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Food Chemistry - FDSC251 > U2 > Flashcards

U2 Flashcards

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1
Q

definition of fatty acids

A

carboxylic acids with a short to long aliphatic chain

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2
Q

aliphatic

A

organic compounds where carbon atoms form open chains rather than rings

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3
Q

relationship between saturation and melting point

A

melting point decreases as number of double bonds increases

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4
Q

fatty acid typical characteristics

A 
unbranched
varying length and degree of saturation
4-28C
even numbered usually
usually cis
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5
Q

characteristics of short fatty acids

A
  1. more volatile
  2. lower melting point
  3. liquid at RT
  4. more soluble in water
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6
Q

characteristics of longer fatty acids

A
  1. not volatile - dont contribute to flavor
  2. higher melting point
  3. solid at RT
  4. less water soluble - more hydrophobic
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7
Q

fatty acids present in milk and plant oils

A

pentadecanoic acid and heptadecanoic acid

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8
Q

what is soap

A

the salt form of a fatty acid

water soluble and has strong surface tension reducing properties

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9
Q

nomenclature systems in saturated fatty acids

A

trivial and IUPAC

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10
Q

nomenclature systems in unsaturated fatty acids

A

IUPAC and trivial and omega

  1. -enoic acid
  2. positional reference
  3. configuration
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11
Q

IUPAC v omega naming in unsaturated fatty acids

A

IUPAC - count from COOH

omega - count from CH3

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12
Q

cis characteristics

A
  1. kinked, not linear
  2. 1 bond = 40 degree turn
  3. harder to form a lattice structure so…
  4. lower melting point
  5. lower density
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13
Q

trans characteristics

A
  1. linear
  2. metabolized like saturated fatty acids
  3. higher melting point
  4. higher density
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14
Q

trans-oleic acid is called

A

elaidic acid - a lot like stearic acid

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15
Q

unconjugated

A

double bonds are separated by a methylene group (CH2) - normal

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16
Q

conjugated

A

double bonds are adjecent. formed during processing.

more thermodynamically stable but more susceptible to autoxidation

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17
Q

mixed bonding system

A

mixture of conjugated and unconjugated. occurs since linolenic and polyunsaturated fatty acids are unstable and reactive, thus easily converted to having both conjugated and unconjugated elements

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18
Q

lattice crystalline

A

stabilized by hydrophobic interaction along acyl residues. temperature required to melt the crystal increases with number of carbons in the chain (length)

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19
Q

what can form a lattice crystalline structure? what can’t?

A

can - saturated, even, trans

can’t - unsaturated, odd

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20
Q

phenomenon that occurs when there is a cis bond at the end of the carbon chain

A

the angle the fatty acid is bent at is lower, thus the molecule is more linear and the melting point is higher

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21
Q

assumptions in omega fatty acid nomenclature

A
  1. cis

2. unconjugated

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22
Q

grouping of omega fatty acids

A

due to the relationship between unsaturated, unconjugated fatty acids there are 3 groups:

  1. w3
  2. w6
  3. w9
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23
Q

malvalic acid

A

branced fatty acid found in cottonseed oil

contains a cyclopropanic ring (triangle)

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24
Q

ricinoleic acid

A

hydroxy side chain. in castor oil

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25
Q

true or false: fats consist of one type of triglyceride

A

false: they consist of a mix of triglycerides that contribute to their physiochemical characteristics

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26
Q

how do we determine the overall fatty acid content of a fat and the relative amounts of each fatty acid?

A

gas chromatography:

  1. extract
  2. saponify - fat + NaOH –> free fatty acid
  3. methylate - convert fatty acids to volatile fatty acid methyl ethers (FAME)
  4. separate FAMEs with GC
  5. compare to FAME standards
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27
Q

3 oil sources

A

plant
animal
fish

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28
Q

where are plant sources extracted from

A

seeds and fruits of plants

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29
Q

most common plant sources

A

soybean, rapeseed, peanut

30
Q

non-edible plant sources

A

castor and linseed(flax)

31
Q

2 ways animal fats are extracted

A
  1. by-product of meat production

2. separated from milk of ruminants

32
Q

common fish sources

A

sardines, herring, menhaden

33
Q

classifications of fats and oils based on gas chromatography

A
  1. milk fats
  2. lauric acid
  3. oleic-linoleic
  4. linolenic
  5. animal fat
  6. marine
  7. erucic acid
34
Q

defining feature of milk fat group

A

high levels of long-chain saturated fatty acids. have a substantial amount of short chain fatty acids

35
Q

source of milkfat

A

milk of lactating ruminants - cows, goats, yaks, sheep, water buffalo

36
Q

source of rancid odor in milkfats

A

short chain fatty acids released by lipolysis (also responsible for aged cheese flavor)

37
Q

do milkfats contain unsaturated fatty acids? what kind?

