ultrasound-assisted drying is a novel drying technology which enhances the rate of drying and causes the least change in quality aspects

1. 1
Semr.4102 Seminar 2 (0+1)
Presented by :
HARIKRISHNAN M.P
2015-06-009
B.Tech food engineering

2. 2
Case studies
04
principle 03
Ultra sound assisted
drying
What is power ultra
sound
02
01

3. 3
Introduction
Food processingThermal
processing
Non thermal
processing
 Producing fresh like foods by replacing thermal treatments
-High hydrostatic pressure (HHP)
-Irradiation
-Pulsed electric field
- Pulsed light
-Ultrasound processing

4. 4 Contd..
Application of ultrasound in food industries
Cutting
freezing
homogenization
Foaming and defoaming
Filtration and extraction
drying

5. Ultrasound assisted drying
5
 DRYING
 Traditional method of preservation of food
 Generally done at a temperature range of 40-80°c for 24-48hrs
 By reducing the water activity of food (reduction of water content)

6. 6 Contd..
V p of food > v p of atmosphere
food
𝐻2O
𝐻2O

7. 7 Contd..
DISADVANTAGES
─ change in physical and chemical composition
─ High temperature and time can alter the quality attributes
─ discolouration
─ Aroma loss
─ Textural loss
─ Changes in appearance and shape
─ Nutritional loss

8. 8
Ultrasound
infrasound Audible Ultra sound
20Hz 20kHz
 It can be classified in to
 High-power ultra sound – 20-100kHz
 High frequency ultrasound- 100kHz-1MHz
 Diagnostic ultrasound-1-500MHz
 Ultra sound pass through any physical medium, compressing and stretch the molecule they
pass through

9. 9 Contd..
 The wave form will have compression and rarefaction cycles
 By using this phenomenon the sound helps to assist the drying

10. 10
Ultrasound assisted drying
 Ultra sound helps to reduce the temperature and time for drying
 It can be done by following methods
 Direct
 indirect

11. 11
Hot air generator
weight
anemometer
thermometer
microphone
Electronic generator
transducer
Vibrating plate
samples
Direct ultrasound assisted dryer
Contd..

12. 12
Indirect ultrasound assisted dryer
Stain less steel tank
Product
U
t
U
t
U
t
U t
Sonicating
medium
Electric generator
Contd..

13. 13
Components of ultra sound assisted drying system
• Ultra sonic generation system and Sonication horn
• Heat supply
• Treatment chamber
Contd..

14. 14
A ultrasonic generation system
Ultrasound transducer is generally used to produce ultrasound from
any other energy
The common transducer used are
 Magnetostrictive
 Piezoelectric
Contd..

15. 1. Normally, the charges in a piezoelectric crystal are exactly
balanced, even if they're not symmetrically arranged.
2. The effects of the charges exactly cancel out, leaving no net
charge on the crystal faces.
3. If you squeeze the crystal you force the charges out of balance.
4. Now the effects of the charges (their dipole moments) no longer
cancel one another out and net positive and negative charges
appear on opposite crystal faces.
5. By squeezing the crystal, you've produced a voltage across its
opposite faces—and that's piezoelectricity!
piezoelectricity!

16. 16
Ac power
supply
Piezoelectric material
Ultrasound
Contd..
 Works according to reverse piezoelectr
effect
 Piezoelectric material have the
ability to convert vibrations into
electric energy
 When it reversed the
electrical energy is
converted into ultra sound
 Produces ultrasound of specific
frequency
 Shape determines the pulse direction
and shape
 Eg : quartz, tourmaline, rochlle salts
Piezoelectric transducers

17. Sonication horn
• Probes have threaded ends and attach to the
converter.
• During operation, the probe’s tip longitudinally
expands and contracts

18. 18
Heat supply
Hot air is blown through electrical heater
Hot air

19. 19Treatment chamber
a) Product is placed between two vibrating plate for direct sonication
b) Product is placed in any medium( water air etc.…)

20. 20
terminologies
• Sonication amplitude: The amplitude of the horn's vibrating surface is defined
as the distance between its position in the horn's fully extended and fully contracted
states, measured in microns (µm).
• Power: it is the measure of energy per unit of time that is conveyed from the generator
to the sonicated liquid. It is measured in watts (W) or kilowatts (KW)
• Frequency: measured in Hertz is the number of occurrences of a repeating event per
second.
• power intensity: refers to the amount of power delivered to the sonicated liquid
via a unit (cm^2) of the horn's radiating area.

