Microwave-assisted treatment for continuous olive paste conditioning: Impact on olive oil quality and yield


Tamborrino, A; Romaniello, R; Zagaria, R; Leone, A

Biosystems Engineering 127: 92-102

2014


BIOSYSTEMS
ENGINEERING
127
(2014) 92-102
Available
online
at
www.sciencedirect.com
ScienceDirect
FT
Q
-
P\
7T1
D
journal
homepage:
www.elsevier.com/locate/issn/15375110
Research
Paper
Microwave-assisted
treatment
for
continuous
olive
paste
conditioning:
Impact
on
olive
oil
quality
and
yield
Antonia
Tamborrino
,
Roberto
Romaniello
,
Riccardo
Zagaria
,
Alessandro
Leone
a
Department
of
Agricultural
and
Environmental
Science,
University
of
Bari
Aldo
Moro,
Via
Amendola
165/A,
70126
Bari,
Italy
b
Department
of
the
Science
of
Agriculture,
Food
and
Environment,
University
of
Foggia,
Via
Napoli,
25,
71122
Foggia,
Italy
®
CrossMark
Olive
paste
conditioning
using
microwave
technology
was
integrated
into
an
olive
oil
extraction
plant
using
industrial-scale
microwave-assisted
apparatus.
This
first
effort
at
integrating
microwave
technology
contributed
significantly
to
the
continuous
conditioning
of
the
olive
paste.
The
components
of
the equipment
were
designed
and
sized
for
optimal
efficiency
in
an
earlier
preliminary
study.
With
the
aim
of
improving
the
operation
of
the
extraction
plants
towards
providing
a
continuous
management
of
the
process,
an
inves-
tigation
of
effects
of
optimal
scheduling
on
olive
oil
quality
was
conducted.
The
objective
was
to
evaluate
the
impact
of
the
microwave
treatment
used
to
condition
the
olive
paste
on
olive
oil
quality
and
yield
and
comparing
it
with
the
conventional
industrial
malaxation.
The
short
process
time
of
the
rapid
microwave
treatment
resulted
in
a
low
oxidation
of
the
olive
oil
and
consequently
a
reduction
in
the
peroxide
value
compared
with
the
conven-
tional
method.
Using
the
microwave
treatment,
a
higher
concentration
of
volatile
com-
pounds
in
the
oil
was
obtained
with
a
lower
content
of
phenolic
compounds
that
are
associated
with
spicy
and
bitter
notes.
No
significant
differences
were
found
with
extraction
yield.
Microwave
processing
was
therefore
confirmed
as
an
attractive
alterna-
tive
to
the
conventional
malaxation,
with
the
main
advantages
being
the
rapid
processing
time
and
the
high
olive
oil
quality.
©
2014
IAgrE.
Published
by
Elsevier
Ltd.
All
rights
reserved.
ARTICLE INFO
Article
history:
Received
1
July
2014
Received
in
revised
form
17
August
2014
Accepted
26
August
2014
Published
online
16
September
2014
Keywords:
Microware
treatment
Olive
oil
extraction
plant
Innovation
Malaxer
Phenols
content
Volatile
compounds
1.
Introduction
The
main
objectives
for
the
designers
of
food
equipment
include
reductions
in
process
time,
improvements
in
energy
efficiency,
reductions
in
labour,
heat
distribution
uniformity,
process
control
and
the
modularity
and
flexibility
of
the
plants
(Rodgers,
2007).
In
the
olive
oil
extraction
process,
the
focus
for
the
introduction
of
new
technologies
is
towards
a
reduction
in
malaxing
time
and
improvements
in
operations
*
Corresponding
author.
Tel.:
+39
0881
589
120.
E-mail
address:
(A.
Leone).
http://dx.doi.org/10.1016/j.biosystemseng.2014.08.015
1537-5110/©
2014
IAgrE.
Published
by
Elsevier
Ltd.
All
rights
reserved.
BIOSYSTEMS
ENGINEERING
127
(2014) 92-102
93
Nomenclature
EVOO
extra
virgin
olive
oil
PLC
programmable
logic
controller
Qu
mass
flow
rate
of
the
modular
unit
(kg
s
-1
)
Fmw
microwave
power
required
(W)
nc
cavity
efficiency
C
p
specific
heat
of
olive
paste
a
kg
-1
K
-1
)
AT
temperature
difference
(K)
V
p
volume
of
the
modular
pipe
(ml)
t
residence
time
(s)
'Y
specific
mass
of
the
olive
paste
(kg
m1
-1
)
EY
extraction
yield
(%)
mass
of
the
extracted
oil
(kg)
Wolves
mass
of
processed
olives
(kg)
SPME
solid-phase
micro-extraction
PDMS/DVB
polydimethylsiloxane/divinylbenzene
MSD
mass
selective
detector
amu
atomic
mass
unit
LOX
lipoxygenase
HPL
hydroperoxide
lyase
management
leading
towards
the
continuous
management
of
the
entire
process.
These
aims
are
closely
linked
to
the
production
of
high-quality
olive
oil
and
high
extraction
yields.
Another
important
aspect
that
must
be
taken
into
account
is
the
reduction
in
the
energy
needs
of
the
process,
thereby
decreasing
both
environmental
and
financial
costs.
Historically,
many
significant
breakthroughs
have
origi-
nated
at
the
interfaces
between
different
fields
of
technol-
ogy.
Microwave
technology
is
an
example
of
a
new
technology
that
is
used
in
many
food
processing
applica-
tions,
which
has
led
to
significant
improvements
in
these
processes
(Catalano,
Fucci,
Giametta,
Penna,
&
La
Fianza,
2013;
Chandrasekaran,
Ramanathan,
&
Basak,
2013;
Dogan-
Halkman,
Yticel,
&
Halkman,
2014;
Kona
et
al.,
2013;
Reyes,
Ceron,
Zuniga,
&
Moyano,
2007;
Schiffmann,
2010;
Xanthakis,
Le-Bail,
&
Ramaswamy,
2014).
The
principle
of
microwave
heating
is
based
on
the
transformation
of
electromagnetic
energy
into
thermal
energy
through
the
direct
interaction
of
the
former
with
polar
molecules
in
a
reaction
mixture
(Venkatesh
&
Raghavan,
2004).
This
volumetric
heating
principle
of
microwaves
can
partially
address
current
heat
transfer
limitations.
Microwave
heating
can
reduce
heat-up
time
and
can
better
preserve
thermo-labile
constituents
(Coronel,
Simunovic,
&
Sandeep,
2003).
The
significant
retention
of
the
quality
attributes
of
foods
treated
by
continuous
flow
microwave
systems
has
been
previously
reported
(Coronel
et
al.,
2003;
Gentry
&
Roberts,
2005).
In
addition,
microwave
heating
has
certain
peculiarities
compared
with
conventional
heating
that
are
related
not
only
to
the
rapid
microwave
heating
rate
but
also
to
the
non-
uniformity
of
the
local
applied
electric
field,
which
serves
to
accelerate
temperature
homogeneity
within
the
material
(Cheng,
Raghavan,
Ngadi,
&
Wang,
2006).
Malaxation
is
a
complex
phase
of
the
olive
oil
extraction
process
that
cannot
be
attributed
solely
to
either
a
simple
"heating'
phase
or
to
a
simple
"kneading'
phase
(Tamborrino,
2014).
The
combined
actions
of
the
time,
temperature
and
kneading
lead
to
important
changes
in
the
olive
paste
microstructure
and
in
the
chemical
and
biochemical
in-
teractions
between
the
substrates
until
a
pre-defined
quality
profile
of
the
extracted
olive
oil
is
obtained
(Amirante,
Clodoveo,
Leone,
&
Tamborrino,
2012;
Angerosa
et
al.,
2004;
Leone,
Romaniello,
Zagaria,
&
Tamborrino,
2014;
Pastore
et
al.,
2014;
Reboredo-RodrIguez,
Gonzalez-Barreiro,
Cancho-Grande,
&
Simal-Gandara,
2014;
Servili
et
al.,
2004;
Tamborrino,
2014;
Tamborrino,
Pati,
et
al.,
2014;
Taticchi
et
al.,
2013).
Although
microwave
radiation
has
wide
uses
in
various
applications
in
the
field
of
food
processing,
research-
aimed
improvements
in
certain
fields
remain
to
be
explored,
especially
in
processes
in
which
the
recovery
of
final
food
products
with
well-defined
sensorial
and
healthy
character-
istics
is
required,
as
is
the
case
of
the
olive
oil.
