Study of the proximate and mineral composition of different Nigerian yam chips, flakes and flours

Yam (Dioscorea spp) is an essential tuber crop for hundreds of millions of people in many African, Asian and South American countries. Considering in particular Southwest Nigeria, chips, flakes and flours are amongst the most common shelf-stable traditionally-processed yam products. This paper reports a systematic study on the proximate (moisture, protein, carbohydrate, fibre, fat, ash and gross energy) and mineral composition of these three food commodities sold in Nigerian markets. Results showed no significant differences in the moisture, crude protein and fibre content of all samples (10.0-12.3, 2.7-4.3 and 1.3-2.0 wt%, respectively). Gross energy was also comparable for all yam derived food items (between 3300 and 3507 kcal/kg), contradicting the common belief that yam flakes have lower nutritional value than chips and flours. Considering the mineral composition, Ca, Mg, P and K were the predominant macronutrients. Micronutrients such as Zn, Co, Mn and Cu were also detected. Significant differences existed between products, and their various sources (markets). Principal component analysis showed a direct correlation between ash content of the samples and the assessed macronutrients, irrespective of the market, or the seller of the commodities. This study confirmed that yam derived food stuffs have an adequate nutritional composition, irrespective of their form and/or origin.