The large number of different molecules produced are responsible for the characteristic smells and
taste of the common caramel. When caramels are prepared in the presence of ingredients containing
proteins or amino acids (like cream or milk), in addition to caramelisation, the sugars will react with
amino acids from the proteins to produce an even greater variety of flavours and colours.
However, table sugar is often replaced by sugar substitutes, like aspartame. When this molecule is
heated, some of the aspartame molecules break down into an aspartic acid sugar unit and a
phenylalanine unit. These two sugars are not associated with this appreciated “caramel-taste” and
furthermore, aspartic acid has a slightly bitter taste.
Effect of acid
When a disaccharide such as sucrose is heated in the presence of acid, it will break down into its
component sugars. This is because the glycosidic bond that joins the two sugar units together is
broken down. Breaking a dissacharide up in this way is known as inversion, and has uses in the
kitchen, especially in making sweets because it reduces the amount of crystallisation.
Monosaccharides, by contrast, are little affected by pH because all the bonds in their structure are
very strong covalent bonds, which are not readily broken down in acid, and require very high
temperatures before they will start to break down.
Reactivity with proteins
Simple sugar molecules are also able to react with the subunits of proteins (called amino acids). When
an amino acid and a simple sugar meet, there is a rearrangement of atoms, and some atoms are
released (usually two hydrogen atoms and an oxygen atom, which forms a water molecule). New
molecules are formed from what remains. This simple reaction can produce many different new
molecules depending on which rearrangement has occurred. Furthermore, these newly formed
molecules can either break down to form other new compounds, or react further with each other to
produce other new molecules, or even react with other molecules if they are present (such as the fats)