Optimising Cassava‐Yam Composite Gari for Improved Zinc and Quality Attributes

This study investigated the effects of yam quantity (YQ) (X 1 ), fermentation duration (FD) (X 2 ) and roasting temperature (RT) (X 3 ) on the physico‐nutritional and sensory qualities of the composite gari. A Box–Behnken response surface methodology (RSM) was used to optimise the bush yam content (10%–30%) and spontaneous fermentation time (1–3 days) to prepare gari at different RTs (100°C–140°C). Increasing the YQ, FD and RT (up to 120°C) significantly ( p < 0.05) increased the beta‐carotene content of the gari from 4.4 to 8 μ g/g. Similarly, the zinc content of the gari increased significantly from 60 to 80.5 μ g/g when the YQ was increased. Both YQ and increased FD reduced the swelling capacity (3.3–2.7), whereas RT improved it significantly ( p < 0.05). YQ (up to 30%) decreased the flavour (7.4–6.2), taste (7.6–6.5), texture (7.4–6.2), overall acceptability (8.2–6.6) and brightness (40–30), whereas fermentation improved them. Moreover, the quantity of yam contributed more to the browning index and colour difference than the other variables. YQ positively affected the yellowness (b∗), with a greater effect. From the optimisation analysis, the optimal processing variables for the cassava‐yam composite gari are a YQ of 24%, FD of 3 days and a RT of 100°C. A 100‐g portion can meet 99%, 72%, 99%, 72% and 89% of the zinc requirements for children, men, women, pregnant women and adolescents. Partly substituting cassava mash with bush yam mash could potentially improve the zinc and provitamin A carotenoid contents of gari while preserving sensory attributes.