Page 281 - Algae Anatomy, Biochemistry, and Biotechnology

264 Algae: Anatomy, Biochemistry, and Biotechnology

germinate and young sporophytes begin to grow on the frames, which are free of epiphytes. The
sporophytes are out-planted on floating ropes in the usual way.
Undaria is processed into a variety of food products. After harvesting, the plants are washed
with seawater, then freshwater, the central midrib is removed, and the pieces are dried in the sun
or a hot air dryer; this is suboshi wakame. However, as this product often fades during storage
because various enzymes are still active, another process can be used in which the fresh fronds
are mixed with ash from wood or straw, so that the alkalinity of the ash inactivates the enzymes.
This mixture is spread on the ground for 2–3 days, placed in plastic bags and kept in the dark.
The plants are washed with seawater, then freshwater to remove the salt and ash, the midrib is
removed and the pieces are dried. This is haiboshi wakame, which keeps its deep green color for
a long time, and retains the elasticity of the fresh fronds.
The major wakame product is salted wakame. Fresh fronds are heated into water at 808C
for 1 min and quickly cooled. The mixture is then dehydrated after 24 h incubation with salt
(30% w/w) and then stored at 2108C. When ready for packaging, it is taken from storage, the
midribs are removed, and the pieces placed in plastic bags for sale. It is a fresh green color and
can be preserved for long periods when stored at low temperatures.
Cut wakame is made from salted wakame, which is washed with freshwater to remove salt, cut
into small pieces, dried in a flow-through dryer and passed through sieves to sort the different sized
pieces. It has a long storage life and is a fresh green color when rehydrated. It is one of the most
popular dried wakame products used for various instant foods such as noodles and soups, and its
consumption is very popular.
The crude protein content of wakame and kombu is 16.3 and 6.2 g (g/100 g), respectively, and
both algae contain all essential amino acids, which account for 47.1% of the total amino acid
content in wakame and for 50.7% in kombu. Table 7.2–Table 7.4 summarize the vitamins,
minerals, and fiber contents of the two edible algae. This data shows that wakame and kombu
have high contents of b-carotene, that is, 1.30 and 2.99 mg (100 g d.w.) 21 or 217 and 481 mg
retinol (100 g d.w.) 21 , respectively. The basic component in sea vegetables is iodine, an essential
trace element and an integral part of two hormones released by the thyroid gland. According to the
results in Table 7.3, wakame and kombu contain 26 and 170 mg (100 g d.w.) 21 of iodine, respect-
ively. The recommended daily dose for adults is 150 mg, meaning that the consumption of 557 mg
of wakame and 88 mg of kombu would satisfy the daily requirement for iodine. The toxic dose of
iodine for adults is thought to be over 2000 mg day 21 . The intake of recommended amount of
wakame and kombu per day would supply 0.94 and 6.29 mg of iodine, respectively, meaning
that 1.18 g of kombu a day would not exceed the recommended safe dose of iodine. However, it
is claimed that iodine supplements can be toxic only if taken in excess, while eating sea vegetables
should cause no concern.

TABLE 7.2
Vitamin Contents of Marine Algae Wakame (U. pinnati-
fida)and Kombu (L. japonica) (in mg [100 g d.w.] 21 )

Vitamins Kombu Wakame
b-carotene 2.99 + 0.09 1.30 + 0.12
Retinol equivalent 0.481 + 0.015 0.217 + 0.006
0.24 + 0.02 0.30 + 0.04
Vitamin B 1
0.85 + 0.08 1.35 + 0.09
Vitamin B 2
0.09 + 0.01 0.18 + 0.02
Vitamin B 6
Niacin 1.58 + 0.14 2.56 + 0.11