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Intro to Food Science > Exam 1 > Flashcards

Exam 1 Flashcards

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1
Q

What a dollar spent for food pays:

A

$0.23 - Farm Value
$0.77 - Food Processing

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2
Q

Food processing has 2 primary functions:

A

-convert inedible agricultural products into edible food
-preserve oversupply of agricultural products for later use

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3
Q

What 5 functions does the food industry perform today?

A
  1. provide quality foods
  2. preserve food
  3. provide safe food
  4. provide nutritious food
  5. process food
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4
Q

Food quality factors:

A
  1. Visual Perception
  2. Flavor
  3. Lots of other factors
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5
Q

Food Quality: Perception

A

-color
-size
-transparency
-shape

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6
Q

Food Quality: Flavor

A

-Taste
-Mouthfeel
-odor

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7
Q

Miscellaneous factors that influence food choices

A

-media pressure
-culture, tradition, ethnicity
-individual experience (lactose intolerance)
-religion
-geographic location
-convenience

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8
Q

What factors must processors take into consideration to preserve food?

A

-physical
-chemical
-biological

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9
Q

Control of Insects/Rodents

A

FDA established a maximum level of “filth”
ex: 5 fly eggs per 250 mL juice and 1 maggot per 50mL juice – anything above maximum can be seized

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10
Q

What are foods composed of?

A

composed of either pure chemical compounds or mixtures of chemical compounds

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11
Q

Chemistry

A

the study of properties, composition and structure of matter

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12
Q

Matter

A

anything that has weight and takes up space: solid, liquid, gas (water can be all 3)

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13
Q

What are atoms composed of?

A

protons, neutrons and electrons

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14
Q

Neutral atom

A

of protons = # of electrons

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15
Q

Atomic Mass (weight)

A

of protons + # of neutrons

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16
Q

Atomic Number

A

of protons

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17
Q

How many electrons does the outer orbital “want” to be complete?

A

8 valence electrons

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18
Q

Element

A

-a simple substance that consists of a single type
-element cannot be reduced to simpler forms by any routine chemical process
-111 elements have been discovered, but only 92 occur naturally

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19
Q

Most common elements in food:

A

H, C, N, and O

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20
Q

Compounds

A

-substances that contain 2 or more elements
-some atoms of certain elements are incapable of existing by themselves and are found in combination with elements of the same type: H2, O2
-this process forms a molecule

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21
Q

Molecule

A

-a molecule is the smallest particle of the compound that can exist and still retain the properties of the compound
-compounds are also made of unlike elements

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22
Q

Chemical reaction

A

-a process where substances are changed into different substances
-this a chemical change, not physical
- chemical bonds are broken and reformed to make new chemical bonds, to make new products

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23
Q

Mixture

A

not a chemical combination of elements, but a physical one

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24
Q

Formation of compounds

A

-can be fairly easy, or they can require a tremendous amount of energy
-common methods include: heating, dissolving in water and then heating
-some elements are very reactive, while other are unreactive or very stable

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25
Q

How are compounds formed?

A

Ionic Compound Formation: electrons are transferred from one compound to another
Covalent Compound: atoms share electrons instead of transferring ownership
-the atoms “share” the valence, so they are covalent ex: methane (CH4)

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26
Q

Organic Chemistry

A

-the study of covalent carbon compounds
-named “organic” because they were first discovered in living organisms
-all forms of life on earth are based on organic carbon compounds
-there are more carbon compounds than all other chemical compounds put together

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27
Q

Carbon

A

-can form covalent bonds with many elements
-has a valence of 4, can bond at most with 4 atoms
-organic compounds synthesized in a lab are identical of those isolated from lifeforms
-not limited to single covalent bonds, can form double or even triple bonds
-the sharing of 2 electrons between atoms is double, 3 is triple

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28
Q

What are the types of simple organic compounds?

