U1 Flashcards
4 things that characterize lipids
- solubility in non-polar organic solvents, not water
- hydrophobic
- fatty mouthfeel and aroma
- lubricant properties when isolated
classifications of lipids
simple lipids, compound lipids, derived lipids
simple lipid definition
esters of fatty acids connected to an alcohol (triglycerides are a glycerol molecule esterified to 3 fatty acids)
major lipid we consume
triglycerides - make up >90% of extractable lipids in biological systems
classifications of simple lipids
fats and waxes
fat v oil
fat - solid at room temp
oil - liquid at room temp
difference between edible fat and pure triglyceride
edible consists of a mixture of many different types of triglycerides (many differences on fatty acid length and saturation), so they melt of a wider range than pure triglycerides
wax definition
fatty acids esterified with an alcohol rather than a glycerol
examples of waxes
jojoba oil (linear monounsaturated fatty acids with fatty alcohols - liquid at room temp) bees wax (solid at room temp)
applications for waxes in food
sealing agent = cheese
polishing agent = apples
low calorie fat substitute (can’t be digested)
when is a wax biologically active
when the fatty acids are esterified to a complex alcohol - cholesterol or vitamin A or retinol. includes a ring structure
compound lipid definition
made of simple lipids conjugated to a non-lipid molecule
kinds of compound lipids
phospholipid
glycolipid/sphingolipids
lipoproteins
phospholipid structure
glycerol, 2 fatty acids, phosphate group, head group
characteristics of phospholipids
amphipathic
emulsifiers
complex mixture of different head groups
commercial emulsifier
soybean oil
lecithin
phosphatidyl choline
phosphatidic acid
hydroxyl group
cephalin
phosphatidyl ethanolamine
phosphatidyl inositol
phosphate group esterified with an inositol 6 carbon ring
phosphatidyl serine
phosphate group esterified with the hydroxyl group of serine AA
phsophatidyl glycerol
glycerol head group
found in chloroplasts
cardiolipin
diphosphatidyl glycerol
beef heart and green plants
plasmalogen
CH2-CH2-N+H3
sphingolipids/glycolipids
glycerol-like backbone, fatty acids, carbohydrate and/or nitrogenous group
NO GLYCEROL
where are sphingolipids and glycolipids
associated with membrane lipids - plants and animals
sphingolipid structure
sphingosine, fatty acid, head group
ceramide
sphingolipid with head group -H
sphingomyelin
sphingolipid with head group phosphocholine
glycolipid structure
carbohydrate esterified to a lipid
glycero-glycolipid structure
carbohydrate esterified to a glycerol - fatty acids
sphingo-glycolipids
carbohydrate esterified to a glycerol - fatty acid and nitrogenous group
lipoproteins
protein-lipid complex; unknown structure
HDL
high density lipoprotein - protective mechanism that carries cholesterol out of the blood to the liver
LDL
low density lipoprotein - transports vital substances, but excess leads to accumulation in blood vessels
derived lipids
derived from simple or compound lipid categories; still retain hydrophobic character
categories of derived lipids
- fatty acids
- alcohols and sterols
- hydrocarbons and oxygenated derivatives
fatty acids
chains of aliphatic hydrocarbons with a carboxyl group at one end
short fatty acids contribute to
flavor when released by lipolysis
long fatty acids contribute to
soapy flavors when with mineral salts
why are free fatty acids bad in frying oils
lower smoke point
alcohols and sterols defining feature
> C6 fatty alcohols - have a hydroxyl group. 4 ring strucutre + hydroxyl makes it amphipathic
short alcohols and sterol
flavor
long alcohols and sterols
biologically active
ex. cholesterol
examples of other hydrocarbons/oxygenated derivatives
- aliphatic hydrocarbons
- carotenoids
- xanthophylls
- terpenes
what kind of hydrocarbon/oxygenated derivative is of highest interest for food chemists and why
terpenes. since they’re build from isoprene units they are componenets of fragrant oils
fundamental isoprene unit
5 carbons
what are the components of essential oils
monoterpenes (2 isoprene units - 10C) and sesqueterpenes (3 isoprene units - 15C)
nutritive value of triglycerides
9kcal/g
37kJ/g
source of essential fatty acids and vitamins
lipid function in food
- mouthfeel - creamy/oily
- solubitizes taste and aroma constituents of food
- acheive a desired texture, aroma, and mouthfeel
- emulsifiers - phospholipids
True or False: Lipids are classified by their hydrophobicity, insolubility in water and solubility in non-polar organic solvents?
True
Fats are made of
a. any alcohol esterified to a fatty acid
b. an alcohol with a single hydroxyl group esterified to a fatty acid
c. glycerol esterified to fatty acids
c
A substance that stabilizes an emulsion by increasing its kinetic stability is …
a. Emulgent
b. Emulsifier
c. Surfactant
d. All
e. none
B
Phospholipids are soluble in water and lipids because…
A. Small molecular weight
B. Hydrophobic and hydrophilic
C. High refractive index
B
Derived lipids are important to food science because…
a. Bioactive properties
b. Nutritional value
c. Functional properties
d. All
e. none
D
A diglyceride linked to a phosphate and a nitrogenous base is…
a. Sphingolipid
b. Phospholipid
c. Glycolipid
b
In lecithin, the hydrophilic nitrogenous base is
a. Ethanolamine
b. Serine
c. choline
c
True or false?
Ceramide is a phospholipid.
False - sphinolipid
Carotenoids are important because of their…
a. Nutritional value as precursors of vitamin A
b. Technological properties as natural food colorant
c. None
d. Both A and B
d
True or False?
HDL contains more cholesterol than LDL.
false - cholesterol/lipids are low density, so high density lipoproteins contain relatively more proteins
