4 Ultrasound Technology

8/22/2019 4 Ultrasound Technology

1/11V.B. Alvarez/Ultrasound/10-2007

Application of UltrasoundTechnology in Foods

Valente B. AlvarezFood Industries Center

Department of Food Science and

Technology

V.B. Alvarez/Ultrasound/10-2007

Application of UltrasoundTechnology in Foods

Contents

Ultrasound principle

Ultrasound applications

Microbial inactivation

Applications




Basic Principle (Knorr, 2004, Piyasena et.al., 2003)

When sound energy passes to the mediumresulting in a continuous wave-type motion,longitudinal waves are generated

The motion creates alternative compressionand rarefaction of the medium particles

Depending on the frequency and amplitude,

a number of physical, chemical andbiochemical effects are observed.


Ultrasound of interest

20 kHz (human range) to 100sof MHz

Able to penetrate solid andliquid materials

Used widely in medicine (fetusexamination), engineering(inspection of materials), andagriculture (measurement ofbackfat on livestock)




Energy of sound field

Characterized by

Sound power (W)

Sound intensity (W/m2)

Sound energy density (Ws/m3)

Classified as

Lower energy

Low frequency low amplitude

High frequency low amplitude

Higher energy

Low frequency high amplitude


How ultrasound can benefit foodindustries? (McClements, 1995)

New analytical techniques to study complexfood materials and to monitor properties offoods during processing

Relatively inexpensive ultrasonicinstrumentation

Fully automated, rapid and precise

measurements, non-destructive, non-invasiveand online applications




Effects during Food Processing

Generation of heat

Cavitation (implosion of gas bubbles)

Caused by a rapid change of heating to5500C and pressure increase to 50 MPa(Leighton, 1998)


Low energy ultrasoundapplications

Intensities lower than 1 W/cm2 andfrequencies higher than 100 kHz

Used for non-invasive detection (processcontrol) and for characterizing

physicochemical properties of foodmaterials (product control)




Low energy ultrasound

applications (contd..)

Stimulation of activity of living cells

Surface cleaning of foods

Effects on enzymes

Ultrasonically assisted extraction,crystallization, emulsification, filtration,

drying and freezing as well astenderization of meat


High energy ultrasoundapplications

Intensities higher than 1 W/cm2 andfrequencies between 20 and 100 kHz

Applications include, degassing of liquidfoods, induction of oxidation/reductionreactions, extraction of enzymes andproteins, induction of nucleation for

crystallization Inactivation of heat resistant enzymes

Inactivation of microorganisms



V.B. Alvarez/Ultrasound/10-2007(Povey, 1998)


Transmission electronmicrograph showing aprostate cancer cellimmediately after exposureto ultrasound. Image hasbeen color enhanced toshow to the spot where thecell membrane has beenremoved.

Image courtesy of RobynSchlicher, Robert Apkarianand Mark Baran




Sanitation of food processing

equipment-fouling (Withers, 1996)

Ultrasonic sensor for measurement of fouling inpipelines

Pulse-echo technique - detect fouling films as thin as0.1mm

Transmission technique-limit of 0.5mm

Useful in tube-in-tube heat exchangers and other

tubular systems



Power ultrasound high power low frequency (20-100kHz)

Causes cavitation inactivates microbes

Hot zones kill some bacteria, but they are localized

Used in conjunction with pressure (manosonication), heat

(thermosonication), or both (manothermosonication)





More effective when used incombination with otherdecontamination techniques, such asextremes of pH or chlorination

Patents exist on ultrasonic bacterialinactivation systems


Microbial inactivation studies

Ultrasound not only increases thesusceptibility of microorganisms to heattreatment, but also increased the rate atwhich solid food particles heat.

Research done on Listeria monocytogenes,strains ofSalmonellaspp., Escherichia coli,

Staphylococcus aureus, Bacillus subtilisandsome other microorganisms Mamothermosonication increases the lethality

of heat treatment by @10-fold againstBacillus subtilis(Knorr et.al.,2002).




Factors affecting microbial

inactivation (USDA,2000)

Amplitude of ultrasonic waves

Exposure/contact time

Volume of food being processed

Composition of the food

Treatment temperature


Advantages of ultrasound overheat pasteurization

Minimized flavor loss, especially insweet juices

Greater homogeneity

Significant energy savings




Specific advantages

Measurements are rapid,nondestructive, precise, fully automated

Suitable for online measurements

Can be used to analyze optically opaqueand delicate samples

No need for extensive samplepreparation


Food industries of interest

Bakery and snack foods

Candy and confectionery

Cheese

Fish

Prepared meatsVegetable

Health bars


11/11V B Alvarez/Ultrasound/10 2007


Application of Ultrasound

Technology in Foods

Summary

Ultrasound principle

Ultrasound applications


Applications


References

http://www.hielscher.com/ultrasonics/cut.htm

http://www.campden.co.uk/whatsnew/NEWS21.HTM

Knorr,D, B.I.O.Ade-Omowaye and V.Heinz. 2002. Nutritional improvement of plantfoods by non-thermal processing. Proceedings of the Nutrition Society. 61, 311-318.

Knorr,D, M.Zenker, V.Heinz and D.Lee. 2004. Applications and potential of ultrasonicsin food processing. Trends in Food Science & Technology. 15, 261-266.

McClements, D.J. 1995. Advances in the application of ultrasound in food analysis andprocessing. Trends in Food Science & Technology. 6, 293-299.

Sala,F.J., J.Burgos, S.Condon, P.Lopez and J.Raso. 1995. Effect of heat and ultrasoundon microorganisms and enzymes. In New Methods of Food Preservation, pp.177-203[GW Gould Editor]. Blackie Academic and Professional Publisher, London.

USDA, 2000. U.S.Food and Drug Administration Report. Kinetics of MicrobialInactivation for Alternative Food Processing Technologies: Ultrasound. Published June2,2000. Available at http://www.vm.cfsan.fda.gov/~comm/ift-us.html

Withers, P.M. 1996. Ultrasonic, acoustic and optical techniques for the non-invasivedetection of fouling in food processing equipment. Trends in Food Science &Technology. 7, 293-298.

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