3 rd International conference on agricultural and food engineering Low-pressure microwave heating system for drying of swiftlet bird s nest Mudtorlep Nisoa Plasma technology for agricultural application laboratory Green Innovation in Physics for Agro-industry Center of excellence Walailak University
Walailak University Nakhon Si Thammarat
Topics Microwave and microwave interaction with bio-materials Swiftlet bird s nest and requirement for drying Low pressure microwave drying system Experimental setup Results and discussion Conclusion and future work
Microwave and its interaction with bio-materials Maxwell s equations E = B t H = J + (εe) t
Microwave and its interaction with bio-materials Dielectric heating materials j Dipole molecules Selective heating
Applications of microwave heating Extraction T < 180 o C T < 100 o C Cooking Microwave Heating T < 60 o C Drying Processing of materials T > 300 o C
Advantages of microwave drying Alternative use during rainy season Fast and energy efficiency Preserve good qualities Bulk heating
Swiftlet bird s and requirement for drying Swiftlet bird s nest, known as healthy functional food in Asia. It is good for skin care, curing respiratory malfunction. It is impressed as Caviar of the East. Products from Malaysia http://www.thestar.com.my/business/sme/2013/08/01/a-growing-nest-egg-forone-company-the-growing-popularity-of-birds-nest-products-is-providing-lucrat/
Swiftlet bird s and requirement for drying Cleaning Forming natural swiftlet bird s nest Drying
Low-pressure microwave drying Microwave vacuum drying Kudra, T., and Mujumdar, A. S. (2002). Advanced drying technologies.
Low-pressure microwave drying Kudra, T., and Mujumdar, A. S. (2002). Advanced drying technologies.
Experimental setup Vacuum chamber Magnetron and waveguide Condenser for water and oil trap Low- pressure microwave drying system
Experimental setup Vacuum gauge Leak valve Magnetron and waveguide Vacuum chamber condenser Gate valve pump drain Schematic diagram of low- pressure microwave drying system
Experimental setup Bird s nest inside the chamber(microwave cavity)
Experimental results Drying curves
Experimental results Natural bird s nest Clean and wet bird s nest Microwave drying at 50 W Microwave drying at 100 W Microwave drying at 150 W Dried bird s nest from local market Comparing color of bird s nest
Experimental results Bird s nest Color values L*(Lightness) a*(redness) b*(yellowness) Clean and wet bird s nest 72.5 1.5 14.7 Microwave drying at 50 W 77.6 2.1 21.1 Microwave drying at 100 W 79.1 2.4 19.4 Microwave drying at 150 W 82.7 1.8 17.1 Cold and dry air convection 77.0 4.0 18.3 Local market 70.1 3.8 20.8 Export 76.3 1.4 21.1 Comparing color of bird s nest
Experimental results Bird s nest % of Protein Clean and wet bird s nest 74.0 Microwave drying at 50 W 79.1 Microwave drying at 100 W 78.9 Microwave drying at 150 W 78.9 Local market 1.4 Cold and dry air convection 62.9 Export 61.7 Percentage of protein of the bird s nest
Experimental results Rehydration of the bird s nest 50 W 100 W 150 W 0 5 mins 10 mins 15 mins
Experimental results Rehydration of the bird s nest
Conclusion and future work 1. Low pressure microwave drying system which is suitable for drying swiftlet bird s nest and other heat sensitive material has been developed 2. Good qualities of the bird s nest, such as colour and protein content, can be preserved 3. Drying time is shorten to be only about 2 hours 4. Scaling up of low-pressure microwave drying system for industrial prototype is in progress
Acknowledgements We would like to thank Office of higher education commission and Praduu engineering company for their financial support.
