Antagonistic effects of essential oils from selected Malaysian herbs and spices against spoilage and mycotoxigenic fungi on food packaging application
Essential oils (EO) have a long history and wide application. Although EO of various herbs and spices from other parts of the world have shown antifungal effects, those from Malaysian herbs and spices remain underreported; thus, they can be further utilised in the search for novel bioactive compo...
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Format: | Thesis |
Language: | English |
Published: |
2022
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Subjects: | |
Online Access: | http://psasir.upm.edu.my/id/eprint/105511/1/MAZLIZA%20BINTI%20RAMLI%20-%20IR.pdf |
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Summary: | Essential oils (EO) have a long history and wide application. Although EO of
various herbs and spices from other parts of the world have shown antifungal
effects, those from Malaysian herbs and spices remain underreported; thus, they
can be further utilised in the search for novel bioactive compounds as natural
antifungals to fulfil the consumers' demand for greener, safer, healthier, and
higher‐quality foods with longer shelf life. Therefore, the objectives of the present
work were (i) to investigate the fungicidal and fungistatic potentials of commercial
EO from selected Malaysian herbs and spices against common spoilage and
mycotoxigenic fungi; and (ii) to examine mycotoxin prevention and reduction in
peanut through the incorporation of the most potent EO in food packaging
system. Essential oils from ten herbs and spices (betel, cinnamon, clove,
coriander, galangal, ginger, lemongrass, lime, nutmeg, turmeric) were analysed
against five common foodborne spoilage and mycotoxigenic fungi; which were
Aspergillus flavus, A. parasiticus, A. niger, Fusarium verticillioides, and F.
incarnatum. Fungal isolates were obtained from common household food
products (maize and peanuts), and isolated by the culture method. Molecular
identification of the fungal isolates was performed using primer pair of the
Internal Transcribed Spacer (ITS) region. The mycotoxigenic potential of fungal
isolates was determined by high performance liquid chromatography with a
fluorescence detector (HPLC-FLD). The EO bioactive compounds were
identified by gas chromatography and mass spectrometry (GC-MS). Preliminary
in vitro screening was conducted with the agar disk diffusion and agar well
diffusion methods on Potato Dextrose Agar (PDA), and microwell assay method
on Potato Dextrose Broth (PDB). Following this, three most potent EO were
selected for their Minimal Inhibitory Concentration (MIC), Minimal Fungicidal
Concentration (MFC), and fungal spore germination test. Molecular identification
confirmed the fungal isolates’ identity with existing species in the GenBank.
Based on HPLC-FLD results, all the fungal isolates were confirmed to be mycotoxigenic based on their ability to produce mycotoxins. Based on GC-MS
results, a total of 120 bioactive compounds were detected from the EO; which
were 26.25% anethole (betel), 63.39% cinnamaldehyde (cinnamon), 87.16%
eugenol (clove), 54.79% linalool (coriander), 29.56% propenoic acid (galangal),
26.32% α-zingiberene (ginger), 42.61% geranial (lemongrass), 39.84%
limonene (lime), 27.80% β-phellandrene (nutmeg), and 41.81% ar-turmerone
(turmeric). Based on preliminary in vitro screening, cinnamon, clove, and
lemongrass EO yielded the highest fungal growth inhibition. Further, cinnamon
EO yielded the lowest MIC, MFC, and spore germination, hence were selected
to be applied in food packaging system. The inhibitory effects of cinnamon EO
were found comparable to the commercial antifungal, cycloheximide. Sachet
including inclusion complexes (ICs; a combination of cinnamon EO and β-
cyclodextrin) by kneading method was prepared, and the fungal growth inhibition
in vitro was determined under different temperature (25°C, 50°C, and 75°C) and
pH values (5.5, 7.4, and 13.0) to see its stability in peanut. The ICs’ antifungal
activity in peanuts was also determined in terms of aflatoxin reduction (peanut
was selected since it is the most commonly colonised food crop commodity by
Aspergillus section Flavi). The prepared ICs showed excellent fungal growth
inhibition in vitro and aflatoxin reduction in peanuts as compared to control
sample. Various temperature levels and pH values did not affect the ICs’ activity. |
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