Figs - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 450

ripen and partially dry on the tree before harvesting and
completion of drying to about 17% moisture using either
solar drying or a dehydrator at 60 ◦ C (140 ◦ F) (Crisosto and
Kader, 2009).

solar installations for drying 'Kadota' figs was examined
by El-Razik et al. (2000) using various process parameters
and compared with sun drying. The solar drying was 2.5-3
times faster than the traditional method; however, the sun-
dried fruit received better sensory scores. Both sun-dried
and solar-dried samples were found positive to aflatoxin B 1 ,
although the concentrations were below the US Food and
Drug Administration's limit (El-Razik et al., 2000). How-
ever, Ozay et al. (1995) reported the reduction of aflatoxin
contamination level by using solar drying.
A simple and inexpensive solar dryer designed in In-
dia was reported not only to expedite drying but to im-
prove quality of 'Bellary' figs (Raghupathy et al., 1998).
Solar tunnel dryer developed at Hohenheim University
(Germany) and comprising light-powered fans were ap-
pliedinTurkeyoncommercialscale(GreenandSchwarz,
2001) and were reported to improve microbiological qual-
ity of dried figs (Ural, 1997). Chimi et al. (2008) have
recently reported good performance of a newly developed
solar technique for industrial fig drying in Morocco; for
solar-dried figs, the results in all cases showed lower dry-
ing time, cleaner product with longer storage and shelf life,
better flavor retention, and more attractive appearance than
the sun-dried fruit and the absence of mycotoxines (Chimi,
2009). Despite better results, literature shows that the scope
of commercial application of solar technologies in fig dry-
ing is rather limited (Green and Schwarz, 2001).

Traditional sun drying
The procedures of sun drying of fig fruit have been de-
scribed by Aksoy (1997) and Ural (1997). The semidry
figs collected from the ground are placed in one layer on
wooden drying trays. These trays are positioned in a special
part of the orchard, usually located in a sun-exposed open
area away from dust and potential sources of infection (e.g.,
toilets) but not far from a shelter (warehouse) used for stor-
ing the dried fruit in piles or sacks. During sun drying, each
fig is periodically turned from one side to the other until
water content of 18-22% is reached, typically, in 3-5 days,
depending on the weather.
The effects of ambient temperature and solar radiation on
the efficacy of fruit sun drying were investigated by Togrul
and Pehlivan (2004) using mathematical modeling. Zare
and Taghyzadeh (2009) reported that based on sensing and
quality tests, the best method of drying fig in Iran was found
to be under a partial shade, however, drying in sun was the
best method with respect to the quality of fruit color.
The main problem with the sun drying of figs is the high
risk of fruit infestation with pests and pathogens due to its
contact with soil and prolonged exposure to open environ-
ment. The major concern is colonization of the sun-dried
figs with toxinogenic molds, such as Aspergillus flavus
and A. parasiticus, resulting in the presence of poisonous
and carcinogenic mycotoxins (e.g., aflatoxin) in the fruit
(Flaishman et al., 2008).

Mechanical dehydration
The use of commercial equipment (e.g., automated de-
hydrator with airflow tunnels) is another alternative to
the conventional sun drying. Its advantages include food
safety, controllable and uniform technological parameters,
fast process, and lower labor demand (Piga et al., 2004).
However, the process parameters for dehydration (airflow,
temperature, drying time) must be optimized for uniform
quality in dried figs (Ertekin et al., 2003). Drying figs of
cultivar 'Niedda Longa' in a commercial two-stage dehy-
dration system was studied by Papoff et al. (1998) in com-
parison with simulated sun drying. The study showed that a
7 hour processing gave a ready-to-market product provided
that figs were pretreated with potassium sorbate. Similar
quality was attained after simulated 120 hours sun drying.
Extension of industrial dehydration beyond 11 hours gave
a product not requiring chemical additives for its preserva-
tion. However, rehydration was needed to ensure appropri-
ate fruit palatability (Flaishman et al., 2008).
Dehydration of figs of nonspecified local Sardinian cul-
tivar in tangential airflow cabinet allowed complete control
of process parameters in sanitary conditions and gave a

Solar drying
For solar drying of figs, the predrying treatments may in-
clude blanching in boiling water (normally for 1 min) and/or
sulfuring. These methods, however, are not easily compat-
ible with the traditional technique of sun drying, but they
are often practiced before solar or mechanical dehydra-
tion. The pretreatments accelerate dehydration, control en-
zymatic browning, and may improve its texture and reduce
infestation (Raghupathy et al., 1998; El-Razik et al., 2000;
Gawade and Waskar, 2005; Piga et al., 2004).
Introduction of more sophisticated drying methods is
intended to accelerate dehydration and to limit the fruit
contact with the environment, thus reducing the risk of
contamination. Solar dryers use the same energy source as
the traditional sun drying, but the process is more energy ef-
ficient and conducted within plastic- or glass-covered space
(Flaishman et al., 2008). The performance of two types of