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Introduction to food science > Chapter 5 and 6 > Flashcards

Chapter 5 and 6 Flashcards

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1
Q

In what states water is found

A

Solid, liquid, gaseous

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2
Q

Water is ___ (food industry) and ___ (health)

A


the main component of many foods

a nutrient necessary to sustain life

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3
Q

Nutritionally water does what

A 

helps control body temperature

transports nutrients and waste products

provides the solution for metabolic reactions
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4
Q

In food science water can do what

A


influences the texture, appearance, and taste of food

is an important heat medium in cooking

is an important solvent for cleaning and sanitation

is critical in food preservation

determines the likelihood of food spoilage by its presence or absence

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5
Q

What bonds there are in water and charges

A

polar covalent and hydrogen

Has partially negative charge on oxygen and partially positive on hydrogen

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6
Q

Water should be a gas at room temperature, because of its size, why it is not?

A

Hydrogen bonding that hold molecules together

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7
Q

Hydrogen bonds Hydrogen bonds in water create a greater surface tension than most
compounds, allowing water to

A


cling to something else as well as itself

have a higher melting and boiling point than other compounds

freeze faster than it thaws

form a crystalline structure in the solid state

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8
Q

Hydrogen bonds help to dissolve ___ substances

A

Polar

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9
Q

What influences the boiling and freezing points

A

Atmospheric pressure

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10
Q

What happens to water boiling temperature at high altitudes ?

A

Water boils at lower temperatures at high altitudes and at higher
temperatures at low altitudes

High altitude baking considerations such as increasing the amount of flour,
water content, and oven temperature need to be considered

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11
Q

Water is not usually found in pure form because it is such a great
solvent

An impurity in water may change its (4 points)

A 

physical and chemical characteristics

flavor and color

boiling and freezing points

hydrogen bonding
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12
Q

Temperature of water steam

A

As boiling water , but can be higher under pressure

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13
Q

Steam in cooking

A


leaves food more flavorful and nutritious than boiling ( vitamins do not leach out)

leavens baked goods

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14
Q

What solution is CO2 in carbonated beverages

A

Gas-in-water solutions

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15
Q

What is partially responsible for water taste

A

Oxygen

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16
Q

Examples of liquid-in-water solutions

A

Alcoholic beverages, vinegars and fruit juice concentrates are examples

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17
Q

Salt and sugar ____ the freezing point and increase the boiling point of
water

A

lower

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18
Q

What is tea and coffee in water

A

Tea and coffee are flavor compounds dissolved in water

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19
Q

Gave examples of water percentage in most foods

A 

Fruits and vegetables are over 70 % water

Bread is 36 % water

Popcorn is 4 % water
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20
Q

What characteristic in products is related to its perishability

A

H2O content

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21
Q

Why water is responsible for perishability

A

This is because water is both a reactant and a reaction medium
deteriorative chemical changes ) and is a requirement for microbial
growth ( spoilage

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22
Q

3 ways water can be a structure of food

A

Free water
Hydrate water
Bound

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23
Q

Characteristics of free water (4)

A 

is easily separated from food tissue

often contains dissolved compounds

boils and freezes easily

readily evaporates when foods are dried
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24
Q

What is anhydrous

A

A process of separating hydrate water to the compound by boiling

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25
Q

Characteristics of bound water (3)

A

is tied to the structure of larger molecules

does not easily freeze or boil

chemically reacts as part of the larger molecule

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26
Q

Both carrots and milk have 88% of water in them, but they spoil differently,why?

