Insights into acrylamide formation in table olives

Acrylamide formation and its precursors in green and naturally black table olives were investigated. The formation from the lipophilic phase via acrolein and the molecular size of aqueous precursors were studied in more detail using LC–MS/MS, preparative HPLC, and ultrafiltration. Acrylamide levels increased in green (33–292 μg kg -1 ) and naturally black table olives (21–478 μg kg -1 ), depending on heating time, with no significant differences between defatted and non-defatted samples. Acrolein content rose with heating time but did not correlate with acrylamide levels, showing the lipophilic phase and acrolein did not significantly influence acrylamide formation. When aqueous olive extracts were ultrafiltrated with a cut-off <10 kDa, lower acrylamide contents were observed in filtrates after heating than in untreated extracts (19–45%). In most cases, acrylamide formation was further reduced with smaller cut-offs (5, 3, and 2 kDa). Thus, acrylamide formation in table olives involves multiple precursors of varying molecular sizes, with significant contributions from components >10 kDa and 5–10 kDa. After separating aqueous olive extracts by preparative HPLC, acrylamide was detected in several fractions after heating, showing that precursors also vary in polarity. Smaller components (<10 kDa) were more prevalent in early polar fractions, while larger components (>10 kDa) significantly contributed to acrylamide formation in later fractions. Trypsin digestion before heating drastically reduced acrylamide levels (97–98%), emphasizing the importance of proteins for acrylamide formation in olives. • Acrolein does not correlate with acrylamide in green and naturally black olives • Acrylamide formation does not occur from the lipophilic phase • Acrylamide formation involves multiple precursors varying in molecular size • Trypsin digestion significantly reduced acrylamide formation • A structure element of peptides or proteins was suggested as a possible precursor