Effect of drying and roasting on nutritional composition and lipid oxidation profile of marula (Sclerocarya birrea) kernels from Far-North Cameroon

Sclerocarrya birrea (Marula) is one of the underutilized wild edible fruit tree species that is grown in Far North Cameroon. The present study investigated the effect of different drying methods on the proximate composition, mineral content, and lipid oxidation of marula kernels consumed in Far-North Cameroon. Sun drying, oven drying, and roasting were employed. The proximate analysis was performed using AOAC methods. Lipid oxidation was evaluated by measuring free fatty acid (FFA), iodine value (IV), peroxide value (PV), p-Anisidine value (p-AV), and thiobarbituric reactive substances (TBARS). Results showed that raw marula kernel contains 7.31% moisture, 4.15% ash, 23.19% proteins, 47.73% lipids, 8.90% carbohydrates, and 7.49% crude fiber. Marula kernels are good sources of phosphorous (P: 1311.88 mg/100g), calcium (Ca: 1144.13 mg/100g), potassium (K: 983.87 mg/100g), zinc (Zn: 7.60 mg/100g), and iron (Fe: 7.04 mg/100g). All the processing methods significantly increased (P<0.05) the ash, protein, lipid, and carbohydrate contents of the marula kernel. An increase in Ca, P, K, magnesium (Mg), Fe, and Zn were also noted. During processing, FFA, PV, p-AV, and TBARS increased significantly (P<0.05), while IV decreased. Oven drying at 80 °C was the best method, given the high protein content, while roasting for 10 min provided the highest lipid content. The oven-dried sample at 40 °C was found to have the best oil qualities.