Food Science Meredith Schneider, RD, LD pH &

Food
Science
Meredith
Schneider,
RD,
LD
pH
&
Acids/Bases
• Can
demonstrate
the
effects
of
acids
and
bases
on
the
color
of
food
and
pH
of
water
Ingredients:
broccoli,
microwave
dish,
pH
probe,
1
tsp
of
baking
soda,
2
tsp
of
cream
of
tartar,
4
two‐quart
pans,
wax
paper
1. Wash
broccoli
and
divide
into
5
pieces.
2. Place
1
liter
of
cold
tap
water
in
each
pan.
3. Test
pH
of
water
with
pH
probe.
Record
results.
4. Bring
each
pot
of
water
to
a
boil.
5. Treat
each
of
the
6
pieces
differently
according
to
following
instructions:
a. Add
one
piece
of
broccoli
to
pot
of
boiling
water.
Boil
uncovered
for
3
minutes.
After
cooking,
measure
pH
of
water
with
probe.
b. Add
one
piece
of
broccoli
to
pot
of
boiling
water.
Boil
covered
for
10
minutes.
After
cooking,
measure
pH
of
water
with
probe.
c. Add
½
tsp
baking
soda
to
water;
stir
well.
Bring
to
a
boil.
Add
broccoli
to
boiling
soda
water.
Boil
for
15
minutes.
After
cooking,
measure
pH
of
water
with
probe.
d. Add
1
tsp
of
cream
of
tartar
to
water;
stir
well.
Bring
to
a
boil.
Add
broccoli
to
boiling
water.
Boil
for
15
minutes.
After
cooking,
measure
the
pH
of
water
with
probe.
e. Place
broccoli
in
microwave
dish.
Add
water
to
cover
bottom
½
inch.
Cover
with
wax
paper.
Microwave
on
full
power
for
2
½
to
3
minutes.
After
cooking,
measure
pH
of
water
with
probe.
6. Record
results
and
evaluate
color
of
juice,
color
of
vegetable,
and
pH
before
and
after
cooking.
Acid:
baking
soda
Base:
cream
of
tartar
*Acid
will
lower
pH
(to
about
3);
base
will
keep
it
at
basic
pH
(around
9)
Food
Safety
and
Microbiology
• Biological
hazards
&
microorganisms:
bacteria,
viruses,
parasites,
fungi,
molds,
yeast,
toxins
o Bacteria:
pathogenic
organisms
that
use
nutrients
found
in
foods
and
are
potentially
dangerous;
can
be
toxic
and
produce
toxins
that
cause
diseases
o 2
very
dangerous
bacteria:
salmonella
&
Clostridium
botulinum
o FATTOM:
food,
acidity
(4.6‐7.0),
time
(2
hours
in
temperature
danger
zone),
temperature
(40°‐140°F),
oxygen,
moisture
 Contribute
to
bacterial
growth
•
•
Food
infection:
an
illness
resulting
from
ingestion
of
food
containing
large
numbers
of
living
bacteria
or
other
microorganisms
Food
intoxication:
an
illness
resulting
from
ingestion
of
food
containing
a
toxin
Solutions,
Colloids,
Gels,
Foams,
Emulsions
• Adding
a
solute
(ex.
Salt
or
sugar)
to
a
mixture
will
lower
the
freezing
point;
adding
too
much
slows
the
freezing
process.
• Adding
a
solute
can
elevate
the
boiling
point.
• 3
parts
of
an
emulsion:
o Dispersed
or
discontinuous
phase,
which
is
usually
oil
o Dispersion
or
continuous
phase,
which
is
most
likely
water‐based
o Emulsifier,
which
is
a
stabilizing
compound
that
helps
keep
one
phase
dispersed
in
the
other
(ex.
Lecithin,
mono‐
or
diglycerides,
gelatin,
gluten,
ground
paprika,
dried
mustard)
• Food
emulsions:
salad
dressings,
milk,
mayonnaise,
gravies,
pudding,
cheese
sauces
• Temporary
emulsions:
least
viscous
and
least
type
of
emulsion
that
separate
on
standing
when
left
alone
(ex.
Oil
and
vinegar
salad
dressing)
• Semipermanent
emulsions:
emulsions
with
a
stabilizer
added
so
it
does
not
separate
as
easily
(ex.
