This document discusses traditional methods of food preservation, including controlling pH and water activity, heat treatment, freezing, fermentation, using natural antimicrobials and antioxidants, nitrites, and drying. It provides details on each method such as how pH is controlled through organic acids, how water activity relates to microbial growth, examples of heat treatment processes like pasteurization, how freezing prevents spoilage, the classification and principles of fermentation, common natural antimicrobials from plants and microorganisms, how antioxidants prevent rancidity, the use of nitrites in curing meat, and classifications of drying processes.

1. OBT554
UNIT 1
Traditional Methods of Preservation
Dr K.Geetha
Associate Professor, Dept of Biotechnology,
Kamaraj College of Engg &Tech, Madurai

4. HazardAnalysis and Critical Control Point
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5. Traditional preservation technologies
 The control of pH
 The control of water activity
 Heat treatment
 Freezing
 Fermentation
 Natural Antimicrobials
 Antioxidants
 Nitrites
 Drying

6. The control of pH
 The pH is the negative logarithm of the hydrogen ion activity.
 pH is an important factor affecting growth of micro-
organisms in food because it affects
(i) microbial energy metabolism
(ii) microbial enzyme activity and
(iii) stability of cellular macromolecules like carbohydrates
 pH also affects the sensory properties of many foodstuffs like
taste.
 For example, lowering the pH causes coagulation of milk
casein and meat proteins.

7.  pH can be controlled by the choice of raw material (e.g., plant
varieties, animal tissues) and by the addition or in situ formation
of acidic or alkaline low molecular weight compounds.
 Hence, organic acids are most important in food preservation.

8. Control of Water Activity
 Water activity: Water activity or aw is the partial vapor pressure of
water in a substance divided by the standard state partial vapor pressure
of water.
 Pure distilled water has a water activity of exactly one. As temperature
increases, aw typically increases, except in some products with
crystalline salt or sugar.
 Higher aw substances tend to support
more microorganisms. Bacteria usually require at least 0.91, and fungi at
least 0.7.

9. Water migrates from areas of high aw to areas of low aw.

11. Heat treatment
 Food preservation by application of heat is achieved by the inactivation
of viable micro-organisms.
 Clostridium botulinum is considered to be the most heat resistant
food poisoning organism.
 Food industry cookers – typically 121°C requires an atmosphere of
about 1bar above atmospheric pressure (1bg).
 Pasteurisation - the partial sterilization of packaged and non-packaged
foods (such as milk and fruit juice) treated with mild heat, usually less
than 100 °C (212 °F), to eliminate pathogens and extend shelf life.

12. Food industry cookers
Milk Pasteurisation
RETORT SYSTEM

13. Freezing
 Provides extended shelf life
 Employed for long-term preservation.
 Freezing changes the physical state of a substance by changing
water into ice when energy is removed in the form of cooling
below freezing temperature.
 The maximum recommended storage temperature at which
microbiological Spoilage ceases is registered between 9°C and
12°C.
 Microorganisms commonly encountered in frozen Food include
Pseudomonas,Achromobacter,Flavobacter,Micrococcus,Lactobacillus etc.

15. Fermentation
 Definition: 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.

16. Principle of Fermentation
1. Minimize the level of microbial contamination onto the food
2. Inhibit the growth of the contaminating microflora
3. Kill the contaminating microorganisms

19. Classification of Fermented Foods
 Campbell-Platt (1987) identified seven groups for
classification, namely,
(1) beverages,
(2) cereal products,
(3) dairy products,
(4) fish products,
(5) fruit and vegetable products,
(6) legumes, and
(7) meat products

20. Natural Antimicrobials
 Definition: Chemical compounds having pharmacological and
biological activity and produced by living organisms.
 Secondary metabolites possessing antimicrobial activity are called the
natural antimicrobials and could be extracted from different
sources like plants (fruits, vegetables, seeds, herb, and spices), animals
(eggs, milk, and tissues), and microorganisms (fungi and bacteria)
 Commonly used: Secondary metabolites like terpenoid or phenolic
biosynthetic origin; hydrolytic enzymes (glucanases and chitinases) and
proteins

22. Examples
 Phytoalexins - broad-spectrum antibiotics, generally active against
phytopathogenic fungi.
 Organic Acids - Citric, succinic, malic, and tartaric acids found in fruits.
 Phenolic Compounds - flavons, flavonols, and tannins.
 Essential Oils and Their Components - derived from spices and herbs
eg: cinnamaldehyde from cinnamon, and eugenol from clove.
 Bacteriocins - Produced by Lactic Acid Bacteria

23. Antioxidants
 Rancidity: degradation due to changes in lipid constituents is
considered the main feature of rancidification.

24.  Antioxidants: a substance that inhibits oxidation, especially
one used to counteract the deterioration of stored food products.

26. Lemon Juice as Antioxidant

27. Nitrites
 A salt or ester of nitrous acid, containing the anion NO2
− or the group —
NO2.
 Nitrites are white-to-pale-yellow hygroscopic crystals.
 Examples: Sodium nitrite (NaNO2), Potassium nitrite (KNO2).
 Sodium nitrite plays an important role in inhibiting the growth and toxin
production of Clostridium botulinum in cured products.
 Application: Nitrites and nitrates inhibit dairy microorganisms by their
effect on the activity of a number of oxido-reduction enzymes, preventing
natural ripening of milk and undesirable microflora forming.

29. Drying
 Drying reduces the water activity, thus preserving foods by
avoiding microbial growth and deteriorative chemical reactions.
 Heating air using either an electric heater or flue gas is the
conventional heating method used for drying foods.
 Microwave, infrared, radio frequency, refractance
window, and dielectric heating use electromagnetic
wavelength spectrum as a form of energy, which interacts with
the materials, thus generating heat and increasing the drying rate.

30. Drying processes
 Can be broadly classified, based on the water-removing
method applied, as
(a) thermal drying,
(b) osmotic dehydration, and
(c) mechanical dewatering

31. Dried fish Dried chilli
Dried safron flowers Dried tamarind

32. ROOT CELLAR for Storage
1950's Root Cellar

33. "Home Demonstration of Canning, Mrs. Jane McKimmon,
ca. 1908-1917 "

34. CanningTomatoes

37. SUMMARY
 The control of pH
 The control of water activity
 Heat treatment
 Freezing
 Fermentation
 Natural Antimicrobials
 Antioxidants
 Nitrites
 Drying

38. Thank you