The Effect of r-irradiation and Cooking on the Physicochemical Properties of African Oil Bean Seed (Pentaclethra macrophylla benth) and Its Oil Extract

Irradiation is a potentially useful technology for ensuring the safety and extending the shelf-life of food products. The effects of r-irradiation (5kGy, 10kGy), cooking and combined treatment of 10 kGy irradiation and cooking on the chemical and functional properties of African oil bean seed (Pentaclethra macrophylla Benth) and physicochemical properties of its oil were investigated. The irradiated seeds and un-irradiated seeds were mechanically dehulled and milled into flour using an attrition mill. ‘Raw seed’, ‘cooked seed’, ‘irradiated (5kGy) seed’, ‘irradiated (10kGy) seed’ and ‘irradiated (10kGy) and cooked seed’ flour samples were analyzed for proximate composition, mineral content, functional properties and antinutritional factors, and the seed oils were analyzed for peroxide value, iodine value, acid value and free fatty acid content. The results show that the combined effect of r-irradiation and cooking gave highest increase in nutritional quality, reducing protein from 32.91g/100g DM in the raw seed to 30.55g/100g DM and increasing fat content from 47.43g/100g DM to 51.19g/100g DM. Combined treatment led to the retention of sodium, calcium, zinc and iron more than the single treatments, but the same process reduced magnesium from 0.52mg/100g to 0.47mg/100g and phosphorus from 0.43mg/100g to 0.35 mg/100g. Least gelation concentration and emulsion capacity increased with combined r-irradiation and cooking, whereas foaming capacity and water absorption capacity decreased significantly (p<0.05). Gamma-irradiation and cooking reduced the concentration of all the antinutritional factors. Combined r-irradiation and cooking increased the peroxide value significantly (p<0.05) from 7.03 mg/g oil to 16.50 mg/g oil and increased the acid value, iodine value and free fatty acid of P. macrophylla seed oil. Combination of r-irradiation and cooking increased nutrient bioavailability in the seed; it led to improvement in the functional properties and increased the susceptibility of the oil to rancidity.