APTEFF, 38, 1-190 (2007)
DOI:10.2298/APT0738029K
UDC: 664.5:579.67:582.28
BIBLID: 1450-7188 (2007) 38, 29-35
Original scientific paper
CONTAMINATION OF SPICES WITH MOULDS
POTENTIAL PRODUCERS OF STERIGMATOCYSTINE
Sunica D. Koci-Tanackov, Gordana R. Dimi and Dragana Karali
The presence of moulds, potential producers of sterigmatocystine, was investigated in
20 samples of spices (cinnamon, caraway, marjoram and clove). The following five species were isolated from the samples: Aspergillus versicolor, Aspergillus sydowii, Aspergillus ustus, Emericella nidulans and Eurotium herbariorum. E. herbariorum was present in
all the investigated spice samples, accounting for 7.6% of total mycopopulation in
caraway and 42.9% in cloves. A. versicolor was detected in cinnamon, caraway and
marjoram, accounting for 0.4% of total mycopopulation in caraway and 1.5% in cinnamon; A. ustus accounted for 0.1% of total mycopopulation in caraway and 0.4% in
marjoram, while A. sydowii accounted for 18.9% of total mycopopulation in marjoram
and 7.1% in clove. E. nidulans was a contaminant of caraway (0.01%) and marjoram
(0.4%).
KEY WORDS: Moulds, producers of sterigmatocystine, spices
INTRODUCTION
Spices have been used in many industries, with the food industry and catering being
predominant users. Having been dried material from plant origin, spices are commonly
heavily contaminated with xerophilic storage moulds and bacteria (1, 2, 3). The most
frequent fungal contaminants of spices are species from the genera Aspergillus and Penicillium (4, 5, 6, 7).
Some species that belong to these genera are known as potential producers of different toxic substances such as aflatoxins, ochratoxins and sterigmatocystine, i.e. mycotoxins that exhibit toxic, mutagenic, teratogenic and carcinogenic effects in humans and
animals (8, 9).
Sterigmatocystine (ST) has a chemical structure similar to hepatocarcinogenic aflatoxin B1 but exhibits lower toxicity. However, in nature, it prevails at much higher con-
Sunica Koci-Tanackov, M. Sc., Assist., Dr Gordana Dimi, Assoc. Prof.,Faculty of Technology, 21000 Novi
Sad, Bulevar Cara Lazara 1, Serbia, Dragana Karali, Biology, Yugoremedia ad., Panevaka bb, 23000
Zrenjanin, Serbia
29
centrations (10). The predominant ST producers are the species from the genera Aspergillus (A. versicolor, A. sydowii, A. ustus, A. glaucus), Eurotium (E. herbariorum) and
Emericella (E. nidulans, E. venezuelensis) (9, 11). Spices are potential contaminants of
food, causing its deterioration (12). Mycotoxins synthesized by moulds in spices pose an
important health risk in the end-products, being so resistant (degrade at 265oC) (13) that
cannot be eliminated during food processing.
This paper aims at assessing the intensity of mould contamination in spices, the presence and frequency of moulds, potential producers of sterigmatocystine.
EXPERIMENTAL
Spices
Four spices (cinnamon, caraway, marjoram and clove) originating from different
manufacturers, were sampled from local food stores. Five samples from each spice were
provided.
Mycological analyses
Total fungal count was determined by dilution method according to Koch, using two
media: Saboraud-malt agar (SMA) and malt yeast agar with 50% glucose (MY50G). To
inhibit bacterial growth, antibiotics were added to SMA medium (1% aqueous solution of
chloramphenicol and 1% aqueous solution of oxytetracycline, 1 ml/100 ml medium). The
inoculated Petri dishes were incubated at 25oC for 7 days.
The isolated moulds were determined according to determination patterns described
by Samson and van Reenen-Hoekstra (14).
RESULTS AND DISCUSSION
Mould contamination occurred in all of the investigated samples. Total mould count
in spices was: caraway - 4.2×105 cfu/g, marjoram - 2.6×105 cfu/g, cinnamon - 2.2×105
cfu/g and clove - 70 cfu/g. As seen in Fig. 1, the highest contamination was detected in
the caraway samples (46.7%) while the lowest contamination was in the clove samples
(0.1%).
contamination %
50
40
30
20
10
0
cinnamon
caraway
marjoram
clove
Fig. 1. Spice contamination by moulds
30
The level of mould contamination in spices depends largely on the environmental
conditions during cultivation, processing, etc.
Mould species that produce ST and their distribution in the observed samples are displayed in Figures 2, 3, 4 and 5.
Two toxigenic species, A. versicolor and E. herbariorum were isolated from the cinnamon samples (Fig. 2). A. versicolor was detected in one cinnamon sample (accounting
for 5% of total mycopopulation) and E. herbariorum occurred in all five samples with
frequencies ranging from 1% to 27%.
