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FDSC251 > 2-FA > Flashcards

2-FA Flashcards

1
Q

what is the chemical structure of carboxyl group in fatty acid?

A

CH3-(CH2)n-COOH

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2
Q

aliphatic chain meaning?

A

FA part of the compound

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3
Q

which is the simplest and least reactive FA, SFA or UFA?

A

SFA. they are unbranched naturally.

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4
Q

how many numbers of FA are found naturally?

A

4-28, even numbers.

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5
Q

what are the 2 FA present in milk?

A

pentadecanoic (15C) and heptadecanoic (17C) FA

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6
Q

Rule of melting point of FA vs. number of double bond?

A

melting point decreases as number of DB increases ( = the more unsaturated the FA, lower the MP)

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7
Q

Rule of solubility of FA vs. chain length

A

shorter the length, bigger and solubility (due to less hydrophobicity)

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8
Q

Can FA dissolve in water? any example?

A

Yes, C4-C8 FA. miscible in water

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9
Q

What is soap?

A

salt form of a FA, water soluble + has strong surface tension reducing properties.

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10
Q

What is the name of reaction for FA to become trans from cis?

A

hydrogenation

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11
Q

how does hydrogenation do to oil conversion?

A

oil becomes plastic fats.

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12
Q

which food product naturally contain trans FA? How does this happen?

A

butter

by rumen microorganisms

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13
Q

What does conjugated DB and unconjugated DB mean?

A

Conjugated DB = DB are right next to each other (happens in oil processing); uncon— DB are seperated by methylene group [natural state of most FA]

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14
Q

which is more stable: con and uncon DB?

A

Conjugated DB is more stable but more susceptible to autoxidation.

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15
Q

give an example of FA that contains all unconjugated DB?

A

Linolenic acid (omega 3)

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16
Q

what kind of bond system does linolenic acid has?

A

mixed bonding system

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17
Q

What does mixed bonding system create for the double bond?

A

It creates active methylene group btw conju and uncon DB.

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18
Q

what are advantages and disadvantage of mixed bonding system?

A

good: is preferred thermodynamically
bad: very susceptible to autoxidation

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19
Q

explain Reversion phenomenon; which system is responsible for this?

A

appearance of bad flavor of soybean + fish oils due to less oxidation than required which produces true rancidity;
this is brought by mixed bonding system

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20
Q

The lattice crystalline structure of acyl residues is stabilized by which chemical interaction?

A

By hydrophobic interactions

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21
Q

which structure of FA can be packed into a crystalline lattice?

A

even-numbered + saturated FA

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22
Q

how does melting point change with increasing number of cis DB?

A

T decreases

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23
Q

what is an omega FA? what is the assumption?

A

omega carbon counted from CH3 end.

assumption: all natural FA are in cis form & DB will be always unconjugated.

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24
Q

example of omega FA?

A

linoleic acid; arachidonic acid (omega 6)

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25
Q

which omega 6 FA can’t be synthesized by human body?

A

linoleic acid

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26
Q

which omega 3 FA is synthesized only by plants?

A

gama-linolenic acid

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27
Q

which group of FA has anticarcinogenic effects?

A

conjugated linoleic acid (CLA)

ex. most common Rumenic acid

28
Q

What are food source of CLA?

A

milk, meat, butter

29
Q

what are branched chain FA?

A

have a hydrocarbon branch in the chain

30
Q

Which FA is found in cottonseed oil? what is special about this FA?

A

Malvalic acid.

it contains a cyclopropanic ring —-cause egg color problem

31
Q

Give a food source of Hydroxy acid?

A

castor bean tree (蓖麻油)

32
Q

Give an example of hydroxy acid.

A

ricinoleic acid —-and makes up 80% of castor oil.

33
Q

what is acetylenic FA, how is it being used?

A

contain a triple bond, used as antifungal

34
Q

is there a simple analytical method for separating, isolating and identifying individual TAG?

