Midterms [Lipids] Flashcards
1
Q
Lipids
A
- naturally-occuring fat-like substances
- generally insoluble in water
- can be synthesized in the liver
2
Q
Fats and oils
A
esters of long chain carboxylic acid
3
Q
Fats
A
- solid at room temperature
- derived from from animal sources
3
Q
Fats
A
- solid at room temperature
- derived from from animal sources
4
Q
Oils
A
- liquid
- plants
5
Q
Fatty acids
A
- smaller units of lipids
- long chain carboxylic acids (COOH)
6
Q
Saturated fatty acids
A
- single bonds only
7
Q
Unsaturated fatty acids
A
- has double bonds
8
Q
In writing fatty acid names
A
- based on carbon atoms
- based on the number of double bonds (Cx:y)
9
Q
Monounsaturated
A
- one double bond
10
Q
Polyunsaturated
A
- two or more double bonds
11
Q
x-Omega fatty acid
A
- x = At what carbon the the double bond is found
12
Q
Structure of lipids
A
- polymers of fatty acids
- typically made of a glycerol backbone, 2 fatty acid tails (hydrophobic), and a phosphate group (hydrophilic)
13
Q
Simple lipids
A
- fats, oils, and waxes
14
Q
Compound lipids
A
- phospholipids, glycolipids, lipoproteins
15
Q
Derived lipids
A
- carotenoids, steroids, bile acids
16
Q
Carotenoids
A
- precursor/source of vitamin A
17
Q
Esterification
A
- reaction between a carboxylic acid and an alcohol to form ester and water
18
Q
Free fatty acids
A
- they occur primarily esterified to glycerol
19
Q
Waxes
A
- esters of fatty acids and alcohols
20
Q
Cholesteryl palmitate containing cholesterol
A
- wax found in the blood plasma
21
Q
Essential fatty acids
A
- body cannot produce and must be added into or obtained from the diet
22
Q
Non-essential fatty acids
A
body can produce or synthesize
23
Q
Phospholipids (phosphatides)
A
- names as the derivative of the parent compound
24
Q
Emulsifier
A
- stands in between oil and water and holds/combines them together
- makes an emulsion stable
25
Q
Functions of emulsifiers
A
- promote emulsion stability
- stabilize aerated systems like ice cream, mayonnaise
26
Q
How does emulsifiers work
A
- they reduce surface tension between the two immiscible phases
27
Q
Cephalin
A
- contain ethanolamine or serine in place of choline in lecithin
- prevalent in brain tissue
28
Q
Sphingomyelins
A
- with a fatty acid in amide linkage on the amino group
- concentrated in brain and tissue
29
Q
Glycolipids
A
- portion of molecule is formed by carbohydrates
30
Q
Sterols-cholesterol
A
- a high molecular weight cyclic alcohol found in high amounts in egg yolk
31
Q
Bile acids
A
- found in the bile combined by the way of their carboxylic groups with the amino acid glycine
32
Q
Triglycerides
A
- ester derived from glycerol and three fatty acids
33
Q
Biological functions of lipids
A
- chemical messengers
- storage and provision of energy
- maintenance of temperature
34
Q
Functions of lipids in foods
A
- contribute to many desirable qualities of foods
- texture, structure, mouthfeel, flavor, and color
35
Q
Rancidity
A
- water and oil creates bad smell
36
Q
Hydrolytic rancidity
A
- involves moisture/water
- ester linkages of lipids are subject to hydrolysis by enzymes
37
Q
Oxidative rancidity
A
- involves oxygen
- dominant in unsaturated fatty acids
38
Q
Lipid deterioration
A
- lipolysis seriously degrades the quality of fat systems
39
Q
Antioxidants
A
- retard the rate of oxidation
40
Q
Function of antioxidants
A
- they direct the breakdown of peroxides into stable substances that do not promote further oxidation
41
Q
Mechanism of antioxidants
A
- RO + AH -> RH (AH = antioxidants)
- ROO + AH -> ROOH + A
42
Q
Synthetic antioxidants
A
- butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate (PG), and tert-butyl-hydroquinone (TBHQ)
43
Q
Natural antioxidants
A
- ascorbic acid, tocopherols, carotene
44
Q
Methods measuring lipid quality
A
- saponification value/number
