Midterms [Lipids] Flashcards
(70 cards)
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
Emulsifier
- stands in between oil and water and holds/combines them together
- makes an emulsion stable
25
Functions of emulsifiers
- promote emulsion stability
- stabilize aerated systems like ice cream, mayonnaise
26
How does emulsifiers work
- they reduce surface tension between the two immiscible phases
27
Cephalin
- contain ethanolamine or serine in place of choline in lecithin
- prevalent in brain tissue
28
Sphingomyelins
- with a fatty acid in amide linkage on the amino group
- concentrated in brain and tissue
29
Glycolipids
- portion of molecule is formed by carbohydrates
30
Sterols-cholesterol
- a high molecular weight cyclic alcohol found in high amounts in egg yolk
31
Bile acids
- found in the bile combined by the way of their carboxylic groups with the amino acid glycine
32
Triglycerides
- ester derived from glycerol and three fatty acids
33
Biological functions of lipids
- chemical messengers
- storage and provision of energy
- maintenance of temperature
34
Functions of lipids in foods
- contribute to many desirable qualities of foods
- texture, structure, mouthfeel, flavor, and color
35
Rancidity
- water and oil creates bad smell
36
Hydrolytic rancidity
- involves moisture/water
- ester linkages of lipids are subject to hydrolysis by enzymes
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Oxidative rancidity
- involves oxygen
- dominant in unsaturated fatty acids
38
Lipid deterioration
- lipolysis seriously degrades the quality of fat systems
39
Antioxidants
- retard the rate of oxidation
40
Function of antioxidants
- they direct the breakdown of peroxides into stable substances that do not promote further oxidation
41
Mechanism of antioxidants
- RO + AH -> RH (AH = antioxidants)
- ROO + AH -> ROOH + A
42
Synthetic antioxidants
- butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate (PG), and tert-butyl-hydroquinone (TBHQ)
43
Natural antioxidants
- ascorbic acid, tocopherols, carotene
44
Methods measuring lipid quality
- saponification value/number
- iodine value/number
- refractive value
- acid value
- peroxide value
45
Saponification
- product of soap using fat with a reaction of an alkali
46
Saponification value/number
- 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
Potassium laurate
- Alcohol + Alkaline = potassium salt
48
Steps in saponification
1. Draw the structure to show the reaction
2. Label each part of the reaction
3. Calculate for molecular weight (H=1, C =12, O=16, K=39)
4. Ratio and proportion
5. Find how many g of KOH to saponify 1g of trilaurin
49
Iodine number
- 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
More unsaturated
- more liquid (oil)
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More saturated
- more solid (fat)
52
Calculations of iodine number
1. Draw the structure
2. Calculate the molecular weight
3. Show the reaction
4. Round off to the whole number
53
Acid number
- measure of the number of carboxylic acid groups in a chemical compound, such as fatty acid, or in a mixture of compounds
54
Refractive index
- 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
Peroxide value
- 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
Modification of lipids
- to improve their functional properties such as oxidative stability, flavor properties, nutrient content
57
Hydrogenation
- addition of hydrogen to split double bonds and produce single bonds
- unsaturated to saturated at 60C with catalyst
58
Reasons for hydrogenation
- 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
Interesterification
- 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
Chemical Interesterification
- use sodium methoxide as a catalyst
- to shift the fatty acid of the triglycerides
- randomly darken the oils
61
Enzymatic Interesterification
- using lipases from bacterial, yeast, and fungal sources
- require less severe reaction conditions, easily purified products
- expensive
62
Application Interesterification
- modification of lard (pork fat)
- grainy texture, poor appearance, and poor creaming capacity
63
Fractionation
- 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
Application of Fractionation
- manufacturers of margarines and cooking fats because it can partly replace the incorporation of hydrogenated fats
- reduction of trans fats
65
Chemistry of frying
- exchange of water in food and oil
- results in distinctive fried flavors and undesirable off-flavors if the oil is overly deteriorated
66
Off-flavors in frying via
- hydrolysis
- oxidation
- polymerization reactions
67
Factors that control hydrolysis of triacylglycerols and glycerols
- oil temperature
- interface area between oil and aqueous phases
- water level
- steam level
68
Polymerization
- reaction takes place during frying
69
Degradation products..
- negatively affect not only flavor and safety but also color and texture of the fried products