Thank you very much Questions and Comments
Low-pressure microwave heating system for drying of swiftlet bird s nest M. Nisoa 1,a and P. Kerdthongmee 2 1 Faculty of Science, Walailak University, Nakhon-si-thammarat, Thailand; 2 Center for scientific and technological equipment, Walailak University, Nakhon-si-thammarat, Thailand Abstract The swiftlet bird s nest is famous for high-valuable functional food, which is popular among Asian countries. Southern provinces of Thailand, especially Nakhon-sithammarat, have produced the bird s nest commercially both for local need and for export. For conventional drying, cold and dry air is used to dry the nest. The drying time is very long, about 22 hours. Low-temperature is critically important to preserve the high-quality of the nest, especially its colour. We have developed the low pressure microwave system to dry the nest more effective, shorten the time to be less than 2 hours. The system consist of vacuum chamber, microwave power unit, condensing chamber for trapping moisture and oil vapour. Adjustable microwave power by using phase control has been developed. Microwave power is generated by magnetron by mean of energy conversion from electricity. The microwave is transmitted through Waveguide to the multi-mode cavity to dry the nest. We have successfully dried the nest by low temperature and short period of time to preserve its colour and protein. The low pressure microwave system is suitable for drying the bird s nest, which can be scaled up for industrial prototype. Keywords: swiftlet s nest, microwave vacuum drying, phase control microwave power INTRODUCTION Figure 1(a) shows the Swiftlet bird s nest, known as healthy functional food in Asia. It is good for skin care, curing respiratory malfunction. It is impressed as Caviar of the East (Zainab et al., 2013). (a) Figure1(a) natural swiftlet bird s nest and (b) Clean and white swiftlet bird s nest (b) a E mail: mnisoa@gmail.com
Typically people consume the nest for their good health and living well. The nutrition contents of the swiftlet bird s nest are fat, carbohydrate and protein of 0.14-1.28%, 25-27% and 62-63%, respectively (Glai-more Magazine, 1988; Zainab et al., 2013; Mei et al., 2014; Babji et al., 2015). The protein of the nest is special, known as glycoprotein. Its precursor substance, which has higher nutrition than normal protein, can boost immunity and stimulate the growth the skin cell. It also has inhibition effect to inhibit the contamination of bacteria, fungi and virus. To process the bird s nest for food product, first raw nest is put is clean water to eliminate the dirt, such as dust, feather. The clean one is shown in Fig.1(b). Then the nest is dried for preservation. Since the bird s nest is very sensitive to temperature, its quality will be deteriorated if the temperature is higher than room temperature (Gan et al., 2015). For conventional drying, cold and dry air is used to dry the nest. The drying time is very long, about 22 hours, which is not practical for industrial production. Freeze drying is the most appropriated method to dry bird s nest (Gan et al., 2015). Drying at temperature below zero can keep original value of the nest. Freeze drying system requires sophisticated vacuum pump and condensing unit which are very expensive. Microwave vacuum(mv) takes advantage of microwave heating and moderate pressure to dry materials at room temperature as shown in Figure2. The qualities of drying products are good enough for herbs and foods, whereas its cost is much cheaper than freezing dry. We have developed low pressure and low temperature microwave drying system to reduce the drying time and preserve the good quality of the nest. Low-temperature is critically important to preserve the high-quality of the nest, especially its colour. Figure2 Pressure-temperature curve showing conditions for feeze-drying, Microwave vacuum(mv) and air drying (T. Kudra and Arun S. Mujumdar, 2002) MATERIALS AND METHODS Experimental setup We have developed the low pressure microwave system to dry the nest more effective, shorten the time to be less than 2 hours. The system consist of vacuum chamber, microwave power unit, condensing chamber for trapping moisture and oil vapour. Adjustable microwave power by using phase control has been developed. Microwave power is generated by magnetron by mean of energy conversion from electricity. The microwave is transmitted through Waveguide to the multi-mode cavity to dry the nest. The picture and diagram of the system are shown in Fig. 3 and Fig. 4, respectively.
