Effect of Plant Ash on Nutrient Quality and Antioxidant Activity of African Yam Bean Seed Porridge in Relation to Cooking Time

Anthony N Ukom,Faith C Egejuru,Ugwuona U Fabian,Philippa C Ojimelukwe

doi:10.4236/fns.2020.117042

Abstract

The present study aimed to investigate the nutrient quality, antioxidant activity and sensory acceptability of hard-to-cook African yam bean (AYB) seeds cooked for 5 h (control) and for 2 h with plant ash. The plant ash were unripe plantain peel ash (UPA), corn cob ash (CCA) and UPA and CCA mixture. Standard methods of Association of Official Analytical Chemists (AOAC) were used for the proximate and mineral analysis, DPPH, ABTS and FRAP assays were used to investigate the antioxidant activity. A completely randomized design with one way analysis of variance (ANOVA) was used for data analysis. The results showed that cooking of AYB seeds for 2 h with 8 g/100mL plant ash solution improved the nutrient contents, antioxidant activity and sensory scores of the porridge. Higher values of proteins, ash and energy were obtained in 8 g/100mL UPA/CCA and in 8 g/100mL CCA additives. However, moisture, fat and fibre contents were not affected by plant ash additives and were higher in 5 h cooked porridge. Cooking with 8 g/100mL plant ash solution for 2 h significantly increased mineral elements in the porridge. Phenolic compounds (total polyphenols and flavonoids), and antioxidant activity (DPPH, ABTS and FRAP) showed higher values with plant ash additives. This study reveals that addition of plant ash did not only reduce the cooking time of AYB seed by 60%, but also improved the nutrient quality, antioxidant activity and sensory acceptability.

Highlights

African yam bean (AYB) (Sphenostylis stenocarpa) is an herbaceous leguminous plant with increasing nutritional interest in Nigeria and West African countries
The results showed that cooking of AYB seeds for 2 h with 8 g/100mL plant ash solution improved the nutrient contents, antioxidant activity and sensory scores of the porridge
The results showed that cooking of AYB seeds for 2 h with plant ash (8 g/100mL) significantly improved the nutrient and sensory qualities, especially the protein, ash, energy, and mineral contents

Summary

Introduction

African yam bean (AYB) (Sphenostylis stenocarpa) is an herbaceous leguminous plant with increasing nutritional interest in Nigeria and West African countries. The amino acid profile of AYB seed is comparable to other legumes like cowpea, soybean and pigeon pea [1]. It is rich in minerals and fiber [2]. Utilization of AYB seed is limited due to the hard-to-cook (HTC) phenomenon arising from high temperature and relative humidity during storage [3], even up to nine months. This results in long cooking time and high energy expenditure, sometimes, overnight by the local people. AYB seed contains some anti-nutritional factors and oligosaccharides which can provoke flatulence and chronic health effects

Objectives

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Conclusion