Average: 76.7

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Exam 2
Average 76.7
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2
Question 1
Types of coagulants
         What types of coagulant (rennet or
rennet substitutes) are available?

• Calf or lamb rennet
• Extract from calf or lamb stomach
• Contains proteolytic enzymes
• chymosin (95), pepsin (5)

• Rennet substitutes
• Animal
• Plant
• Fungal protease ex. Mucor miehei enzyme preps
• Genetically engineered microorganisms
  recombinant chymosin

Dried or liquid forms
http//www.wsu.edu/creamery/phototours/phototoursc
hz.htm
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Question 2
Heat treatment of milk
Describe how the heat treatment of the milk (no
heat treatment, thermization or pasteurization)
impacts the microbiology and biochemistry of
cheese ripening.
Why would a cheese maker choose to use
unpasteurized (heat-treated or raw) milk for
cheese making?

• Pasteurize
• 161F (71.7C), 15 seconds or equivalent
• Required for cheeses that are not held for
• gt60 days at gt1.7 C

• Thermization
• Heat treatment less than pasteurization
• NSLAB and others can survive

Cheese must be held for gt60 days at gt1.7 C (FDA)

• No heat treatment
• Raw milk

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Question 2
Microbiological changes Nonstarter bacteria
Nonstarter bacteria unintentionally added
bacteria that grow to high numbers in cheese.
Lactobacillus, Enterococcus, Micrococcus,
Pediococcusothers
Starter
Nonstarter LAB (NSLAB)
109
cfu/g
101
Time
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Question 3
Sauerkraut Microbiological Changes
Explain the progression of microorganisms in a
typical sauerkraut fermentation.
Time
6
Question 3
Pickles Microbiological changes
NaCl inhibits L. mesenteroides no heterolactic
fermentation
Time
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Question 4
Ripening Surface-ripened (mold)
Which has the higher pH, the surface or the
inside of a surface mold ripened cheese? Give
two reasons for the pH difference.
Penicillium camemberti mold spores added to
surface of cheese after pressing or added to milk
before coagulation
Little O2 inside cheese, so mold only grows on
surface. BUT, the extracellular enzymes produced
by the mold (proteases and lipases) can diffuse
in to the cheese. Size affects ripening.
Examples Camembert Brie
Flavor from protein, carbohydrate and lipid
degradation by

• P. camemberti proteases and lipases
• Milk enzymes
• Coagulant
• Starter culture
• Nonstarter bacteria

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Question 4
Ripening Surface-ripened (mold), pH
Changes in pH during Camembert cheese ripening

• pH increases due to
• Release of ammonia by molds proteolytic enyzmes
• Consumption of lactic acid by mold

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Question 5
Vegetable Fermentations Steps
Why are heterolactic fermenting lactic acid
bacteria undesirable in pickle fermentations?
How is their growth discouraged?

• Brining

Addition of salt affects which organisms can grow
Brining methods
Dry salting cabbage - osmotic pressure draws
water from the plant cells to make a brine
Brine addition cucumbers and olives, - add a
concentrated salt solution to vegetables - final
salt concentration is affected by water coming
out of vegetable cells
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Question 5
Pickles Microbiological changes
NaCl inhibits L. mesenteroides no heterolactic
fermentation
Time
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Question 5
Vegetable Fermentations Spoilage
Tissue softening pectinolytic enzymes from
yeast and molds
Discoloration pinkish color of sauerkraut -
yeasts
Off odors and flavors usually from coliform
growth before L.A.B become established
Gaseous deterioration Growth of heterolactic
fermenters in pickle and olive fermentation -
Aerobic growth of yeast molds before conditions
become anaerobic
bloaters
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Question 6
Some cultures do not ferment galactose
Lactose
Galactose
in cheese
Lactose
Reducing sugar will react with free amino groups
when heated ------Maillard browning
Glucose
Galactose
Glycolysis
Lactate-
2H
Gal- species
Gal alternatives
Lactate-
2H
S. thermophilus Lb. delbrueckii
Gal derivatives Lb. helveticus
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Question 7
Sources of proteolytic enzymes in cheese
Name three sources of proteolytic enzymes that
are active in all ripened cheeses and describe
how they participate in casein breakdown.
Coagulant
Native milk enzymes pepsin, trypsin (heat
sensitive and low activity at cheese
pH) plasmin (heat stable and active at cheese pH)
Bacteria (starter and nonstarter) cell
envelope-associated protease intracellular
peptidases
Molds (if added)
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Question 8
Whey Composition
Why is there more calcium in whey from an acid
curd than whey from a paracaseinate curd?
How does the whey differ between the two curd
types? What are the two main types of whey in
the U.S. and how do they differ?
Fluid Sweet Whey
Fluid Acid Whey
93.66 0.25 0.60 4.85 0.50 0.14
93.64 0.05 0.54 4.50 0.80 0.47
Water Fat Protein Lactose Ash (minerals) Lactic
acid
Whey from paracaseinate curd has
caseinomacropeptide (review on next slide).
If cheese is made by acidification, lactose
will be higher - 5.0.
Some fat and protein components of whey have
health benefits.
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Question 9
Setting the milk (paracaseinate curd) Step 2
Coagulation
What are the functions of the coagulant?
Add coagulant. Wait 20-30 minutes.
http//www.wsu.edu/creamery/phototours/phototoursc
hz.htm

