Chapter 5 and 6 Flashcards
In what states water is found
Solid, liquid, gaseous
Water is ___ (food industry) and ___ (health)
the main component of many foods
a nutrient necessary to sustain life
Nutritionally water does what
helps control body temperature transports nutrients and waste products provides the solution for metabolic reactions
In food science water can do what
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
What bonds there are in water and charges
polar covalent and hydrogen
Has partially negative charge on oxygen and partially positive on hydrogen
Water should be a gas at room temperature, because of its size, why it is not?
Hydrogen bonding that hold molecules together
Hydrogen bonds Hydrogen bonds in water create a greater surface tension than most
compounds, allowing water to
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
Hydrogen bonds help to dissolve ___ substances
Polar
What influences the boiling and freezing points
Atmospheric pressure
What happens to water boiling temperature at high altitudes ?
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
Water is not usually found in pure form because it is such a great
solvent
An impurity in water may change its (4 points)
physical and chemical characteristics flavor and color boiling and freezing points hydrogen bonding
Temperature of water steam
As boiling water , but can be higher under pressure
Steam in cooking
leaves food more flavorful and nutritious than boiling ( vitamins do not leach out)
leavens baked goods
What solution is CO2 in carbonated beverages
Gas-in-water solutions
What is partially responsible for water taste
Oxygen
Examples of liquid-in-water solutions
Alcoholic beverages, vinegars and fruit juice concentrates are examples
Salt and sugar ____ the freezing point and increase the boiling point of
water
lower
What is tea and coffee in water
Tea and coffee are flavor compounds dissolved in water
Gave examples of water percentage in most foods
Fruits and vegetables are over 70 % water Bread is 36 % water Popcorn is 4 % water
What characteristic in products is related to its perishability
H2O content
Why water is responsible for perishability
This is because water is both a reactant and a reaction medium
deteriorative chemical changes ) and is a requirement for microbial
growth ( spoilage
3 ways water can be a structure of food
Free water
Hydrate water
Bound
Characteristics of free water (4)
is easily separated from food tissue often contains dissolved compounds boils and freezes easily readily evaporates when foods are dried
What is anhydrous
A process of separating hydrate water to the compound by boiling
Characteristics of bound water (3)
is tied to the structure of larger molecules
does not easily freeze or boil
chemically reacts as part of the larger molecule
Both carrots and milk have 88% of water in them, but they spoil differently,why?
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
Rigidity of plant cells is due
the cells are filled with water
Moisture content is also closely related to ___
The texture of many products
Responsible for juiciness or crispness of harvested fruits and vegetables
Meat and water
Meat: changes in water holding capacity of meat proteins during
freezing or heating affect texture
What can cause an increase in water content in fried snack foods
Textural defects
What is water activity and how it is calculated
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
water activity results interpretation
𝑎𝑤is on a scale of 0 to 1.0 (pure water)
The smaller-> less perishable, less active
Water activity takes into account ___
) takes into account the water available to support
enzyme activity and microorganism growth
Canned vs dried foods, what is more perishable
Canned
What techniques are used for removal of water from food
Dehydration/drying Concentration (removal of some of the water) Freezing
The preservation effect of removing water is actually based on a ____
reduction in water activity (a w ) - free water rather than moisture content per se.
What is considered a contaminant or pollutant
Anything that makes a substance like water impure or unsafe such as
- human and animal wastes
- chemicals and factory waste
- grabage
What are biological contaminant in water
Large numbers of bacteria, protozoa, viruses, and organic waste deplete oxygen from rivers, lakes , and water supplies
Chemical contaminants in water
Metal ions such as calcium and Mg -> hard water
Acid rain changes the pH of water
Physical contaminants in water
Garbage and litter such as cans, bottles, and plastics harbor bacteria, cause physical harm, and break down into toxins that enter water supply
Water quality standards are ____ for food applications
Are very high
Potable water and food processing
Potable water is suitable for drinking but usually requires further treatment to be suitable for use in food processing
Why water quality is so controlled
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
What is BOD
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
Why high BOD is not suitable for food production
high BOD leaves insufficient oxygen for fish
What should be done with water before leaving the plant
Large amounts of organic matter present in food processing wastewater would cause high BOD -> should be treated before discharge
What is 99% of food
Major components - proteins, CHO, fat, water
What are nutritive aspects of foods
Vitamins and minerals , which are minor constituents
What do cranberries contain
sodium benzoate : a natural preservative
Where you can find beta-carotene
Pigment in carrots
What does vegetable oil have
Alpha-tocopherol ( antioxidant)
example of an acidulant
Citric acid in lemons
Phosphoric acid
What is extracted from papyas
Papain- proteolytic enzyme
What is food additive
Any constituents that are either isolated from their source or
synthesized and then incorporated into commercial food products are
What is the exception for legal food additives list
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
Minor constituents include
Naturally occurring and added
What is an emulsifier
Emulsifiers are compounds that can keep aqueous and oil phases
together in a food emulsion.
