U4 - a + b Flashcards
properties of a fat are a function of…
- fatty acid composition
2. fatty acid distribution
difference and similarity between lard and vegetable oil
similar fatty acid content
different distribution, causing lard to be solid
due to configurations of GS3 and GS2U in lard
characteristic of lard texture
grainy. fixed by interesterification
what is G2SU
glyceride with 2 saturated and 1 unsaturated fatty acid
oleopalmitostearin. forms large crystals and causes a grainy texture
when is crystal modified lard formed (CML)
intraesterification conditions
when is partially modified lard (PML) formed
random distribution conditions
when is direct interesterified lard (DIL) formed
directed interesterification (GS3)
what is interesterification
exchange of fatty acids on the glycerol backbone via heat and a catalyst. occurs between triglycerides
potential catalysts for interesterification
tin, lead, zinc, alkali earth metals
difference between interesterification and hydrogenation
both change the physical and chemical properties of the lipid, but interesterification doesn’t produce trans fats
interesterification v intraesterification
inter - between TGs
intra - within a TG
what happens when interesterification is undergone at lower temperatures ?
more saturated long-chain glycerides fractionally crystallize out
random esterification
interesterification carried out to equilibrium, assuming random distribution. occurs at low temperatures
directed interesterification
interesterification is directed away from its usual random end-point, allowing the fat to crystallize (GS3 crystallizes first)
is chemical interesterification random or directed?
random
is enzymatic interesterification random or directed?
directed - produces lipids with highly specific compositions for functional uses and mono/diglycerides for emulsifiers
catalyst used at high temperature
KOH and NaOH
catalyst used at low temperature
NaOCH3
cocoa butter melting point
sharp and at body temp
can other fats and oils be modified to produce cocoa butter?
yes! good because this reduces the amount of expensive cocoa butter needed
what can be formed as a byproduct from interesterification
mono and di glycerides used as emulsifiers
4 analytical methods for modified triglycerides
Iodine value
saponification value
gas chromatographic analysis
liquid chromatogroaphy
definition of iodine value
mass of iodine in g absorbed by 100g of a fat sample
what 2 things does IV tell us
degree of unsaturation and source of oil
IV is directly proportional with…
degree of unsaturation
fats are lower
oils are higher
IV is indirectly proportional with…
melting point
description of WIJS method
- ICl + fat –> saturated
- KI + ICl excess –> I2
- I2 titrated with NaSO3
- blank titration
how to calculate IV
create a ratio between the grams of iodine needed for 1 molecule of fat (taking # double bonds into account)
catalyst activity is represented as
decrease in IV per time
relationship between agitation and hydrogenation
more agitation = faster hydrogenation
relationship between catalyst concentration and hydrogenation
more catalyst = faster hydrogenation
what is saponification
hydrolysis of ester under alkaline conditions
what is saponification value
mg of KOH needed to neutralize the FAs released from hydrolyzing 1g of lipid
saponification value equation
(56.1 * (B-S) * N)/g
saponification is directly proportional to
number of fatty acids
saponification value is indirectly proportional to
chain length
method for gas chromatography
- extract
- saponify
- prepare methyl ester
- chromatograph methyl esters
- determine peak areas of fatty acids (retention time)
- compare to the response curve of known fatty acids
G2SU means…
a. TG with 2 unsaturated fatty acids and one saturated fatty acid
b. TG with 2 short chained fatty acids and one unsaturated fatty acid
c. TG with 2 saturated fatty acids and 1 unsaturated fatty acid
c
True or false
Intraesterification is an exchange of FAs among TG molecules
F
the mass of iodine in grams absorbed by 100g of the sample is…
iodine value
the saponification value of a fat is inversely proportional to the…
chain length
The saponification value of a fat sample is
a. Directly proportional to the chain length of fatty acids in the sample
b. Inversely proportional to the chain length of fatty acids in the sample
c. Directly proportional to the number of double bonds in the sample
d. Inversely proportional to the number of double bonds in the sample
b
the rate of hydrogenation reaction is measured by the change of…
a. Saponification value per minute
b. Chain length per minute
c. IV per minute
c
why don’t fats have sharp melting points
complex mix of TGs with unique melting points. composite of these MPs
why do fats appear solid at room temperature
oil trapped in a crystalline matrix
what % of solids are neccessary to make the fat retain solid character
10%
what is plasticity
