الفهرس 
Food contaminationOnly 14 pages are availabe for public view
 |  | from | 241 |  |  |
| | | from | 241 | | |
Abstract
Hanem Ahmed Abd-Elalim Megahed: Utilization of Nano Chitosan
as Inhibitor of Fusarium Growth in Foods. Unpublished Ph.D.
Thesis, Department of Food Science, Faculty of Agriculture, Ain
Shams University, 2017.
Fusarium species are well-known plant pathogens and food
contaminants and they appeared as one of the most important groups of
medically significant fungi. Of these species of fungi, Fusarium
graminearum infects corn and other cereal crops causing the reduction of
yield and quality. It has the ability to produce zearalenone (ZEN) which is
an estrogenic mycotoxin causes severe health hazards to human and
animals. The current study was conducted to prepare and characterize
chitosan nanoparticles (COS-NPs), determine its antifungal activity
against different isolated fungi in particular its effect on the growth of
Fusarium graminearum and ZEN production. The inhibitory effect of
different concentrations of COS-NPs on fungal growth and ZEN
production in talbina prepared from contaminated barley flour and on the
shelf life of stored apple were also studied. Moreover, the safety of COSNPs
and its protective role against ZEN toxicity was conducted in
laboratory animals. Chitosan (COS) was purified and the molecular
weight and the degree of deacetylation were carried out. COS-NPs were
prepared and its particles size and morphology characterization were
determined. The antifungal effect of different concentrations of COS-NPs
was determined against fungi isolated from corn grain through the
mycelium growth inhibition and agar well diffusion methods. The results
of evaluation and characterization of COS revealed that the deacetylation
degree (DD) was 86.9 ± 0.44 %, the average of molar mass was 171.41 ±
0.29 g/mol, molecular weight was 244 ± 7 kDa and the concentration of
free amino groups was 0.05 ± 0.019 mol/L. The Scanning Electron
Microscopy (SEM) showed the nanorod form of COS-NPs. The particle
size of COS-NPs was around 180 nm and the zeta potential was + 70.9 ±
2.4 mV. The FT-IR spectra revealed that COS-NPs appeared at 1256/cm
and the intensity of (NH2) band at 1628/ cm found in COS was decreased
dramatically and a new sorption band at 1550/ cm. COS-NPs showed an
excellent antifungal activity against six out of seven species of fungi
isolated from corn grains included Alternaria tenuis, Aspergillus niger, A.
terreus, Baeuvaria bassiana, Fusarium graminearum, F. oxysporum in a
dose dependent manner however; Sclerotium rolfsii was resistant to
COS-NPs at all tested doses. At a concentration of 800 mg/L, COS-NPs
completely inhibited ZEN production by F. graminearum in PDA
medium. Moreover, at a concentration of 200 and 400 mg/L, it succeeded
to prevent the fungal spoilage of apple fruits during cooling storage
period up to 3 week. On the other hand, COS-NPs at a concentration as
low as 200 mg/L succeeded to induce complete inhibition of Fusarium
graminearum growth and ZEN production in talbina. The biological
evaluation revealed that animals treated with ZEN showed severe toxicity
in the liver, kidney and testes. Addition of COS-NPs at low dose (0.5 mg/
kg b.w) or high dose (1 mg/kg b.w) did not induce any toxicity in
experimental animals and succeeded to protect against ZEN toxicity in a
dose dependent manner through the restoration of most of the tested
parameters. An improvement of histological and histochemical pictures of
the liver, kidney and testes was also occurred.
Key words: Fusarium graminearum; food contaminants; chitosan
nanoparticles; antifungal; antimicrobial; zearalenone;
mycotoxins; oxidative stress; antioxidant; gene
expression.