Recent advances in guar gum-based films or coatings: Diverse property enhancement strategies and applications in foods

Plastics sourced from petrochemicals are most commonly and widely used for food packaging films. However, the extensive employment of petrochemical plastics unavoidably brings about some adverse impacts on the environment due to the fact that plastics require years to naturally degrade and the burning of them would release some dangerous chemicals. Within this context, many efforts have been made to find renewable and low-toxic materials for the development of biodegradable films to partly supplant petrochemical plastics. Guar gum (GG) is a promising biopolymer for the development of packaging or coating films. Herein, the recent techniques employed to improve the physical and functional properties of GG-based films are discussed. Moreover, the potential applications of GG-based films and bio-active films in food products are comprehensively discussed. With an aim to improve the physical properties of GG-based films, many strategies have been examined, including modifications of GG, introducing plasticizers, blending with other polymers, layer-by-layer assembly technique, and incorporating nanoparticles, plant extracts (PEs), and essential oils (EOs), which can effectively improve the hydrophilic properties, mechanical properties, and barrier properties. Furthermore, numerous additives such as PEs, EOs, and metal nanoparticles (MNPs) have been employed to fabricate bio-active GG-based films with excellent antioxidant and antimicrobial properties. Importantly, GG-based films can be employed to maintain the storage quality of fruits, vegetables, snacks, livestock, and aquatic products, and the preservation effects can be further enhanced by incorporating some antioxidant and antimicrobial agents such as PEs, EOs, and greenly-synthesized MNPs.