Amino and organic acids of the prickly pear cactus (Opuntia ficus indica L.)

The amino acids of prickly pear (Opuntia ficus indica L.) proteins, free amino acids and nonvolatile organic acids were determined on fresh and lyophilised young pads. The calculated biological value of prickly pear protein was 72.6, relative to egg protein. Trace amounts of malonic, malic and citric acids in material collected at 1800 hours; traces 0.95 and 0.31 mg g^?1, respectively. In similar material analysed at 0600 hours, the concentrations of those acids were 0.36, 9.85, and 1.78 mg g^?1, respectively. Since there was a significant accumulation of the acids during the evening, crassulacean-type metabolism is suggested.