Transcript Purdue : Fermentation Notes

Purdue :
Fermentation Notes
Ch 17
Food processing with fermentation
• Fermentation is the breakdown of carbohydrates ( glucose)
• Under anaerobic ( absence of oxygen) conditions
• Could also involve microbial-induced changes to the proteins and lipids in the foods
• Color , flavors and textures characteristic of fermented foods
MICROBIAL- INDUCED CHANGES
RAW MATERIAL ---> FERMENTED PRODUCT
AGENT
RAW MATERIAL
PRODUCT
Lactic acid bacteria
Lactose, glucose
Lactic acid
Yeasts
Glucose, other fermentable
carbohydrates
Ethanol
Acetic acid bacteria
Ethanol
Acetic Acid
Lipids
Free fatty acids, aldehydes, ketones
Proteins
Polypeptides, peptides, free amino
acids, amines (cause texture and
flavor changes in food)
Cellulose
Oligosaccharides, glucose
Microbial lapases
Microbial proteinases
Mold cellulases
Food products obtained by fermentation
• Fermented beverages:
• Wine, Beer, Sake, Sake, Mead, Root/ ginger beer
• Fermented dairy products:
• Yogurt, kefir, specialty cheeses, cheddar cheese
• Fermented meat products:
• Salami, bologna, prosciutto
• Traditional fermented foods:
• Sauerkraut, soy sauce, tempeh, idll, yaktult, miso
Microorganism
Food commodity
Fermented product
Lactic acid bacteria
Cucumbers
Olives
Cabbage
Coffee cherries
Vanilla beans
Meat
Dairy
dill pickles, sour pickle
Green olives, ripe olives
Sauerkraut
Coffee beans
Vanilla
Meat sausage (salami)
Sour cream, yogurt
Yeast
Malt
Grapes (fruit)
Wines
Rice
Bread doughs
Beer, ale, stout
Wine, vermouth, Mead
Brandy
Sak’e
Bread
Mold
Soybeans
Miso, soy sauce
Preservation effect:
• Metabolites: End products of fermentation
• Antimicrobial compounds ( like Acids, alcohols)
• Acids ( formed in situ*) can also lower pH of food
• * situated in the original, natural, or existing place/ position
• Microbial Antagonism
• Supress growth & metabolic activities of spoilage causing microflora
May need additional processing methods for preservation
Eg.) refrigeration or pasteurization or vacuum packaging, etc
Benefits of fermentation
• Increased nutritional value and availability
• More nutritious than starting materials
• Mold fermented foods have B vitamins
• Liberate nutrients from plants that would be otherwise indigestible in the human GI tract
• Microbial hydrolysis of cellulose materials that are indigestible by humans
• Add variety to our food supply and diet
Starter cultures
• Specifically selected Microbial cultures
• Desirable traits for the particular fermentation
• Metabolism leads to the desired products
• Like acids, alcohols, and flavor compounds
• Dominant microorganism
Starter cultures added…
• As a “pure” culture
• Yeast in bread
• From a previous batch
• Fermented food containing that culture
• ( sourdough, friendship bread, yogurt, kefir)
• Part of the normal microflora
• Sauerkraut, olives
Temperatures
Starter cultures will only grow at their optimum temperatures
eg) sauerkraut flavor- proper succession of
lactic acid bacteria:
Stage 1: Leuconostoc mesenteroides
initiates fermentation
Stage 2: Lactobacillus cucumeris takes over
Stage 3: Lactobacillus pentoaceticus
2-2.5% acid ferment is over (no more bubbles)
Oxygen
• Fermenting microorganisms have different oxygen requirements
• Baker’s yeast- grows better under aerobic conditions
• However, the yeast ferments sugars more rapidly under anaerobic conditions
Example of fermentation
• Cheese https://www.youtube.com/watch?v=FHmXAb3G0ek
• Root beer https://www.youtube.com/watch?v=kZ1Jt-JeED0
• Breadhttps://www.youtube.com/watch?v=ed6qDJHmamw
• Why is milk pasteurized, water boiled, before starter cultures are added?
• It can interfere with fermentation
cheese making
Pasteurizationlactic acid culture and coagulating enzyme (rennet like substitutes)
Fermentation
lactic acid bacteria
casein micelles stable in calcium
calcium sensitive micelles form gel
Curd coagulation----------------------------- whey
Curd fuses together to form rubbery slab (matted)
Curds cut to smaller blocks ( milled)
*whey disposal is a major problem of the dairy industry
Cheese making cont.
Salting draws more liquid from curd (osmosis)
inhibits proteolytic organisms
adds flavor
Curing/ ripening
paraffin wrapped or vacuum packed
10 kg milk to make 1 kg cheese
22 lbs
2.2 lbs
What aspects of cheese(making) result in preservation?
(Longer shelf life than milk)
• Moisture content and Water activity
• Acidic conditions
• Lactic acid bacteria- microbial antagonism, antimicrobials
• Salt
Examples of different cheesesfermentation using different starter cultures
• Examples of hard cheeses
• Cheddar: lactic acid bacteria
• Swiss:
• Streptococcus thermophiles and
• Propionic acid bacteria
• CO2 – eyes in the cheese
• Proline- sweet
• Propionic acid- nutty flavor
Examples of different cheesesfermentation using different starter culture
• Semi- soft cheese
• Blue veined cheese• Blue cheese( US) ; stilton (England); Gorgonzola (Italy): cow milk
• Roquefort (France): goat milk
• Curd is needle-inoculated (penicillium roquefortii)
Blue veined cheeses
curd is placed to provide
channels for oxygen
(which is required for mold growth)
to enter the cheese
Examples of soft cheeses
• Mold ripening cheeses• Penicillium camembertii (or P. candidum)
• Proteases
• Small molecular weight peptides
• (characteristic flavor)
• Soft/ creamy texture
• Curds are not pressed
Cheese surface is inoculated with mold spores.
A layer of mycella forms the
white coating on the surface