Module 1 - Topic 1 (LE 1, pt. 1)

• • In the 1600’s Anton Van Leeuwenhoek discovered microorganisms — (the era prior to the establishment of bacteriology as a science may be designated as the pre-scientific era)
• • Pre-scientific era — there was no study of microbiology or bacteriology yet (can be divided into the food-gathering period and the food-producing period)
• • Food-producing period — 10,000 years ago up until the present — the problem of food spoilage and poisoning were only encountered in this period since people learned how to preserve food, prepare food, and store food during this period 
• —> The history of food microbiology dated back to 6000 BC or 6th Millennium before Christ where the spoilage of prepared foods were recorded 
• —> In 5000 BC, the first evidence of a beer manufacturer has been traced to ancient Babylonia and the art of cereal cookery, food storage, and brewing methods were also recorded at 5000 BC
• —> From 1200-3500 BC the first dairy products were made such as milk, butter, and cheese — the pioneers for these were the Sumerians (they were the first great livestock breeders and dairy men) — also the juice at this time use salt for food preservation (they used Dead Sea salt and they found that salt can preserve their fish and they can also create fermented sausages)
• —> In 1000 BC the Romans excelled in the preservation of meats other than beef and they also used snow to pack prawns and other perishables (But during this time, people still didn’t know why food generally got spoiled, although they know that it can)
• —> Between 943 to 1100 AD, there was an Ergot poisoning caused by Claviceps purpurea — it caused around 40000 deaths just in France alone since they still didn’t understand the role of microorganisms in food 
• —> From 1156 to 1276, meat butchers were first mentioned — people have become more civilised and the Swiss were now concerned about the marketability of their meat products (they developed a defined perception of what is marketable and what is not - similar to testing for food quality) — in 1276, there was a slaughter and inspection order for the public abattoirs in Augsburg, but still the knowledge of the relationship between food quality and microorganisms up until the 14th century was not known 
• —> In 1658, Kircher was the first person to describe the relationship between microorganisms and food because he examined decaying bodies along with meat, milk, and other food substances (he described what he observed as worms) - this description lacked precision and the scientific community and the public didn’t accept this explanation and was debunked)
• —> Then, the discovery of the microscope occurred, and Anton Van Leewenhoek first first observed yeast cells in 1680 and he was also the one to first describe bacteria and protozoans (however scientists at this time were very curious about what Anton discovered as Animalcules, and they asked where did these “tiny things” originate from, so the spontaneous generation theory arose)
• Spontaneous Generation Theory —> States that living organisms can come from non-living organisms 
• —> Year 1668 to 1765, some scientists were not convinced by this theory and two Italian scientists (Francesco Redi and Lazzaro Spallanzani) were able to perform experiments

  • Francesco Redi performed a meat experiment 
  • Lazzaro Spallanzani also performed an experiment to further disprove the spontaneous generation theory 
• —> Francesco Redi had two set-ups for his experiment (left= 1st, right = 2nd)

  • The first set up has meat in an open jar that is left in a place accessible to flies (when flies laid their eggs here, maggots grew and they multiplied)
• Francisco Redi‘s

  • The second set up had meat in a tightly sealed jar and he observed that maggots did not grow (however, those against him argued that the spontaneous generation theory requires oxygen, which a tightly sealed jar does not have enough of) 
• Francisco Redi’s:

  • He made a third set-up to disprove the spontaneous generation theory by covering the jars with cloth netting (allowing oxygen inside, and the flies to lay their eggs on top of the cloth) — he finally observed that there was no growth inside 
  • He concluded that meat alone was not able to generate maggots
• —> Antagonists to Redi at the time said that “perhaps spontaneous generation cannot occur with larger creatures (Ex: maggots) but can occur in microscopic organisms”
• —> A supporter of the spontaneous generation theory, John Needham, did an experiment where he put nutrient broth in a flask, heated, then sealed it and obtained a spoiled product — he concluded that microorganisms developed spontaneously from the fluids (he stated that there was a reaction that occurred in the nutrient broth that cannot be seen physically (ex: with maggots)
• —> Spallanzani said that John Needham’s methodology was incorrect and that there was another way to prove that the spontaneous generation theory was incorrect (he did the same experiments as Needham’s but he interchanged the two steps) — he has a fluid placed in a flask, sealed it, then heated it, and found it to be not spoiled (spontaneous generation did not occur)
• —> At 1795, Nicolas Appert was the first one to do a food preservation by canning or appertization (from his surname)
• —> In 1835, Louis Pasteur was the first person to appreciate and understand the presence and role of microorganisms in food because he demonstrated souring of milk (after two centuries debating about the spontaneous generation theory, in the 18th century, he finally ended the debate) — Louis Pasteur demonstrated the use of heat to destroy microorganisms in wine and beer (now, known as pasteurisation) — microorganisms are needed as a starter culture in beer and wine but they must be deactivated to prevent the beverage from spoiling 
• Louis Pasteur demonstrated that microorganisms are present in the air and can contaminate sterile solutions
• Air itself does not create microorganisms
• Pasteur's experiment

