## 1 Introduction  
Fresh food goods can rapidly deteriorate due to the physical damage that might be sustained during the processes brought on by chemical reactions, enzyme activity, and microbial contamination [1]. The development of new packaging solutions is a result of the development of packaging technology in response to consumer expectations for food products that are fresh, safe, and of exceptional quality [2; 3]. Food waste and food degradation can be prevented by using packaging as a storefront for information about the food's condition. Packaging can also actively contribute to the preservation of food. In this regard, research and development are underway on active and intelligent packaging [1]. Bioactive substances, such as antimicrobials [4] and antioxidants [5], are present in active food-packaging materials to increase the shelf lives of, preserve the quality of, and stabilize food-packaged commodities [6]. Furthermore, intelligent food-packaging solutions are designed to monitor the environment or the conditions of the food, identify any physical, chemical, or biological changes, and take appropriate action. The intended outcome is to quickly evaluate food quality [7; 8; 9]. There are three categories of intelligent sensor-based packaging material: freshness, time-temperature, and gas. These materials can be used to track inaccuracies in temperature changes along the supply chain, modifications in the gas composition in food packing,and the deterioration of freshness due to variations in the amount of metabolites, which are indicative of microbial growth [3; 10]. The most widely used freshness indicators include a stable base and a dye that responds to pH variations by changing color and providing a visual response to the environment inside the package [3; 7]. Numerous studies have examined different synthetic dyes as pH indicators [11; 12; 13], but the leaching of the dye and consumer awareness of chemically manufactured dyes' negative effects raises questions due to their toxicity and bioaccumulation [3; 7; 14]. Due to their biodegradability, lack of toxicity, lack of carcinogenicity, and ecologically benign manufacturing process, natural dyes derived from a variety of sources are potential options [15; 16]. The red naphthoquinone pigment, shikonin, from the roots of gromwell, is one example of a natural pigment used in colorimetric indicator systems. Other examples include anthocyanins from barberry (_Berberis vulgaris_ L.), black carrots (_Daucus carota_ L.), saffron (_Crocus sativus_ L.), red cabbage (_Brassica oleraceae_), and saffron [8; 9; 17; 18]. Sappan wood (_Caesalpinia sapan_ L.) is naturally present across Asia, including Thailand, China, and Japan. Due to its many beneficial uses, this wood plant is now grown in several parts of the world, including Africa, Europe, North America, and South America. Since the wood is inexpensive and lacks a distinct flavor, it has the potential to be utilized as a natural red dye, as opposed to a synthetic dye [19]. The main active ingredient in sapan is brazilein, a white phenolic compound with two aromatic rings: one pyrone, and one five-membered ring. However, the brazilein structure's hydroxyl group is simply oxidized. It can transition into a carbonyl group, resulting in a structural alteration and the production of the vibrant chemical, brazilein. Brazilian is a polyphenolic chemical; hence, changes in pH are likely to cause the hydroxyl group in its molecule to change color [20; 21]. In addition to brazilein, _C. sapan_ is also thought to be a possible source of anthocyanins. These natural compounds may be candidates to replace synthetic dyes due to their attractive, vibrant hues (orange, red, and purple), which fade quickly when exposed to light, oxygen, high temperatures, pH, salt stress, and enzymes [22]. The incorporation of biopolymers in active packaging has attracted the attention of numerous researchers. These biopolymers include the units created by a covalent peptide link, proteins [23].