A


Water bound to other compounds is not available to support food spoilage

Water in carrots is mostly bound to starch molecules, while in milk, it s mostly
free

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27
Q

Rigidity of plant cells is due

A

the cells are filled with water

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28
Q

Moisture content is also closely related to ___

A

The texture of many products

Responsible for juiciness or crispness of harvested fruits and vegetables

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29
Q

Meat and water

A

Meat: changes in water holding capacity of meat proteins during
freezing or heating affect texture

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30
Q

What can cause an increase in water content in fried snack foods

A

Textural defects

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31
Q

What is water activity and how it is calculated

A

A measure of available (mobile) water in a food system

𝑎𝑤=𝑃(𝑇)/𝑃0(𝑇)

where:

P = partial vapour pressure of water over a sample of food

P0 = partial vapour pressure of pure water

T = temperature

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32
Q

water activity results interpretation

A

𝑎𝑤is on a scale of 0 to 1.0 (pure water)

The smaller-> less perishable, less active

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33
Q

Water activity takes into account ___

A

) takes into account the water available to support

enzyme activity and microorganism growth

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34
Q

Canned vs dried foods, what is more perishable

A

Canned

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35
Q

What techniques are used for removal of water from food

A 

Dehydration/drying

Concentration (removal of some of the water)

Freezing
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36
Q

The preservation effect of removing water is actually based on a ____

A

reduction in water activity (a w ) - free water rather than moisture content per se.

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37
Q

What is considered a contaminant or pollutant

A

Anything that makes a substance like water impure or unsafe such as

  • human and animal wastes
  • chemicals and factory waste
  • grabage
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38
Q

What are biological contaminant in water

A

Large numbers of bacteria, protozoa, viruses, and organic waste deplete oxygen from rivers, lakes , and water supplies

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39
Q

Chemical contaminants in water

A

Metal ions such as calcium and Mg -> hard water

Acid rain changes the pH of water

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40
Q

Physical contaminants in water

A

Garbage and litter such as cans, bottles, and plastics harbor bacteria, cause physical harm, and break down into toxins that enter water supply

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41
Q

Water quality standards are ____ for food applications

A

Are very high

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42
Q

Potable water and food processing

A

Potable water is suitable for drinking but usually requires further treatment to be suitable for use in food processing

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43
Q

Why water quality is so controlled

A

Control over a manufacturing process requires that all factors that may contribute to variability be controlled

E.g. Minerals present in municipal water may interact with food constituents

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44
Q

What is BOD

A

Biological oxygen demand: milligrams of oxygen consumed per liter of sample during 5 days of incubation at 20C

Amount of oxygen that aerobic microorganisms in a body of water require to break down all the organic matter present

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45
Q

Why high BOD is not suitable for food production

A

high BOD leaves insufficient oxygen for fish

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46
Q

What should be done with water before leaving the plant

A

Large amounts of organic matter present in food processing wastewater would cause high BOD -> should be treated before discharge

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47
Q

What is 99% of food

A

Major components - proteins, CHO, fat, water

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48
Q

What are nutritive aspects of foods

A

Vitamins and minerals , which are minor constituents

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49
Q

What do cranberries contain

A

sodium benzoate : a natural preservative

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50
Q

Where you can find beta-carotene

A

Pigment in carrots

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51
Q

What does vegetable oil have

A

Alpha-tocopherol ( antioxidant)

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52
Q

example of an acidulant

A

Citric acid in lemons

Phosphoric acid

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53
Q

What is extracted from papyas

A

Papain- proteolytic enzyme

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54
Q

What is food additive

A

Any constituents that are either isolated from their source or
synthesized and then incorporated into commercial food products are

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55
Q

What is the exception for legal food additives list

A

U.S. Food and Drug Administration (FDA) as GRAS ” = G enerally
R ecognized A s S afe- were used for a long time already and was fine

Can be used without pre-market approval from FDA

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56
Q

Minor constituents include

A

Naturally occurring and added

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57
Q

What is an emulsifier

A

Emulsifiers are compounds that can keep aqueous and oil phases
together in a food emulsion.

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58
Q

Two phases in emulsion

A

Internal- what we have less in the solution (inside micells)

-External, where internal is dispersed

59
Q

Tendency of droplets in external phase

A

Droplets have a tendency to aggregate and coalesce to minimize
contact with the external phase ( interfacial tension

60
Q

Coalesce cause ___ of the emulsion

A

Breaking-> separation into 2 different phases , emulsion stabalizes emulsion and prevents coalescence

61
Q

Explain emulsion in salad dressing

A

) phase. Emulsifier molecules are
present at the surfaces of the oil droplets with their nonpolar ends
facing inwards and their polar ends protruding into the water.