French
and
Italian
salad
dressings)
• Permanent
emulsions:
very
viscous
and
very
stable
to
the
point
that
they
do
not
separate
(ex.
Mayonnaise,
milk)
Emulsions
Experiment
Ingredients:
1
tsp
sugar,
¼
tsp
paprika,
½
tsp
dry
mustard,
¼
tsp
salt,
¼
tsp
pepper,
¼
cup
vinegar,
½
cup
canola
oil,
1
garlic
clove,
crushed
1. Secure
ingredients,
two
timers,
two
jars
with
lids
2. Make
French
dressing
using
all
ingredients
above
and
divide
in
half.
Place
all
ingredients
in
covered
jar.
Shake
and
divide
into
half
into
two
jars.
3. Begin
timing
version
1
to
determine
the
time
required
to
start
to
separate,
and
then
finally
to
complete
separation.
4. To
the
second
version,
add
½
tsp
dry
parsley
and
½
tsp
celery
seed.
Shake
well.
5. Start
timing
on
version
2
as
soon
as
parsley
and
celery
seed
are
added
and
shaking
completed.
6. Record
data.
7. Evaluate
dressings
for
color,
mouthfeel,
flavor
and
stability
of
product.
Have
students
identify
continuous
and
discontinuous
phases,
function
of
emulsifier
and
how
it
affected
the
mixtures
in
the
experiment.
Fermentation:
the
conversion
of
carbohydrates
to
carbon
dioxide
and
alcohol
by
yeast
or
bacteria
Experiment:
Influence
of
Liberation
of
Carbon
Dioxide
by
Yeast
Supplies:
Secure
eight
250
mL
beakers,
one
100
ml
beaker
with
graduated
markings,
centigrade
thermometer,
glass
stirring
rod,
100
mL
graduated
cylinder,
eight
10
ml
disposable
pipettes
with
graduated
markings
and
pipette
bulb,
timer,
water
bottle
filled
with
distilled
water,
one
500
ml
beaker
for
washing,
one
7g
package
of
yeast
1. Secure
supplies.
2. Turn
on
the
oven
to
350°F,
bring
it
to
temperature,
and
then
turn
it
off.
3. Label
the
8
beakers
with
masking
tape
with
numbers
1‐8.
4. In
a
100
ml
beaker,
add
80
ml
of
water
that
is
42°C.
Measure
the
water
with
a
100
ml
graduated
cylinder.
5. Add
one
package
of
dry
yeast
to
the
beaker
containing
80
ml
of
water
that
is
42°C.
Stir
with
glass
stirring
rod.
Wash
the
stirring
rod
with
distilled
water
in
water
bottle
over
a
500
ml
beaker.
6. Let
the
yeast
stand
for
a
few
minutes
to
allow
yeast
to
hydrate.
7. To
each
of
the
numbered
beakers
(1‐8),
add
the
following
items
as
specified
below:
Graduated
Amt
of
Temp
of
Substance
Vol.
at
Vol.
After
Vol.
After
Cylinder
#
Water
Water
Beginning
30
min.
1
Hour
1
118
ml
42°C
None
2
118
ml
42°C
2
g
sugar
3
118
ml
42°C
2
g
sugar
+
3g
salt
4
118
ml
42°C
2
g
sugar
+
6
g
salt
5
118
ml
42°C
25
g
sugar
+
3g
salt
6
118
ml
0°C
6
g
sugar
7
118
ml
42°C
6
g
sugar
8
118
ml
92°C
6
g
sugar
8. Transfer
10
ml
of
yeast
solution
to
each
of
the
8
graduated
cylinders
using
a
pipette
and
bulb.
9. Place
beakers
in
oven
on
rack,
with
oven
door
open.
This
will
create
a
warm
environment
for
the
yeast
to
ferment.
Start
timer.
10. Observe
fermentation
of
beakers
at
beginning,
in
30
min,
and
at
end
of
1
hour.
Use
table
for
data
collection.
Have
students
compare
yield
of
carbon
dioxide
in
beakers
2,3,4
and
compare
to
yield
in
beaker
1.
Compare
yield
of
CO2
in
beakers
3
and
5.
