Effect of oxidized chitin nanocrystals and curcumin into chitosan films for seafood freshness monitoring

Fabrication of halochromic smart films by immobilizing red cabbage anthocyanins into chitosan/oxidized-chitin nanocrystals composites for real-time hairtail and shrimp freshness monitoring

In this study, halochromic smart films were produced, characterized, and applied to monitor the freshness of hairtail and shrimp in real-time. Red cabbage anthocyanins (RCAs) solution illustrated significant color variations (red-pink-blue-green) in different pH environments. RCAs were successfully immobilized into chitosan (CS)/oxidized-chitin nanocrystals (OCN) composites through hydrogen bonding, and cohesive film structures were formed. When the proper concentration of RCAs was incorporated into the composites, improved water vapor permeability (WVP), oxygen permeability (OP), mechanical, UV-blocking, and antioxidant properties were observed. Moreover, the smart films exhibited distinguishable changes of color to ammonia vapor and acidic/alkaline environment within short time intervals, which were easy to discern by naked eyes. Finally, the smart films were applied to monitor the freshness of hairtail (Trichiurus lepturus) and shrimp (Penaeus vannamei). The film color changed significantly during storage time, and three stages of product freshness (fresh, medium fresh, and spoiled) were successfully differentiated. Strong correlations among three freshness indicators and two colorimetric parameters were also identified and analyzed. Overall, the smart system assembled from non-toxic and biodegradable components could contribute to monitoring the freshness of seafood, like hairtail and shrimp, in real-time.

Chitosan-riboflavin composite film based on photodynamic inactivation technology for antibacterial food packaging

Photodynamic inactivation (PDI) is a novel sterilization technology that has proven effective in medicine. This study focused on applying PDI to food packaging, where chitosan (CS) films containing photosensitizing riboflavin (RB) were prepared via solution casting. The CS-RB composite films exhibited good ultraviolet (UV)-barrier properties, and had a visually appealing highly transparent yellow appearance. Scanning electron microscopy (SEM) confirmed even dispersion of RB throughout the CS film. The addition of RB led to improved film characteristics, including the thickness, mechanical properties, solubility, and water barrier properties. The CS-RB⁵ composite films produced sufficient singlet oxygen under blue LED irradiation for 2 h to inactivate two food-borne pathogens (Listeria monocytogenes and Vibrio parahaemolyticus) and one spoilage bacteria (Shewanella baltica). The CS-RB composite films were assessed as a salmon packaging material, where inhibition of bacterial growth was observed. The film is biodegradable, and has the potential to alleviate the issues associated with the excessive use of petrochemical materials, such as environmental pollution and limited resources. The CS-RB composite films showed potential as a novel environmentally friendly packaging material for shelf-life extension of refrigerated food products.

Monitoring freshness of chicken breast by using natural halochromic curcumin loaded chitosan/PEO nanofibers as an intelligent package

Intelligent packaging is important to get information about real time quality of foods. The objective of this study was to develop an electrospun nanofiber halochromic pH sensor film using curcumin, chitosan (CS) and polyethylene oxide (PEO) to monitor chicken freshness. Conductivity and rheological behavior of CS/PEO/curcumin solutions were measured to understand the effect of solution properties on the morphology of the fibers. The morphological characteristics of nanofiber films were investigated by Field Emission Scanning Electron Microscopy (FESEM). Average diameter of the fibers was found to be between 283 ± 27 nm and 338 ± 35 nm. It was concluded that increasing CS amount in nanofibers decreased the diameter of the fibers. Thermal analysis and water vapor permeability features of the pH sensor were also examined. Color changes of curcumin loaded CS/PEO nanofiber film was evaluated on chicken breast package at 4 °C. The color of nanofiber film changed from bright yellow to reddish color which provided an opportunity to detect color changes by even the naked eyes of the untrained consumer. As a quality indicator, surface pH changes of the chicken breast and TVB-N (total volatile basic nitrogen) were measured. At the end of the day 5, pH value of 6.53 ±0.08 and TVB-N concentration of 23.45 ±3.35 mg/100 g indicated that food was at the edge of the acceptance level. As a result, curcumin loaded nanofiber satisfied the expectation and gave an opportunity to visualize real time monitoring of chicken spoilage.