The
concept
of
utilising
microwave
heating
to
condition
olive
paste
through
the
use
of
an
industrial-sized
micro-
wave-assisted
apparatus,
thereby
replacing
the
conven-
tional
malaxation
process,
has
recently
been
reported
by
the
authors
(Leone,
Tamborrino,
Romaniello,
Zagaria,
&
Sabella,
2014).
In
the
present
study,
an
approach
for
guaranteeing
control
of
the
microwave
apparatus
was
developed
to
ensure
product
quality,
flexibility
and
efficiency
through
the
implementation
of
a
feedback
control
system.
Improvements
in
the
thermal
energy
transfer
efficiency
during
the
olive
paste-conditioning
process
and
reductions
in
processing
time
while
still
obtaining
high-quality
olive
oil
have
been
the
main
challenges
of
this
research.
The
aim
of
the
application
of
the
microwave
technology
in
the
olive
oil
industry
manufacturing
sector
is
to
modify
the
process,
which
normally
consists
of
a
discontinuous
conditioning
of
the
olive
paste
(the
malaxation
process),
by
the
introduction
of
a
continuous
process
to
improve
the
performance
of
the
mechanical
extraction
plant,
thus
saving
malaxation
time,
and
to
develop
system-integrated
machines
that
perform
active
functions
related
to
the
disruption
of
the
water—oil
emulsion,
promoting
coalescence.
In
the
specific
field
of
olive
oil
extraction
plants,
the
innovative
equipment
solu-
tions
should
only
be
considered
after
careful
assessments
of
the
potential
impacts
on
the
quality
of
the
olive
oil
pro-
duced.
The
goal
of
this
work
was
to
address
microwave
applications
during
the
olive
oil
extraction
process
to
highlight
factors
that
affect
innovative
approaches
to
olive
oil
extraction
plants
and
to
investigate
the
adequacy
of
microwave
plant
design
parameters
by
assessing
the
olive
oil
quality
and
yield.
In
this
regard,
extraction
yields,
the
chemical
characteristics
of
the
olive
oil
were
investigated,
and
minor
compounds
such
as
phenols
content
and
volatile
compounds
were
evaluated.
The
sizing
of
a
modular
unit
of
a
microwave-assisted
plant
was
carried
out,
by
improving
a
prototype
microwave-assisted
plant
developed
in
a
previous
research
(Leone,
Tamborrino,
et
al.,
2014).
In
spite
of
the
complex
nature
of
microwave—food
interactions,
the
results
of
this
study
should
be
useful
for
a
better
understanding
of
the
process
and
for
future
industrial
applications.
94
BIOSYSTEMS
ENGINEERING
127
(2014)
92-102
2.
Materials
and
methods
2.1.
Microwave-assisted
treatment
apparatus
A
microwave-assisted
treatment
apparatus
for
conditioning
the
olive
paste
was
sized
and
built
to
allow
a
continuous
flow
of
olive
paste
to
be
exposed
to
a
standing
microwave
field
that
was
formed
in
a
reverberate
tunnel.
The
microwave
heater
was
manufactured
by
EMitech
Srl
(Molfetta,
Italy).
The
microwave-assisted
system
design,
which
was
tested
by
the
authors
in
a
previous
study
(Leone
et
al.,
2014),
was
improved,
making
it
modular,
and
a
feedback
control
system
added
to
automate
the
actions
for
regulating
the
output
olive
paste
temperature.
The
modular
unit
of
the
microwave
plant
has
been
sizing
to
be
adapted
to
different
working
capacity
of
the
mills.
2.1.1.
Sizing
of
a
modular
unit
of
the
microwave-assisted
treatment
apparatus
The
sizing
of
the
modular
unit
was
done
making
these
assumptions:
-
Output
temperature
of
the
olive
paste
from
the
condi-
tioning
operation,
equal
to
28
°C.
-
Output
temperature
of
the
olive
paste
from
the
crushing
operation,
equal
to
20
°C.
-
AT
considered
for
sizing
was
about
8
°C.
-
C
p
value
of
the
olive
paste
was
3250
J
kg
-1
K
-1
(Leone
et
al.,
2014).
The
maximum
power
of
the
magnetron
chosen
for
the
sizing
of
the
modular
unit
was
equal
to
6
kW.
Considering
these
abovementioned
assumptions
the
mass
flow
rate
of
the
modular
unit
(Q
u
)
has
been
calculated
by
using
the
following
equation:
Pmwnc
(
1
)
C
p
AT
where
P
MT
is
the
microwave
power
required
(W),
n,
is
the
cavity
efficiency,
C
p
is
the
specific
heat
of
the
olive
paste
and
AT
is
the
temperature
difference
(K).
The
calculated
Q
u
resul-
ted
706
kg
h
-1
.
Considering
the
mass
flow
rate
of
the
olive
paste,
the
sizing
of
the
polypropylene
pipe
inside
the
modular
unit
has
been
made,
taking
in account
that
the
residence
time
was
equal
to
18
s
and
the
specific
mass
of
the
olive
paste
equal
to
=
1.05
x
10
-3
kg
ml.
Therefore,
the
volume
of
the
olive
paste
treatable
in
the
modular
unit
(equal
to
the
volume
of
the
modular
pipe)
has
been
determined
by
using
the
following
equation:
a
t
V
=
Q
(2)
P
Thus,
the
volume
of
the
modular
pipe
was
equal
to
3358
ml.
Finally,
considering
the
diameter
of
the
modular
pipe
chosen,
equal
to
those
of
the
output
pipe
of
the
feeding
cavity
pump
(65.4
mm),
the
length
of
the
modular
pipe
resulted
equal
to
1000
mm.
To
sizing
of
the
microwave
system
in
a
mill
plant
is
necessary
to
choose
the
number
of
modules
proportional
to
the
maximum
capacity
of
the
mill
and
the
maximum
AT
needed.
To
work
with
lower
AT
is
sufficient
to
reduce
the
power
of
the
magnetron
by
acting
on
the
programmable
logic
controller
(PLC).
The
sized
modular
unit
microwave-assisted
treatment
apparatus
(Fig.
1),
was
made
of
specific
components
and
was
suitably
assembled
to
be
adapted
to
the
different
working
capacities
of
industrial
olive
oil
extraction
plants.
The
modular
unit
consisted
of:
-
A
reverberant
tunnel,
constructed
from
AISI
304
stainless
steel;
-
A
generator
head
(TM060,
ALTER
Srl,
Reggio
Emilia,
Italy);
-
A
power
supply
(SM1180T,
ALTER
Srl,
Reggio
Emilia,
Italy);
-
A
water-cooled
magnetron
head
(YJ1600C,
ALTER
Srl,
Reggio
Emilia,
Italy).
The
magnetron
operated
with
a
fre-
quency
of
2.4
GHz,
and
the
power
supply
can
be
regulated
to
provide
a
variable
power
from
1
to
6
kW;
-
Polypropylene
pipe
with
an
internal
diameter
of
65.4
mm
and
a
length
of
1000
mm,
that
is
mounted
onto
the
broad
face
of
the
reverberant
tunnel.
The
inner
volume
of
the
reverberant
chamber
has
been
chosen
in
order
to
have
a
specific
power
of
4
kW
m
-3
.
2.1.2.
Feedback
control
system
The
feedback
control
system
(
)
was
composed
of
a
PLC,
a
mass
flow
meter
and
two
thermocouples
(model
PT
100).
The
feedback
regulation
system
permitted
the
monitoring
and
regulation
of
the
power
of
the
magnetrons
on
the
basis
of
three
input
parameters:
both
the
input
and
output
tempera-
ture
of
the
olive
paste,
which
were
registered
through
the
two
thermocouples,
and
the
mass
flow
rate
of
the
olive
paste,
measured
through
the
mass
flow
meter
that
was
installed
on
the
output
pipe
of
the
cavity
pump.
The
PLC
(model
PCD1,
Saia
Burgess
Controls
Italia
Srl
-
Monza,
Italy)
was
mounted
in
an
C
Fig.
1
-
Three-dimensional
diagram
of
the
modules
of
the
microwave-assisted
treatment
apparatus.
A)
Reverberant
chamber;
B)
polypropylene
pipe;
C)
magnetron;
D)
power
supply.
Flow
meter
Thermocouple
#1
Paste
inlet
Thermocouple
#2
Paste
outlet
Defoliator
+
-
- -
-
Washing
machine
-
-
-
-
Partial
de-stoner
r•
-
-
PLC
Cavity
pump
+
.
_
.
_
.
BIOSYSTEMS
ENGINEERING
127 (2014) 92-102
95
Magnetron
1
Magnetron
2
Magnetron
3
Magnetron
4
Input
signal
Output
regulation
signal
- - -
Alarm
signal
Fig.
