JOURNAL OF READY TO EAT FOOD Journal homepage: www.jakraya.com/journal/jref Solar Drying of Osmosed Aonla Flakes for Preparation of Aonla Candy Anil K. Kamble a * and Namita S. Lavande b ORIGINAL ARTICLE a Assistant Professor, All India Co-ordinated Research Project on Renewable Energy Sources and b Former M. Tech. Student, Department of Unconventional Energy Sources and Electrical Engineering, Dr. Panjabrao Deshmukh Agricultural University, Post- Krishi Nagar, Akola 444 104, (M.S.) India. *Corresponding Author: Anil K Kamble Email: anilkumar_kamble@hotmail.com Received: 01/07/2014 Revised: 29/08/2014 Accepted: 20/09/2014 Abstract A low cost portable PAU farm solar dryer was evaluated for drying of Aonla (gooseberry) candy in the conditions of Vidarbha region of Maharashtra State. Temperature profile at top, middle and bottom in its seven trays loaded with aonla candy was studied with respect to ambient temperature during the course of drying. The temperature variation in the drying trays of the dryer was found in the range of 23 to 36 C, 31 to 48 C and 38 to 55 C in bottom, middle and top trays of dryer, respectively. The moisture content was reduced from 36.38 to 8.62 per cent (wb) in four days in solar drying method; whereas eight days were required for the same in conventional method of drying. The drying period was reduced by 50 per cent compared to the conventional shade drying method. Appearance, taste and flavour of aonla berry candy dried in farm solar dryer were superior to conventional drying. Keywords: Farm solar dryer, Goose berry candy, Solar radiation, Dryer efficiency. Introduction The earth receives solar energy at a range of 5.4 10 24 J/year. This is equivalent about 30,000 times the sources used at the present time. India lies between altitude 7 and 37 N and receives an annual average intensity of solar radiation between 4651 to 8134 W/m 2 /day. Annual daily diffuse radiation received over the whole country is about 872 W/m 2 /day (Rai, 1994). Solar energy is non-polluting, plenty and perennial source. Fortunately the solar energy from sun is available to solve the energy crises. Drying was probably the first ever preservation method used by human, ever before cooking. The removal of water content from the product under controlled conditions of airflow, temperature and humidity is called drying. Chinese, Hindus, Persians, Greeks and Egyptians practiced the drying of fruits and vegetables since ancient s times. The ancient people dried herbs, fruits and vegetables with the help of sun and wind five thousand years ago. Dates and figs were sun dried by early inhabitants of middle and rear east. Solar drying is process familiar to all farmers. It is the process in which the heat of the sun is used to dry produce so that such produce does not get spoiled or damaged easily and can be stored for long time thereafter. After the produce is dried, it becomes very easy to store it for a long time and to transport it from one place to another without fear of rotting etc. Sun drying perhaps is the cheapest method of food preservation but requires very huge space per unit of material dried and is time consuming dependent fully upon uncontrolled weather conditions. This delay often causes mould growth deterioting the quality. To meet the demand of the present age sun drying is gradually being replaced by mechanical drying by means of dryer. Drying is based on the principle of increasing the moisture carrying capacity of air by increasing its temperature and causing lower relative humidity. Thus increasing the moisture absorption capacity, when this air is passed over the material to be dried it produces vapour pressure gradient placed from material at high vapour pressure to low-pressure air until equilibrium is reached. Vegetables dried by traditional open air sun drying are time consuming, less hygienic and climate dependent. In industrialized regions and sectors mechanized dryers with boilers to heat incoming air and fans to force it at a high rate are now largely replaced by open air-drying. Mechanized drying is faster than open-air drying. In addition, reduction of moisture content results in preservation of quality characteristics such as flavour and nutritive value. Another objective of drying is the significant reduction in product volume. This promotes easy and efficient transportation and storage of the food product. Solar