21. 21 Contd..
• Power density : is the amount of delivered power per unit of sonicated
liquid volume. Common units: Watts per centimeter cubed (W/cm^3) or
kilowatts per liter (kW/L).
• Processing rate: describes how much product can be made per unit of time
with a given ultrasonic processor.

22. 22
Principle of sonication
 When ultrasound is passed through any medium it generates cycles of
compression and refraction by the mechanical vibrations
 The phenomenon called cavitation occurs in the liquid
U s
5000 k

23. 23 Contd..
The cavitation phenomena
Formation(nucleation)
Rapid growth(expansion)
compression
Violent collapse
 Upon violent collapse each bubbles act as
hotspot with temperature of 5000 k and
pressure of 500atm
 Cools fast in 109k/s

24. 24 Contd..
Other factors that is increasing the drying efficiency by sonication
Pressure between gas and liquid phase is variated
Reduces diffusion layer
Micro steaming
Increases mass
transfer and
diffusion rate
Acoustic wave produced will increase drying rate at stable air velocity
a)
b)
Micro steaming enables natural channels for moisture migrationc)

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Effect on quality
i. Till reported as no effect on quality attributes
ii. Colour change Is comparable
iii. Results of rehydration show only minor changes in biometric
characteristics

26. FRESH APPLE(TEM)
DRIED AT 30°c
DRIED AT 30°c
ASSISTED WITH
ULTRA SOUND
26 Contd..

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ADVANTAGES
1. Not effecting nutritional quality
2. Reduces energy consumption
3. Simple equipment
4. Reduces drying time
5. Safe and easy to operate

28. 28
Disadvantages
1. Still evolving technique
2. Not approved by regulatory agents
3. Noisy parts may make irritation to operator

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Case study 1
Title: Drying characteristics of ultrasound assisted hot air drying of Flos Lonicerae
Authors: Yunhong Liu & Yue Sun & Shuai Miao & Fang Li &Denglin Luo
Journal: journal of food science and technology ,year 2015, vol 52(8), page 4955–4964.
Objectives
 Investigation of Ultrasound assisted hot air drying of Flos Lonicerae
 Analysis of the effects of drying parameters such as ultrasonic radiation distance,
ultrasonic power and drying temperature on drying char-acteristics

30. 30 Contd..
Materials and method
o Fresh Flos Lonicerae (honey suchle flower )
initial moisture content of the samples ranged from 4.62~4.78
(g/g dry base).

31. 31 Contd..
The experimental setup(dryer)
Blower
Electric heater
Material tray
Ultrasonic generator
ultrasonic transducer
Vibration plate
Temperature velocity detector

32. 32The experimental methods
× Sample is loaded into drying chamber
× Dried under different conditions as follows and weight is taken
Temperature
(°c)
ultrasonic
radiation
distances
(cm)
ultrasound
powers(W)
40 10 0
50 20 40
60 30 80
70 120
160
Contd..

33. 33
• The moisture content is found by following equation
𝑀 =
𝑤 − 𝑤 𝑑
𝑤 𝑑
M moisture content
W total weight of sample
𝑤 𝑑 weight of dry matter
• The drying rate was calculated by following equation
DR=
𝑚 𝑡− 𝑚 𝑡+∆𝑡
𝑚 𝑡
where Mt and Mt+△t are moisture contents at drying times t and t+△t, respectively (g/g, dry
base).
Contd..

34. RESULTS AND DISCUSSION
34

35. 35Drying characteristics
30 CM
The air velocity, drying temperature and ultra-sonic power were
set as 1 m/s, 50 °C and 160 W, respectively

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 The drying time of direct HAD without ultrasound assistance was 340 min.
 With the application of ultrasound, the drying time was as short as 200 min
 the reduction ratio was 41.2 %.
 So it is clear that the water removal rate is higher when HAD is assisted by
ultrasound.
 shortening ultrasonic radiation dis-tance is beneficial to improve both
ultrasonic energy efficien-cy and drying rate.
Contd..

