Abstracts
Pitaya peel can be used as a raw material for betalains extraction. The aim of this research was to quantify phenolic compounds, antioxidant activity and betalains on pitaya peel. Furthermore, evaluate the betalains stability against various pH conditions and exposure time of heating. The results showed that pitaya peel contains phenolic compounds and presented antioxidant activity. Moreover it showed high concentration of betalains (101.04mg equivalent to betanin. 100g-1) which were stable over a wide pH range (3.2 - 7.0) and were resistant to heating (100oC) up to 10 minutes at pH range from 3.7 to 5.5. Therefore, pitaya peel is a promising source of betalains which can be applied as a natural colorant for food.
betalains; antioxidant activity; colorant; phenolic compounds
A casca da pitaya pode ser utilizada como matéria prima para a extração de betalaínas. O objetivo deste trabalho foi quantificar os compostos fenólicos, atividade antioxidante e as betalaínas presentes na casca da pitaya. Além disso, foi avaliada a estabilidade das betalaínas em diferentes condições de pH e tempo de exposição ao aquecimento. Os resultados mostraram que a casca da pitaya contém compostos fenólicos e apresenta atividade antioxidante. Além disso, a casca da pitaya apresenta alta concentração de betalaínas (101,04mg equivalente a betanina. 100g-1) as quais apresentaram-se estáveis em uma ampla faixa de pH (3,2 - 7,0) e resistentes ao aquecimento (100oC) por até 10 minutos em uma faixa de pH de 3,7 a 5,5. Portanto, a casca da pitaya é uma fonte promissora de betalaínas as quais podem ser aplicadas como corante natural para alimentos.
betalaínas; atividade antioxidante; corante; compostos fenólicos
INTRODUCTION
Pitaya, belongs to Cactacea family, and is a native fruit from Mexico and Central and
South America (MIZRAHI et al., 1997MIZRAHI, Y. et al. Cacti as crops. Horticultural Review, v.18,
p.291-320, 1997. Avaliable from:
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). There are
many species of the fruit, however the Hylocereus undatus is the best known
and cultivated. Pitaya peel is considered a residue from the consumption and processing
of the fruit (JAMILAH et al., 2011JAMILAH, B. et al. Physico-chemical characteristics of red pitaya
(Hylocereuspolyrhizus) peel. International Food Research Journal, v.18, p.279-286,
2011. Avaliable from:
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http://www.ifrj.upm.edu.my/18%20(01)%202...
) and it is
usually discarded. However, this residue can be used as raw material for the extraction
of pigments, due to the presence of betalains which present attractive and stable color
(LI-CHEN et al., 2006LI-CHEN, W. et al. Antioxidant and antiproliferative activities of red
pitaya. Food Chemistry v.95, p.319-327, 2006. Avaliable from:
<http://www.researchgate.net/publication/248510478_Antioxidant_and_antiproliferative_act
vities_of_red_pitaya>. Accessed: Jan. 13, 2014. doi: 10.1016/j.
http://www.researchgate.net/publication/...
).
Betalains are a group of nitrogen pigments, which are water soluble and provide
attractive coloration for some groups of flowers and fruits. There are two subgroups,
the betacyanin red-violet and betaxantins yellow-orange (MOßHAMMER, et al., 2005MOBHAMMER, M.R. et al. Colour studies on fruit juice blends from
Opuntiaand Hylocereuscacti and betalain-containing model solutions derived therefrom.
Food Research International, v.38, p.975-981, 2005. Avaliable from:
<http://www.hugedrive.com/published/WG/show.php?q=U0VBQlVDS1RIT1JO
9cbc5d61&file=NDE=>. Accessed: Jul. 4, 2013.
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; HERBACH et al.,
2006aHERBACH, K.M. et al. Thermal degradation of betacyanins in juices from
purple pitaya (Hylocereuspolyrhizus [Weber] Britton and Rose) monitored by high
performance liquid chromatography-tandem mass spectrometric analyses. European Food
Research and Technology, v.219, p.377-385, 2004. Avaliable from:
<http://www.researchgate.net/publication/226418364>. Accessed: Jul. 21, 2013.
doi: 10.1007/s00217-004-0948-8.
http://www.researchgate.net/publication/...
