# Characterization of Grape Extract-Colored SiO2 Synthesized via the Sol-Gel Method  
[PERSON]  
1 Department of Engineering, University of Campania \"[PERSON]\", Via Roma n. 29, 81031 Aversa, Italy; [EMAIL_ADDRESS] (M.F.) [EMAIL_ADDRESS] (A.D.); [EMAIL_ADDRESS] (L.V) 1  
[PERSON]  
1 Department of Engineering, University of Campania \"[PERSON]\", Via Roma n. 29, 81031 Aversa, Italy; [EMAIL_ADDRESS] (M.F.) [EMAIL_ADDRESS] (A.D.); [EMAIL_ADDRESS] (L.V) 1  
[PERSON]  
1 Department of Engineering, University of Campania \"[PERSON]\", Via Roma n. 29, 81031 Aversa, Italy; [EMAIL_ADDRESS] (M.F.) [EMAIL_ADDRESS] (A.D.); [EMAIL_ADDRESS] (L.V) 1  
[PERSON]  
2 Department of Environmental, Biological, and Pharmaceutical Sciences and Technologies, University of Campania \"[PERSON]\", Via Vivaldi 43, 81100 Caserta, Italy; [EMAIL_ADDRESS] 2  
[PERSON]  
1 Department of Engineering, University of Campania \"[PERSON]\", Via Roma n. 29, 81031 Aversa, Italy; [EMAIL_ADDRESS] (M.F.) [EMAIL_ADDRESS] (A.D.); [EMAIL_ADDRESS] (L.V) 1  
food packaging, glass plays a key role in preserving the freshness of products, thereby extending their shelf life. This is because glass is completely inert; it does not chemically interact with the contents it holds, and therefore, it does not alter the organoleptic characteristics of the food or its quality [11]. Interestingly, glass-based materials could be used for active packaging if prepared as hybrids in which bioactive or functional molecules are interacting with or chemically bonded to the inorganic phase [12; 13]. Glass-based hybrids can be prepared by the sol-gel route, which involves water hydrolysis and water/alcohol polycondensation reactions [14; 15; 16] (see the SN\({}_{2}\) mechanism type shown in Figure S1, using tetraethyl orthosilicate or TEOS as a precursor) to convert a solution into a solid gel matrix. It offers precise control over the structure and composition of the materials, resulting in the development of hybrid glasses with the desired properties. Working at room temperature helps to maintain the bioactivity of the organic molecules without compromising their properties. Acid and base catalysts can even have a major impact on the sol-gel process, influencing reaction rate, gel architecture, and the final properties of the synthesized material. They also fundamentally shape the properties of the resulting gel [17]. This technique could be easily coupled with others, such as dip-coating, to produce thin films on the surfaces to be functionalized [18; 19]. This work presents a preliminary study on the development of glass-based hybrid materials capable of releasing bioactive molecules for food packaging applications. Unlike other scientific publications that primarily focus on materials for active packaging based on plastic-like polymers such as Polypropylene, Polystyrene, Polyethylene Terephthalate (PET), and Polyamide [5; 20], this work proposes an innovative approach based on the use of glass. In the scientific literature, glass is predominantly described as a physical barrier against oxygen and contaminants [21]. However, its potential active role in packaging has not been explored. In this study, glass is utilized not only as a physical barrier but also as a functional material capable of playing an active role in food preservation through the controlled release of bioactive molecules from plant extracts. In this scenario, grape extract (GRE) was used as a bioactive source, as it is rich in polyphenols, particularly flavonoids and anthocyanins, with antioxidant activity that can extend the shelf life of food products and beverages [22]. Furthermore, anthocyanins can impart a natural color to the matrix in which they are incorporated [23]. Typically, metal oxides are used to color glass-based packaging [24]. However, their synthesis process relies on non-renewable resources. On the contrary, there are several coloring molecules from natural renewable sources that could be used instead of mineral types.