# UV-Induced Aging in Thermochromic Pigment-Integrated Food-Grade Polymers: A Performance Assessment  
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lightweight [7]. However, concerns exist over its sustainability [8]. In addition, there has been a push for packaging that can prolong the shelf life of food [9]. Thermochromic materials belong to a class of chromogenic substances that exhibit color shifts in reaction to specific external stimuli such as temperature (thermochromism), light (photochromism), or electricity (electrochromism) [10]. Among these, thermochromic systems--particularly those based on leuco dyes or liquid crystals--have gained traction in food packaging due to their responsiveness to subtle temperature changes and ability to communicate spoilage risk visually [11]. The color-changing properties of thermochromic pigment (TP) masterbatches, when added to polymer matrices, make them suitable for rigid and flexible packaging across a broad spectrum of polymer materials and forming processes [12]. Applications such as dairy products, frozen dinners, and pre-cooked meals--where temperature sensitivity is crucial--can particularly benefit from the use of TPs [13]. Real-world applications of thermochromic pigments in packaging include temperature-sensitive time-temperature indicators (TTIs) for dairy [14] and meat products [15], freshness indicators that respond to cumulative heat exposure in seafood packaging [16], and irreversible cold chain monitors for frozen goods [17]. These intelligent systems visually signal temperature abuse, spoilage risk, or compromised storage conditions, enhancing food safety and consumer confidence. Although thermochromic polymers are innovative, their environmental resilience is inherently limited [18]. Ultraviolet (UV) radiation can degrade organic materials through photochemical processes, leading to chain scission, oxidation, discoloration, and a loss of mechanical properties in polymers [19]. When TPs are exposed to UV radiation, the thermochromic phase transition may deteriorate, dye fading may occur, and encapsulation integrity may be compromised [20]. This is particularly troublesome in food packaging applications where thermochromic indicators must remain visible to consumers and functional throughout the product's shelf life [21]. Many TP formulations use microencapsulated leuco dyes that are especially sensitive to photodegradation, which can be triggered even under moderate UV levels found in indoor lighting or direct sunlight [22]. There are several restrictions on the use of TPs in food contact packaging applications. In addition to maintaining optical clarity, preventing chemical component migration into food, and complying with safety regulations, these materials must demonstrate precise and reversible thermochromic activity [23]. Repeated exposure cycles to light [24], temperature fluctuations [25], and mechanical stress [26] can gradually decrease TP performance. Additionally, there are more significant restrictions on the types of polymers and additives that can be used with thermochromic systems, as packaging materials are increasingly being made to be recyclable or biodegradable [27]. As a result, there is a growing need for rigorous evaluation of the environmental stability of thermochromic polymers under realistic operating conditions. Regulatory acceptance of thermochromic pigments in food contact plastics remains limited across jurisdictions. In the European Union, these materials fall under Regulation (EC) No. 1935/2004 [28] and Commission Regulation (EU) No. 10/2011 [29], requiring all components--including pigments and encapsulants--to be either authorized substances or proven to comply with migration and toxicological safety criteria. In the United States, components must be approved under relevant FDA 21 CFR sections or through Food Contact Notifications (FCNs).