Vacuum chamber Magnetron and waveguide Condenser for water and oil trap Figure 3. Low- pressure microwave drying system Vacuum gauge Leak valve Magnetron and waveguide Vacuum chamber condenser Gate valve pump drain Figure 4. Schematic diagram of Low- pressure microwave drying system
RESULTS AND DISCUSSION The drying time of the bird s nest in Fig. 5 shows that the nest can be dried to have moisture content less than 1% within three hours. Depending on microwave powers, drying time is varied, more high power have shorter drying time. At 150 watts, drying time is about 2 hours. Since the nest is dried at low temperature in a short time, its colour is still white as the original one. Figure 6 shows the comparison between the original bird s nest and the dried bird s nest by low pressure microwave drying system. Figure 5. Dependence of percentage of moisture content on drying time Original bird s nest Dried bird s nest by low microwave Dried bird s nest from market Figure 6. Comparison of color of bird s nest Table 1. Comparison of percentage of protein for different kinds of bird s nest Swiftlet bird s nest % of protein Original wet bird s nest 74.0 Dried by 50 watts of microwave 79.1 Dried by 100 watts of microwave 78.9 Dried by 150 watts of microwave 78.9 Dried bird s nest from local store 1.4
Dried by wind convection in air conditioned room 62.9 Export grade of dried bird s nest 61.7 Table 1 shows the percentages of the protein of the bird s nests. It is seen that drying bird s nests by low pressure microwave system can preserve higher content of protein than conventional drying method. Low temperature and shorter time by microwave plays the key role for higher content of protein. CONCLUSIONS We have shown that low pressure microwave drying system is suitable to dry the swiftlet bird s nest. The good qualities of the bird s nest, such as colour and protein content, can be preserved. The drying time is shorten to be only about 2 hours. The protein content is high as the original one. The drying system can be developed to increase drying capacity for industrial prototype. ACKNOWLEDGEMENTS We would like to thank Thailand Center of Excellence in Physics(ThEP) and Commission on Higher Education (CHE), for their financial support. Literature cited Glai-more Magazine.(1998) Vol.23, No.2, February (in Thai) Zainab, H., Nur H. I., Sarojini, J., Kamarudin, H., Kamarudin, H., Othman, H., and Boon-Beng, L. (2013). Nutritional properties of edible bird nest. Journal of Asian Scientific Research, 2013, 3(6):600-607. Mei, Y., Sau-Ha, C., Sze C L., and Hon-Yeung, C. (2014). Establishment of a holistic and scientific protocol for the authentication and quality assurance of edible bird s nest. Food Chemistry 151 (2014) 271 278. Babji, A. S., Nurfatin, M. H., Etty Syarmila, I. K., and Masitah, M. (2015). Secrets of edible bird nest. UTAR AGRICULTURE SCIENCE JOURNAL l VOL. 1 NO. 1. Gan, S.H., Law, C. L., and Ong, S P. (2015). Review on challenges and future drying trend in edible bird s nest industry in Processing of Foods, Vegetables and Fruits: Recent advances, Ed. Hii, C.L., Jangam, S.V., Ong, S.Z., Show, P.L., Mujumdar, A.S. ISBN - 978-981-09-6284-5, Published in Singapore, pp. 45-60. Kudra, T., and Mujumdar, A. S. (2002). Advanced drying technologies. Marcel Dekker Inc. New York, NY, 459 p. Hao, F., Yun, Y., and Juming, T. (2012). Microwave Drying of Food and Agricultural Materials: Basics and Heat and Mass Transfer Modeling, Food Eng Rev., 4:89 106 Orsat, V., Yang, W., Changrue, V., and Raghavan, G. S. V. (2007). MICROWAVE-ASSISTED DRYING OF BIOMATERIALS, Trans IChemE, Part C, Food and Bioproducts Processing, 85(C3): 255 263 Vadivamba, R. l., and Jayas, D.S. (2007). Changes in quality of microwave-treated agricultural products a review, BIOSYSTEM ENGINEERING 98, p. 1-16 Zhang, M., Tang, J., Mujumdar, A. S., and Wang, S. (2006). Trends in microwave related drying of fruits and vegetables, Trends in Food Science & Technology 17, p. 524 534 J.I. Lombraña and et.al., Microwave-drying of sliced mushroom. Analysis of temperature control and pressure, Innovative Food Science and Emerging Technologies 11 (2010) 652 660
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