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Mudtorlep Nisoa
Plasma technology for agricultural application laboratoryGreen Innovation in Physics for Agro-industry Center of excellence
Walailak University
Low-pressure microwave heating system for drying of swiftlet bird’s nest
3rd International conference on agricultural and food engineering
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
Dipole molecules
j
Selective heating
Applications of microwave heating
Microwave Heating
T < 100o C
T < 180o C
T < 60o C
T > 300o C
Cooking
Processing of materials
Extraction
Drying
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
Products from Malaysia
http://www.thestar.com.my/business/sme/2013/08/01/a-growing-nest-egg-for-one-company-the-growing-popularity-of-birds-nest-products-is-providing-lucrat/
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.
Low-pressure microwave drying
Kudra, T., and Mujumdar, A. S. (2002). Advanced drying technologies.
Microwave vacuumdrying
Vacuum chamber
Condenser for water
and oil trap
Magnetron and
waveguide
Experimental setup
Low- pressure microwave drying system
Experimental setup
Vacuum
chamber
Magnetron
and
waveguide
condenser
pump
Vacuum gauge Leak valve
drain
Schematic diagram of low- pressure microwave drying system
Gate valve
Experimental results
Comparing color of bird’s nest
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
Experimental results
Comparing color of bird’s nest
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
Experimental results
Percentage of protein of the bird’s nest
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
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.
Low-pressure microwave heating system for drying of swiftlet bird’s nest
M. Nisoa1,a and P. Kerdthongmee2 1Faculty of Science, Walailak University, Nakhon-si-thammarat, Thailand; 2Center 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-si-
thammarat, 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).
aE‐mail: [email protected]
(a) (b)
Figure1(a) natural swiftlet bird’s nest and (b) Clean and white swiftlet bird’s nest
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.
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.
Figure2 Pressure-temperature curve showing conditions for feeze-drying,
Microwave vacuum(MV) and air drying (T. Kudra and Arun S. Mujumdar, 2002)
Figure 3. Low- pressure microwave drying system
Vacuum chamber
Condenser for
water and oil trap
Magnetron and waveguide
Vacuum chamber
Magnetron and
waveguide condenser
pump
Vacuum gauge Leak valve
drain
Figure 4. Schematic diagram of Low- pressure microwave drying system
Gate valve
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.
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
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
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
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