A

Alkanes, Alcohols, Carboxylic Acids, Aldehydes, Amino Acids

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29
Q

Alkanes

A

Common feature: saturated hydrocarbons
(all bonds are single bonds, so considered saturated with hydrogen)
Ex:
-methane
-ethane
propane
-butane

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30
Q

Alcohols

A

common feature: -OH functional group
Ex:
-methanol
-ethanol
-glycerol

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31
Q

Carboxylic Acid

A

common feature: -COOH functional group
Ex:
-acetic acid
-butyric acid
-lactic acid

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32
Q

Aldehydes

A

common feature: -COH
Ex:
-formaldehyde
-acetaldehyde

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33
Q

Carbohydrates

A

-organic compounds composed of carbon, hydrogen, and oxygen (CHO) used as the primary source for derivation of energy in human metabolism
-classified into sugars, starches, dextrins and glycogen
-other types like cellulose are not digestible by humans (fiber)

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34
Q

Monosaccharides

A

ex: sucrose (table sugar), lactose (sugar in milk), maltose (malt sugar), and glucose (sugar found in blood)
-sugars are the simplest of carbohydrates
-the simplest sugars are monosaccharides
-the most common saccharides are 6 carbon sugars called hexoses

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35
Q

What are the 5 monosaccharides/hexoses that occur freely in nature?

A

glucose, mannose, galactose, fructose and sorbose

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36
Q

Glucose

A

sweet and is key in browning reactions; converts (polymerizes) to starches

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37
Q

Fructose

A

the higher the levels of glucose and fructose in potatoes, the more susceptible to non-enzymatic browning
-storage at low temp <40 degrees 5-6mo) inhibits sprouting but induce CHO –> sugar conversion
-if the potato is conditioned by holding 2 wks @ 70 degrees, the sugars will reconvert to CHO

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38
Q

Where to carbohydrates come from in the human diet?

A

Plants; through photosynthesis

6CO2 + 6H2O + Sunlight = C6H12O6 + 6O2

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39
Q

Disaccarides

A

-when 2 monosaccharide molecules chemically combine
Maltose = 2 glucose molecules
Lactose = galactose + glucose

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40
Q

Oligosaccharides

A

raffinose = galactose/glucose/fructose
stachyose = galactose/glucose/fructose found in soybeans and not readily digestible

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41
Q

Polysaccharides

A

-starch
-long chains of simple sugar like starch
-composed of 2 polysaccharides: 20% Amylose and 80% Amylopectin

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42
Q

Amylose

A

50-500 glucose molecules connected in a straight chain

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43
Q

Amylopectin

A

up to 100000 glucose in branched chains
-both chains are held together by hydrogen bonding

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44
Q

Conversion

A

-reverse photosynthesis
-converting glucose to glycogen

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45
Q

Indigestible polysaccharides

A

insoluble dietary fiber

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46
Q

Properties of carbs

A

-enolization
-heating glucose
-caramelization
-maillard browning reaction

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47
Q

Enolization

A

-heating process in the presence of alkaline solution
-get a lot of isomerization (change in structure)

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48
Q

Heating glucose

A

-under acidic conditions result in brown pigment
-sulfites can be used to prevent browning

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49
Q

Caramelization

A

reaction controlled by pH
acidic = color only
basic = color and flavor

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50
Q

Maillard Browning Reaction

A

-reducing sugar and some compound with a primary amine (donated by a protein(
1. condensation - sugar + amine = schiff’s base (glycosylamine)
2. amadon rearrangement
3. stecker degradation - loss/destruction of amino acids

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51
Q

How to control maillard reaction:

A
  1. temperature
  2. remove/reducing sugar
  3. add sulfites
  4. pH
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52
Q

Properties of Starch

A

A high amylose starch:
-difficult to gelatinize
-requires more heat
-forms tighter crystalline structure
A high amylopectin starch:
-easier to gelatinize
-easier to hydrate (branches)
-gelatinizes at lower temp

53
Q

Gelatinize

A

-starch is granular, but in the presence of heat and water the chains hydrate and soften then swell
-as starch swells the mixture thickens
-the more amylose, the stronger the gel

54
Q

Flavor

A

Taste and Olfactory perception
-operate differently but not separately

55
Q

What are the 5 modalities of flavor?