A

NO

35
Q

4 steps to determine FA composition of TAG

A
  1. extract
  2. saponify (+NaOH)
  3. methylate —-convert it to FAME (FA methyl ester) and seperate FAME using GC
  4. identify + quantify
36
Q

Give example of plants that produces oil ?

A

soybean, canola, peanut, olive, coconut, cocao, palm, corn, cottonseed

37
Q

give an example of animal that is important source of milk fat?

A

water buffalo

38
Q

Which tool is always used to characterize fat and oil?

A

GC - gas chromatography

39
Q

what are characteristic of milkfat in terms of its chemical structure?

A

high levels of LCSFA; unique: a lot SCFA (<12C), ex. butyric acid (C<4)

40
Q

Which FA of milkfat is responsible for rancid like odor?

A

SCFA by lipolysis

41
Q

what good aspect of flavor does SCFA of milkfat has in food?

A

it is responsible for desirable flavor of aged cheese.

42
Q

is butter water in oil / oil in water emulsion?

A

water in oil

43
Q

what food is lauric acid (C12) derived from?

A

Palm

44
Q

what is the difference between palm oil and palm kernel oil?

A

Palm kernel oil: extracted from palm oilseed;

palm oil: extracted from palm fruit

45
Q

Is palm kernel oil part of the lauric acid group? is it SFA or USFA?

A

NO, since it is extracted from palm oilseed’

it is USFA

46
Q

Is lauric acid oil / fat in room T with large level of saturation?

A

Oil. due to C12

47
Q

Is lauric acid susceptible to oxidation?why

A

No, due to low degree of unsaturation.

48
Q

which group of FA does sottonseed, olive, peanut and corn oil belong to?

A

oleic-linoleic acid

49
Q

what are the major FA contained in oleic-linoleic acid group? which FA is in low proportion (<20%)?

A

predominate: long chain: oleic (18:1) + linoleic (18:2)

SFA is in low proportion; C18:3 in trace amount

50
Q

is olive, peanut and corn oil relative stable? To which phenomenon?

A

Yes, they don’t suffer from Reversion; and May be turned into
plastic edible fats by partial hydrogenation

51
Q

which FA is used in conjunction with oleic and linoleic acid`?

A

linolenic (C18:3)

52
Q

what are disadvantages of linolenic acid?

A

reactive + readily oxidized

53
Q

Which group of FA is referred as “drying oils” ?

A

Linolenic acid. because of their ability to polymerize into a hard film if applied as
a thin layer on surfaces

54
Q

which group of FA does soybean, linseed, casto, hempseed and perilla oil belong to? which is used originally an industrial drying oil?

A

linolenic acid

Soybean.

55
Q

how does Reversion change soybean oil?

A

rapid transition from a bland, tasteless oil shortly after processing to
grassy, hay‐like and then fishy flavor

56
Q

how to overcome Reversion of soybean?

A

by hydrogenation to convert a substantial portion of linolenic —->oleic + linoleic acid

57
Q

which animal are lard and tallow from?

A

lard-pig

tallow-sheep + cattle

58
Q

does animal fat depot group contain high or low melting point?

A

high.

59
Q

is lard and tallow fat / oil? why ?

A

they are fat.
bc animal fat depot group has a higher ratio of di‐saturated (gs2u) and
tri‐saturated (gs3) glycerides than oleic‐linoleic acid group

60
Q

can GS3 or GS2 change lipid system? how does it change?

A

GS3

change from an oil to a fat

61
Q

What are characteristics of fish oils？

A
  • Contain low levels of saturated fatty acids

- High in long‐chain unsaturated fatty acids [very high degree of saturation]

62
Q

is marine oil susceptible to autoxidation? why?

A

yes due to VERY HIGH degree of unsaturation.

63
Q

Give example of erucic acid (C22)?

A

rapeseed oil 油菜籽; mustard oil 芥末油

64
Q

What is rapeseed oil originally used for?

A

marine motor oil—-excellent lubricating property due to erucic acid.

65
Q

Why rapeseed oil a health hazard? how does it become edible today?

A

bc 40-50% erucic acid;

it is changed into low erucic acid —-“canola oil”

FDSC251 (2 decks)

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