Comparative preservation effect of water-soluble and insoluble chitosan from Tenebrio molitor waste

Development of Active Antibacterial CEO/CS@PLA Nonwovens and the Application on Food Preservation

The biodegradable activity antibacterial materials have been widely applied on food preservation because they not only protect foods from pathogenic attacks but also relieve environmental pollution. Biodegradable melt-blown nonwovens (MB) have several advantages over the other materials in terms of a simpler and more environmentally friendly fabrication process, higher specific surface area, and lower cost. Herein, polylactic acid (PLA) MB is first modified by polydopamine (PDA) to activate the surface. Then, chitosan (CS) and cinnamon essential oil (CEO) are used to decorate the surface of the modified PLA MB via a simple one-pot method to prepare CEO/CS@PLA MB with different CEO contents. Compared with PLA MB, CEO/CS@PLA MB had a rougher surface and larger average fiber diameter, while the average pore diameter and air permeability reduced. The input of CEO led to a decrease in the tensile strength of CEO/CS@PLA MB and an obvious increase in the elongation at break. The combination of CS and CEO shows excellent synergistic antibacterial effect. The antibacterial efficiencies of CEO/CS@PLA MB against Escherichia coli and Staphylococcus aureus enhance with the increase of the CEO content. When the weight ratio of CS to CEO is 1:2, the antibacterial efficiencies of CEO2/CS@PLA MB against E. coli and S. aureus are 99.98 and 99.99%, respectively. When being applied to the preservation of fresh strawberry, CEO2/CS@PLA MB can effectively inhibit the microbial growth in strawberry and reduce decay, which extends the shelf time of strawberry.

The current state of research and potential applications of insects for resource recovery and aquaculture feed

Concerns about fishmeal use and its ecological footprints must be addressed for the aquaculture industry to move on as a sustainable food production sector. Through recent research outcomes, the insect-based meals in fish diets have promise and harnessed promises for commercial applications. In this midst, the efficiency of the selected insects in valorizing biological waste, as well as the nutritional profile of the harvested insects for use in fish diets, will be the driving forces behind such an approach. More extensive research has been published on the suitability of the waste substrate, the nutritional profiling of the meals, the level of substitution, the effects on growth, the immune physiology, and the flesh quality of the animals. Previously, there are only a few reviews available in insect protein applications in aqua feed that focused particularly on the nutritional quality and substitution levels. Considering the dearth of available work, the goal of this review is to provide a more comprehensive account of the resource recovery potential of insects and its derivatives, with a special emphasis on quality as determined by substrate used and processing techniques. Suggestions and policy implications for a sustainable approach to achieving a circular bio-economy of insect farming and its application in aquaculture are discussed for progression and advancement of the existing state of the art.

Preparation and characterization of functionalized chitosan/polyvinyl alcohol composite films incorporated with cinnamon essential oil as an active packaging material

In this study, amphiphilic chitosan (NPCS-CA) was synthesized by grafting quaternary phosphonium salt and cholic acid onto the chain of chitosan, aiming to develop an active edible film based on NPCS-CA and polyvinyl alcohol (PVA) incorporated with cinnamon essential oil (CEO) by the casting method. The chemical structure of the chitosan derivative was characterized by FT-IR, ¹H NMR and XRD. Through the characterization of FT-IR, TGA, mechanical and barrier properties of the composite films, the optimal proportion of NPCS-CA/PVA was determined as 5/5. And, the tensile strength and elongation at break of the NPCS-CA/PVA (5/5) film with 0.4 % CEO were 20.32 MPa and 65.73 %, respectively. The results revealed that the NPCS-CA/PVA-CEO composite films exhibited an excellent ultraviolet barrier property at 200-300 nm and significantly reduced oxygen permeability, carbon dioxide permeability and water vapor permeability. Furthermore, the antibacterial property of film-forming solutions against E. coli, S. aureus, and C. lagenarium was distinctly improved with the increase of NPCS-CA/PVA proportion. And, the multifunctional films effectively extended the shelf-life of mangoes at 25 °C based on the characterization of surface changes and quality indexes. The NPCS-CA/PVA-CEO films could be developed as biocomposite food packaging material.

