FDSC 200 Midterm 2

Describe phospholipids. What is the structure? Give an example of what it is found in.

- 5% of extractable biological lipids
- glycerol base with 2 fatty acids and a phosphorus-containing acid attached
- both hydrophilic (phosphorus) and hydrophobic (fatty acids) groups
- natural emulsifiers
- components of egg yolk lecithin

Why are phospholipids important?

- they are part of cell membranes and help transport fats in and out of cells
- help fats stay mixed in water-based solutions

Give examples of some sterols.

- vitamin D
- steroid hormones (sex hormones)
- cholesterol, a part of every cell

What is the role of cholesterol?

the body uses cholesterol to produce hormones and build cell membranes.

What is cholesterol found in? What does excess blood cholesterol lead to?

found in animal products
leads to atherosclerosis

How is cholesterol transported throughout the body? (specifically)

lipoproteins
- low density lipoproteins (LDL) carry cholesterol to the liver
- high density lipoproteins (HDL) find unneeded cholesterol and return it to the liver

What does high levels of LDL mean? how can you maintain LDL and HDL at healthy levels? (5)

High levels of LDL means a higher risk of developing atherosclerosis
Recommendations:
- limiting saturated fat and cholesterol intake
- exercising regularly
- maintaining a healthy weight
- reading food labels carefully, especially fat fat-free, low-fat, and cholesterol-free options as they may have added salt and sugar
- consume 20-35% of daily calories from fat, mainly from polyunsaturated and monounsaturated fatty acids

To create a stable mixture of water and oil, we have to use a(n)......

emulsifier

What is the main component of many foods?

water

What is the only substance found in abundance in the solid, liquid, and gaseous state?

water

What are the nutritional roles of water? (3)

- helps control body temp
- transports nutrients and waste products
- provides the solution for metabolic reactions

What are the non-nutritional roles of water (in food)?

- influences texture, appearance of food
- important heat medium in cooking
- important solvent for cleaning and sanitation
- critical in food preservation
- determines the likelihood of food spoilage by its presence or absence

H2O is held together by what kinds of bonds?

polar covalent (unequal sharing of electrons)
hydrogen bond

Why are H2O bonds unequal?

the positive hydrogen end of one water molecule is drawn to the negative oxygen ends of other water molecules (hydrogen bond)

What is surface tension? What does it allow? (4)

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

What forms hydrogen bonds with water?

sugars, starches and proteins

How does atmospheric pressure impact the boiling and freezing points of water? how does this affect baking?

- water boils at lower temperatures at high altitudes (quicker) and at higher temperatures at low altitudes (slower)
- high altitude baking considerations such as increasing the amount of flour, water content, and oven temp need to be considered

An impurity in water may change its....? (4)

- physical and chemical characteristics
- flavour and colour
- boiling and freezing points
- hydrogen bonding

The unusual high boiling point of water is explained by its intermolecular \______

hydrogen bonding

True or false: steam is as hot as boiling water.

True, when not under pressure. It is hotter than water under pressure

What is better to heat food with - steam or water?

steam leaves food more flavorful and nutritious than boiling
(also leavens baked goods)

What is partially responsible for the taste in water?

oxygen

name 2 gas solutes dissolved in water

CO2 and O2

give some examples of liquid in water solutions.

alcoholic beverages, vinegar and fruit juice concentrates

What happens to the freezing point and boiling point if salt or sugar are dissolved in water?

lower the freezing point and increase boiling point

give some examples of solid in water solutions

tea, coffee

The amount of water present in a food product is strongly related to its \______

perishability

Why is the amount of water present in food related to its perishability?

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

Water becomes part of the structure of food in what 3 ways? Why does this matter?

1. free water
2. hydrate water
3. bound water
the water type impacts perishability.
water bound to other compounds is not available to support food spoilage. (ex: water in carrots is mostly bound to starch molecules, while in milk, it is mostly free. both at 88% water, but carrots are much less perishable)

What is free water?

- easily separated from food tissue
- often contains dissolved compounds
- boils and freezes easily
- readily evaporates when foods are dried

What is hydrate water?

