Fjölrit RALA - 22.03.1979, Side 74

-68-
During the growth period of the potato it will contain
0.6-1.0% mono- and disaccharides (Pressey and Shan, 1966).
If it is stored at a low temperature, the content of these
compounds increases up to two- or threefold (Rönsen, 1969,
W.B. Burton, 1969, M.C. Jarvis et al., 1974).
W.C. Burton regards it desirable that the amount of
reducing sugars (glucose, fructose) in potatoes be over
0.25% because then the probability of them reacting with
proteins increases. This reaction results in the formation
of a brown pigment and is called Maillard browning (E.F.
Hoover and R.A. Kinder,1961, W.B. Burton, 1969). It is
especially important to keep this is mind when dealing
with potatoes which are to be used in the production of,
for example, potato chips.
If refrigerated, the amount of both reducing sugars
and sucrose increases. The increase is, however, rela-
tively greater for sucrose.
W.B. Burton (1969) showed that if potatoes are refrig-
erated slowly, for example, 2°C7week, the sucrose content
will be 2-3 times as much as if they were put directly into
the lowest temperature. On the other hand, the amount of
reducing sugars will be the same whether refrigerating slowly
or suddenly.
No research has been done in Iceland on mono- and di-
saccharides in Icelandic potato varieties.
4. Fat:
No results on fat measurements in Icelandic potatoes
have been recorded. The fat content is about 0.1%. Thereof
are 10% triglycerides, 4% stearin esters, 1% sterin, 25%
phosphatidyl ethanolamine, 25% lecithin, 15% monogalactosyl-
diglycerides and 15% digalactosyldiglycerides (A. Fricker
and W.D. Koller, 1974).
According to Fricker and Koller, the amount of linolenic
acid increases on storage while the amount of linolic acid
decreases.
Jarvis et al. (1974) showed that very little changes
occur in the fat during cooling from 18°C to 4°C. The amount
of phosphatidyl choline (lecithin) does, however, decrease
slightly and the amount of digalactosyl diglyceride increases.