With the aim of meeting the growing demand for safe food, intelligent packaging has emerged, which monitors the conditions of the food and informs the consumer about its quality directly at the time of purchase. Among intelligent packaging options, colorimetric indicator films, which change color in response to changes in the food, such as the release of volatile compounds, have been widely studied. Among them, pH indicator films composed of dyes sensitive to small variations in the pH value of the food surface have received greater attention in recent years. Anthocyanins, which are natural pigments, have stood out as one of the most commonly used sources of dyes in the production of these indicator films. In this context, the present review aims to present an updated overview of research employing anthocyanins in indicator films, including their stability under different storage conditions, the influence of different polymers used in their production, and alternative techniques for maintaining stability.

Oral film (OF) research has intensified due to the effortless administration and advantages related to absorption in systemic circulation. Chitosan is one of the polymers widely used in the production of OFs; however, studies evaluating the maintenance of the active principles’ activity are incipient. Propolis has been widely used as an active compound due to its different actions. Printing techniques to incorporate propolis in OFs prove to be efficient. The objective of the present study is to develop and characterize oral films based on chitosan and propolis using printing techniques and to evaluate the main activities of the extract incorporated into the polymeric matrix. The OFs were characterized in relation to the structure using scanning and atomic force electron microscopy; the mechanical properties, disintegration time, wettability, and stability of antioxidant activity were evaluated. The ethanolic extract of green propolis (GPEE) concentration influenced the properties of the OFs. The stability (phenolic compounds and antioxidant activity) was reduced in the first 20 days, and after this period, it remained constant.

Intelligent films (IFs) incorporating natural colorants and biodegradable materials offer innovative solutions for monitoring food freshness and spoilage. This study evaluated the impact of varying the PVA-APN ratio on films formulated with Peruvian Purple Potato starch (APN) and anthocyanin extract (AE). The research focused on the effects of PVA on physicochemical and mechanical characteristics, as well as the color changes observed when the films were used with seafood. The results indicated a decrease in chroma a* and an increase in chroma b* when the films were in contact with different buffer solutions (from acidic to alkaline). Solubility decreased with higher starch concentrations and the mechanical properties revealed a reduced tensile strength and elongation with increased APN concentration. The films effectively indicated freshness, with the best ΔE values for the 50:50 formulations (13.6 ± 1.6 and 12.04 ± 2.8 for fish and shrimp, respectively), making them promising candidates for intelligent seafood packaging.