Молекулярная гастрономия для креативных шеф-поваров (англ. язык) - страница 134

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

and freezing can prevent discoloration - blanching actually destroys the enzymes, whereas freezing

slows down their activity. (However, care must be taken to not under-blanch the fruit or vegetable - this

actually stimulates the activity of enzymes and produces more pronounced browning effects than does

blanching).

Alternatively remove the substrates: This is most easily done by removing the oxygen from the

surrounding area (the enzymes or substrates themselves are very hard to remove), by replacing the

air with either pure nitrogen or CO2 - this is often how pre-prepared cut vegetables are packaged.

Citrus fruits: Citrus fruits do not brown. Often, lemon juice is added to freshly cut fruits to prevent their

browning. This is not due to the acidity of the lemon juice slowing down enzyme activity, since the

addition of vinegar does not slow browning. Lemon juice contains high amounts of ascorbic acid (also

known as vitamin C). This molecule functions as an antioxidant (i.e. reverses the oxidation process),

and therefore reconverts the quinines formed back into their original uncoloured polyphenol molecule,

before they have the chance to form melanoidins.

Quinines + ascorbic acid _ polyphenols

Experiment :

To see this effect for yourself, cut three slices from an apple and leave them on a plate exposed to air.

To one add lemon juice, to the second vinegar, and the third a small amount of ascorbic acid powder.

The browning is...

one add lemon juice, to the second vinegar, and the third a small amount of ascorbic acid powder.

The browning is prevented most by the ascorbic acid (a pure form of vitamin C), to a lesser by the

lemon juice (a less pure source of vitamin C), yet the vinegar provides little anti-browning effect.

III/IV - 3 (of 11)

· The smell of garlic:

Raw garlic contains a sulfur based compound called alliin as well as an enzyme that acts on the alliin

called alliinase. In raw garlic, these two compounds are separated by different compartments - a whole

garlic clove therefore has little aroma. On cutting garlic, these special sub-compartments are broken,

allowing the enzyme to react with its substrate the alliin and convert it to allicin, which has a very

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