Background: Monodora myristica (Gaertn.) Dunal is a useful but underutilised tropical tree of the Annona- ceae or custard apple family of flowering plants which is rich in proteins. The objective of this study was to evaluate the effect of thermal processing on the protein quality of Monodora myristica (Gaertn.) Dunal seeds.
Methods: Raw, boiled (10, 20, 30 min) and roasted (10, 20, 30 min) Monodora myristica seeds were defatted, and the effect of heat treatment on their crude protein, amino acid composition/concen- tration and protein quality parameters was investigated.
Results: The results showed that crude protein was significantly reduced by heat treatment and ranged between 19.92–23.32%. Essential amino acids of the samples ranged from 26.34–34.06%. Glutamic acid (14.58 g/100 g), aspartic acid (9.18 g/100 g), leucine (7.76 g/100 g) and lysine (6.91 g/100 g) were the most predominant amino acids, while methionine + cysteine was the first limiting amino acid. There were some increases in some of the amino acids in the roasted samples. For instance, lysine was increased by 3.3% and arginine by 6.9%. The predicted protein efficiency ratio at all levels of processing was higher than 1.50, below which a protein is taken to be of poor quality. The calculated biological value ranged from 70.7% to 77.7%. Based on The Provisional Amino Acid (Egg) Scoring Pattern, the percentage adequacy of most essential amino acids in the samples was high.
Conclusions: Despite the decrease in most amino acid contents by cooking, the plant food has the potential to provide high quality protein which can be exploited to enhance protein quality in human nutrition and performance in sports.
Keywords: Monodora myristica; amino acid composition; amino acid score; protein efficiency ratio.