Fabrication and characterization of a pH‐sensitive intelligent film incorporating dragon fruit skin extract

Abstract

A novel intelligent pH‐sensing indicator based on gelatin film and anthocyanin extracted from dragon fruit skin (Hylocereus polyrhizus) (DFSE) as a natural dye was developed to monitor food freshness by the casting method. Anthocyanin content of DFSE was 15.66 ± 1.59 mg/L. Dragon fruit bovine gelatin films were characterized by Fourier transform infrared spectroscopy (FTIR) and observed by a scanning electron microscope (SEM). Moisture content, mechanical properties, water solubility, water vapor permeability (WVP), light transmittance, color, and pH‐sensing evaluations were evaluated for potential application. FTIR spectroscopy revealed that the extracted anthocyanin could interact with the other film components through hydrogen bonds. When the extract was added, films showed a smooth and clear surface as observed by SEM. The addition of anthocyanin increased the moisture content, thickness, and water solubility of the films, but decreased the WVP and light transmittance of films. Also, the incorporation of 15% v/v DFSE decreased the tensile strength from 17.04 to 12.91 MPa, increasing the elongation at break from 91.19% to 107.86%. The films showed higher ΔE with increasing DFSE content, which indicated that the film had good color variability. A significant difference in the color of the films was observed with exposure to different pH buffer solutions. The findings demonstrated that gelatin film incorporated with DFSE could be used as a visual indicator of pH variations to monitor the freshness of foods during storage time.

Development of an Indicator Film Based on Cassava Starch–Chitosan Incorporated with Red Dragon Fruit Peel Anthocyanin Extract

“…The analysis was performed at room temperature (25 °C). Tensile strength, elongation at break, and Young’s modulus as measurements of film strength, film flexibility, and film stiffness, respectively, were determined using the formula [ 16 ]: where F = the force applied to the film, A 0 = the area of the film, = the increase in length, and L 0 = the initial length of the film.…”

“…The composite films were cut into 2 cm × 2 cm sections and coated with gold. The surface morphology of the composite films was observed using scanning electron microscopy (SEM) (Hitachi SU3500, Tokyo, Japan) with an electric voltage of 20 kV and high vacuum conditions (10 −2 –10 −3 Pa) [ 16 ].…”

“…Red dragon fruit peel anthocyanin is interesting to be developed as an indicator because its use can reduce the amount of organic waste. Moreover, it is sensitive to pH and can be used in antioxidant and antibacterial applications [ 16 ].…”

Fabrication and characterization of a smart film based on cassava starch and pomegranate peel powder for monitoring lamb meat freshness

“…One of the new and effective technologies in the food industry is intelligent biopolymer packaging, which is in the smart packaging category and provides the consumer with good information about the state of freshness or spoilage of food products, so these food packagings are receiving more and more attention (Azlim et al., 2022; Vedove et al., 2021; Xue Mei et al., 2020). Smart packaging films can display the freshness of food products, develop shelf life, and improve the quality and safety of food products during transportation and storage (Chen et al., 2020; Mahmood et al., 2022).…”

“…Smart packaging films can display the freshness of food products, develop shelf life, and improve the quality and safety of food products during transportation and storage (Chen et al., 2020; Mahmood et al., 2022). One of the intelligent systems used to detect the freshness of food products is pH‐sensitive packaging, which consists of two parts, including a biopolymer film and a pH‐sensing active agent (especially natural pigments such as anthocyanin; Azlim et al., 2022; Taherkhani et al., 2020). A pH‐sensitive intelligent packaging has been successfully used to display the freshness of food products, especially meat and meat products (Alamdari et al., 2021; Alizadeh‐Sani et al., 2021; Ghorbani et al., 2021; Li et al., 2022; Zhou et al., 2021).…”