As a result, coalescence of the oil droplets is prevented.

62
Q

Name natural emulsifier

A

Lecithins and mono, diglycerides

63
Q

Functionality of an emulsifier is characterized by

A 
hydrophilic
lipophilic balance (HLB)
64
Q

Who has higher HLB mono or diglyceride

A

Monoglyceride

65
Q

Emuslifier is a common constituent in what type of foods

A

food with significant amounts of fat

66
Q

What organic acids are found naturally in food

A 
Organic acids (i.e., carboxylic acids) such as citric, malic, and tartaric
acids are found in many fruits.
67
Q

Role of acids in fruits

A

These acids impart flavor as well as acidifying characteristics

68
Q

Role of acids as the result of fermentation

A

Organic acids produced during fermentation (by microorganisms
metabolizing carbohydrates) contribute to the taste of fermented
foods and cause curd formation by milk proteins (production of yogurt
and cheese).

69
Q

In what products organic acids and phospharic acids are used

A 
Organic acids (fruit drinks)

Phosphoric acid (colas, root beer)
70
Q

Acidulants and preserving effect

A

Preservative effect: A reduction in pH tends to slow down microbial
spoilage .

71
Q

What is considered high and low pH

A


pH ≤ 4.6 : high acid food

pH > 4.6 : low acid food

72
Q

Low-acid canned food require

A

require much more extensive thermal

processing

73
Q

Why would we want low pH in some products, apart from preservation

A

Acidulants are added to obtain the low pH required for gel formation in
jams/jellies produced using pectin.

Acidulants prevent enzymatic browning in fruits and vegetables.

74
Q

Enzymatic browning happens due to

A

polyphenol oxidase , an enzyme that catalyzes oxidation of

polyphenol compounds present in plant cells.

75
Q

Enzymatic activity becomes uncontrolled when ___

A

Enzymatic activity becomes uncontrolled when tissues are damaged
(e.g., by slicing or peeling).

76
Q

Nonenzymatic browning another name

A

Maillard reaction

77
Q

Oxidation leads to ____ in fats and oils and cause ____ in foods

A

In particular, oxidation leads to rancidity of fats and oils as well as
off flavor development in foods and color losses

78
Q

Oxidation is ( definition)

A

Oxidation: a reaction in which an electron is removed from a

molecule by an oxidant.

79
Q

O2 is a strong oxidant, capable of oxidizing ___ compounds:____

A 
O 2 is a strong oxidant, capable of oxidizing electron rich
compounds :

Unsaturated fats and oils

β Carotene (pigment, precursor of vitamin A)

Chlorophyll (pigment)

Ascorbic acid (vitamin C)
80
Q

Role of antioxidants

A

Antioxidant is a compound that prevents (or delays) reactions of food
components with O 2

81
Q

Natural antioxidants

A 
Lecithin

Ascorbic acid (vitamin C)

Tocopherols (vitamin E)
82
Q

What is added to fats and oild at levels of 0.01%

A

Synthetic antioxidants

83
Q

Examples of synthetic antioxidants

A 
Butylated hydroxyanisole (BHA)
 butylated hydroxytoluene (BHT)

Propyl gallate

Tertiary butylhydroxyqulnone

84
Q

Oxidation reactions involving molecular oxygen are ___

A

Chain reactions that proceed by a free-radical mechanism

85
Q

What are free radicals

A

Free radicals are species that have a single unpaired electron : they
are extremely reactive.

86
Q

Lipid autoxidation involves

A

For example, lipid autoxidation involves the formation of peroxy
radicals: LOO. (L = lipid)

87
Q

How antioxidants function

A

Antioxidants function by scavenging free radicals and terminating
free radical chain reactions.

Many antioxidants are sacrificial ” antioxidants, meaning that they
become oxidized themselves, e.g., ascorbic acid.

