Food Chemistry Flashcards
(128 cards)
1
Q
What compound in chocolate stimulates the central nervous system and also makes dogs sick?
A
Theobromine
2
Q
What chemical hormone do fruits release upon ripening?
A
Ethylene
3
Q
Chlorophyll molecule reacting with hydrogen exhibits what shade of green?
A
Olive Green
4
Q
What two common compounds are used together as an antioxidative system?
A
Ascorbic Acid and Citric Acid
5
Q
What is the name of the final degradation compound of chlorophyll?
A
Pheophorbide
6
Q
What is an isomer that is cheaper than Vitamin C?
A
Erythorbic Acid
7
Q
What is the enzyme responsible for browning in apples and lettuce?
A
Polyphenol Oxidase
8
Q
What are the acids present in fish oil?
A
Arachidonic Acid, DHA, and EPA
9
Q
What is surimi?
A
A concentrate of microfibrillar proteins of fish muscle.
10
Q
What is Carboxyl-methyl cellulose often used for?
A
Thickener in foods (and stabilizer)
11
Q
Does Kosmotrope ion discourage water structure?
A
No (they cause water molecules to favorably interact)
12
Q
What is the main class of color compounds found in raspberries?
A
Anthocyanins
13
Q
What is the major color compound in tomatoes?
A
Lycopenes
14
Q
What is the structural difference between chlorophyll and chlorophyllide?
A
Chlorophyllide does not have a phytol tail
15
Q
What happens to chlorophyll on heating?
A
Pheophytin forms
16
Q
Alar is the trade name for what chemical compound?
A
Daminozide
17
Q
How many polypeptide chains make up an antibody?
A
Four
18
Q
What is the winterization process for an oil?
A
Cooling the oil and filtering of the solids formed so that long chained saturated fats do not crystallize at low temperatures.
19
Q
What is the structural difference between chlorophyll and pheophytin?
A
Pheophytin does not have magnesium in porphyrin ring.
20
Q
Peptide bond formation results in the formation of what secondary compound?
A
Water
21
Q
What metabolic end product does the Voges-Proskauer test detect?
A
Acetoin in a baceterial broth culture
22
Q
Will lipid oxidation be higher at a water activity of .05 or .5?
A
0.05
23
Q
How many carbon atoms and how many double bonds are there in arachidonic acid?
A
20 carbons and 4 double bonds
24
Q
What are the three stages of oxidative rancidity?
A
Initiation, Propagation, and Termination
25
What ketohexose is most significant to food chemists?
Fructose
26
How many carbon atoms are there in the fatty acid myristic acid?
14
27
What is the Peroxide Value a measure of?
Fat Oxidation
28
Waxes are composed of what two basic chemical entities?
Fatty Acid (Ester linked) to Fatty Alcohol
29
Name three effects of protein denaturation.
```
Decreased solubility
altered water-binding capacity
loss of biological activity,
increased susceptibility to attack by proteases
increased intrinsic viscosity,
inability to crystallize.
```
30
Name 3 physical agents capable of denaturing proteins.
```
Temperature Changes Mechanical Actions
Change in pH
Irradiation
Sound Waves
Exposure to Mineral Salt and Metals
```
31
Name two main gluten proteins.
Gliadins and Glutenins
32
How do sodium chloride and sucrose affect foam stability?
Sodium chloride reduces foam stability and sucrose improves foam stability.
33
Name three factors useful in controlling enzyme activity.
```
Temperature
Water Content and Activity
Extremes of pH
Chemicals
Alterations of Substrates
Alterations of Products
Preprocessing Controls
```
34
Name 3 chemical agents capable of denaturing proteins.
```
Acids
Alkalis
Metals
Organic Solvents
Aqueous Solutions of Organic Solvents
```
35
Name 5 proteins with good foaming properties.
```
Egg white proteins
the globin part of hemoglobin
bovine serum albumin
gelatin
whey proteins
casein micelles
B-casein
wheat protein
soy proteins
some protein hydrolyzates.
```
36
Name 3 reasons it is advantageous to obtain enzymes from microorganisms.
