Structural and concomitant physical changes of Lipid Networks during tempering. Suresh Narine, AVAC Chair in Rheology, Agri-Food Materials Science Centre University of Alberta Frank Kincs,Neil Widlak, Oilseeds Research Archer Daniel Midland Centre of Excellence, Bunge Foods. - PowerPoint PPT Presentation
Suresh Narine, Suresh Narine, AVAC Chair in Rheology, AVAC Chair in Rheology, Agri-Food Materials Science Centre Agri-Food Materials Science Centre University of Alberta University of Alberta Frank Kincs, Frank Kincs, Neil Widlak, Neil Widlak, Oilseeds Research Oilseeds Research Archer Daniel Archer Daniel Midland Midland Centre of Excellence, Centre of Excellence, Bunge Foods Bunge Foods Structural and concomitan physical changes of Lipid Networks during tempering
Transcript
Suresh Narine, Suresh Narine, AVAC Chair in Rheology,AVAC Chair in Rheology,Agri-Food Materials Science CentreAgri-Food Materials Science CentreUniversity of AlbertaUniversity of Alberta
Frank Kincs,Frank Kincs, Neil Widlak, Neil Widlak, Oilseeds Research Oilseeds Research Archer Daniel Archer Daniel MidlandMidlandCentre of Excellence,Centre of Excellence,Bunge Foods Bunge Foods
Structural and concomitantphysical changes of Lipid Networks during tempering
ProblemProblem
Shortenings and margarines are usually Shortenings and margarines are usually incubated for periods of 48 hours or more, incubated for periods of 48 hours or more, in controlled temperature environments.in controlled temperature environments.
During this “temper” period, large changes During this “temper” period, large changes in the physical properties of the shortening in the physical properties of the shortening can be detected:can be detected:
It is costly and a logistic challenge to It is costly and a logistic challenge to incubate for such long periods.incubate for such long periods.
Accurate temperature control in large Accurate temperature control in large warehouses are difficult to maintain.warehouses are difficult to maintain.
Fluctuations in temperature conditions can Fluctuations in temperature conditions can often result in prolonging the required often result in prolonging the required temper period.temper period.
If improperly tempered, the product can If improperly tempered, the product can continue to demonstrate changes in physical continue to demonstrate changes in physical properties on the shelf.properties on the shelf.
ProblemProblem Very little is known about the structural changes Very little is known about the structural changes
that occur during tempering of shortenings.that occur during tempering of shortenings.
It is often NOT due only to a change in It is often NOT due only to a change in polymorphism, Solid Fat Content, or even polymorphism, Solid Fat Content, or even particle size distribution.particle size distribution.
Company-specific methods of processing (work Company-specific methods of processing (work times, hold times, etc.) contribute to the lack of times, hold times, etc.) contribute to the lack of understanding, as the changes occurring during understanding, as the changes occurring during the temper process may also differ depending the temper process may also differ depending on the process.on the process.
DeliverablesDeliverables Find optimum temperature for storageFind optimum temperature for storage
Find maximum time at that temperature required Find maximum time at that temperature required for storagefor storage
Find allowable margins for temperature fluctuationsFind allowable margins for temperature fluctuations
Identify structural changesIdentify structural changes– Find ways of halting such changes by use of additives Find ways of halting such changes by use of additives
such as emulsifierssuch as emulsifiers– Find ways of accelerating such changes in order to reduce Find ways of accelerating such changes in order to reduce
time required to temper.time required to temper.