- iodine value/number
- refractive value
- acid value
- peroxide value
45
Q
Saponification
A
- product of soap using fat with a reaction of an alkali
46
Q
Saponification value/number
A
- helps to know the amount of free fatty acids
- number of milligrams of potassium hydroxide (KOH) required to saponify one gram of fat under a specified condition
- know hydrolytic rancidity
47
Q
Potassium laurate
A
- Alcohol + Alkaline = potassium salt
48
Q
Steps in saponification
A
- Draw the structure to show the reaction
- Label each part of the reaction
- Calculate for molecular weight (H=1, C =12, O=16, K=39)
- Ratio and proportion
- Find how many g of KOH to saponify 1g of trilaurin
49
Q
Iodine number
A
- number of grams of iodine that can saturate the double bonds of a fat or oil
- determine the amount of unsaturation in fats, oils, and waxes
50
Q
More unsaturated
A
- more liquid (oil)
51
Q
More saturated
A
- more solid (fat)
52
Q
Calculations of iodine number
A
- Draw the structure
- Calculate the molecular weight
- Show the reaction
- Round off to the whole number
53
Q
Acid number
A
- measure of the number of carboxylic acid groups in a chemical compound, such as fatty acid, or in a mixture of compounds
54
Q
Refractive index
A
- a physical attribute of triglycerides
- indicated the possible chances of rancidity development in oil
- the higher the RI, the higher the chances of spoilage due to oxidation
55
Q
Peroxide value
A
- the amount of peroxide oxygen per 1 kilogram of fat or oil
- indicator of deterioration of fats
- can be used to estimate oxidation of fats
56
Q
Modification of lipids
A
- to improve their functional properties such as oxidative stability, flavor properties, nutrient content
57
Q
Hydrogenation
A
- addition of hydrogen to split double bonds and produce single bonds
- unsaturated to saturated at 60C with catalyst
58
Q
Reasons for hydrogenation
A
- provides a semi-solid fat at room temperature from an oil source
- increase oxidative stability during storage
- typical products that result include shortening and margarine
59
Q
Interesterification
A
- involves rearranging the fatty acids in a triglyceride in such a way that they become distributed randomly among the triacylglycerol molecules of fat
- change the overall melting profile, spreadability, and solid-fat content temperature profile
60
Q
Chemical Interesterification
A
- use sodium methoxide as a catalyst
- to shift the fatty acid of the triglycerides
- randomly darken the oils
61
Q
Enzymatic Interesterification
A
- using lipases from bacterial, yeast, and fungal sources
- require less severe reaction conditions, easily purified products
- expensive
62
Q
Application Interesterification
A
- modification of lard (pork fat)
- grainy texture, poor appearance, and poor creaming capacity
63
Q
Fractionation
A
- change the physical properties and the nutritional value into a higher melting and a low melting or even liquid fraction
- done either by dry process
- means altering the proportion of solid to liquid
64
Q
Application of Fractionation
A
- manufacturers of margarines and cooking fats because it can partly replace the incorporation of hydrogenated fats
- reduction of trans fats
65
Q
Chemistry of frying
A
- exchange of water in food and oil
- results in distinctive fried flavors and undesirable off-flavors if the oil is overly deteriorated
66
Q
Off-flavors in frying via
A
- hydrolysis
- oxidation
- polymerization reactions
67
Q
Factors that control hydrolysis of triacylglycerols and glycerols
A
- oil temperature
- interface area between oil and aqueous phases
- water level
- steam level
68
Q
Polymerization
A
- reaction takes place during frying
69
Q
Degradation products..
A
- negatively affect not only flavor and safety but also color and texture of the fried products
