Transcript Food_Science_Angie_updated

Chemistry of Food
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a. Identify the sources of and understand the role of lipids,
carbohydrates and proteins typically found in cookies, and use
tests to identify these compounds, including the Benedict’s,
Iodine and Brown Bag tests.
b. When given samples of sweeteners, use the Benedict’s test
to identify reducing sugars.
c. When given samples of cupcake ingredients, use the Biuret
test to identify and rank the ingredients by protein content.
d. When given formulations, processes, and finished
cupcakes, identify the error in the cupcake formulation and/or
process used.
e. Use standard labeling regulations to produce a label from
information given.
f. Determine the moisture loss and density of cupcakes.
g. Identify leavening agents using chemical tests, and
understand the role of the leavening agents in baked
cupcakes.
Ingredients
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The right ingredients
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Liquids….
Lipids
Leavening agents
Flours
Sweeteners
Must understand WHY you are using the
ingredient…what function does it provide?
Teams are limited to listed ingredients
Carbohydrates
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Carbohydrates
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Cox(H2O)y carbon along with
hydrogen and oxygen in the
same ratio as water
Basic unit – monosaccharide
Multiple units –
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disaccharide (2)
trisaccharide (3)
oligosaccharide (2-10)
polysaccharide (>10)
Carbohydrates
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Sugars
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Monosaccharides
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Glucose, Fructose
Disaccharides
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Lactose (glucose
and galactose) milk
Maltose (glucose
and glucose) Sucrose (glucose
and fructose –table
sugar
Reducing sugars
Examples: glucose, lactose,
fructose
Non-reducing sugar contains
no hemiacetal groups.
Example: sucrose
Carbohydrates
Polysaccharides
 Examples:
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starch - glucose polymers, found in plants
cellulose –found in plant fibers, insoluble
Pectin-units are sugar acids rather than simple
sugars, found in vegetables and fruits
Branched vs. linear
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Starches are a mixture of branched (amylopectin) and
linear (amylose) polysaccharides
Tests for carbohydrates
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Benedicts test for sugars
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Iodine test for starch
Positive
Reaction
Benedict’s Test
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The Benedict's test allows us to detect the presence of
reducing sugars (sugars with a free aldehyde or ketone
group). All monosaccharides are reducing sugars. Some
disaccharides are also reducing sugars. Other disaccharides
such as sucrose are non-reducing sugars and will not react
with Benedict's solution. Starches are also non-reducing
sugars.
The copper sulfate (CuSO4) present in Benedict's solution
reacts with electrons from the reducing sugar to form cuprous
oxide (Cu2O), a red-brown precipitate.
The final color of the solution depends on how much of this
precipitate was formed, and therefore the color gives an
indication of how much reducing sugar was present if a
quantitative reagent was used.
With increasing amounts of reducing sugar the result will be:
green yellow orange red
Iodine Test
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The Iodine test is used to test for the
presence of starch.
Iodine solution – Iodine is dissolved in an
aqueous solution of potassium iodide reacts with starch producing a deep blueblack color.
Although the exact chemistry of the color
change is not known, it is believed that
the iodine changes the shape of the starch
to change the color
Lipids
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Present as fats extracted from plants or
animals (butter, vegetable oil) or as
constituents of food (chocolate)
Contributions to foods: texture and flavor
Contain only Carbon, hydrogen and
oxygen
Most common form for lipid in foods is as
a triglyceride
What difference in texture would you see
substituting vegetable shortening or
vegetable oil for butter in the formulation?
Saturated Lipids (Fats)
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Saturated fats have
no double bonds in
any of the fatty acid
chains in the
triglyceride hence it is
saturated with
hydrogen.
Considered not heart
healthy
Food
Lauric
acid
Myristc Palmitc Stearic
acid
acid
acid
Coconut oil
47%
18%
9%
3%
Butter
3%
11%
29%
13%
Dark
chocolate
0%
0%
34%
43%
Eggs
0%
0.3%
27%
10%
Soybean oil
0%
0%
11%
4%
Unsaturated Fats (Lipids)
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Have one
(monounsaturated) or
more (polyunsaturated)
carbon chains
This means there are one
or more double bonds in
the chain
Lipids
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http://www.wellsphere.com/he
althy-cooking-article/butter-vsshortening-in-baking/156136
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Conversion between
solid structure to a
liquid state is called
the melting point
How would changing
the melting point of
the lipid used change
the cookie texture?
