The influence of cooking methods on the antioxidant status of <i>Tetrapleura tetrapetra</i>

Abstract

Africa is blessed with a rich array of local spices such as Tetrapleura tetraptera. The culinary uses of T. tetraptera are many. The seed of Uhiokirihio is majorly used in the preparation of ‘Banga’ (palm fruit) soup, meat pepper soup and other types of soup in the southern part of Nigeria. It is also commonly used in soups of nursing mothers to prevent post-partum contractions. The rich antioxidant activity of this spice has been reported. There is, however, a dearth of information on the effect of different cooking methods on its antioxidant activity. This study, therefore, evaluated the effect of cooking methods on the antioxidant status of the seeds of Tetrapleura tetraptera. The raw seeds of the spice were both toasted and boiled separately for 0, 5, 10, 15 and 20 minutes, respectively. The samples were analysed for anti-nutrients, vitamin contents and antioxidant properties. Anti-nutrient evaluation of the ethanolic (80% ethanol) extract revealed that both toasting and boiling time caused significant (p<0.05) variations in all the anti-nutrients studied. Total phenolics increased (p<0.05) from 20.80mg/100g to 28.53mg/100g for toasted samples and from 20.80mg/100g to 30.51mg/100g for boiled samples, respectively. Both cooking methods caused significant reduction in the phytate and tannin levels of the seeds. At the end of the cooking processes, tannin level was reduced by 62.07 % for boiling and 75.68 % for toasting treatment. The cooking methods led to significant reduction in both the vitamin C and β- carotene levels of the samples. Boiling for 20 min caused a 91.98% decrease in vitamin c and a 59.52 % decrease in β-carotene while toasting reduced these nutrients by 86.73 % and 39.88 %, respectively. Antioxidant activity as measured by DPPH scavenging activity and FRAP showed a significant rise with increase in cooking time. The DPPH activity of the toasted samples increased from 22.06μg/ml to 27.64 μg/ml while the boiled samples increased from 22.06μg/ml to 43.26μg/ml. It was observed that boiling led to a greater increase in total phenolics and antioxidant activity than toasting. It could, therefore, be concluded that cooking T. tetraptera seeds would improve its antioxidant properties.