swollen grains fill the solution completely, so that it flows with difficulty and becomes thicker. Third,
when a lot of small solids are dispersed into water, the solution cannot flow as easily, and the sauce
thickens: this is the case of custard, as shown in the following pictures, showing respectively the
solution before cooking, being cooked, and being curdled:
II - 9 (of 9)
Of course, as thickening is very important in the kitchen and in the food industry, new thickening
agents have been discovered and used. Want to discover them?
Some specific compounds can impart sweetness to food: not only sucrose (table sugar), but also
glucose (the sugar that circulate in our blood and constitutes the fuel of our body), fructose (the sugar
present in honey) and others.
All these products, when pure, are white powders, or crystals, but they dissolve easily in water (but not
When dissolved in a small quantity of water, these sugars make syrups, i.e. viscous liquids, which can
contain,, with sucrose as an example, a maximum quantity of sugar (known as the dissolution limit) of
about 900 grams per litre, for sucrose. This means that when too concentrated, thee sugar can
crystallize out, and cooks should know that the faster the crystallization process, the smaller the
crystals formed (“grains”).
Crystallization means that the sugar molecules pile up regularly in all directions. Adding some glucose
to sucrose syrup can prevent crystallisation, because glucose molecules will be inserted in between
the sucrose molecules, and prevent their regular piling up. This is why glucose is used in sweets.
One should also know that chemically speaking, sucrose is “made of glucose and fructose”, which
means that heating sucrose and water for a long time, in particular after adding some acid (vinegar, for
example) can transform sucrose molecules into a mixture of glucose, fructose and sucrose. This can
be helpful when you don’t have any glucose syrup in your kitchen.
Chocolate is very popular, and that is easy to understand- it is made of fats, sugar, fibres and many