Amino Acid Profile and Physicochemical Properties of African Locust Bean (Parkia biglobosa) Seeds as affected by Combined Irradiation and Cooking

This study examined the impact of cooking, Co-60 gamma irradiation (5 kGy and 10 kGy) and combined irradiation (10 kGy) and cooking treatments on the amino acid profile and physicochemical properties of African locust bean (Parkia biglobosa) seeds, as well as the quality of the seed oil. The treated and untreated (control) seeds were mechanically dehulled and milled into flour using an attrition mill, and subsequently analysed for chemical composition, amino acid profile, functional properties and quality of the seed oil. The results showed a significant increase in the fat content (p ≤ 0.05) after cooking and post-irradiation cooking treatments. The cooked seed samples recorded a 3.84% increase in total mineral content although there was a loss in the total percentage minerals after combined irradiation and cooking which could be linked to leaching of soluble minerals into cooking water. The 10 kGy irradiation dose improved the total essential amino acids present in the seed possibly due to the lyses of adherrent microflora. Percentage cysteine was highest in the 5 kGy irradiated seed sample with about 4.8% increase compared to control. There was a 92.6% loss in foaming capacity of the seed flour as a result of processing; however, 5 kGy irradiated sample recorded only about 26% loss in the foaming capacity. The anti-nutrients were significantly reduced by cooking, irradiation, post-irradiation cooking up to about 60%, 40%, 26.7% and 60% for cooked, 5 kGy irradiated, 10 kGy irradiated and post-irradiated cooked samples, respectively. Tannin content was not significantly affected (p<0.05) by the irradiation treatments; it was however reduced significantly by post-irradiation cooking. The 5 kGy and 10 kGy doses did not significantly affect iodine value of the oil sample. There was however an increase in iodine value as a result of cooking and post-irradiation cooking with values as high as 163.53 g I2 and 182.77 g I2 per 100g, respectively. Overall, it could be concluded that medium dose gamma irradiation did not negatively affect the quality of the African locust bean seed, which is desirable for elongation of storage life of the seed.