A polydiacetylene-based colorimetric sensor as an active use-by date indicator for milk.

Area of Science:

• Materials Science
• Food Science
• Analytical Chemistry

Background:

• Current food date labels are inadequate, contributing to significant food waste.
• Existing methods lack real-time monitoring of food spoilage indicators.
• Human health risks arise from consuming spoiled food due to unreliable shelf-life assessments.

Purpose of the Study:

• To develop a novel polydiacetylene/zinc oxide (PDA/ZnO) colorimetric sensor for real-time milk freshness detection.
• To engineer a sensor system capable of monitoring pH changes indicative of bacterial spoilage.
• To enhance sensor sensitivity and stability for practical food applications.

Main Methods:

• Fabrication of a PDA/ZnO nanocomposite sensor.
• Tuning sensor sensitivity by selecting diacetylene monomers and functional group relocation.
• Exploring lipid doping and pre-exposure stabilization techniques for the sensor.
• Utilizing lactic acid concentration and pH changes to trigger colorimetric responses.

Main Results:

• The PDA/ZnO sensor successfully indicates milk freshness through a blue to purple to red color change corresponding to pH shifts.
• Sensors constructed with 5,7-hexadecadiynoic acid (HDDA) and ZnO demonstrated clear discrimination between fresh, spoiling, and spoiled milk.
• A novel stabilization method involving pre-exposure to the food matrix improved the sensor's chromatic stability in food environments.

Conclusions:

• The developed PDA/ZnO sensor provides a reliable, real-time method for assessing milk freshness.
• This technology has the potential to significantly reduce food waste and enhance food safety.
• Further optimization of PDA/ZnO sensors could lead to broader applications in food quality monitoring.