evolution of food microbiology

1. THE EVOLUTION OF FOOD
MICROBIOLOGY

2. SUMMARY

3. WHAT IS MICROBIOLOGY?
Microbiology is the branch of biological
science that deals with microorganisms and
agents (prions, viroid, etc.) that are invisible
to the naked eye
 Importance of microorganisms
 Human and animal diseases
 Soil fertility
 Plant diseases
 Fermentation
 Food spoilages
 Foodborne diseases
© 2020 Dr. Muneeb Khan

4. WHAT IS MICROBIOLOGY?
 Later, microbiology was divided into several
sub-disciplines:
 Medical microbiology
 Mycology
 Soil microbiology
 Plant pathology
 Food microbiology
 Except for a few sterile foods, all foods
contain one or more types of microorganisms
 Some of them have desirable roles in food,
such as in the production of fermented food
 Whereas others cause food spoilage and
foodborne diseases

5. FOOD
MICROBIOLOGY
Study of the microorganisms
that inhabit, create or
contaminate food and cause
food spoilage

6. WHY IS
MICROBIOLOGY
IMPORTANT?
 Food microbiology is important because microbes
and food interact in both positive and negative ways:
 They can make or be the food
 Enhance it
 Spoil it
 Make it unsafe to eat
 Knowing how to bring out the good and prevent the
bad is very important since people need to eat
 To study the role of microorganisms in food and to
control them when necessary, it is important to:
 Isolate them in pure culture
 Indicate their morphological, physiological,
biochemical and genetic characteristics
 Food Microbiology therefore, is important to make
sure our foods are safe for consumption
© 2020 Dr. Muneeb Khan

7. EARLY HAPPENINGS
 7000 BC – Evidence that the
Babylonians manufactured beer
(fermentation)
 3500 BC – Wine appeared
 6000 BC – The first apparent reference
to food spoilage in recorded history
 3000 BC – Egyptians manufactured
cheese (fermentation) and butter
(fermentation, low aw) Fermented foods
such as cheese and sour milk (yogurt)
were safer to eat and resisted spoilage
better than their raw agricultural
counterparts Several cultures also
learned to use salt (low aw) to preserve
meat and other foods around this time

8. EARLY HAPPENINGS
 1000 BC – Romans used snow to
preserve shrimp (low temp)
 Records of smoked and fermented
meats also appeared
 Even though early human cultures
discovered effective ways to preserve
food (fermentation, salt, ice, drying
and smoking), they did not understood
how these practices inhibited food
spoilage or food borne disease
 Their ignorance was compounded by a
belief that living things formed
spontaneously from nonliving matter
(Theory of Spontaneous Generation)

13. FOOD PROCESSING

14. FOOD PROCESSING
 Food processing is the set of techniques used
to change the raw ingredients, by physical or
chemical means, into food, or of food into
other forms, so that they can be consumed by
humans or animals
 Food processing combines raw food
ingredients to produce marketable food
products, that can be easily prepared and
served by the consumer
1. Extend shelf life
2. Maintain sensory properties
3. Maintain or improve nutritive properties
4. Ensure safety
5. Make more convenient
6. Bottom line: $$ (economic value)

15. FOOD PROCESSING
From Farm To Table
?
Whey protein, a by-
product of cheese
manufacturing, is used in
energy bars and drinks!

16. FOOD PROCESSING METHODS
 Thermal Processing
 Thermal processing is defined as the combination of
temperature and time required to eliminate a desired
number of microorganisms from a food product
 Enhances microbial safety, texture, digestibility,
and detoxification
 Pasteurization and sterilization
 Non-Thermal Processing
 Non-thermal processing involves a wide variety of
processing techniques that do not involve heating the
food necessarily to impart a certain change in the
product

17. TRADITIONAL
FOOD
PROCESSING
METHODS

18. TRADITIONAL FOOD PROCESSING METHODS
Dehydration
 Dehydration, or drying, of foods has long been practiced commercially in the production of
various food products:
 Fruits, vegetables, skim milk, potatoes, soup mixes, and meats
 Foodstuffs may be dried in air, superheated steam, vacuum, or inert gas or by direct
application of heat
 Air is the most generally used drying medium, because:
 It is plentiful and convenient
 Permits gradual drying
 Allowing sufficient control to avoid overheating
 Loss of moisture content produced by drying results in increased concentration of nutrients
 Dehydration techniques are aimed at lowering the water activity (aw) of foods
 Lower the water activity, safer will be the food

19. TRADITIONAL FOOD PROCESSING METHODS
Addition of Sugar
 Fruit jelly and preserve manufacture, an important fruit by-product industry, is based on
the high-solids–high-acid principle, with its moderate heat-treatment requirements
 Fruits that possess excellent qualities but are visually unattractive may be preserved and
utilized in the form of concentrates, which have a pleasing taste and substantial nutritive
value
 Jellies and other fruit preserves are prepared from fruit by adding sugar and concentrating
by evaporation to a point where microbial spoilage cannot occur
 The prepared product can be stored without hermetic sealing, although such protection is
useful to control mold growth, moisture loss, and oxidation
 Candied and glacéed fruits are made by slow impregnation of the fruit with syrup until
the concentration of sugar in the tissue is sufficiently high to prevent growth of spoilage
microorganisms

20. TRADITIONAL FOOD PROCESSING METHODS
Fermentation
 Controlled fermentations are used to produce a range of fermented foods
 Sauerkraut, pickles, olives, vinegar, dairy and other products
 Controlled fermentation is a form of food preservation since it generally results in a
increase of acidity of the food, thus preventing the growth of spoilage micro-organisms
 The two most common acids produced are lactic acid and acetic acid
 Other acids such as propionic, fumaric and malic acid are also formed during
fermentation
 It is highly probable that the first controlled food fermentations came into existence
through trial and error and a need to preserve foods for consumption later in the season
 It is possible that the initial attempts at preservation involved the addition of salt or
seawater

