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Cutting of food products by ultrasound

Identification

Key words Ultrasound, cutting, ultrasonic separation, ultrasonic amplitude, friction force
Latest version 2012/04/16
Completed by FRIP, DIL

How does it work?

Primary objective Ultrasound application for cutting enhances the cut surface quality, lowers the energy for cutting and improves the cut exactness.
Working principle Ultrasound is a cyclic sound pressure with a frequency greater than the upper limit of human hearing which can be used to induce mechanical vibrations [1].

Generally, an ultrasonic cutting system consists of a generator, a transducer, an amplifier and a sonotrode (blade) which is capable of applying frequencies in the low ultrasonic frequency range of 20-100 kHz [2]. The induced oscillation at the cutting edge of the sonotrode with defined vibration amplitude results in faster and more efficient cutting due to less mechanical cutting force needed in comparison to other conventional methods such as laser cutters and water jet cutters. The cutting blade is made of titanium which is quite inert towards foods and enduring materials. In fact, the vibration reduces the friction resistance at the cutting surface. Cutting with devices excited by ultrasound is a promising alternative to conventional cutting when the materials contain particles which differ in stiffness and elasticity from the surrounding bulk or when they consist of layers which exhibit largely differing mechanical properties. There are many benefits using ultrasound in food processing operations [5, 6, 7, 8].

Images
Additional effects
  • Absorption heating that can affect negatively to soft food stuff (slight softening on the edges being cut).
  • Cavitation that reduces the energy and time for cutting (cavitation is a high intensity flow of fluid at the local point of cutting, connected with pressure decrease ).
  • Sonochemical effects [1] which enables easier cutting by ultrasound (these effects cause high efficient chemical reactions)
  • Temperature increase, off-flavour generation
Important process parameters blade shape, geometry, frequency, vibration amplitude, time and size of the contact area [3] , direction of oscillation related to cutting direction
Important product parameters composition, structure (porous, non-porous), food state (solid or semisolid), shape

What can it be used for?

Products Soft and hard cheese, snack bars, health bars, ice cream, bakery, frozen cakes and pies, frozen fish, prepared meats, pizza, gum and candy, fresh and frozen vegetables, bones.
Operations Separation, cutting
Solutions for short comings
  • Improved cutting quality and precision (cutting force increase by increasing cutting velocity).
  • Reduced cutting forces in a continuous cutting operation
  • Avoids wetting of cut material (compared to water jet cutting)
  • Avoids noises and smoke and air contamination (compared to laser cutting)
  • Increases the blade’s life
  • Avoids adhering food products to the blade which makes cleaning more convenient

What can it NOT be used for?

Products
  • Products with high content of fat and semi-liquid products
  • Products that can be easily cut.
  • Products with irregular shape.
  • Products with many particles of solid nature.
Operations Not advisable for high fat content products and semi-liquid products.
Other limitations The tendency to burn at the cut surface during ultrasonic cutting in case of poor temperature control at the blade [2].

Additionally, acoustic cavitation occurring in the surroundings of a cutting sonotrode while cutting a high fat content material may initiate chemical reactions such as hydroperoxide formation, which during long-term storage could result in quality defect due to inducing radical chain reactions [4]. Blunting of the blade after about 30.000 hours of operation.

Risks or hazards Temperature increase in cut surface – overheating, protection of users from ultrasound.

Implementation

Maturity Commercially available with the frequency of 20 to 60 kHz.
Modularity /Implementation Easy implementation into current production lines. Ultrasound can be easily set for cutting methods.
Consumer aspects Consumers perceive this method quite fast, clean and convenient.
Legal aspects Protection of humans against ultrasound is necessary.
Environmental aspects
  • Less energy required in comparison with the other methods.
  • Product waste is reduced.

Further Information

Institutes TU Dresden, Université d'Avignon et des Pays de Vaucluse, University of Kiel, University of Glasgow
Companies Newtech, Sonowave, Decoup
References [1] Schneider Y., Zahn S., Rohm H., 2008. Power requirements of the high-frequency generator in ultrasonic cutting foods, Journal of Food Engineering 86, 61-67.

[2] Lucas M., Cardoni A., MacBeath A., 2005. Temperature effects in ultrasonic cutting of natural materials, CIRP Annals - Manufacturing Technology, Volume 54, Issue 1, 195-198.

[3] Lucas M., Petzing J.N., Cardoni A.., Smith L. J., 2001. Design and characterization of ultrasonic tools. CRIP Annals – Manufacturing technology, V 50, Issue1, 149-152.

[4]. Schneider Y., Zahn S., Hofmann J., Wecks M., Rohm H., 2005. Acoustic cavitation induced by ultrasonic cutting devices: A preliminary study. Ultrasonics sonochemistry, 13, 117-120.

[5] Chemat, F., Zill-E-Huma, Khan, M.K., 2011. Applications of ultrasound in food technology: Processing, preservation and extraction. Ultrasonics Sonochemistry, 18 (4), pp. 813-835.

[6] Bhaskaracharya, R.K., Kentish, S., 2009. Ashokkumar, M. , Selected applications of ultrasonics in food processing. Food Engineering Reviews, 1 (1), pp. 31-49.

[7] Anonymous, Ultrasonics in food processing, 2007. Food Technology, 61 (3), pp. 67-69.

[8] Knorr, D., Zenker, M., Heinz, V., Lee, D.-U., 2004. Applications and potential of ultrasonics in food processing.. Trends in Food Science and Technology, 15 (5), pp. 261-266.

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Created by Milan123 on 16 April 2012, at 10:41