• Coagulants contain proteases and serve two
  purposes
• Coagulate the casein micelle to form
  paracaseinate curd.
• Participate in casein breakdown during cheese
  ripening

• What determines the type of coagulant?
• Tradition
• Price and availability
• Proteolysis during cheese ripening

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Question 10
Transformation of curds (optional)
Dependent on cheese variety not all have this
step
Coalesce curds together to form the
characteristic texture or the cheese
variety Accumulation of acid and/or physical
manipulations help the curds come together in a
specific way
Examples Cheddaring of Cheddar cheese,
stretching of Mozzarella
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Question 10
Mozzarella
Changes in structure due to stretching
Figure from M. Johnson, University of Wisconsin
Figure from D. McMahon, Utah State Univeristy
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Question 10
Mozzarella
Figure from M. Johnson, University of Wisconsin
Extent of demineralization
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Cheddaring Process Curd Transformation
Question 10
Cheddaring piling and repiling of matted curd
blocks until desired acid level is reached
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Question 11
Whey expulsion factors (Syneresis)
Discuss the factors that affect the moisture of a
cheese.
What determines how much whey is removed from the
curd?
More whey loss
Less whey loss
Curd firmness
Size of curd particles
Acidity
Heat during cooking
Force during pressing
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Question 12
Changes in micelle structure with acidification
If you want a cheese with at stretchy texture,
would you want more or less acid (higher or lower
pH) in the curd compared to a cheese with a
crumbly texture?
H
H
H
Increasing acidity, decreasing pH
Loss of structure, pasty, gummy, brittle
Pliable, elastic, stretchy
Rigid, rubbery, no curd knitting
Crumbly
0.95 TA pH4.9
0.15 TA pH 5.4
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Cheese Ripening
Question 13a
See entire cheese ripening lecture notes
Flavor and texture changes during ripening are
caused by

• MICROBIAL POPULATION CHANGES
• Starter culture bacteria
• Other intentionally added bacteria, yeasts,
  molds
• Unintentionally added microorganisms

         What is autolysis, and why is it
important in cheese ripening?
Where do nonstarter lactic acid bacteria (NSLAB)
come from and what is their effect on cheese?
CHEMICAL REACTIONS
Enzymes Nonenzymatic chemical reactions
How does proteolysis during ripening affect
cheese flavor and texture? How are autolysis and
proteolysis related?

• Added enzymes
• Native milk enzymes
• Microbial enzymes

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Question 13b
Methods to accelerate cheese ripening
See lecture notes for details on each
Name one method to accelerate cheese ripening and
briefly describe how it works.
If you want your Cheddar cheese to ripen quickly,
what attributes would you want in your starter
culture (Lactococcus lactis)?
What is an adjunct starter culture?
Elevated ripening temperature Addition of
enzymes Selection of starter cultures Attenuated
or inactivated starters Adjunct starters
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Question 14
Cheddar and camembert cheeses are very different
from each another yet they are produced using the
same starter culture (mesophilic) and raw
material (milk). Describe factors that cause the
dramatic differences in the final products.
Include processing steps, microorganisms and
enzymes involved in these differences. (You
could do this with any of the cheeses that we
discussed.)
See cheese chart for details
Type of curd Relative curd cutting sizes Relative
cooking temperatures Pressing Salting Special
features special bacteria, molds, or enzyme
special processing steps