energy is the cheapest source of heat for removal of water from agricultural produce. However, with sun drying come the risk of losses due to inclement weather and the difficulty of maintaining high degree of sanitation. The use of solar energy as a source of renewable energy is received more attention for saving conventional energies. Fortunately India is blessed with plenty of sunshine. The daily average solar energy incident in the country varies from 5-7 kwh/m 2, approximately 5 10 15 kwh/m 2 of energy per annum from the sun is received in India (Jain et al., 2004; Seveda et al., 2004). Most of the agricultural, horticultural and forest products are either spoiled due to lack of proper sundrying or sold to the adjoining markets at meager prices. The farmers and entrepreneurs use open sun drying or shade drying for products but they are neither aware of solar drying of these products with solar dryers nor these gadgets have ever been tested and demonstrated in the Vidarbha region of Maharashtra. The industries are not properly using the available solar radiation for the drying of agricultural produce. The use of solar dryers can results in the value addition of their produce and even the leaves of wild plants and medicinal herbs after proper drying can fetch good prices provided the suitable efficient designs of the dryers at the affordable cost can be provided to the farmers (Shafiq and Singh, 2010). Akola district of Maharashtra state is situated at 77 2 E longitude and 20 42 latitude having altitude of 281 m above mean sea level. Due to high temperature the solar radiations are abundantly available in this region. Hence for the proper utilization of solar energy most of the processing industries take advantage of it. Abundant amount of goose beery local name is aonla (Phylanthus emblica) fruits are available in this region. During the processing of candy, drying is major unit operation and advantage of availability of solar radiation should have to take in the consideration. These fruits are used to prepare various products such as candy, beverages, supari, and powder in region. These products are normally sun dried or shade dried which is a cheap method. But it often results in inferior quality. Solar drying can be considered as an elaboration to sun drying and is an efficient system of utilizing solar energy. The use of solar dryer can results in the value addition of their produce. Multi-rack farm solar dryer using natural convection is developed for drying agricultural products (Hayati and Rzayer, 2002). This farm dryer does not required electric power for its working and it does not require any attention once the product is loaded. The portable farm solar dryer was demonstrated to the entrepreneur and evaluated its performance for drying aonla candy. Beisdes, many researchers opted osmo dehydration prior to convective drying (Sutar and Sutar, 2013). Material and Methods The conventional method of goose berry candy preparation, drying methods, equipments used and identification of improvement in drying methods in small-scale industries was studied. Industrial survey was conducted to study the existing methods of candy preparation and drying. The procedure for making candy from raw goose berry is given as below (Fig 1). Fig 1: Process flow chart for goose berry candy preparation Selected the proper size, appearance, less astringent fruits for processing, washed fruits thoroughly in water for one hour and remove it. The whole fruits were steamed for 10 minutes in autoclave at pressure of 0.75 kg/cm 2. After steaming the steamed fruits were allowed to cool down to normal temperature and the flakes were separated. These flakes had moisture content of 87 % wb. The flakes were exposed to open air under shade for 24 h. This was followed by osmotic dehydration of flakes for next 18 hours using sugar syrup (70 Brix) in proportion of 500 g of flakes into 1000 ml of syrup, maintained at temperature of 85 C (Biswal and Bozorgmehr, 1992; Lazarides et al., 1995; Kamble et al., 2010; Kamble et al., 2011). The process was facilitated with stirring at regular interval of 2 to 2.5 hours. After osmotic dehydration, the draining off of the syrup from osmosed flakes was allowed for seven hours. Thus osmosed flakes had 121