2
Scheme
of
the
feedback
control
system.
operator
panel
(PCD7.D5,
Saia
Burgess
Controls
Italia
Srl
Monza,
Italy)
and
both
programmed
using
the
proprietary
software.
The
PLC
receives
the
analogue
signals
from
the
two
thermocouples
and
the
mass
flow
meter.
The
touch
screen
of
the
PLC
allowed
one
to
set
the
desired
output
temperature
of
the
olive
paste
by
regulating
the
power
out
of
the
magnetrons.
The
software
was
developed
to
take
into
account
the
three
input
parameters
and
the
C,
of
the
olive
paste
(constant
value
equal
to
3310
J
kg
-1
K
-1
),
which
was
determined
calorimetrically
(Leone
et
al.,
2014),
and
to
send
a
digital
signal
to
the
power
supplies
of
the
magnetrons
that
modulated
the
output
electric
power.
The
PLC
also
received
input
signals
from
the
power
supplies
that,
in
case
of
failure,
determine
a
signal
generation
output
from
the
PLC
to
stop
the
motors
and
valves
on
the
machines
upstream
of
the
cavity
pump.
2.1.3.
Assembled
microwave-assisted
treatment
apparatus
During
the
tests,
four
single
modular
units
were
assembled
and
connected
in
a
continuous
manner
to
the
olive
oil
extraction
line
to
evaluate
the
experimental
apparatus
ac-
cording
to
the
work
capacity
of
the
industrial
olive
oil
extraction
plant
and
the
temperature
chosen
for
conditioning
the
olive
paste.
The
units
and
the
feedback
control
system
were
developed
and
implemented
in
the
plant
as
described
in
the
previous
sections,
and
they
represent
the
experimental
microwave-assisted
treatment
apparatus
used
in
the
present
research.
The
schematic
diagram
of
the
experimental
appa-
ratus
is
shown
in
Fig.
3.
2.2.
Olives
and
industrial
olive
oil
extraction
plant
The
experimental
tests
were
conducted
using
the
Ogliarola
Garganica
(Olea
europaea
L.)
cultivar
olives
from
the
2013/
2014
crop
season.
The
olives
were
mechanically
picked
from
the
olive
groves
located
in
the
countryside
near
Foggia
(Puglia,
Italy)
and
were
processed
within
8
h.
The
fruit
ripeness
index,
determined
according
to
the
method
pro-
posed
by
the
International
Olive
Council
(IOOC,
2001),
was
2.7.
The
homogeneous
olive
batches
(700
kg
per
batch)
were
processed
in
an
industrial
oil
extraction
plant
(Alfa
Laval,
Sweden)
that
had
implemented
the
microwave-assisted
treatment
apparatus.
The
olive
fruits
were
defoliated
and
cleaned,
and
then
they
were
crushed
using
a
partial
de-
stoner
mill
(Pietro
Leone
e
Figli
s.n.c.,
Foggia
Italy).
This
machine
removed
about
50%
of
the
stone
fragments,
whereas
the
remaining
50%
of
the
fragments
of
stone
continued
in
the
process.
The
olive
paste
was
successively
processed
separately
using
either
the
traditional
close-top
malaxer
with
a
cover
partially
fissured
or
the
microwave-
assisted
apparatus
developed.
The
experimental
apparatus
was
placed
between
the
partial
de-stoner
and
the
decanter.
The
olive
oil
was
separated
by
means
of
a
three-phase
decanter
(mod.
NX
X32,
Alfa
Laval
Corporate
AB,
Lund,
Sweden)
and
was
finally
centrifuged
using
a
vertical
disc
stack
centrifuge.
2.3.
Test
programme
In
this
research
programme,
three
different
industrial
plant
configurations
were
tested
to
compare
three
different
methods
for
conditioning
the
olive
paste.
The
use
of
micro-
wave
energy
in
a
continuous
flow
of
olive
paste
was
compared
with
the
conventional
malaxation
operation,
which
occurred
in
a
standard
malaxer
machine
(Fig.
4).
To
provide
a
contin-
uous
flow
the
microwave-assisted
apparatus
was
sized
as
described
earlier
and
was
used
during
the
experimental
tests.
Test
1.
The
extraction
plant
used
the
malaxer
machines
to
condition
the
olive
paste.
The
malaxation
temperature
was
set
to
28
°C,
and
the
duration
process
was
40
min.
Test
2.
The
extraction
plant
used
the
microwave-assisted
treatment
apparatus
instead
of
the
malaxer
machines.
The
outlet
temperature
was
set
to
28
°C
using
the
control
system.
Test
3.
As
a
first
treatment,
the
extraction
plant
used
the
microwave
apparatus
and
then
successively
used
the
""""
.........
F
F
F
F
G
A
1
1
Fig.
3
Scheme
of
the
microwave-assisted
treatment
apparatus
and
the
feedback
control
system
implemented
in
the
industrial
mill.
A)
Olive
paste
from
partial
de-stoner;
B)
cavity
pump;
C)
mass
flow
meter;
D)
PLC;
E)
power
supplies;
F)
magnetrons;
G)
decanter;
H)
liquid
phases
to
vertical
centrifuge;
I)
husk
discharge.
96
BIOSYSTEMS
ENGINEERING
127
(2014)
92-102
Defoliator
MWS
Washing
machine
H
Malaxer
1
Partial
de-
stoner
H
Malaxer
2
H
Malaxer
3
H
H
Malaxer
4
H
H
Malaxer
5
H
Malaxer
6
1—
L
_
_
_
I
L
_
_
Decante
Vertical
—>
centrifuge
Fig.
4
-
Plant
configurations
tested:
solid
line
is
Test
1;
dashed
line
is
Test
2;
dotted
line
is
Test
3.
malaxer
machines
as
a
second
step.
The
olive
paste
con-
ditioning
began
in
the
microwave
apparatus
at
28
°C
and
ended
in
the
malaxer
machines,
where
it
was
malaxed
for
20
min
at
28
°C.
The
malaxing
time
did
not
include
the
times
required
to
load
and
unload
the
malaxer.
Each
test
was
replicated
four
times.
During
all
three
tests,
the
mass
flow
rate
of
the
plat
was
3000
kg
h".
Considering
the
volume
of
the
poly-
propylene
pipe
for
the
four
assembled
units
and
the
mass
flow
rate
chosen
for
the
microwave
apparatus,
the
residence
time
for
the
treatments
in
the
microwave
apparatus
was
17
s.
Three
samples
of
olive
oil
obtained
from
each
test
were
acquired
and
stored
in
dark
bottles
at
4
°C
until
analysed.
2.4.
Extraction
yield
The
extraction
yield
(EY)
is
the
amount
of
oil
that
is
obtained
through
the
milling
of
100
kg
of
olives.
The
EY
was
calculated
using
the
following
equation:
EY
-
W°I1
100
(3)
vv
olives
where
Wa
is
the
mass
of
the
extracted
oil
(kg)
and
W
oi
i
ves
is
the
mass
of
the
processed
olives
(kg).
2.5.
Extra
virgin
olive
oil
analyses
2.5.1.
Marketable
parameters
The
free
acidity,
expressed
as
the
percentage
of
oleic
acid,
and
the
peroxide
value,
expressed
as
milli-equivalents
of
active
oxygen
per
kilogram
of
oil
(meq
[0
2
]
kg
-1
[oil])
were
deter-
mined
according
to
the
methods
described
in
the
European
Union
standard
methods
and
subsequent
amendments
(EC,
1991).
2.5.2.
Phenolic
compounds
The
total
phenolic
content
and
phenolic
profile
analysis
were
determined
from
the
oils
through
a
liquid-liquid
extraction
with
methanol
according
to
the
procedure
reported
by
Gambacorta,
Previtali,
Pati,
Baiano,
and
La
Notte
(2006).
2.5.3.
Volatile
compounds
Volatile
compounds
were
extracted
from
the
olive
oil
using
the
solid-phase
micro-extraction
(SPME)
technique
and
were
analysed
by
gas
chromatography
coupled
to
mass
spectrom-
etry
(GC/MS).
Using
2-methyl-1-pentanol
as
the
internal
standard
(IS)
at
a
concentration
of
10.25
mg
kg
-1
,
3
g
oil
sample
were
intro-
duced
into
a
10
ml
headspace
vial
fitted
with
a
polytetrafluoroethylene-lined
septum
and
sealed
with
an
aluminium
seal.
