A study was undertaken to investigate the influence of protein concentration and the addition of different doses of endopeptidase (Alcalase) and exopeptidase (Flavourzyme) on the sequential enzymatic hydrolysis of a protein concentrate obtained from defatted sunflower wholemeal. The results show that the greatest degree of hydrolysis (37.8%) is achieved by hydrolyzing an aqueous substrate with a 5% protein concentrate, and using a 0.02 g Alcalase/g of protein concentrate of the substrate. The aminograms performed reveal that the free amino acid found in the highest proportion in the hydrolysate was aspartic acid, which accounted for over 50% of the free amino acids present, regardless of the substrate concentration and the enzyme dosage used. Finally, the hydrolysate obtained from a substrate containing a 5% protein concentrate and a 0.02 g Alcalase/g of protein concentrate displayed characteristics that indicate its suitability for use as a vegetable-origin plant growth regulator. (c) 2007 Elsevier Ltd. All rights reserved.