Principle, development and application of time–temperature indicators for packaging

Time–temperature indicators (TTIs) can visually reflect the remaining shelf life of various products, especially in cold chain transportation, by taking consideration of both time and temperature influences. Though various TTIs have been developed, few have been commercialized. This review aims at providing a timely reference to scientific community and valuable guidance for the future design of TTIs to boost the commercialization. This review firstly introduces the general principle and models for TTIs including key parameters of reaction rate constants, activation energies and activation energy matching. Then, four classical types of TTIs covering diffusion‐based, polymer‐based, enzyme‐based, and microbial TTIs are introduced regarding their working mechanisms, advantages and disadvantages as well as commercialized TTI products as examples. The development trend of TTI design and fabrication is highlighted from three categories including nanoparticles, electrospun nanofibers and printable inks. Furthermore, the review summarizes recent application of TTIs for monitoring the quality and safety of various products (meat, seafood, dairy, vaccines and fruits and vegetables). We also point our concerns from the perspective of safety, accuracy, multifunctionality and commercialization for the future development of TTIs.