Abstract
Samples of anhydrous milk fat and rapeseed oil were characterized by small amplitude oscillatory shear rheology using nine different instrumental geometrical combinations to monitor elastic modulus (G′) and relative deformation (strain) at fracture. First, G′ was continuously recorded during crystallization in a fluted cup at 5C. Second, crystallization of the blends occurred for 24h, at 5C, in external containers. Samples were gently cut into disks or filled in the rheometer prior to analysis. Among the geometries tested, corrugated parallel plates with top and bottom temperature control are most suitable due to reproducibility and dependence on shear and strain. Similar levels for G′ were obtained for samples measured with parallel plate setup and identical samples crystallized in situ in the geometry. Samples measured with other geometries have G′ orders of magnitude lower than identical samples crystallized in situ. This emphasizes the importance of gentle sample pre handling, temperature control and preventing slip. Practical Applications: Small deformation rheology is widely used to study and evaluate textural behavior of fat-based systems. As different research groups use different geometries, a systematic evaluation of data gained using different geometrical combinations is needed. By conducting a methodic evaluation, this work provides an increased knowledge of how to characterize fat-based systems using small deformation rheology and evaluates the relations between geometries. Because of the rigid nature of fat-based systems, wall slip is likely to occur. Moreover, when characterizing such systems during storage and/or produced at industrial scale, in situ crystallization is not possible. In such cases, the sample must be loaded at the geometry prior to analysis. Such loading will affect the fat crystal network to some extent and consequently the data obtained. However, as the physical conditions differ between the geometries available, they affect both the fat crystal network and the tendency of wall slip to occur differently.
| Translated title of the contribution | Små deformations reologi til karakterisation af vandfrit mælkefedt/rapsolie prøver |
|---|---|
| Original language | English |
| Journal | Journal of Texture Studies |
| Volume | 45 |
| Issue number | 1 |
| Pages (from-to) | 20-29 |
| Number of pages | 10 |
| ISSN | 0022-4901 |
| DOIs | |
| Publication status | Published - Feb 2014 |
Keywords
- Former LIFE faculty
- Fatty acids
- Dairy products
- Taste, smell and texture in food
- Faculty of Science