Fermented foods Flashcards
What was fermentation used for?
Preserve food, enhance shelf life, increase safety
Improve flavour, texture
What is the definition of fermented foods?
Foods or beverages produced through controlled microbial growth and the conversion of food components through enzymatic action
Is fermented food a “functional food”?
Yes
What are the two ways that fermented food originates?
Spontaneous and induced
What is spontaneous fermentation?
Natural fermentation. The microorganisms are naturally present in the raw material or manufacturing environment.
What is induced fermentation?
Microorganisms are added as a starter culture . The natural microflora is inefficient, uncontrollable, unpredictable or destroyed by heat treatment.
How do you select the starter culture?
Selection based on the type and quality of the product
Incubation temperature during fermentation
Nutrient content
Which important role does the food matrix play?
Plays a role in the survival of bacteria via its protective effect against gut conditions (pH, bile acids)
Why is the starter culture added in high inocculum levels?
So that it will have low competition from other organisms
What is the species used for producing yoghurt called?
Streptococcus thermophilus
What are the basic characteristics of lactic acid bacteria?
Gram positive
Ferment sugars to lactic acid
Catalase negative
Non-motile
Unable to form endospores
Able to grow at low pH (below 5.5)
Non-pathogenic
Which taxa are included in the functional concept “lactic acid bacteria”?
Lactococcus (sourmilk, cheese)
Lactobacillus (Spontaneously dominating most traditionally lactic acid fermented foods)
Leuconostoc (initial fermentation of plant material)
Oenococcus (wine, beer)
Pediococcus (smoked fermented sausage, fermented vegetables, cereals, beer)
Weissella (Spontaneous in many lactic acid fermenting foods)
Species: Streptococcus thermophilus (starter culture youghurt)
Which species are often mistaken for lactic acid bacteria but isn’t actually?
Bifidobacterium, Enterococcus, Carnobacterium
Why is enterococcus not LAB?
Because it causes urinary tract infections and easily acquires antibiotic resistance
Can cause sepsis
Give some examples of fermented foods
Kefir
Kombucha
Sauerkraut
Tempeh
Kimchi
Sourdough bread
Are fermented foods and probiotics closely related?
Yes
What is the WHO definition of probiotics?
Live microorganisms that, when administered in adequate amounts, confer a health benefit to the host
Hosw many bacteria do fermented foods typically contain?
10^5-7
How many LAB do dairy products contain?
10^9
Do fermented food products contain live bacteria?
Not when heated, may also not have survived because of harsh environment
What must the microorganisms in the product manage to survive from in the product?
Salt
Organic acids
Ethanol
Anaerobic milieu
Low pH
What does allochtonous mean?
Foreign
What is the transient microbiota?
Part of the variable microbiome that varies with diet. Can be detected for a few days but not after one week
The human microbiome is made up from a transient and a _____ community
Core commensal community
What in the fermented product enhances the activity of the microbial enzymes (amylases, proteases, phytases, lipases)?
The acidic nature of fermented products
What do the microbial enzymes do?
Modify primary food products through hydrolysis of polysacharrides, proteins, phytates and lipids
Give examples of some nutritional benefits of fermentation
Synthesise complex vitamins
Release nutrients from indigestible cellulosic and hemicellulosic structures surrounding endosperm in grain and seed making them available for humans to digest
Can LAB produce lactase to digest lactose?
Yes
What are phytate?
They form insoluble complexes with minerals (iron, zinc, calcium, magnesium) and is abundant in cereal grains, oil seeds, legumes, flours
