Ultrasound processing in dairy industry

Ultrasound Processing in Dairy Industry
4/26/2018 ADVANCED DAIRY PROCESSING 1
Presented By:
Parth Hirpara
Dairy Technology Dept.

What is Ultrasound???
Energy driven from sound waves.
Frequency of sound waves above human hearing range (20 Hz to 20 KHz) i.e., above 20 KHz.

Physics of Ultrasound
Ultrasound can propagate in gases, liquids and solids.
This longitudinal pressure waves transmitted through a medium.
The majority of food applications ranging in frequency between 20 and 40kHz.
(Mason, 1998)
Ultrasound when propagate through a system induces a series of compression and rarefaction
cycles that generate acoustic cavitation.
(Ciawi et al., 2006)

Type of Ultrasound waves
Applications of ultrasound in the food industry are classified into low-intensity and high-
intensity ultrasound.
The low-intensity (low power) ultrasound is known as a non-destructive tool where it uses
typically smaller power levels (<1 W/cm²) and frequencies higher than 100 kHz (or 1MHz).
High-intensity (high power) ultrasound uses intensities higher than 10 W/cm² at frequencies
between 20 and 100 kHz, that are disruptive and affects on physical, mechanical and
chemical/biochemical properties of foods .
(Jha, 2010; Tiwari and
Mason 2012)
High power
Low power

Principle
At higher intensity it generates a series of compression and rarefaction cycles that generate acoustic
cavitation.
In an acoustic field, microbubbles in solution may undergo growth by rectified diffusion and by
bubble–bubble coalescence.
(Ciawi et al., 2006)
Cavitation bubbles reach a maximum size and violently collapse, generating mechanical, physical and
chemical effects, such as shockwave formation and turbulent motion, powerful enough to break large
aggregates apart.
(Ashokkumar et al., 2009b)
At the point of bubble collapse, high localized temperatures are generated and these may cause
chemical changes, primarily by generating radicals.
(Ashokkumar and Mason, 2007)

History
The discovery of Ultrasound came with Pierre Curie in 1880.
The inactivation of microorganisms by Ultrasonic Waves (UW) was reported in the early 1930s.
(Pagan et al., 1999)
Sanz et al. (1985) studied the lethal effects of ultrasound on spore forming bacteria.
In 1987, combination of heat and high power UW (>20 kHz) was first explored by Ordondez &
coworkers and the term of thermoultrasonication was used.
The Manothermosonication (MTS), which is the combination of heat, pressure and ultrasound,
has been coined for the combined treatments.
(Ordondez et al., 1987)

Ultrasonic Equipments
1. Ultrasound bath

2. Ultrasound Probe

Application of US in Dairy
Application Mechanism/Details Advantages Authors
Microbial Inactivation Cavitation Phenomena;
Frequencies about 20 KHz,
High power
 Minor variation in
physicochemical and
nutritional properties.
 Higher shelf-life.
 Less energy
consumption.
Law et al., 2003; Bermúdez-
Aguirre & Barbosa-Cánovas,
2008; Cameron et al., 2008;
Sengül et al., 2011; Arroyo et
al., 2011.
Homogenization Using cavitation;
Frequencies from 20 KHz to
100 kHz, High power
 Reducing process
temperature and time.
Wu et al., 2000; Riener et al.,
2009.
Creaming Frequencies between 20 and
100 kHz
 Promoting quality and
security.
Juliano et al., 2012
Cutting Conversion of the
mechanical vibration energy
into thermal energy,
frequency 40 kHz
 Rapid process.
 Reducing the process of
the process.
 Independent with
temperature.
Arnold et al., 2009; Schneider
et al., 2009.
Dissolution Power ultrasound  Decrease the time of
process.
Yebra et al., 2004

Contd…
Viscosity decreasing Almost at 20 kHz and high
Powers
 Controlling products
viscosity.
 Preventing the ‘age
thickening’.
Zisu et al., 2010; Zisu et al.,
2013.
Fermentation Low frequencies and high
intensity ultrasound
 Accelerate the process.
 Better quality product.
 Less undesirable
flavours.
Nguyen et al., 2009; Nguyen et
al., 2012.
Filtration/Fouling prevention Based on cavitation
phenomenon; 20 kHz
frequency, low power
 Higher permeate flux.
 Need of lower pressures.
 More money saving.
Muthukumaran et al., 2005;
Muthukumaran et al., 2008;
Mirzaie & Mohammadi, 2012.
Monitoring/Quality Control Analysing of signals, high
frequencies and low powers
 Non-invasive & non-
destructive diagnosis.
 Fast & in-line test.
 Non-contact & without
manipulation.
Richard et al., 2012; Gülseren
et al., 2010; Lopez et al., 2009;
Pallav et al., 2009; Leemans et
al., 2009; Elvira et al., 2006;
Yucel & Coupland 2010.
Extraction Based on collapsing
microbubbles
 Higher enrichment.
 Better quality.
Yan et al., 2011; Ashokkumar et
al., 2008.

