Nano-composite films were developed between silver nanoparticles (Ag NPs) and a low-density polyethylene (LDPE) using master batches by melt extruding and melt compounding. The Ag/PE composite film showed decreased gas permeability, moisture permeability coefficient, the tear strength,
the longitudinal and transverse elongation to that of commercial LDPE. Although stiffness increased at high Ag (40 ppm) concentration, but the longitudinal and transverse tensile strength enhance comparing with commercial PE. Light transmittance and haze were comparable. Both Nano-silver and
composite films are effective against Escherichia coli (E. coli). Antibacterial activity of nano-silver for E. coli was determined by diameter of the inhibition zone and the minimum inhibitory concentration of nano-silver is detected by tube double dilution method reaching
15.63 ppm. The composite films are effective inhibition of E. coli at concentrations of 40 ppm Ag nanoparticles. Moreover, Nano-silver migration occurs in composite film. One-side migration was conducted to detect under three food simulants (3% acetic acid, 50% ethanol and distilled
water) at three degree of temperature (25 °C, 40 °C and 70 °C) on different period of time (2, 4, 6, 8, 10 and 12 hours). These results indicated that the highest migration amount was obtained with 3% acetic acid following distilled water and finally 50% ethanol under same conditions.
The migration level is dependent upon time and temperature and high migration time and temperature can enhance migration level. These findings demonstrate that nano-silver-containing polyethylene composite film may have a great potential for developing antibacterial and acid food packaging
system.
The self-assembly
of a nonionic triblock copolymer (F127) and a
nonionic surfactant (HS15) has been investigated due to favorable
changes in properties in their mixtures. The effect of the mixing
ratio on the self-assembly process and on the structural stability
of the mixtures was studied by coarse-grained molecular dynamic simulation
(CGMD) and experimental measurements (transmission electron microscopy,
dynamic light scattering measurement, drug loading stability analysis,
and fluorescence spectroscopy measurement). The CGMD provided the
information on self-assembly behavior. The microstructure and micellar
stability are affected by different proportions of F127/HS15. Pure
HS15 molecules (system I) can rapidly form stable aggregates driven
by strong hydrophobic force, including two steps: the formation of
seed clusters and the fusion of them. At low F127 ratio (system II),
the self-assembly process is dynamic unstable, and a volatile “coil/cluster-like”
aggregate is formed under the single “binding” effect.
As the ratio of added F127 increase, such as system III, stable “lotus-seedpod-like”
aggregates form under the double effects of “binding plus wrapping”.
Its dynamic equilibrium can be achieved rapidly. The experimental
results approved the assumption of “different mixing ratio
with different structural stability” and even different loading
stability of F127/HS15 systems for drugs with different log P, such as PUE and DTX, which means different loading area
for them in the micellar systems at different mixing ratios because
of less hydrophobic microdomains with the increase of F127 molecules.
Nano-composite film possesses antibacterial properties of nanomaterials and preservation performance of food packaging film. The goal of this work was to explore the potential application of nano-silver-containing polyvinyl alcohol (PVA) composite film in grape fresh-keeping. Mechanical
properties, transparency, barrier performance and antibacterial activity of Nano-silver-containing PVA film were tested and results showed that the antibacterial zone diameter of nano-silver on Aspergillus niger was 14.4 mm, with minimum bactericidal concentration of 75 ppm. The PVA
antibacterial membrane effectively revealed antibacterial properties. Moreover, the decreased mechanical properties and transparency enhanced barrier performance of antibacterial membrane compared with PVA film. For comparison, the fresh-keeping effects of non-packaging film, commercial cling
wrap and nano-silver-containing PVA film on sensory score, mass loss rate, decay rate, Ascorbic Acid (Vc) content and titratable acid content were also studied. Results indicated that the PVA antibacterial membrane significantly effectively avoided sensory score, water, decay, Ascorbic Acid
(Vc) and titratable acid in grapes during storage, and had a remarkable effect in prolonging grapes' shelf life due to its breathability and antibacterial activity.
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