Autor(es):
Guiné, Raquel 
; Sério, Susana ; Correia, Paula ; Barroca, Maria João
Data: 2014
Identificador Persistente: http://hdl.handle.net/10400.19/2314
Origem: Repositório Científico do Instituto Politécnico de Viseu
Assunto(s): carrots; pre-treatment; drying; color; texture
Descrição
Carrot is the most commonly used vegetable for hu-
man nutrition and is an excellent source of β-carotene,
vitamin A and potassium, and contains cholester-
ol-lowering pectin, vitamin C, vitamin B6, thiamine,
folic acid, and magnesium. Carrots are highly season-
al and abundantly available at particular times of the
year. For extending the availability of this root, several
preservation processes can be used, but convective
drying is one of the most important since it not only
extends vegetable shelf life significantly but also diver-
sifies the offer of foods for consumers. However, con-
vective drying can also give rise to significant chemical
changes (non-enzymatic browning, among others),
which may affect the quality of the product. Pre-drying
treatments of solid food products can be used as a way
to augment product quality and to modify the struc-
ture of food products so as to improve mass transfer
coefficient s i n drying . I n thi s context , assessment s of
the physical and chemical properties were made in or-
der to investigate the effects of sodium metabisulphite
at different concentration/time combinations prior
convective drying of carrots.
The carrots used in this study were purchased in a lo-
cal market, and hand peeled and cut into slices with
thickness of 10 mm. Before convective drying at 60 0 C
the slices of carrots were submitted to pre-treatments
as follows: a) dipping in a water solution of 0.25% of
sodium metabisulphite for 60 and 90 min. and 1% of
sodium metabisulphite for the same times, at room
temperature; b) dipping in an equal mass of plain water
for 60 and 90 min. at room temperature (as control sam-
ple). Some chemical properties of the fresh and dried
samples were evaluated with classical methods, name-
ly moisture content, fiber, ashes and sugars (reducing,
total and non-reducing sugars). The physical properties
evaluated were color and texture. Color was evaluated
with a Colorimeter in the CieLab color space and texture
was measured Color was evaluated with a Colorimeter
in the CieLab color space and texture was measured by
texture profile analysis with a texturometer.
The main results show that the different combina-
tions concentration/time of sodium metabishulphite
dipping has a similar effect on the chemical proper-
ties of the dried carrots. Furthermore, the dried slices
of carrots with and without pre-treatment originat-
ed products with similar nutritional characteristics.
With respect of color, the total difference of color and
browning index was similar to the different solutions
of sodium metabishulphite. In addition the browning
of the dried carrots was, apparently, independent of
the pre-treatment. Similarly, the different combina-
tions of pre-treatment had no visible effect on textural
parameters and generally the hardness decreased with
the pre-treatments.
From the obtained results it was concluded that the
different concentration/time combinations of sodium
metabisulphite solutions had no visible improvement
on the quality of the dried carrots.