moisture content of 36.38 % wb, i.e, 57.18 % db. This is traditional way to prepare osmosed aonla flakes as if used for AMRUT Aonla, a well known local brand. These osmosed flakes were subjected to conventional shade drying (as practiced by Small scale entrepreneurs) and using PAU farm solar dryer (available with the Department of UCES and EE, Dr. PDKV, Akola) for further experimental study. Fig 1 presents the process flow chart for candy making process at Amrut Aonla Industry. Conventional Shade Drying Methods Goose berry candy was dried in shade using M.S. racks with polynet, open sun drying and in open shade drying. The shade drying method was adopted in M/s Amrut Awala industry for drying candy (Fig 2). The processed candy was firstly washed with hot water and uniformly spread over the Mild steel racks prepared for drying whereas in M/s Awala Candy, Partawada and M/s Vharadi Awala, Digras industries dried processed candy by spreading uniformly in open yard. holding seven trays. These trays were made of mild steel angle with perforated stainless steel wire mesh base. The glazing consists of ultra violate stabilized polyethylene sheet of 200 micron sheet fitted on upper frame and the frame was mounted on a castor wheels for easy loading and unloading of products used for drying (Fig 4). Method of Installation, Operation and Maintenance of PAU Portable Farm Solar Dryer Portable farm solar dryer needs no installation as such for its working. The side view of PAU farm solar dryer is shown in (Fig 5). When drying is to be done, it can be placed at a location where sunshine is available for most part of the day. To avoid it s overturning due to wind it needs to be fixed to the ground. Fig 3: PAU Portable Farm Solar Dryer Fig 2 Conventional shade drying method PAU Portable Farm Solar Dryer Table 1 shows the specification for PAU (Panjab Agricultural University, Ludhiana, India) Portable Farm Solar dryer (Fig 3). Table 1: Specifications of PAU Portable Farm Solar dryer SN Particulars Specifications 1. Aperture Area, m 2 3.34 2. No. of trays Nos. 7 3. Size of dryer, mm 1830 1890 330 4. Wt of dryer, kg 40.5 5. Loading/ batch, kg 20-30 (Depending upon the product) 6. Inclination of dryer, degrees 45 for northern India 30 for southern India The dryer have four important parts such as supporting frame, trays and glazing. The supporting frame was made from nickel-plated mild steel angle for Fig 4: Movable glazing arrangement of PAU portable farm solar dryer Experimentation Fresh fruits were procured from farm and the candy was prepared with procedure adopted by M/s Amrut Awala, Akola industry. Candy of 21 kg were taken and loaded in the multi layers dryer trays with three kg in each tray. The candy was loaded at 09.00 h and removed at 16.00 h every day. Drying parameters were studied from March to April. Solar radiation falling on the solar collector of the dryer, temperatures 122
inside the dryer in all seven trays were recorded for unloading and loading condition after every 30 min interval. Prevailing practice of candy drying was also studied to examine the performance of solar dryer. The weight of the candy loaded for drying in each tray was measured before loading and at the end of each consequent day of drying. Samples were taken and the initial and final moisture contents during the study were determined using standard oven drying method. The loss in weight was recorded at regular interval of two hours. The efficiency of dryer was calculated using the following equation (Desai et al., 2002). candy were conducted based on verbal conversation in order to study prevailing method and appliances used for drying goose berry candy. It is seen that goose berry candy preparation was same in all the industries, but it differs in drying procedure adopted i.e. shade drying in trays was used at M/S Amrut Awala where as at Awala Candy, Paratwada Varhadi Awala, Digras open sun drying was practiced. It was observed that among all M/S Amrut Awala, Akola found superior over others in regard to quality and taste. Therefore, the procedure followed