Selective Isolation Methods for Cellulose and Chitin Nanocrystals

This Minireview focuses on the selective isolation methods for the preparation of cellulose nanocrystals (CNCs) and chitin nanocrystals (ChNCs). Various selective preparation strategies with specific preparation conditions and reaction mechanisms are summarized. In particular, these selective reaction routes include controlled acid hydrolysis and selective oxidations at specific positions of cellulose or chitin fibers as well as particular reaction sites of the repeating monosaccharide building blocks of their main chains. These lead to selective cleavage of the ordered and non-ordered regions of cellulose and chitin and result in efficient production of CNCs and ChNCs.

Preparation, Characterization and Application of a Low Water-Sensitive Artemisia sphaerocephala Krasch. Gum Intelligent Film Incorporated with Anionic Cellulose Nanofiber as a Reinforcing Component

A low-water-sensitive Artemisia sphaerocephala Krasch. gum (ASKG) based intelligent film was developed. Red cabbage extracts (RCE) was selected as a natural pH-sensitive indicator, and anionic cellulose nanofiber (ACNF) was added as a hydrophobic and locking host. The zeta potential, rheology, Fourier-transform infrared spectroscopy, X-ray diffractometry, and release results indicated that the RCE was locked by the ACNF via electrostatic interactions, moreover, broke the original complicated network and ordered arrangement of polymer molecules in the developed intelligent films. RCE addition decreased the tensile strength, oxygen, and water vapor barrier properties and light transmission of the developed intelligent films, while increasing the elongation at break. The films could respond to buffer solutions and NH₃ through different color changes. The developed intelligent film was hydrophobic, which could precisely detect the freshwater shrimp freshness in real time via color changes, which indicated that the films have potential in intelligent packaging and gas-sensing label fields.

pH-responsive pectin-based multifunctional films incorporated with curcumin and sulfur nanoparticles

pH-responsive pectin-based functional films have been prepared by incorporating curcumin and sulfur nanoparticles (SNP). FTIR and SEM results indicated that curcumin and SNP were uniformly dispersed in the pectin to form a well-developed composite film. Addition of curcumin and SNP significantly influenced the surface color and UV-blocking properties of the composite films. The composite films showed a higher water contact angle and thermal stability compared with the neat pectin film, however, the mechanical and water vapor barrier properties did not change significantly. The composite film exhibited antibacterial activity against E. coli and L. monocytogenes, and strong antioxidant activity. When applied to shrimp packaging, the film showed a pH-responsive highly distinctive color change from yellow to orange as the quality of the shrimp changed.

Development of bacterial cellulose/chitin multi-nanofibers based smart films containing natural active microspheres and nanoparticles formed in situ

Nanofiber-based materials have recently gained increasing attention in food packaging, drug delivery, and biomedical applications. In this study, a multi-nanofibers composite film was developed based on bacterial cellulose nanofiber (BCNF)/chitin nanofiber (CNF) hybridization. The nanofibers were responsible for the formation of well-dispersed curcumin (Cur) micro/nanoparticles in the nanocomposite films. The release of Cur from the films were affected by CNF and the sizes of Cur particles formed in situ. The Cur particles reduced tensile strength and increased water vapor permeability of BCNF film. However, CNF improved the mechanical strength and barrier property of the Cur/BCNF/CNF composite film. Moreover, the multi-nanofibers composite film showed excellent dynamic antioxidant capacity and antibacterial activity, as well as was capable to monitor pH change and trace amount of boric acid. Results of this study suggested that the Cur/BCNF/CNF composite film can be used as a smart and active food packaging material.

High intensity ultrasound modified ovalbumin: Structure, interface and gelation properties

Influence of high intensity ultrasound (HIUS) on the structure and properties of ovalbumin (OVA) were investigated. It was found that the subunits and secondary structure of OVA did not change significantly with HIUS treatment from the electrophoretic patterns and circular dichroism (CD) spectrum. The amount of free sulfhydryl groups increased and intrinsic fluorescence spectra analysis indicated changes in the tertiary structure and partial unfold of OVA after sonication increased. Compared with the untreated OVA, HIUS treatment increased the emulsifying activity and foaming ability, and decreased interface tension (oil-water and air-water interface), which due to the increased surface hydrophobicity and decreased the surface net charge in OVA, while the emulsifying and foaming stability had no remarkable differences. The increased particle size may be attributed to formation of protein aggregates. Moreover, the gelation temperatures of HIUS-treated samples were higher than the untreated OVA according to the temperature sweep model rheology, and this effect was consistent with the increased in surface hydrophobicity for ultrasound treated OVA. These changes in functional properties of OVA would promote its application in food industry.