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[LEC] Food Chemistry > Midterms [Lipids] > Flashcards

Midterms [Lipids] Flashcards

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1
Q

Lipids

A
  • naturally-occuring fat-like substances
  • generally insoluble in water
  • can be synthesized in the liver
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2
Q

Fats and oils

A

esters of long chain carboxylic acid

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3
Q

Fats

A
  • solid at room temperature
  • derived from from animal sources
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3
Q

Fats

A
  • solid at room temperature
  • derived from from animal sources
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4
Q

Oils

A
  • liquid
  • plants
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5
Q

Fatty acids

A
  • smaller units of lipids
  • long chain carboxylic acids (COOH)
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6
Q

Saturated fatty acids

A
  • single bonds only
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7
Q

Unsaturated fatty acids

A
  • has double bonds
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8
Q

In writing fatty acid names

A
  • based on carbon atoms
  • based on the number of double bonds (Cx:y)
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9
Q

Monounsaturated

A
  • one double bond
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10
Q

Polyunsaturated

A
  • two or more double bonds
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11
Q

x-Omega fatty acid

A
  • x = At what carbon the the double bond is found
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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)
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13
Q

Simple lipids

A
  • fats, oils, and waxes
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14
Q

Compound lipids

A
  • phospholipids, glycolipids, lipoproteins
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15
Q

Derived lipids

A
  • carotenoids, steroids, bile acids
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16
Q

Carotenoids

A
  • precursor/source of vitamin A
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17
Q

Esterification

A
  • reaction between a carboxylic acid and an alcohol to form ester and water
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18
Q

Free fatty acids

A
  • they occur primarily esterified to glycerol
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19
Q

Waxes

A
  • esters of fatty acids and alcohols
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20
Q

Cholesteryl palmitate containing cholesterol

A
  • wax found in the blood plasma
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21
Q

Essential fatty acids

A
  • body cannot produce and must be added into or obtained from the diet
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22
Q

Non-essential fatty acids

A

body can produce or synthesize

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23
Q

Phospholipids (phosphatides)

A
  • names as the derivative of the parent compound
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24
Q

Emulsifier

A
  • stands in between oil and water and holds/combines them together
  • makes an emulsion stable
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25
Q

Functions of emulsifiers

A
  • promote emulsion stability
  • stabilize aerated systems like ice cream, mayonnaise
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26
Q

How does emulsifiers work

A
  • they reduce surface tension between the two immiscible phases
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27
Q

Cephalin

A
  • contain ethanolamine or serine in place of choline in lecithin
  • prevalent in brain tissue
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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
  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
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
  1. Draw the structure
  2. Calculate the molecular weight
  3. Show the reaction
  4. 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

[LEC] Food Chemistry (2 decks)

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