Fabricating a visibly colorimetric film via self-releasing of anthocyanins from distributed mulberry pomace particles in hydrophilic sodium carboxymethyl starch-based matrix to monitor meat freshness.

A highly distinguishable indicator film was developed based on sodium carboxymethyl starch, κ-carrageenan, carboxylated cellulose nanocrystals and mulberry pomace particles (MPPs). As the content of MPPs increased from 0 % to 6 %, the tensile strength decreased from 11.71 MPa to 5.20 MPa, the elongation at break increased from 26.84 % to 43.76 %, respectively, and the haze increased from 34.12 % to 52.10 %. The films accurately exhibit a color change from purple to blue-green under alkaline conditions. The enhanced haze improved the visible resolution of the films during the color-changing process. The films with the size of 7.50 mm × 7.50 mm and 10.0 mm × 10.0 mm exhibited obvious color changes when the total volatile basic nitrogen reached 14.60 mg/100 g and 19.04 mg/100 g, respectively, which accurately indicated the quality of pork and fish. This study will offer a simplified path to improve both accurate sensitivity and distinguishability for smart films.

Improving the comprehensive properties of chitosan-based thermal insulation aerogels by introducing a biobased epoxy thermoset to form an anisotropic honeycomb-layered structure.

Naturally-derived aerogels have attracted considerable attention owing to their good biocompatibility, biodegradability and sustainability, but their weak mechanical properties largely limit their applications in various fields. Herein, we proposed the use of a directional freeze-drying method to prepare an anisotropic honeycomb three-dimensional porous aerogel with water-soluble chitosan (CS) as a rigid skeleton and water-soluble biobased epoxy resin as cross-linked hard segments, which had low volume shrinkage and density of 13.9 % and 34.3 mg/cm3, respectively. The resultant aerogel had anisotropic mechanical properties, such as rigidity in the axial direction with a maximum axial modulus of 6.71 MPa, which was 51.6 times larger than that of the pure chitosan aerogel, demonstrating a good compressive elasticity in the radial direction. It also had anisotropic thermal management properties, with a lower thermal conductivity in the radial direction than in the axial direction, down to 0.029 W/mK. The introduction of biobased epoxy resin improved the overall thermal stability, flame retardancy, and increased the biomass content in the aerogel, reducing the carbon footprint of the material. This study paves the way for the construction of a special graded porous, structurally and functionally integrated thermal insulation aerogel, which is of great significance for the development of new thermal insulation materials.

Fabricating an anti-shrinking κ-carrageenan/sodium carboxymethyl starch film by incorporating carboxylated cellulose nanofibrils for fruit preservation.

A stronger and dimension-stabilized film was obtained using κ-carrageenan and sodium carboxymethyl starch (CMS) with carboxylated cellulose nanocrystals (C-CNC) as a reinforcing agent and anti-shrinkage agent. C-CNC endowed the films with better mechanical properties as well as excellent dimensional stability. The film solutions showed shear thinning and acted as a pseudoplastic fluid. When C-CNC content was increased from 0% to 12%, the tensile strength and elongation at break of the films improved from 23.89 MPa to 38.37 MPa and 21.00% to 27.31%, respectively. The films maintained good thermal stability and barrier performance. The Zeta potential of the film suspension can reach below -30 mV, indicating C-CNC enhanced the electrostatic repulsion in the film-forming system, which favored the network structure more continuous and stable. By virtue of the excellent mechanical properties and dimensional stability, strawberries can be tightly wrapped without cracks by the coatings to delay the deterioration greatly. By comparing the weight loss rate, Vc, total soluble solid, hardness, titratable acid and pH, CCC12-coated strawberries were closer to fresh ones. Therefore, this study has developed a feasible, low-cost and green fruit coating that can be potentially utilized on a large-scale.

Self-assembling crystals of an extract of Flos Sophorae Immaturus for improving the antioxidant, mechanical and barrier properties of a cassia gum film.

A novel antioxidative film was prepared by drying a film-forming solution containing the Flos Sophorae Immaturus extract (FSIE) (0-3.5%) and cassia gum (CG). Scanning electron microscopy (SEM) showed that FSIE was successfully compounded with CG. Although the addition of FSIE slightly increased the water vapor permeability (WVP) and O2 permeability (OP) of the film, it also improved its ability to block ultraviolet light significantly. The appropriate amounts of FSIE increased the tensile strength (TS) from 20.9 MPa to 30.2 MPa but reduced the elongation at break (EB) from 38.7% to 27.6%. The films doped with FSIE exhibited strong antioxidative activity and high rates of free radical scavenging. Total phenols exhibited a positive trend as the amount of FSIE increased in 50% of ethanol. The practical application of these composite films was investigated by evaluating the quality of lard wrapped in the films. After 25 d, the acid value (XAV) and peroxide value (POV) of lard packaged in CG/FSIE2% were lower than the values for lard packaged in CG/FSIE0% and plastic bag. These results showed that the CG/FSIE film had superior antioxidative activity compared to films made from plastic and pure CG.

A semen cassia gum-based film with visual-olfactory function for indicating the freshness change of animal protein-rich food.

Bromothymol blue (BTB) was fixed on the cationic cellulose fibers (CCFs) to prepare pH sensitive fibers (pH-SFs). The pH-SFs as intelligent indicator were added into the semen cassiae gum (SCG) as a weakly acidic matrix to prepare a visual-olfactory film. The 13C NMR results show that the CCFs were successfully obtained by introducing hydroxypropyltriethylamine groups which showed strong affinity to BTB molecules. Rheology results demonstrated that all of the film-forming solutions were shear-thinned fluids with non-Newtonian behavior. Scanning electronic microscopy showed that the addition of pH-SFs makes the film surface rougher and rougher. The addition of pH-SFs < 3% improved the tensile strength of the film. The visual-olfactory film was sensitive to ammonia with a highly visible color change from pale yellow to blue-green. The SCG-3SFs film pre-treated in NaOH solution changed from blue to pale yellow while the raw milk was close to spoilage. The light yellow SCG-3SFs film changed to blue-green as the freshwater shrimp changed from fresh to spoilage. The results indicate that the visual-olfactory film can be used for perceiving the freshness of milk and freshwater shrimp.

An Intelligent Film Based on Cassia Gum Containing Bromothymol Blue-Anchored Cellulose Fibers for Real-Time Detection of Meat Freshness.

To prepare intelligent cellulose fiber (ICF), cellulose fibers were modified by grafting hydroxypropyltriethylamine groups to which bromothymol blue (BTB) was anchored. The ICFs were incorporated into cassia gum (CG) to prepare a pH-sensitive intelligent film. The Fourier transform infrared results indicated that BTB has been introduced in the CG-ICF5 film. Scanning electronic microscopy indicated that the addition of ICF can loosen the structure of the film. The incorporation of ICF decreased light transmittance and water vapor permeability but did not significantly affect thermal stability. The mechanical properties were weakened with 3% ICF addition and were improved with 5% ICF addition. The release experiment indicated that 46.784% and 8.297% of BTB was released from the CG-ICF5 film under oscillating to 50% and 95% alcohol/water solution, respectively. The response of the intelligent films to triethylamine in environments with different relative humidities was investigated. A visible color change occurred in the triethylamine environment within 20 min. Pork and chicken spoilage experiments were performed to study the application of the intelligent film in monitoring meat freshness during spoilage. Obvious color changes appeared, demonstrating that the intelligent film has potential for use in real-time indication of meat spoilage.