What are Time-Temperature Indicators?

Time and temperature indicator (TTI) is a new type of indicator for real-time monitoring of the safety of products such as food and medicine. It uses time or temperature to produce a cumulative effect of time and temperature through physical or chemical changes, which is used to record the temperature change history of products and indicate The remaining shelf information of the product solves the problem that the quality of the product cannot be monitored in real time caused by the traditional method of calibrating the shelf life.

In the process of commodity circulation, factors such as temperature, relative air humidity, gas, and light radiation will affect the deterioration rate of the product. Among these factors, temperature is the most difficult to regulate. The main reason for product decay is the microbial action and the catalytic action of enzymes, and the strength of the action is closely related to the storage temperature. In order to ensure the safety of food, vaccines and other products, the traditional method is to calibrate

The time and temperature indicators (TTIs) currently used are mainly divided into diffusion type, polymerization reaction type and enzyme reaction type according to the indication principle; according to the chemical principle when the indicator works, they can be divided into solution diffusion type and pH discoloration reaction type; According to the type of information transmitted, the temperature indicator can be divided into a critical temperature indicator, a critical temperature / time integrator, and a time temperature indicator.

Selection range of time temperature indicator acetylenic reagent

The conditions for the solid-phase polymerization to occur are the two packing parameters d (distance between two molecules in the crystal) and (the angle between the diyne rod and the filling axis) of the diacetylene molecule in the crystal, where d At 0.5 nm, is about 45 °. Studies have shown that as the length of the conjugated triple bond becomes longer, the reaction becomes more active, and the side chain structure plays a greater role in the polymerization process, and a more stable polymer can be obtained after the reaction.

When choosing an indicator, choose a suitable indicator according to different host products. For example, it is necessary to make the indicator match the activation energy of the main product better. At the same time, it is also desirable that the color change rate constant corresponding to the indicator reacts with the main product deterioration rate constant. Pre-polymerization or delayed polymerization occurs at low temperature (depending on whether the activation energy of the host product is higher or lower than the activation energy of the indicator material) to give the wrong color change signal; the reliability and consistency of the indicator must also be considered .

In addition, it is also expected that the indicator has low cost, low toxicity, printability, etc., and can provide sharp peaks at the end of the color change curve (thus making the color change node contrast with the colors on both sides), and have good Pigment characteristics include the ability to print smoothly and smoothly on the surface of substrates (such as labels). Different applications have different requirements for indicator properties. XRD and NMR can be used to detect the physical properties of the new acetylene reagent monomers to make them match the main product to the greatest extent.

As a result, the range of indicators available for selection has been greatly reduced. A method to expand the selection range of indicator and host product is to change the reactivity of a given acetylenic reagent monomer so that the indicator will produce different responses under specified conditions, so that a monomer can be modified according to the modified Different methods of acetylenic reagents to provide two or more color changes ^[1] .

Modification of time temperature indicator acetylenic reagent

In order to expand the selection range of indicators used in specific main products, an ice water bath can be used to dissolve a mixture of acetylenic reagents in different proportions in an acetic acid solution, and then stir to cool to 20 ° C from its boiling point (about 110-115 ° C). Commonly used solvent systems are acetic acid, propionic acid, dimethylformamide, dimethyl sulfoxide, methanol, formic acid, ethylene glycol, allyl alcohol, 2-aminoethanol, 1,1,3,3, -tetra Methyl urea, dichloroacetic acid, trifluoroacetic acid, and some solvent mixtures such as water and mixed solutions of different ratios of the above reagents. It is necessary to disperse the acetylenic reagent made into a solid particle into a liquid medium, and whether the indicator ink is transparent can be determined by controlling the size of the indicator particles ^[2] .

Application of time temperature indicator acetylene reagent

Because during the use of the indicator, it will inevitably be affected by factors other than temperature, such as ultraviolet radiation. These factors may cause premature polymerization of acetylenic monomers and cause changes in indicator color, which will affect people's judgments about whether the product is out of date. Therefore, protective measures should be taken before the indicator is prepared to reduce the influence of ultraviolet rays. One can achieve this by covering the surface of the indicator with a protective film that resists UV rays. Time and temperature indicators can be used to monitor the safety of milk, cheese, frozen burgers, tomatoes, mushrooms, seafood, frozen beef and other products in the process of transportation, storage and sales in real time. It has a more accurate indication of product quality and remaining shelf life. And predict product safety.

The different aggregation states of polydiacetylene have many different uses. The sol state is suitable for drug tracking detection in large-scale liquid drug production, and the solid or gel state polydiacetylene is more suitable for simple and extensive detection methods. The diversity of diacetylene aggregation forms provides a broad application platform for the application prospects of polydiacetylene ^[3] .