Revista Brasileira de Produtos Agroindustriais, Campina Grande, v.16, n.2, p.173-178, 2014
ISSN: 1517-8595
173
COLORIMETRIC CHARACTERIZATION OF READY-TO-EAT IRRADIATED
CARROTS
Vanessa de Cillos Silva1,2, Valter Arthur1, Marcia Nalesso Costa Harder1,2, Fernanda
Faganelo Neme2
ABSTRACT
Consumers are increasingly looking for healthy foods and practical, where time is a prime
factor. The technology known as "ready to eat", which can combine the techniques such as
minimally processed and pre-cooking. These techniques add value to the product and make life
easier for consumers. The food preservation techniques have been studied because of the
growing concern to health and safety of the food consumed. The present work aims to evaluate
the effect of different doses of gamma radiation on ready-to-eat carrots with respect to the color
parameter. The parameter color was analyzed by L, a *, b * values, chroma and Hue-Angle. We
used Minolta CR-200 colorimeter previously calibrated in white. It is concluded, by the results
obtained, that irradiation decreased the red-orange color of carrots irradiated on the first day, but
preserved the dye compounds during the storage period.
Keywords: carrots, ready-to-eat, gamma radiation, color analysis
CARACTERIAÇÃO COLORIMÉTRICA DE CENOURAS IRRADIADAS “PRONTAS
PARA COMER”
RESUMO
Os consumidores estão cada vez mais procurando alimentos saudáveis e práticos, onde o tempo
é um fator primordial. A tecnologia conhecida como "pronto para comer", que pode combinar as
técnicas, tais como minimamente processados e pré-cozimento. Estas técnicas agregam valor ao
produto e torna a vida mais fácil para os consumidores. As técnicas de conservação de
alimentos têm sido estudadas por causa da crescente preocupação com a saúde e segurança dos
alimentos consumidos. O presente trabalho tem como objetivo avaliar o efeito de diferentes
doses de radiação gama sobre cenouras “prontas para comer” com referência ao parâmetro cor.
O parâmetro de cor foi analisado pelos parâmetros L, a *, b *, croma e ângulo Hue. Foi
utilizado para esta avaliação o colorímetro Minolta CR-200, previamente calibrado em branco
de acordo com metodologia previamente estabelecida. Concluiu-se, através dos resultados
obtidos, que a irradiação reduziu a cor vermelho-alaranjado das cenouras irradiadas no primeiro
dia, mas preservou os compostos corantes durante o período de armazenamento.
Palavras-chave: cenouras, alimentos pronto para comer, radiação gama, análise de cor
1
Radiobiology and Environment Department, Center of Nuclear Energy in Agriculture – CENA/USP, Av.
Centenário, 303 13416-000 Piracicaba, SP, Brazil
2
Technology College of Piracicaba – FATEC Piracicaba, Rua Diácono Jair de Oliveira, 651 13414-155
Piracicaba, SP, Brazil
174
Colorimetric characterization of ready-to-eat irradiated carrots
Silva et al.
INTRODUTION
The consumer’s lifestyle and eating
habits have suffered significant changes in
recent years, increasing demand for ready-toeat foods.
Ready-to-eat foods products refer to
any fruit, vegetable or combination of them that
was altered from its original form, ie, gone
through processes such as selection, washing,
disinfection, peeling, cutting, spinning and
packaging, making it usable in its entirety
(Moretti, 1999; IFPA, 2005 cited in Rodrigues,
2005).
To avoid problems related to
contamination of ready-to-eat foods by
microorganisms is necessary strict control of all
processes (Rodrigues, 2005). Using the
technique of irradiation has been extensively
studied and has shown satisfactory results in
relation to food preservation in most
experiments analyzed.
The carrot (Daucus carota L.) stands
out as one of the world's major vegetable crops
because of its large consumption around the
world and the extension of cultivated area
(Lima et al., 2003). It is one of most vegetables
grown in Brazil, with higher production in the
periods between July and November
(Murayama, 1973).
Shurong, et al. (2006) found the effects
of gamma radiation doses below 2 kGy in
carrots and cherry tomatoes pre-cutted and
storage under refrigeration. The analyzed
aspects (color, nutritional quality, soluble
solids, sensory quality and permeability of cell
membrane) did not change significantly,
enabling the process of irradiation on the food
security of these foods.
Bibi et al. (2006) hightlights that doses
up to 2 kGy were sufficient for the maintenance
of ready-to-eat carrots with sensory and
microbiological characteristics acceptable for
two weeks exposed to cooling.
Another study found that doses of 4
kGy in ready-to-eat carrots can be used to
increase the lifetime of the product without
changing its sensory qualities (Hammad et al.,
2006).
The aim of this work is to assess the
action of different doses of gamma radiation on
minimally processed carrots, pre-cooked,
vacuum packed and stored at a temperature of 8
° C with respect to the color parameter.
