Post-harvest losses occur at various stages
from production, postharvest handling, marketing, distribution and processing.
These include losses in quantity and tuber quality, arising from physical damage,
rodent attack, fungal and bacterial diseases, and physiological processes such
as sprouting, dehydration, and respiration. Estimated loss of 10-60% of total
crop has been reported (NAS, 1978). Weightloss during storage in traditional
or improved barns, or clamp storage can reach 10-12% in the first 3 months and
30-60% after 6 months. Weight losses alone of 33-67% after 6 months storage
have been reported (Coursey, 1967). In West Africa alone, this amounted to an
annual loss of one million tonnes of tuber (Akoroda and Hahn, 1995).
The magnitude of weight loss in stored yams
increases rapidly after the first months (Table 8). Transit losses of about
15-40% occur in some developing countries due mainly to inefficient storage
and transport facilities. Losses of D. alata
cultivars varied from 7-23% during 4 months of storage (Gooding, 1960), and
in Puerto Rico, postharvest losses of yams due to decay exceeded 50% (Burton,
1970). Processing losses during culinary preparation of peeled yam can amount
to 10-15%.
| Table 8:Weight loss in stored yams. | ||||||
| Percentage weight loss during storage | ||||||
| Country | Species | 1 month | 2 months | 3 months | 4 months | 5 months |
| Puerto Rico | Guinea yams | 1 | 3 | 8 | (sound tubers) | |
| 2 | 6 | 11 | (tubers slightly infected by rots) | |||
| Nigeria | D. rotundata | 5 | 7 | 12 | 20 | 29 |
| 4 | 6 | 10 | 14 | 21 | ||
| 3 | 6 | 14 | 23 | 30 | ||
| D. cayenensis | 6 | 17 | 29 | 39 | 48 | |
| Ghana | D. rotundata | 1 | 5-7 | 15-17 | 26-27 | 34-40 |
| Source: (Coursey, 1967). | ||||||