). The betalains received less scientific attention than other classes of
natural pigments (chlorophylls, carotenoids and anthocyanins) due to their restricted
occurrence (STINTZING et al., 2005STINTZING, F.C. et al. Color, betalainpattern,
andantioxidantpropertiesofcactus pear (Opuntiassp.) clones. Journal of Agricultural
and Food Chemistry v.53, p.442-451, 2005. Avaliable from:
<http://pubs.acs.org/doi/abs/10.1021/jf048751y>. Accessed: Dec. 10, 2013. doi:
10.1021/jf048751y.
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).
Currently beet (Beta vulgaris) is the main source of commercial extraction
of betalains. However, beets contain substances as geosmin and pyrazines which are
responsible for the off flavor (ground) in this culture (STINTZING & CARLE, 2004STINTZING, F.C.; CARLE, R. Functional properties of anthocyanins and
betalains in plants, food, and in human nutrition. Trendsin Food Science and
Technology. v.15, p.19-38, 2004. Avaliable from:
<http://www.deepdyve.com/lp/elsevier/functional-properties-of-anthocyanins-and-betalains-in-plants-food-and-S4QE6MnvEL>.
Accessed: Nov. 7, 2013.
http://www.deepdyve.com/lp/elsevier/func...
). The betalains extracted from pitaya, unlike
the red beet, can be used in foods without flavor, and it covers a wide spectrum of
color from yellow-orange (Opuntia) to red-violet (Hylocereus)
(MOBHAMMER et al., 2005MOBHAMMER, M.R. et al. Colour studies on fruit juice blends from
Opuntiaand Hylocereuscacti and betalain-containing model solutions derived therefrom.
Food Research International, v.38, p.975-981, 2005. Avaliable from:
<http://www.hugedrive.com/published/WG/show.php?q=U0VBQlVDS1RIT1JO
9cbc5d61&file=NDE=>. Accessed: Jul. 4, 2013.
http://www.hugedrive.com/published/WG/sh...
).
The aim of this research was to quantify phenolic compounds, antioxidant activity and betalains on pitaya (Hylocereus undatus) peel. Furthermore, evaluate the betalains stability against various pH conditions and exposure time of heating.
MATERIALS AND METHODS
Samples (thirty units) of pitaya (Hylocereus undatus) were harvested at Embrapa Brasília-DF, Brazil, in 2011 January. The fruits were stored in a cold chamber (6oC) at the laboratory of fruits and vegetables at the Federal University of Santa Catarina.
The reagents used were all of analytical grade. Reagents: Folin-Ciocalteu, 2,4,6-tris-(2-pyridyl) -1,3,5-triazine (TPTZ), 2,2-diphenyl-1-picrylhydrazyl (DPPH), Trolox(6-hydroxy-2,5,7,8-tetrametilchroman-2-carboxylic acid) were obtained from Sigma Aldrich (Santa Ana, USA). Acetone was obtained from Vetec (Rio de Janeiro, Brazil) and the water used was filtered through deionization system (deionizer Milli-Q, Millipore, Bedford, USA).
Samples preparation: the fruits were washed and the pitaya peel was manually separated. Part of the pitaya peel samples was used in natura to total phenolic compounds and antioxidant analysis. The other part was completely dehydrated in a common oven (DeLeo, DLS04) at 45°C for about 12 hours, until constant weight, grinded (Quimis, Q298A21), packaged in polyethylene bags and stored in a freezer (-18°C). The moisture of the samples was determined previously each analysis, to express results at dry basis weight.
Extracts preparation: the extracts were obtained from pitaya peel of the three fruits, retired from the lot of thirty fruits. Pitaya peels were grounded in a food processor (RI Philips 1342). The crushed sample (5g) was taken for extraction at room temperature, using 200mL of acetone (80%) in an ultrasound (Unique, USC-1400) for 15min. After that, it was filtered through Whatman no1 filter paper. The filtrate was then evaporated in a rotary evaporator and frozen at -18oC.
