Guava seed protein isolate: Functional and nutritional characterization

A protein isolate from the guava seed meal (Psidium guajava) was obtained by use of isoelectric precipitation, with 78% extraction yield (extracted protein to that in raw material) and 96.7% protein content of the product. Protein solubilization was done at pH 11.5 and 40C for 30 min, followed by precipitation at its isoelectric point (pH 5). Solubility of the isolate was minimal at pH 4 to 6, and increased below pH 4 and above pH 6. Emulsifying capacity and stability of the emulsion was maximum at pH 8. However, the water and oil absorption capacity, as well as the foaming capacity and foam stability, were relatively low. The essential amino acid profile of the guava seed protein isolate, except for lysine content, is above that proposed in the FAO/WHO pattern for adults. The isolate is also an important source of tryptophan. Its in-vitro protein digestibility was higher than for soybean isolate.