High-power ultrasound in olive paste pretreatment. Effect on process yield and virgin olive oil characteristics


Jiménez, A.; Beltrán, G.; Uceda, M.

Ultrasonics Sonochemistry 14(6): 725-731

2007


The effect of high-power ultrasound on olive paste, on laboratory thermo-mixing operations for virgin olive oil extraction, has been studied. Direct sonication by an ultrasound probe horn (105 W cm(-2) and 24 kHz) and indirect sonication with an ultrasound-cleaning bath (150 W and 25 kHz) were applied and their effects compared with the conventional thermal treatment. A quick-heating of olive paste, from ambient (12-20 degrees C) to optimal temperature conditions (28-30 degrees C), and an oil extractability improvement were observed when applying sonication. Better extractability was obtained by direct sonication for high moisture olives (>50%) whereas indirect sonication gave greater extractability for low moisture olive fruits (<50%). Optimal application of ultrasound was achieved with direct sonication for 4 min at the beginning of paste malaxation and with indirect sonication during the malaxation time. Effect of high-power ultrasound on oil quality parameters and nutritional and sensory characteristics were studied. Changes in quality parameters (free acidity value, peroxide value, K270 and K232) were not found, however significant effects on the levels of bitterness, polyphenols, tocopherols (vitamin E), chlorophyll and carotenoids were observed. Oils from sonicated pastes showed lower bitterness and higher content of tocopherols, chlorophylls and carotenoids. Related to sensory characteristics, off-flavour volatiles were not detected in oils from sonication treatments. Total peak areas of volatiles and the ratio hexanal/E-2-hexenal, as determined by SPME analysis, were lower than non-sonicated reference oils; sensory evaluation by panel test showed higher intensity of positive attributes and lesser of negative characteristics than those untreated.

