significantly after treatment (composition of a leaf of green tea given in the appendix 7; according to "food
chemistry " xv).
The quantities of the different tea compounds that are present in the drink are dependent on
various factors. The main factors are the solubility of these components, the temperature of the water and
the time of infusion. In the case of fermented teas, 38 to 40 % of the dry material is soluble in hot water,
which is more significant than in the case of roasted coffee. For all the tea varieties, the intensity of the
savours is correlated to both the total quantity of polyphenols and the activity of polyphenol oxidases
(stopped in the case of green teas)16.
III.6.2. Gels from infusions of tea.
III.6.2.1. Material :
· Green tea (Sencha Silver).
· Tap water.
· Gelatine and Agar-agar provided by Louis Francois.
· Carrageenan Kappa (+locust bean gum), IBERAGAR product Ref S-3847 / 04.
· A plastic bowl of 1 L .
III.6.2.2. Method :
1. Make an infusion with 20 g of tea in 1L of water.
2. Filter the solution, and keep the leaves..
3. Split the solution into 5 bowls of 200 g.
4. Repeat the steps 1 to 3 five times, reusing the same tea leaves.
5. Take 3 samples from 3 successive experiments and add some gelatine to form a gel at 1% and keep
them in the fridge. We wish to observe the complex formed between tannins (or more generally
phenolic) and proteins of gelatine.
6. Take 3 samples from a same infusion and add some agar-agar to form a gel at 1% and keep them in
the fridge. We wish to compare the efficiency of the gelatine to the one of the agar-agar.
7. Make gel with kappa carrageenan (also 1%) with 3 samples.
8. Make one master sample with each gelling agent.
9. The other samples are kept aside and will be used for further experiments.
Figure 22: Infusion of green tea with agar agar at 1 %.
22 / 63
The solutions with gelatine get cloudy and do not set well in gel. Other gelling agent give good
III.6.2.4. Discussion/ Interpretation:
III.188.8.131.52. Concerning gelatine: