3 Fat Forms Flashcards
how is solid fat content commonly determined?
nuclear magnetic resonance (NMR) measurement
what does dilatometry measure
- change in specific volume per unit temperature
- it is the INVERSE of DENSITY
how is dilatometry done?
- take ur fat
- stick it in a reservoir
- have a capillary attached
- measure its expansion
- keep track of temperature change increments
what kind of curve do you get from a specific volume vs temperature graph? (dilatometry)
- sigmoidal (S shape)
1) thermal expansion of fat
2) expansion due to change in state
3) thermal expansion of liquid only
on a dilatometry curve, what do the top and bottom “lines” depict?
- top = liquid line
- bottom = solid line
- enables the calculation solid:liquid ratio if they are PARALLEL
what is the ratio of solid:liquid at a specific temperature called?
solid fat index
how is the solid fat index calculated?
%solids = (X/Y)*100
expand SFC
solid fat content
what does NMR measure?
nuclear spin: alignment of nuclei in a magnetic field
what’s the procedure for pulsed NMR when determining SFC?
- 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
what’s the FID?
- 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
which is more time consuming? NMR or dilatometry?
dilatometry
define polymorphism
occurrence of several different crystal forms for a single compound
what are the most common polymorphic forms for fats?
alpha, beta prime, and beta
alpha, beta prime, and beta: which has the highest melting point? which is most stable?
beta for both
what does triclinic beta look like?
looks like someone sat on a box
what does orthorhombic beta-prime look like?
a healthy box
what does hexagonal alpha look like?
a healthy cube
what are the names of the 3 crystal forms?
triclinic, orthorhombic beta-prime, hexagonal alpha
what are the names of the TG spacial arrangements?
tuning fork, chair form
which carbons are arranged 180° from each other in the chair form?
2 and 3
how are alpha polymorphic forms spatially arranged?
vertical tuning fork
how are beta prime polymorphic forms spatially arranged?
tilted tuning fork
how are beta polymorphic forms spatially arranged?
stacked chair (they also appear slanted)
what kind of transformations can crystal structures undergo?
- simple collapse (tuning fork to slanted tuning fork)
- cataclysmic chain shift (tuning fork to slanted chair)
what analytical methods are used to study polymorphism?
1) x-ray diffraction
2) microscopic
3) infrared spectroscopic (IR)
4) thermal
what are the characteristics of the ALPHA polymorph dictated by x-ray diffraction?
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
what are the characteristics of the BETA-PRIME polymorph dictated by x-ray diffraction?
- orthorhombic
- tuning fork
- acyl groups tilted 68-70° from plane of glyceryl group
- tilted chain
- intermediate spacing
- kinda ordered
- moderately packed
what are the characteristics of the BETA polymorph dictated by x-ray diffraction?
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
what are the characteristics of the ALPHA polymorph dictated by microscopic analysis?
- platelet
- 5 micro
what are the characteristics of the BETA-PRIME polymorph dictated by microscopic analysis?
- fine needle
- 1 micro
what are the characteristics of the BETA polymorph dictate by microscopic analysis?
- long needle
- 25-50 micro
what are the characteristics of the ALPHA polymorph dictated by IR analysis?
singlet at 720/cm
what are the characteristics of the BETA-PRIME polymorph dictated by IR analysis?
doublet at 719-727/cm
what are the characteristics of the BETA polymorph dictated by IR analysis?
singlet at 717/cm
what are the characteristics of the ALPHA polymorph dictated by thermal analysis?
- most thermodynamically unstable
- lowest melting point
what are the characteristics of the BETA-PRIME polymorph dictated by thermal analysis?
- thermodynamically unstable
- intermediate melting point
what are the characteristics of the BETA polymorph dictated by thermal analysis?
- thermodynamically stable
- highest melting point
what colors are the polymorphs?
alpha: translucent
bet-prime: in between
beta: opaque
how are alpha polymorphs formed?
rapid cooling of liquid fat
how are beta-prime polymorphs formed?
- slow cooling of liquid fat
- transformation of alpha
how are beta polymorphs formed?
- very slow cooling of liquid fat
- transformation of beta-prime
which polymorph has the highest activation energy?
beta
what oils prefer to form beta polymorphs?
- coconut
- corn
- olive
- lard
- palm kernel
what oils prefer to form beta-prime polymorphs?
- cottonseed
- herring
- tallow
- milk fat
- palm oil