A

sweet (sucrose), salt (sodium chloride), umami (msg), sour (acetic acid), and bitter (quinine)

56
Q

Olfactory receptors

A

-at top of nasal cavity
-can distinguish 1000’s of different stimuli (not just 5)
-olfactory nerve can also attenuate (get used to smell)

57
Q

Sweetness

A

-structural basis of sweet modality
-not everything that gives sweet perception is a sugar: chloroform fits sweet receptor
-fructose fit better so perceived as sweeter (threshold is lower)

58
Q

Bitterness

A

-similar structure to sweet (can get flavors mixed up)
-a compound can fit into different taste buds
-Quinine, Creatine, Caffeine and theobromine, limonin

59
Q

Bitterness: quinine

A

medicinal agent, desirable in some alcoholic drinks

60
Q

Bitterness: Creatine

A

found in muscle (secondary energy system)

61
Q

Bitterness: caffeine and theobromine (in cocoa)

A

very similar structures, desirable bitter compounds

62
Q

Bitterness: Limonin

A

bitter flavor in citrus = defect develops with aging of juice

63
Q

Humolone convert to isohumolone (beer)

A

desirable flavor, but can be easily changed to a skunky flavor by uv light (bottle in dark bottle or cans)

64
Q

Sour

A

-commonly associated with acidity but do not correlate

65
Q

Umami

A

-newly discovered receptor in 2000
-found that there were glutamate receptors on tongue and stomach tissue
-the umami taste is often described as meaty, broth-like or savory and is independent from the other 4 modalities

66
Q

Flavor enhancers

A

-maltol, isomaltol
-L-Glutamine, salt (msg)
-NaCL

67
Q

Astringency

A

-tannins

68
Q

Pungency

A

-capsaicin (red peppers)
-gingerol (ginger)
-piperine (B&W pepper)

69
Q

Sulfur volatiles

A

-horseradish
-radish
-shitake mushrooms

70
Q

Flavor volatiles in muscle foods

A

-species specific, enzymatic
-mutton like
-cooked fish smell
-fishy odor
-formaldehyde

71
Q

Fat soluble vitamins

A

Vitamin A, E, D, K, B1, B2, B6, B12, C

72
Q

Vitamin A

A

-found only in animals
-required for vision and resistance to infection

73
Q

Vitamin E

A

-alpha, beta, gamma and delta - tocopherols
-found in seed germ
-serves as an antioxidant
-deficiency affect not clear

74
Q

Vitamin D

A

-normal tooth and bone development
-fish oils
-body can synthesize sterols like cholesterol
-D and A are added to milk
-deficiency may result in rickets

75
Q

Vitamin K

A

-needed for synthesis of prothrombin for clotting of blood
-good sources are spinach and cabbage

76
Q

Vitamin B1: Thiamin

A

-high in legumes
-B1 is destroyed by SO2, so SO2 should not be used as a preservative

77
Q

Vitamin B2: Riboflavin

A

-sensitive to high pH and light but heat stable
-milk, liver, eggs are good sources of

78
Q

Vitamin B12: Folacin

A

red blood cell formation

79
Q

Vitamin C: Abscorbic Acid

A

-readily oxidized by Cu ++ and Fe ++ in contact with metals during processing
-deficiency causes scurvy

80
Q

Iron

A

-trace mineral (because it is needed in small amounts)
-iron from animal sources thought to be absorbed better
-Vitamin E and C help with Iron absorption

81
Q

Calcium

A

-humans require this mineral in the greatest amount
-needed for bone and tooth structure, as well as for nerve and muscle function
-also needed for blood clotting
-deficiencies lead to osteoporosis
-Vitamin D and lactose essential for absorption of calcium

82
Q

Other major minerals

A

sodium, chlorine, potassium, phosphorus, magnesium, sulfur, iodine, fluorine, copper, cobalt, zinc

83
Q

Organic acids

A

-contribute to flavors, aroma, tartness

84
Q

Pigments

A

Anthocyanins (flavonoids):
-low pH triggers red color
-high pH triggers blue/violet color
Metals:
-flavonoids will leak from fruit during processing and interact with metals, which will change colors due to changed pH
High Temperature:
-can result in brown pigment
Oxygen
-added to reduce rapid degeneration

85
Q

Blanching

A

preserves anthocyanins by deactivating the enzymes that cause degradation. However, too much heat/time will degrade the pigment too

86
Q

Carotenoids

A

-fat soluble b-carotene = vitamin A (orange)
-fat soluble lycopene = no vitamin A (red)
-fat soluble chlorophyll = Mg ++ present (green)

