| dc.description.abstract | Background: Biodegradable active packaging films, is used to improve the quality,
increasing shelf-life, controlling pathogens, and improving organoleptic properties
of foodstuff. The present study was conducted to evaluate the effects of CNF, TiO2,
and REO in combination, on antibacterial, physicomechanical and apparent
properties of whey protein film. Also, with covering of food model sample (meat)
with the prepared film and its effects, including microbial changes and sensory
characteristics, during 15 days of storage at the refrigerated temperature, were
investigated
Material and Methods: To detect REO chemical compounds, a gas
chromatography coupled with a mass spectrometer method was used. Films with
different contents, including:
1. WPI (10%)
2. WPI/CNF (2.5-5-7.5- 10%)
3. WPI/CNF/TiO2 (0.5-1-1.5%)
4. WPI/CNF/REO (1.5-2%)
5. WPI/CNF/TiO2/REO
were prepared. The physicomechanical traits characteristics of the films, including
tensile test, apparent properties, nanoparticle distribution by SEM, XRD, FTIR,
water vapor permeability, transparency, thickness, moisture content, and solubility
percent, were valuated. Based on optimum antimicrobial activities and
physicomechanical features, the best film was selected. Then the meat pieces were
covered with this film and were kept at the refrigerated for 15 days. Microbiological
evaluations were performed through counting Pseudomonas, aerobic mesophilic
bacteria, Enterobacteriaceae, Listeria monocytogenes, Escherichia coli in the time
intervals of 0, 3, 6, 9, 12, and 15 days. All experiments were carried out in three
replications.Results: WPI-CNF composite films without antimicrobial compounds did not
indicate any inhibitory effect on the tested bacteria. Films, containing TiO2 and
REO had the highest impact on gram-positive bacteria, especially Listeria
monocytogenes. The results of tensile and mechanical strength tests of films
showed that, addition of CNF to the protein matrix improved the mechanical
properties of the protein film, and the best concentration was chosen 7.5% CNF.
On the other hand, the addition of TiO2 and REO to the WPI / CNF film, also
significantly, improved the physicomechanical properties of the resulted films. By
increasing the concentration of nanoparticles and essential oils in films, the
transparency of the films was reduced and also samples thickness showed that, the
addition of each of the compounds did not have a significant effect on this index.
Finally, based on the results, the protein film with 7.5% CNF + 1% TiO2 + 2% REO
as the selected film for meat packaging was used. The results of microbial load
determination showed that the population of aerobic mesophilic bacteria,
Enterobacteriaceae, and Pseudomonas in meat samples decreased significantly
compared to control group until the day 15th. On the other hand, the nanocomposite
film caused reducing of 3.6 (Escherichia coli) and 3.8 (Listeria monocytogenes)
logarithmic cycles in the bacterial population at the end of 15 days of storage
compared to the uncoated control group.
Conclusion: This study showed that WPI-CNF-TiO2-REO nanocomposite film
have a good synergistic effect on inhibiting the bacterial growth. Also, by
improving some physicomechanical and sensory properties, the film can be used
for packaging foods as well as increasing the meat shelf-life | en_US |