Microorganisms are very versatile,
MO's can be altered by mutations or genetic engineering to produce a greater quantity of enzyme or different enzymes,
recovery of enzymes is often easy,
readily available,
high rate of growth and enzyme production.
37
What effect would the addition of sodium bicarbonate have to chocolate?
Smoother,
less acid and less bitter chocolate flavor,
darker color,
and improved solubility (elevated pH enhances sugar-amino browning reactions and polymerization of flavonoids).
38
Name 5 chelating agents used in the food industry.
```
EDTA,
citric acid,
malic acid,
tartaric acid,
oxalic acid,
succinic acid,
adenosine triphosphate,
pyrophosphate,
porphyrins,
and proteins.
```
39
Name 2 heat stable enzymes in food that are important to the quality of aseptic products.
```
Lipase,
lipoxygenase,
catalase,
chlorophylase,
peroxidase,
pectinase,
protease,
ascorbic acid oxidase,
alkaline phosphotase.
```
40
Chlorophyll molecule reacting with magnesium shows what shade of green
Bright green
41
At low water activity what is the main deteriorative concern?
Lipid oxidation
42
Name one way foam stability can be assessed.
The degree of liquid drainage or foam collapse (foam reduction) after a given time,
the time for total or half-drainage (or half-reduction in volume),
or the time before drainage starts.
43
Name 4 advantages of using enzymes in food processing.
```
They are natural, nontoxic substances,
generally catalyze without unwanted side-effects, active under very mild conditions of temperature and pH,
active at low concentrations,
rate of reaction can be controlled,
can be inactivated after reaction.
```
44
S-(1-propenyl)-L-cysteine sulfoxide is the chemical precursor to the major flavor compounds in what foodstuff?
Onions ( or leeks)
45
What kinds of food emulsions are? (1) Butter (2) Mayonnaise(3) Milk
```
Butter= water in oil Mayonnaise= oil in water
Milk= oil in water
```
46
What is the fundamental driving of electrophoresis?
The speed of a molecule is proportional to the surrounding voltage gradient.
47
How can a molecular weight of protein, DNA, and RNA be determined?
For proteins: SDA-PAGE.
| For DNA & RNA: Agarose gel.
48
How does HPLC differ from FPLC?
HPLC has higher pressure than FPLC
49
What are two common reducing agents that break disulfide bonds in proteins?
2-mercaptoethanol (2-ME),
| dithiothreitol (DDT)
50
In polyacrylamide gel electrophoresis (PAGE) what purpose do ammonium persulfates (APS) and TEMED serve?
They act as catalysts, speeding the polymerization of acrylamide.
51
What does the acronym NPN stand for?
Non-protein nitrogen
52
Name three nonpolar polar, and charged amino acids.
Nonpolar: (Valine, Alanine, Leucine, Isoleucine, Proline, Tryptophan)
Polar: (Glycine, Serine, Cystein, Threonine, Tyrosine)
Charged: (Lysine, Arginine, Histidine, Aspartic Acid, Glutamic Acid)
53
What name is given to the small circular DNA molecules that carry genetic information independently of the main bacterial chromosome?
Plasmids
54
In genetics what is conjugation?
DNA transferred by cell to cell contact (bacterial sex).
55
Which will be coldest at its freezing point: 1M dispersion of amylose 1M solution of NaCl, distilled water, or 1M solution of sucrose?
NaCl (it dissociated to a 2M solution)
56
What metabolic disorder prevents conversion of phenulalanine to tyrosine by normal metabolic pathways?
Phenylketonuria
57
What does MSG stand for?
Monosodium Glutamate
58
What happens to a bottle of wine if before you bottle it you forget to put the stuff in it that prevents it from fermenting?
It explodes
59
If you take 20 ml of .1 M NaOH to titrate 40 mL of an HCL solution to the penolphthalein end point what is the molarity of the HCL solution?
.05 M HCL
60
What does the "c" stand for in the equation E=mc2?
Speed of Light
61
20 grams of amylose is added to 80 grams of water in a beaker; the boiling point is measured with an ordinary mercury-in-glass thermometer. What is the observed boiling point of the material in the beaker?