Determination of total phenolic content: the content of phenolic compounds was
determined from in natura pitaya peel samples according to
Folin-Ciocalteu (ROSSI & SINGLETON, 1965ROSSI, J.A.J.; SINGLETON, V.L. Colorimetry of total phenolics with
phosphomolybdic phosphotungstic acid reagents. American Journal of Enology and
Viticulture, v.16, p.144-158, 1965. Avaliable from:
<http://ajevonline.org/content/16/3/144.short> . Accessed: Set. 28,
2013.
http://ajevonline.org/content/16/3/144.s...
)
that determines total phenols (and other oxidized substances), producing a blue color by
reducing yellow heteropoly phosphomolybdate-tungstate anions (WU et al., 2006WU, L. et al. Antioxidant and antiproliferative activities of red
pitaya. Food Chemistry v.95, p.219-327, 2006. Avaliable from:
<http://www.sciencedirect.com/science/article/pii/S0308814605000889>. Accessed:
May 2, 2013. doi: 10.1016/j.foodchem.2005.01.002.
https://doi.org/10.1016/j.foodchem.2005....
).
Determination of antioxidant activity: the determination of antioxidant activity was
performed from in natura pitaya peel samples, using the following
methods: FRAP method - the evaluation of reducer potential of iron
(FRAP) was determined according to the methodology described by BENZIE & STRAIN (1996)BENZIE, I.F.F.; STRAIN, J.J. The ferric reducing ability of plasma
(FRAP) as a measure of antioxidant power: the FRAP assay. Analytical Biochemistry,
v.239, p.70-76, 1996. Avaliable from:
<http://www.ncbi.nlm.nih.gov/pubmed/8660627>. Accessed: Jun. 7, 2012. doi:
10.1006/abio.1996.0292.
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and DPPH method - the
reduction of the stable radical DPPH was determined according to the methodology
described by BRAND-WILLAMS et al. (1995)BRAND-WILLIAMS, W. et al. Use of free radical method to evaluate
antioxidant activity. Lebensmittel - Wissenschaft und -Technologie. v.22, p.25-30,
1995. Avaliable from: <http://www.researchgate.net/publication/223633796>.
Accessed: Sep. 14, 2012. doi: 10.1016/S0023-6438(95)80008-5.
http://www.researchgate.net/publication/...
, with
modifications by KIM et al. (2002)KIM, D.O. et al. Vitamina C equivalente antioxidantcapacity (VCEAC) of
phenolics phytochemicals. Journal of Agricultural and Food Chemistry v.50,
p.3713-3717, 2002. Avaliable from:
<http://www.ncbi.nlm.nih.gov/pubmed/12059148>. Accessed: Jul. 12, 2013. doi:
10.1021/jf020071c.
http://www.ncbi.nlm.nih.gov/pubmed/12059...
.
Quantification of betalains: a sample of dried pitaya peel (1g) was diluted with
distilled water, and transferred to a flask, where the volume was completed to 100mL,
filtered with a vacuum pump with filter paper Whatmann o1. The filtrate was
then used to spectrophotometer (HITACHI U-1800) analysis and the readings at 536 nm were
performed in triplicate. Quantification of betalains was calculated according to
Beer-Lambert-Bougue Law, modified by TANG &
NORZIAH (2007)TANG, C.S.; NORZIAH, M.H. Stability of betacyanin pigments from red
purple pitaya fruit (Hylocereuspolyrhizus): influence of pH, temperature, metal ions
and ascorbic acid. Indonesian Journal of Chemistry. v.7, p.327-331, 2007. Avaliable
from: <http://pdm-mipa.ugm.ac.id/ojs/index.php/ijc/article/viewArticle/446>.
Accessed: Mar. 12, 2013.
http://pdm-mipa.ugm.ac.id/ojs/index.php/...
.
Stability of betalains: the stability of betalains present in the pitaya peel was evaluated by exposing the extracts of betalains at various pH conditions (2.4, 3.2, 3.7, 4.2, 4.5; 5, 5.5, 6, 6.5, 7, 7.5, 8) and exposure times (0, 5, 10, 20, 30, 40, 50, 60, 70, 80 to 90min) at temperature of 100oC. The extracts were prepared from dehydrated samples (1g), diluted in buffer solution of Na2HPO4 (0.2M) and citric acid (0.1M). The extract was exposed to a temperature of 100 °C, and three samples were taken at time intervals for the analysis at the spectrophotometer (Hitachi, U-1800) scanning absorbance at 280-780nm at a speed of 400nm.min-1, and colorimeter (Minolta CR-400 Chroma) with illuminant D65 and the CIE L * a * b *, in triplicate.
