Developing a simultaneously antioxidant and pH-responsive κ-carrageenan/hydroxypropyl methylcellulose film blended with Prunus maackii extract.

к-Carrageenan and hydroxypropyl methylcellulose were used as matrix materials in which the extract of Prunus maackii pomace (EPm) was added to prepare a simultaneously antioxidant and pH-responsive film. EPm effectively increased the flexibility, barrier properties, antioxidant activity and pH-responsiveness of the film. When EPm content was increased to 8%, the elongation at break, heat-sealing strength and oxygen permeability of the film could reach 43.20 ±â€¯2.07%, 1096.39 ±â€¯51.29 N/m and 2.23 ±â€¯0.02 cm3 mm m-2 day-1 atm-1, respectively. Ultraviolet-visible spectra of EPm and the films color changed significantly in the range of pH 2.0-12.0. The κC/Hm/EPmy film obviously slowed the oxidation of lard compared with commercial PE film, and exhibited visible changes from red to purple when TVB-N in the pork reached 13.18 mg/100 g which was close to the freshness limit of 15.00 mg/100 g. Therefore, the κC/Hm/EPmy film can be promisingly used for extending oil shelf life and indicating the protein-rich food quality.

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.