This document discusses ultrasound and its uses in food processing and preservation. It begins by defining ultrasound and describing how it is generated using a generator, transducer, and application system. It then explains how ultrasound can be used in various food processing applications like extraction, drying, and homogenization. It also discusses how ultrasound preserves foods by inactivating microbes, spores, and enzymes through cavitation. The document concludes by summarizing some common uses of ultrasound in food processing like filtration, freezing, mixing, and degassing.

1. OBT554
Unit 5
Dr K.Geetha
Associate Professor, Dept of
Biotechnology, Kamaraj College of Engg
& Tech, Madurai

3. Introduction
• Ultrasound waves are similar to sound waves but, having a frequency above
16 kHz, cannot be detected by the human ear.
• Ultrasound refers to sound waves, mechanical vibrations, which propagate
through solids, liquids and gases with a frequency greater than the upper
limit of human hearing.
• Use of ultrasound in food processing includes extraction, drying,
crystallization, filtration, defoaming, homogenization and also use of
ultrasound as preservation technique.
• The principle aim of this technology is to reduce the processing time, save
energy and improve the shelf life and quality of food products.

5.  Sound waves can propagate
parallel or perpendicular to
the direction of travel through
a material.
 Parallel waves are known as
longitudinal waves.
 Perpendicular waves are also
known as shear waves.

6. Ultrasound generation
 Ultrasonic wave producing system contains the
generator, transducer and the application system.
• Generator: It produces mechanical energy.
• Transducer: It converts mechanical energy into the
sound energy at ultrasonic frequencies.
 There are 3 types of Transducer:
1) Fluid-driven
2) Magnetostrictive
3) Piezoelectric

7. F

10. Ultrasound in food preservation
 Microbial inactivation
 Spore Inactivation
 Enzyme inactivation

11. Ultrasound in food preservation
 Microbial inactivation mechanism: By Cavitation
phenomena.
 During the cavitation process it changes the pressure
and temperature cause break- down of cell walls,
disruption and thinning of cell membranes and DNA
will be damage.
 The inactivation effect of ultrasound has also been
attributed to the generation of intracellular cavitation and
these mechanical shocks can disrupt cellular structural and
functional components up to the point of cell lysis.

12. Uses of Ultrasound in Food Processing
 Filtration and drying
 Freezing
 Mixing and homogenization
 Defoaming
 Crystallization of fats, sugars etc
 Cutting
 Degassing

13. HIGH PRESSURE
PROCESSING (HPP)

14. HIGH PRESSURE PROCESSING (HPP)
 High Pressure Processing is also known as “High
Hydrostatic Pressure” or “Ultra High Pressure”
processing. Also known as PASCALIZATION.
 HPP uses up to 900MPa to kill many of the
microorganisms found in foods, even at room
temperature without degrading vitamins, flavor and
colour molecules in the process .
 Food packages are loaded onto the vessel and the top is
closed.
 The pressure medium usually water is pumped into the
vessel from the bottom.
 Once the desired pressure is reached, the pumping is
stopped, valves are closed, pressure can be maintained
without further need for energy input.

15. Principle
 The high pressure is applied in an “isostatic” manner
such that all regions of food experience a uniform
pressure, unlike heat processing where temperature
gradients are established.

16.  Non-thermal processing technology (combination
with heat possible) for obtaining microbiologically safe
food products while avoiding undesirable changes in the
sensory, physicochemical, and nutritional properties of
foods.
 First research in 1890s –milk pathogens
 First commercialized in Japan in the early 1990s for
pasteurization of acid foods for chilled storage
 High pressure treated foodstuffs have been marketed in
Japan since 1990, in Europe and the United States since
1996 and Australia since 2001
 Rapid commercialization since 2000

18. Components
 A pressure vessel and its closure
 A pressure generation system
 A temperature control device
 A materials handling system

21. Two methods of processing foods
1.In container processing
 Applied to all solid and liquid foods
 Minimal risk of post processing contamination and Easier
cleaning.
2.Bulk processing
 Simple material handling
 Great flexible in choice of container

24. Applications
 Sterilization of heat sensitive ingredients like
shellfish, flavorings, and vitamins.
 Sterilization of fruits and fruit products, sauces,
pickles, yoghurt, pasteurization of meat and
vegetables, decontamination of high risk products,
high value products

28. Advantages
 Reduced processing time,
 Uniformity of treatment,
 Low energy consumption,
 Elimination of chemical preservatives.

30. Fermentation as
Preservation Tool

31. Fermentation Definition
 A process in which microorganisms change the
sensory (flavor, odor, etc.) and functional properties of
a food to produce an end product that is desirable to
the consumer.

32. Common Fermented Foods

33. Fermentation as a Preservation Method
 To reduce or prevent microbial spoilage of food, four
basic principles can be applied:
1. Minimize the level of microbial contamination onto
the food
2. Inhibit the growth of the contaminating microflora
3. Kill the contaminating microorganisms
4. Remove the contaminating microorganisms
 Fermentations use a combination of the first three
principles.

34. Factors Produced by the Metabolic Activity of
Microorganisms that can Contribute to the Increased
Stability and Safety of Fermented Foods

35. Examples of Microbial Metabolic End Products
Used in Fermented Foods

36. Potential Benefits of Fermented Foods

37. Microorganisms Used in Food Fermentations

38. 1. Lactic Acid Bacteria

39. Lactic Acid Bacteria

40. Genera of Lactic Acid Bacteria Commonly Used
in Food Fermentations

41. Potential Health Benefits from Lactic Acid Bacteria

42. 2. Acetic Acid Bacteria
 The acetic acid bacteria consist of two genera,
Acetobacter and Gluconobacter.
 Acetobacter can eventually oxidize acetic acid to
carbon dioxide and water using Krebs cycle enzymes
referred to as over oxidation.
 This is not the case with Gluconobacter.
 The most desirable action of acetic acid bacteria is in
the production of vinegar.

43. Gluconobacter

44. 3. Yeasts
 Saccharomyces cerevisiae is the most frequently used
and many variants are available.
 Saccharomyces cerevisiae ferments glucose but does
not ferment lactose or starch directly.
 Yeasts are used to produce ethanol, CO2, flavor, and
aroma.

45. Saccharomyces cerevisiae

46. 4. Molds
 The majority of fungal species have filamentous
hyphae and are referred to as molds.
 The Aspergillus species are often responsible for
undesirable changes in foods, although some species
such as A. oryzae are used in fermentations of
soybeans to make miso and soy sauce.
 Mucor and Rhizopus are also used in some traditional
food fermentations.
 Rhizopus oligosporus is considered essential in the
production of tempeh from soybeans.

47. Aspergillus

48. Few Examples
 The sprouting of grains, seeds, and nuts, multiplies the amino acid,
vitamin, and mineral content and antioxidant qualities of the starting
product.
 Fermented beans are easier for our bodies to digest, like the proteins
found in soy beans that are nearly indigestible until fermented.
 Fermented dairy products, like, cheese, yogurt, and kifir, can be
consumed by those not able to digest the raw milk, and aid the digestion
and well-being for those with lactose intolerance and autism.
 Porridge made from grains allowed to ferment increases the
nutritional values so much that it reduces the risk of disease in children.
 The news is full of reports about the health benefits of probotic
supplements (beneficial bacterial cultures for microbial balance in the
body) fighting cancer and other diseases. Ex: Yakult
 Vinegar is used to leach out certain flavors and compounds from plant
materials to make healthy and tasty additions to our meals