RESULTS AND DISCUSSION
Total phenolic content and antioxidant activity
Fresh pitaya peel (moisture of 90.23g. 100g-1) presents high level of
phenolic content (40.68mg GAE.100g-1). Content of total phenolic compounds
is high, being similar to that found in white grape, blueberry, apple, pear and plum
(VAILLANT et al., 2005VAILLANT, F. et al. Colourant and antioxidant properties of red-purple
pitahaya (Hylocereus sp.) Fruits. v.60, p.1-10, 2005. Avaliable from:
<http://journals.cambridge.org/download.php?file=%2FFRU%2FFRU60_01%2FS0248129405000071a.pdf&code=3d8a07f5d470f771533e435a6523a1b7>.
Accessed: Feb. 25, 2013. doi: 10.1051/fruits:2005007.
http://journals.cambridge.org/download.p...
). Wu et al. (2006WU, L. et al. Antioxidant and antiproliferative activities of red
pitaya. Food Chemistry v.95, p.219-327, 2006. Avaliable from:
<http://www.sciencedirect.com/science/article/pii/S0308814605000889>. Accessed:
May 2, 2013. doi: 10.1016/j.foodchem.2005.01.002.
https://doi.org/10.1016/j.foodchem.2005....
) found phenolic total content of
39.7 ± 5.39mg of GAE.100g-1 in pitaya peel. Although, Choo & Yong (2001CHOO, W.S.; YONG, W.K. Antioxidant properties of two species of
Hylocereus fruits. Advances in Applied Science Research, v.2, p.418-425, 2001.
Avaliable from:
<http://pelagiaresearchlibrary.com/advances-in-applied-science/vol2-iss3/AASR-2011-2-3-418-425.pdf>.
Accessed: Set. 12, 2013.
http://pelagiaresearchlibrary.com/advanc...
) found higher total
phenolic content in the pulp (28.65mg GAE. 100g-1) than in the pulp + peel
(20.14mg GAE.100g-1).
The levels of phenolic compounds detected in pitaya are considerably high compared
with other fruits such as banana - 11mg GAE. 100g-1, pineapple - 15mg GAE.
100g-1, papaya - 26mg GAE. 100g-1 and low compared with
cherry 670mg GAE. 100g-1 and blueberries 318mg GAE. 100g-1
(LAKO et al., 2007LAKO, J. et al. Phytochemical flavanols, carotenoids and the antioxidant
properties of a wide selection of Fijian fruit, vegetable and other readily available
foods. Food Chemistry, v.101, p.1727-1741, 2007. Avaliable from:
<http://repository.usp.ac.fj/749/>. Accessed: Oct. 15, 2012.
http://repository.usp.ac.fj/749/...
).
Pitaya peel presented higher antioxidant activity when analyzed by DPPH (177.14μmol AEAC. 100g-1) than when analyzed by FRAP (109.29μmol AEAC. 100g-1) method. On the other hand, the fresh pulp of pitaya presents 306.81μmol AEAC. 100g-1 (MUÑOZ et al., 2002MUÑOZ, D.C. et al. Los alimentos y sus nutrientes. Tablas de valor nutritivo de alimentos. México: McGraw Hill Interamericana, 2002. 203p.).
ESQUIVEL et al. (2007)ESQUIVEL, P. et al. Phenolic compound profiles and their corresponding
antioxidante capacity of purple pitaya (Hylocereus sp.) genotypes. Zeitschrift für
Naturforschung, v.62, p.636-644, 2007. Avaliable from:
<http://www.znaturforsch.com/ac/v62c/s62c0636.pdf>. Accessed: jan. 10, 2014.
http://www.znaturforsch.com/ac/v62c/s62c...
investigated the
contributions of phenolics to the antioxidant capacity of purple-red pitaya and
concluded that betalains were responsible for the major antioxidant capacity of
purple pitaya juices while non-betalainic phenolic compounds contributed the least.