by M/S Amrut Awala was adopted for research work. Results and Discussion Where, m e Moisture evaporated (kg), L Latent heat (kj/kg), I av - Average solar input (kw/m 2 ), A Aperture area (m 2 ), t Drying time (sec) Fig 5: Side view of farm solar dryer The farm solar dryer is essentially poly-house where incident radiation over the glazing material can transmit inside the drying chamber and boost up temperature of air enclosure. During the day time, the solar energy enters the dryer from the transparent cover of the dryer get absorbed by the product inside the dryer. The objects in turn emit long radiation for which transparent cover act as opaque material or have low transparency. As a result of which energy is trapped inside the dryer and its temperature increases (Hachemi et al., 1998; Sharma et al., 1994). All India Coordinated Research Project on Renewable Energy Sources, Dr Panjabrao Deshmukh Krishi Vidyapeeth, and Akola Centre has carried out evaluation of portable farm solar dryer for drying goose berry candy at entrepreneur s site M/s Amrut Awala, MIDC, Akola. Survey of three different locations viz., Amrut Awala, Akola, Awala candy, Paratwada and Varhadi Awala, Digras engage in preparation of goose berry Conventional Method of Drying Goose Berry/ Aonla Flakes Shade drying method was adopted to dry the processed aonla flakes in M/S Amrut Awala, Akola. The processed flakes were uniformly spread on the green net of the rack in shade. Observations like temperature, moisture content and weight loss were recorded during course of drying. The temperature of 19.5 to 25.1 C was observed in shade drying from 0900 to 1600 and covered with polythene sheet after 1600 h (Table 2). The weight loss observed is presented in (Table 3). Drying of Osmosed Aonla Flakes in PAU Portable Farm Solar Dryer Temperature variation during aonla flakes drying in portable farm solar dryer is presented in Table 2. The temperature range of 23 36 C, 31 48 C and 38 55 C were observed in bottom, middle and top trays, respectively. The temperature attended in the drying trays corresponding to the drying time is given in the Table 2. The periodical weight loss in product in all seven trays is given in Table 3. The variation in temperature of different seven trays of the dryer is shown in Fig 6 during drying of aonla flakes. The maximum temperature of 55 C was attended in top and its consequent tray, while it was 36 C in bottom tray of the dryer and this might may due to the moisture content reduced from initial moisture content of 36.38% to 8.82, 8.88, 8.01% (wb) in bottom, middle and top trays, respectively. Thus on an average the moisture content was reduced from 36.38% to 8.62% in four days. Efficiency of portable farm solar dryer was determined and presented in Table 4. From Table 4 it is observed that thermal efficiency of the dryer on first day of drying was higher (15.23%) and gradually it decreased from 15.23 to 0.13% from 1 st to 4 th day of the drying, respectively. The goose berry candy sample was given to the five - 123
Time, H Table 2: Temperature accumulated in the dryer during drying process Temperature in respective trays, C 1(bottom) 2 3 4 (middle) 5 6 7 (top) Shade drying temp, C 09.00 23.0 25.0 27.0 31.0 32.0 35.0 38.0 19.5 09.30 24.5 26.5 29.5 33.5 34.0 36.0 39.0 20.0 10.00 25.0 28.0 32.0 36.0 37.0 37.0 40.0 20.5 10.30 26.0 30.0 37.0 38.0 39.0 40.0 41.0 20.4 11.00 27.0 31.0 39.0 41.0 42.0 44.5 44.0 21.5 11.30 29.0 33.0 41.0 43.0 44.5 47.0 47.0 21.5 12.00 30.0 36.0 43.0 45.0 48.0 50.0 50.0 22.0 12.30 31.0 38.0 45.0 46.0 48.0 55.0 55.0 23.5 13.00 33.0 42.0 46.0 46.5 48.0 53.5 53.5 23.2 13.30 34.5 44.0 47.0 48.0 49.0 53.0 53.0 23.3 14.00 35.5 40.0 46.0 46.0 52.0 53.0 53.0 23.5 14.30 36.0 40.0 46.0 46.0 50.0 54.0 52.0 24.5 15.00 34.0 39.0 42.0 44.0 49.0 49.0 52.0 24.9 15.30 33.0 37.0 40.0 42.0 43.0 43.0 45.0 25.0 16.00 32.0 35.0 38.0 40.0 41.0 41.0 42.0 25.1 Drying time, h Table 3 Moisture content of aonla flakes during drying process Moisture content, per cent (wb) Solar drying trays 1 2 3 4 5 6 7 Conventional drying (wb) 0 36.38 36.38 36.38 36.38 36.38 36.38 36.38 36.38 2 32.12 29.78 18.24 17.89 22.8 20.4 18.57 26.34 4 28.14 28.2 17.92 16.92 16.67 16.52 16.65 18.7 6 24.14 23.12 16.13 15.87 15.82 15.38 