Effect of Heat Treatment on the Amino Acid Profile of Plukenetia conophora Seed Kernel Flours

The effect of heat treatment on the amino acid composition of Plukenetia conophora (African walnut) seed flours was investigated. The seed kernel of Plukenetia conophora (PC) is eaten roasted or cooked mainly as indigenous snacking nut in Nigeria. The sample was divided into four lots. The 1st was used raw, the 2nd, 3rd and 4th boiled in water (99±1°C) for 45, 90, and 135 min and labeled PCraw, PC45, PC90, and PC135 respectively. The kernels were found to contain amino acids found naturally in plant protein. Glutamic acid (7.88-18.5 g/100 g protein) and aspartic acid (4.86-9.16 g/100 g protein) were the most abundant non-essential amino acids while the essential amino acid ranges were for leucine (4.50-7.80 g/100 g protein), lysine (3.65-7.09 g/100 g protein) and arginine (3.22-6.12 g/100 protein). In addition to leucine other branched-chain amino acids (Isoleucine and valine) were present in high proportion. Cooking progressively decreased the level of all amino acids. For essential amino acid, the percent decrease ranged from 6.07% for lysinein PC45 to 64% for isoleucine in PC135. Protein quality parameters such as: predicted protein efficiency ratio, total amino acid, total essential amino acid, total acidic amino acid, total neutral amino acid, total aromatic amino acid and total sulphur amino acid though decreased by cooking were comparable to those of some plant foods and recommended standards. Based on whole hen’s egg amino acids, FAO amino acid provisional pattern and Food and Nutrition Board/Institute of Medicine (FNB/IOM) pattern for 1-3-year-old child, the percentage adequacy (Essential amino acid score) of most of the essential amino acids in the samplesat all levels of cooking were high. Despite the decreasein the amino acid contents bycooking, the plant food has the potential for giving high quality protein that can be exploited to enhance protein quality in human nutrition and performance in sports.