· Spoon for sherbet or Parisian spoon, diameter 1 cm ± 0.1cm.
· Dishes: pan, tubs.
· Tap water: we made the hypothesis (to verify) that we shall obtain a good result with tap water,
because there are no strong interactions between gelatine and the ions contained in the tap water.
· Gelatine or Agar-agar, supplier Louis Francois.
· Deep freeze Koma (system 80/20); beach 40 in +40°C; constant T°C-30°C
· Cold room Dagar brand with constant temperature at 2°C; precision 2°C
1. Put some water (beforehand frozen) in the ice-cream maker to obtain a "sherbet".
2. Form balls with the Parisian spoon.
3. Put them in the deep freeze so that the temperature of balls is kept between -15 and -25°C.
4. Make a solution of gelatine at 1,2 % in weight with sheets of gelatine previously dipped into some
water at room temperature.
5. With a chocolate fork (two teeth), plunge the balls of sherbet into the solution of gelatine, and remove
them after less than 5 s. The sherbet quickly cools the solution of gelatine in contact and thus, the
gelatine sets in gel, making a film around the ball of sherbet.
6. Let flow the excess of gelatine.
7. If the coat of gel is not enough, repeat steps 5 and 6.
8. Put the balls in the fridge, until the sherbet balls are liquid.
With these experimental conditions (solution of gelatine in water at 12 g/L at room temperature
and cold ice balls) the pearls of gelatine didn’t set. The gelatine didn’t form a complete skin around the
III.1.3.5. Discussion/ Interpretation:
The first tests did not succeed: either the concentration in gelatine was too low, or the difference
of temperatures between the balls of sherbet and the solution was not important enough.
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The experiments were repeated using a higher concentration in gelatine with better results.
III.1.4. Balls of ice at very low temperature, coated by 1.2 % gelatine:
The material used is the same as in the first experience.