- any compound loosely bound with water
- must be boiled to be free of water, known as anhydrous

what does anhydrous mean?

contains no water

what is bound water?

tied to the structure of larger molecules
does not easily freeze or boil
chemically reacts as part of the larger molecule

Why are plant cells rigid?

filled with water. Responsible for juiciness or crispiness of harvested fruits and veg

loss of water from food results in.....

textural changes

What is water activity? Give the equation. What is the scale? The higher the number is..........

a measure of available (mobile) water in a food system. Takes into account the water available to support enzyme activity and microorganism growth.
Aw \= P/Po, where P \= partial vapor pressure of water over a sample of food, and Po \= partial vapor pressure of pure water
scale \= 0-1.0 (pure water). The higher the number is, the more perishable the food will be.

What is more perishable - canned or dried foods?

canned

Food preservation by removal of water is based on what 3 techniques?

- dehydration/drying
- concentration (removal of some of the water)
- freezing

True or false: two products can have the same moisture content but different water activities.

True - the water may be bound in one more than the other

What are the 4 main function of water in the body?

- maintain body temp
- transport nutrients and waste products
- serve as a reactant in metabolism
- become part of body tissue

To reduce the water activity for a specific food product \______ water must be reduced

free

Among these food commodities, \____ has the least water content: tomatoes, cucumbers, milk, beer

milk

\______ water keep protein molecules suspended in a colloidal solution

hydrate

Give some examples of water pollutants.

- biological: bacteria, protozoa, viruses, organic waste
- chemical contaminants: metal ions such as calcium, magnesium (cause hard water), acid rain (changes pH)
- physical: garbage (cans, bottles, plastics) harbors bacteria, cause physical harm, break down toxins that enter water supply.

What causes hard water?

metal ions such as calcium & magnesium (chemical contaminants)

True or false: potable water can be used for food processing. Explain.

false: Potable water (meaning water suitable for drinking) is commonly
supplied by a municipality but usually requires further treatment to be
suitable for use in food processing
One reason: Control over a manufacturing process requires that all
factors that may contribute to variability be controlled.
For example, minerals present in municipal water may interact with
food constituents.

What is BOD?

Biological oxygen demand (B.O.D.): Amount of oxygen that aerobic
microorganisms in a body of water require to break down all the
organic matter present.
B.O.D.: milligrams of oxygen consumed per litre of sample during 5
days of incubation at 20 C

Why is food processing waste water an important environmental issue?

large amounts of organic matter present in food processing wastewater would cause high BOD so wastewater must be pretreated at food processing plant before discharge
High BOD leaves insufficient oxygen for fish

What proportion of food do major components make up (water & macromolecules)?

99%

Name a natural preservative found in cranberries

sodium benzoate

Name a pigment in carrots.

beta-carotene

name an antioxidant in veg oils

alpha tocopherol

name an acidulant in lemond

citric acid

name a proteolytic enzyme in papayas

papain

True or false: GRAS substances are considered food additives.

False: GRAS substances are not considered to be food additives and can be used as ingredients in food products without pre market approval
from FDA.

What are emulsifiers?

compounds that can keep aqueous and oil phases together in a food emulsion. Stabilize emulsions by preventing coalescence of the droplets that constitute the internal phase

How do aqueous and oil phases remain separate?

droplets of one liquid, called the internal phase, are dispersed in another liquid, called an external phase. Droplets have a tendency to aggregate and coalesce to minimize contact with the external phase (interfacial tension). Coalescence can cause "breaking" of the emulsion (separation into 2 phases)

Describe what emulsifiers are composed of?

contain both polar (hydrophilic) and nonpolar (hydrophobic/lipophilic) moities. The polar end dissolves in water and the nonpolar dissolves in oil

in an o/w emulsion, what is the internal phase and what is the external phase?

in an o/w emulsion, oil is the internal ( dispersed ) phase
and water is the external ( continuous ) phase. ) phase.

name some natural emulsifiers

lecithins
mono & diglycerides

The functionality of an emulsifier is characterized by what?

its hydrophilic & lipophilic balance (HLB)

What has higher HLB: a mono or diglyceride? why?

monoglyceride because it has 2 hydrophilic substitudes (hydroxyl groups) and 1 lipophilic substituent (fatty acyl chain)

name a major food additive that is found in foods containing significant amounts of fat

emulsifers

What type of emulsion if butter?

water in oil

What contributes to the taste of fermented foods?