37. 37
The air velocity, drying temperature were set as 1 m/s, 50 °C
respectively
Contd..

38. 38
The applied ultrasonic power was set as 80 W.
Contd..

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• drying times with ultrasound assistance were obviously shorter that of HAD at same
temperature.
• So it could be concluded that not only the temperature, but also ultrasound
application affect drying kinetics.
Contd..

40. 40
Case study 2
Title: Ultrasound-Assisted Air-Drying of Apple (Malus domestica L.).
Authors: Fabiano A. N. Fernandes & Sueli Rodrigues & Juan A. Cárcel & José V. García-Pérez
Journal: Food and Bioprocess Technology,year 2015, vol 8(7), 1503–1511.
Objectives
 influence of ultrasonic-assisted air-drying on the dehydration of apple (Malus domestica L. var
Royal Gala)

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Materials and method
× The apple were dried in an ultrasound-assisted convective drier
× Air-drying experiments with apple samples were carried out at four different air
velocities (1, 2, 3, and 5 m/s)
× Two temperatures(45and60°C).
× Drying was carried out with and without ultrasound applied in the air-drying. The
ultrasound transducer was set at 75 W and 21 kHz
× The amount of Vit A,B1,B2,B3,B5,B6,E present in apple juice were collected and
analysed spectrophotometrically at 215 to315 nm of uv-c

42. 42
BLOWER
US GENERATING SYSTEM
ELECTRICAL HEATER
Contd..

43. Results and discussion
43

44. 44 Contd..

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48. 48
• as observed comparing the effective Drying time for each condition
at 45 °C and 1 m/s of air velocity, the effective time reduction was 35 %
lower
• while at 60 °C and 5 m/s, both drying time were similar for ultrasonic and non
ultrasonic-assisted drying experiments.
• At low drying temperatures, the additional energy provided by ultrasound is
significant but its relevance is reduced whenthe drying temperature increases
• the high values of air velocity produce turbulence that can disrupt the ultrasonic
field

49. 49
In overall
 What is ultrasound assisted drying
 What its principle and components
 What is its importance

50. 50
References
• Cárcel, J.A., Benedito, J., Rosselló, C. and Mulet, A., 2007. Influence of ultrasound intensity on
mass transfer in apple immersed in a sucrose solution. Journal of food engineering, 78(2), pp.472-
479.
• Szadzińska, J., Łechtańska, J., Kowalski, S.J. and Stasiak, M., 2017. The effect of high power
airborne ultrasound and microwaves on convective drying effectiveness and quality of green
pepper. Ultrasonics sonochemistry, 34, pp.531-539.
• Schössler, K., Jäger, H. and Knorr, D., 2012. Effect of continuous and intermittent ultrasound on
drying time and effective diffusivity during convective drying of apple and red bell
pepper. Journal of Food Engineering, 108(1), pp.103-110.
• Rodríguez, Ó., Santacatalina, J.V., Simal, S., Garcia-Perez, J.V., Femenia, A. and Rosselló, C., 2014.
Influence of power ultrasound application on drying kinetics of apple and its antioxidant and
microstructural properties. Journal of Food Engineering, 129, pp.21-29.
Contd..

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• Kowalski, S.J. and Pawłowski, A., 2015. Intensification of apple drying due to ultrasound
enhancement. Journal of Food Engineering, 156, pp.1-9.
• Denglin, L., Juan, L., Yunhong, L. and Guangyue, R., 2015. Drying characteristics and mathematical
model of ultrasound assisted hot-air drying of carrots. International Journal of Agricultural and Biological
Engineering, 8(4), pp.124-132.
• Fernandes, F.A., Rodrigues, S., Cárcel, J.A. and García-Pérez, J.V., 2015. Ultrasound-assisted air-drying of
apple (Malus domestica L.) and its effects on the vitamin of the dried product. Food and Bioprocess
Technology, 8(7), pp.1503-1511.
• Leong, T., Ashokkumar, M. and Kentish, S., 2011. The fundamentals of power ultrasound-A review.

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