100 Degrees Celsius (it is not a true solution-there is no boiling point of elevation)
62
If oxygen attacks an unsaturated fatty acids at the double bond what is the resultant product?
Two aldehydes
63
In the enzyme Taq Polymerase what does Taq stand for?
Thermus Aqauticus
64
What are the primary secondary, tertiary, and quaternary structures?
Primary-amino acid sequence. Secondary-alpha-helix, beta sheet. Tertiary-one complete protein chain with cross bonds linking it together. Quaternary-four separate protein chains assembled as one.
65
Define molarity, molality, and normality.
Molarity is moles of substance per liter solution. Molality is moles of substance per kg solvent. Normality is equivalents of substance per liter solution.
66
How is pH defined?
Negative log of the hydrogen concentration (mol/l).
67
What charge will a protein have when the pH of its solution is below, at, and above its pKa?
pH below positive charge; pH at no charge; pH above negative charge
68
What does the iodine value measure and how is it measured?
pH below positive charge; pH at no charge; pH above negative charge
69
What does the iodine value measure and how is it measured?
The amount of unsaturated bonds in fat; grams Iodine reacting with 100 grams fat.
70
What does the saponification value measure and how is it measured?
Number of fatty acids present; mg KOH needed to saponify 1 g fat.
71
What does Acid Degree Value measure and how is it measured?
Amount of free fatty acids present; mg KOH needed to neutralize the free fatty acids in 1 g of fat.
72
Water A) Is the major component of most foods.B) Controls shelf-life or storage capabilityC) Regulates chemical and microbiological reactionsD) All of the above
D) All of the Above
73
Which of the following foods contain the lowest content of water?A) Fresh Carrots B) Fresh Tomatoes C) Whole Milk D) Fresh Celery
C) Whole Milk
74
Which of these food additives could be used to prevent cocoa particles from settling in chocolate milk? A) BHA (butylated hydroxyanisole B) Carrageenan C) Thiamine Hydrochloride D) Citric Acid
B) Carrageenan
75
Which of the following examples of browning is enzymatic in nature? 1. Browning of sugars as a result of heating 2. Browning of freshly cut surfaces of fruits and vegetables 3. Browning of bread during toasting 4. Browning of potato chips
Browning of freshly cut surfaces of fruits and vegetables.
76
What would be a safe processing time for heat processing green beans in a boiling water bath? A. 30 minutes B. 300 minutes C. Depends on the size of the food container D. None of the above
D: None of the above
77
Which of these foods is not appropriate to this list? A) Salami B) Yogurt C) Orange Juice D) Beer
A: Orange Juice
78
To which of the following four basic tastes are humans most sensitive? A) Bitter B) Sweet C) Sour D) Salty
Bitter
79
At what pH is benzoic acid most effective?
pH 3-5
80
What is acid proteolysis?
Degradation of protein and production of acid from sugar at the same time.
81
What is catalase?
An enzyme that converts hydrogen peroxide to water plus oxygen.
82
What reaction does the enzyme "reverse transcriptase" catalyze?
RNA transcribed to DNA
83
What pigment was first designated as anthocyanins?
Blue pigment in flowers
84
What is the chemical nature of anthocyanins?
Glycosides of anthocyanidins
85
Name a naturally occurring protein sweetener.
Thaumautin
86
What is the chemical nomenclature for caffeine?
1, 3, 7-trimethylxanthine
87
Name three non-nutritive sweeteners approved for use in USA?
Acsulfame-K, Saccharin, Succralose, Aspartame
88
Which two amino acids is the aspartame derived from?
Aspartic Acid and Phenylalanine
89
Are sorbitol and mannitol sweet?
Yes
90
What are the fructose contents in commercial HFCS products.
45%, 52%, 90%
91
What are the limiting amino acids in corn, potato, and green peas?
Corn- Lysine, Potato-Methionine, Green Peas-Methionine
92
Which amino acid has the greatest molecular weight: tryptophan or tyrosine?
Tryptophan
93
Give one word for a carbon atom involved in hemiacetal or acetal formation.
Anomeric
94
What degradative enzyme causes browning in apples, pears, bananas, and peaches?