Relate quantifiable structural changes to Relate quantifiable structural changes to quantifiable physical changesquantifiable physical changes
ExperimentExperiment
Samples of:Samples of:
20% fully hydrogenated lard in 80% Soybean Oil, and20% fully hydrogenated lard in 80% Soybean Oil, and 20% fully hydrogenated cottonseed in 80% Soybean 20% fully hydrogenated cottonseed in 80% Soybean
OilOil
Cooled at a processing rate of 10Cooled at a processing rate of 10oCoC/min, /min, from 67from 67ooC to 20C to 20ooCC
Continually mixed via shearing action for Continually mixed via shearing action for 6 minutes6 minutes
Samples were then:Samples were then: Poured into identical stainless steel cylindrical Poured into identical stainless steel cylindrical
containers, suitable for measuring hardness using an containers, suitable for measuring hardness using an Instron Texture AnalyzerInstron Texture Analyzer
Sampled onto glass slides pre-calibrated with a grid, Sampled onto glass slides pre-calibrated with a grid, allowing easy location of identical spots,allowing easy location of identical spots,
Sampled into DSC pansSampled into DSC pans Sampled into NMR tubesSampled into NMR tubes
Enough samples were prepared to allow a Enough samples were prepared to allow a set of samples stored each at 20set of samples stored each at 20ooC, 25C, 25ooC, C, and 30and 30ooC.C.
Samples were stored over a 104 hour Samples were stored over a 104 hour period, and tested every 8 hoursperiod, and tested every 8 hours
ExperimentExperiment
Lard
Hardness EvolutionHardness Evolution
0.001
0.002
0.003
0.004
0.005
0.006
-4 4 12 20 28 36 44 52 60 68 76 84 92 100
Time / h
Avera
ge H
ard
ness
Hardness Evolution of 20% Lard/Soybean at 20oC
Hardness EvolutionHardness Evolution
0.001
0.002
0.003
0.004
0.005
0.006
-4 4 12 20 28 36 44 52 60 68 76 84 92 100
Time / h
Avera
ge H
ard
ness
Hardness Evolution of 20% Lard/Soybean at 25oC
Hardness EvolutionHardness Evolution
0.001
0.002
0.003
0.004
0.005
0.006
-4 4 12 20 28 36 44 52 60 68 76 84 92 100
Hardness Evolution of 20% Lard/Soybean at 30oC
Time / h
Avera
ge H
ard
ness
Hardness EvolutionHardness Evolution
0
0.001
0.002
0.003
0.004
0.005
0.006
0.007
0 25 50 75 100
Lard 20
Lard 25
Lard 30
Avera
ge H
ard
ness
Time / h
Evolution of HardnessEvolution of Hardness
Hardness of all the samples increase Hardness of all the samples increase very slightly from 0h to 104 h.very slightly from 0h to 104 h.
3030ooC sample>25C sample>25ooC sample>20C sample>20ooC C samplesample
However, due to the extremely small However, due to the extremely small differences, these samples all differences, these samples all practically have the same hardness, practically have the same hardness, which remains constant over the 104 h.which remains constant over the 104 h.
Evolution of meltingEvolution of melting
46
47
48
49
50
51
52
53
54
55
56
0 8 16 24 32 40 48 56 64 72 80 88 96 104 112
Time ( Hours)
Me
ltin
g P
ea
k
Melting Peak Evolution of 20% Lard/Soybean at 20oC
Evolution of meltingEvolution of melting
46
47
48
49
50
51
52
53
54
55
56
0 8 16 24 32 40 48 56 64 72 80 88 96 104 112
Time (hours)
Me
ltin
g P
ea
k
Melting Peak Evolution of 20% Lard/Soybean at 25oC
Evolution of meltingEvolution of melting
46
4748
49
5051
52
53
5455
56
0 8 16 24 32 40 48 56 64 72 80 88 96 104 112
Time (hours)
Me
ltin
g p
ea
k
Melting Peak Evolution of 20% Lard/Soybean at 30oC
Evolution of meltingEvolution of melting
46
47
48
49
50
51
52
53
54
55
56
0 20 40 60 80 100 120
Time (Hours)
Mel
tin
g P
eak
Lard 20*C Lard 25*C Lard 30*C
Evolution of meltingEvolution of melting The peak maximum of the melting peak The peak maximum of the melting peak
measured by DSC does not change for any of measured by DSC does not change for any of the samples, over 104 hours.the samples, over 104 hours.
