfer should not occurs. The activated of heating fro condenser s heat loss can increased the drying rate of vacuu drying process fro g/ s at without heating becoe g/ s with heating at 44 o C. The activated heating fro condenser s heat loss also have effect to cold trap teperature. Cooling load of cold trap at the beginning cae fro flash point of aterial before reach freezing teperatur and then at priary and secondary drying cae fro oisture content which is reoved fro aterial. Acknowledgeent The authors acknowledge the financial support fro DRP UI (Research Centre of UI) Contract: DRP / RSN-UI / 011 / 1 / 1071 Noenclature Notation P = Pressure (bar) Greek letters L = Distance of frozen surface fro the top () = Theral conductivity of ice W k. kg p = ass density 3 Subscripts w = Water d = drying = aterial s = solid References [1] George, J. P., A. K. Datta. 00. Developent and Validation of Heat and ass Transfer odels for Freeze-Drying of Vegetable Slices. Elsevier Journal of Food Engineering. (5): [] Chakraborty, R., A. K. Saha, P. Bhattacharya odeling and siulation of Paraetric Sensitivity in Priary Freeze-Drying of Foodstuffs. Elsevier Separation and Purification Technology. (49): [3] Ghio, S., A. A. Barresi, G. Rovero A Coparison of Evaporative and Conventional Freezing Prior to Freeze-Drying of Fruits and Vegetables. IChe Journal [4] Holkeboer and David, H Vacuu Technology and Space Siulation. Boston Technical Publishers, USA. [5] Alibas, Ilknur Energy Consuption and Colour Characteristics of Nettle Leaves During icrowave, Vacuu and Convective Drying. Elsevier Biosystes Engineering. 4: [6] George-Wilhel Oetjen., Peter Haseley Freeze Drying. Second, Copletely Revised and Extended Edition. WILEY-VCH Verlag GbH&Co. KGaA, Weinhei. [7] Ozturk, Hande utlu., Harun Keal Ozturk Effect of Pressure on the Vacuu Cooling of Iceberg Lettuce. International Elsevier International Journal of Refrigeration. 3:

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