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

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

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.

Swiftlet bird’s and requirement for drying

natural swiftlet bird’s nest

CleaningForming

Drying

Low-pressure microwave drying

Kudra, T., and Mujumdar, A. S. (2002). Advanced drying technologies.

Microwave vacuumdrying

Low-pressure microwave drying

Kudra, T., and Mujumdar, A. S. (2002). Advanced drying technologies.

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 setup

Bird’s nest inside the chamber(microwave cavity)

Experimental results

Drying curves

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

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. 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: mnisoa@gmail.com

(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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