Nanostructured Oxide-Based Systems for the pH-Triggered Release of Cinnamaldehyde

Facile preparation of pH-responsive antimicrobial complex and cellulose nanofiber/PVA aerogels as controlled-release packaging for fresh pork

Intelligent controlled release technologies that rely on environmental changes to control the release rate of antimicrobial agents have attracted attention in the field of food preservation. In this paper, cinnamaldehyde (CN) was grafted onto chitosan (CS) to form a pH-responsive controlled-release complex, CS-CN, via the Schiff base reaction. Then, tempo oxidized cellulose nanofibers (CNF) and PVA were prepared as aerogels loaded with CS-CN with different pore parameters (PCNF@CN). Release experiments showed that acid triggered the release of CN and increased the release from 10.3 to 68.4% with increasing pH. In addition, PCNF@CN showed significant pH-responsive antimicrobial properties against Escherichia coli and Staphylococcus aureus. Utilizing the water absorption of the aerogel and triggering the release of CN, the shelf life of fresh meat could be delayed for 4 days. This study demonstrated the potential application of PCNF@CN aerogel in functional food preservation packaging.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01487-8.

Cinnamaldehyde Inhibits Postharvest Gray Mold on Pepper Fruits via Inhibiting Fungal Growth and Triggering Fruit Defense

Gray mold infected with Botrytis cinerea frequently appears on fruits and vegetables throughout the supply chain after harvest, leading to economic losses. Biological control of postharvest disease with phytochemicals is a promising approach. CA (cinnamaldehyde) is a natural phytochemical with medicinal and antimicrobial activity. This study evaluated the effect of CA in controlling B. cinerea on fresh pepper fruit. CA inhibited B. cinerea growth in vitro significantly in a dose- (0.1-0.8 mM) and time-dependent (6-48 h) manner, with an EC50 (median effective concentration) of 0.5 mM. CA induced the collapse and breakdown of the mycelia. CA induced lipid peroxidation resulting from ROS (reactive oxygen species) accumulation in mycelia, further leading to cell leakage, evidenced by increased conductivity in mycelia. CA induced mycelial glycerol accumulation, resulting in osmotic stress possibly. CA inhibited sporulation and spore germination resulting from ROS accumulation and cell death observed in spores. Spraying CA at 0.5 mM induced a defense response in fresh pepper fruits, such as the accumulation of defense metabolites (flavonoid and total phenols) and an increase in the activity of defense enzymes (PAL, phenylalanine ammonia lyase; PPO, polyphenol oxidase; POD, peroxidase). As CA is a type of environmentally friendly compound, this study provides significant data on the activity of CA in the biocontrol of postharvest gray mold in peppers.

Cinnamaldehyde-Contained Polymers and Their Biomedical Applications

Cinnamaldehyde, a natural product that can be extracted from a variety of plants of the genus Cinnamomum, exhibits excellent biological activities including antibacterial, antifungal, anti-inflammatory, and anticancer properties. To overcome the disadvantages (e.g., poor water solubility and sensitivity to light) or enhance the advantages (e.g., high reactivity and promoting cellular reactive oxygen species production) of cinnamaldehyde, cinnamaldehyde can be loaded into or conjugated with polymers for sustained or controlled release, thereby prolonging the effective action time of its biological activities. Moreover, when cinnamaldehyde is conjugated with a polymer, it can also introduce environmental responsiveness to the polymer through the form of stimuli-sensitive linkages between its aldehyde group and various functional groups of polymers. The environmental responsiveness provides the great potential of cinnamaldehyde-conjugated polymers for applications in the biomedical field. In this review, the strategies for preparing cinnamaldehyde-contained polymers are summarized and their biomedical applications are also reviewed.

Fabrication of Gold Nanoparticles and Cinnamaldehyde-Functionalized Paper-Based Films and Their Antimicrobial Activities against White Film-Forming Yeasts

During storage and fermentation of kimchi, white film-forming yeasts (WFY) are generated on the surface of kimchi under various conditions. These yeasts include Candida sake, Pichia kudriavzevii, Kazachstania servazzii, Debaryomyces hansenii, and Hanseniaspora uvarum. Because of the off-odor and texture-softening properties of WFY that degrade the quality of kimchi, a method to prevent WFY is required. In this study, cinnamaldehyde (CIN) and gold nanoparticles (AuNPs) with a large surface area were grafted on a paper surface, which was termed the "Paper_AuNPs_CIN" film. CIN is an antimicrobial agent that is approved for use in food applications. In the as-fabricated Paper_AuNPs_CIN film, antimicrobial CIN molecules were physically adsorbed to the surface of AuNPs and simultaneously chemically synthesized on the paper surface via the imine reaction. The Paper_AuNPs_CIN film exhibited greater antimicrobial activity against the three WFY strains than a Paper_CIN film (which contains only CIN molecules). Since more CIN molecules were adsorbed to the large surface area of the paper-reduced AuNPs, the Paper_AuNPs_CIN film exhibited a higher antimicrobial activity. Using AuNPs and CIN simultaneously to inhibit the growth of WFY is a novel approach that has not yet been reported. The morphology and elemental mapping of the functionalized films were examined via scanning electron microscopy and energy-dispersive spectroscopy, elemental composition was analyzed via inductively coupled plasma optical emission spectroscopy, and chemical bonding and optical properties were investigated via Fourier transform infrared spectroscopy and diffuse reflectance spectroscopy. Additionally, agar-well diffusion assays were used to determine the antimicrobial activity against three representative WFY strains: C. sake, P. kudriavzevii, and K. servazzii.

Bio-based antibacterial food packaging films and coatings containing cinnamaldehyde: A review

As a typical bioactive compound from the bark and leaves of the trees of the genus Cinnamomum, cinnamaldehyde (CIN) is natural and safe. Its excellent antibacterial activity against various foodborne microorganisms is growingly regarded as a promising additive for improving and enhancing the properties of bio-based packaging films/coatings. This review systematically summarized the bio-based food packaging films/coatings containing CIN developed recently. The effects of CIN incorporation on physical and chemical properties of the antibacterial food packaging films/coatings, including thickness, color index, transparency, water content, water solubility, water contact angle, mechanical performances, water barrier performances, and antibacterial performances, were discussed. Simultaneously, this work also concluded that an explanation of the antibacterial mechanism of CIN and preparation methods of bio-based packaging films/coatings containing CIN/CIN carriers. Notably, the incorporation of CIN into the films/coatings could enhance their antibacterial performance extend the shelf-life of various foods, such as fish, meats, vegetables, fruits, and other perishable food, while improving their physical and chemical properties. Although incorporating CIN into food packaging films/coatings has been extensively studied, long-term follow-up research on the human safety of active food packaging films/coatings containing CIN needs to be carried out.