Fermentation in Dairy Flashcards
Describe the application of biotechnology post farm.
-
Processing
- Fermentation (e.g., milk to yogurt)
- Non-fermented probiotic foods
- Novel foods
-
Production of specific compounds
- Processing aids (e.g., enzymes)
- Additives (e.g., colour, flavourings)
-
Waste management
- Transformation of waste into environmentally friendly material (biodegradation)
Define: fermentation
Anaerobic (and sometimes aerobic) breakdown of organic materials (mostly carbohydrates) by microorganisms as part of their metabolic process.
Yeasts; moulds; bacteria
List a few fermented food products.
- Kombucha
- Natto
- Cheese
- Kefir
- Sauerkraut
- Kimchi
Fermentation has a long history of use in the human diet. Give a few basic facts.
- Desirable microorganisms grow on food and produce
compounds as part of their metabolism- These compounds provide a desired characteristics in
food by formation of specific metabolites
- These compounds provide a desired characteristics in
- Serves as a low cost means of preservation in less
advanced societies by preventing the growth of
pathogens and spoilage former - Gives variety in industrialized societies
Describe the resurgence of fermented foods.
- Fermented foods named as the top superfood
- According to “What’s trending in nutrition”
- Cultural shift from heart health to gut health
- Connection to brain function
- Rise in lactose intolerance
- Fermented dairy products are better tolerated
Why do we ferment foods?
What is the outcome of fermentation? [5]
- Formation of metabolites
- Acids; aldehydes; ketones; alcohols; CO2
- Prevention of spoilage
- Inhibition of pathogen growth
- Lowering the total energy (except alcohol producing fermentation)
- Higher nutritive value
Metabolites provide unique sensory quality to fermented foods.
Compare primary and secondary fermentation metabolites.
What are the three large categories of fermentation?
- Natural fermentation
- Traditional culture
- Use of pure cultures
What is natural fermentation?
-
Microorganisms arrived by chance in raw food
- Microorganism as part of their ecosystem ( LAB in milk)
- Microorganism as part of processing (yeast in grape and grape crushing equipment)
- Condition provided to compete and outgrow
- Fermentation occurred
- Stabilization in fermented food
- Still being used in home pickling and small scale wine making
What are the problems with natural fermentation? [5]
- Right form of microorganism should be present
- Long time required for processing
- Surprise outcome
- Safety risks
- Not reliable for industrialized production
What is back slopping?
- Sample of successful fermentation used for the next batch of fermentation (e.g., Home made sourdough)
- Large quantities of dominant mixed culture is added as a fermenting source
- Shorter time required compared to natural fermentation
- More predictable results
- Still being used in small scale beer processing, some cheese types and vinegar
Traditional mixed culture
What is the concern with traditional fermentation?
Although more uniform and predictable than natural fermentation, still does not meet the requirements for large scale production to avoid safety and economical risk
Describe the characteristics of the modern fermentation food industry. [9]
- Large scale
- Heat treated medium
- Aseptic condition
- Contained structure
- Automated
- Time sensitive
- Minimal exposure to contaminants
- Consistent quality
- Safety a major concern
What is Koch’s Postulate? [4]
- The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms.
- The microorganism must be isolated from a diseased organism and grown in pure culture.
- The cultured microorganism should cause disease when introduced into a healthy organism.
- The responsible microorganism can be re-isolated and purified and once re-introduced to the host will have the same disease causing property
Describe the use of Koch’s postulate in fermentation science.
The responsible microorganism for fermentation can be isolated and purified and once reintroduced to raw material it will cause the same fermentation
What is a pure starter culture? [4]
- A selected type of microorganism or mixture of different microorganisms to initiate the fermentation
- Laboratory selected and pre-cultured starters used (first attempt in 1883- isolating brewer’s yeast by Emil Christian Hansen)
- Pure starter cultures are propagated under sterile condition
- The food to be fermented is usually heat treated to minimize the presence of other microorganisms
What are the problems with pure culture fermentation? [2]
- Expensive for small scale producers
- Does not have the same organoleptic properties of natural/traditional fermentation
What are some challenges in fermented product development? [3]
- In cultured/fermented products you deal with both chemistry and microbiology as it pertains to the product’s sensory and physical attributes
- Microorganisms may behave differently due to strain differences
- Slight changes in the conditions (e.g., temperature) may cause a different strain to dominate
Describe lactic acid bacteria.
- “A nontaxonomic classification for a group of Gram-positive non-spore-forming bacteria which ferment sugars to lactic acid”
- Emerged 1.5-2 billion years ago
- Lack pathogenicity
- Ferment lactose and other carbohydrates to lactic acid
- Relatively acid tolerant
- Mostly aerotolerant anaerobe
At this time there are 13 genera established as LAB. Which ones are dairy LAB? [3]
Lactobacillus
Lactococcus (relatively new taxonomic group)
Streptococcus
Note that Bifidobacteria have been erroneously included in some older resources
Describe a process flowchart for yogurt making.
Describe the cheese making unit operation.
Bacteriophages are viruses that attack bacteria. How does this happen?
- They have the typical virus structure (head and tail)
- Attach to specific receptor (Ca++ required)
- Channel formation
- DNA penetration
- Degradation of host chromosome
- Synthesis of phage DNA components
- Breach of host cell wall
- Release of phage components
- Transform into complete phage
Describe the lytic pathway of bacteriophage infection.
Not mentioned in this class, but there is also the lysogenic cycle whereby the viral DNA incorporates itself into the host genome and remains dormant for a long time before lysis. Lysogenic may be more efficient since it allows the host cell to replicate with the viral DNA in the meantime.