174
MATERIAL AND METHODS
Sample preparation
Carrots (Daucus carota L.) were
washed to remove dirt from thick, peeled with
sharp knives, immersed in water, cut into sticks,
immersed in water with 2,00 – 2,50% P/P for
10 minutes and dried in stainless steel colander.
After drying were pre-cooked for 6 minutes and
placed in polypropylene containers sealed under
vacuum, adapted from Pilon (2003).
Treatments
The packages containing pre-cooked and readyto-eat carrots were submitted to gamma
radiation from a Co60 source type Multipurpose
in the Institute of Energy and Nuclear (IPEN),
at doses of 0 (control), 1.0 kGy, 2.0 kGy and
3.0 kGy. The samples were stored in BOD at
temperatures of 8°C ± 1°C.
Treatments evaluation
Color analysis
The parameters were analyzed for color
L, a *, b * values, Chroma and Hue-Angle. We
used a colorimeter Minolta CR-200 b
previously calibrated in white (Bible & Singha,
1997). The values were measured in a *, b *
and L * characterizes where the colors red (+a
*) to green (-a *) b *, yellow (+b *) to blue (-b
*) and white L (L = 100) to black (L = 0).
It was determined the values of Chroma
and Hue-Angle by the values obtained by a *, b
* and L, as the following formulas (Estevez &
Cava, 2004):
C=
a
2
 b2

Hº=arctg b*/a*
Statistical Analysis
Results were submitted to a variance
analysis, F test at 5%, and Tukey test, using
SAS (Statistical analysis system institute,
1996).
Colorimetric characterization of ready-to-eat irradiated carrots
175
Silva et al.
RESULTS AND DISCUSSION
The average values of L in the different
treatments of carrots processed and pre-cooked
by irradiation are showed in Table 1.
Color parameters
L values
Table 1 - Mean values of L for carrots processed, precooked and irradiated during the storage period
1 day
8 days
15 days
22 days
29 days
0 KGY
57.62 ± 1.69*a**
41.58 ± 5.29a
46.09 ± 5.19a
42.87 ± 7.10a
50.51 ± 5.20a
1 KGy
52.02 ± 1.44ab
46.81 ± 4.31a
46.49 ± 3.21a
39.84 ± 7.35a
49.02 ± 7.25a
2 KGy
51.01 ± 1.38b
47.39 ± 2.29a
49.58 ± 8.27a
48.56 ± 2.58a
56.32 ± 1.22a
3 KGy
47.48 ± 3.52b
48.57 ± 1.58a
50.72 ± 2.05a
43.95 ± 5.37a
51.95 ± 5.39a
* Mean ± standard deviation.
**
Means followed by the same letter in column do not differ by Tukey test (P <0.05).
Figure 1 - Mean values of L along time for different treatments
According to the data showed in Table
1, we can observe that there was statistical
difference only at the first day decreasing the
brightness was increased as the dose.
For other days, it is observed that there
was no statistical difference between
treatments, but there was a loss of brightness
over the days, increase the value assessed on
the last day (Figure 1).
These results are agree in value with
Lima et al. (2004) found that average around
49.01 for the parameter L, also agrees that there
was a loss of brightness along time and,
furthermore, agree that last week the L values
increased for irradiated.
The values found were agree well with
those obtained by Lima et al. (2001) who
obtained average values for L of 43.9 for
carrots irradiated.
a and b values
The mean values of results obtained by
instrumental analysis of color, the parameters a
(red) and b (yellow) in minimally processed
carrots, cooked and pre-irradiated are presented
in Tables 2 and 3 respectively.
Table 2 - Mean values for a processed carrots, cooked and pre-irradiated during the storage period
1 day
8 days
15 days
22 days
29 days
0 KGY
29.28 ± 1.89*a**
21.21 ± 0.59b
23.21 ± 0.98a
20.30 ± 0.27a
22.58 ± 2.49b
1 KGy
23.47 ± 0.98b
22.37 ± 1.01ab
22.07 ± 1.24a
20.19 ± 1.49a
22.88 ± 3.09b
2 KGy
23.25 ± 1.50b
22.24 ± 2.19b
22.55 ± 3.60a
23.95 ± 1.22a
30.38 ± 2.53a
3 KGy
22.76 ± 1.09b
26.75 ± 2.37a
23.87 ± 0.65a
22.26 ± 2.93a
25.25 ± 1.45ab
* Mean ± standard deviation.
**
Means followed by the same letter in column do not differ by Tukey test (P <0.05).
Revista Brasileira de Produtos Agroindustriais, Campina Grande, v.16, n.2, p.173-178, 2014
176
Colorimetric characterization of ready-to-eat irradiated carrots
Silva et al.
