## 1 Introduction  
Every year, 1.3 billion tons of food are wasted globally [1; 2]. This figure corresponds to almost one third of all food produced for humans [2]. In theory, global food production can provide for every living person, indicating that ineffective food distribution systems are substantial contributors to world hunger [3]. According to the United States Department of Agriculture, 31 percent of U.S. food supply at the retail and consumer levels is wasted [4]. Of the United States' total food waste, packaging accounts for 29.5% of municipal solid waste, suggesting that a more efficient material for the transport and storage of foods may contribute to less food wasted [5]. Simultaneously, our waste management systems face an overwhelming influx of discarded plastic products [6]. Even so-called recyclable materials have a limited number of cycles before they undergo phase separation and become unusable, meaning that recycling is not an effective solution to plastic waste [7]. A solution to both food spoilage and plastic waste is a biodegradable polymer that extends the shelf life of produce through selective permeability of the membrane. Currently, finding an appropriate bio-based polymer can be rather challenging because they are typically hydrophilic in nature, leading to high water vapor transmission rates [8; 9]. The concentrations of oxygen gas and water vapor must remain low to prevent spoilage due to oxidation [10; 11]. Within the localized packaging environment, a modified, carbon dioxide-rich environment is necessary to preserve food and delay rancidity [12; 13; 14]. Carbon dioxide maintains a low pH, which decreases microbe growth [12; 13; 14]. A polymer capable of the aforementioned tasks is poly(lactic acid) (PLA). PLA is a polyester that is classified as Generally Recognized as Safe (known as GRAS) by the U.S. Food and Drug Administration [15]. Commercial synthesis of PLA via the condensation of lactic acid is an environmentally friendly, inexpensive, and energy efficient process [16; 17; 18; 19; 20; 21]. For these reasons, PLA has been established as a viable biodegradable polymer for food packaging applications [22; 23; 24; 25; 26; 27]. PLA has two naturally occurring stereoregular forms, PDLA and PLLA [28]. A great deal of current research is focused on characterizing these forms with techniques such as nuclear magnetic resonance [29]. A racemic mixture of PLA leads to an amorphous polymeric structure [28]. The water vapor permeability of the racemic PLA is 14-23% lower than for the homopolymers, making racemic PLA an ideal choice for food packaging applications [30]. Moreover, dipole-dipole interaction and hydrogen bonding between the two stereoregular forms lead to a stronger, denser material with improved thermal stability [30]. Food packaging is inextricably linked to radiation in multiple ways. First, ionizing radiation is already utilized as a safe method of extending shelf life and ensuring the safety of food products [31]. Food is irradiated inside its packaging once it is ready for retail, and this process serves several purposes including the delay of sprouting and ripening, reduction of spoilage-causing organisms, control of insects, and the prevention of foodborne illness through elimination of pathogenic bacteria [31; 32]. Electron beam radiation for the treatment of fruits and vegetables is typically achieved with doses up to 10 kGy [31]. After the consumer has discarded the food packaging, radiation is used to enhance the slow biodegradation rate of PLA [33]. Elucidating the radiation chemistry mechanism of PLA via identification of the radiolytically produced free radicals and their decay will further the understanding of the physical properties, permeability, and biodegradability of PLA. It is expected that radiation-induced C-O-C bond scissions in the PLA will occur under the radiation conditions used in this work.