Two phases in emulsion
Internal- what we have less in the solution (inside micells)
-External, where internal is dispersed
Tendency of droplets in external phase
Droplets have a tendency to aggregate and coalesce to minimize
contact with the external phase ( interfacial tension
Coalesce cause ___ of the emulsion
Breaking-> separation into 2 different phases , emulsion stabalizes emulsion and prevents coalescence
Explain emulsion in salad dressing
) 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.
Name natural emulsifier
Lecithins and mono, diglycerides
Functionality of an emulsifier is characterized by
hydrophilic lipophilic balance (HLB)
Who has higher HLB mono or diglyceride
Monoglyceride
Emuslifier is a common constituent in what type of foods
food with significant amounts of fat
What organic acids are found naturally in food
Organic acids (i.e., carboxylic acids) such as citric, malic, and tartaric acids are found in many fruits.
Role of acids in fruits
These acids impart flavor as well as acidifying characteristics
Role of acids as the result of fermentation
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).
In what products organic acids and phospharic acids are used
Organic acids (fruit drinks) Phosphoric acid (colas, root beer)
Acidulants and preserving effect
Preservative effect: A reduction in pH tends to slow down microbial
spoilage .
What is considered high and low pH
pH ≤ 4.6 : high acid food
pH > 4.6 : low acid food
Low-acid canned food require
require much more extensive thermal
processing
Why would we want low pH in some products, apart from preservation
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.
Enzymatic browning happens due to
polyphenol oxidase , an enzyme that catalyzes oxidation of
polyphenol compounds present in plant cells.
Enzymatic activity becomes uncontrolled when ___
Enzymatic activity becomes uncontrolled when tissues are damaged
(e.g., by slicing or peeling).
Nonenzymatic browning another name
Maillard reaction
Oxidation leads to ____ in fats and oils and cause ____ in foods
In particular, oxidation leads to rancidity of fats and oils as well as
off flavor development in foods and color losses
Oxidation is ( definition)
Oxidation: a reaction in which an electron is removed from a
molecule by an oxidant.
O2 is a strong oxidant, capable of oxidizing ___ compounds:____
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)
Role of antioxidants
Antioxidant is a compound that prevents (or delays) reactions of food
components with O 2
Natural antioxidants
Lecithin Ascorbic acid (vitamin C) Tocopherols (vitamin E)
What is added to fats and oild at levels of 0.01%
Synthetic antioxidants
Examples of synthetic antioxidants
Butylated hydroxyanisole (BHA) butylated hydroxytoluene (BHT)
Propyl gallate
Tertiary butylhydroxyqulnone
Oxidation reactions involving molecular oxygen are ___
Chain reactions that proceed by a free-radical mechanism
What are free radicals
Free radicals are species that have a single unpaired electron : they
are extremely reactive.
Lipid autoxidation involves
For example, lipid autoxidation involves the formation of peroxy
radicals: LOO. (L = lipid)
How antioxidants function
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.
Antioxidation reaction in living organism vs food
In living cells these oxidized antioxidants are replaced by
biosynthesis and/or regenerated by enzymes , but in foods
antioxidant depletion occurs over time.
You should look into properties of the product before putting antioxidant in because
Vitamin C-> water soluble
Vitamin E-> fat soluble
In what units pigments and colors are expressed
parts per million
For example: 100 parts per million= 10^2/10^6=10^-2/100=0.01%
Definition of pigments
A natural substance that absorbs visible light and gives color to plants or animals
Many pigment molecules are ____ so that their color is affected by
____
unstable
pH, reactions with O 2 , or other factors
Groups that contribute to natural food color
Chlorophylls Anthocyanins Carotenoids Meat proteins Tannins
What causes color change from bright green to olive brown
Conversion of chlorophyll to pheophytin (by loss of the magnesium
ion at the core of its structure) causes a color change
When chlorophyll converts to olive brown
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
Color of chlorophyll is also affected by
oxidation and changes in
pH.
