Environmental Engineering Reference
In-Depth Information
variable from one yam type to another, ranging from about 40 per cent up to
about 92 per cent (
digi
). This variability may be explained partly by the fact
that various yam types require a different planting time, as well as planting
depth. These issues require further investigation.
Length of petiole was also very variable, ranging from 1.2 to 10.7 cm.
Similarly, other morphological characteristics show great variability from type
to type (Table 8.3). Almost all the yam types also showed clockwise circummu-
tating. Regretfully this type of information was not available for the
nkanfu
yam
type.
Great dissimilarity in tuber weight and length at the end of the growing season
corresponded well with already observed variations in vegetative characteristics
during the season. The tuber weight ranged from 0.06 (
nyuwogu
) to 2.30 kg
(
kpuno
). The number of stems also ranged from one (
zong
,
friginli
,
chamba
) to
about eight (
nyuwogu
,
chenchito
).
Chemical content
In order to complement effectively the traditional knowledge and field obser-
vations, laboratory analysis of the chemical content of 22 yam types was also
conducted with the assistance of the Food Research Institute Laboratory, Accra,
in 2001.
Data on seven parameters obtained during the tuber analysis and a summary of
the results are presented in Table 8.4.
Moisture content was variable for various yam types.
Manchisi
had the highest
moisture content (71.9 per cent), and
chamba
(50.2 per cent) had the lowest mois-
ture content.
Coursey (1976) reported that ash content of yams is high, but varies
from species to species. Apart from
zong
(1.6 per cent),
nyuwogu
(1.6 per
cent), and
friginli
(1.5 per cent), which had the highest ash content, the rest of
the yam types from Bongnayili-Dugu-Song had ash contents ranging from 0.9
to 1.4 per cent.
Contrary to some earlier reports indicating relatively high protein contents in
yam, among the 22 types collected, the protein content ranges from 1.6 (
manchisi
)
to 4.1 per cent (
kan-gbaringa
), which is rather low. Starch content was very vari-
able, ranging from 6.0 (
mogni-nyugo
) to 27 per cent (
kpuringa
).
Tindal (1983) reports that 100 g yam has about 1 mg phosphorus and 0.8 mg
of iron. Yams at Bongnayili-Dugu-Song have a phosphorus level content
ranging from 29.2 mg/100 g (
gun-gonsalli
) to 3.8 mg/100 g (
kukulga
), iron
content ranging from 11.1 mg/100 g (
zong
) to 0.5 mg/100 g (
gun-gonsalli
,
friginli
,
baamyegu
,
digi
,
kpuringa
,and
liilya
), and a variable calcium content