The
volatile
compounds
were
extracted
by
exposing
the
SPME
(polydimethylsiloxane/divinylbenzene,
PDMS/DVB,
50/30
Ian,
20
mm
long)
fibres
(Supelco
Ltd.,
Belle-
fonte,
PA,
USA)
for
30
min
in
the
bottle,
which
was
placed
in
a
40
°C
water
bath
during
the
extraction.
The
SPME
device
was
then
removed
from
the
vial
and
immediately
inserted
into
the
injection
port
of
a
GC/MS
system
(split-less
mode)
for
thermal
desorption
at
250
°C
for
4
min.
A
6890N
series
gas
chromatograph
(Agilent
Technologies
Inc.,
Santa
Clara,
CA,
USA)
with
an
Agilent
5975C
mass
se-
lective
detector
(MSD)
and
equipped
with
a
DB-Wax
capillary
column
(60
m
x
0.25
mm
internal
diameter,
0.25
Ian
film
thickness,
J&W
Scientific
Inc.,
Folsom,
USA)
was
used
to
analyse
the
volatile
compounds.
Helium
was
used
as
the
carrier
gas
at
a
flow
rate
of
1.0
ml
min
-1
.
The
oven
temperature
was
set
at
40
°C
for
4
min,
followed
by
a
temperature
gradient
of
3
°C
min
-1
to
140
°C,
with
a
final
post-run
of
10
min
at
200
°C.
The
mass
spectrometer
was
operated
in
electron
impact
mode
(ionisation
energy,
70
eV)
using
a
mass
range
of
m/z
30-400
amu.
Compound
identification
was
performed
by
comparing
the
retention
times
of
unknowns
with
those
of
standard
compounds
and
by
matching
the
mass
spectra
with
those
from
the
data
system
library
(NIST11,
P
>
90%).
Quan-
tification
was
achieved
by
normalising
the
compound
peak
BIOSYSTEMS
ENGINEERING
127
(2014) 92-102
97
area
to
that
of
the
internal
standard
and
multiplying
by
the
internal
standard
concentration.
The
concentration
of
each
volatile
compound
was
expressed
as
mg
internal
standard
equivalents
kg
-1
[oil].
2.6.
Statistical
analysis
All
experimental
data
were
analysed
using
the
Duncan
test
(p
<
0.05)
using
the
Statistics
Toolbox
of
Matlab
®
(The
Math-
works
Inc.,
Natick,
MA,
USA).
3.
Results
and
discussion
3.1.
Microwave-assisted
treatment
apparatus
evaluation
and
its
impact
on
olive
oil
quality
and
yield
3.1.1.
The
impact
of
the
microwave
apparatus
on
marketable
parameters
The
results
of
the
marketable
parameters
are
shown
in
Table
.
No
significant
differences
were
observed
for
the
free
acidity.
The
peroxide
values
showed
significant
differences
between
the
conditions
investigated.
Specifically,
the
conditions
under
which
the
olive
paste
spent
time
in
the
malaxer
machine
(Test
1
and
Test
3)
resulted
in
increased
peroxide
values
compared
with
those
obtained
in
Test
2
(olive
paste
conditioning
using
the
microwave-assisted
treatment).
This
effect
can
certainly
be
ascribed
to
the
low
contact
with
atmospheric
oxygen
dur-
ing
Test
2,
which
prevented
the
lipid
autoxidation
reactions,
resulting
in
a
decreased
formation
of
peroxides.
The
use
of
the
malaxer
machine
enabled
the
contact
of
the
olive
paste
with
the
atmosphere
for
40
min
in
addition
to
the
loading
and
unloading
operations.
In
contrast,
through
the
use
of
the
mi-
crowave
apparatus,
the
continuous
flow
of
olive
paste
through
the
reverberant
tunnel
in
a
closed
pipe
avoided
contact
with
the
oxygen
atmosphere.
Additionally,
the
reduction
of
the
kneading
time
led
to
a
reduction
in
the
number
of
peroxides
that
were
formed.
These
results
confirmed
the
results
previ-
ously
reported
by
Esposto
et
al.
(2013)
and
Leone,
Romaniello,
et
al.
(2014).
3.1.2.
The
impact
of
the
microwave
apparatus
on
phenolic
compounds
The
impact
of
the
microwave
radiation
on
the
concentration
and
composition
of
phenolic
compounds
of
the
extra
virgin
olive
oil
(EVOO)
was
investigated
using
an
apparatus
suitably
designed
to
be
used
in
an
olive
oil
extraction
plant.
As
shown
in
Table
1,
the
microwave
treatment
affected
the
phenol
content
of
the
virgin
olive
oil,
as
the
total
amount
detected
in
the
oils
obtained
under
the
three
conditions
resulted
in
significantly
different
amounts
of
phenols.
The
lowest
phenol
content
in
the
EVOO
was
obtained
when
the
microwave-assisted
treatment
apparatus
was
used
(Test
2),
while
the
oils
obtained
from
Test
1,
the
traditional
malax-
ation
treatment,
was
characterised
by
higher
values
of
phe-
nols.
The
amount
of
phenols
is
strictly
related
to
the
activities
of
various
endogenous
enzymes
of
olive
fruit
that
are
acti-
vated
during
the
extraction
process
(Servili
et
al.,
2004).
As
reported
in
other
studies,
the
main
enzymes
that
have
been
implicated
in
the
release
of
the
phenols
into
the
oil
are
the
endogenous
pectinases,
hemi-cellulases,
and
cellulases
that
hydrolyse
the
cell
wall,
thus
increasing
the
amounts
of
phenolic
compounds
that
are
released
into
the
oil
and
vege-
tation
water
during
processing
(Heredia,
Gullien,
Jimenez,
&
Bolarios,
1993;
Vierhuis
et
al.,
2001).
In
this
context,
the
length
of
time
of
the
malaxation
significantly
affected
the
phenolic
content
(Servili
et
al.,
2004).
The
oil
extraction
from
the
olive
pastes
performed
with
the
microwave-assisted
apparatus
reduced
the
time
that
was
available
for
the
action
of
the
depolymerising
enzymes,
which
corresponded
to
a
decreased
release
of
the
phenolic
compounds
into
the
oil.
Similar
results
were
previously
obtained
using
a
flash
thermal
machine
instead
of
the
malaxers
for
olive
paste
conditioning
(Esposto
et
al.,
2013).
The
flash
thermal
machine
is
a
heat
exchanger
consisting
of
concentric
tubes
that
reduces
the
conditioning
time
of
the
olive
paste
to
a
few
minutes.
Table
2
shows
the
phenolic
composition
of
the
oils
that
were
obtained
during
the
tests.
The
individual
phenols
that
were
investigated
maintained
the
same
trend
as
that
of
the
total
phenolic
content
for
the
different
trials
studied.
The
only
exception
was
that
of
(+)-pinoresinol,
which
exhibited
a
different
trend.
The
amounts
of
certain
secoiridoid
derivatives,
specifically
3,4-DHPEA-EDA,
p-HPEA-EA
and
p-HPEA-EDA,
were
signifi-
cantly
lower
in
the
oils
that
were
rapidly
treated
with
the
microwave
radiation
(Test
2)
than
those
that
were
investi-
gated
in
the
samples
treated
in
the
traditional
manner
(Test
1).
These
substances
are
derived
from
the
enzymatic
conversion
of
phenolic
glycosides
of
the
olive
fruit,
such
as
oleuropein
and
ligustroside,
by
the
endogenous
B-glucosidase
(Servili
et
al.,
2004).
Because
oleuropein
is
contained
in
the
vacuoles
of
the
olive
mesocarp
cells,
the
detection
of
B-glucosidase
activity
in
the
mesocarp
cell
chloroplasts
clearly
indicates
that
the
enzyme
and
substrate
are
kept
in
different
cell
compart-
ments
(Mazzuca,
Spadafora,
&
Innocenti,
2006).
The
decreased
time
employed
using
the
microwave
apparatus
prevents
the
enzyme
activity
from
hydrolysing
the
phenolic
glycosides,
resulting
in
decreased
amounts
of
secoiridoid
derivatives
detected.
Those
results
can
be
explained
by
considering
dif-
ferences
in
terms
of
the
activation
period
of
the
depolymer-
ising
enzymes
between
the
rapid
microwave
treatment
(Test
2)
and
the
slow
traditional
malaxing
process
(Test
1).
Table
1
Marketable
parameters
and
total
phenol
content.
Test
conditions
Free
acidity
(%)
Peroxide
value
(meq
[0
2
]
kg
1
[oil])
Total
phenol
content
(mg
kg
1
)
Test
1
0.57
±
0.02
a
8.1
±
0.4
a
407
±
10
b
Test
2
0.58
±
0.03
a
6.9
±
0.1
c
354
±
9
c
Test
3
0.62
±
0.06
a
7.3
±
0.2
b
447
±
14
a
Data
represents
mean
value
±
standard
deviation.