They observed a positive correlation between total antioxidant activity (Trolox
equivalent antioxidant capacity) and total betalain contents
(R2=0.75). The high betalain content of pitaya seems to contribute
significantly to this high antioxidant capacity (VAILLANT et al., 2005VAILLANT, F. et al. Colourant and antioxidant properties of red-purple
pitahaya (Hylocereus sp.) Fruits. v.60, p.1-10, 2005. Avaliable from:
<http://journals.cambridge.org/download.php?file=%2FFRU%2FFRU60_01%2FS0248129405000071a.pdf&code=3d8a07f5d470f771533e435a6523a1b7>.
Accessed: Feb. 25, 2013. doi: 10.1051/fruits:2005007.
http://journals.cambridge.org/download.p...
).
PANTELIDIS et al. (2007)PANTELIDIS, G.E. et al. Antioxidant capacity, phenol, anthocyanin and
ascorbic acid contents in raspberries, blackberries, red currants, gooseberries and
cornelian cherries. Food Chemistry v.102, p.777-783, 2007. Avaliable from:
<http://www.deepdyve.com/lp/elsevier/antioxidant-capacity-phenol-anthocyanin-and-ascorbic-acid-contents-in-Ow6IubFska>.
Accessed: Nov. 13, 2013. doi: 10.1016/j.foodchem.2006.06.021.
http://www.deepdyve.com/lp/elsevier/anti...
reported the
antioxidant activity of some cultivars of gooseberry 40.7-65.1μmol
AEAC.g-1; blackberry 113.6-169.0μmol AEAC.g-1 and raspberry
77.7-145.4μmol AEAC.g-1.
Quantification of betalains
Pitaya peel presented 101.04mg betanin equivalent. 100g-1 of dry sample.
These level was much higher that founded by TANG
& NORZIAH (2007)TANG, C.S.; NORZIAH, M.H. Stability of betacyanin pigments from red
purple pitaya fruit (Hylocereuspolyrhizus): influence of pH, temperature, metal ions
and ascorbic acid. Indonesian Journal of Chemistry. v.7, p.327-331, 2007. Avaliable
from: <http://pdm-mipa.ugm.ac.id/ojs/index.php/ijc/article/viewArticle/446>.
Accessed: Mar. 12, 2013.
http://pdm-mipa.ugm.ac.id/ojs/index.php/...
, corresponding to 6.7mg betanin equivalent.
100g-1 of fresh pitaya peel, however for Hylocereus polyrhizus
species. Figure 1 shows a single peak at
about 538nm. In contrast, beetroot extracts show a second absorption peak at about
480nm, which is characteristic of yellow betaxanthins (VAILLANT et al., 2005VAILLANT, F. et al. Colourant and antioxidant properties of red-purple
pitahaya (Hylocereus sp.) Fruits. v.60, p.1-10, 2005. Avaliable from:
<http://journals.cambridge.org/download.php?file=%2FFRU%2FFRU60_01%2FS0248129405000071a.pdf&code=3d8a07f5d470f771533e435a6523a1b7>.
Accessed: Feb. 25, 2013. doi: 10.1051/fruits:2005007.
http://journals.cambridge.org/download.p...
).
Absorption spectra of betalains in different pHs and exposure times to temperature of 100oC.
Therefore, according to ZHIJIAN & XIN
(2003)ZHIJIAN, D.; XIN, Y. Studies on the stability of red pigment in
Hylocereusundatus fruit. Jounal of South China Agricultural University, v.24,
p.79-83, 2003. Avaliable from:
<http://agris.fao.org/agris-search/search.do?f=2004/CN/CN04032.xml;CN2004080789>.
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, pitaya peel can be used as raw material for pigment extraction due
to the presence of high betalains concentration.
