Recently, foodborne diseases caused by Gram-positive or Gram-negative bacteria have become a main concern in the food industry field [1,2]. Antibacterial packaging materials can play an important role in controlling foodborne diseases because microbial contamination occurs mainly on the food surface [3,4]. Because of the increasing environmental problems caused by the accumulation of plastics, food packaging films based on natural biodegradable polymers with antibacterial properties have emerged in response to the increasing consumer demands [[5], [6], [7], [8]].

Starch, one of the natural biodegradable polymers, has become a promising material for preparing antibacterial packaging films because of its edibility, degradability, low cost, and film-forming ability, with many sites available for chemical or physical modifications [[9], [10], [11]]. Although starch has no antibacterial properties, it can provide a film matrix able to incorporate antibacterial substances that can inhibit microbial growth and food spoilage, thus extending shelf life [12,13].

Chitosan is the product of deacylated chitin extracted from crustacean shells that perform significant biocompatibility, antibacterial and hemostatic activity, biodegradability, and low toxicity [[14], [15], [16]]. Recently, antibacterial films based on a complex of starch and chitosan have received increasing attention. After introducing chitosan, starch films exhibit improved mechanical, film-forming, and antibacterial properties [17,18]. The interfacial bonding mechanism between starch and chitosan governs the microstructure and superior mechanical behaviors of the resulting antibacterial films [19,20]. However, the susceptibility to acidic and alkaline solubility issues of chitosan has limited its application in synthesizing starch/chitosan antibacterial films in neutral aqueous solution [21,22].

To overcome these issues, researchers have synthesized some quaternary derivatives of chitosan exhibiting marked solubility in a neutral aqueous solution. 2-hydroxypropyl-trimethylammonium chloride chitosan (HTCC) [23,24], an excellent quaternized chitosan, has been widely used as an antibacterial substance because of its remarkable broad-spectrum antibacterial property and significant water-solubility over a wide pH range [25,26]. Thus, a study on antibacterial HTCC/amylose starch film is now reported using HTCC as the antibacterial substance, amylose as the matrix, with glutaraldehyde (GA) as the cross-linker.

The main goal of the present study was to prepare antibacterial HTCC/amylose films, to investigate the interfacial bonding mechanism between amylose, HTCC, and GA, and to determine the effect of HTCC on improving their antimicrobial and mechanical properties. In the design, we postulated that the molecular chains of amylose starch and HTCC entwine via inter-molecular H-bond, whereas the amino groups of HTCC react with the aldehyde groups of GA to form the stable interface between HTCC and amylose starch. The postulated interfacial bonding mechanism was investigated experimentally using Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron (XPS) and was explained further by theoretical modeling. The effect of HTCC on the films was determined mainly by evaluating their mechanical and antibacterial properties. The HTCC/amylose films were evaluated practically by application to meat preservation.