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 Structural and concomitant physical changes of Lipid Networks during tempering

Problem Shortenings and margarines are usually incubated for periods of 48 hours or more, in controlled temperature environments. Shortenings and margarines are usually incubated for periods of 48 hours or more, in controlled temperature environments. During this “temper” period, large changes in the physical properties of the shortening can be detected: During this “temper” period, large changes in the physical properties of the shortening can be detected: Hardness Hardness Adhesion Adhesion Density Density Spreadability Spreadability Melting Melting

Problem It is costly and a logistic challenge to incubate for such long periods. It is costly and a logistic challenge to incubate for such long periods. Accurate temperature control in large warehouses are difficult to maintain. Accurate temperature control in large warehouses are difficult to maintain. Fluctuations in temperature conditions can often result in prolonging the required temper period. Fluctuations in temperature conditions can often result in prolonging the required temper period. If improperly tempered, the product can continue to demonstrate changes in physical properties on the shelf. If improperly tempered, the product can continue to demonstrate changes in physical properties on the shelf.

Problem Very little is known about the structural changes that occur during tempering of shortenings. Very little is known about the structural changes that occur during tempering of shortenings. It is often NOT due only to a change in polymorphism, Solid Fat Content, or even particle size distribution. It is often NOT due only to a change in polymorphism, Solid Fat Content, or even particle size distribution. Company-specific methods of processing (work times, hold times, etc.) contribute to the lack of understanding, as the changes occurring during the temper process may also differ depending on the process. Company-specific methods of processing (work times, hold times, etc.) contribute to the lack of understanding, as the changes occurring during the temper process may also differ depending on the process.

Challenge Investigate relationships between: Investigate relationships between: –Formulation (type of fat, presence of emulsifiers) –Storage Temperature –Storage Time And: –Structural Changes –Resultant Physical Changes Nucleation Crystallization Ripening/Sintering Global thermodynamic Minima

Deliverables Find optimum temperature for storage Find optimum temperature for storage Find maximum time at that temperature required for storage Find maximum time at that temperature required for storage Find allowable margins for temperature fluctuations Find allowable margins for temperature fluctuations Identify structural changes Identify structural changes –Find ways of halting such changes by use of additives such as emulsifiers –Find ways of accelerating such changes in order to reduce time required to temper. Relate quantifiable structural changes to quantifiable physical changes Relate quantifiable structural changes to quantifiable physical changes

Experiment Samples of: Samples of: 20% fully hydrogenated lard in 80% Soybean Oil, and 20% fully hydrogenated lard in 80% Soybean Oil, and 20% fully hydrogenated cottonseed in 80% Soybean Oil 20% fully hydrogenated cottonseed in 80% Soybean Oil Cooled at a processing rate of 10 oC /min, from 67 o C to 20 o C Cooled at a processing rate of 10 oC /min, from 67 o C to 20 o C Continually mixed via shearing action for 6 minutes Continually mixed via shearing action for 6 minutes

Samples were then: Samples were then: Poured into identical stainless steel cylindrical containers, suitable for measuring hardness using an Instron Texture Analyzer Poured into identical stainless steel cylindrical containers, suitable for measuring hardness using an Instron Texture Analyzer Sampled onto glass slides pre-calibrated with a grid, allowing easy location of identical spots, Sampled onto glass slides pre-calibrated with a grid, allowing easy location of identical spots, Sampled into DSC pans Sampled into DSC pans Sampled into NMR tubes Sampled into NMR tubes Enough samples were prepared to allow a set of samples stored each at 20 o C, 25 o C, and 30 o C. Enough samples were prepared to allow a set of samples stored each at 20 o C, 25 o C, and 30 o C. Samples were stored over a 104 hour period, and tested every 8 hours Samples were stored over a 104 hour period, and tested every 8 hours Experiment

Lard

Hardness Evolution Time / h Average Hardness Hardness Evolution of 20% Lard/Soybean at 20 o C

Hardness Evolution Time / h Average Hardness Hardness Evolution of 20% Lard/Soybean at 25 o C

Hardness Evolution Hardness Evolution of 20% Lard/Soybean at 30 o C Time / h Average Hardness

Hardness Evolution Average Hardness Time / h

Evolution of Hardness Hardness of all the samples increase very slightly from 0h to 104 h. Hardness of all the samples increase very slightly from 0h to 104 h. 30 o C sample>25 o C sample>20 o C sample 30 o C sample>25 o C sample>20 o C sample However, due to the extremely small differences, these samples all practically have the same hardness, which remains constant over the 104 h. However, due to the extremely small differences, these samples all practically have the same hardness, which remains constant over the 104 h.

