|
In
Asia, effort is being made to promote sweetpotato as a nutritional
crop.
Root
crops are often considered to be nutritionally inferior to cereals. However,
when compared on an equal energy basis (Table 1), sweetpotato has an average
protein concentration comparable with that of rice. Furthermore, the protein
concentration in sweetpotato is highly variable, and there is potential for
significantly improving the average through both genetic and management factors.
Sweetpotato
is also a good source of calcium, ascorbic acid (vitamin C) and b-carotene
(provitamin A). The yellow- to orange-fleshed cultivars contain particularly
high levels of carotenoids, and are equalled only by carrot as a source of
provitamin A. Vitamin A deficiency is a common and serious health problem in
many countries with rice-based diets, being the main cause of blindness in
children. Less acute deficiency decreases children’s resistance to infectious
diseases, contributing to infant mortality. In response to this problem, efforts
are being made in some Asian countries to promote the use of yellow-fleshed
cultivars of sweetpotato. There is scope for breeding yellow-fleshed
sweetpotatoes with higher dry matter and lower sugar content, which are more
acceptable to users of traditional staple varieties.
The young leafy shoots, which are eaten
as a green vegetable in some countries, particularly in Asia, are high in
protein (approximately 20% of dry weight), and are also a good source of
b-carotene, thiamine (vitamin B1), riboflavin (B2), folic acid and ascorbic acid
(Villareal et al., 1985; Woolfe, 1992).
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Table
1. Edible energy yield, and approximate composition per MJ edible
portion, of sweetpotato and other major tropical staple crops. |
|
Crop
|
Edible
Energy Yield MJ/ha/da |
Proteinb
(g) |
Calciumb
(mg) |
Ironb
(mg) |
ß-carotene
equiv.b,c (mg) |
Thiaminea
(mg) |
Riboflavin
(mg) |
Niacina
(mg) |
Ascorbic
Acida,c (mg) |
|
Sweetpotato |
201 |
3.6 |
67 |
1.5 |
0-42d |
0.22 |
0.08 |
1.5 |
62 |
|
Cassava |
146 |
1.7 |
66 |
1.9 |
0-0.25 |
1.10 |
0.05 |
1.1 |
48 |
|
Potato |
205 |
5.9 |
25 |
2.3 |
Trace |
0.31 |
0.11 |
3.4 |
85 |
|
Banana |
184 |
3.3 |
20 |
1.5 |
1.0-2.6 |
0.09 |
0.09 |
1.3 |
38 |
|
Rice |
138 |
4.1 |
14 |
0.3 |
0 |
0.04 |
0.02 |
0.7 |
0 |
|
Wheat |
142 |
7.5 |
21 |
1.1 |
0 |
0.21 |
0.06 |
1.4 |
0 |
|
Maize |
155 |
5.7 |
13 |
1.9 |
0.3 |
0.23 |
0.09 |
1.3 |
0 |
|
Sorghum |
100 |
7.6 |
11 |
4.7 |
0 |
0.33 |
0.08 |
2.3 |
0 |
|
Sources:
ade Vries et al. (1967), derived from Platt
(1965);
bWoolfe
(1992)
cLosses
of 18-78% of ascorbic acid (Vitamin C) and 20-25% of carotenoids are
incurred during boiling.
dHigher
carotenoid content is found in orange-fleshed cultivars. |
Source:
O'Sullivan, J.N., Asher, C.J., and Blamey, F.P.C. 1997. Nutrient disorders of
sweetpotato. ACIAR Monograph No 148, 136 p.
|
Origin
Botany
and morphology
Importance
Growing
environments
Utilisation
|