87
Q

Myoglobins

A

-CO2 carriers (respiration of muscle cells)

88
Q

Proteins

A

-most abundant macromolecule in animal cells
-constitute over half the dry weight of most organisms
-made up of amino acids

89
Q

Functions of proteins

A

enzymes (catalysts to chemical reactions), transporters (hemoglobin, lipoproteins), contractile proteins (muscle contraction), structural proteins (collagen, keratin)

90
Q

Structure of proteins

A

-amino acids joined together by peptide bonds
-2 amino acids form a peptide bond
- di-, tri-, polypeptides
-polypeptide = protein

91
Q

Isoelectric Point (pI) of a protein

A

the pH at which the molecule is neutral (zero net charge; positives = negatives)

92
Q

Layers of protein structure

A

Primary, secondary, tertiary, quatenary

93
Q

Primary protein structure

A

-the number and sequential order of amino acids
-typical proteins contain 100-500 aa’s

94
Q

Secondary protein structure

A

refers to the shape that the polypeptide chain assumes along it’s axis (coiled helix)

95
Q

Tertiary protein structure

A

refers to 3-D shape from folding of protein

96
Q

Quatenary structure

A

-2 or more chains join together
-very sensitive to heat
-ex: pleated sheet

97
Q

Amino Acids composed of chains of:

A

H00C-CH-NH2

98
Q

Denaturation of Proteins

A

-the conformation of proteins is altered
-denaturation is the loss of biological activity
-denatured proteins are less soluble and less able to bind water
-caused by: heat, acids, solvents, salt, mixing

99
Q

Artificial sweeteners

A

-synthetic carbohydrates that were found to be many times sweeter than sucrose
-most common: saccharin, cyclamate, aspartame and acesulfame

100
Q

Lipids

A

-important constituent of food
-contain carbon, hydrogen and oxygen
-fats are also called lipids or triglycerides
-lipids are of plant or animal origin
-insoluble in water
-major members are fats and oils

101
Q

Structure of lipids

A

3 fatty acids on a glycerol backbone

102
Q

Saturated fats

A

have straight carbon chains with single bonds

103
Q

Unsaturated fats

A

have one or more double bond

104
Q

Monounsaturated fats

A

more than one double bond

105
Q

Single bonds

A

saturated with hydrogen

106
Q

Fats vs Oils

A

-oils are more unsaturated
-fats are more saturated
-unsaturated fats can be turned into saturated fatty acids called hydrogenation

107
Q

Reaction of Fats

A

-hydrogenation: hydrogen chemically added to double bonds
-Saponification: adding alkali to produce glycerol and soap
-Hydrolysis: breakdown lysis of lipid from heat & water effects
-Rancidity: a type of spoilage due to instability of fat

108
Q

2 kinds of rancidity

A

-Lipolytic rancidity: caused by action of the enzyme lipase; enzymes leave the glycerol backbone, releasing fatty acids
-Oxidative rancidity: oxygen attacks fats at the sites of unsaturation; causes bond to break

109
Q

What are lipids carriers of?

A

flavor

110
Q

Artificial lipids

A

Simplesse and Olestra

111
Q

Water Chemistry

A

Most familiar chemical compound, but most
important influences are least visible:
– Moderates climate, carves landscape, and all life
exists in a water solution!
– Humans 60% water (by weight)
* raw meat = 75%
* fruits and vegetables up to 95%

112
Q

The importance of hydrogen bonds

A
  • Hydrogen bonds:
    – weak but important bonds between H on one
    molecule, and O or N on another.
  • Water has two H and one O atom
  • The covalent bonds between O and H are
    ASYMMETRICAL .
  • O has a greater affinity for electrons than hydrogen,
    so the shared electrons are held closer to the O atom
113
Q

importance of hydrogen bonds continued

A

If all three atoms were in a straight line, the
molecule would be symmetrical.
* The net positive charges on the H would balance
each other, and water would not function in all
the incredible ways that we see in nature!
* Because of the disposition of other electrons in
the O atom, the covalent bonds are not at an
180 angle, but 105.
* Therefore, the molecule forms a V-like shape.
As a result of the bonding angle and the
electrical asymmetry of each bond,
WATER MOLECULES ARE POLAR

114
Q

First physical peculiarity of water

A

-Abnormally high melting and boiling points
Not like other hydrogen compounds of the
other elements in oxygen’s column of the
periodic table:
– sulfur, selenium, tellurium:
* Freezing point = - 150F
* Boiling point = - 110F
* If this were the case, water on earth would be gas
and life as we know it would not exist!