Tenebrio molitor as a source of interesting natural compounds, their recovery processes, biological effects, and safety aspects

Nowadays, it is urgent to produce in larger quantities and more sustainably to reduce the gap between food supply and demand. In a circular bioeconomy vision, insects receive great attention as a sustainable alternative to satisfy food and nutritional needs. Among all insects, Tenebrio molitor (TM) is the first insect approved by the European Food Safety Authority as a novel food in specific conditions and uses, testifying its growing relevance and potential. This review holistically presents the possible role of TM in the sustainable and circular solution to the growing needs for food and nutrients. We analyze all high value-added products obtained from TM (powders and extracts, oils and fatty acids, proteins and peptides, and chitin and chitosan), their recovery processes (evaluating the best ones in technical and environmental terms), their nutritional and economical values, and their biological effects. Safety aspects are also mentioned. TM potential is undoubted, but some aspects still need to be discussed, including the health effects of substances and microorganisms in its body, the optimal production conditions (that affect product quality and safety), and TM capacity to convert by-products into new products. Environmental, economic, social, and market feasibility studies are also required to analyze the new value chains. Finally, to unlock the enormous potential of edible insects as a source of nutritious and sustainable food, it will be necessary to overcome the cultural, psychological, and regulatory barriers still present in Western countries.

Rational Design of Smart Hydrogels for Biomedical Applications

Hydrogels are polymeric three-dimensional network structures with high water content. Due to their superior biocompatibility and low toxicity, hydrogels play a significant role in the biomedical fields. Hydrogels are categorized by the composition from natural polymers to synthetic polymers. To meet the complicated situation in the biomedical applications, suitable host–guest supramolecular interactions are rationally selected. This review will have an introduction of hydrogel classification based on the formulation molecules, and then a discussion over the rational design of the intelligent hydrogel to the environmental stimuli such as temperature, irradiation, pH, and targeted biomolecules. Further, the applications of rationally designed smart hydrogels in the biomedical field will be presented, such as tissue repair, drug delivery, and cancer therapy. Finally, the perspectives and the challenges of smart hydrogels will be outlined.

Carboxymethyl chitosan-pullulan edible films enriched with galangal essential oil: Characterization and application in mango preservation

This study aimed to develop an active edible film based on carboxymethyl chitosan (CMCS) and pullulan (Pul) incorporated with galangal essential oil (GEO) by the casting method. And their physical properties, structural and preservation effect on mangoes were characterized. The CMCS/Pul ratio was determined to be 2.5:2.5 after the optimization of physical properties, mechanical properties and barrier properties of the blend film. The results of FT-IR and XRD showed that hydroxyl groups of Pul interacted with the carboxyl groups of CMCS and the blend films had good compatibility. Good thermal stability of CMCS/Pul-GEO films was further proven by TGA curves. The CMCS/Pul-8 %GEO film showed effective preservations on mango fruits during 15 days of storage at 25 ± 1 °C, based on the characterization by fruits weight loss, firmness, titratable acidity, soluble solids. Consequently, CMCS/Pul-GEO blend films may be a promising eco-friendly packaging material for the industrial application of fruit preservation.

Extraction, physicochemical characterization, and morphological properties of chitin and chitosan from cuticles of edible insects

As an alternative, cuticles from edible insects was proposed as an unconventional but viable source of chitin and chitosan. The chitin present in the mealworm's (Tenebrio molitor) cuticles was obtained biotechnologically in one step of enzymatic deproteinization and after deacetylated. Differences in the physicochemical characteristics and the properties of the cuticles, chitin, and chitosan were investigated in this study. Commercial chitosan was used as a reference sample to validate the methods used. The enzymatic deproteinization used to obtain chitin showed an efficiency of 85%. The global yield of the process (cuticle-to-chitosan) was 31.9%. The characterization results of these polymers using DSC, FT-IR, XRD, TGA, and SEM techniques demonstrate consistency with the degree of deacetylation of the obtained chitosan, allowing the differentiation between chitin and chitosan. This study suggests that the wastes of edible insect breeding should be collected and evaluated as an alternative of chitin/chitosan source.

High-substitute nitrochitosan used as energetic materials: Preparation and detonation properties

In order to develop new high-energy materials utilizing natural products, a high-substitute nitrochitosan was prepared with different methods. Prepared processes and detonation properties of the nitrochitosan samples were systematically studied. The nitration substitute degree, nitrogen content, exothermic decomposition enthalpy, heat of combustion, impact sensitivity, detonation velocity and detonation pressure of the prepared high-substitute nitrochitosan were 2.01, 16.67 %, -2226 J g^-1, -7831.6 ± 116.3 J g^-1, >14.2 J, 7.81 km s^-1, and 24.03 GPa, respectively. Compared with nitrocellulose (NC), the nitrogen content, impact sensitivity and detonation properties of the prepared nitrochitosan were significantly improved. Nitrochitosan and RDX can form a uniform composite in acetone. With the increase of RDX content, the impact sensitivity of composite increased, but the composite was more stable and not easy to decompose. High-substitute nitrochitosan presents a potential application in solid propellants.