Microbial Inactivation
Intense power and long contact times are required to inactivate microorganisms at ambient
conditions in real food systems when ultrasound is applied alone.
(Cameron et al., 2009)
Recent improvements recognize the combination of more than one technique in combination
with ultrasound such as heat (thermosonication, TS), pressure (manosonication, MS), or heat
and pressure (manothermosonication, MTS) and provide enhanced benefits for microbial
inactivation.
The effectiveness of microbial inactivation by these methods is dependent on the amplitude of
the ultrasonic waves, exposure/contact time, volume of product being processed, the
composition of the food including the types and initial number of the microbes present, and
their aggregate state, viscosity of the medium, and the treatment conditions.
(Chandrapala, 2016)

Mechanism of Microbes Inactivation
The physical forces generated by acoustic cavitation.
The asymmetric collapse of a cavitation bubble leads to a liquid jet rushing through the center of the
collapsing bubble.
Microorganisms that have hydrophobic surfaces will promote the collapse of cavitation bubbles on the
surface and lead to severe damage of the cell wall.
Microstreaming effects can lead to the erosion of cell walls, again resulting in inactivation of
the microorganisms.
The effects of localized heating, free radical production causing DNA damage which in turn
causes thinning of cell membranes are also crucial in the inactivation.
(Bermudez-Aguirre et al., 2011).
The thickness and softness of the bacteria capsules as one of the most important parameters
when using high-power ultrasound for the deactivation microbes.
(Gao et al., 2014)

Process Parameters
Ultrasound treatment combined with mild heat (57oC) for 18 min resulted in a 5-log reduction
of L. monocytogenes in milk and a 5-log reduction in the total aerobic bacteria in raw milk.
(D’Amico et al., 2006)
Use of ultrasound at 124 μm amplitude was effective without heat against spoilage
microorganisms and potential pathogens including E. coli (100% reduction in 10min),
Pseudomonas fluorescens (100% reduction in 6min) and L. monocytogenes (99% reduction in
10min) even when inoculum loads of five times higher than permitted were present in raw and
pasteurized milk.
(Cameron et al., 2009)
Manosonication (MS) treatment at 500 kPa and 117 μm of amplitude for 12 min inactivated ~
99 % of the B. subtilis spore population. MS treatment (20 kHz, 300 kPa, 70oC, 12 min) at 90 μm
amplitude inactivated 75 % of the B. subtilis spore population.
(Raso et al., 1998)

Enzymatic Inactivation
Thermo-resistant enzymes in milk such as lipases and proteases that withstand UHT treatment
can reduce the quality and shelf- life of heat-treated milk and other dairy products.
The effectiveness of ultrasound for control of enzymatic activity is strongly influenced by many
factors such as enzyme concentration, temperature, pH and composition of the medium
including treatment volume and processing variables such as sonotrode type and geometry,
frequency, and acoustic energy density.
(Raso et al., 1998)
Enzyme inactivation generally increases with increasing US power, frequency, exposure time,
amplitude, temperature, and pressure but decreases as volume of sample increases.
(Sala et al., 1995)

Mechanism of Enzyme Inactivation
Defragmentation of the enzyme or formation into aggregates.
(Mawson et al., 2011)
Formation of enzymes fragment into monomeric subunits during ultrasonication primarily attributed
to cavitation.
The extreme agitation created by microstreaming could disrupt van der Waals interactions and
hydrogen bonds in the polypeptide, causing protein denaturation.
(Tian et al., 2004)
Denaturation of protein (enzyme) due to the intense pressures, temperatures, and shear forces
generated by the ultrasonic waves.
Free radical-mediated deactivation.
(Lopez et al., 1994)
 Disruption in hydrophobic interactions and hydrogen bonds.
(Tian et al., 2004)

Process Parameters
Thermos labile enzymes were more sensitive to ultrasonication than heat-resistant enzymes.
 Such enzymes have been efficiently inactivated at tenfold the rate of thermal treatment alone,
by MTS (20 kHz, 145 μm amplitude, and 650 kPa for protease, 117 μm amplitude and 450 kPa
for lipase, 109–140oC) treatment.
(Vercet et al., 1997)
Inactivation effects were reported when sonication was carried out above 61oC.
Similarly, TS (150 W, 20 kHz, 120 μm amplitude, 30–75.5oC, 40.2–102.3 s) was reported to be
more effective at inactivating milk enzymes (alkaline phosphatase, lactoperoxidase, and γ-
glutamyl transpeptidase) than heat alone.

Creaming of Milk
Milk fat separation is a key process in producing some dairy products such as butter, cheese, yogurt,
and skim milk.
Use of high frequencies (>400 kHz) than those associated with conventional food processing to
destabilize fat and assist creaming.
(Juliano et al., 2012)
No disturbance on the structure of fat globules is considered as an important aspect.
(Leong et al., 2013)
Use of high-frequency ultrasound (1 and 2 MHz) to separate the small fat globules distributed in milk
(~4 μm diameter).
It was demonstrated that operation in the temperature range of around 25–40oC is more optimal to
the fat separation.

