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food chem 1 > 3 Fat Forms > Flashcards

3 Fat Forms Flashcards

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1
Q

how is solid fat content commonly determined?

A

nuclear magnetic resonance (NMR) measurement

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2
Q

what does dilatometry measure

A
  • change in specific volume per unit temperature

- it is the INVERSE of DENSITY

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3
Q

how is dilatometry done?

A
  • take ur fat
  • stick it in a reservoir
  • have a capillary attached
  • measure its expansion
  • keep track of temperature change increments
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4
Q

what kind of curve do you get from a specific volume vs temperature graph? (dilatometry)

A
  • sigmoidal (S shape)
    1) thermal expansion of fat
    2) expansion due to change in state
    3) thermal expansion of liquid only
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5
Q

on a dilatometry curve, what do the top and bottom “lines” depict?

A
  • top = liquid line
  • bottom = solid line
  • enables the calculation solid:liquid ratio if they are PARALLEL
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6
Q

what is the ratio of solid:liquid at a specific temperature called?

A

solid fat index

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7
Q

how is the solid fat index calculated?

A

%solids = (X/Y)*100

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8
Q

expand SFC

A

solid fat content

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9
Q

what does NMR measure?

A

nuclear spin: alignment of nuclei in a magnetic field

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10
Q

what’s the procedure for pulsed NMR when determining SFC?

A
  • take ur fat
  • stick it in a magnetic field
  • give it a nice radio frequency (RF)
  • make sure this RF is perpendicular to the field (90° RF pulse)
  • record the free induction decay (FID) signal
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11
Q

what’s the FID?

A
  • free induction decay
  • accompanies the relaxation of H magnetic spins after they’re disturbed by the RF pulse
  • solids relax faster than liquid
  • shape of FID determines proportion of solid/liquid content
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12
Q

which is more time consuming? NMR or dilatometry?

A

dilatometry

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13
Q

define polymorphism

A

occurrence of several different crystal forms for a single compound

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14
Q

what are the most common polymorphic forms for fats?

A

alpha, beta prime, and beta

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15
Q

alpha, beta prime, and beta: which has the highest melting point? which is most stable?

A

beta for both

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16
Q

what does triclinic beta look like?

A

looks like someone sat on a box

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17
Q

what does orthorhombic beta-prime look like?

A

a healthy box

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18
Q

what does hexagonal alpha look like?

A

a healthy cube

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19
Q

what are the names of the 3 crystal forms?

A

triclinic, orthorhombic beta-prime, hexagonal alpha

20
Q

what are the names of the TG spacial arrangements?

A

tuning fork, chair form

21
Q

which carbons are arranged 180° from each other in the chair form?

A

2 and 3

22
Q

how are alpha polymorphic forms spatially arranged?

A

vertical tuning fork

23
Q

how are beta prime polymorphic forms spatially arranged?

A

tilted tuning fork

24
Q

how are beta polymorphic forms spatially arranged?

A

stacked chair (they also appear slanted)

25
Q

what kind of transformations can crystal structures undergo?

A
  • simple collapse (tuning fork to slanted tuning fork)

- cataclysmic chain shift (tuning fork to slanted chair)

26
Q

what analytical methods are used to study polymorphism?

A

1) x-ray diffraction
2) microscopic
3) infrared spectroscopic (IR)
4) thermal

27
Q

what are the characteristics of the ALPHA polymorph dictated by x-ray diffraction?

A

remember: this is the least stable. so…
- hexagonal
- tuning fork
- acyl groups oriented 90° to plane of glyceryl group
- vertical chain
- longest spacing
- randomly ordered
- loosely packed

28
Q

what are the characteristics of the BETA-PRIME polymorph dictated by x-ray diffraction?

A
  • orthorhombic
  • tuning fork
  • acyl groups tilted 68-70° from plane of glyceryl group
  • tilted chain
  • intermediate spacing
  • kinda ordered
  • moderately packed
29
Q

what are the characteristics of the BETA polymorph dictated by x-ray diffraction?

A

remember: this is the most stable. so…
- triclinic
- chair
- acyl groups tilted 59° from plane of glyceryl group
- tilted chain
- shortest spacing
- highly ordered
- closely packed

30
Q

what are the characteristics of the ALPHA polymorph dictated by microscopic analysis?

A
  • platelet

- 5 micro

31
Q

what are the characteristics of the BETA-PRIME polymorph dictated by microscopic analysis?

A
  • fine needle

- 1 micro

32
Q

what are the characteristics of the BETA polymorph dictate by microscopic analysis?

A
  • long needle

- 25-50 micro

33
Q

what are the characteristics of the ALPHA polymorph dictated by IR analysis?

A

singlet at 720/cm

34
Q

what are the characteristics of the BETA-PRIME polymorph dictated by IR analysis?

A

doublet at 719-727/cm

35
Q

what are the characteristics of the BETA polymorph dictated by IR analysis?

A

singlet at 717/cm

36
Q

what are the characteristics of the ALPHA polymorph dictated by thermal analysis?

A
  • most thermodynamically unstable

- lowest melting point

37
Q

what are the characteristics of the BETA-PRIME polymorph dictated by thermal analysis?

A
  • thermodynamically unstable

- intermediate melting point

38
Q

what are the characteristics of the BETA polymorph dictated by thermal analysis?

A
  • thermodynamically stable

- highest melting point

39
Q

what colors are the polymorphs?

A

alpha: translucent
bet-prime: in between
beta: opaque

40
Q

how are alpha polymorphs formed?

A

rapid cooling of liquid fat

41
Q

how are beta-prime polymorphs formed?

A
  • slow cooling of liquid fat

- transformation of alpha

42
Q

how are beta polymorphs formed?

A
  • very slow cooling of liquid fat

- transformation of beta-prime

43
Q

which polymorph has the highest activation energy?

A

beta

44
Q

what oils prefer to form beta polymorphs?

A
  • coconut
  • corn
  • olive
  • lard
  • palm kernel
45
Q

what oils prefer to form beta-prime polymorphs?

A
  • cottonseed
  • herring
  • tallow
  • milk fat
  • palm oil

food chem 1 (12 decks)

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