3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Food Chemistry & Biotechnology
identically as described in our previous papers, involving the
DPPH, TBARS and FRP assays. Total phenolic compounds
content of extracts was evaluated, as well. 9, 11
M u l t i v a r i a t e S t a t i s t i c a l A n a l y s i s
Canonical discriminant analysis of all results obtained
from UV-VIS experiments was performed using the Unistat ®
software in order to distinguish the native (non-irradiated)
spice samples from that exposed to γ-radiation.
Results
Microbiological analysis performed immediately after
the irradiation process proved, that as a result of γ-irradiation,
the total count of microorganisms in caraway sample irradiated
at dose of 5kGy decreased considerably from 2.8 × 10 4
colony forming unit (CFU) detected in reference sample, to
less than 10 CFU g –1 . The same effect of γ-irradiation on laurel
leaves was achieved using the dose of 10 kGy, still fulfilling
the requirements of international standards on irradiation
3,4 .
Table I
Microbiological analysis of ground caraway seeds (C) and
laurel bay leaves (L) samples, γ-irradiated at doses of
kGy using 60Co-source performed one day after the γ-irradiation
Radiation Total count of
dose microorganisms
Coliform
bacteria
Moulds
[CFU g –1 [kGy] [CFU g
]
–1 ] [CFU g –1 ]
C L C L C L
0 2.8 × 10 4 1.7 × 10 5 1.0 × 10 4 8.6 × 10 3 9.8 × 10 3 5.7 × 10 3
5 < 10 5.7 × 10 3 < 10 5.0 × 10 1 2.5 × 10 2 < 10
10 < 10 < 10 < 10 < 10 < 10 < 10
20 < 10 < 10 < 10 < 10 < 10 < 10
30 < 10 < 10 < 10 < 10 < 10 < 10
As follows from data presented in Table I, the presence of
oliform bacteria as well as of yields and moulds was effectively
suppressed by the irradiation. Analysis performed 6 months of
post-irradiation storage confirmed, that microbial status of both
spices remained practically unchanged.
EPR spectrum of both reference (non-irradiated) samples
represents broad singlet line with unresolved hyperfine splitting,
attributable mostly to Mn 2+ ions, upon which the additional sharp
EPR line (g eff = 2.0022, ∆B pp ~ 1 mT) is superimposed, previously
assigned to stable semiquinone radicals produced by the
oxidation of polyphenolic compounds present in plants. In addition,
the presence of low-intensive EPR singlet line was noticed
in caraway reference sample, attributable to radicals generated
during the grinding process (Table II). 5,9–11
EPR spectra of γ-radiation treated spices showed the formation
of additional paramagnetic structures. As follows from
detail simulation analysis of obtained spectra (Table II), different,
mostly cellulosic and carbohydrate radical structures were
identified.
s561
Table II
Identification of radical structures found in reference and
γ-irradiated samples of ground caraway and laurel leaves
EPR signal g-value Hyperfine ΔB pp [mT]
origin splittings [mT]
Reference samples
Semiquinones g ┴ = 2.0042 – 0.52
g ║ = 2.0030
Carbohydrate I g ┴ = 2.0041 – 0.06
g ║ = 2.0028
γ- irradiated samples
Carbohydrate II g ┴ = 2.0041 A ┴ = 0.7 0.45
g ║ = 2.0033 A ║ = 0.6 (2H)
Carbohydrate III g ┴ = 2.0032 A ┴ = 0.85 0.67
g ║ = 2.0025 A ║ = 0.7 (2H)
Carbohydrate IV g ┴ = 2.0030 A ┴ = 0.45 0.59
g ║ = 2.0038 A ║ = 0.40 (1H)
Cellulosic g ┴ = 2.0029 A ┴ = 3.00 1.20
g ║ = 2.0014 A ║ = 1.70 (2H)
Integral EPR intensity
8
7
6
5
4
3
2
1
March
April
May
June
0 5 10 15 20 25 30
Radiation dose, kGy
Fig. 1. Dependence of integral EPR intensity of ground caraway
seed on γ-radiation dose measured immediately after
the irradiation (March) and during three month of post irradiation
storage (April-june). EPR spectra were recorded using
0.633 mw microwave power at 298 K
These radicals originate either from cleavage processes
of cellulose matter (laurel leaves) and/or of other polysaccharides
forming the skeleton of plant structures and their cells,
as the cellulosic radicals were not detected in γ-irradiated caraway
samples.
In accord with our previously published papers, the
dose-dependent formation of radical structures’ in γ-irradiated
samples of both spices under study was found (Fig. 1.).