Pigment that is responsible for red/blue/violet color
Anthocyanins
Anthocyanins belong to a large class of
Flavonoids
Flavonoid’s general structure
: two aromatic rings fused together
and connected by a single bond to a third aromatic ring
What R groups can be present on flavonoids
R groups can be H, OH, or OCH 3
Anthocyanins are water/lipid soluble?
Water
Color change in anthocyanins
Colors change with changes in pH: stronger colors in acidic solution .
Additional variability in the structure of anthocyanins is due to
glycosylation
What does it mean that antocyanins are glycosylated
: anthocyanins isolated from plants are glycosylated,
meaning that one (or more) of the OH groups is attached to a sugar
by a glycosidic bond.
Characteristics of carotenoids ( solubility, what color, saturation)
Fat soluble and highly unsaturated molecules responsible for orange
and yellow colors in nature.
Beta-carotene is the precursor to
Vitamin A , from 1 beta carotene-> 2 vitamin A
Lycopene : where found , what color
Lycopene (tomatoes, red carrots)
Lutein: where fund , what color
Lutein (leafy green vegetables, color is masked by chlorophyll; added
to chicken feed to make egg yolks darker yellow)
Color of salmon is due to
carotenoids in their diet of
shrimp and krill (smaller crustaceans) become incorporated in the fish
flesh.
What happens to farmed salmon if it is fed with plant-based diet
grayish flesh so carotenoids are added to their feed (representing
15 20 % of the total cost of the feed)
What is annatto
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.
saffron: what pigment and where found
is a carotenoid found in the crocus stamen that provides both
color (yellow) and flavor
Carotenoids, anthocyanins and chlorophyll are what for plants
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
Are phytochemicals have health effect?
Not yet determined
Myoglobin and hemoglobin have what component in the structure
Fe2+
Red color of fresh meat is due to
The red color of fresh meat is due to the binding of oxygen (in the air)
to the heme group of myoglobin.
What happens with color of meat over time
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.
CO and Fe2+ produce what color
Cherry-red color
What happens with modified packaging and meat in US
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
CO, meat and canadian regulations
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 .
The color change that occur to the meat when it is cooked is due to
denaturation of myoglobin .
Why cured meat is pink
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.
Tannins are
Tannins are a large group of polymeric polyphenolic compounds
occurring in plants and soil: black brown yellow colors
Tannins are responsible for and found in
Astringency, responsible for the color and astringency of tea
Progression of color in maillard and caramelization reaction and it contributes to
Colors: yellow brown black
Both caramelization and the Maillard reaction are very complex and
produce both color and flavor
Influence of color on humans
Overall, color has a major psychological effect and can dramatically
affect taste perception: Jell
Our perception of flavor involves a combination of two senses:
taste
and smell
Human tongue can sense
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.
Monosodium glutamate is used as
flavor potentiator
Coffee aroma contains ___ compounds
800
Many types of volatile organic compounds contribute to aroma:
short
chain fatty acids, alcohols, aldehydes, ketones, etc.
___ are major contributors to the aroma of
onions and garlic.
Sulfur containing compounds
How much of flavor usually is in the product?
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
Banana flavor is due to what compound
Isopentyl acetate (key compound in banana aroma) has an olfactory
If studied carefully, coffee aroma of 800 can be replaced with
30-50 constituents
A key flavor category is
Essential oils
Essential oils are the essence ” of flavors associated with plant
materials:
mint, strawberry, orange, raspberry, apple, etc.
Essential oils are made up largely of \_\_\_\_ , a class of volatile hydro\_\_\_\_ molecules:
terpenes
phobic
Citral is responsible for what flavor
Lemon
Limonene is responsible for
Lime flavor
Beta-sinensal is responsible for what flavor
Orange
Nootkatone is responsible for what flavor
Grapefruit
How essential oils can be extracted from plant sources
By steam distillation
What are reaction flavors
are another important sub category of flavors: they
can be produced commercially by controlled or directed Maillard
and/or caramelization reactions.