Furthermore, all the samples melt at the same Furthermore, all the samples melt at the same temperature.temperature.
Therefore, the same polymorph is formed in Therefore, the same polymorph is formed in each of the samples, and this does not change.each of the samples, and this does not change.
This is in agreement with the Hardness Data This is in agreement with the Hardness Data (essentially the same)(essentially the same)
Evolution of Solid Evolution of Solid ContentContent
12
13
14
15
16
17
18
19
20
0 20 40 60 80 100 120
20*C 25*C 30*C
Perc
en
t S
olid
Con
tent
Time / h
Evolution of Solid Evolution of Solid ContentContent There is a slight decrease in solid There is a slight decrease in solid
content demonstrated by all the content demonstrated by all the samples over 104 h.samples over 104 h.
SamplSample e TempTemp
SFC at 0 SFC at 0 hh
SFC at 104 SFC at 104 hh
DeviatioDeviationn
2020 1919 17.517.5 ReferencReferencee
2525 1919 17.017.0 0.50.5
3030 16.516.5 14.514.5 2.52.5
Evolution of Solid Evolution of Solid ContentContent The solid content data does NOT The solid content data does NOT
support the hardness datasupport the hardness data
The hardness of the sample stored at The hardness of the sample stored at 3030ooC is slightly higher than that at both C is slightly higher than that at both 2525ooC and 20C and 20ooC.C.
Yet, the solids at 30Yet, the solids at 30ooC are less than C are less than both 25both 25ooC as well as 20C as well as 20ooC!!!!C!!!!
30oC
25oC
20oC
1 hour of storage
The average particle sizes are the same.
There are not discernible changes betweenthe samples stored at different temperatures
30oC
25oC
20oC
104 hours of storage
The average particle sizes are the same.
There are not discernible changes betweenthe samples stored at different temperatures
25oC
Microstructure DataMicrostructure Data
There is no discernible difference There is no discernible difference in the microstructure of the in the microstructure of the samples stored at different samples stored at different temperatures.temperatures.
This supports the hardness data, This supports the hardness data, in so far as the microstructure in so far as the microstructure compared across samples does compared across samples does not vary at any particular time.not vary at any particular time.
30oC at 1 hour 30oC at 104 hour
There is less solid in the image at 104 h, but the solid portion in this imageis more defined, more particulate in nature than the solid in the image whichis at 1 hour. There is also apparently more sintering.
Identical Structure
Microstructure DataMicrostructure Data
The increase in sintering and The increase in sintering and definition of the microstructure definition of the microstructure explains why although the SFC explains why although the SFC decreases, the hardness is fairly decreases, the hardness is fairly constant.constant.
The sintering and definition as the The sintering and definition as the network recrystallizes and decreases network recrystallizes and decreases in SFC, compensates for the SFC in SFC, compensates for the SFC effect.effect.
Identical structure
25 oC at 1 hour 25oC at 104 hour
There is no difference in the amount of solid, but there are small changes in the structures which make them more defined.
20 oC at 1 hour 20oC at 104 hour
Identical Structure
There are no discernible change in the sintering or definition of the particles
Cottonseed
Profile of hardness increase in CTN-20% @ 30*C over 12 days
0.00000
0.00200
0.00400
0.00600
0.00800
0.01000
0.01200
0.01400
0.01600
0.01800
0 32 64 96 128 160 192 224 256 288 320
Time in hours
Ave
rag
e sl
op
e
1400%
Hardness BehaviorHardness Behavior
Hardness BehaviorHardness Behavior
Hardness Increase in 20% Hard Cottonseed/Soy Oil tempered at 25*C
0.00000
0.00005
0.00010
0.00015
0.00020
0 8 16 24 32 40 48 56 64 72
Time (hours)
Ave
rag
e H
ard
nes
s
183%
Hardness BehaviorHardness Behavior
Hardness Increase in 20% Hard Cottonseed/Soy Oil tempered at 20*C
0.00000
0.00002
0.00004
0.00006
0.00008
0.00010
0.00012
0.00014
0 8 16 24 32 40 48 56 64 72
Time (hours)
Ave
rag
e H
ard
nes
s
No Measurable Increase
Relative Hardness at Relative Hardness at 64 Hours of temper64 Hours of temper
Storage Storage Temperature Temperature (*C)(*C)
Qualitative Qualitative HardnessHardness
Percentage Percentage Differences Differences in Hardnessin Hardness
Evolution of Solid Evolution of Solid ContentContent
Evolution of Solid Content
14
15
16
17
18
19
20
70 75 80 85 90 95 100 105 110
Time (H)
%S
FC
20*c 25*C 30*C
Microstructure of the sample stored at 20*C
Identical Structures
8 hours after sample formed
40 hours after sample formed
60 hours after sample formed
No appreciable changes canbe detected.
8 hours after sample formed
40 hours after sample formed
No appreciable changes canbe detected.
60 hours after sample formed
Microstructure of the sample stored at 25*C
8 hours after sample formedSintering between structural entities notWell defined.
40 hours after sample formed,Sintering between structuralEntities are much more defined.
No appreciable increase in the sizeof the structural entities can be discerned.
Same structure
60 hours after sampleformed, sintering ismore pronounced
8 hours after sample formedSintering between structural entities notWell defined.
40 hours after sample formed,Sintering between structuralEntities are much more defined.
No appreciable increase in the sizeof the structural entities can be discerned.
60 hours after sampleformed.Sintering is more pronounced
Microstructure of the sample stored at 30*C
Same structure
8 hours after sample formed
60 hours after sampleformed
85 hours after sampleformed
No discernible changein structure
8 hours after sample formed
60 hours after sampleformed
85 hours after sampleformed
No discernible changein structure
ConclusionsConclusions
At 20*C:At 20*C:
No change in polymorphismNo change in polymorphism No change in solid fat contentNo change in solid fat content No change in MicrostructureNo change in Microstructure
Also, no change in hardness.Also, no change in hardness.
ConclusionsConclusions
At 25*C:At 25*C:
No change in polymorphism.No change in polymorphism. No change in solid content.No change in solid content. Changes in Microstructure from sample tempered for Changes in Microstructure from sample tempered for
8 hours to sample tempered for 40 hours – more 8 hours to sample tempered for 40 hours – more sintering.sintering.
Even more sintering can be observed in sample at 60 Even more sintering can be observed in sample at 60 hours.hours.
No change in hardness until 32 hours, then No change in hardness until 32 hours, then a steep increase until 60 hours, and then a steep increase until 60 hours, and then hardness plateaushardness plateaus
ConclusionsConclusions
At 30*C:At 30*C:
Large change in polymorphismLarge change in polymorphism Most of sample changed to more stable, higher melting Most of sample changed to more stable, higher melting
polymorphpolymorph A small amount of sample changed to a less stable, A small amount of sample changed to a less stable,
lower melting polymorph, which almost disappears by lower melting polymorph, which almost disappears by 104 hours104 hours
Steady decrease in solid fat content until approximately Steady decrease in solid fat content until approximately 70 hours.70 hours.
No discernible change in microstructure.No discernible change in microstructure.
Large, steady increase in hardness over 104 Large, steady increase in hardness over 104 hours, then hardness plateaushours, then hardness plateaus
ConclusionsConclusions
Obviously, the temperature at which Obviously, the temperature at which the sample is stored has a large effect the sample is stored has a large effect on the final properties of the sample.on the final properties of the sample.
As little as 5*C differences can cause As little as 5*C differences can cause such large effects.such large effects.
