Молекулярная гастрономия для креативных шеф-поваров (англ. язык) - страница 133

Молекулярная гастрономия для креативных шеф-поваров (англ. язык)

Water is found throughout the plant structure, and the cell wall functions to control the movements of

water into and out of the cell. When the plant is living, vegetable cells contain much water. This gives

the cells rigidity, which is called “turgor”, and this also contributes to vegetable texture. After harvesting

the fruits or vegetables, water is lost from the vegetable cells and the vegetable wilts, which is why

vegetables and fruits should be eaten fairly soon after harvesting.

The most important proteins found in plants that we are interested in are the pigments, which play an

important role in determining the plants colour.

Preparing vegetables

As the world of plants is almost infinite, we can only examine some important cases in the kitchen.

· Fruit and vegetable browning:

If a freshly cut slice of apple or avocado is left on a plate, it will turn brown. When vegetables are

peeled or cut up, the fine structure of the vegetable or fruit cells which have been cut will be destroyed

and cell compartment will release their contents. Amongst their contents, enzymes will be released

from their special compartments and are free to find their target – the substrates.

III/IV - 2 (of 11)

For example, enzymes called polyphenol oxidases are released from their special compartment, and

are free to find their substrate, the uncoloured fruit molecules called polyphenol, and greatly speed up

the reaction between this uncoloured ...

substrate, the uncoloured fruit molecules called polyphenol, and greatly speed up

the reaction between this uncoloured molecule and oxygen in the air to form molecules called

quinines. The quinines formed in this way react with each other, and rearrange themselves to form

brown melanoidins– these are molecules of the same kind as ones that allows us to tan!

polyphenol + oxygen _ quinines _ melanoidins

+

The melanin forming reaction in the absence of enzyme (white, polyphenol and oxygen, brown,

melanoidin)

The melanin forming reaction in the presence of enzyme (shown as green)

There are a number of ways to prevent this undesirable browning:

Firstly, remove the enzyme: The enzyme can be removed by changing temperature: - both blanching

Страницы: Пред. | 1 | ... | 131 | 132 | 133 | 134 | 135 | ... | 253 | След.

Еще статьи