Evolution of melting Melting Peak Evolution of 20% Lard/Soybean at 20 o C

Evolution of melting Melting Peak Evolution of 20% Lard/Soybean at 25 o C

Evolution of melting Melting Peak Evolution of 20% Lard/Soybean at 30 o C

Evolution of melting

The peak maximum of the melting peak measured by DSC does not change for any of the samples, over 104 hours. The peak maximum of the melting peak measured by DSC does not change for any of the samples, over 104 hours. Furthermore, all the samples melt at the same temperature. Furthermore, all the samples melt at the same temperature. Therefore, the same polymorph is formed in each of the samples, and this does not change. Therefore, the same polymorph is formed in each of the samples, and this does not change. This is in agreement with the Hardness Data (essentially the same) This is in agreement with the Hardness Data (essentially the same)

Evolution of Solid Content Percent Solid Content Time / h

Evolution of Solid Content There is a slight decrease in solid content demonstrated by all the samples over 104 h. There is a slight decrease in solid content demonstrated by all the samples over 104 h. Sample Temp SFC at 0 h SFC at 104 h Deviation Reference

Evolution of Solid Content The solid content data does NOT support the hardness data The solid content data does NOT support the hardness data The hardness of the sample stored at 30 o C is slightly higher than that at both 25 o C and 20 o C. The hardness of the sample stored at 30 o C is slightly higher than that at both 25 o C and 20 o C. Yet, the solids at 30 o C are less than both 25 o C as well as 20 o C!!!! Yet, the solids at 30 o C are less than both 25 o C as well as 20 o C!!!!

30 o C 25 o C 20 o C 1 hour of storage The average particle sizes are the same. There are not discernible changes between the samples stored at different temperatures

30 o C 25 o C 20 o C 104 hours of storage The average particle sizes are the same. There are not discernible changes between the samples stored at different temperatures 25 o C

Microstructure Data There is no discernible difference in the microstructure of the samples stored at different temperatures. There is no discernible difference in the microstructure of the samples stored at different temperatures. This supports the hardness data, in so far as the microstructure compared across samples does not vary at any particular time. This supports the hardness data, in so far as the microstructure compared across samples does not vary at any particular time.

30 o C at 1 hour 30 o C at 104 hour There is less solid in the image at 104 h, but the solid portion in this image is more defined, more particulate in nature than the solid in the image which is at 1 hour. There is also apparently more sintering. Identical Structure

Microstructure Data The increase in sintering and definition of the microstructure explains why although the SFC decreases, the hardness is fairly constant. The increase in sintering and definition of the microstructure explains why although the SFC decreases, the hardness is fairly constant. The sintering and definition as the network recrystallizes and decreases in SFC, compensates for the SFC effect. The sintering and definition as the network recrystallizes and decreases in SFC, compensates for the SFC effect.

Identical structure 25 o C at 1 hour 25 o C 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 o C at 1 hour20 o C at 104 hour Identical Structure There are no discernible change in the sintering or definition of the particles

Cottonseed

1400% Hardness Behavior

183%

Hardness Behavior No Measurable Increase

Relative Hardness at 64 Hours of temper Storage Temperature (*C) Qualitative Hardness Percentage Differences in Hardness 20SoftReference 25Hard143% 30 Very Hard 9757%

Melting Behavior (Polymorphism)

Evolution of Solid Content

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 can be detected.

8 hours after sample formed 40 hours after sample formed No appreciable changes can be detected. 60 hours after sample formed

Microstructure of the sample stored at 25*C

8 hours after sample formed Sintering between structural entities not Well defined. 40 hours after sample formed, Sintering between structural Entities are much more defined. No appreciable increase in the size of the structural entities can be discerned. Same structure 60 hours after sample formed, sintering is more pronounced

8 hours after sample formed Sintering between structural entities not Well defined. 40 hours after sample formed, Sintering between structural Entities are much more defined. No appreciable increase in the size of the structural entities can be discerned. 60 hours after sample formed. Sintering is more pronounced

Microstructure of the sample stored at 30*C

Same structure 8 hours after sample formed 60 hours after sample formed 85 hours after sample formed No discernible change in structure

8 hours after sample formed 60 hours after sample formed 85 hours after sample formed No discernible change in structure

Conclusions At 20*C: At 20*C: No change in polymorphism No change in polymorphism No change in solid fat content No change in solid fat content No change in Microstructure No change in Microstructure Also, no change in hardness. Also, no change in hardness.

