NO - Besoin d'assistance

Composition of tomatoes and tomato products in antioxidants (WG1) page 89
__________________________________________________________________________________________
d) the solutions diluted are not stable overnight even in the refrigerator (should be
kept in the freezer).
9.1.7 Differences Between our Analytical Method and One of Hart & Scott.
- Quantity of tomato derivatives to weigh . Particular extraction for peels.
- Use of THF instead of CH2Cl2 to redilute samples after evaporation with rotavapor:
THF seems to be the best solvent to extract lycopene in tomato matrix and secondary CH2Cl2
is responsible of decreasing in lycopene concentration after storage (even just 1 day).
- Temperature of columns: not thermostated at 22.5 (from 20 to 24°C air conditioned
ambiant temperature.
9.2 Vitamin C in tomatoes and in tomato products.
Vitamin C, the antiscorbutic vitamin necessary for normal body functions, is correctly
associated by consumers with tomato juice and other tomato products. Whole red-ripe
tomatoes contain nearly all the vitamin C activity in the reduced ascorbic acid form.
Dehydroascorbic acid has been reported to be from 1 to 5% of the total ascorbic acid in
tomatoes.
The ascorbic acid concentration in fresh ripe tomatoes is about 25 mg per 100g.
9.2.1 Processing effects on Vitamin C.
The maintenance of high levels of ascorbic acid products during processing has
received considerable emphasis by food technologists. In the manufacture of tomato juice,
ascorbic acid is destroyed, mainly by oxidation. Ascorbic acid is oxidized to dehydroascorbic
acid, wich is further oxidized to degradation products with no vitamin C activity.
The oxidation may be enzymatic or non enzymatic, and is catalized by copper ions.
The rate of oxidation is dependent on the dissolved oxygen, enzyme content, dissolved