Brown Bag Test
Proteins
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Proteins are made up of amino acids
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essential and nonessential
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Contains Nitrogen
Protein can be found in the flour, egg and
milk as well as other ingredients.
Proteins
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Biuret Test
The Biuret Reagent is made of
sodium hydroxide and copper
sulfate. The blue reagent turns
violet in the presence of
proteins, and the darker the
purple color, the more protein
is present.
Biuret’s Reagent is unstable,
but can be mixed on the spot
using NaOH & Benedicts
Leavening agents
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Used to produce a gas that
'lightens' dough or batter.
used to raise baked goods.
water a leavening agent (pie
crusts, some crackers)
air incorporated into batter (angel
and sponge cakes)
expand when heated and cause
the raising of the dough or batter
when gas is trapped in matrix of
gluten and starch from flour
Leavening agents
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Baking soda
 -NaHCO3
 Needs moisture plus an acid
source such as vinegar, citrus juice,
sour cream, yogurt, buttermilk,
chocolate, cocoa (not Dutchprocessed), honey, molasses (also
brown sugar), fruits or maple syrup to
react
 used to neutralize acids in foods
 around 4 times as strong as baking
powder
 can cause soapy flavor in high
amounts
Leavening agents
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Baking powder
 NaHCO3 plus acidifier(s) and drying agent (usually an
acid salt and cornstarch)
 can cause acidity and/or bitter off-flavor
 two acidifiers used in double acting to produce CO2 in
two steps
 Reacts when moistened and also reacts when heated
 double-acting is the only commercial baking powder
available today.
Standard Recipe
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2 1/4 cups flour
1 1/3 cups sugar
3 teaspoons baking powder
1/2 teaspoon salt
1/2 cup shortening
1 cup milk
1 teaspoon vanilla
2 large eggs
Effect of Ingredients
Batch #
Flour
Leavening agent
1
2 ¼ cups
2
Sweetener Liquid
Egg
lipid
Salt
Vanilla
cup
3 tsps. baking powder 1 1/3 Cup 1
milk or
sub.
2 large or
substitute
none
½ tsp. 1 tsp.
2 ¼ cups
3 tsps. baking powder 1 1/3 Cup 1 cup
milk or
sub.
2 large or
substitute
3 Tbsp oil ½ tsp. none
3
2 ¼ cups
None
1 1/3 Cup 1 cup
milk or
sub.
2 large or
substitute
3 Tbsp oil ½ tsp. 1 tsp.
4
2 ¼ cups
3 tsps. baking soda
1 1/3 Cup 1 cup
milk or
sub.
2 large or
substitute
3 Tbsp oil ½ tsp. 1 tsp.
5
2 ¼ cups
cup
3 tsps. baking powder 1 1/3 Cup 2
milk or
sub.
2 large or
substitute
3 Tbsp oil ½ tsp. 1 tsp.
6
2 ¼ cups
3 tsps. baking powder 2 1/3 Cup 1 cup
milk or
sub.
2 large or
substitute
3 Tbsp oil ½ tsp. 1 tsp.
Mixing Technique
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Incorporate
ingredients
Hydrate dry
ingredients
Experiment set 2
explores the best
method to mix the
batter
Standard Mixing
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Preheat oven to 350 degrees. Line cupcake pans with paper
liners.
Combine flour, sugar, baking powder, and salt in a large
mixing bowl. Add shortening, milk, and vanilla. Beat for 1
minute on medium speed. Scrape side of bowl with a spatula.
Add eggs to the mixture. Beat for 1 minute on medium
speed. Scrape bowl again. Beat on high speed for 1 minute
30 seconds until well mixed.
Spoon cupcake batter into paper liners until 1/2 to 2/3 full.
Bake for 20 to 25 minutes or until toothpick inserted in center
comes out clean.
Cool 5 minutes in pans then remove and place on wire racks
to cool completely.
Mixing Technique
Batch # Step 1
Step 2
Step 3
Step 4
Add egg. Use spoon to
stir for 1 minute
1
Mix dry
ingredients
together
Add liquid
ingredients
Using spoon,
stir
ingredients for
30 seconds
2
Mix dry
ingredients
together
Add liquid
ingredients
Pour into
Add egg. Use mixer or
blender or use blender to blend for 1
hand mixer and minute
blend or mix 2
minutes
3
Mix dry
ingredients
together
Add liquid
ingredients
Use whisk, stir
ingredients 1
minute
Add egg. Use whisk, stir
ingredients 2 minutes
Viscotester
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Made from 8 oz Styrofoam cup
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Heat 16 penny nail with tea candle for ~1 minute
(or until it gets too hot to hold)
Punch hole from INSIDE into center bottom of cup
Place tape over hole
Time how long it takes for same amount of each
standard liquid to break flow as it leaves
When determining how much fluid to use, keep a
couple of items in mind
 The larger the amount of fluid the less influence
reaction time will have on error.
