A pH-Sensitive Intelligent Packaging Film Harnessing Anthocyanin for Food Freshness Monitoring

In recent years, there has been a growing interest in advanced packaging films made from natural polymers. These films are integrated with pH-sensitive dyes, aiming to monitor the freshness of food. Specifically, the development of pH-adaptive intelligent packaging films, known as MC 5 /ZA 5 -Anth 3% , involves using methylcellulose (MC) and zinc alginate (ZA) as the foundational materials, with anthocyanins (Anth) serving as the freshness indicators. The production of MC 5 /ZA 5 -Anth 3% films has resulted in improved thermal stability, mechanical properties and water resistance, alongside a reduction in the transmission of ultraviolet–visible (UV–vis) light through the material. Importantly, these color-changing films undergo a noticeable change in color when subjected to pH changes or exposure to ammonia gas, making them suitable for detecting shifts in the pH of foods like pork and shrimp, the presence of volatile nitrogen compounds, and early signs of food degradation. Upon exposure to varying pH buffers, the color indicator film underwent a noticeable transition from a reddish-pink hue to blue, ultimately shifting to blue-green. Consequently, this pH-sensitive color indicator film emerges as a viable candidate for the smart, real-time monitoring of freshness in perishable foods such as pork and shrimp.