Development of Smart Bilayer Alginate/Agar Film Containing Anthocyanin and Catechin-Lysozyme

Fabricating a high-loading smart film to monitor pork freshness via adsorption of anthocyanins on simultaneously etched, anionized and bleached wood cell wall

In this paper, wood cell walls were simultaneously roughened, carboxylated, and bleached via NaOH/H2O2 treatment and roughened-poplar film (RPF) was obtained. Compared with the untreated film, the carboxyl group content increased 8 times to 1.92 mmol/g, and the pore growth rate reached 11.24%. Afterwards, a pH-indicator wood film (CTA-RPF) was prepared by self-adsorption of anthocyanins on RPF. It rapidly changed from purple to green within 7 s in 0.25 mL of ammonia at 53% RH and the initial color could restore in the air. When anthocyanins adsorption capacity reached 1.95 mg/g, only 0.36 cm2 of the film could accurately indicate the quality change of 300 g pork. Currently, CTA-RPF is the smallest smart film that can track the maximum mass of pork after comparing with other researches, therefore, promising to be used as a smart indicator label to track the freshness of pork in real market circulation.

Quercetin-loaded melanin nanoparticle mediated konjac glucomannan/polycaprolactone bilayer film with dual-mode synergistic bactericidal activity for food packaging

It is still difficult for a single antibacterial modality to realize satisfactory management of bacterial breeding in food preservation. To solve this problem, we developed a photothermal-derived dual-mode synergistic bactericidal konjac glucomannan (KGM)/polycaprolactone (PCL) bilayer film incorporated with quercetin-loaded melanin-like nanoparticles (Q@MNPs). The results showed that the mechanical properties (TS: 29.8 MPa, EAB: 43.1 %), UV shielding properties, and water resistance (WCA: 124.1°, WVP: 3.92 g mm/m2 day kPa) of KGM-Q@MNPs/PCL bilayer films were significantly improved. More importantly, KGM-Q@MNPs/PCL bilayer film presented outstanding photothermal inversion and controlled release behavior of Q triggered by near infrared (NIR) radiation, thus contributing to excellent dual-mode synergistic antibacterial properties against E. coli and S. aureus. Meanwhile, the KGM-Q@MNPs/PCL bilayer film possessed good biocompatibility and low toxicity. As a proof-of-concept application, we further verified the significant value of film for the preservation of cherry tomatoes. Since KGM-Q@MNPs/PCL bilayer film showed excellent biodegradability, this work will aid the development of sustainable antibacterial food packaging materials.

Colorimetric indicator films based on carboxymethyl cellulose and anthocyanins as a visual indicator for shrimp freshness tracking

This study aimed to evaluate the response efficiency of colorimetric indicator films based on carboxymethyl cellulose (CMC) incorporated with different anthocyanins [Karanda alone (CMC/AK), butterfly pea alone (CMC/AB), and a mixture of anthocyanins from Karanda and butterfly pea (CMC/AK75/AB25)] for tracking shrimp freshness during storage at different temperatures and times (4 °C for 8 days and 25 °C for 30 h). The mathematical models were also applied to predict their freshness and shelf life. The CMC/AK75/AB25 indicator film was the most sensitive and clearly changed color, which could be distinguished by the naked eye. Color changes indicated the shrimp deterioration processes: dark purple (fresh), purplish gray or gray (semi-fresh), and olive green or brown (spoilage). During shrimp storage at temperatures of 4 and 25 °C, the pH reached 7.52 and 8.14, TVB-N 35.98 and 72.72 mg/100 g, and TVC 5.75 and 7.88 log CFU/g, respectively, indicating shrimp had completely deteriorated. Furthermore, there was a positive correlation between the ΔE value of the indicator film and both TVB-N and TVC. These findings suggest that the CMC/AK75/AB25 indicator film could serve as a real-time visual indicator for tracking shrimp freshness and could enhance the guarantee of shrimp safety.