  1. Sterilized/heated the broth

  2. Allowed the broth to cool slowly

  3. Created a set-up with an S neck

  4. Stores the flask for years

  5. Tilted the flask

  6. Bacteria multiplied in the broth within hours/days
• Spontaneous generation theory


  Theory stating that the microorganisms in the air were the agents responsible for contaminating non-living matter such as the broths in Needham’s flasks
• Pasteur's experiment debunked the spontaneous generation theory
• —> Louis Pasteur concluded that microorganisms cannot originate from mystical forces/from non-living materials
• —> Louis Pasteur also said that microorganisms can be present in non-living matter (solid, liquid, air), but may not be born from these matters 

  • Pasteur demonstrated that microbes can be killed by heat and that methods can be devised to block the access of airborne microorganisms to nutrient environments (through the S neck in the flask)
  • This is the basis of aseptic technique 
• — Although the primary role of microorganisms sometimes appear to be destructive, since they cause food spoilage and foodborne diseases, their primary role is not to destroy but to self perpetuate or continue self preservation 
• food legislations - are designed to protect consumers from food that can be dangerous to one’s health and protect consumers from misleading information) (ex: food safety, food labelling, and advertising)
• —> Three distinct categories of types of microorganisms: 

  1. Prokaryotes (bacteria)
  2. Eukaryotes (yeast, moulds, parasites)
  3. Viruses
• Viruses — comprised of a single type of nucleic acid surrounded by a protein coat, not free-living (need a host to live), obligate intracellular parasites (bacteriophages) (not all viruses are bad, bacteriophages are able to kill bacteria without any negative effect on human or animal cells) — bacteriophages and antibiotics can be used to treat bacterial infections
• For example, listex is a product of phage-guard to eliminate listeria monocytogenes which is a foodborne disease that can cause listeriosis (it’s one of the deadliest food borne pathogen, with a rate of mortality of 20-30%) 
• Sources of Foodborne microorganisms:

  1. Soil and water 
  2. Plant and plant products 
  3. Food utensils 
  4. Gastrointestinal tract 
  5. Food handlers 
  6. Animal feeds 
  7. Animal hides 
  8. Air and dust 
• when analyzing microorganisms in food, we have to ask:

  1. What is the total number of microorganisms per gram or mL of food?
  2. What types of microorganisms are represented in this number?
• —> There are spoilage microorganisms that are mostly caused by commensal microorganisms that were not controlled (they are commensal = present in the environment, but they were uncontrolled and reached a population of 10^5-10^7 in cfu/g) — most spoiled foods do not cause foodborne diseases (it’s more of a food quality concern rather than food safety) 
• —> Some examples of spoilage microorganisms are: Colletrotrichum gloeosporiodes (Causes Anthracnose in mango), Monilinia vaccinii (causes whitening or mummyberry in blueberries), Rhizopus stolonifer (causes bread moulds), Erwinia carotovora (causes bacterial soft rot in carrots)
• —> pathogenic microorganisms encompasses a small group of microorganisms associated with diseases in humans — pathogenicity may be manifested by infection, intoxication, or toxicoinfection 
• —> Some types of pathogenic bacteria: Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus (Starchy food) , Clostridium botulinum (canned food), Escherichia coli, Vibrio cholera, Salmonella enterica
• —> Some examples of pathogenic protozoa are Cryptosporidium app., Cycospora cayatenensis, Entamoeba histolytica, Giardia lambda, and Toxoplama gondii