Conclusions 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 8 hours to sample tempered for 40 hours – more sintering. Changes in Microstructure from sample tempered for 8 hours to sample tempered for 40 hours – more sintering. Even more sintering can be observed in sample at 60 hours. Even more sintering can be observed in sample at 60 hours. No change in hardness until 32 hours, then a steep increase until 60 hours, and then hardness plateaus No change in hardness until 32 hours, then a steep increase until 60 hours, and then hardness plateaus

Conclusions At 30*C: At 30*C: Large change in polymorphism Large change in polymorphism Most of sample changed to more stable, higher melting polymorph Most of sample changed to more stable, higher melting polymorph A small amount of sample changed to a less stable, lower melting polymorph, which almost disappears by 104 hours A small amount of sample changed to a less stable, lower melting polymorph, which almost disappears by 104 hours Steady decrease in solid fat content until approximately 70 hours. Steady decrease in solid fat content until approximately 70 hours. No discernible change in microstructure. No discernible change in microstructure. Large, steady increase in hardness over 104 hours, then hardness plateaus Large, steady increase in hardness over 104 hours, then hardness plateaus

Conclusions Obviously, the temperature at which the sample is stored has a large effect on the final properties of the sample. Obviously, the temperature at which the sample is stored has a large effect on the final properties of the sample. As little as 5*C differences can cause such large effects. As little as 5*C differences can cause such large effects. There seems to be some correlation between structural changes and changes in physical properties. There seems to be some correlation between structural changes and changes in physical properties.

Conclusions At 20*C, there are no detectable changes in structural parameters of the network. At 20*C, there are no detectable changes in structural parameters of the network. At 25*C, the structural changes are in microstructure only. At 25*C, the structural changes are in microstructure only. At 30*C, the structural changes are polymorphic in nature. At 30*C, the structural changes are polymorphic in nature.

Conclusions Polymorphism – possible explanations? Polymorphism – possible explanations? At 20*C, there is not enough liquid in the sample to allow for a melt-mediated polymorphic transformation, or for significant dissolution behavior, perhaps? At 20*C, there is not enough liquid in the sample to allow for a melt-mediated polymorphic transformation, or for significant dissolution behavior, perhaps? At 25*C, the situation is the same as at 20*C At 25*C, the situation is the same as at 20*C At 30*C, there is an appreciably greater percentage of liquid, therefore promoting the polymorphic transformation. At 30*C, there is an appreciably greater percentage of liquid, therefore promoting the polymorphic transformation. Quite frankly, I am confused about this result, as the difference in SFC’s is only about 3% Quite frankly, I am confused about this result, as the difference in SFC’s is only about 3% However, the argument of greater molecular mobility at the higher temperature may be relevant However, the argument of greater molecular mobility at the higher temperature may be relevant

Conclusions Microstructure Microstructure At 20*C, the sample is probably viscosity-constrained for changes in microstructure, although this must be proven. At 20*C, the sample is probably viscosity-constrained for changes in microstructure, although this must be proven. At 25*C, the sample is certainly less viscosity- constrained, and may lead to sintering, although it must be kept in mind that the SFC of the samples at 20 and 25*C are the same. At 25*C, the sample is certainly less viscosity- constrained, and may lead to sintering, although it must be kept in mind that the SFC of the samples at 20 and 25*C are the same. At 30*C, for some reason, there is no re-arrangement of the microstructure, which is yet to be explained. At 30*C, for some reason, there is no re-arrangement of the microstructure, which is yet to be explained.

Conclusions Clearly, any attempt to speed up the temper process, or to constrain the changes over time, must be educated by: Clearly, any attempt to speed up the temper process, or to constrain the changes over time, must be educated by: The kind of structural change causing final physical functionality changes. The kind of structural change causing final physical functionality changes. The kinetics of the changes. The kinetics of the changes. The degree to which the structural change must be constrained in order to affect physical functionality. The degree to which the structural change must be constrained in order to affect physical functionality.

Questions: Lard samples demonstrated little differences in structure at the various levels, and small changes in hardness. Lard samples demonstrated little differences in structure at the various levels, and small changes in hardness. How is this related to the molecular level? How is this related to the molecular level? That is, why are the changes seen in Cottonseed samples and NOT in the lard samples? That is, why are the changes seen in Cottonseed samples and NOT in the lard samples?

Questions:TAG Hard Cottonseed HardLard PPP PPS SPS SSS

Acknowledgements Baljit S. Ghotra, Ph.D. Student, Baljit S. Ghotra, Ph.D. Student, Sarah S. McCalla, Summer Student Sarah S. McCalla, Summer Student Sandra D. Dyal, MSc. Student Sandra D. Dyal, MSc. Student Kerry L. Humphrey, Ph.D. Student Kerry L. Humphrey, Ph.D. Student Archer Daniel Midland Archer Daniel Midland Bunge Foods Bunge Foods National Oilwells National Oilwells NSERC NSERC AVAC AVAC AARI AARI