Transcript Fermentation and milk

Fermentation and milk
review
fermentation
• Cellular respiration is aerobic (requires
oxygen) to convert glucose to carbon dioxide
and water, to produce energy
• Fermentation is anaerobic (no oxygen)
releases carbon dioxide to produce energy.
Depending on the organism, the other biproduct might be ethyl alcohol (yeast), lactic
acid (some bacteria) or acetic acid (different
bacteria)
Why ferment?
• Preservative
• Easier to eat
• Flavor
pasteurization
• The process that uses heat to kill bacteria. In
milk, this makes it safe to drink, with a longer
shelf life.
• For fermented products, this kills the
undesirable micro-organisms that will spoil
the fermented foods
• The organism that is used for fermentation is
then added.
Bacterial fermentation
• Bacteria used for fermentation are indigenous,
or the culture is added
• Lactic acid- produce lactic acid, used to
produce yogurt, sour cream, cheese, dill
pickles, sauerkraut
• Acetic acid- used to make vinegar
• Carbon dioxide- Gouda, Edam, and Swiss
cheese
Pickling
• Brine pickling- a high salt solution several
weeks until pH is lowered
• Fresh-pack pickling- placed in brine for a few
hours, then drained and placed in boiling
vinegar and spices
Sauerkraut
• Bacteria is on the cabbage, when washed and
chopped this increases the fermenting
bacteria, stored at 21 OC
• Salt- releases fluid to promote bacterial
growth, inhibits growth of undesirable
bacteria
• pH is lowered during fermentation
yeast
• Fermentation produces ethyl alcohol
• Best temperature 27 OC – temperatures too
high will kill the yeast
• While sugar is needed, too much sugar will
slow fermentation
• Salt- too much inhibits carbon dioxide
production, too little weakens gluten
beverages
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Use yeast
Pasteurization
Inoculation
Incubation
The flavor depends upon what is fermented
and the period of incubation
Coffee and tea
• Coffee
– cherries are either fermented wet or dry
– The fleshy part is removed
– Then beans are roasted
• Tea
– The leaves are rolled to encourage fermentation,
weaken the cell walls
– Then dried
Fermented products
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Cheese
Pickles
Sausage
Beverages
Tempeh
chocolate
• Brain pop
milk
• A solution, a colloid, and emulsion
– A solution
• Vitamins and minerals
• Carbohydrates
– A colloid
• Proteins
– An emulsion
• Fats
Milk proteins: colloid
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80% is casein micelles
Stable at normal pH
Coagulate (clump) at pH of 4.6 forming curds
Precipitate when heated (the bottom or float to
the top forming skin)
• Whey- the solution left (and the 20% proteins)
after casein coagulates
• Responsible for the Tyndall effect and why milk
is white
• Enzymes-most are denatured during
pasteurization
emulsion
• Fat globules surrounded by a membrane of
phospholipids and proteins
• 400 different fatty acids, but little cholesterol
• Creaming: When fats rise to the top of fresh
milk
carbohydrates
• Lactose: milk sugar- reacts with proteins when
heated gives flavor and color
• Lactose intolerance- when person does not
have lactase (the enzyme that breaks down
lactose)
– Results in gas, bloating, pain,
Vitamins and minerals
• Minerals- as salts
– Helps prevent milk from curdling
– Calcium and magnesium keeps casein micelles stable
– The enzyme Rennin- used in cheese making
coagulates more when fewer salts are present
• Vitamins- four main ones
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Riboflavin- light sensitive
Thiamin
Niacin
Vitamin A- fat soluble
processing
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To increase shelf life
Pasteurization
Homogenization
Fortification – vitamin D
Restoration Vitamin A in low fat products
Milk products
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UHT- ultra High temperature
Evaporated (uses carrageenan to stabilize)
Sweetened condensed
Dry milk
Fermented milk products
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Buttermilk (uses acid to coagulate casein)
Yogurt
Sour cream
Cheeses