Investigations into acrylamide precursors in sterilized table olives: Evidence of a peptic fraction being responsible for acrylamide formation

•Acrylamide formation from Ala, Asp and Met containing peptides without carbonyl compound.•Only heated olive water fractions containing peptides/proteins generate significant acrylamide.•No detection after heating the same fractions when previously subjected to acid hydrolysis.•Peptides (<10,000 Da) as precursors of acrylamide formation in sterilized olives.

Formation of acrylamide from commercial model peptides containing protein-bound aspartic acid, alanine and methionine, respectively, at 200 °C and different times in the absence of any carbonyl sources, was demonstrated by HPLC–MS/MS analyses. Further experiments using a more complex model system based on olive water, i.e., the aqueous fraction of olive pulp from untreated and lye-treated green olives, were performed. After partial fractionation of olive water by solid-phase extraction, only peptides/proteins containing fractions, being devoid of free asparagine, generated significant amounts of acrylamide during less harsh heat treatment (121 °C for 30 min). In contrast, acrylamide was not detected after heating the same fraction under identical thermal conditions when previously subjected to acid hydrolysis. Consistently, significant amounts of acrylamide were released after heating the albuminous precipitate resulting from acetone precipitation of olive water. These results strongly support the role of peptides/proteins as precursors of acrylamide formation in sterilized olives.