21. MODERN
FOOD
PROCESSING
METHODS

22. MODERN FOOD PROCESSING METHODS
Refrigeration
The life of many foods may be increased by storage at temperatures below
4°C (40°F)
Commonly refrigerated foods include fresh fruits and vegetables, eggs,
dairy products, and meats
Also, refrigeration cannot improve the quality of decayed food; it can only
retard deterioration
One problem of modern mechanical refrigeration—that of dehydration of
foods due to moisture condensation—has been overcome through humidity
control mechanisms within the storage chamber and by appropriate
packaging techniques

23. MODERN FOOD PROCESSING METHODS
Canning
 Tin-coated steel containers, made from 98.5 percent sheet steel with a thin coating of tin, soon
became common, after 1820’s
 These cans had a double seamed top and bottom to provided an airtight seal and could be
manufactured at high speeds
 A typical canning operation involves:
 Cleaning, filling, exhausting, can sealing, heat processing, cooking, labeling, casing, and
storage
 Most of these operations are performed using high-speed, automatic machines
 The thermal processes of canning are generally designed to destroy the spores of
the bacterium C. botulinum
 This microorganism can easily grow under anaerobic conditions, producing the
deadly toxin that causes botulism
 Sterilization requires heating to temperatures greater than 100°C (212°F)

24. MODERN FOOD PROCESSING METHODS
Pasteurization
Pasteurization is the application of heat to a food product in order to:
Destroy pathogenic (disease-producing) microorganisms
Inactivate spoilage-causing enzymes
Reduce or destroy spoilage microorganisms
The relatively mild heat treatment used in the pasteurization process causes
minimal changes in the sensory and nutritional characteristics of foods
compared to the severe heat treatments used in the sterilization process
The typical processing conditions for the pasteurization of fruit juices
include heating to 77°C (171°F) and holding for 1 minute, followed by rapid
cooling to 7°C (45°F)

25. MODERN FOOD PROCESSING METHODS
Pasteurization
In the pasteurization of milk, the time and temperature conditions target the
pathogenic bacteria Mycobacterium tuberculosis, Coxiella burnetti, and Brucella
abortus
The typical heat treatment used for pasteurizing milk is 72°C (162°F) for 15
seconds, followed by rapid cooling to 7°C
The high-temperature–short-time (HTST) treatments cause less damage to the
nutrient composition and sensory characteristics of foods and therefore are
preferred over the low-temperature–long-time (LTLT) treatments
Liquid foods such as milk, fruit juices, beers, wines, and liquid eggs are
pasteurized using plate-type heat exchangers
Plate-type heat exchangers are effective in rapid heating and cooling applications

26. MODERN FOOD PROCESSING METHODS
Chemical Preservation
Sugar (jams, jellies, marmalades), vinegar and salt (pickling), and some
chemicals foreign to foods are added to prevent the growth of
microorganisms
The latter group includes some natural food constituents such as ascorbic
acid (vitamin C), which is added to frozen peaches to prevent browning
Sodium benzoate (benzoic acid) and other benzoates are among the
principal organic chemical preservatives
Sulfur dioxide and sulfites are perhaps the most important inorganic
chemical preservatives
Oxidizing agents such as nitrates and nitrites are commonly used in the
curing of meats

27. MODERN FOOD PROCESSING METHODS
Irradiation
 Food irradiation involves the use of either high-speed electron beams or high-energy
radiation with wavelengths smaller than 200 nanometers, or 2000 angstroms (e.g., X-rays
and gamma rays)
 The two most common sources of high-energy radiation used in the food industry are
cobalt-60 (60
Co) and cesium-137 (137
Cs)
 The unit of absorbed dose of radiation by a material is denoted as the gray (Gy), one gray
being equal to the absorption of one joule of energy by one kilogram of food
 The bactericidal (bacteria-killing) effect of ionizing radiation is due to damage of the
biomolecules of bacterial cells
 The free radicals produced during irradiation may destroy or change the structure of
cellular membranes
 In addition, radiation causes irreversible changes to the nucleic acid molecules (i.e.,
DNA and RNA) of bacterial cells, inhibiting their ability to grow

28. MODERN FOOD PROCESSING METHODS
Irradiation
 Pathogenic bacteria that are unable to produce resistant endospores in foods such as
poultry, meats and seafood can be eliminated by radiation doses of 3 to 10 kilograys
 If the dose of radiation is too low, then the damaged DNA can be repaired by
specialized enzymes
 The dose of radiation used on food products is divided into three levels:
 Radappertization is a dose in the range of 20 to 30 kilograys, necessary to sterilize a
food product
 Radurization is a dose of 1 to 10 kilograys, that, like pasteurization, is useful for
targeting specific pathogens
 Radicidation involves doses of less than 1 kilogray for extending shelf life and
inhibiting sprouting

29. MODERN FOOD PROCESSING METHODS
 Ohmic Heating (Weak electric waves at 50-60 Hz)
 Microwave Heating (EM waves 2450 MHz and 915 MHz)
 Radiofrequency Heating
 Infrared Heating
 High Pressure Processing (HPP) (Pressure of up to 900 MPa)
 Pulsed Electric Field (PFF) (High voltage electric pulses 70 kV/cm)
 Ultrasonication
 Pulsed Light Technology (UV/Infra-red light flashes 1-20 per second)
 Pulsed X-rays
 Irradiation
 Oscillating Magnetic Field