Different
letters
in
the
same
column
denotes
statistical
significant
differences
(p
<
0.05).
98
BIOSYSTEMS
ENGINEERING
127 (2014) 92-102
Table
2
-
Phenolic
composition
of
olive
oil.
Data
expressed
as
mg
kg'
equivalents
of
IS.
Retention
time
(min)
Phenols
Test
1
Test
2
Test
3
6.6
p-HPEA
0.964
±
0.040
b
0.154
±
0.008
c
1.094
±
0.017
a
36.8
3,4-DHPEA-EDA
6.160
±
0.250
b
5.280
±
0.010
c
7.480
±
0.070
a
37.8
p-HPEA-EDA
2.430
±
0.090
a
2.040
±
0.050
b
2.500
±
0.050
a
39.3
(+)-Pinoresinol
0.840
±
0.019
b
0.959
±
0.069
a
0.695
±
0.008
c
42.8
3,4-DHPEA-EA
4.030
±
0.250
b
3.820
±
0.070
b
5.390
±
0.140
a
45.2
p-HPEA-EA
0.680
±
0.029
b
0.462
±
0.015
c
0.995
±
0.016
a
Data
represents
mean
value
±
standard
deviation.
Different
letters
in
the
same
row
denotes
statistical
significant
differences
(p
<
0.05).
It
has
been
suggested
by
several
studies
that
these
secoir-
idoids
are
the
main
molecules
responsible
for
"bitter"
and
"spicy"
notes.
In
particular,
both
3,4-DHPEA-EDA
and
p-HPEA-
EA
appear
to
contribute
to
the
"bitter"
note
(Catania
et
al.,
2013;
Gutierrez-Rosales,
Rios,
&
Gomez-Rey,
2003;
Tambor-
rino,
Pati,
et
al.,
2014),
while
p-HPEA-EDA
appears
to
be
asso-
ciated
with
the
"spicy"
note
(Andrewes,
Busch,
de
Joode,
Groenewegen,
&
Alexandre,
2003).
Because
the
secoiridoids
affect
the
quality
of
the
sensory
and
health
properties
of
the
EVOO
(Gambacorta,
Faccia,
Trani,
Lamacchia,
&
Gomes,
2012;
Servili
et
al.,
2004),
determining
bitter,
pungent
sensations,
the
microwave
treatment
used
to
condition
the
olive
paste
could
open
new
scenarios
for
the
oils
produced
by
some
cultivars
that
are
rich
in
polyphenols
and
that
are
identified
as
"bitter",
e.g.,
the
cultivar
Coratina,
miti-
gating
the
attributes
that
not
always
desired
by
consumers.
Thus,
the
development
of
microwave
equipment,
specif-
ically
designed
for
the
olive
oil
industrial
plants,
could
have
interesting
implication
to
the
specific
needs
of
the
olive
oil
process.
3.1.3.
The
impact
of
the
microwave
apparatus
on
volatile
compounds
The
qualitative-quantitative
evaluation
of
the
EVOO
volatile
compounds
with
the
HP-SPME-GC/MS
was
investigated.
The
differences
in
the
amounts
of
volatile
compounds
resulted
mainly
from
the
reduction
in
time
of
the
conditioning,
which
affects
the
biochemical
events
that
underlie
the
formation
of
the
volatile
compounds.
Table
3
presents
the
identified
C5
and
C6
carbonyl
com-
pounds,
which
represent
the
most
important
fraction
of
vol-
atile
compounds
found
in
high-quality
EVOO
(Kalua
et
al.,
2(
).
The
concentrations
of
C6
and
C5
compounds,
produced
from
polyunsaturated
fatty
acids
by
the
enzymatic
activities
exerted
by
the
lipoxygenase
(LOX)
pathway,
depend
on
the
level
and
the
activity
of
each
enzyme
involved
in
this
LOX
pathway
(Kalua
et
al.,
2007;
Sanchez-
Ortiz,
Perez,
&
Sanz,
2013).
Except
for
(EE)-2,4-hexadienal,
which
did
not
show
signif-
icant
differences
between
the
trials,
the
values
shown
in
Table
3
indicate
that
the
oils
obtained
by
the
rapid
microwave
treatment
(Test
2)
were
characterised
by
a
greater
concen-
tration
of
C6
and
C5
compounds
than
either
Test
1
or
Test
3,
each
of
which
required
longer
times.
Additionally,
a
signifi-
cant
decrease
in
pentan-3-one
was
followed
by
a
considerable
increase
of
penten-3-one
from
Test
1
to
the
Test
2.
This
trend
was
probably
due
to
the
oxidation
of
pentan-3-one
to
penten-
3-one.
The
volatile
compounds
that
exhibited
the
greatest
in-
crease
by
the
rapid
microwave
conditioning
compared
with
the
traditional
malaxation
operation
were
penten-3-one,
(Z)-2-pentenol,
hexanal
and
(E)-2-hexenal,
which
increased,
respectively,
from
0.11
to
1.91,
from
0.040
to
0.131,
from
0.71
to
1.49,
and
from
4.43
to
6.31
mg
equivalents
of
IS.
Penten-3-one
and
(Z)-2-pentenol
are
associated
with
"fruity"
and
"green"
attributes
(Morales,
Alonso,
Rios,
&
Aparicio,
1995;
Pouliarekou
et
al.,
2011),
while
hexanal
is
associated
with
notes
of
"grassy",
"green-fresh"
and
"green
apple"
(Kalua
et
al.,
Table
3
-
Volatile
compounds
detected
in
extra
virgin
olive
oils.
C5
and
C6
carbonilic
compounds
Rta
Test
1
Test
2
Test
3
Pentan-3-one
10.8
1.49
±
0.09
a
0.85
±
0.05
b
1.55
±
0.04
a
Penten-3-one
12.5
0.11
±
0.01
c
1.91
±
0.09
a
1.65
±
0.05
b
Hexanal
15.0
0.71
±
0.02
c
1.49
±
0.08
a
0.90
±
0.03
b
2-Methyl-propanol
15.7
0.15
±
0.01
c
0.66
±
0.04
a
0.55
±
0.01
b
Penten-3-ol
18.8
0.14
±
0.01
c
0.38
±
0.02
a
0.25
±
0.01
b
(E)-2-Hexenal
21.6
4.43
±
0.12
c
6.31
±
0.29
a
5.88
±
0.24
b
(Z)-2-Pentenol
26.4
0.040
±
0.001
c
0.131
±
0.005
a
0.080
±
0.002
b
Hexanol
27.9
0.36
±
0.01
c
0.63
±
0.02
a
0.52
±
0.01
b
(Z)-3-Hexenol
29.3
0.033
±
0.001
c
0.086
±
0.003
a
0.063
±
0.002
b
(E.E)-2,4-Hexadienal
30.1
0.032
±
0.002
a
0.038
±
0.012
a
0.025
±
0.002
a
(E)-2-Hexenol
30.2
0.39
±
0.01
c
0.90
±
0.03
a
0.55
±
0.02
b
Sum
7.88
±
0.15
13.38
±
0.32
12.00
±
0.25
Data
are
expressed
as
mg
[internal
standard
equivalents]
kg
-1
[oil]
±
standard
deviation
(n
=
4).
Different
letters
in
the
same
row
denotes
statistical
significant
differences
(p
<
0.05).
a
Rt
=
retention
time
(min).
BIOSYSTEMS
ENGINEERING
127
(2014) 92-102
99
2007).
(E)-2-Hexenal
is
inversely
related
to
the
degree
of
oxidation
(Kalua
et
al.,
2007).
Generally,
the
oils
that
were
obtained
from
the
combined
treatment
(microwave
and
con-
ventional
malaxation)
(Test
3),
showed
an
intermediate
value
of
aromatic
content
with
respect
to
the
oils
that
were
obtained
from
Test
1
and
2.
Principal
component
analysis
helped
explain
the
observed
changes
in
the
volatile
compounds
among
the
different
trials
(Fig.
5).
PC1
and
PC2
explained
92.45%
and
6.88%
of
the
total
variance,
respectively.
With
PC1,
the
highly
discriminated
virgin
olive
oils
produced
by
traditional
malaxation
(Test
1,
located
in
the
left
part
of
the
plot)
had
negative
high
scores,
whereas
the
samples
that
were
obtained
using
the
microwave
treatment
(Tests
2
and
3)
had
positive
first
component
scores.