Figure 2 - Mean values of along time for different treatments
Table 3 - Mean values for b processed carrots, cooked and pre-irradiated during the storage period
1 day
8 days
15 days
22 days
29 days
0 KGY
59.04 ± 3.74*a**
44.17 ± 2.26b
46.80 ± 2.77a
43.05 ± 3.09a
46.60 ± 7.19a
1 KGy
50.23 ± 1.60b
46.58 ± 0.42b
47.97 ± 4.70a
40.20 ± 5.40a
46.93 ± 10.28a
2 KGy
49.30 ± 2.70b
47.54 ± 3.56ab
44.80 ± 5.00a
47.68 ± 1.05a
61.65 ± 4.56a
3 KGy
48.59 ± 4.32b
53.23 ± 2.52a
48.76 ± 2.04a
45.43 ± 5.49a
53.12 ± 3.97a
* Mean ± standard deviation.
**
Means followed by the same letter in column do not differ by Tukey test (P <0.05)
Figure 3 - Mean values of b along time for different treatments
It may be noted that the first day, both
the parameter a and b decrease with radiation,
but during the day this process is reversed, ie,
the irradiated samples tended to keep the color,
while the witness fell within the parameters
analyzed (Figure 2 and 3).
The values obtained for the parameter a
are agree with Lee et al. (2001) and Lima et al.
(2004), who obtained for this award averages
around 24.04 and 23.7 respectively.
For the values obtained for the parameter
b, the means values showed by the authors
differ from the values obtained, which showed
the average around 25.0.
These variations can be attributed to
variability of the samples, this fact were
observed by Lima et al. (2001).
Croma and Hue-Angle values
The means values of the results obtained
by color instrumental analysis, the Chroma
parameters (color) and Hue-Angle (saturation)
in ready-to-eat carrots, cooked and preirradiated are presented in Tables 4 and 5
respectively.
Revista Brasileira de Produtos Agroindustriais, Campina Grande, v.16, n.2, p.173-178, 2014
Colorimetric characterization of ready-to-eat irradiated carrots
177
Silva et al.
Table 4 - Mean values for Chroma processed carrots, cooked and pre-irradiated during the storage
period
1 day
8 days
15 days
22 days
29 days
0 KGY
65.90 ± 4.13*a**
48.99 ± 2.23b
52.25 ± 2.55a
47.61 ± 2.70a
51.79 ± 7.53a
1 KGy
55.45 ± 1.57b
51.68 ± 0.64b
52.81 ± 4.72a
45.00 ± 5.49a
52.23 ± 10.58a
2 KGy
54.51 ± 2.91b
52.52 ± 3.64b
50.16 ± 6.08a
53.37 ± 1.06a
68.74 ± 5.07a
3 KGy
53.66 ± 4.37b
59.58 ± 3.13a
54.29 ± 2.10a
50.59 ± 6.21a
58.82 ± 4.16a
* Mean ± standard deviation.
**
Means followed by the same letter in column do not differ by Tukey test (P <0.05)
Figure 4 - Mean values of Chroma along time for different treatments
Table 5 - Mean values for Hue-Angle processed carrots, cooked and pre-irradiated during the storage
period
1 day
8 days
15 days
22 days
29 days
0 KGY
1.11 ± 0.01*a**
1.12 ± 0.01a
1.11 ± 0.03a
1.13 ± 0.03a
1.12 ± 0.02a
1 KGy
1.13 ± 0.02a
1.12 ± 0.02a
1.14 ± 0.02a
1.10 ± 0.03a
1.11 ± 0.03a
2 KGy
1.13 ± 0.02a
1.13 ± 0.04a
1.11 ± 0.02a
1.11 ± 0.02a
1.11 ± 0.02a
3 KGy
1.13 ± 0.02a
1.11 ± 0.02a
1.12 ± 0.01a
1.12 ± 0.01a
1.12 ± 0.01a
* Mean ± standard deviation.
Means followed by the same letter in column do not differ by Tukey test (P <0.05).
**
Figure 5 - Mean values of Hue-Anlge along time for different treatments
It may be noted that the first day, the
parameter chroma decreases with radiation, but
during the day this process is reversed, ie, the
irradiated samples tended to keep the color,
while the witness fell on the parameter analyzed
(Figure 4).
Chervin & Boisse (1994) are agree the
results, at day 1, which shows loss of orangered color due to oxidation of carotenes after
processing. But it turns out that this work to
orange-red color remains, over time, treatments
and lost in the witness.
Revista Brasileira de Produtos Agroindustriais, Campina Grande, v.16, n.2, p.173-178, 2014
178
Colorimetric characterization of ready-to-eat irradiated carrots
These variations can also be attributed to
variability of the samples, a fact observed by
Lima et al. (2001).
There is stability with respect to the HueAnlge, since it showed no significant
differences between treatments, indicating that
the color saturation did not change due to
irradiation.
CONCLUSIONS
By the results obtained, we can be
concluded that irradiation decreased the redorange color of carrots irradiated on the first
day, subsequent reviews, the treated samples
showed higher values than the control, showing
that radiation protected the dye compounds.
In addition, the instrumental analysis
showed that irradiated carrots have become
clearer, the evaluation of the parameter L with
the storage time.
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Revista Brasileira de Produtos Agroindustriais, Campina Grande, v.16, n.2, p.173-178, 2014