This study evaluated the nutritional qualities of a protein concentrate and an isolate produced from cashew nut. The nutritional qualities were evaluated by determining amino-acid composition, in vitro digestibility and anti-nutritional factors (tannins, trypsin inhibitor activity-TIA and phytic acid content) in the protein concentrate and isolate using standard analytical methods. The amino-acid with the highest concentration in defatted cashew nut powder (DCNP), cashew nut protein concentrates (CNPC), and cashew nut protein isolate (CNPI) was glutamic acid, which was found to be 22.5, 21.38, and 21.81 g/100 g, respectively. This was followed by leucine, aspartic acid and arginine, in that order. The amino-acid with the lowest concentration in DCNP, CNPC, and CNPI was cysteine. The sulphur-containing amino-acids and some other essential amino-acids (lysine, tryptophan, leucine, isoleucine, and tyrosine) in CNPI were not significantly different (p>0.05) from that of DCNP, but were significantly different from that of CNPC (p<0.05). CNPC and CNPI were rich in essential amino-acids, and based on the FAO/WHO recommended essential amino-acids pattern requirements for an infant, the limiting amino-acid in CNPC, and CNPI was lysine with chemical scores of 0.68, and 0.63 respectively. However, the anti-nutritional factors (tannins, TIA, and phytic acid contents) of CNPI were found to be lower than those in DCNP and CNPC, while those of CNPI and CNPC were within the range found in the commercial peanut and soy protein concentrates and isolates. The highest in vitro digestibility was observed in CNPI (95.30%), while CNPC (87.83%) had a higher value than DCNP (79.93%). The nutritional qualities of the protein concentrate and isolate from cashew nut were found to be comparable to those reported for commercial peanut and soy protein concentrates and isolates. Therefore, the cashew nut products could be suitable as additional source of protein ingredients in food formulations.
Key words: Cashew, protein, nutrition, isolate, concentrate.