Development of a Prototype of Lactic Acid-Based Time-Temperature Indicator for Monitoring the Fresh Produce Quality

摘要

Temperature is a crucial factor affecting the quality and safety of food products during both distributionand storage. The difficulty in controlling and monitoring the temperature history of food productsmakes it difficult to precisely predict shelf life. Time-temperature indicators (TTIs) provide a visual summaryof a product's accumulated chill-chain history, recording the effect of both time and temperature. Attemptshave been made to develop a prototype of time temperature indicator based on the diffusion of lactic acid,which is temperature dependent. Four lactic acid-based TTIs were made in different substrate concentrations.Color changes associated with the diffusion of lactic acid were monitored. In a vapor diffusion of lactic acid,an irreversible color change of a chemical chromatic indicator (from green to red) clearly and progressivelyoccurred due to the pH reduction. The temperature dependencee TTIs kinetics was characterized isothermallyin the rang of 4-45 °C, yielding the activation energy (Ea) of approximately 50 kJ mol-1. The mathematicalmodels of each TTI were established according to the relationships between color changes andtime and temperature. The difference between the Ea's of the TTIs and the Ea of fresh produce quality lossesin association with respiration rate was less than 5 kJ mol-1 and therefore these TTIs could be used to monitorfresh produce quality losses. It could be applied to show the time-temperature history of fresh produces and toindicate fresh produce quality associated with time-temperature exposure.