changes in consistency as a function of temperature
what property of fats allows them to have plasticity
made of a liquid in a crystalline matrix. thus, the 3D crystal network is held together by weak VDW interactions that constantly dissociate and reform
solid-to-liquid ratio is a function of
temperature
plasticity of a function of
solid to liquid ratio
what is the plastic range
the state a fat is in when it can be deformed readily
the plastic range is a function of (2 things)
fatty acid composition and distribution
difference between margarine and butter
margarine - wide plastic range. butter - small plastic range
what is polymorphism
TGs able to change from one crystal form into another
alpha form
thin,leaf-like crystals
melting fat the quickly cooling
random packing arrangement
unstable
beta prime form
remelting and slowly cooling
small and uniform crystals
desirable structure
beta form
remelting and cooling very slowly
dense, large crystals
large and grainy
analytical methods for studying polymorphism
x-ray diffraction analysis
microscopic analysis
IR spectroscopic analysis
thermal analysis
how to determine solid fat content
dilatometry
what is dilatometry
measurement of the change in specific volume per unit of temperature change
dilatometry process
measuring the fat expansion as a function of temperature in a reservoir
dilatometry curve is a combination of what 3 curves
- thermal expansion of solid fat
- expansion due to change in state
- thermal expansion of liquid only
these 3 are consecutive
solid fat index formula
x/y * 100 (x is at a certain temperature)
how to determine solid fat content
NMR - nuclear magnetic resonance
NMR process
- place fat in magnetic field
- radiofrequency (RF) pulse delivered perpendicular to field
- the H nuclei spins
- detect free induction decay (FID) - relaxiation process . since solids relax faster than liquids, comparing the FID time determines the SFC
what method is preferred? NMR or dilatometry
NMR
consitstency
apparent hardness at a specific temperature
beta prime in shortening
large amount of small air bubbles. smaller crystals whiter, creamier, more tender, smoother uniform and glossy better volume and texture of baked goods
beta in shortening
small amounts of large air bubbles
large clustered crystals
waxy/grainy
what crystals are present in natural lard? rearranged? how does the molecular arrangement change
natural - beta. more palmatic acid at postion 2
rearranged - beta prime
what kind of mixture is margarine
water-in-oil emulsion
what oils are present in margarine
soybean (beta) and hydrogenated cottonseed (beta prime)
blending these 2 oils into margarine is desirable because…
produces a high polyunsaturated and low/none trans containing product. good spreadability and high temp stability
what is tempering
process of transforming to the proper polymorphic form
what must processors be mindful of when tempering?
removing the heat of transformation so that melting and over-transforming dont occur
difference between hydrogenated palm kernel oil and randomized hydrogenated palm kernal oil. result of mixing
hydrogenated palm kernel oil - hard butter; melts at a higher temp; waxy mouthfeel
randomized hydrogenated palm kernal oil - melts at a lower temp
mixing creates a hard butter that melts in your mouth
cocoa butter
short melting range
mostly disaturated TGs
polymorphism state determines texture at temperatures
small beta crystals in cocoa butter
glossy texture. beta prime
large, clustered beta crystals
chocolate bloom. white spots and dull surface appearance
2 examples of oil-in-water emulsions
mayo and salad dressing
what properties do emulsions have in food products
more viscous
more opaque
fatty sensation masked
True or false: fat can provide the body with vitamin C
false
a crunchy chocolate is obtained when cocoa butter forms
a. Small alpha crystals
b. Small beta prime crystals
c. Small beta crystals
d. Large beta crystals
c
butter has a sharp fat content curve which means
a. It melts quickly
b. It releases flavors quickly
c. None
d. Both
d
The preferred crystal type in margarine is…
a. Alpha crystals because it gives better spreadability
b. Beta prime crystals because it give better spreadability and creamy mouthfeel
c. Beta crystals because they give a desirable degree of solidness
b
fats don’t have sharp melting points because
a. Consist of different TGs with different MPs
b. Have a 3D network of crystals delaying the melting of some fat crystals
c. None
d. Both
a
Interesterified TGs can be fractionated by controlling the …
temp
The change in consistency as a function of temperature is…
plasticity
True or false: Beta prime crystals are preferred for chocolate
false; beta
The technique that is based on the measurement of the change in specific volume per unit temperature is called…
dilatometry
When fat is cooled quickly it forms thin, leaf-like crystals. This forms…
alpha crystals