There seems to be some correlation There seems to be some correlation between structural changes and between structural changes and changes in physical properties.changes in physical properties.
ConclusionsConclusions
At 20*C, there are no detectable At 20*C, there are no detectable changes in structural parameters of the changes in structural parameters of the network.network.
At 25*C, the structural changes are in At 25*C, the structural changes are in microstructure only.microstructure only.
At 30*C, the structural changes are At 30*C, the structural changes are polymorphic in nature.polymorphic in nature.
ConclusionsConclusions Polymorphism – possible explanations?Polymorphism – possible explanations?
At 20*C, there is not enough liquid in the sample to allow for a At 20*C, there is not enough liquid in the sample to allow for a melt-mediated polymorphic transformation, or for significant melt-mediated polymorphic transformation, or for significant dissolution behavior, perhaps?dissolution behavior, perhaps?
At 25*C, the situation is the same as at 20*CAt 25*C, the situation is the same as at 20*C
At 30*C, there is an appreciably greater percentage of liquid, At 30*C, there is an appreciably greater percentage of liquid, therefore promoting the polymorphic transformation.therefore promoting the polymorphic transformation.
Quite frankly, I am confused about this result, as the difference Quite frankly, I am confused about this result, as the difference in SFC’s is only about 3%in SFC’s is only about 3%
However, the argument of greater molecular mobility at the However, the argument of greater molecular mobility at the higher temperature may be relevanthigher temperature may be relevant
ConclusionsConclusions
MicrostructureMicrostructure
At 20*C, the sample is probably viscosity-constrained At 20*C, the sample is probably viscosity-constrained for changes in microstructure, although this must be for changes in microstructure, although this must be proven.proven.
At 25*C, the sample is certainly less viscosity-At 25*C, the sample is certainly less viscosity-constrained, and may lead to sintering, although it constrained, and may lead to sintering, although it must be kept in mind that the SFC of the samples at must be kept in mind that the SFC of the samples at 20 and 25*C are the same.20 and 25*C are the same.
At 30*C, for some reason, there is no re-arrangement At 30*C, for some reason, there is no re-arrangement of the microstructure, which is yet to be explained.of the microstructure, which is yet to be explained.
ConclusionsConclusions
Clearly, any attempt to speed up the Clearly, any attempt to speed up the temper process, or to constrain the temper process, or to constrain the changes over time, must be educated by:changes over time, must be educated by:
The kind of structural change causing final physical The kind of structural change causing final physical functionality changes.functionality changes.
The kinetics of the changes.The kinetics of the changes.
The degree to which the structural change must be The degree to which the structural change must be constrained in order to affect physical functionality.constrained in order to affect physical functionality.
Questions:Questions:
Lard samples demonstrated little Lard samples demonstrated little differences in structure at the various differences in structure at the various levels, and small changes in hardness.levels, and small changes in hardness.
How is this related to the molecular How is this related to the molecular level?level?
That is, why are the changes seen in That is, why are the changes seen in Cottonseed samples and NOT in the lard Cottonseed samples and NOT in the lard samples?samples?
Questions:Questions:
TAGTAG Hard Hard CottonseeCottonseedd
HardHard
LardLard
PPPPPP 14.614.6 13.313.3
PPSPPS 36.936.9 37.637.6
SPS SPS 25.025.0 3737
SSSSSS 23.423.4 12.112.1
AcknowledgementsAcknowledgements
Baljit S. Ghotra, Ph.D. Student,Baljit S. Ghotra, Ph.D. Student, Sarah S. McCalla, Summer StudentSarah S. McCalla, Summer Student Sandra D. Dyal, MSc. StudentSandra D. Dyal, MSc. Student Kerry L. Humphrey, Ph.D. StudentKerry L. Humphrey, Ph.D. Student Archer Daniel MidlandArcher Daniel Midland Bunge FoodsBunge Foods National OilwellsNational Oilwells NSERCNSERC AVACAVAC AARIAARI
