Name: _____________________
FDSC 400: Exam 2
Answer all questions. There are only 50 min available for this exam so make an
effort to work quickly and answer all questions.
Question 1
8
Points
available
Points
gained
2
3
4
5
6
7
8
9
10
11
12
13
14
15
4
2
8
6
2
6
10
12
2
6
6
4
6
14
1) What are the substrates for the following enzymes? (2 points each, 8 total)
(a) Lipoxygenase
POLYUNSATURATED FATTY ACIDS
(b) Amylase
STARCH
(c) Polyphenoloxidase
PHENOLS
(d) Protease
PROTEINS
2) Why is enzymatic browning unimportant during the roasting of cocoa beans? (4
points)
NOT COVERED YET IN 2004
3) The Maillard reaction is nutritionally significant largely because of its effect on which
amino acid? (2 points)
NOT COVERED YET IN 2004
4) A potato processor is concerned that her potato flakes are an undesirable golden
brown color as soon as they are produced. The potatoes are peeled, steam-cooked,
mashed then dried on heated drums. Her proposed solution is to conduct the drying
under a nitrogen atmosphere to limit oxidation.
(a) What do you think is the most likely mechanism of browning (2
points)
NOT COVERED YET IN 2004
(b) Do you think her solution is likely to be effective? Why? (6 points)
NOT COVERED YET IN 2004
5) Indicate whether the following sugars are reducing or non-reducing? (2 points each, 6
total)
R
R
NR
6) The following shows a segment of a polypeptide chain. Mark the bond(s) where the
chain backbone is most free to flex and bend? (2 points)
(DOUBLE BONDS FROM THE CARBONYL RESONATE INTO THE
CHAIN)
7) In the context of protein folding, briefly explain the meaning and importance of
solvent entropy. (6 points)
SOLVENT ENTROPY IS ANOTHER TERM FOR HYDROPHOBICITY.
UNFOLDING THE PROTEIN IS UNFAVORABLE AS IT WOULD EXPOSE MORE
HYDROPHOBIC AMINO ACIDS TO WATER
deformation
8) A flour improver is added to bread dough to increase the number of inter-protein
disulfide bonds present. The effect of the additive is tested in a creep test where a
force is applied to a sample of dough, held then released and the deformation
measured as a function of time.
(a) On the following axes, sketch the creep curves (deformation as a
function of time after the applied force is removed) for the original
recipe and for the modified dough. (6 points)
time
(b) Briefly explain which dough you would prefer for stamping out
intricately detailed cookies. (4 points)
NOT COVERED YET IN 2004
9) The following graph is taken from a paper where the authors measured the effective
particle size (d32) of a whey protein isolate stabilized emulsion heated to different
temperatures at different salt concentrations (i.e., ionic strength).
(a) Estimate the denaturation temperature of whey protein isolate (2
points)
ABOUT 70°C. (AT THIS TEMPERATURE THE PROTEINS AT THE
DROPLET SURFACES BEGIN TO UNFOLD AND ALLOW THE
EMULSION DROPLETS TO AGGREGATE
(b) Sketch a cartoon of the emulsion droplets before heating and after
heating to 80°C. Show as much appropriate detail as possible. (6
points)
(c) Fill in the gaps in the following sentence (4 points):
“___pH_______ affects the magnitude of electrostatic forces while
___salt______ affects the rate at which they diminish with distance”
DVLO THEORY – NOT COVERED IN 2004
10) True or false: Van der Waal’s forces are always attractive. (2 points)
TRUE
11) Why don’t the following cookies go brown? (6 points)
Ingredients: 2 1/2 cups flour, 1 1/2 tsp baking powder, 3/4 tsp salt, 1 tsp cinnamon,
1 cup sugar, 3/4 cup vegetable oil, 2 eggs, 1 tsp vanilla, sugarDirections: Sift
together flour, baking powder, salt and cinnamon. In a separate bowl, combine
sugar and oil. Add to the second mixture the eggs and vanilla. Add the flour mixture
all at once and beat well. Shape the dough into 1/2 inch balls. Flatten the balls as
thin as you can between lightly floured hands. (To give a corrugated effect, score
them in parallel lines with a fork dipped in flour.) Sprinkle with granulated sugar.
Bake about 10-12 minutes on a lightly greased cookie sheet.
NOT COVERED YET IN 2004
12) Why is the Maillard reaction faster in French fries rather than boiled potatoes (2
reasons)? (6 points)
NOT COVERED YET IN 2004
13) A company has traditionally made a rich, meat-flavored bouillon by heating a mixture
of proteins and sugars. More recently they have tried to make a modification of their
recipe by adding some Balsamic vinegar to the mixture (perhaps to create a low pH,
Italian-style product). Unfortunately the meat flavor is very weak in the new product.
Why? (4 points)
NOT COVERED YET IN 2004
14) The following diagram is a Rosanoff projection of glucose. How many chiral carbons
does it have? How many optical isomers does it have? (6 points)
24
15) Define the following terms. (2 points each, 14 total)
(a) Hydrophobic effect
THE ATTRACTION BETWEEN HYDROPHOBIC MATERIAL PLACED IN
WATER. or THE STRONG ATTRACTION OF WATER WITH ITSELF WHICH
MAKES IT DIFFICULT TO BRONG NON-POLAR MOLECULES INTO SOLUTION
(b) Physicochemical
A COMBINATION OF PHYSICAL AND CHEMICAL PROPERTIES OF A
MATERAL
(c) Shear-thinning
WHEN A LIQUID BECOMES LIQUID AS IT IS STIRRED. IN THE CONTEXT OF
THE PAPER, FLOCCULATED EMULSIONS WERE BROKEN DOWN BY THE
FORCE OF MIXING (THE REACTION IN 9B IN REVERSE) MAKING THE
SAMPLE LESS VISCOUS.
(d) Protein hydrolysis
THE BREAKDOWN OF PROTEIN PRIMARY STRUCTURE BY WATER BEING
ADDED ACROSS PEPTIDE BONDS
(e) Protein denaturation
UNFOLDING OF THE NATIVE CONFORMATION. BREAKDOWN OF
SECONDARY OR TERTIARY STRUCTURE.
(f) Protein primary structure
THE LINEAR SEQUENCE OF AMINO ACIDS
(g) Thiol-disulfide interchanges
THE REACTION OF A THIOL GROUP ON ONE PROTEIN WITH THE DISULFIDE
BOND IN ANOTHER PROTEIN TO MAKE A NEW DISULFIDE BOND AND A
NEW THIOL.
S
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