Original article
Effect of drying kinetics on main bioactive compounds and
antioxidant activity of acerola (Malpighia emarginata D.C.) residue
Alexandra G. Duzzioni,* Vanessa M. Lenton, Diogo I. S. Silva & Marcos A. S. Barrozo
Chemical Engineering School, Federal University of Uberl^ andia, Block K, Campus Santa M^ onica, CEP 38400-902, Uberl^ andia, MG, Brazil
(Received 27 July 2012; Accepted in revised form 31 October 2012)
Summary This study investigates the drying kinetics of residue of acerola, in a fixed-bed dryer, analysing the effect
of the process variables on the antioxidant properties of the residue. A complete factorial design 3
2
has
been performed, where the independent variables studied were as follows: air velocity (0.5, 1.0 and
1.5 m s
1
) and air-drying temperature (40, 50 and 60 °C). The bioactive compounds studied were
L-ascorbic acid, total phenolic, total flavonoids and antioxidant activity (expressed as IC
50
) was deter-
mined using free radical DPPH
•
. Both independent variables studied have shown to be statistically signifi-
cant. The content of ascorbic acid was the highest at 60 °C and 1.0 m s
1
(126.2 0.004 mg 100 g
1
)
while for the fresh residue 16.12 0.003 mg 100 g
1
, whereas the total phenolic showed the highest
content at 50 °C and 1.5 m s
1
(46.2 0.003 mg gallic acid.100 g
1
) while for the fresh residue
12.59 0.001 mg gallic acid.100 g
1
. The drying conditions play an important role in determining the
final quality of the product mainly in terms of antioxidant activity.
Keywords Antioxidant activity, drying, fruits.
Introduction
The processing of fruits creates a substantial quantity
of residues in the form of peel, seeds and pulps. Stud-
ies have shown that the peel and seeds of certain fruits
can present a higher antioxidant activity than the pulp
(Gorinstein et al., 2001). Antioxidants are the sub-
stances that are able to prevent or inhibit oxidation
processes in human body and food products (Diaz
et al., 1997).
Oxidation is essential to many living organisms for
the production of energy necessary for biological pro-
cesses. Oxygen-centred free radicals, also known as
Reactive Oxygen Species (ROS) are produced in vivo
during oxidation (Babbar et al., 2011). ROS may be
very damaging, as they can attack lipids in cell mem-
branes, proteins in tissues or enzymes, carbohydrates
and DNA to induce oxidations, which cause membrane
damage, protein modification including enzymes and
DNA damage. This oxidative damage is considered to
play a causative role in the degenerative or pathological
processes of various serious diseases in humans, such as
ageing, cancer, cardiovascular diseases, cataract, decline
in the immune system and cerebral dysfunctions (Atoui
et al., 2005). Humans have evolved with antioxidant
systems to protect against free radicals.
It also can be expected high levels of phenolics (e.g.
flavonoids), citric acid and ascorbic acid in some fruit
residues. Phytochemicals, especially phenolics in fruits
are one of the major bioactive compounds known for
health benefits (Babbar et al., 2011). Flavonoids are
the most abundant polyphenolic compounds present in
fruits and vegetables. Flavonoids have long been
associated with a variety of biochemical and pharma-
cological properties, including antioxidant, antiv-
iral, anticarcinogenic, and anti-inflammatory activities
(Middleton et al., 2000). Citric acid has many benefits
to the human body. Citric acid increases effectiveness
of the digestive system. It helps absorb and break
down fats and regulates the body’s pH levels. Citric
acid also prevents bowel dysfunction, and can prevent
urinary tract infections. Ascorbic acid is one of the
important water soluble vitamins. It is essential for
collagen, L-carnitine and neurotransmitters biosynthesis
(Naidu, 2003).
The recovery of fruit residues, to be used in food,
cosmetics and in the pharmacy industry can be an
important alternative for the sustainable development
(Cunha et al., 2009). However, depending on the type
of fruit, the residues can contain a high moisture
content level (80 a 90% wet basis) that can contribute
to the degradation at an accelerated pace (Makris
et al., 2007). One of the methods to conserve the sen-
sorial properties and the bioactive compounds present
*Correspondent: E-mails: gelsleichter_ale@hotmail.com,
masbarrozo@ufu.br
International Journal of Food Science and Technology 2013, 48, 1041–1047
doi:10.1111/ijfs.12060
© 2013 The Authors. International Journal of Food Science and Technology © 2013 Institute of Food Science and Technology
1041