Akademik Veri Yönetim Sistemi
Tezin Türü: Yüksek Lisans
Tezin Yürütüldüğü Kurum: Wageningen Universiteit, VLAG Graduate School, Food Process Engineering, Hollanda
Tezin Onay Tarihi: 2022
Tezin Dili: İngilizce
Öğrenci: Viktoria Mayr
Danışman: Murat Yanat
Özet:
Objective
The addition of nanoparticles into biodegradable films has been found to improve their
properties in many aspects. Chitin and chitosan are non-toxic polysaccharides, which
possess naturally antimicrobial activities against a wide spectrum of microorganisms. Thus,
they are interesting particles for creating antimicrobial food packaging. The antimicrobial
activities of chitin and chitosan nanoparticles in form of suspensions and reinforced
polylactic acid (PLA) nanocomposites, have been studied on food spoilage bacteria;
Lactobacillus plantarum and Pseudomonas fragi.
Method
Chitin and chitosan nanoparticles were produced by acid hydrolysis and ionic gelation,
respectively. Their particle size distribution and zeta potential were determined by dynamic
and electrophoretic light scattering. PLA nanocomposites were produced by solvent casting.
The diffusion of nanoparticles, in form of suspensions, was assessed by the agar diffusion
method. The antimicrobial properties of nanosuspensions and PLA nanocomposites were
tested via agar spot method and liquid incubation.
Results
Chitin and chitosan nanoparticles had a mean Z-average diameter of 0.390 μm and 1.45
μm and zeta potentials of 32.2 mV and 29.5 mV. Their corresponding powders showed
mean Z-average values of 102 and 298 μm with zeta potentials of 16.8 and 12 mV. 10 -
20 mg/mL concentrations of chitin and chitosan powders did not result in clear inhibition
zones for L. plantarum and Ps. fragi after 48 h incubation. Chitin nanoparticles in the
concentrations 1-20 mg/mL did not affect the growth of L. plantarum. Ps. fragi showed at
concentrations 5 -20 mg/mL signs of inhibition during the agar spot method. Growth of L.
plantarum was inhibited for at least 48 h by chitosan nanoparticles with concentrations >
0.2 mg/mL. Ps. fragi showed lower sensitivities to chitosan and needed concentrations ≥
3 mg/mL for an inhibition of 72 h. During liquid incubation, chitin nanoparticles were not
found to affect growth of Ps. fragi. Chitin and chitosan PLA nanocomposites showed no
antimicrobial activity on L. plantarum nor Ps. fragi.
Conclusion
Chitosan nanoparticles' antimicrobial effects on L. plantarum were enhanced because of
the bacteria-induced pH drop during liquid incubation. Gram-positive and Gram-negative
bacteria might obey different mechanisms since Ps. fragi showed signs of inhibition for
chitin nanoparticles. The chosen methods for testing PLA nanocomposites might not be
suitable or need revision. Based on experiments with nanosuspensions, the highest
potential for chitosan reinforced PLA nanocomposites is seen in the packaging of acidic
food items since low pH values were found to enhance the antimicrobial properties.