Advances in Food Mycology

186 Beatriz T. Iamanaka et al.
Figure 1 shows the total numbers of black Aspergillus species
isolated from each type of sample and the numbers of isolates
producing OA. Of 264 isolates from black sultanas, only 6.1% were
toxigenic, whereas in dates 68.4% of black Aspergilli were toxigenic.
Plums and figs yielded 84 and 43 isolates, of which 28 (33.3%)
and 11 (25.6%) were toxigenic, respectively. Studies on dried fruits
have shown that these products are commonly contaminated with
black Aspergilli such as A. carbonarius, A. niger and related species
(King et al., 1981; Abarca et al., 2003). Apricots were not contaminated
with ochratoxigenic fungi because the use of high levels of
sulphur dioxide to preserve colour renders dried apricots essentially
sterile.
Abarca et al. (2003) isolated black Aspergilli from 98% of dried fruit
samples (currants, raisins and sultanas). They found that 96.7% of
A. carbonarius and 0.6% of A niger isolates produced OA, indicating
that among black Aspergilli, A. carbonarius was the most probable
source of this toxin in these substrates in Spain. However, Da Rocha
Rosa et al. (2002) found a higher percentage of A. niger producing OA
in grapes from Argentina (17%) and Brazil (30%). Only A. carbonarius
was found in Brazilian grapes and only eight isolates (25%) were
able to produce this toxin.
In the present study, the high incidence of toxigenic black Aspergilli
in dates, plums and figs is of concern, but only a few isolates were
identified as A. carbonarius. Compared with studies that have been
carried out in several parts of the world (Heenan et al., 1998; Da
Rocha Rosa et al., 2002; Abarca et al., 2003; Battilani et al., 2003), the
results presented here differ significantly because they show a higher
percentage of black Aspergilli other than A. carbonarius producing
OA.
Figure 2 shows the numbers of A. ochraceus found in dried fruits.
A. ochraceus contamination was not high, only 27 isolates were found
in black sultanas, dates and plums, however 52% of the isolates were
toxigenic. Most of isolates from black sultanas and plums produce
OA; 80% and 100%, respectively. From dates, only one of 12 isolates
was toxigenic. A. ochraceus was not found in white sultanas, apricots
or figs.
In general, the presence of OA in dried fruits was related to contamination
by black Aspergilli and the major incidence occurred in
black sultanas, figs and dates.