88
Q

Antioxidation reaction in living organism vs food

A

In living cells these oxidized antioxidants are replaced by
biosynthesis and/or regenerated by enzymes , but in foods
antioxidant depletion occurs over time.

89
Q

You should look into properties of the product before putting antioxidant in because

A

Vitamin C-> water soluble

Vitamin E-> fat soluble

90
Q

In what units pigments and colors are expressed

A

parts per million

For example: 100 parts per million= 10^2/10^6=10^-2/100=0.01%

91
Q

Definition of pigments

A

A natural substance that absorbs visible light and gives color to plants or animals

92
Q

Many pigment molecules are ____ so that their color is affected by
____

A

unstable

pH, reactions with O 2 , or other factors

93
Q

Groups that contribute to natural food color

A 

Chlorophylls

Anthocyanins

Carotenoids

Meat proteins

Tannins
94
Q

What causes color change from bright green to olive brown

A

Conversion of chlorophyll to pheophytin (by loss of the magnesium
ion at the core of its structure) causes a color change

95
Q

When chlorophyll converts to olive brown

A

This conversion easily occurs during processing (even in a blanching
step before freezing) and storage and is responsible for the drab
color of canned, and to a lesser extent, frozen green vegetables

96
Q

Color of chlorophyll is also affected by

A

oxidation and changes in

pH.

97
Q

Pigment that is responsible for red/blue/violet color

A

Anthocyanins

98
Q

Anthocyanins belong to a large class of

A

Flavonoids

99
Q

Flavonoid’s general structure

A

: two aromatic rings fused together

and connected by a single bond to a third aromatic ring

100
Q

What R groups can be present on flavonoids

A

R groups can be H, OH, or OCH 3

101
Q

Anthocyanins are water/lipid soluble?

A

Water

102
Q

Color change in anthocyanins

A

Colors change with changes in pH: stronger colors in acidic solution .

103
Q

Additional variability in the structure of anthocyanins is due to

A

glycosylation

104
Q

What does it mean that antocyanins are glycosylated

A

: anthocyanins isolated from plants are glycosylated,
meaning that one (or more) of the OH groups is attached to a sugar
by a glycosidic bond.

105
Q

Characteristics of carotenoids ( solubility, what color, saturation)

A

Fat soluble and highly unsaturated molecules responsible for orange
and yellow colors in nature.

106
Q

Beta-carotene is the precursor to

A

Vitamin A , from 1 beta carotene-> 2 vitamin A

107
Q

Lycopene : where found , what color

A

Lycopene (tomatoes, red carrots)

108
Q

Lutein: where fund , what color

A

Lutein (leafy green vegetables, color is masked by chlorophyll; added
to chicken feed to make egg yolks darker yellow)

109
Q

Color of salmon is due to

A

carotenoids in their diet of
shrimp and krill (smaller crustaceans) become incorporated in the fish
flesh.

110
Q

What happens to farmed salmon if it is fed with plant-based diet

A

grayish flesh so carotenoids are added to their feed (representing
15 20 % of the total cost of the feed)

111
Q

What is annatto

A

Annatto is a food additive obtained from the seeds of the Bixa
orellana tropical shrub that contains bixin (a fat soluble carotenoid)
and norbixin (a water soluble carotenoid) and added to foods as a
colorant; e.g., used to color cheddar cheese orange yellow.

112
Q

saffron: what pigment and where found

A

is a carotenoid found in the crocus stamen that provides both
color (yellow) and flavor

113
Q

Carotenoids, anthocyanins and chlorophyll are what for plants

A

C are phytochemicals phyto means plant in
Greek) that serve as antioxidants in plants and protect plants from
light induced damage

The fact that they are colored (absorb visible light) necessarily means
that they have delocalized electrons that are relatively easily
removed.

Consequently, they are easily oxidized and can function as
sacrificial ” antioxidants that consume reactive oxygen species

114
Q

Are phytochemicals have health effect?

