A gel of alginate gives very satisfactory results, but it has to be noted that the use of some
sodium alginate requires the presence of calcium to set in gel.
III.11.4. Thermal equilibrium.
III.11.4.1. Materials and method:
With the same gels than in III.11.3.2., measure the temperature with a thermocouple (MAFTER k
beach 50 - 950 °C; uncertainty 1°C).
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evolution de la temperature des gels chauds et froid
0 2 4 6 8 10 12 14 16 18 20
temps en minute
Temperature en °C
Figure 28 of the evolution of the temperature of the gels
Series 1: Evolution of the temperature of a cold gel from the fridge.
Series 2: Evolution of the temperature of a warm gel from the microwave.
Series 3: Evolution of the temperature warm gel in contact with the cold gel.
Series 4: Evolution of the temperature cold gel in contact with the warm gel.
The data of this graph are in the appendix 12.
III.11.4.3. Discussion/Interpretation :
The gels cools quite slowly and the difference of temperature between a hot and a cold gel in
contact is still perceivable after 20 min (there is still a difference of 20°C).
The temperature was taken near the edge of the glass. But right in the middle of the gel, the
temperature were obviously bigger. It seems that the thermal exchange between the middle of the gel
and its borders is bigger than the thermal exchange between the two gels at different temperatures.
This experiment is easy to do, it does not require a particular technique. The gels of alginates are
restricted to the use of solutions containing some calcium ions, as dairy products. However, the other
gelling agents can be employed to obtain similar effects.
Also, Pierre Gagnaire wished very smooth gels, which behave more like a thick liquid than a
solid gel. Here, we could have used a thickening instead of a strong gel. For example, the use of starch
can lead to good results, without any new ingredients or techniques. This technology is thus easy to set