 The amount of fluid the event supervisor is likely
to allow the team to have.
Standard Curve
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Use same amount of standard fluids to
calibrate
Time how long it takes to break stream
Standard Curve
Viscosity
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Students need to investigate viscosity of their
batters and compare to final results.
The resistance of a fluid to deformation.
Temperature dependent
*Dynamic or simple viscosity
Kinematic viscosity: ratio of viscosity/density
Shear viscosity – reaction to a shearing stress
(pumping, spraying, etc.)
Must know general nomenclature
Measuring Density
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Density Score Sheet
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Students should measure the density of
each of their experimental cupcakes and
record
Suggested Density
Suggested Score
.28-.329
5
.25-.279 or .32-.359
4
.21-.249 or .36-.389
3
.19-.209 or .319-.42
2
Less than .19 or greater
than .42
1
Nutrition
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Calorie - amount of heat required to raise the temperature of 1
gram of water 1 degree Celsius.
Kilocalorie (1000 calories) is the unit commonly used to represent
energy values of foods -or Calorie with a C instead of a c
Not all carbohydrates (or fats, or proteins) yield the exact same
amount of energy when burned in a calorimeter, so common
averages from studies (in kcal/g) are used
Carbohydrates average 4.1 kcal/gram in a bomb calorimeter, are
about 98% digestible and yield 4 kcal/g when consumed
Proteins average 5.7 kcal/g in a bomb calorimeter, are not as easily
digested and yield an average of 4 kcal/g when consumed
Lipids average 9.5 kcal/g in a bomb calorimeter, are 95% digested
and yield an average of 9 kcal/g when consumed
Fats (lipids) are the most concentrated source of food calories
Carbohydrates are the cheapest source of calories, proteins the
most expensive
Fiber
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Foods not digested by human digestive
system
Two types
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Soluble Fiber-helps regulate blood sugar
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Found in Oats & Oat Bran, some Fruits & vegys
Insoluble Fiber-helps clean out colon
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Found in whole wheat, some fruit skins and vegys
Nutritional labeling
1)
2)
Fill in the following blanks.
a) There are ___ Calories/gram of fat.
b) There are ___ Calories/gram of carbohydrate
c) There are ___Calories/gram of protein
d) There are ___Calories/gram of water
Use the nutritional label given for information to
answer the following questions:
a) Calculate the Calories in one serving of this
product.
(1) Calories from Fat
(2) Calories from Protein
(3) Total Calories in one serving
b) What percent of the carbohydrate Calories come
from fiber?
c) If the daily value of iron is 18 mg per day, calculate
the amount (in mg) of iron in one bar of this
product.
Attribute
Flavor
Aroma
Sensory Score Sheet
Score (Circle for each attribute listed)
Starch
1
Terrible
1
Raw or burned
4
OK
5
Very Pleasing
5
Very Pleasingly
cooked
5
Pleasant
Dairy/Milky
1
Spoiled
2
Under or over
cooked
2
Moderate off-flavor
1
Way too much or
too little
1
Way too much or
not enough
2
Moderately too
much or too little
2
Moderately too
much or too little
3
Slightly too sweet
or too tart
3
Slightly too much
or too little
4
About right
5
Perfect sweetness
4
About right
5
Excellent
Surface
1
Really rough
2
Somewhat rough
3
Moderately rough
4
Slightly smooth
5
Smooth
Moisture
1
Dry
2
Moderately dry
3
Somewhat dry
4
Somewhat moist
5
Moisture just right
Cohesiveness
1
Really gummy
2
Somewhat gummy
3
Slightly gummy
4
Falls apart easily
5
Just right
Stickiness
1
Really sticky
2
Moderately sticky
3
Somewhat sticky
4
Slightly sticky
5
Just right
Gritty
Oxidized (paint)
flavor
Sweetness
Vanilla
2
3
Average
3
Slightly under or
over cooked
3
Slightly off flavor
4
4
Pleasingly cooked
Texture
Circle any of the
following if
present
Sour
Bitter
Astringent