organic acids produced during fermentation

What type of preservative is used in beverages such as pop and fruit juice?

acidulants (organic acids and phosphoric acids)

What is the preservative effect of acidulants? + name 2 other roles

a reduction in pH which slows down microbial spoilage
- low pH required for gel formation in jam produced with pectin
- prevent enzymatic browning in fruits and veg

What pH cut off makes a food low or high acid?

pH 4.6

What is enzymatic browning due to?

polyphenol oxidase, an enzyme that catalyzes oxidation of
polyphenol compounds present in plant cells, leads to production of brown pigments

What is nonenzymatic browning?

browning produced by Maillard reaction

To prevent botulism, canned meat products need to be sterilized at temps over 100C because canned meat is a \___ food product

low acid

What is oxidation?

Oxidation: a reaction in which an electron is removed from a
molecule by an oxidant (O2). Occurs to electron-rich compounds (unsaturated fats, beta-carotene, chlorophyll, ascorbic acid)

What is an antioxidant? How does it work as a preservative?

Antioxidant is a compound that prevents (or delays) reactions of food
components with O2.
Function by scavenging free radicals and terminating free radical chain reactions

Name some natural and synthetic antioxidants.

Natural antioxidants
- Lecithin
- Ascorbic acid (vitamin C)
- Tocopherols (vitamin E)
Synthetic antioxidants
- Butylated hydroxyanisole (BHA) butylated hydroxytoluene (BHT)
- Added to fats and oils at levels of ~ 0.01%

Oxidation reactions mechanism?

chain reactions proceed by a free-radical mechanism (species that have a single unpaired electron)

What does it mean for an antioxidant to be "sacrificial'?

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

What happens to antioxidants once they become oxidized themselves?

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

True or false: ascorbic acid is an effective antioxidant for bottled oils.

false

Milligrams of oxygen consumed per litre of sample during 5 days of incubation at 20C is \_____

BOD

Increased BOD indicates

increased water pollution with organic matter

What is a pigment?

Pigment: a natural substance that absorbs visible light and gives
color to plants or animals.

What is the result of many pigment molecules being unstable?

their colour is affected by pH, reactions with O2, or other factors. These colour changes are detrimental because colour is a key factor associated with food acceptability

Give some examples of groups of compounds that contribute to natural food colours.

chlorophylls, anthocyanins, carotenoids, meat proteins, tannins

What causes a colour change from bright green to olive brown?

conversion of chlorophyll to pheophytin (by loss of magnesium ion at the core of its structure) that can occur during processing and storage.
colour of chlorophyll is also affected by oxidation and changes in pH

Red/blue/violet pigments responsible for colours of raspberries, blueberries, eggplant...

anthocyanins

400 mg/100 g in ppm
10 mg/100 g in ppm

4000 ppm
100 ppm

What is the structure of anthocyanins?

3 ring phenolic compounds called flavanoids: 2 aromatic rings fused together and connected by a single bond to a 3rd aromatic ring

What are anthocyanins soluble in?

water

How do anthocyanin colours change with pH?

stronger colours in acidic solution

Name some additional variability in the structure of anthocyanins.

glycosylation (one or more of the OH groups is attached to a sugar by a glycosidic bond)

What are carotenoids soluble in?

fat
(highly unsaturated)

Beta carotene is the precursor of...

vitamin A

Beta carotene is found in carrots at what levels?

50-100 ppm

Name some carotenoids.

beta caroteine
lycopene
lutein

What is lutein found in?

it is a carotenoid in leafy green veg, colour is masked by chlorophyll; added to chicken feed to make egg yolks darker yellow

What makes wild salmon pink?
What about farmed salmon?

carotenoids in their diet of shrimp and krill
farmed salmon are fed mainly a plant based diet and would have a greyish flesh so carotenoids are added to their feed (15-20% of total cost of the feed)

10 mg/kg in ppm

10 ppm

What is annatto?

a food additive obtained from the seeds of a tropical shrub that contains bixin (a fat-soluble carotenoid) and norbixin (a water-soluble carotenoid) and added to foods as a colorant (ex: used in cheddar cheese)

What makes cheddar cheese orange-yellow?

Annatto, 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)

What is saffron?

a carotenoid found in the crocus stamen that provides both
color (yellow) and flavor: one of the most expensive spices in the
world.