The widespread use of petroleum-based plastic packaging has become a major global concern due to its environmental impact, as it is difficult to degrade and often contains harmful chemicals. To address this issue, green biodegradable packaging made from polysaccharides and proteins is emerging as a promising alternative to petroleum-based plastics (Alizadeh-Sani et al., 2020). At present, food packaging has gone beyond basic optical, mechanical, and biodegradable properties. On the other hand, the high nutrient content inherent in food, coupled with the presence of water and oxygen, creates an ideal environment for microbial proliferation, leading to spoilage. The assurance of food quality and safety remains a major concern in the food industry. The development of smart packaging systems, comprising both active and intelligent functionalities, represents a practical strategy to both enhance shelf life and enable continuous monitoring of food freshness (Guo et al., 2024; Li, Lei, et al., 2023).

Essential oils, hydrophobic active compounds derived from plants, are particularly valued for their strong antibacterial and antioxidant properties (Miao et al., 2024). Additionally, incorporating hydrophobic substances into the hydrophilic matrix is an effective strategy to improve its water vapor barrier properties (Farahani et al., 2025; Luo et al., 2022). However, adding hydrophobic substances directly to the hydrophilic matrix often leads to poor miscibility between the two phases during film formation, resulting in phase separation. Traditional emulsions are generally stabilized by abundant molecular emulsifiers adsorbed onto the oil-water interface. These emulsifiers can desorb from the interface under the impetus of thermal motion, a phenomenon that may subsequently trigger polymerization or phase separation within the emulsified system (Zhao et al., 2024). Furthermore, incorporating hydrophobic essential oils into hydrophilic polysaccharide matrices could result in partial phase separation under certain processing or storage conditions. Pickering emulsion, a novel system stabilized by solid particles adsorbed at the oil-water interface, offers a solution to this challenge while avoiding the potential health risks associated with surfactants. This method ensures a uniform and stable distribution of essential oils within the film matrix, effectively overcoming compatibility issues and improving the retention rate of hydrophobic essential oils (Zhao et al., 2024). Notably, solid particles play a crucial role in preparing stable emulsions. In recent years, Gel has been employed as a stabilizer in emulsion. However, challenges such as aggregation, flocculation, and phase separation remain. Studies have shown that protein/polysaccharide complexes formed through electrostatic interactions exhibit excellent emulsification properties (Li, Hu, et al., 2024). Protein-polysaccharide hybrid particles are more suitable for stabilizing Pickering emulsions. Protein-polysaccharide hybrid particles combined the respective advantages and synergistic effects of sole particle. It has been reported that Pickering emulsions prepared using soy protein isolate-cellulose nanofiber hybrid particles exhibited outstanding stability (Liu, Lin, et al., 2022; Zhao et al., 2024). Protein-nanocellulose particles have also been shown to improve emulsion stability by modifying electrostatic interactions (Feng et al., 2023). Adjusting the pH of the solution could induce the formation of electrostatic complexes, which regulate the binding state and wettability of the complex by altering surface charge (Niu et al., 2022). This, in turn, enhances interfacial properties and emulsion stability. Therefore, constructing a Gel-cellulose network skeleton through pH adjustment may be an effective strategy for stabilizing essential oil emulsions.

Currently, fresh meat and aquatic products often utilize colorimetric indicators, such as pH-sensitive dyes, to monitor freshness and provide consumers with visual information about packaged foods (Lin et al., 2023; Shiryanpour et al., 2025). Curcumin (Cur), a bioactive small molecule, exhibits various pharmacological effects, including anti-cancer, anti-inflammatory, and antibacterial properties (Wu et al., 2025). In addition, Cur suffers from poor water solubility, high susceptibility to decomposition, and marked sensitivity to light, temperature, and ultraviolet radiation. However, the color change of curcumin may not be noticeable in environments with a pH below 9, which limits its application in food packaging. (Hu et al., 2019). When combined with anthocyanins (Ant), this dye was found to exhibit enhanced pH sensitivity and a broader color response range (Zhang, Zhang, et al., 2024). Ant, natural polyphenol pigments, are widely recognized for their pH-responsive properties, exceptional antioxidant activity, and health benefits (Choubaki et al., 2025; Xiong et al., 2024). However, Ant face challenges related to stability, as external factors such as pH, temperature, light, oxygen, solvents, and humidity strongly affect their performance. Co-pigmentation, oxygen exclusion, and encapsulation are effective approaches to stabilize Ant (Xiong et al., 2024). Studies have shown that combining Cur and Ant as copigment color indicators enhances their sensitivity to meat and seafood freshness compared to individual pigments (Chen et al., 2020; Zhou et al., 2021). Specifically, Cur exhibits higher degree of deprotonation and enhanced color-change sensitivity under alkaline conditions. In contrast, Ant shows greater stability in acidic environments, primarily due to the inherent instability of its chalcone form. Thus, the combination of these two compounds may enable more effective exertion of their respective responsive indicator functions across distinct acidic and alkaline conditions (Erna et al., 2022; Guo et al., 2024). Here, we intend to mix two natural pigments and introduce them into the konjac glucomannan (Kgm) system together with Pickering emulsion to improve the intelligent responsiveness. It was found that the indicator film containing Cur-coated Pickering emulsion showed excellent freshness monitoring performance and extended shelf life of basa fish during storage (Miao et al., 2024). A composite film combining oxidized cellulose nanofiber-stabilized cinnamon oil Pickering emulsion and Cur within a Gel/chitosan matrix exhibited great active and intelligent properties (Liu, Li, et al., 2022). Additionally, lignocellulosic nanofibril/Cur Pickering emulsions have been reported to enhance Cur stability, enable pH-responsive color changes, and produce composite films with UV shielding, mechanical strength, oxygen barrier properties, and antioxidant activity. These films have shown potential as real-time freshness indicators for shrimp (Xu et al., 2024). Furthermore, adding oxidized mulberry extract to cinnamon essential oil-based Pickering emulsions imparted excellent antibacterial and antioxidant activity to collagen films through the sustained release of active substances, offering promising applications for fish preservation and freshness indicators (Ran et al., 2024).

In summary, the design of a stable Pickering emulsion system combined with dual natural pigments represents an innovative strategy for enhancing film indication stability, sensitivity and contrast, contributing to the advancement of smart packaging. Moreover, the migration of essential oils and pigments exerts no adverse effects on the flavor and odor of the final product, with all migration concentrations complying with the relevant regulatory standards. This study aims to innovatively develop an active and intelligent packaging for preservation and freshness indicators. Here, Ant and Cur were introduced as co-pigments and functional components, while thyme essential oil Pickering emulsion (GCTEO) stabilized by Gel and CNC composite colloidal particles (G-CNC) was incorporated into Kgm matrix. We hypothesize that four key advantages are proposed: (i) A relatively eco-friendly preparation: The composite colloidal particles were prepared using pH-induced electrostatic interactions; (ii) Enhanced functional properties: The Pickering emulsion loaded with thyme essential oil (TEO) synergizes with the inherent antibacterial and antioxidant activities of Ant and Cur, effectively enhancing these properties and maintaining the freshness of fruits. (iii) Improved indicator performance: The composite pigment-emulsion system enhances the stability and rapid responsiveness of the color indicator. The expanded pH response range allows for effective monitoring of the freshness of yogurt and seafood; (iv) Enhanced material properties: The composite film demonstrated excellent mechanical properties, light-blocking and water vapor/oxygen barrier performance, thermal stability, and enhanced hydrophobicity. This study highlights the potential of pigment-emulsion system to create innovative, multifunctional smart packaging.