Polyphenoloxidase
95
Name the two components that comprise the relaxing factor in muscle fibers.
Troponins and Tropomyosin
96
An emulsifier with a high hydrophilic-lipophilic balance (HLB) value would promote which type of emulsion: oil in water or water in oil?
Oil in Water
97
What is the protein efficiency ratio (PER) of casein?
2.5
98
What two enzymes degrade pectic substances?
Pectin methylesterase & polygalacturonase
99
Match the number of carbon atoms with the common name of these saturated fatty acids. Carbon #: 4:0 10:0, 12:0,14:0, 16:0, 18:0Common Name: Myristic, Butyric, Capric, Lauric, Stearic, Palmitic
4:0 (Butyric), 10:0 (Capric), 12:0 (Lauric), 14:0 (Myristic),16:0 (Palmitic), 18:0 (Stearic)
100
What is a polymorphism?
Solid phases of the same chemical composition that differ by crystalline structure, but yield identical liquid phases upon melting.
101
Name 3 factors influencing the consistency of commercial fats.
Proportion of solids in the fat, number, size, and kinds of crystals, viscosity of the liquid, temperature treatment, and mechanical working.
102
What does HLB stand for and what does a high and low HLB value indicate?
HLB (hydrophilic-lipophilic balance); a low value (3-6) promotes water in oil emulsions and a high value (8-18) promotes oil in water emulsions.
103
Name 3 factors influencing the rate of lipid oxidation in foods.
Fatty acid composition, free fatty acids versus the corresponding glycerols, oxygen concentration, temperature, surface area, moisture, pro-oxidants, antioxidants
104
Name two reasons why fats are hydrogenated.
It allows the conversion of liquid oils into semisolid or plastic fats and it improves the oxidative stability of the fat.
105
Name three compounds capable of poisoning the catalyst during commercial hydrogenation.
Phospholipids, water, sulfur compounds, soaps, partial glycerol esters, carbon dioxide, and mineral acids.
106
Name the three positively charged amino acids.
Lysine, Arginine, and Histidine
107
If the absorption of a sample is being determined spectrophotometrically at 420 nm what color is the sample?
Blue/purple
108
What enzyme is most responsible for browning bananas?
Polyphenol Oxidase
109
During freezing what are the two stages in the crystallization process?
Nucleation or crystal formation and crystal growth.
110
In what food is butyric acid typically found?
Milk
111
What is the name given to a mixture of equal parts of Darel Lisomers?
Racemic Mixture
112
What enzyme causes hyrolytic rancidity in milk?
Lipase
113
Name two enzymes that are involved in softening fruits.
Pectin Esterase, Polygalacturonase, Pectin Layase
114
Name the strongest biochemical bond and the weakest biochemical bond.
Covalent (strongest) and Hydrophobic (Weakest)
115
What is the enzyme that softens tomatoes?
Pectin Esterase
116
Name a commonly used household chemical leavening agent and the gas it generates.
Sodium bicarbonate generates CO2
117
Name two non-enzymatic browning reactions.
Carmelization and Maillard
118
What are the three main steps in the autooxidation of lipids?
Initiation, Propagation, Termination
119
What are the only phenols approved for use in the microbiological preservation of foods?
Parabens
120
What is the common name for 9 12, cis-cis-octa dienoic acid?
Linoleic Acid
121
What are 3 mesomorphic structures associated with lipids in the liquid state?
Lamellar; Hexagonal I, II; Cubic
122
What are proteins which are soluble in 50-80% ethanol known as?
Prolamines
123
What are colloids that are stabilized by a layer of solvation called?
Emulsoids
124
What are soluble polymers of anhydro-galacturonic acid and its esters called?
Pectins
125
What is the geometric configuration of double bonds in most natural fatty acids?
Cis
126
The undesirable clarification of orange juice or tomato juice (precipitation of pulp) is caused by what enzymes?
Pectin methyl esterase or galacturonase
127
What is the movement of molecules through a semi permeable membrane from a region of low to high solute concentration called?
Osmosis
128
What is the name of the structural carbohydrate found in lobsters crab, shellfish, and insects?
Chitin