Smart colorimetric sensing films based on carboxymethyl cellulose incorporated with a natural pH indicator

This study aimed to combine various natural pH indicators of anthocyanin from Karanda (CA) with anthocyanin from butterfly pea flower (BA) or curcumin (CC) to improve the sensitivity of CA. CA75/BA25 and CA25/CC75 enhanced the sensitivity of the endpoint colour change of CA. A smart colorimetric sensing film was also developed and characterised by loading different natural pH indicators on carboxymethyl cellulose (CMC) films. The addition of different natural pH indicators increased the thickness, elongation, colour (a* and b* values), and contact angle of CMC films (p < 0.05). However, the tensile strength, water vapour permeability, film solubility, light transmission, and L* value decreased when different natural pH indicators were added (p < 0.05). The indicator films demonstrated enhanced antioxidant capacity and thermal stability. The FTIR spectra showed that natural pH indicators were successfully immobilised into the CMC films. Notably, the CMC/CA75/BA25 film was the most sensitive film to changes in volatile ammonia and different pH buffer solutions. The CMC/CA75/BA25 film changed from purple to green with exposure to ammonia solution and from pink to purple to blue to green with increasing pH. Therefore, the CMC/CA75/BA25 film has potential as a colorimetric sensing film, providing a more accurate assessment result.

Synergistic effects of EDTA and lysozyme on the properties of hydroxypropyl starch nano antibacterial films

Hydroxypropyl starch (HPS) nano antibacterial films incorporating Ethylene Diamine Tetraacetic Acid (EDTA) and lysozyme (LY) were fabricated via solvent casting method. The synergistic effects of EDTA and LY on the microstructure, component interactions, color, optical, mechanical, barrier and antibacterial properties of HPS nano antibacterial films were evaluated. The results indicated that EDTA and LY were well dispersed in the matrix of the HPS nano antibacterial films, the film-forming substrates have good compatibility, resulting in a dense multi-layer structure of the HPS nano antibacterial films. The addition of EDTA and LY increased the color parameters (L*, a*, b* and △E*) of the HPS nano antibacterial films. The synergistic effects of EDTA and LY significantly decreased the light transmission of the HPS nano antibacterial films. The presence of EDTA and LY increased the tensile strength (TS) and the elongation at break (EAB) of the HPS nano antibacterial films. The TS and EAB of E2.5L1 reached the highest values of 6.329 MPa and 50.24 %, respectively. The incorporation of EDTA and LY had positive effects on the improvement of water vapor permeability (WVP) and oxygen permeability (OP). The WVP and OP of E2.5L1 reached the highest values of 0.9350 × 10-12 g cm/cm2•s•Pa and 0.297 × 10 -2 g m/m2 •d, respectively. In addition, EDTA and LY had significant synergistic effects on the antibacterial activity against S. aureus (Gram-positive bacteria) and E. coli (Gram-negative bacteria). E2.5L1 exhibited the highest antibacterial activity and the inhibition zone diameters of S. aureus and E. coli were 3.69 mm and 4.28 mm, respectively. The HPS nano antibacterial films incorporating EDTA and LY are potential functional packaging materials.

A Systematic Review of Butterfly Pea Flower (Clitoria ternatea L.): Extraction and Application as a Food Freshness pH-Indicator for Polymer-Based Intelligent Packaging

The butterfly pea flower (Clitoria ternatea L.) (BPF) has a high anthocyanin content, which can be incorporated into polymer-based films to produce intelligent packaging for real-time food freshness indicators. The objective of this work was to systematically review the polymer characteristics used as BPF extract carriers and their application on various food products as intelligent packaging systems. This systematic review was developed based on scientific reports accessible on the databases provided by PSAS, UPM, and Google Scholar between 2010 and 2023. It covers the morphology, anthocyanin extraction, and applications of anthocyanin-rich colourants from butterfly pea flower (BPF) and as pH indicators in intelligent packaging systems. Probe ultrasonication extraction was successfully employed to extract a higher yield, which showed a 246.48% better extraction of anthocyanins from BPFs for food applications. In comparison to anthocyanins from other natural sources, BPFs have a major benefit in food packaging due to their unique colour spectrum throughout a wide range of pH values. Several studies reported that the immobilisation of BPF in different polymeric film matrixes could affect their physicochemical properties, but they could still effectively monitor the quality of perishable food in real-time. In conclusion, the development of intelligent films employing BPF's anthocyanins is a potential strategy for the future of food packaging systems.