AbstractThe optimum conditions were determined for the preparation of protein isolates from ground, defatted guava seed flour. The isolates were obtained by micellisation and isoelectric precipitation techniques. The isoelectric point of guava seed protein was found to be pH 4.5 with a protein solubility of more than 85% above pH 9. Using 40–80 mesh particle size and extracting at pH 10 for 30 min, an isoelectric isolate was obtained by acidification to pH 4.5 which was 85.4% of the starting protein compared to 18.3% for micellisation protein obtained by twofold dilution with cold distilled water of 5% NaCl protein extract. The isolates were easily digested by the pepsin‐pancreatin enzyme system and were comparable to casein. The amino acid composition showed that guava seed flour and isolates were deficient in sulphur‐containing amino acids and in lysine, but contained the other essential amino acids in adequate levels. The micellisation isolate had higher fat absorption and emulsion stability than the isoelectric isolate, while other functional properties were almost si