Search

World hunger is on the rise, yet one-third of food is wasted. It is necessary to develop an effective food preservation method to reduce food waste. This article reports a composite film based on chitosan biguanidine hydrochloride(CBg) and poly (N-vinyl-2-pyrrolidone)(PVP) that can be used as a conformal coating for fresh produce. Due to the strong positive charge of CBg, the film has excellent antibacterial properties. Owing to the hydrogen bonds between CBg and PVP, the film has good flexibility and mechanical properties. In addition, the coating is washable, transparent, and can reduce the evaporation of water. The above characteristics mean the film has broad application prospects in the field of food preservation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dialdehyde starch as a "smart gatekeeper" achieved on-demand release of thymol. • The membrane had pH and amylase responsive due to Schiff base and glycosidic bonds. • Acid and amylase secreted by melon R. stolonifer were used to trigger thymol release. • The membrane showed excellent antifungal ability and promising application effect. • The membrane had desirable biocompatibility and biodegradability. Antimicrobial active packaging was limited by the inability to release the antimicrobial agents at the required location, required time, and required quantity. Hence, it is necessary to develop smart release active packaging material that can on-demand release antimicrobial agents according to the storage microenvironment. In this work, a pH and amylase dual responsive release membrane (THY@PLA-COS-DAS) was designed by grafting dialdehyde starch (DAS) onto positively charged chitosan oligosaccharide-modified electrospinning porous poly (lactic acid) (PLA) nanofiber via Schiff base bond. The dialdehyde starch as the smart gatekeeper for on-demand releasing thymol had not only glycosidic bonds that could be hydrolyzed by amylase but also Schiff base bonds that formed with PLA-COS and were sensitive to acidic pH. And the cumulative release rate confirmed that the THY@PLA-COS-DAS could respectively release 78.1% and 98.6% of thymol after 120 h at pH 5.0 or 2 mg/mL glucoamylase conditions. More importantly, the secretion assay demonstrated that Rhizopus stolonifer (R. stolonifer) could secrete acid and amylase, which respectively facilitate the breaking of Schiff base bond and glycosidic bond, thus allowing smart release thymol in response to changes in the storage microenvironment. Meanwhile, THY@PLA-COS-DAS showed a 94.5% inhibition rate against R. stolonifer. More importantly, the biocompatible THY@PLA-COS-DAS could considerably maintain the melon's appearance and hardness compared with the control group. Thus, this pH and amylase dual responsive release nanofiber membrane achieved the sustainable on-demand release of antimicrobial agents to cost-effectively inhibit spoilage microorganisms and had significant potential in innovative antimicrobial active packaging materials. [ABSTRACT FROM AUTHOR]