richness of plant tissues. All the culinary processes used for meat can be used, as long as the
conditions are appropriate.
But vegetables and fruits also are a wider spectrum of properties that have to be taken into account.
Color is one of them.
For example, green beans are appreciated for their special flavour, consistency and color. In the
kitchen, cooks make efforts to keep this color: they avoid cooking with a lid, they stop the thermal
heating by dropping the beans in water with ice when they consider the beans cooked, etc. Are they
right? At a time when the Earth seems to be warming, energy preservation is crucial, and cooking
without lids is a waste of energy. In our laboratory, and in many lectures, we demonstrated that there
is no color difference when cooking with or without a lid (for beans, broccolis, romanesco). And we
also showed that putting the beans in cold water after cooking does not keep a better green color.
How should cooks behave using these informations? First they should cook in pans with a lid (better
energy efficiency), and they should only stop the cooking process some time before having the right
texture, soaking the beans to get finally the appropriate texture.
We also tested some “culinary precisions” on red fruits: it was written that red fruits should never been
put in copper vessels lined with tin. As tin metal is unlikely to react chemically with the compounds of
red fruits, this culinary precision seemed dubious… and it was first shown that it was wrong: putting
raspberries or gooseberries, or strawberries in contact with tin does not make any visible difference.
However, could tin ions have an effect? Yes! If you add some Sn 2+ ions to raspberries, they get
almost immediately a dark purple color, because of complexation of anthocyanin molecules
(responsible for red colour) with tin ions.
Let’s consider a last example with pears. It was sometimes written that pear jams could be obtained
red when pears where cooked with copper pans lined with tin. True or not? The experiment of cooking