Account
for
difference.
Have
students
account
for
effects
of
temperature,
time,
and
substance.
Leavening
Agents
• The
presence
of
a
leavener
causes
a
flour
mixture
to
rise.
There
are
3
types
of
leaveners:
o Physical:
air
and
steam
o Biological
leaveners:
yeast
and
bacteria
o Chemical
leaveners:
baking
powder
and
baking
soda
• Baking
soda
must
have
an
acid
ingredient
added
to
the
flour
mixture
in
order
to
yield
carbon
dioxide.
When
using
baking
powder,
an
acid
does
not
need
to
be
added
to
the
mixture.
• Air
as
a
leavening
agent:
incorporating
air
into
a
flour
mixture
helps
the
dough
rise
(added
by
mixing,
creaming
of
fat
and
sugar,
sifting
dry
ingredients,
using
whipped
egg
whites)
• Steam
as
a
leavening
agent:
water
incorporated
into
flour
mixtures
produces
steam
when
heated
and
expands
to
1,600
times
its
original
volume.
Experiment:
Leavening
of
Bread
by
Steam­
Popovers
1. Secure
mixer
on
a
stand,
oven
thermometer,
popover
pan,
graduated
cylinder,
237
ml
Pyrex
cup,
mixing
bowl,
sifter,
sharp
knife,
hot
pads,
wire
cooling
rack.
2. Secure
ingredients
for
popovers:
3
large
eggs,
46
g
margarine
stick,
237
ml
reconstituted
non
fat
dry
milk,
1.5
g
salt,
129
g
instant
flour,
Pam
3. Preheat
oven
365°F
on
Bake
4. Spray
pan
with
Pam
5. Melt
margarine
in
microwave.
6. Sift
129
g
instant
flour
and
1.5
g
salt
7. Place
eggs
in
mixer
and
beat
slightly.
Add
237
ml
reconstituted
non
fat
dry
milk
and
melted
butter.
8. While
mixer
is
beating
on
slow
speed,
gradually
add
flour/salt.
Mix
for
30
seconds.
9. Pour
batter
into
cups
to
¼
inch
of
top.
10. Place
in
oven
and
check
in
50
minutes.
DO
NOT
bother
while
cooking.
11. Remove
when
popovers
are
dark
brown
and
crisp.
Make
slit
in
side
to
release
steam.
12. Remove
popovers
from
pan
and
place
on
wire
rack.
Questions:
1. What
is
the
main
leavener
in
popovers?
2. What
is
the
ratio
of
liquid
to
flour?
3. Why
did
the
popovers
rise?
4. State
ways
air
may
be
incorporated
into
a
batter
or
dough.
Food
Additives
• Purposes:
o Improve
the
appeal
of
foods
by
improving
their
flavor,
smell,
texture,
color
o Extend
storage
life
o Maximize
performance
o Protect
nutrient
value
• Common
food
additives
and
functions:
o Acetic
acid:
pH
control,
preservative
o Ascorbic
acid
(Vitamin
C):
nutrient,
antioxidant,
preservative
o Aspartame:
sweetener,
low
calorie
o Cellulose:
emulsifier,
stabilizer
and
thickener
o Citric
acid:
preservative,
antioxidant,
pH
control
agent
o Gelatin:
stabilizer,
thickener,
texturizer
Heat
Transfer
Experiment
1. Secure
containers
of
similar
size
made
of
glass,
stainless
steel
and
pottery/ceramic
materials.
Each
should
have
a
lid.
Also
secure
oven
thermometer,
graduated
cylinder,
timer.
2. Heat
oven
to
400°F.
3. Add
same
amount
of
water
to
each
container
(approximately
2/3
full).
4. Check
and
record
temperature
of
water
in
each
container.
5. Place
one
container
with
water
in
center
of
oven
rack,
close
door,
and
allow
to
heat
for
10
minutes.
6. Pull
rack
½
way
out
of
oven
and
immediately
insert
thermometer
into
water
and
read.
Make
sure
thermometer
does
not
touch
container.
7. Record
highest
temperature.
8. Remove
from
oven,
close
door,
and
allow
oven
to
return
to
temperature.
9. Repeat
with
other
containers.
