Benyamin Asadipour-Farsani [EngD Conference abstract]

Figure 1 illustrates how the coolant temperature of the scraped surface heat exchanger affectsthe viscosities of fat systems. Three different behaviours are observed. The first is that ofsamples produced at low temperatures (i.e. 2°C and 5°C), which show shear thinningbehaviour and signs of structural deformation. The second is that of samples made at a hightemperature (i.e. 15°C). Such samples initially exhibit slightly shear-thickening behaviourfollowed by a significant decrease in the viscosity, indicating the shear-thinning nature ofsolid fat networks; and have a higher viscosity at the end of the viscometry experiment,compared to that at the start of the experiment. So the application of shear has altered themicrostructure of the systems in such a way that results in an increase in viscosity. The thirdviscosity profile observed is that of samples produced at 10°C, which show an intermediatebehaviour to that of the two viscosity profiles previously mentioned. A slight increase inviscosity is observed when comparing the values at the start and the end of the experiment,on the other hand the viscosity profile at higher shear rates is similar to that of samplesproduced at lower temperatures.Results obtained from these experiments provide an insight into the effect of processingconditions on the physical properties of fat crystal networks. This allows the design ofsystems with specific behaviour by manipulating the processing conditions.References(1) Effect of cooling rate on the structure and mechanical properties of milk fat and lard.Campos, R., Narine, S. S. and Marangoni, A. G. s.l. : Elsevier Science Ltd., 2002, FoodResearch International, Vol. 35, pp. 971-981.(2) SIKORSKI, Z. E. and SIKORSKA-WISNIEWSKA, G. The Role of Lipids in Food Quality. [bookauth.] C. WILLIAMS and J. BUTTRISS. Improving the Fat Content of Foods. s.l. : WoodheadPublishing, 2006.(3) Crystallization behaviour of fats and lipids - a review. Sato, Kiyotaka. s.l. : Elsevier ScienceLtd., 2001, Chemical Engineering Science, Vol. 56, pp. 2255-2265.