Effect of Gelatin Gelation Kinetics on Probe Diffusion Determined by FRAP and Rheology

Abstract

The time-dependent diffusion and mechanical properties of gelatin in solution, in the gel state, and during the sol/gel transition were determined using fluorescence recovery after photobleaching (FRAP) and rheology. The parameters in the experimental design were 2% w/w and 5% w/w gelatin concentration; 15, 20, and 25 °C end quench temperatures; and Na(2)-fluorescein, 10 kDa FITC-dextran, and 500 kDa FITC-dextran as diffusion probes. The samples were monitored in solution at 60 °C, during quenching, for 75 min at end quench temperatures and after 1, 7, and 14 days of storage at the end quench temperature. The effect of temperature on the probe diffusion was normalized by determining the free diffusion of the probes in pure water for the different temperatures. The results gained by comparing FRAP and rheology showed that FRAP is able to capture structural changes in the gelatin before gelation occurs, which was interpreted as a formation of transient networks. This was clearly seen for 2% w/w gelatin and 20 and 25 °C end quench temperatures. The structural changes during sol/gel transition are detected only by the larger probes, giving information about the typical length scales in the gelatin structure. The normalized diffusion rate increased after 7 and 14 days of storage. This increase was most pronounced for fluorescein but was also seen for the larger probes.

Contrasting relationship between macro- and microviscosity of the gelatin- and starch-based suspensions and gels

“…diffusion of small molecules is slowed marginally. This finding is in good agreement with that of another investigation showing that small probe (like fluorescein) is unable to detect the gelatin transition from solution to gel [30]. Media with starch reveal opposite feature: they are fluid enough and their macroviscosity exceeds that of water by not more than three times.…”

Synthesis of spherical hydroxyapatite granules with interconnected pore channels using camphene emulsion

“…Gelatin has been reported to be easy to handle and to have good biocompatibility and plasticity 21. It is sensitive to temperature and concentration such that lower temperatures and higher concentrations lead to faster gel formation and stronger gels 22. If the concentration of gelatin is too high, reduced flow makes it difficult to produce a spherical form 22.…”

“…21 It is sensitive to temperature and concentration such that lower temperatures and higher concentrations lead to faster gel formation and stronger gels. 22 If the concentration of gelatin is too high, reduced flow makes it difficult to produce a spherical form. 22 If the concentration of gelatin is too low, problems arise such as lack of hardness and low bond strength between HA powder.…”

Oil diffusivity through fat crystal networks

“…Assuming that the dye and oil move in tandem, the rate of intensity recovery is the same as the rate of molecular diffusion. 20,24 In this study, we used FRAP to calculate the local diffusion coefficients of a hard fat mixed with vegetable or mineral oil as a function of solid fat content (SFC), SFC being simple to determine experimentally. [16][17][18] It has been used sparingly in food systems, namely in starch solutions, 19 model cheeses, 20,21 fat crystal networks, 6 and model chocolates.…”