Konjac glucomannan (KGM) is a natural water-soluble polymer extracted from konjac, which is considered as a safe, non-toxic, edible, renewable, and environmentally friendly polysaccharides [1]. The unique properties of KGM, such as hydrogen bonds network, spiral structure, and topological structure [2], make it well-suited for encapsulating active substances, thereby exerting its health benefits and becoming a sustainable biopolymer material with broad prospects. In recent years, KGM has been widely used in food packaging, biomedicine, and other industries due to its good film-forming properties, stability, biodegradability, and biocompatibility [3]. Besides, such polysaccharides based film has been promoted in the field of plastic packaging as a new material, and can partially replace non-biodegradable plastic packaging for food packaging and preservation [4].

However, the molecular structure of KGM presents an atypical helical state, resulting in a semi-flexible and linear conformation of its molecular chain [5]. This weak rigidity of the molecular chain hinders the composite film from attaining desirable mechanical properties [6]. Furthermore, the abundance of hydroxyl groups and the flexible side chain structure contribute to the significant water absorption of KGM, rendering the film prone to dissolution [7]. Consequently, the broader utilization of KGM in edible or biodegradable packaging and food preservation is considerably limited.

To overcome these limitations, researchers have developed various methods to improve the properties of KGM films, such as the development of blend films [8] with other biopolymers or nanomaterials [9]. In terms of functional properties, studies have improved the antibacterial and antioxidant properties of KGM films by adding functional active ingredients [10]. However, the direct addition of such components, especially for hydrophobic volatile small molecule, has problems such as poor compatibility, easy loss, and reduced mechanical properties of the films [11]. Recently, emulsion based KGM composite films has gradually attracted broad attention, such film can effectively improve a variety of inherent defects of pure polysaccharides based films [[12], [13], [14]] Xu et al. [15] developed an environmentally friendly active film by incorporating TEMPO (2, 2, 6, 6-tetramethylpiperidine-1-oxyl radical)-oxidized chitin nanocrystal-stabilized oregano essential oil Pickering emulsion into a KGM matrix with excellent antioxidant and antimicrobial properties.

Eugenol is the main component of clove essential oil with excellent antimicrobial and antioxidant properties. Eugenol can denature cell proteins and chemically react with cell membrane phospholipids to change the permeability, so it can be used to preserve food [16]. It was found that eugenol containing hydroxyl groups and can easily penetrate into the KGM matrix network and enhance the properties by hydrogen bonding interactions with KGM [17,18]. Such composite film, in turn, can alter the stability, bioavailability, and sustained release of aroma compounds through steric hindrance and interaction with active substances [19]. Besides, studies had found that cellulose nanocrystals [9,20], starch nanocrystals [21,22], cyclodextrins [23], and other hydroxy-rich particles can strengthen the mechanical properties of the film by forming hydrogen bonds with hydroxyl groups in the polysaccharides matrix.

Considering the respective advantages of aroma small molecules and hydroxy-rich Pickering particles, we speculated that the combination of the above two ingredients to strengthen the polysaccharides-based packaging film may be an effective means. And the information on the preparation of eugenol Pickering emulsions stabilized by β-CD/SC and the effect of the addition of such Pickering emulsions on the properties of KGM films is extremely limited. In this study, β-cyclodextrin/sodium caseinate/Tween-20 was used as solid particles to prepare the eugenol loaded Pickering emulsion, and the emulsion was then incorporated into the KGM system to fabricate a novel composite film. The physical and functional properties of the composite films, such as microstructure, mechanical properties, thermal stability, antioxidant properties, antibacterial properties, and preservation properties, were characterized. Based on the existing defects of pure KGM film, this study aimed to develop a novel means to improve the film performance and provide a new insight for the development and application of new food packaging film.