Diffusion is vital for many food properties such as oral taste release and water management in pasta and pastry products. These examples show that it is important to have good control over the diffusion properties to obtain desired functionality. Therefore thorough understanding of structure - mass transport relationships and good measurement techniques are essential. In this talk, the coupling between structure and diffusion in soft porous heterogeneous materials will be exemplified and discussed.
Confocal laser scanning microscopy (CLSM) in combination with Flourescence recovery after photobleaching (FRAP) is a versatile method to determine quantitative diffusion properties locally directly in the microscope. It can be used in many types of soft porous homogeneous and heterogeneous biomaterials. In FRAP, fluorescently labelled molecules are bleached locally and rate of intensity recovery is proportional to local diffusion rate. Here, new advanced pixel-based FRAP models1that opens up possibilities to estimate diffusion coefficients with good precision and error estimates will be presented.
Food properties changes as a function of time and surrounding conditions. CLSM-FRAP combined with stages to control surrounding conditions is powerful to monitor effects of kinetics on the diffusion properties. Here, possibilities of CLSM-FRAP and new pixel-based models to quantitatively monitor diffusion during fat crystallisation in chocolate2, and gelatine gelation3will be shown. It was found that tempering and solid particle additions have a large impact on the time-dependent fat migration in chocolate model systems2. CLSM-FRAP combined with rheology shown strong indication of formation of transient structures during gelation of gelatine gels3. Recent advances in cell science that allow for determination of interaction parameters using FRAP has been applied to biopolymer gels. Results that reveal the effects of charge density, size and concentration on diffusion of negative probes in positively charged b-lactoglobulin gels will be presented4.
1Deschout et al. (2010) Optics Express, 18, 22886-22905.
2Svanberg et al. (2011) Food Research International, 44, 1339-1350.
3Hagman et al. (2010) Biomacromolecules, 11, 3359-3366.
4Schuster et al. (2013) Submitted.
Principal investigator: Assoc. Prof. Niklas Lorén niklas.loren@sik.se