Stability of betalains
The betalains of pitaya peel were stable in the pH range from 3.2 to 7. The highest
degradation was observed at pH 2.4 followed by pH 8, corresponding to extreme acidic
and basic analyzed conditions (Figure 1). The
stable range of pH founded is according to STINTZING
et al. (2003)STINTZING, F.C. et al. Evaluation of colour properties and chemical
quality parameters of cactus juices. European Food Research and Technology v.216,
p.303-311, 2003. Avaliable from:
<http://www.researchgate.net/publication/226207032>. Accessed: Apr. 16, 2013.
doi: 10.1007/s00217-002-0657-0.
http://www.researchgate.net/publication/...
and TANG & NORZIAH
(2007)TANG, C.S.; NORZIAH, M.H. Stability of betacyanin pigments from red
purple pitaya fruit (Hylocereuspolyrhizus): influence of pH, temperature, metal ions
and ascorbic acid. Indonesian Journal of Chemistry. v.7, p.327-331, 2007. Avaliable
from: <http://pdm-mipa.ugm.ac.id/ojs/index.php/ijc/article/viewArticle/446>.
Accessed: Mar. 12, 2013.
http://pdm-mipa.ugm.ac.id/ojs/index.php/...
, who reported that the color of the pitaya betalains was remarkably
stable in the pH range 3-7.
The maximum absorption was detected at pH 7.0 followed by pH 4.5. However, CASTELLAR et al. (2003)CASTELLAR, M.R. et al. Color properties and stability of betacyanins
from Opuntia fruits. Journal of Agricultural and Food Chemistry. v.51, p.2772-2776,
2003. Avaliable from: <http://pubs.acs.org/doi/abs/10.1021/jf021045h>.
Accessed: Oct. 15, 2012. doi: 10.1021/jf021045h.
http://pubs.acs.org/doi/abs/10.1021/jf02...
found the maximum
absorption of betalains at pH from 5.0 to 6.0. Moreover STINTZING et al. (2004)STINTZING, F.C. et al. Structural investigations on betacyanin pigments
by LC NMR and 2D NMR spectroscopy, Phytochemistry. v.65, p.415-422, 2004. Avaliable
from: <http://www.researchgate.net/publication/8888335>. Accessed: Sep. 22,
2013. doi: 10.1016/j.
http://www.researchgate.net/publication/...
reported that the
greatest stability of the color of the betalains from pitaya is at pH 5.0. The
characteristic of stability at acid pH, but greater than 3.0, allows that pitaya
betalains can be used as a pigment in low-acid foods (CASTELLAR et al., 2006CASTELLAR, M.R. et al. The isolation and properties of a concentrated
red-purple betacyanin food colourant from Opuntiastrictafruits. Journal of the
Science of Food and Agriculture. v.86, p.122-128, 2006. Avaliable from:
<http://onlinelibrary.wiley.com/doi/10.1002/jsfa.2285/abstract>. Accessed: Nov.
9, 2012. doi: 10.1002/jsfa.2285.
http://onlinelibrary.wiley.com/doi/10.10...
; VAILLANT et al., 2005VAILLANT, F. et al. Colourant and antioxidant properties of red-purple
pitahaya (Hylocereus sp.) Fruits. v.60, p.1-10, 2005. Avaliable from:
<http://journals.cambridge.org/download.php?file=%2FFRU%2FFRU60_01%2FS0248129405000071a.pdf&code=3d8a07f5d470f771533e435a6523a1b7>.
Accessed: Feb. 25, 2013. doi: 10.1051/fruits:2005007.
http://journals.cambridge.org/download.p...
).
The betalains have been degraded over time of exposure to a temperature of 100°C. How greater the exposure, greater is the degradation of the pigment, following a first order reaction kinetics, as reported by HERBACH et al. (2004). The absorption peak at 536nm was reduced during the heating time and that after 30 minutes cannot be observed anymore (Figure 1). After 5 minutes of heating, it is possible to observe that there was a shift of absorption maximum pH from 7.0 to 5.0, with a reduction of 39.5% retention of the pigment.
The heating causes degradation of betalains by isomerization, decarboxylation or
cleavage resulting in a gradual reduction of red and the appearance of a light brown
color (HERBACH et al., 2006bHERBACH, K.M. et al. Stability and color changes of thermally treated
betanin, phyllocactin, and hylocerenin solutions. Journal of Agricultural and Food
Chemistry v.54, p.390-398, 2006b. Avaliable from:
<http://pubs.acs.org/doi/abs/10.1021/jf051854b>. Accessed: Nov 8, 2012. doi:
10.1021/jf051854b.
http://pubs.acs.org/doi/abs/10.1021/jf05...
