Protein oxidation and proteolysis during storage and in vitro digestion of pork and beef patties

• Oxidation and proteolysis were measured during storage and digestion of meat.
• Protein oxidation was assessed as thiol oxidation, carbonylation and hydroxylation.
• 4-Hydroxyphenylalanine is a new protein oxidation marker in meat.
• Protein oxidation before digestion impairs proteolysis in the proximal gut.

The effect of protein oxidation on proteolysis during meat digestion was investigated following storage and subsequent in vitro digestion of beef and pork patties. Protein oxidation was evaluated as thiol oxidation, total carbonylation, and specific carbonylation (α-amino adipic and γ-glutamic semialdehyde). Furthermore, 4-hydroxyphenylalanine, a hydroxylation product of phenylalanine, was identified and quantified as a new protein oxidation marker. After 7 days of chilled illuminated storage (4 °C), significant oxidative modifications were quantified and the oxidative degradation was continued during in vitro digestion. The observed effects were more abundant in beef patties. Protein oxidation before digestion resulted in impaired proteolysis during digestion.