A

yes; trans due to biohydrogenation in the rumen by microbes

38
Q

defining feature of lauric acid group

A

high content of lauric acid (C12). mostly saturated, but since the fatty acid chains are short they exist as oils

39
Q

source of lauric acid group

A

tropical oils (palms) - palm, coconut, babassu oil

40
Q

difference between palm kernel oil and palm oil

A

source!
palm kernel oil - palm oil seeds
palm oil - palm fruit. not in lauric acid group; more unsaturated

41
Q

true or false: lauric acid group fats are highly resistant to oxidative rancidity

A

true! low degree of unsaturation

42
Q

defining feature of oleic-linoleic group

A

predominantly long-chain oleic and linoleic fatty acids. rarely C18:3. 20% saturated fats

43
Q

sources of oleic-linoleic group

A

cottonseed, sunflower, safflower, olive, peanut, corn

44
Q

true or false? oleic-linoleic group undergoes reversion

A

false - rarely has C18:3 and this group is relatively stable

45
Q

formation of shortening

A

partial hydrogenation converting oleic-linoleic group to plastic edible fats

46
Q

defining feature of linolenic group

A

very high polyunsaturated fatty acid content - linolenic, oleic, and linoleic acids - contributing to its high reactivity and ease of oxidation

47
Q

function of linolenic group

A

paint - polymerizes into a hard film if applied as a thing layer on a surface

48
Q

sources of linolenic acid group

A

soybean, linseed, castor, hempseed, perilla

49
Q

what is reversion and what oil does this happen to

A

rapid transition from bland, tasteless oil to grassy, hay-like and eventually fishy flavor. occurs in processed (but not modified) soybean oil

50
Q

how to fix reversion

A

hydrogenation - converts linolenic to oleic or linoleic acids

51
Q

soybean oil functions

A

industrial drying oil traditionally. now it us edible due to plant breeding and food technology

52
Q

defining feature of animal fat depot group

A

high melting point though the unsaturated fatty acid content is similar to that of the oleic-linoleic group

53
Q

why is animal fat solid at room temperature despite it’s composition

A

fatty acid distribution on the glycerol backbone. higher ratio of di-saturated and tri-saturated glycerides, affecting the crystal forms

54
Q

defining feature of the marine oil group

A

low levels of saturated fatty acids and high levels of long-chain unsaturated fatty acids

55
Q

marine oil fatty acids are sources of

A

omega 3
EPA
DHA

56
Q

true or false: marine oils are reactive

A

true due to its unsaturated fatty acid content, they readily undergo reversion and are highly susceptible to autoxidation

57
Q

sources of erucic acid group

A

rapeseed and mustard oil

58
Q

function of rapeseed oil

A

marine motor oil due to its lubricating properties

59
Q

defining feature of erucic acid group

A

high levels of erucic acid (health hazard)

60
Q

how is canola oil produced

A

rapeseed oil is plant bred into a low erucic acid composed oil. makes it edible

61
Q

Animal fat is solid because

a. It has a higher ratio of desaturated and trisaturated glycerides
b. It has a higher amount of saturated fatty acids than unsaturated

A

a

62
Q

oleic acid 18:1 cis-9 is considered

a. N3 fatty acid
b. N6 fatty acid
c. N9 fatty acid
d. Not an omega acid

A

c

63
Q

Long chained polyunsaturated cis fatty acids…

a. Give better packed, more stable crystalline lattice that requires high temperature to melt
b. Give less stable crystalline lattice than their isomers thus the melting point is less
c. Have no effect on the stability of the crystalline lattice

A

b

64
Q 
The melting point of fatty acids is affected by:
A.	Chain length
B.	Number of double bonds
C.	Double bond configuration
D.	All
E.	None
A

d

65
Q

all-cis-docosa-4,7,10,13,16,19-hexa-enoic acid is a fatty acid that contains

a. 26 carbon atoms with 6 cis double bonds
b. 22 carbon atoms with 6 cis double bonds
c. 26 carbon atoms with 6 trans double bonds

A

a

66
Q

True or false?

Branched FA with odd number of carbon atoms aren’t very common in food.

A

true

67
Q

A carboxylic acid with a short to long aliphatic chain is a…

A

fatty acid

68
Q

By increasing the number of double bonds in a fatty acid, its melting point will

a. Increase
b. Decrease
c. none

A

b

69
Q

Octadeca-9,12,15-trienoic acid is a fatty acid with…

a. 18C atoms and 3 double bonds
b. 9C atoms with 3 double bonds
c. 18C atoms with no double bonds

A

a

70
Q

Double bonds that are next to each other and not interrupted by a methylene group are called…

A

conjugated

71
Q

When the 1st double bond is located on the 3rd carbon atom starting the count from CH3 end, this fatty acid is labelled as…

A

omega 3 (w3)

Food Chemistry - FDSC251 (10 decks)

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