Plasticizers improved flexibility, homogeneity, and color stability in pitahaya (Hylocereus sp.) peel-based biopolymer films aimed at food packaging
Laura Arroyo-Esquivel, Víctor M. Jiménez, Fabián Vásquez-Sancho, Patricia Esquivel
Abstract
The growing demand for sustainable food packaging materials has driven the exploration of novel biopolymer sources. This study aimed to develop biopolymer films (Bfs) from pitahaya ( Hylocereus sp.) peels using three plasticizers (glycerol, sorbitol, and ethylene glycol) at three concentrations (0.05, 0.06, and 0.07 mol/L) via the casting method. The Bfs were characterized for their performance, stability, and potential applications at two time points (day 1 and day 30). The films were homogeneous, fracture-free, and exhibited a color range from brown to light brown, with thickness between 0.087 and 0.175 mm. Solubility tests showed the highest water solubility in sorbitol (59 %) and glycerol (56 %) Bfs, compared with the control (43 %) and ethylene glycol (37 %). Films with ethylene glycol exhibited the lowest solubility in both acidic (36 %) and basic (19 %) conditions. Moisture content was about 22 % across all treatments. Bfs containing plasticizers exhibited elongation between 11.9 % and 14.2 %, whereas control Bfs showed an elongation of 5.1 %. The lowest water vapor permeability was observed in the control Bfs (2.431 µg s −1 m −2 Pa −1 ), while glycerol-supplemented Bfs had the highest (3.938 µg s −1 m −2 Pa −1 ). Thermal analysis indicated a constant glass transition temperature of 62.4°C, a melting temperature of 131°C, and a melting enthalpy of 241.6 J g −1 , with no differences between treatments. X-ray diffraction identified peaks at 2θ = 14° and 32° (pectin) and 2θ = 22° (lignocellulose). These results highlight the potential of pitahaya peel-based Bfs as sustainable materials for food packaging applications. • Biopolymer films from pitahaya peel represent a sustainable alternative for the use of agricultural waste. • The addition of plasticizers significantly improves the mechanical properties and homogeneity of the films. • Biopolymer films show thermal and structural stability, which makes them suitable for various industrial applications. • The low water vapor permeability and durability of the films highlight their potential for applications in environmentally friendly food packaging.