Chemical marker M2 (4-hydroxy-5-methyl-3(2H)-furanone) formation in egg white gel model for heating pattern determination of microwave-assisted pasteurization processing

• Studied the formation of chemical marker M2 in egg white gel models at various pasteurization time-temperatures combinations.
• M2 yield negatively correlated with the egg white gel model color parameters L∗ and G values.
• Salt addition (up to 200 mM) has no effect on the M2 formation.
• The retention rate of M2 during storage decreased with storage time and temperature.
• M2 in egg white gel can be used for heating pattern determination in microwave-assisted thermal pasteurization processing.

Microwave-assisted pasteurization (MAP) is a potential thermal processing technology in which the non-uniform heating presents a challenge. This study evaluated the application of a chemical marker M2 (4-hydroxy-5-methyl-3(2H)-furanone) in an egg white gel model on the determination of possible heating patterns in prepackaged foods during MAP processing. The gel model samples were prepared by heating a homogeneous liquid egg white mixture (25% egg white, 1% D-ribose, 0.5% L-lysine) at 70 °C for 30 min. The chemical marker M2 formation was studied by heating the gel model samples in 75, 80, 85, 90, 95, and 100 °C oil bath for 5, 10, 15, 20, and 30 min. The marker yields were determined using high-performance liquid chromatography (HPLC). The color values of the heat-treated samples were measured using CIE L∗a∗b∗ and RGB models. The stability of M2 was evaluated at storage temperatures of 4 and 22 °C for 1, 3, 5, and 9 days. In order to validate the application of the new gel model system, the heating patterns of the gel models and marker yields of samples taken from 5 different locations of the MAP-processed gel models at 75 and 100 °C were analyzed. Results showed that the M2 formation in egg white increased linearly with heat treatment time at 75–95 °C, while a slight concavity was observed for samples treated at 100 °C. Color parameters L∗ and G values were found to be significantly correlated with the heating temperatures. During storage, the M2 retention rate decreased with increasing time and temperature, while samples treated for longer times were more stable. Salt addition had no significant effect on the M2 yield within the studied time-temperature combination. The color change of egg white gel models due to different M2 yield after the MAP process could be clearly recognized using a computer vision method.