food microbiology

1. FOOD
MICROBIOLOGY
BIO 4414
Heather Lofton-Garcia
MWF 1:00 – 1:50
Lab on Mondays 3:30 – 6:20

2. Food Microbiology
 Microbiology is the study of organisms
too small to be seen with the unaided
eye
 Food microbiology is a subdivision of
microbiology

3. Food Microbiology Studies
 Microbes that cause diseases in food
 Microbes that cause spoilage in food
 Microbes that produce food
 How food environments influence
microbes
 This science has changed
dramatically over the last 20 years

4. Microorganisms
 Were the first organisms to colonize
Earth
 Colonize just about every inch of the
Earth’s surface
 Most species are either harmless or
beneficial
 Pathogenic species can cause
disease

5. Microorganisms
 Decompose organic waste
 Are producers in the ecosystem by
photosynthesis
 Produce industrial chemicals such as ethyl
alcohol and acetone
 Produce fermented foods such as vinegar,
alcoholic beverages, cheeses and breads
 Produce antibiotics and vaccines

6. Groups of Microbes
 Bacteria
 Fungi
 Protozoa
 Algae
 Viruses
 Helminthes (parasitic worms)
 Prions (infectious altered proteins)
 Spores and toxins produced by each group
are important

7. Bacteria
 Prokaryotes
 Reproduce by binary fission at
phenomenal rates
 For energy they use organic
chemicals, inorganic chemicals, or
photosynthesis

8. Bacteria - cocci

9. Bacteria - bacilli

10. Fungi
 Eukaryotes
 Use organic chemicals for energy
 Molds are multicellular
 Yeasts are unicellular
 Many produce foods and some
species can cause food spoilage

11. Mold

13. Mushroom – edible
reproductive structure
Photos from kjbeath’s photostream

14. Yeast
www.scientist.live.com

15. Protozoa
 Eukaryotes
 Are usually unicellular
 Inhabit the water and soil
 Absorb or ingest organic chemicals
 Can contaminate food and water
supplies

16. Protozoa - Amoeba sp.
www.csm.jmu.edu

17. Algae
 Eukaryotes
 Cellulose cell walls
 Use photosynthesis for energy (like
terrestrial plants)
 Produce molecular oxygen and organic
compounds
 Many can produce toxins that
contaminate food and water

18. Diatoms
www.daviddarling..info/images

19. Red Tide
www.microbeworld.org

20. Viruses
 Acellular (non-living)
 Consist of DNA or RNA core
 Core is surrounded by a protein coat called
a capsid
 Viruses are replicated only when they are in
a living host cell
 Many are transmitted via contaminated food
or water, and many pass directly from
human to human contact

21. Rotavirus
http://www.carlgoodman.co.uk/scientific/scientific/A-microscopic-01.jpg

22. Helminthes
 Eukaryotes
 Multicellular animals – most are not
parasitic
 Some parasitic species are tapeworms,
flukes, and roundworms
 Microscopic stages exist in their complex
life cycles
 The eggs or larvae of many species can
contaminate meat products and seafood

23. Beef tapeworm
www.stanford.edu

24. Scary!!!!!

25. History of Food Microbiology
 Humans were originally hunter-
gatherers
 Food preservation and storage
procedures were not adequately
developed
 Early preservation methods were
most likely accidental

26. History of Food Microbiology
 Sun-dried, salted, or frozen foods did
not spoil
 Early humans learned to enjoy
“spoiled” milk products
 Fermentation became an organized
activity around 4000 B.C.
 Knowledge of the presence of
microbes did not occur until the mid-
1600s

27. History of Food Microbiology
 In 1665, Robert Hooke published
Micrographia that included the
structure of Mucor, a genus of fungus
 In 1676, Antony van Leeuwenhoek
used a crude microscope to study
pond water

29. Biogenesis
 The hypothesis that living organisms arise
from nonliving matter is called spontaneous
generation.
 The alternative hypothesis, that the living
organisms arise from preexisting life, is
called biogenesis.
 In the mid-1700s, Lazzaro Spallanzini tried
to disprove spontaneous generation by
placing boiled meat into sealed containers
to prevent spoiling

30. 1861: Louis Pasteur demonstrated that
microorganisms are present in the air with his
S-shaped flask – disproving spontaneous
generation

31. Louis Pasteur
 Commonly called the “Father of
Microbiology”
 Showed that microbes are responsible
for fermentation.
 Fermentation is the conversion of
sugar to alcohol to make beer and
wine.

32. Louis Pasteur
 Microbial growth is also responsible for
spoilage of food.
 Bacteria that use alcohol and produce
acetic acid spoil wine by turning it to vinegar
(acetic acid).
 Pasteur demonstrated that these spoilage
bacteria could be killed by heat that was not
hot enough to evaporate the alcohol in wine
 This application of a high heat for a short
time is called pasteurization

33. History of Food Microbiology
 Napolean offered a prize to anyone
who could preserve food
 Nicolas Appert won this prize by
heating foods and then canning them
 It was not until the 1900s that the
process of canning was fully
understood

34. Robert Koch
 1876: provided proof that a
bacterium, Bacillus anthracis,
causes anthrax
 Developed Koch’s postulates,
which are used to prove that a
specific microbe causes a specific
disease.

35. Koch’s postulates

36. Koch’s postulates

37. Other contributions from
Koch’s lab
 Julius Petri invented the petri dish
 Walter Hesse began to use agar
instead of gelatin to solidify
microbial media (he got the idea
from his wife)

38. Modern Contributions
 Many foodborne pathogens were
discovered in the early to mid 20th
century
 Bacteria: Salmonella species,
Clostridium botulinum,
Staphylococcus aureus, Bacillus
cereus
 Viruses were first crystallized and
associated with disease in the 1930s

39. Modern Contributions
 James Watson and Francis Crick
discovered the structure of DNA in the
middle of the 20th century
 This led to a better understanding of
microbes and how they cause illness,
how we can detect them, how we can
use them in industry
 Molecular biology is vital to food
microbiology

40. Modern Contributions
 GMPs (good manufacturing practices)
provide manufacturers with procedures
that yield safe products
 HACCP (hazard analysis critical control
point) plans help to assure safety at
each key step of the manufacturing
process
 Food irradiation is approved as “kill” step
in the processing of raw poultry and
meat

41. Recent Concerns
 About 1/3 of the world’s food supply is
lost to spoilage
 The world is demanding safer food
 “Globalization” of the food supply can
cause problems with sanitation
standards
 The causes of ½ of foodborne illness
cases are unknown (over 90% of
bacteria remain undiscovered)