Sample origin and characteristics
Analyses were performed on two lots of pears (Pyrus
communis L. var. S. Bartolomeu), corresponding to two
drying seasons, 2008 and 2009. Each lot was composed by
fresh pear fruits and traditionally dried fruits (direct
exposure to solar radiation) (Traditional). The samples
from 2009 were also processed using three different
methodologies: in a large glass greenhouse with air convection
(GH1), in a small greenhouse with natural convection
(GH2) and using a hot air tunnel in the absence of
light (HAT). All fruits were harvested in an orchard located
638 Eur Food Res Technol (2011) 233:637–646
123
at the village of Ervedal da Beira (Oliveira do Hospital,
Portugal) at the commercial maturity stage (Fig. 1a). On
average, the fresh fruits had a mass of 64 g, with a diameter
of 4.3 cm and height of 6.5 cm. The moisture content was
78%.
For fresh pear analysis, some fruits were frozen just
after harvesting. The remaining fruits were processed
according to the different methodologies under study.
According to the traditional sun-drying process, the
fresh fruits were peeled and allowed to dry in an open
space with sunshine incidence, as described by Ferreira
et al. [5] (Fig. 1b). After being peeled, fresh pears were
also allowed to dry in two greenhouses that differed in their
size, structure and location. GH1 was provided with air
convection, with a flux of 900 m3 h-1, it was located at
ground level and, in comparison to GH2, had the largest
cargo capacity. Its area was 6.3 m2 (3.19 m long by 1.93 m
wide), and the height in the sides was 1.24 m, whereas in
the middle was 1.97 m. The structure was aluminium with
horticulture glass and there were two roof windows for air
extraction. The drying time for GH1 was approximately
7 days (Fig. 1c). The GH2 greenhouse consisted of insulated
glass panels and had the form of a box (1.20 m height
by 1.20 m long and 1.00 m wide). Inside, it was composed
by a U-shaped structure, parallel to the floor, where pears
were let to dry. GH2 was located on a roof of a building
and contained a step structure coated with reflective film,
where pears were allowed to dry. This interior structure
allowed a greater incidence of the light and consequently
promoted the drying process by natural air convection, with
the air entering in the lower level (first step) and leaving in
the higher level, by means of a girandole. The drying time
for GH2 was approximately 5 days (Fig. 1d), 2 days less
that the drying time of GH1.
For hot air tunnel drying (HAT), after peeled, pears were
let to dry at a constant temperature of 40 C and an air flow
of 1.2 m s-1 for about 7 days (Fig. 1e). The drying tunnel
was 2 m long, and the air convection was promoted by a
ventilator placed at the entrance of the tunnel. In this
structure, pears were not exposed to light, although the air
was heated by a solar collector, and therefore the sun was
also the main source of energy.
Independently of the type of processing used, the processed
fruits reached a mass of 10–14 g with a moisture
content of 20% and had a maximum width of 2.5–3.4 cm,
height of 3.9–4.7 cm and thickness of 1.2–1.5 cm. The
sensory descriptive profile of the traditional product, when
evaluated by a sensory panel test, is the following: brown–
red uniform colour (Fig. 1b), sweet and slight acid, with a
not too hard–not too soft texture and presenting elasticity.
Concerning GH1, it was considered very similar to the
traditional product, with the same rate of global appreciation,
but with lower colour uniformity (Fig. 1c), sweetness
and elasticity. GH2 was similar to GH1, although obtaining
a lower global appreciation, possibly due to an even lower
acidity (Fig. 1d). HAT presented the sensory profile close
to the traditional product concerning colour uniformity,
sweetness and toughness but it was not appreciated due to
the colour tonality (yellow-orange) (Fig. 1e) and slight less
acidity. This product, although having the accurate organoleptic
characteristics except the colour, was rejected by
the panellists due to the inaccurate colour when compared
with the traditional product.
Before analysis, the pulp of the fresh and dried pears
was collected, ground and freeze-dried.
