Keratin-Based Composite Bioactive Films and Their Preservative Effects on Cherry Tomato

• Published in: Molecules (Basel, Switzerland) Vol. 27; no. 19; p. 6331
• Main Authors: Wei, Lanlan, Zhu, Shuaijie, Yang, Huan, Liao, Zhiheng, Gong, Zexuan, Zhao, Wenwen, Li, Yan, Gu, Jinyan, Wei, Zhaohui, Yang, Jianting
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 26-09-2022; MDPI
• Subjects: Analysis; Antibacterial activity; Antioxidants; Biocompatibility; Biological activity; Biopolymers; Body weight loss; cherry tomatoes; Crystal structure; Curcumin; Diseases and pests; Environmental impact; Escherichia coli; Food; Food industry; Food packaging industry; Fourier transforms; Gelatin; Genetic aspects; Glycerol; Growth; Hydrogen bonds; Infrared spectroscopy; Keratin; keratin/gelatin/glycerin/curcumin film; Molecular interactions; Morphology; Packaging; Pectin; pig nail keratin; preservation; Preservatives; Proteins; Reducing agents; Safety and security measures; Scanning electron microscopy; Solanum lycopersicum cerasiforme; Staphylococcus aureus; Thermal properties; Thermogravimetric analysis; Thin films; Tomatoes; Weight loss; X-ray diffraction; China
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules27196331

In this study, keratins were extracted from pig nail waste through the reduction method using L-cysteine as a reductant. Curcumin was successively incorporated in a mixed solution including keratin, gelatin, and glycerin to prepare different kinds of keratin/gelatin/glycerin/curcumin composite films. The morphology of the keratin/ gelatin/glycerin/curcumin composite films were examined using scanning electron microscopy. The structures and the molecular interactions between curcumin, keratin, and pectin were examined using Fourier transform infrared spectroscopy and X-ray diffraction, and the thermal properties were determined through thermogravimetric analysis. The tensile strengths of keratin/gelatin/glycerin/curcumin and keratin/gelatin/curcumin composite films are 13.73 and 12.45 MPa, respectively, and their respective elongations at break are 56.7% and 4.6%. In addition, compared with the control group (no film wrapped on the surface of tomato), the ratio of weight loss of the keratin (7.0%)/gelatin (10%)/glycerin (2.0%)/curcumin (1.0%) experimental groups is 8.76 ± 0.2%, and the hardness value of the tomatoes wrapped with composite films is 11.2 ± 0.39 kg/cm3. Finally, the composite films have a superior antibacterial effect against Staphylococcus aureus and Escherichia coli because of the addition of curcumin. As the concentration of curcumin reaches 1.0%, the antibacterial activity effect of the film is significantly improved. The diameter of the inhibition zone of E. coli is (12.16 ± 0.53) mm, and that of S. aureus is (14.532 ± 0.97) mm. The multifunctional keratin/gelatin/glycerin/curcumin bioactive films have great potential application in the food packaging industry.