## 1 Introduction  
The development of novel \"functional foods\" is a great opportunity to improve the quality of foods available to consumers to benefit their health and well-being in most modern societies. Indeed, the European Union (EU) is fighting diseases characteristic of a modern age, such as obesity, osteoporosis, cancer, diabetes, allergies, and dental problems [1]. A food can be regarded as functional if, beyond its inherent nutritional effects, it does satisfactorily demonstrate to provide added physiologic benefits (e.g., reduction of chronic disease risk) [2]. Currently, the majority of commercial functional foods are presented with the bioactive components contained within compatible foods. However, this aspect imposes to the food industry a number of limitations and difficulties during processing and storage such as the loss of product functionality, the development of undesirable flavors, or the modification of the food product texture [3]. The functional, or more precisely, \"bioactive packaging\" concept, is based on the incorporation into the packaging structure of the desired bioactive principles in optimum conditions until their eventual release into the food product either through controlled or fast release during storage, or just before consumption, taking into account the specific product/functional substance characteristics or requirements [4]. Indeed, the so-called bioactive packaging differs from the well-known active packaging technologies in the fact that while active packaging primarily deals with maintaining or increasing quality and safety of packaged foods (e.g., antimicrobial and antioxidant packaging), bioactive packaging provides a direct impact on the health of the consumer by generating healthier packaged foods. Biodegradable polymers and sustainable plastics are nowadays essential elements involved in novel bioactive packaging technologies. Biopolymers are very advantageous to develop compostable (including edible) active and bioactive films due to their availability, non-toxicity, biodegradability and renewability, and their unique properties [5]. Biodegradable and/or sustainable polymer materials, such as synthetic biodegradable polymers, bio-based polyesters and polyamides, and naturally occurring polymers (e.g., proteins and polysaccharides and derivatives) are considered among the most suitable materials for the controlled release of bioactive substances [6]. Biopolymers will also act as an \"added value\" argument within the food chain for the upward use of sustainable packaging. In this sense, polylactide (PLA) is a commercially available bio-based and biodegradable polymer, which is gaining acceptance for both existing and novel applications in the packaging field in the form of different articles such as films or injection-molded pieces and parts [7]. Creating a fully based PLA film with control release ability of bioactives is certainly a new concept of sustainable functional packaging. Additionally, PLA is also a Food and Drug Administration (FDA) approved material because it is degraded by hydrolysis to products that can be metabolized and excreted [8]. In this context, gallic acid (GA), that is, 3,4,5-trihydroxybenzoic acid, is a naturally occurring polyphenol commonly found in a variety of fruits and vegetables, such as grapes, cherry, tea leaves, and longan seeds [9], either in its free or bound form (e.g., gallotannins) [10]. Moreover, GA can be obtained from both liquid and solid wastes of the agro-food industry, for instance the wine industry [11], resulting in a good candidate of a waste material converted into an added-value product. GA has been shown to exhibit bioactive properties such as antioxidant, anti-inflammatory, anticarcinogenic, and antifungal properties [12]. Nevertheless, GA is unstable at high temperatures or in the presence of oxygen or light, conditions that are common in food processing and storage [13].