Sample origin and characteristicsAnalyses were performed on two lots of pears (Pyruscommunis L. var. S. Bartolomeu), corresponding to twodrying seasons, 2008 and 2009. Each lot was composed byfresh pear fruits and traditionally dried fruits (directexposure to solar radiation) (Traditional). The samplesfrom 2009 were also processed using three differentmethodologies: in a large glass greenhouse with air convection(GH1), in a small greenhouse with natural convection(GH2) and using a hot air tunnel in the absence oflight (HAT). All fruits were harvested in an orchard located638 Eur Food Res Technol (2011) 233:637–646123at the village of Ervedal da Beira (Oliveira do Hospital,Portugal) at the commercial maturity stage (Fig. 1a). Onaverage, the fresh fruits had a mass of 64 g, with a diameterof 4.3 cm and height of 6.5 cm. The moisture content was78%.For fresh pear analysis, some fruits were frozen justafter harvesting. The remaining fruits were processedaccording to the different methodologies under study.According to the traditional sun-drying process, thefresh fruits were peeled and allowed to dry in an openspace with sunshine incidence, as described by Ferreiraet al. [5] (Fig. 1b). After being peeled, fresh pears werealso allowed to dry in two greenhouses that differed in theirsize, structure and location. GH1 was provided with airconvection, with a flux of 900 m3 h-1, it was located atground level and, in comparison to GH2, had the largestcargo capacity. Its area was 6.3 m2 (3.19 m long by 1.93 mwide), and the height in the sides was 1.24 m, whereas inthe middle was 1.97 m. The structure was aluminium withhorticulture glass and there were two roof windows for airextraction. The drying time for GH1 was approximately7 days (Fig. 1c). The GH2 greenhouse consisted of insulatedglass panels and had the form of a box (1.20 m heightby 1.20 m long and 1.00 m wide). Inside, it was composedby a U-shaped structure, parallel to the floor, where pearswere let to dry. GH2 was located on a roof of a buildingand contained a step structure coated with reflective film,where pears were allowed to dry. This interior structureallowed a greater incidence of the light and consequentlypromoted the drying process by natural air convection, withthe air entering in the lower level (first step) and leaving inthe higher level, by means of a girandole. The drying timefor GH2 was approximately 5 days (Fig. 1d), 2 days lessthat the drying time of GH1.For hot air tunnel drying (HAT), after peeled, pears werelet to dry at a constant temperature of 40 C and an air flowof 1.2 m s-1 for about 7 days (Fig. 1e). The drying tunnelwas 2 m long, and the air convection was promoted by aventilator placed at the entrance of the tunnel. In thisstructure, pears were not exposed to light, although the airwas heated by a solar collector, and therefore the sun wasalso the main source of energy.Independently of the type of processing used, the processedfruits reached a mass of 10–14 g with a moisturecontent of 20% and had a maximum width of 2.5–3.4 cm,height of 3.9–4.7 cm and thickness of 1.2–1.5 cm. Thesensory descriptive profile of the traditional product, whenevaluated by a sensory panel test, is the following: brown–red uniform colour (Fig. 1b), sweet and slight acid, with anot too hard–not too soft texture and presenting elasticity.Concerning GH1, it was considered very similar to thetraditional product, with the same rate of global appreciation,but with lower colour uniformity (Fig. 1c), sweetnessand elasticity. GH2 was similar to GH1, although obtaininga lower global appreciation, possibly due to an even loweracidity (Fig. 1d). HAT presented the sensory profile closeto the traditional product concerning colour uniformity,sweetness and toughness but it was not appreciated due tothe colour tonality (yellow-orange) (Fig. 1e) and slight lessacidity. This product, although having the accurate organolepticcharacteristics except the colour, was rejected bythe panellists due to the inaccurate colour when comparedwith the traditional product.Before analysis, the pulp of the fresh and dried pearswas collected, ground and freeze-dried.
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