Field verification of food quality monitoring in the cold chain by using a laccase time-temperature indicator label

This study developed a laccase time-temperature indicator label (LTTIL) by immobilising laccase on electrospun fibres to form the LTTI film and reacted with guaiacol solution for colouration. Field verification was performed to validate the function of the LTTIL in monitoring food quality changes in the cold chain under temperature fluctuations. The time required to reach a total plate count of 6 log CFU/g was regarded as the critical point of fresh-cut cucumber (FCC) deterioration (CPTPC). A critical point of LTTIL colouration (CPLTTIL) was also set to indicate the significantly darker reddish brown of LTTIL. The field verification experiment revealed that when the LTTIL with 0.10 mM NaN3 was applied, the CPLTTIL was attained at 132.8 hr after the start of an experiment, whereas the CPTPC was attained at 139.2 hr, resulting in a low prediction error of approximately 4.6%. Therefore, the LTTIL is considered to be effectively used to monitor FCC quality changes in the cold chain and accurately evaluate their freshness.