Bioconversion of Mandarin Orange Peels by Aspergillus oryzae …
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2.4 Gas Chromatography–Mass Spectrometry (GC–MS)
Analysis of Essential Oils of Fresh Mandarin Peel
After extraction of essential oil, the sample was diluted with HPLC-grade 40–60
petroleum ether in 1:100 ratio (v/v). The separation of aroma compounds was carried
out by using an Agilent 7890 GC system with 575C triple axis equipped with selective
mass detector Agilent 5973. A capillary column of HP-5MS (30 m × 0.25 μm ×
10 m duraguard column film thickness) and an automatic injection system were used.
The initial oven temperature was 60 °C. In the splitless mode, the column was held
at 60 °C for 5 min followed by an increase to 150 °C at 3 °C/min temperature rate
and held for 2 min. Finally, the oven temperature was increased to 200 °C at a rate of
5 °C/min and held for 2 min. Finally, column temperature was increased to 260 °C
at a rate of 10 °C/min and then held for 2 min.
2.5 Identification of Volatiles Present in Essential Oils
of Fresh Peel of Mandarin Orange
Individual chromatographic peak identification of volatile components was carried
out by comparing their mass spectra with the mass spectra from NIST 05 library
and WILEY L-built library (Ibrahim et al. 2011). The results were also confirmed
by comparing with previous studies and reviews (Elmaci and Altug 2012). The fragmentation of mass spectra of specific compounds was also identified by comparing
with chromatograms and retention times of the analytes with those from analytical
standards (Adams 1995).
2.6 Spoilage of Mandarin Peel Infected by Aspergillus sp.
(Aspergillus oryzae) and Penicillium sp.
About 100 g of peels from fresh Mandarin mandarins was weighed and smashed.
Then the smashed peel was homogenized at 8000 rpm by homogenizer (REMI
MOTORS-RQ-122). The pH of the resulting mixture solution was adjusted according
to the pH optima of specific fungus. Two sterilized 100-ml Erlenmeyer flasks were
taken and 30 ml of homogenized peel was poured into each of the flasks. Then one
of the flasks was inoculated with the pure fungal strain Aspergillus sp. (Aspergillus
oryzae) and another flask inoculated with the pure fungal strain Penicillium sp. at a
level of 10
7 cells or spores per ml of homogenized peel sample. The flasks were then
incubated at 28 °C for 5 days in incubator.
1 5
2.4 Gas Chromatography–Mass Spectrometry (GC–MS)
Analysis of Essential Oils of Fresh Mandarin Peel
After extraction of essential oil, the sample was diluted with HPLC-grade 40–60
petroleum ether in 1:100 ratio (v/v). The separation of aroma compounds was carried
out by using an Agilent 7890 GC system with 575C triple axis equipped with selective
mass detector Agilent 5973. A capillary column of HP-5MS (30 m × 0.25 μm ×
10 m duraguard column film thickness) and an automatic injection system were used.
The initial oven temperature was 60 °C. In the splitless mode, the column was held
at 60 °C for 5 min followed by an increase to 150 °C at 3 °C/min temperature rate
and held for 2 min. Finally, the oven temperature was increased to 200 °C at a rate of
5 °C/min and held for 2 min. Finally, column temperature was increased to 260 °C
at a rate of 10 °C/min and then held for 2 min.
2.5 Identification of Volatiles Present in Essential Oils
of Fresh Peel of Mandarin Orange
Individual chromatographic peak identification of volatile components was carried
out by comparing their mass spectra with the mass spectra from NIST 05 library
and WILEY L-built library (Ibrahim et al. 2011). The results were also confirmed
by comparing with previous studies and reviews (Elmaci and Altug 2012). The fragmentation of mass spectra of specific compounds was also identified by comparing
with chromatograms and retention times of the analytes with those from analytical
standards (Adams 1995).
2.6 Spoilage of Mandarin Peel Infected by Aspergillus sp.
(Aspergillus oryzae) and Penicillium sp.
About 100 g of peels from fresh Mandarin mandarins was weighed and smashed.
Then the smashed peel was homogenized at 8000 rpm by homogenizer (REMI
MOTORS-RQ-122). The pH of the resulting mixture solution was adjusted according
to the pH optima of specific fungus. Two sterilized 100-ml Erlenmeyer flasks were
taken and 30 ml of homogenized peel was poured into each of the flasks. Then one
of the flasks was inoculated with the pure fungal strain Aspergillus sp. (Aspergillus
oryzae) and another flask inoculated with the pure fungal strain Penicillium sp. at a
level of 10
7 cells or spores per ml of homogenized peel sample. The flasks were then
incubated at 28 °C for 5 days in incubator.