115
Q

First physical peculiarity of water continued

A

Because of the asymmetrical bonds, it is
more difficult to separate one water
molecule from another.
– This results in an abnormally high melting and
boiling points.
– This also gives water an unusually high
“latent heat of vaporization”:
* The energy water absorbs without a rise in
temperature as it changes from liquid to gas

116
Q

First physical peculiarity of water continued

A

Plants and animals have used this property for
temperature regulation.
– As we overheat, we excrete water onto outer surfaces.
– As the water evaporates, it absorbs large amounts of
energy from the body and carries it away.
* Ancient cultures used the same principle for
cooling water and wine.
– Porous clay vessels evaporate moisture continuously
from their surfaces.

117
Q

Second physical peculiarity: Ice Floats

A

Normally, the solid phase of a given
substance is more compact and dense
than the liquid phase.
– Molecules move around less and settle into a
compact arrangement.
In solid form, the bond angle of water
changes from 105 to 109 in order to
form a crystalline ordered structure.
* As ice crystals begin to form, water
expands by about one-eleventh.
* Because ice is less dense that water,
IT FLOATS
In everyday life, this can be inconvenient!
– Water pipes burst when heat fails in the winter.
– Bottled beverages placed in the freezer for a quick
chill and left forgotten pop open.
– Containers of leftover soup will shatter if not enough
room is left for expansion.
– Plant and animal tissue may be damaged during
freezing when expanding ice crystals rupture cell
walls.

118
Q

Third Physical Peculiarity:
Water is Slow to Heat

A

Water has a abnormally high SPECIFIC
HEAT
– the amount of energy required to raise its
temperature by a given amount

119
Q

Third Physical Peculiarity:
Water is Slow to Heat Continued

A

The consequence of this peculiarity is
considerable:
– Living organisms (which are 50 –95% water) can
moderate the sudden environmental temperature
changes.
– We can absorb or lose considerable amount of energy
without becoming dangerously hot or cold.
– We are like miniature oceans or lakes, which even out
climatic changes by soaking up or releasing energy in
extreme conditions without reaching extreme
temperatures themselves

120
Q

Third Physical Peculiarity:
Water is Slow to Heat Continued

A

The consequence of this peculiarity is
considerable:
– When we want to cook something delicate
(like custard) we do so in a water bath rather
than exposing it to direct heat.
– Water is involved in reactions in most foods.
– Water influences texture, stability, etc.

121
Q

Free Water:

A

This water retains its physical properties and thus acts as the
dispersing agent for colloids and the solvent for salts.

122
Q

Adsorbed Water:

A

This water is tightly held or is occluded in cell walls or
protoplasm and is help tightly to proteins.

123
Q

Water of hydration

A

This water is bound chemically

124
Q

Bound water

A

– that water which exists intimately associated
with the solute molecule.
– It has reduced molecular ability (won’t freeze
at -40C) and can’t be removed by
conventional drying techniques (only way to
remove is essentially ashing it)
– Type I water: Vicinal water
first layer of bound water molecules
– Type II water: Multilayer water
second layer of bound water molecules

125
Q

Bulk phase water

A

– Type III water:
Entrapped water (in capillaries) and free
water

126
Q

Water activity (aW)

A

aW = the partial pressure of water vapor
above the sample, divided by partial
pressure of pure water vapor at the same
temperature.
* aW = vp of water above sample
vp of pure water at same T

127
Q

Water activity (aW) continued

A

aW can be used as predictor of microbial
growth
* 0.7 – 0.8 = yeast, mold, bacterial growth
* 0.2 – 0.7 = Maillard browning (non-enzymatic
browning)
* also an indicator of certain major chemical
reactions that occur in food (lipid oxidation
and enzymatic browning)

128
Q
A

Intro to Food Science (1 decks)

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