Active coatings based on hydroxypropyl methylcellulose and silver nanoparticles to extend the papaya (Carica papaya L.) shelf life

This study aimed to understand the effect of silver nanoparticles (AgNPs) on physiochemical properties of hydroxypropyl methylcellulose (HPMC) film-forming solutions (FFS) and nanocomposite films (NCF), as well as the efficacy of these materials to control the development of anthracnose caused by Colletotrichum gloeosporioides in papaya (Carica papaya L.). FFS were characterized by pH, particle size distribution, and rheology. In addition, thickness, morphology, water contact angle, barrier, chemical, crystallinity, thermal, and mechanical properties from NCF were investigated. The minimum inhibitory concentration of AgNPs against C. gloeosporioides was determined by in vitro test. FFS with 0.25 wt% of AgNPs were used as coatings in papayas inoculated with C. gloeosporioides. Finally, the physicochemical parameters were investigated during their storing up to 7 days at 10 °C, followed by 7 days at 20 °C. The presence of AgNPs impacted the thickness, morphology, moisture content, chemical bonds, crystalline structure, and thermal properties of films. Coatings with 0.25 wt% of AgNPs reduced the incidence and severity of C. gloeosporioides and avoided the weight loss of papayas during storing. The ripening of papaya occurred naturally, showing that the coating only delayed this process. Thus, HPMC-AgNPs coating can be an alternative to extend the papaya shelf life.

Keywords: Anthracnose; Biopolymers; Food packaging; Fruit shelf life; Metal nanoparticles.