Abstract
Yams (Dioscorea spp) are among the oldest food crops. It is estimated that after six months of storage up to 56% of the crop is lost to rot. In Nigeria, fresh yam tubers are used for production of Elubo (yam flour) for preparation of amala, as it is called among the Yoruba in Western Nigeria, and akwunaji in the east of the River Niger. Many researchershave emphasized the importance of microbial rotting in causing storage losses. This study evaluated the effect of yam rot on the nutritional values of Fusarium infected yam tubers.Tubers from two yam (Dioscorea rotundata Poir.)varieties-Nwopoko and TDr95/19177-were infected with Fusarium nygamai pure culture and stored for 12 weeks, after which the tubers were used to produce yam flour and were analyzed for their nutrient composition comprising: dry matter/ moisture content, ash, total sugar, starch, amylose, vitamin C, protein and tannins. Wholesome yams of the same varieties were also used to produce yam flour and equally evaluated for the same nutrients. Infection with Fusariumnygamai led to a significant reduction (p<0.05) in the nutrient composition of the infected yam flour compared with those ofwholesome samples. Vitamin C content reduced from 41.10 to 27.26 (mg/100g) in variety Nwopoko and 36.30 to 30.53 (mg/100g); in variety TDr95/19177. Corresponding values for protein content was from 5.05 to 4.60% and 4.93 to 4.62%; Ash Content from 1.32 to 1.30% and 1.36 to 1.24%; Total Sugar Content from 5.34 to 5.20% and 5.21 to 5.02%; Starch 78.71 to 77.61 and 89.28 to 81.53%; Amylose from 29.95 to 28.87% and 30.01 to 27.95%. However, an increase in the tannin content – (1.84 and 1.94 mg/g) as against (0.31 and 0.26 mg/g) in Nwopoko and TDr 95/19177 varieties respectively was observed. The increase in the tannin content implies an increase in the antinutrient composition. The tendency to produce Elubo used for preparation of amala with rotten yam (possibly Fusarium infected) should be discouraged.
Highlights
Yam (Dioscorea spp) are important food crops in West Africa, the Caribbean, the Northern and Central parts of South- East Asia, including parts of China, Japan, Malaysia and Oceania Orkwor et al, 1998
West Africa produces the greatest percentage of yam mainly in Nigeria, Benin, Togo, Ghana and Ivory Coast- the five yam zone countries Orkwor et al, 1998
Sources of Yam Tubers: The yam (Dioscorea rotundata Poir.) tubers from Nwopoko and TDr 95/19177 were harvested at matured stage (8 months) from the field of the Yam Programme of the National Root Crops Research Institute (NRCRI), Umudike
Summary
Yam (Dioscorea spp) are important food crops in West Africa, the Caribbean, the Northern and Central parts of South- East Asia, including parts of China, Japan, Malaysia and Oceania Orkwor et al, 1998. Yams are among the oldest recorded food crops. It is an important crop in Nigeria, where it is produced both as a food and cash crop. Fresh yam tubers are peeled, chipped, fermented, dried and milled into flour. This flour is cooked in boiling water, turned into a thick paste similar to fufu, and eaten with soup. Pounded yam is by far the most popular food from yams in Nigeria (Hahn et al, 1987)
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