The
oils
obtained
from
the
microwave
treatment
(Test
2)
were
located
closer
to
the
abscissa
in
the
first
quadrant.
These
results
confirm
that
the
amount
of
volatile
com-
pounds
increase
when
the
time
of
the
conditioning
is
very
fast.
Angerosa,
D'Alessandro,
Basti,
and
Vito
(1998)
com-
mented
that
after
the
very
rapid
synthesis
of
volatile
com-
pounds
that
occurs
from
cell
disruption
during
milling,
the
partitioning
phenomena
between
the
oils
and
aqueous
phases
would
be
the
main
factor
responsible
for
the
variations
of
the
volatile
compounds
content
in
the
oils
during
the
olive
paste
malaxation.
Thus,
the
decrease
in
processing
time
with
the
microwave
treatment
could
affect
the
distribution
phenome-
non.
In
addition,
another
reason
for
the
lack
of
volatile
com-
pound
synthesis
during
conventional
malaxation
remains
unclear,
but
it
might
be
associated
with
a
deactivation
of
the
enzymes
of
the
LOX
pathway
by
components
in
the
olive
paste,
such
as
oxidised
phenolics
that
arise
during
the
milling
step
(Sanchez-Ortiz
et
al.,
2013).
This
inactivating
role
of
oxi-
dised
phenolics
on
enzymatic
activity
is
well
established
(Chedea,
Braicu,
&
Socaciu,
2012;
Loomis,
1969;
Loomis
&
Battaile,
1966),
and
it
can
contribute
to
reductions
in
the
effective
enzyme
activity
load
during
the
oil
extraction
pro-
cess
(Sanchez-Ortiz
et
al.,
2013).
Therefore,
it
is
suggested
that
the
variability
in
the
volatile
compounds
content
during
the
olive
paste
conditioning
was
due
to
the
different
time—temperature
profiles
of
the
three
different
trials
compared.
These
different
parameters
caused
different
activity
levels
of
the
LOX
pathway
(Angerosa
et
al.,
2004).
Moreover,
as
reported
by
Sanchez-Ortiz
et
al.
(2013),
the
synthesis
of
EVOO
volatile
compounds
may
also
depend
on
the
activity
of
hydroperoxide
lyase
(HPL),
which
cleaves
the
polyunsaturated
fatty
acid
hydroperoxides
that
are
produced
during
the
oil
extraction
process.
Moreover,
the
increase
in
C6
aldehydes
that
were
observed
in
the
oils
obtained
from
the
rapid
microwave
treatment
was
due
to
the
activity
of
HPL.
The
short
time
needed
for
the
thermal
treatment
of
the
olive
paste
with
the
microwave-
assisted
treatment
apparatus
compared
with
the
traditional
process
reduced
the
partial
inactivation
of
the
HPL,
promoting
an
increased accumulation
of
C6
aldehydes.
The
results
confirmed
that
the
olive
oil
extracted
using
the
microwave
apparatus
exhibited
a
higher
amount
of
C6
aldehydes
compared
with
the
olive
oil
obtained
with
the
traditional
malaxation.
3.1.4.
Extraction
yield
and
final
evaluation
of
the
microwave-
assisted
treatment
apparatus
In
this
study,
experimental
tests
have
been
carried
out
to
evaluate
the
extraction
yield.
No
significant
differences
were
found
regarding
the
extraction
yields
between
the
tests
compared
(data
not
shown).
These
results
confirm
previously
reported
results
(Leone
et
al.,
2014).
The
developed
microwave-assisted
treatment
apparatus
was
shown
to
be
flexible
for
application
in
olive
oil
industry
and
was
rapidly
developed
to
meet
the
requirements
of
the
mill.
The
apparatus
comprised
a
feedback
regulation
that
ensured
the
supervision
of
the
correct
operation
of
the
plant.
The
control
and
monitoring
concepts
provided
for
in
this
experimentation
improved
plant
performance,
and
it
can
be
installed
during
normal
production
so
that
the
plant
operation
is
not
disturbed.
The
feedback
control
system
is
accessible
and
economical
today,
and
the
statistical
process
control
can
be
employed
as
an
excellent
tool
in
total
quality
management
(Aiello
et
al.,
2012;
Leone,
Romaniello,
&
Tamborrino,
2013;
20
15
10
Pentait-3-one
Test
3
.
.•
5
Penten-3-one
(E)-2-Hexenal
0
2-meth
-Propanol
i '
-5
Test
1
(Z)-3-Hexenol
.
Test
2
Penten-3-ol
-10
(Z)-2-Pentenol
(E)-2-1-lexenol
-15
1-lexanal
-20
(E,E)-2,4-I
Iexadienal
-20
-15
-10
-5
0
5
10
15
20
Component
1
(92.45
%)
Fig.
5
The
principal
component
analysis
diagram
of
the
volatile
compounds
among
the
tests.
Comp
onen
t
2
(
6.
88
%)
100
BIOSYSTEMS
ENGINEERING
127 (2014) 92-102
Tamborrino,
Pati,
et
al.,
2014;
Tamborrino,
Catalano,
&
Leone,
2014).
Communications
between
the
feedback
system
could
be
refined
to
assemble
a
monitoring
system
with
increased
autonomy.
The
microwave-assisted
apparatus
tested
positively,
and,
although
it
possesses
room
for
improvement,
it
can
reach
a
commercialisation
phase.
It
constitutes
an
innovative
and
currently
the
most
advanced
solution
for
the
continuous
conditioning
of
olive
paste.
Some
effort
must
be
put
also
into
educating
the
olive
oil
industry
about
new
technologies
and
their
applications.
3.2.
Prospective
of
microwave
application
in
olive
oil
extraction
plants
The
knowledge
of
the
effects
of
the
microwave
treatment
on
the
olive
oil
quality
and
yield
could
open
new
prospective
for
the
innovation
in
olive
oil
extraction
plants.
The
main
result
of
this
research
is
the
use
of
the
microwave-assisted
apparatus
for
determining
a
great
reduction
of
the
kneading
time
and
consequently
of
the
entire
process
time
without
compromise
the
quality
and
the
yield.
This
could
be
the
first
result
towards
a
continuous
olive
oil
process.
In
addition,
the
olive
oil
quality
obtained
opens
some
considerations
regard
the
operative
management
of
the
process
as
well
as
on
the
mechanical
so-
lution
of
the
plants.
The
future
goal
could
be
to
develop
an
integrated
system
conditioning
the
olive
paste
constituted
by
processing
tech-
nologies
that
perform
the
malaxing
phase
to
obtain
the
opti-
mum.
In
order
to
adapt
the
extraction
plants
both
to
the
olive
characteristics
(i.e.
cultivar
or
maturation
index)
and
to
the
oil
obtained
could
be
useful
the
introduction
of
a
"modular
olive
oil
extraction
plant"
including
different
olive
paste
condi-
tioning
equipment.
This
innovation
allows,
in
real
time,
the
selection
of
more
appropriate
conditioning
processes
for
the
required
results.
4.
Conclusions
In
this
study,
the
suitability
of
the
microwave
treatment
for
conditioning
olive
paste
was
compared
with
the
conventional
approach
using
malaxation.
For
this
purpose,
a
microwave-
assisted
treatment
apparatus
with
a
feedback
control
sys-
tem
was
implemented
in
an
olive
oil
extraction
line,
and
the
olive
oil
quality
and
yield
were
evaluated.
The
developed
mi-
crowave
apparatus
was
shown
to
be
flexible
for
application
in
industry
and
was
rapidly
developed
to
meet
the
requirements
of
the
mill.
The
comparison
with
the
traditional
malaxation
approach
showed
that
no
significant
differences
were
found
regarding
the
extraction
yield.
The
use
of
the
innovative
microwave
treatment
allowed
a
rapid
and
volumetric
heating
of
the
olive
paste,
and
it
considerably
reduced
the
overall
processing
time
by
allowing
a
continuous
flow
of
olive
paste
during
conditioning.
The
decreased
process
time
resulted
in
a
lower
oxidation
of
the
olive
oil
and
consequently
a
reduction
in
the
peroxide
value
compared
with
the
traditional
method
as
confirmed
by
the
results
of
the
quality
parameters,
thus
improving
the
quality
of
the
olive
oil.
An
interesting
aspect
of
this
research
was
revealed
by
the
phenolic
compounds
content.
The
use
of
the
microwave
treatment
caused
a
reduction
of
the
phenolic
compounds
due
to
the
reduced
time
that
was
needed
for
the
action
of
depolymerising
enzymes.