A

Not yet determined

115
Q

Myoglobin and hemoglobin have what component in the structure

A

Fe2+

116
Q

Red color of fresh meat is due to

A

The red color of fresh meat is due to the binding of oxygen (in the air)
to the heme group of myoglobin.

117
Q

What happens with color of meat over time

A

The color of fresh meat is very unstable over time: oxidation of the
Fe 2 ion in myoglobin molecules to Fe 3 slowly occurs and causes the
color to shift from red toward purple

Accordingly, the color of meat is used by consumers as the main
indicator of freshness and strongly affects the price of meat.

118
Q

CO and Fe2+ produce what color

A

Cherry-red color

119
Q

What happens with modified packaging and meat in US

A

The use of a blanket of CO in modified atmosphere packaging (MAP)
can make meat look fresh (for up to a year!), which potentially could
be dangerously deceptive.

More deceptively, some opponents of this practice (which is permitted
in the U.S.) refer to the possible dangers as carbon monoxide food
poisoning

120
Q

CO, meat and canadian regulations

A

In Canada , the use of CO in MAP for meat is only permitted in outer
packaging (not in direct contact with the meat), where CO preserves
meat color by a different mechanism: prevention of contact with air .

121
Q

The color change that occur to the meat when it is cooked is due to

A

denaturation of myoglobin .

122
Q

Why cured meat is pink

A

The pink color of cured meats (which are preserved by salt) that
contain nitrites is due to the binding of nitric oxide (NO) to the heme
group.

123
Q

Tannins are

A

Tannins are a large group of polymeric polyphenolic compounds
occurring in plants and soil: black brown yellow colors

124
Q

Tannins are responsible for and found in

A

Astringency, responsible for the color and astringency of tea

125
Q

Progression of color in maillard and caramelization reaction and it contributes to

A

Colors: yellow brown black

Both caramelization and the Maillard reaction are very complex and
produce both color and flavor

126
Q

Influence of color on humans

A

Overall, color has a major psychological effect and can dramatically
affect taste perception: Jell

127
Q

Our perception of flavor involves a combination of two senses:

A

taste

and smell

128
Q

Human tongue can sense

A

Human tongue has receptors for only five tastes : sweet, salty, bitter,
and sour plus umami (savory or brothy ” taste).

Umami is due to the presence of receptors for glutamate in the
tongue.

129
Q

Monosodium glutamate is used as

A

flavor potentiator

130
Q

Coffee aroma contains ___ compounds

A

800

131
Q

Many types of volatile organic compounds contribute to aroma:

A

short

chain fatty acids, alcohols, aldehydes, ketones, etc.

132
Q

___ are major contributors to the aroma of

onions and garlic.

A

Sulfur containing compounds

133
Q

How much of flavor usually is in the product?

A

Very little: for example
Vanillin can be tasted at a level of 0.1 ppm ( 0.00001

Isopentyl acetate (key compound in banana aroma) has an olfactory
threshold of 0.005 ppm ( 0.0000005

134
Q

Banana flavor is due to what compound

A

Isopentyl acetate (key compound in banana aroma) has an olfactory

135
Q

If studied carefully, coffee aroma of 800 can be replaced with

A

30-50 constituents

136
Q

A key flavor category is

A

Essential oils

137
Q

Essential oils are the essence ” of flavors associated with plant
materials:

A

mint, strawberry, orange, raspberry, apple, etc.

138
Q 
Essential oils are made up largely of \_\_\_\_ , a class of volatile
hydro\_\_\_\_ molecules:
A

terpenes

phobic

139
Q

Citral is responsible for what flavor

A

Lemon

140
Q

Limonene is responsible for

A

Lime flavor

141
Q

Beta-sinensal is responsible for what flavor

A

Orange

142
Q

Nootkatone is responsible for what flavor

A

Grapefruit

143
Q

How essential oils can be extracted from plant sources

A

By steam distillation

144
Q

What are reaction flavors

A

are another important sub category of flavors: they
can be produced commercially by controlled or directed Maillard
and/or caramelization reactions.

Introduction to food science (12 decks)

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