Food Chemistry

6.3 Water-Soluble Vitamins 419

Diketogulonic acid degradation products, xy-
losone and 4-deoxypentosone (Formula 6.21), are
then converted into ethylglyoxal, various reduc-
tones (cf. 4.2.4.3.1), furfural and furancarboxylic
acid.

(6.21)

In the presence of amino acids, ascorbic acid, de-
hydroascorbic acid and their degradation prod-
ucts might be changed further by entering into
Maillard-type browning reactions (cf. 4.2.4.4).
An example is the reaction of dehydroascorbic
acid with amino compounds to give pigments,
which can cause unwanted browning in citrus

(6.22)

juices and dried fruits. The intermediates that

have been identified are scorbamic acid (I in

Formula 6.22), which is produced byStrecker

degradation with an amino acid, and a red

pigment (II). A wealth of data is available on

ascorbic acid losses during preservation, storage

and processing of food. Tables 6.1 and 6.2 and

Figs. 6.3 and 6.4 present several examples.

Ascorbic acid degradation is often used as

a general indicator of changes occurring in food.

Fig. 6.3.Ascorbic acid losses as a result of cooking of

cabbage (according toPlank, 1966)