Moreover,
the
phenolic
compounds
that
are
associated
with
spicy
and
bitter
notes
were
found
in
lower
amounts
in
the
oils
that
were
obtained
using
the
microwave-assisted
treatment
apparatus
compared
with
those
obtained
with
traditional
conditioning
in
the
malaxer
machine.
Some
mono-varietal
oils
are
characterised
by
high
spicy
and
bitter
notes,
such
as
the
Coratina
olive
oil
variety.
These
notes,
even
when
considered
as
positive
attributes,
can
reduce
acceptance
by
the
consumers
if
present
in
high
con-
centrations.
In
fact,
many
mono-varietal
oils
are
often
blended
with
other
olive
oils
to
reduce
the
spicy
and
bitter
notes.
Thus,
the
use
of
microwaves
could
be
a
valid
tool
for
controlling
the
amounts
of
phenolic
compounds
responsible
for
the
spicy
and
bitter
notes
of
the
oils,
which
could
be
important
for
increasing
the
marketability
of
certain
mono-
varietal
oils.
Another
advantage
of
reducing
the
overall
conditioning
time
is
the
different
activity
level
of
the
LOX
pathway,
which
produces
an
increase
in
the
aromatic
substances
of
the
oils
obtained
using
the
microwave-assisted
treatment
apparatus
compared
with
those
obtained
by
traditional
malaxation.
In
addition,
to
the
quantitative
and
qualitative
results
previously
exposed,
is
important
to
consider
that
the
use
of
the
microwave
conditioning
system
of
the
olive
paste
allows
to
obtain
various
benefits
such
as,
drastic
reduction
of
the
olive
paste
conditioning
time
as
well
as
the
total
olive
pro-
cessing
time,
uniform
time—temperature
profile
of
the
olive
paste,
smaller
footprint
of
the
plant
and
a
continuous
process.
Furthermore,
the
"modular
solutions"
allows
to
easily
adapt
the
olive
paste
conditioning
equipment
to
different
mills.
The
feedback
regulation
system
permits
the
adjustment
in
real
time
of
the
output
temperature
of
the
olive
paste
by
regulation
both
of
feeding
flow
rate and
of
magnetrons
power.
Besides,
it
is
possible
to
stop
the
motors
and
valves
on
the
machines
upstream
of
the
cavity
pump
in
case
of
outbreaks
of
the
mi-
crowave
system.
The
described
aspects
should
be
considered
in
designing
and
laying
out
of
new
olive
oil
machinery
and
equipment
for
olive
oil
extraction
industry.
These
results
confirm
that
it
is
reasonable
to
implement
the
microwave
system;
however,
further
studies
on
different
varieties
and
on
using
different
crusher
machines
could
be
useful
to
validate
these
results.
REFERENCES
Aiello,
G.,
Catania,
P.,
Enea,
M.,
La
Scalia,
G.,
Pipitone,
F.,
&
Vallone,
M.
(2012).
Real
time
continuous
oxygen
concentration
monitoring
system
during
malaxation
for
the
production
of
virgin
olive
oil.
Grasas
y
Aceites,
63(4),
475-483.
Amirante,
P.,
Clodoveo,
M.
L.,
Tamborrino,
A.,
&
Leone,
A.
(2012).
A
new
designer
malaxer
to
improve
thermal
exchange
enhancing
virgin
olive
oil
quality.
Acta
Horticulturae
(ISHS),
949,
455-462.
Andrewes,
P.,
Busch,
J.
L.
H.
C.,
de
Joode,
T.,
Groenewegen,
A.,
&
Alexandre,
H.
(2003).
Sensory
properties
of
virgin
olive
oil
polyphenols:
identification
of
deacetoxy-ligstroside
aglycon
as
BIOSYSTEMS
ENGINEERING
127 (2014) 92-102
101
a
key
contributor
to
pungency.
Journal
of
Agricultural
and
Food
Chemistry,
51,
1415-1420.
Angerosa,
F.,
D'Alessandro,
N.,
Basti,
C.,
&
Vito,
R.
(1998).
Biogeneration
of
volatile
compounds
in
virgin
olive
oil:
their
evolution
in
relation
to
malaxation
time.
Journal
of
Agricultural
and
Food
Chemistry,
46(8),
2940-2944.
Angerosa,
F.,
Servili,
M.,
Selvaggini,
R.,
Taticchi,
A.,
Esposto,
S.,
&
Montedoro,
G.
(2004).
Volatile
compounds
in
virgin
olive
oil:
occurrence
and
their
relationship
with
the
quality.
Journal
of
Chromatography
A,
1054,
17-31.
Catalano,
P.,
Fucci,
F.,
Giametta,
F.,
Penna,
A.,
&
La
Fianza,
G.
(2013).
Experimental
system
and
tests
to
optimize
a
tomato
drying
process.
The
Open
Agriculturae
Journal,
7,
73-79.
Catania,
P.,
Vallone,
M.,
Pipitone,
F.,
Inglese,
P.,
Aiello,
G.,
&
La
Scalia,
G.
(2013).
An
oxygen
monitoring
and
control
system
inside
a
malaxation
machine
to
improve
extra
virgin
olive
oil
quality.
Biosystems
Engineering,
114,
1-8.
Chandrasekaran,
S.,
Ramanathan,
S.,
&
Basak,
T.
(2013).
Microwave
food
processing
-
a
review.
Food
Research
International,
52(1),
243-261.
Chedea,
V.
S.,
Braicu,
C.,
&
Socaciu,
C.
(2012).
Antioxidant/
prooxidant
activity
of
polyphenolic
grape
seed
extract.
Food
Chemistry,
121,
132-139.
Cheng,
W.
M.,
Raghavan,
G.
S.
V.,
Ngadi,
M.,
&
Wang,
N.
(2006).
Microwave
power
control
strategies
on
the
drying
process
I.
Development
and
evaluation
of
new
microwave
drying
system.
Journal
of
Food
Engineering,
76(2),
188-194.
Coronel,
P.,
Simunovic,
J.,
&
Sandeep,
K.
P.
(2003).
Temperature
profiles
within
milk
after
heating
in
a
continuous-flow
tubular
microwave
system
operating
at
915
MHz.
Journal
of
Food
Science,
68(6),
1976-1981.
Dogan-Halkman,
H.
B.,
Yiicel,
P.
K.,
&
Halkman,
A.
K.
(2014).
Non-
thermal
processingimicrowave.
In
C.
A.
Batt,
&
M.
L.
Tortorello
(Eds.),
Encyclopedia
of
food
microbiology
(pp.
962-965).
Oxford:
Academic
Press,
ISBN
9780123847331.
EC.
(1991).
Commission
regulation
(EEC)
no.
2568/91
of
11
July
1991
on
the
characteristics
of
olive
oil
and
olive-residue
oil
and
on
the
relevant
methods
of
analysis.
Official
Journal
of
the
European
Union,
L
248,
0001-0083.
Esposto,
S.,
Veneziani,
G.,
Taticchi,
A.,
Selvaggini,
R.,
Urbani,
S.,
Di
Maio,
I.,
et
al.
(2013).
Flash
thermal
conditioning
of
olive
pastes
during
the
olive
oil
mechanical
extraction
process:
impact
on
the
structural
modifications
of
pastes
and
oil
quality.
Journal
of
Agricultural
and
Food
Chemistry,
61,
4953-4960.
Gambacorta,
G.,
Faccia,
M.,
Trani,
A.,
Lamacchia,
C.,
&
Gomes,
T.
(2012).
Phenolic
composition
and
antioxidant
activity
of
Southern
Italian
monovarietal
virgin
olive
oils.
European
Journal
of
Lipid
Science
and
Technology,
114(8),
958-967.
Gambacorta,
G.,
Previtali,
M.
A.,
Pati,
S.,
Baiano,
A.,
&
La
Notte,
E.
(2006).
Characterization
of
the
phenolic
profiles
of
some
monovarietal
extra
virginolive
oils
of
Southern
Italy.
In
XXIII
international
conference
on
polyphenols
(pp.
393-394).
Winnipeg:
Manitoba.
Gentry,
T.
S.,
&
Roberts,
J.
S.
(2005).
Design
and
evaluation
of
a
continuous
flow
microwave
pasteurization
system
for
apple
cider.
LWT
-
Food
Science
and
Technology,
38(3),
227-238.
Gutierrez-Rosales,
F.,
Rios,
J.
J.,
&
Gomez-Rey,
M.
L.
(2003).
Main
polyphenols
in
the
bitter
taste
of
virgin
olive
oil.
Structural
confirmation
by
on-line
high-performance
liquid
chromatography
electrospray
ionization
mass
spectrometry.