Material
of
Container
Before
temperature
Temperature
after
10
minutes
in
oven
Glass
Aluminum
Pottery
Questions:
1. Which
pan
heated
water
the
fastest?
Aluminum
2. How
does
heat
reach
the
baking
utensil
in
oven?
Convection
3. How
is
heat
transferred
from
hot
air
to
utensil?
Conduction
4. How
is
the
transfer
of
heat
affected
by
each
kind
of
material?
Conductors
Gelatinization,
Paste,
Retrogradation,
Syneresis
• Gelatinization:
the
increase
in
volume,
viscosity,
and
translucency
of
starch
granules
when
they
are
heated
in
a
liquid
Retrogradation:
the
seepage
of
water
out
of
an
aging
gel
because
of
the
contraction
of
the
gel
(bonds
tighten
between
the
amylose
molecules)
o Also
known
as
syneresis
or
weeping
Experiment
for
Comparison
of
Starches
1. Secure
the
following
ingredients:
2
T
cornstarch,
2
T
flour,
1
½
T
tapioca
Equipment
needed
includes
3
sauce
pans,
6
custard
cups,
timer,
graduated
cylinder,
thermometer.
In
all
experiments,
measure
the
temperature
when
starch
paste
was
completed.
2. Measure
and
place
237
ml
tap
water
in
small
heavy
aluminum
saucepan.
3. Add
the
2
T
cornstarch
stirring
constantly.
Stir
until
smooth.
4. Place
over
direct
heat;
stir
continuously;
turn
heat
to
low
and
cook
for
5
minutes.
Cornstarch
must
reach
near
boiling
temperature
for
thickening
to
occur.
Measure
temperature
when
solution
is
thickened.
5. Divide
the
starch
solution
between
2
custard
cups.
Freeze
1
of
the
custard
cups
that
will
be
thawed
and
evaluated
later.
6. For
experiment
2,
follow
same
steps
for
cornstarch
but
replace
the
cornstarch
with
2
T
(14
g)
flour.
7. Divide
the
starch
solution
between
2
custard
cups.
Freeze
1
cup
that
will
be
thawed
and
evaluated
later.
8. For
experiment
3,
weigh
1
½
T
(14.3
g)
tapioca
and
place
in
237
ml
of
water.
Let
it
stand
and
soak
for
15
minutes.
Use
timer.
9. After
soaking
period,
place
the
saucepan
on
the
direct
heat.
10. Continuously
stir
as
the
solution
reaches
boiling.
Once
boiling
is
reached,
remove
immediately
from
the
heat.
11. Divide
the
solution
between
the
2
custard
cups.
Place
once
custard
cup
in
freezer
until
frozen.
It
will
be
thawed
and
evaluated
later
in
the
lab.
12. Turn
the
cooked
starch
upside
down
on
a
small
dish
for
evaluation.
13. Rate
transparency
from
1=
most
transparent
to
10=
most
opaque;
1=
thickest
and
10=
thinnest.
14. Fill
out
chart.
Thickening
Pasting
Thickness
Transparency
Consistency
Agent
Temperature
of
Cooked
Following
Mixture
Freezing
and
Thawing
Cornstarch
Flour
Tapioca
Questions:
1. Why
is
the
gel
made
with
flour
slightly
softer
than
the
gel
made
with
cornstarch?
Cornstarch
has
more
amylose
which
makes
a
more
solid
gel.
2. Which
starch
gels
showed
syneresis?
The
most?
The
least?
Tapioca=most,
flour=
least
3. Describe
the
difference
between
the
cooked
and
frozen
starch
gels.
•
4. Which
frozen
gel
exhibited
the
best
texture?
5. Why
was
the
tapioca
soaked?
It
softens
the
amylopectin
6. What
should
be
the
process
for
cooking
a
cherry
pie
that
has
tapioca
as
the
thickening
agent?
Cross‐linked
starch
to
prevent
syneresis.