Mechanism of Creaming of Milk
When an ultrasonic standing wave is set up in a container, the fat globules distributed in the
milk experience acoustic radiation forces that cause them to migrate specifically to the pressure
antinodes.
The acoustic forces are proportional to (radius)3. Therefore larger particles will be driven to the
node faster than smaller particles.
Concerns when using high-frequency ultrasound for the separation of milk fat:
Potential for oxidation of fat to occur (i.e., lipolysis).
• By promoting radical-driven oxidation processes.
(Juliano et al., 2014)
Potential for alteration of fatty acids within the systems.
High power US were required for hydrolysis of fatty oils by cavitation.
(Pandit & Joshi, 1993)

Homogenization
High-pressure homogenization is the most used technique within the dairy
industry.
Ultrasonic homogenization (400 W, 24 kHz, using a 22 mm probe) of milk at
63oC for 30 min reduced the diameter of the milk fat globules to < 1 μm
compared to the native fat globule size.
(Bermúdez-Aguirre et al., 2008)
Milk fat globule size reduction of up to 82 % during continuous flow, high-
intensity (150 W, 20 kHz) ultrasonication of milk.
(Villamiel & de Jong, 2000)

Mechanism of Homogenization of Milk
Shear forces generated due to cavitation were mainly responsible for
homogenization effects.
(Koh et al., 2014)
The efficiency of sonication toward homogenization is driven by several
important factors such as power, frequency, amplitude, diameter of the
ultrasonic probe, and the composition of the medium being sonicated.

Emulsification
Emulsification in dairy industry has been used through mechanical shaking, colloid mills, high- or
ultrahigh-pressure homogenization, and microfluidization.
Ultrasound-assisted emulsification is influenced by many variables such as wave power, position of
the ultrasonic source with liquid–liquid interface, tip diameter, vessel size, viscosity of the continuous
phase, pre-emulsification, oil–water ratio, surfactant concentration, hydrostatic pressure, presence of
dissolved gases, and exposure time.
(Juang & Lin, 2004)
Only high intensity, low-frequency ultrasound (16–100 kHz) for 5-10min is able to produce
emulsions.
Increasing the amount of gas in the system tends to increase the gas/vapor pressure ratio inside the
bubbles which can cushion the bubble collapse and hence reduce the shock wave intensity and
thereby be less efficiently emulsified.
Ultrasonic emulsification is primarily driven by cavitation, wherein collapse at or near the oil–water
interface bubble causes disruption and mixing of the two phases, resulting in the formation of very
fine emulsions.
(Thompson & Doraiswamy, 1999)

Ultrasound Assisted Filtration
Membrane technology is currently used in the dairy industry for a variety of applications such
as separation of milk components, concentration of protein levels prior to spray drying and
water purification, and treatment of liquid effluents.
One of the critical issues during filtration is the decline in permeate flux as a result of both
concentration polarization and membrane fouling.
The application of ultrasound has proven to be an effective approach to enhance the flux to
improve the cleaning of fouled membranes.
The use of continuous low-frequency (50 kHz) ultrasound is most effective in both the fouling
and cleaning cycles, whereas the application of intermittent high-frequency (1 MHz) ultrasound
is less effective.
(Muthukumaran et al., 2005)

Mechanism
The increase in flux was attributed to an increase in the number of cavitation bubbles in the
system and an increase in acoustic energy in the system by the cavitation bubbles.
The increased permeability observed due to sonication may have been affected by the physical
processes caused by acoustic cavitation which may occur on the surface of the fouled
membrane, on the solid material, and in the vicinity of the pores where the dislodgement of
particles that block the pores can be expected.
At the same time, although higher frequencies may have more cavitation bubbles, the bubbles
are smaller in size and collapse less energetically; thus, they may not be capable of detaching
particles from the cake layer as readily as lower frequencies.
(Muthukumaran et al., 2007)

Advantages of US Processing
1. Rapid processing and high outputs.
2. Low energy consumption.
3. Reduced processing costs.
4. Non-thermal technology.
5. Higher purity.
6. Green technology.

Disadvantages of US Processing
1. High initial investments.
2. Narrow spectrum of application.
3. Skilled labour requirement.
4. Budding technology.

Conclusion
Ultrasound is a promising technology suitable for a range of different applications in the dairy
industry.
In liquid media, the extreme physical forces generated by low-frequency, high-intensity ultrasound
induces acoustic streaming, cavitation, shear, micro-jet, and shockwaves. These physical forces have
been successfully used for the generation of dairy emulsions, functionality improvements of dairy
systems, inactivation of microbes and enzymes, and crystallization of lactose, ice, and fat in dairy
systems, among several other applications.
High frequency, low intensity ultrasound on the other hand has been used to initiate rapid creaming
of fat from milk.
Ultrasound processing has advantages of achieving high product yields, minimizing flavour loss,
increasing homogeneity, reducing energy requirements, reducing processing times, enhancing end-
product quality, reducing chemical and physical hazards, and lowering the environmental impact,
when compared with conventional dairy processes.
The majority of these applications are only proven in the laboratory, some have been successfully
implemented on a larger scale.

Ultrasound processing in dairy industry

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