Journal
of
Agricultural
and
Food
Chemistry,
51,
6021-6025.
Heredia,
A.,
Gullien,
R.,
Jimenez,
A.,
&
Bolarlos,
G.
F.
(1993).
Olive
fruit
glycosidases.
Factor
affecting
their
extraction.
Zeitschrift
far
Lebensmittel-Untersuchung
and
Forschung,
196,
147-151.
IOOC.
(2001).
Trade
standard
applying
to
olive
oil
and
olive
e
pomace
oil.
COI/T.15/NC
no.
2/rev.
10.
Kalua,
C.
M.,
Allen,
M.
S.,
Bedgood,
D.
R.,
Jr.,
Bishop,
A.
G.,
Prenzler,
P.
D.,
&
Robards,
K.
(2007).
Olive
oil
volatile
compounds,
flavour
development
and
quality:
a
critical
review.
Food
Chemistry,
100,
273-286.
Kone,
K.
Y.,
Druon,
C.,
Gnimpieba,
E.
Z.,
Delmotte,
M.,
Duquenoy,
A.,
&
Laguerre,
J.
C.
(2013).
Power
density
control
in
microwave
assisted
air
drying
to
improve
quality
of
food.
Journal
of
Food
Engineering,
119(4),
750-757.
Leone,
A.,
Romaniello,
R.,
&
Tamborrino,
A.
(2013).
Development
of
prototype
for
extra
virgin
olive
oil
storage,
with
online
control
system
of
the
nitrogen
injected.
Transaction
of
the
ASABE
-
American
Society
of
Agricultural
and
Biological
Engineers,
56(3),
1017-1024.
Leone,
A.,
Romaniello,
R.,
Zagaria,
R.,
&
Tamborrino,
A.
(2014).
Development
of
a
prototype
malaxer
to
investigate
the
influence
of
oxygen
on
extra-virgin
olive
oil
quality
and
yield,
to
define
a
new
design
of
machine.
Biosystems
Engineering,
118,
95-104.
Leone,
A.,
Tamborrino,
A.,
Romaniello,
R.,
Zagaria,
R.,
&
Sabella,
E.
(2014).
Specification
and
implementation
of
a
continuous
microwave-assisted
system
for
paste
malaxation
in
an
olive
oil
extraction
plant.
Biosystems
Engineering,
125,
24-35.
Loomis,
W.
D.
(1969).
Removal
of
phenolic
compounds
during
the
isolation
of
plant
enzymes.
Methods
in
Enzymology,
13(C),
555-563.
Loomis,
W.
D.,
&
Battaile,
J.
(1966).
Plant
phenolic
compounds
and
the
isolation
of
plant
enzymes.
Phytochemistry,
5(3),
423-438.
Mazzuca,
S.,
Spadafora,
A.,
&
Innocenti,
A.
M.
(2006).
Cell
and
tissue
localization
of13-glucosidase
during
the
ripening
of
olive
fruit
(Oleo
europaea)
by
in
situ
activity
assay.
Plant
Science,
171(6),
726-733.
Morales,
M.
T.,
Alonso,
M.
V.,
Rios,
J.
J.,
&
Aparicio,
R.
(1995).
Virgin
olive
oil
aroma:
relationship
between
volatile
compounds
and
sensory
attributes
by
chemometrics.
Journal
of
Agricultural
and
Food
Chemistry,
43(11),
2925-2931.
Pastore,
G.,
D'Aloise,
A.,
Lucchetti,
S.,
Maldini,
M.,
Moneta,
E.,
Peparaio,
M.,
et
al.
(2014).
Effect
of
oxygen
reduction
during
malaxation
on
the
quality
of
extra
virgin
olive
oil
(Cv.
Carboncella)
extracted
through
"two-phase"
and
"three-
phase"
centrifugal
decanters.
LINT
-
Food
Science
and
Technology.
http://dx.doi.org/10.1016/j.lwt.2014.04.053.
Pouliarekou,
E.,
Badeka,
A.,
Tasioula-Margari,
M.,
Kontakos,
S.,
Longobardi,
F.,
&
Kontominas,
M.
G.
(2011).
Characterization
and
classification
of
Western
Greek
olive
oils
according
to
cultivar
and
geographical
origin
based
on
volatile
compounds.
Journal
of
Chromatography
A,
1218(42),
7534-7542.
Reboredo-Rodriguez,
P.,
Gonzalez-Barreiro,
C.,
Cancho-
Grande,
B.,
&
Simal-Gandara,
J.
(2014).
Improvements
in
the
malaxation
process
to
enhance
the
aroma
quality
of
extra
virgin
olive
oils.
Food
Chemistry,
158,
534-545.
Reyes,
A.,
Ceran,
S.,
Zinliga,
R.,
&
Moyano,
P.
(2007).
A
comparative
study
of
microwave-assisted
air
drying
of
potato
slices.
Biosystems
Engineering,
98(3),
310-318.
Rodgers,
S.
(2007).
Innovation
in
food
service
technology
and
its
strategic
role.
International
Journal
of
Hospitality
Management,
26(4),
899-912.
Sanchez-Ortiz,
A.,
Perez,
A.
G.,
&
Sanz,
C.
(2013).
Synthesis
of
aroma
compounds
of
virgin
olive
oil:
significance
of
the
cleavage
of
polyunsaturated
fatty
acid
hydroperoxides
during
the
oil
extraction
process.
Food
Research
International,
54(2),
1972-1978.
Schiffmann,
R.
F.
(2010).
Industrial
microwave
heating
of
food:
principles
and
three
case
studies
of
its
commercialization.
In
C.
J.
Doona,
K.
Kustin,
&
F.
E.
Feeherry
(Eds.),
Case
studies
in
novel
food
processing
technologies
(pp.
407-426).
Woodhead
Publishing,
ISBN
9781845695514.
Servili,
M.,
Selvaggini,
R.,
Esposto,
S.,
Taticchi,
A.,
Montedoro,
G.
F.,
&
Morozzi,
G.
(2004).
Health
and
sensory
properties
of
virgin
olive
oil
hydrophilic
phenols:
agronomic
and
technological
102
BIOSYSTEMS
ENGINEERING
127 (2014) 92-102
aspects
of
production
that
affect
their
occurrence
in
the
oil.
Journal
of
Chromatography
A,
1054(1-2),
113-127.
Tamborrino,
A.
(2014).
Olive
paste
malaxation.
In
C.
Peri
(Ed.),
The
extra-virgin
olive
oil
handbook
(pp.
127-138).
UK:
John
Wiley
&
Sons,
Ltd.
Tamborrino,
A.,
Catalano,
P.,
&
Leone,
A.
(2014).
Using
an
in-line
rotating
torque
transducer
to
study
the
rheological
aspects
of
malaxed
olive
paste.
Journal
of
Food
Engineering,
126,
65-71.
Tamborrino,
A.,
Pati,
S.,
Romaniello,
R.,
Quinto,
M.,
Zagaria,
R.,
&
Leone,
A.
(2014).
Design
and
implementation
of
an
automatically
controlled
malaxer
pilot
plant
equipped
with
an
in-line
oxygen
injection
system
into
the
olive
paste.
Journal
of
Food
Engineering,
141,
1-12.
Taticchi,
A.,
Esposto,
S.,
Veneziani,
G.,
Urbani,
S.,
Selvaggini,
R.,
&
Servili,
M.
(2013).
The
influence
of
the
malaxation
temperature
on
the
activity
of
polyphenoloxidase
and
peroxidase
and
on
the
phenolic
composition
of
virgin
olive
oil.
Food
Chemistry,
136,
975-983.
Venkatesh,
M.
S.,
&
Raghavan,
G.
S.
V.
(2004).
An
overview
of
microwave
processing
and
dielectric
properties
of
agri-food
materials.
Biosystems
Engineering,
88(1),
1-18.
Vierhuis,
E.,
Servili,
M.,
Baldioli,
M.,
Schols,
H.
A.,
Voragen,
A.
G.
J.,
&
Montedoro,
G.
F.
(2001).
Effect
of
enzyme
treatment
during
the
mechanical
extraction
of
olive
oil
on
phenolic
compounds
and
polysaccharides.
Journal
of
Agricultural
and
Food
Chemistry,
49,
1218-1223.
Xanthakis,
E.,
Le-Bail,
A.,
&
Ramaswamy,
H.
(2014).
Development
of
an
innovative
microwave
assisted
food
freezing
process.
Innovative
Food
Science
&
Emerging
Technologies.
http://
dx.doi.org/10.1016/j.ifset.2014.04.003.