15.85 17.00 8 22.85 21.07 15.72 14.82 13.11 13.72 13.11 17.32 10 21.97 19.37 14.19 13.85 13.00 12.57 12.00 16.90 12 18.90 15.50 13.95 12.92 12.87 11.00 11.14 16.75 14 15.75 14.8 13.75 10.99 11.01 10.83 10.57 16.10 16 12.03 12.00 13.17 11.27 11.12 10.57 9.83 15.62 18 10.22 11.11 11.01 10.11 11.09 10.95 9.59 16.82 20 9.92 9.78 9.70 9.67 9.99 10.01 9.34 15.01 22 9.75 9.17 9.74 9.63 9.67 9.98 9.13 14.98 24 9.87 9.12 9.68 9.43 9.75 9.78 8.88 14.44 26 9.72 8.90 9.50 9.21 8.92 9.97 8.57 13.92 28 8.96 8.72 9.45 9.1 8.83 8.78 8.43 13.58 30 8.82 8.63 8.96 8.88 8.57 8.52 8.01 12.18 32 11.32 34 11.14 36 11.01 38 9.97 40 9.78 42 9.33 44 9.12 46 9.03 48 8.39 50 8.57 52 8.44 54 8.33 124
Table 4 Efficiency of the farm solar dryer Particulars Moisture evaporated, kg Thermal efficiency, % Drying period, days 1 2 3 4 4.92 0.79 0.45 0.05 15.23 2.47 1.33 0.13 60 Tray 1 Tray 2 Tray 3 Tray 4 Tray 5 Tray 6 Tray 7 50 Temerature, oc 40 30 20 10 0 Time during day hours, h Fig 6: Temperature develop in portable farm solar dryer for drying aonla flakes Fig 7: Conventional shade dried aonla candy Fig 8: Solar dried aonla candy 125
users for collecting their feedback. According to the users it was found that the taste and flavour of goose berry candy dried in portable farm solar dryer was superior. The aonla flakes dried in portable farm solar dryer has soft texture, less astringent taste as compared to aonla flakes dried in conventional method. The appearance i.e. colour of solar dried candy was reddish brown, which was more attractive than the aonla flakes dried by conventional method (Fig 7 and 8). Conclusions PAU Portable Farm solar dryer is a simple, convenient and low cost technology. Drying of aonla References Biswal RN and Bozorgmehr K (1992). Mass transfer in mixed solute osmotic dehydration of apple rings. Transaction of American Society of Agricultural Engineers (ASAE), 35: 257-262. Desai SR, Kumar V and Guruswamy T (2002). Performance evaluation of mini multi-rack solar dryer for grapes drying. Journal of Agricultural Engineering Today, 26 (3-4): 30-37. Hachemi AC, Abed B and Asnoun A (1998). Theoretical and experimental study of solar dryer. Renewable Energy, 13(4): 439-451. Hayati O and Rzayer P (2002). New drying systems for crops. International Journal of Global Energy, 17(1): 106-112. Jain NK, Kothari S and Mathur AN (2004). Technoeconomics evaluation of a forced convection dryer. Journal of Agricultural Engineering, 41(31): 6-12. Kamble AK and Gadge SR (2010). Studies on portable farm solar dryer for drying gooseberry candy (2010). International Journal of Green Farming, 1(3): 323-325 Kamble AK, Kalbande SR and Gadge SR (2011). Solar drying system for energy conservation applied solar (gooseberry) flakes in this farm solar dryer saves the product from contamination and is effective in unfavourable environment conditions like high wind velocity, heavy rainfall, etc. The taste, flavour and appearance of aonla candy dried in this dryer was superior to that dried using conventional shade drying. Besides, the PAU Farm Solar dried aonla candy had soft texture and less astringent taste as compared to aonla candy dried by local method. The appearance of solar dried aonla candy was reddish brown, which was more attractive than the candy dried by conventional method. energy. Applied Solar Energy (Springer), 47(2): 124-133. Lazarides HN, Katsanidis E and Nickolaides A (1995). Mass transfer kinetics during osmotic pre concentration aiming at minimal solid uptake. Journal of Food Engineering, 35: 151-166. Rai GD (1994). Solar energy utilization. Khanna Publications, New Delhi. pp 1-3. Seveda MS, Rathore NS and Singh P (2004). Technoeconomics of solar tunnel dryer A case study. Journal of Agricultural Engineering, 41(3): 13-17. Shafiq A and Singh A (2010). Optimum process parameters for development of sweet aonla flakes. International Journal of Research and Reviews in Applied Sciences, 3(3): 323-333. Sharma VK, Colangelo A and Spagna G (1994). Experimental investigation of different solar dryers suitable for fruit and vegetable drying. Renewable Energy, 6(4): 413-423. Sutar N and PP Sutar (2013). Developments in osmotic dehydration of fruits and vegetable- a review. Trends in Post Harvest Technology, 1(1): 20-36. 126