Fjölrit RALA - 22.03.1979, Page 76

-70-
point. The type of soil has much less effect on the amount
of this vitamin (J. Augustin, 1975).
8. Ascorbic Acid (Vitamin C):
Sigurjónsson carried out extensive research on the vita-
min C content of potatoes 1945-49. Six varieties were inclu-
ded in his sutdies (Gullaugen, Kerr's pink, Alpha, Arran Pilot,
"Rauðar íslenzkar" (Red Icelandic) and "Bláar xslenzkar" (Blue
Icelandic)) and measurements were done on four potatoes of each
variety.
Sigurjónsson's results show that the vitamin C content
varies greatly depending on the variety. This is in accord-
ance with results from J. Augustin in 1975. The variation
between varieties was, according to Sigurjónsson, from 5 to
25 mg/100 g.for fresh potatoes.
In addition tD the variety of the potato playing an im-
portant role in the amount of vitamin C it will contain, it
will still depend mainly on the environmental factors. Pota-
toes in sandy soils are richer in vitamin C than those grown
in humus soils. In addition, increasing the use of nitrogen
fertilizers causes the vitamin C content to decrease consid-
erably (J. Augustin, 1975, J. Augustin et al., 1975).
The time of harvesting also affects the vitamin C content.
Potatoes harvested early contain considerably more vitamin C
than those harvested later (J. Augustin et al., 1975).
Vitamin C diminishes quickly during storage (J. Augustin,
1975, J. Augustin et al., 1975, Sigurjónsson, 1957). The
results of Sigurjónsson show that during the first two months
in storage, the vitamin C content has decreased by 50%, but
after this period of time, it decreases more slowly. During
the next 6 months in storage, the decrease is so slow that
at the end of this time period the total decrease is only
30-35%.
After a storage period of 2-3 months, the vitamin C con-
tent of potatoes varies insignificantly between varieties
(J. Augustin, 1957, Júlíus Sigurjónsson, 1957).
Experiments carried out on the Russel Burbank variety
show that there is a linear relationship between the decrease
in vitamin C content and the logarithm of the storage time