). Cleavage of
betanin and isobetanina, which can also be induced by bases (SCHLIEMANN et al., 1999SCHLIEMANN, W. et al. The decisive step in betaxanthin biosynthesis is a
spontaneous reaction. Plant Physiology. v.119, p.1217-1232, 1999. Avaliable from:
<http://www.plantphysiol.org/content/119/4/1217.abstract>. Accessed: Dec. 9,
2013. doi: 10.1104/pp.119.4.1217.
http://www.plantphysiol.org/content/119/...
), generates the bright yellow acid
betalamic and cyclo-Dopa-5-0-glycoside colorless. HERBACH et al. (2006a)HERBACH, K M. et al. Betalain stability and degradation - structural and
chromatic aspects. Journal of FoodScience. v.71, p.41-50, 2006a. Avaliable from:
<http://onlinelibrary.wiley.com/doi/10.1111/j.1750-3841.2006.00022.x/abstract>.
Accessed: May 17, 2013. doi: 10.1111/j.1750-3841.2006.00022.x
http://onlinelibrary.wiley.com/doi/10.11...
reported that the degradation of
betalains is usually accompanied by a marked change in color resulting from the
formation of degradation yellow products such as betalamic acid (424nm) and
betaxantins (460-480nm).
With heat increasing the sample time showed increased of the parameter L* (lightness of the color), decrease of the parameter a* (from red to green) and increase of the parameter b* (from blue to yellow) values, to all pHs analyzed (Figure 2). This behavior means that with the increasing of heating time the pink color, characteristic of betalains, was degraded to different shades of yellow, characteristic of betaxantins and betalamic acid.
: Colorimetric analysis (parameters (L *, a *, b*) of pitaya peel exposed a different conditions of pH and exposure time to temperature of 100oC.
Extreme acidic pH (2.4) and basic (8.0) conditions and the heating time of five minutes was sufficient to degrade the color of betalains. At pH 5.0, it was observed higher stability of the parameter a* to 10 minutes of heating.
At 10 minutes of heating the color of betalains was stable in the range of pH 3.7 to 5.5. After this time period, the color of betalains was degraded to orange and to yellow.
Therefore, the betalains of pitaya showed good stability in a wide pH range (3.0-7.0)
and resistance to heating for 10 minutes at 100oC at pH range of 3.7 to
5.5. These results are very similar to those obtained for VAILLANT et al. (2005)VAILLANT, F. et al. Colourant and antioxidant properties of red-purple
pitahaya (Hylocereus sp.) Fruits. v.60, p.1-10, 2005. Avaliable from:
<http://journals.cambridge.org/download.php?file=%2FFRU%2FFRU60_01%2FS0248129405000071a.pdf&code=3d8a07f5d470f771533e435a6523a1b7>.
Accessed: Feb. 25, 2013. doi: 10.1051/fruits:2005007.
http://journals.cambridge.org/download.p...
.
CONCLUSION
Pitaya peel can be considered as a potential source of betalains, which besides having effect as natural colorant, is rich in phenolic compounds and further presented high antioxidant activity. The betalains from pitaya peel remained stable over a wide pH range (3.2-7.0) and were resistant to heating (100oC).up to 10 minutes at pH range from 3.7 to 5.5. This feature allows the application of pitaya peel in low acidity foods with moderate heat treatment, or else to be added in food after heating.
The production of natural colorant from pitaya peel can be a great alternative for the food industry, as well as reduce the environmental impact caused by the current discarding of the peel. Furthermore pitaya peel can be a healthy substitute for synthetic colorant.
ACKNOWLEDGEMENTS
The authors are grateful to Embrapa Cerrado for provide the pitaya samples and technical information and to Dr Nilton Tadeu Vilela Junqueira for providing scientific information on the pitaya fruit.
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Publication Dates
-
Publication in this collection
21 Oct 2014 -
Date of issue
Feb 2015
History
-
Received
16 Apr 2014 -
Accepted
18 June 2014