A. versicolor
E herbariorum
Other species
100%
frequency
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
U1
U2
U3
U4
U5
samples
Fig. 2. Distribution of ST producers in the cinnamon samples
Beside A. versicolor and E. herbariorum, A. ustus and E. nidulans were found to contaminate the caraway samples (Fig. 3). In this case either, E. herbariorum was the dominating contaminant, being present in all of the observed samples with higher frequency
than that in cinnamon (from 5% to 32%). A. versicolor was detected in three samples,
accounting for 1% to 6% of the total mould population, while A. ustus and E. nidulans
were present in one sample (0.2% and 8% of total mycopopulation, respectively).
A. versicolor
A. ustus
E herbariorum
Other spices
E. nidulans
100%
frequency
80%
60%
40%
20%
0%
U1
U2
U3
U4
U5
samples
Fig. 3. Distribution of ST producers in caraway samples
31
Marjoram was contaminated with five producers of ST. The most frequent species
was E. herbariorum, from 3% to 51% of the total mycopopulation. Regarding species
from the genus Aspergillus, the following were isolated: A. versicolor, A. sydowii and A.
ustus. The proportions of these mould species in the total mould populations were as
follows: 2%-24% for A. sydowii, 1%-11% for A. versicolor and 1%-2% for A. ustus. A.
sydowii and A. ustus were found in four samples and A. versicolor in three. Two samples
of marjoram were found to contain E. nidulans in low proportions (Fig. 4).
A. sydowii
A. versicolor
A. ustus
E. nidulans
E herbariorum
Other species
90%
80%
frequency
70%
60%
50%
40%
30%
20%
10%
0%
U1
U2
U3
U4
U5
samples
Fig. 4. Distribution of ST producers in marjoram samples
Examining the mycopopulation composition in clove revealed that the ST producing
moulds were present in four samples (Fig. 5). These were E. herbariorum and A. Sydowii.
In two clove samples, E. herbariorum was found to be the only moulds contaminant. The
clove sample was the least mould- contaminated spice. Clove is well known for its
antimicrobial properties with essential oils highly effective against moulds, similarly to
those of thyme and mustard (15, 16).
A. sydowii
E herbariorum
Other species
100%
90%
frequency
80%
70%
60%
50%
40%
30%
20%
10%
0%
U1
U2
U3
U4
U5
samples
Fig. 5. Distribution of ST producers in clove samples
32
The predominating mould species in the total mycopopulations was E. herbariorum,
which was present in all of the examined spice samples with frequencies in the total
mould populations ranging from 7.6% for caraway to 42.9% for clove (Fig. 6). Its high
prevalence is presumably due to low water activity (aw) required for growth (0.72 aw)
(17). Of the ST-producing moulds detected in the samples, E. herbariorum was the most
xerophilic one.
45%
40%
35%
30%
25%
20%
15%
10%
5%
0%
Caraway
Cinnamon
A
.s
yd
A
ow
.v
ii
er
si
co
lo
r
A
.u
st
us
E.
ni
du
E
la
he
ns
rb
ar
io
ru
m
Clove
Majoram
Fig. 6. Distribution of ST producers in the spices samples
The second most frequent species was A. sydowii (7.1% in clove, 18.9% in marjoram), followed by A. versicolor (0.4% in caraway, 1.5% in cinnamon), A. ustus (0.1% in
caraway, 0.4% in marjoram) and E. nidulans (0.01% in caraway and 0.4% in marjoram).
According to the study reported by Dimi et al. (2), samples of pepper, paprika, and spice
blends were frequently contaminated with E. herbariorum and A. versicolor. They
synthesized ST at levels ranging from 100.0 μg/l to 400.0 μg/l (E. herbariorum), and
from 100.0 μg/l to 1600.0 μg/l (A. versicolor). In fact, these mould species are associated
with low moisture food deterioration (18, 19, 20, 21).
CONCLUSION
The present investigation documented the significant occurrence of potential toxigenic moulds in spices that are potential producers of not only ST but other harmful metabolites such as tremotrin, penicillinic and cyclopiazonic acid. Their presence should be
controlled during all processing steps – plant growth, transport, drying and storage. One
of the preventive measures could be the control of water activity in spices. Water activity
under 0.70 inhibition the growth of these mould species.
33
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. -
, . 20 (
, , ) (). : Aspergillus versicolor, Aspergillus sydowii, Aspergillus ustus, Emericella
nidulans Eurotium herbariorum. E. herbariorum !" # 7,6% () # 42,9% (
).
$# #
#
Aspergillus, A. versicolor #
, !" # 0,4% () # 1,5% (), A. ustus # (0,1%)
(0,4%), A. sydowii # (18,9%) (7,1%). E.
nidulans a (0,01%) (0,4%).
Received 25 June 2007
Accepted 15 October 2007
35