Eggs
and
Egg
Foams
• Factors
affecting
the
stability
of
an
egg
foam:
o Beating
technique,
temperature,
type
of
bowl,
careful
separation
of
yolks
and
whites,
whether
or
not
sugar,
acid,
fluid
or
salt
have
been
added
Experiment:
Effect
of
Stage
of
Beating
on
Quality
of
Egg
White
Foam
1. Secure
4
eggs,
6
T
sugar,
baking
sheet,
parchment
paper,
5
timers,
½
cup
measuring
cup,
4
glass
funnels,
4
graduated
cylinders,
electric
hand
beater,
4
small
pyrex
bowls,
spatula,
egg
separator,
2
measuring
cups
2. There
are
4
variations
of
foams
with
different
amounts
of
sugar
in
this
experiment.
Use
1
egg
white
for
each
variation.
Variation
1:
Add
2
T
sugar
to
one
egg
white.
Beat
until
peaks
have
a
slightly
rounded
top.
Variation
2:
Beat
the
egg
white
to
foamy
stage,
then
add
2
T
sugar
and
continue
to
beat
until
peaks
have
slightly
rounded
top.
Variation
3:
Beat
egg
white
until
stiff
peaks
are
formed;
add
2
T
sugar
and
beat
until
sugar
has
been
incorporated.
Variation
4:
Beat
egg
white
until
stiff
peaks
are
formed.
DO
NOT
ADD
SUGAR.
3. Time
the
beating
time
for
each
foam.
4. Measure
the
total
volume
of
each
foam
before
separating
to
measure
leakage.
5. Immediately
after
each
variation
is
made,
place
½
cup
of
foam
in
a
mound
on
a
baking
sheet
line
with
parchment
paper
that
is
labeled
as
to
variation.
6. Measure
another
½
cup
foam
and
place
it
in
a
glass
funnel
that
is
place
on
top
of
a
graduated
cylinder
to
check
for
leakage.
Time
the
beginning
of
each
foam
place
in
a
funnel
separately.
7. At
this
point,
all
4
variations
should
be
draining
with
timing
being
monitored.
8. Place
the
baking
sheet
with
the
4
labeled
foams
in
the
oven
to
bake
for
5‐7
minutes
at
375°F
until
a
golden
brown.
9. Remove
from
oven
and
allow
to
cool
for
20
minutes.
Read
drainage
in
graduated
cylinders
and
record
leakage.
Record
results
in
chart
below.
Variation
Beating
Time
Evaluation
of
peak
Leakage
(ml)
and
foam
1
2
3
4
What
constituents
in
egg
white
contribute
to
its
foam‐forming
ability?
Protein
Compare
beating
times,
volume,
leakage,
and
baked
meringues.
How
did
the
addition
of
sugar
affect
the
egg
white
beaten
to
the
stiff
peak
stage?
Makes
it
more
stable
What
did
the
absence
of
sugar
have
upon
the
beaten
egg
white
when
it
was
baked?
More
air,
less
brown
What
appears
to
be
the
optimum
stage
for
adding
sugar
to
beaten
egg
white?
Beginning
Milk
Proteins
• Coagulate:
to
clot
or
become
semi‐sold.
In
milk,
denatured
proteins
often
separate
from
the
liquid
by
coagulation.
o Lowering
the
pH
in
the
milk
or
adding
heat
denatures
proteins;
adding
an
acid
can
drop
the
pH.
Teachers:
you
can
create
an
experiment
to
show
milk
coagulation
using
heat
and
an
acid.
Heat
milk
in
a
saucepan
on
a
stove
and
have
students
evaluate
the
scum
and
coagulation
of
the
milk.
You
can
add
vinegar
or
lemon
juice
to
milk
and
measure
the
pH
before
and
after
adding
the
acid.
Have
students
observe
the
consistency/coagulation
of
milk.
Forming
a
cream
foam:
factors
affecting
this
are
temperature,
amount
of
fat,
acid,
sugar
• Foams
that
are
colder
and
are
higher
in
fat/sugar
will
form
a
more
stable
foam
• Acid
will
interfere
with
the
stability
of
a
foam
Teachers:
you
can
create
an
experiment
in
which
students
whip
cream
and
evaluate
the
stability
of
the
foam
formed
• Use
different
creams
with
different
fat
percentages,
at
different
temperatures,
add
acid
to
one
and
you
can
compare
the
foams
to
commercial
whipped
topping
*Lab
experiments
from
NTR
107L
Food
Science
Laboratory
Workbook
by
Margaret
E.
Briley,
PhD,
RD,
LD

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