Phytoconstituents and Polycyclic Aromatic Hydrocarbon (PAH) Content of Roasted Dioscorea dumetorum (Bitter Yam)

Abstract

Background and Objective: Most of the staple foods enjoyed by the populace are prepared by either roasting or smoking methods. The primary purpose of this study was to evaluate the proximate concentration and distribution of PAHs and anti-nutrients in roasted Dioscorea dumetorum (bitter yam) consumed by people in Nigeria. Materials and Methods: Materials used include charcoal, firewood, bitter yam and pieces of plastic. All chemicals used were of analytical grade. The bitter yam was roasted with firewood, charcoal and augmented charcoal and the levels of Polycyclic Aromatic Hydrocarbons (PAHs), the proximate analysis and the anti-nutrient content were investigated using standard methods. Results: The proximate analysis showed that crude fibre, protein, fat, ash and carbohydrate content varied with changes in the roasting method and were lower than the fresh sample. This study also showed that roasting decreased the anti-nutrient content of yam samples while those roasted with firewood recorded the least content. None of the PAHs detected was above the permissible limit of 5 µg gG 1 stipulated by the World Health Organization (WHO). Yam roasted with augmented charcoal accumulated the highest PAHs (4.4426 µg gG 1 ) when compared to those roasted with firewood (3.4742 µg gG 1 ) and charcoal (1.8044 µg gG 1 ). Fluoranthene and dibenzo(a,h)anthracene were detected in all the roasted yam samples. Conclusion: This study showed that roasting decreases anti-nutrient content in Dioscorea dumetorum and that Naphthalene will be the most deposited PAH after roasting.