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Suresh Narine, AVAC Chair in Rheology, Agri-Food Materials Science Centre University of Alberta

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.

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Suresh Narine, AVAC Chair in Rheology, Agri-Food Materials Science Centre University of Alberta

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  1. 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

  2. Problem • 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: • Hardness • Adhesion • Density • Spreadability • Melting

  3. Problem • It is costly and a logistic challenge to incubate for such long periods. • Accurate temperature control in large warehouses are difficult to maintain. • 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.

  4. Problem • 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. • 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.

  5. Challenge • 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

  6. Deliverables • Find optimum temperature for storage • Find maximum time at that temperature required for storage • Find allowable margins for temperature fluctuations • 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

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

  8. Experiment • Samples were then: • 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 into DSC pans • Sampled into NMR tubes • Enough samples were prepared to allow a set of samples stored each at 20oC, 25oC, and 30oC. • Samples were stored over a 104 hour period, and tested every 8 hours

  9. Lard

  10. Hardness Evolution Hardness Evolution of 20% Lard/Soybean at 20oC Average Hardness Time / h

  11. Hardness Evolution Hardness Evolution of 20% Lard/Soybean at 25oC Average Hardness Time / h

  12. Hardness Evolution Hardness Evolution of 20% Lard/Soybean at 30oC Average Hardness Time / h

  13. Hardness Evolution Average Hardness Time / h

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

  15. Evolution of melting Melting Peak Evolution of 20% Lard/Soybean at 20oC

  16. Evolution of melting Melting Peak Evolution of 20% Lard/Soybean at 25oC

  17. Evolution of melting Melting Peak Evolution of 20% Lard/Soybean at 30oC

  18. Evolution of melting

  19. Evolution of melting • 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. • 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)

  20. Evolution of Solid Content Percent Solid Content Time / h

  21. Evolution of Solid Content • There is a slight decrease in solid content demonstrated by all the samples over 104 h.

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

  23. 1 hour of storage 25oC 30oC 20oC The average particle sizes are the same. There are not discernible changes between the samples stored at different temperatures

  24. 104 hours of storage 25oC 25oC 20oC 30oC The average particle sizes are the same. There are not discernible changes between the samples stored at different temperatures

  25. Microstructure Data • 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.

  26. 30oC at 104 hour 30oC at 1 hour Identical Structure 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.

  27. Microstructure Data • 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.

  28. 25oC at 104 hour 25 oC at 1 hour Identical structure There is no difference in the amount of solid, but there are small changes in the structures which make them more defined.

  29. 20 oC at 1 hour 20oC at 104 hour Identical Structure There are no discernible change in the sintering or definition of the particles

  30. Cottonseed

  31. Hardness Behavior 1400%

  32. Hardness Behavior 183%

  33. Hardness Behavior No Measurable Increase

  34. Relative Hardness at 64 Hours of temper

  35. Melting Behavior (Polymorphism)

  36. Melting Behavior (Polymorphism)

  37. Melting Behavior (Polymorphism)

  38. Evolution of Solid Content

  39. Evolution of Solid Content

  40. Microstructure of the sample stored at 20*C

  41. 8 hours after sample formed Identical Structures 40 hours after sample formed 60 hours after sample formed No appreciable changes can be detected.

  42. 8 hours after sample formed 40 hours after sample formed 60 hours after sample formed No appreciable changes can be detected.

  43. Microstructure of the sample stored at 25*C

  44. 8 hours after sample formed Sintering between structural entities not Well defined. Same structure 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

  45. 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

  46. Microstructure of the sample stored at 30*C

  47. 8 hours after sample formed 60 hours after sample formed Same structure No discernible change in structure 85 hours after sample formed

  48. 8 hours after sample formed 60 hours after sample formed No discernible change in structure 85 hours after sample formed

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

  50. Conclusions • At 25*C: • No change in polymorphism. • No change in solid content. • 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. • No change in hardness until 32 hours, then a steep increase until 60 hours, and then hardness plateaus

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