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SONOCHEMISTRY
Ultrasonics
Sonochemistry
14
(2007)
725-731
-
I
ELSEVIER
www.elsevier.com/locate/ultsonch
High-power
ultrasound
in
olive
paste
pretreatment.
Effect
on
process
yield
and
virgin
olive
oil
characteristics
A.
Jimenez
*,
G.
Beltran,
M.
Uceda
Estacion
de
Olivicultura
y
Elaiotecnia,
'Yenta
del
Llano',
Institute
de
Investigacion
y
Formacion
Agraria
y
Pesquera,
Consejeria
de
Innovacion,
Ciencias
y
Empresas,
Junta
de
Andalucia,
Ctra.
Bailen-Motril,
Km.
18.4,
23620
Mengibar,
Jaen,
Spain
Received
17
June
2006;
received
in
revised
form
2
December
2006;
accepted
9
December
2006
Available
online
1
February
2007
Abstract
The
effect
of
high-power
ultrasound
on
olive
paste,
on
laboratory
thermo-mixing
operations
for
virgin
olive
oil
extraction,
has
been
studied.
Direct
sonication
by
an
ultrasound
probe
horn
(105
W
cm
-2
and
24
kHz)
and
indirect
sonication
with
an
ultrasound-cleaning
bath
(150
W
and
25
kHz)
were
applied
and
their
effects
compared
with
the
conventional
thermal
treatment.
A
quick-heating
of
olive
paste,
from
ambient
(12-20
°C)
to
optimal
temperature
conditions
(28-30
°C),
and
an
oil
extractability
improvement
were
observed
when
applying
sonication.
Better
extractability
was
obtained
by
direct
sonication
for
high
moisture
olives
(>50%)
whereas
indirect
sonication
gave
greater extractability
for
low
moisture
olive
fruits
(<50%).
Optimal
application
of
ultrasound
was
achieved
with
direct
sonication
for
4
min
at
the
beginning
of
paste
malaxation
and
with
indi-
rect
sonication
during
the
malaxation
time.
Effect
of
high-power
ultrasound
on
oil
quality
parameters
and
nutritional
and
sensory
characteristics
were
studied.
Changes
in
quality
parameters
(free
acidity
value,
peroxide
value,
K270
and
K232)
were
not
found,
however
significant
effects
on
the
levels
of
bitterness,
polyphenols,
tocopherols
(vitamin
E),
chlorophyll
and
carotenoids
were
observed.
Oils
from
sonicated
pastes
showed
lower
bitterness
and
higher
content
of
tocopherols,
chlorophylls
and
carotenoids.
Related
to
sensory
characteristics,
off-flavour
volatiles
were
not
detected
in
oils
from
sonication
treatments.
Total
peak
areas
of
volatiles
and
the
ratio
hexanal/E-2-hexenal,
as
determined
by
SPME
analysis,
were
lower
than
non-sonicated
reference
oils;
sensory
evaluation
by
panel
test
showed
higher
intensity
of
positive
attributes
and
lesser
of
negative
characteristics
than
those
untreated.
©
2007
Elsevier
B.V.
All
rights
reserved.
Keywords.•
High-power
ultrasound;
Virgin
olive
oil
elaboration;
Extractability;
Quality;
Nutritional;
Sensorial
1.
Introduction
Virgin
olive
oil
is
obtained
from
the
olive
fruits
(Olea
europaea
L.)
through
the
use
of
physical
procedures
[1].
This
process
begins
with
fruit
crushing
to
break
the
plant
tissues
in
order
to
liberate
the
oil
drops
contained
into
mesocarp
cells.
Then
olive
paste
is
kneaded
in
a
thermo-malaxer
to
group
the
oils
drops
into
a
continuous
oil
phase.
Solid-liquid
phase
separation,
by
pressure
or
Corresponding
author.
Tel.:
+34
953366367.
E-mail
address.•
(A.
Jime-
nez).
1350-4177/$
-
see
front
matter
©
2007
Elsevier
B.V.
All
rights
reserved.
doi:10.1016/j.ultsonch.2006.12.006
centrifugal
force,
is
carried
out
to
separate
olive
oil
from
the
water
and
solid
matter.
Finally,
to
eliminate
the
sus-
pended
particles
in
oil
a
decantation,
with
or
without
pre-
vious
centrifugation,
is
performed
before
storage.
Among
the
process
steps,
olive
paste
malaxation
is
one
of
the
most
important
in
the
virgin
olive
oil
extraction
process.
During
this
step
kneading
time
and
paste
temperature
are
regu-
lated
in
order
to
obtain
high
oil
quality
and
optimal
pro-
cess
yields
[2].
Basically,
the
virgin
olive
oil
extraction
process
is
a
set
of
basic
operations
of
heat
transference,
mass
transfer,
filtrations
and
sedimentations.
Their
aim
is
to
extract
a
fluid,
olive
oil,
from
a
semisolid
matrix
formed
by
particles
of
skin,
pulp
and
stones
[3].
6
I.
9
7
4
2
4
I.
3
4
4
4
5
4
7
726
A.
Jimenez
et
al.
1
Ultrasonics
Sonochemistry
14
(2007)
725-731
These
typical
operations
indicate
the
possibility
for
the
use
of
high-power
ultrasound
to
improve
the
oil
extraction
process.
Recently,
this
technology
has
been
investigated
and
applied
to
similar
industrial
operations,
particularly
in
the
food
industry.
There
are
several
studies
for
its
employment
in
opera-
tions
of
heat
transfer
[4,5],
in
mass
transport,
as
brining
of
cheeses
[6]
or
drying
of
food
products
[7,8];
in
operations
of
filtration
[9,10],
sedimentation
[11]
or
defoaming
[12];
in
extraction
of
oils
and
active
principles
using
solvents
[13-
15];
application
on
food
freezing
[16];
potential
application
in
food
processing
for
preservation
and
enzymatic
inhibi-
tion
[17,18].
The
aim
of
this
work
is
to
show
the
results
obtained
from
experiments
carried
out,
at
laboratory
scale,
to
ana-
lyse
the
potential
application
of
high-power
ultrasounds
on
the
malaxation
step
and
its
effect
on
oil
characteristics
and
process
yield.
The
effect
of
high-power
ultrasound
direct
application,
by
probe
horn,
and
indirect
application,
by
ultrasound
bath,
on
olive
pastes
from
'tree
picked'
fruits
at
two
harvesting
times
were
analysed.
2.
Materials
and
methods
2.1.
Oil
extraction
system
For
laboratory
scale
simulation
of
virgin
olive
oil
indus-
trial
process,
olives
were
subjected
to
ABENCOR
equip-
ment
[19].
This
equipment
consists
of
three
units:
a
hammer
mill,
a
thermo-malaxer
and
a
paste
centrifuge.
Approximately
1
kg
of
olive
fruits
was
ground
and
thor-
oughly
mixed,
700
g
of
the
milled
paste
were
placed
into
a
stainless-steel
mixing
container.
The
container
was
placed
in
the
thermo-malaxer
and
stirred
for
30
min
at
30
°C.
Then
olive
paste
was
centrifuged
for
2
min.
Oil
must
was
collected
in
a
500
ml
probe
allowing
10
min
for
phase
decantation,
the
volume
of
oil
was
measured.
Oils
extracted
were
filtered
for
chemical
analysis.
The
industry
performance
was
calculated
as
the
percent-
age
on
weight
of
the
olive
oil
extracted
(volume
measured
by
olive
oil
density,
0.915
g
m1
-1
)
from
the
olive
paste
weight
(on
a
fresh
matter
basis).
Extractability
index
has
been
defined
[20]
as
the
percent-
age
of
olive
oil
extracted
from
the
total
oil
content
of
the
fruit
(on
a
fresh
matter
basis).
2.2.
High
power
ultrasound
systems
For
the
application
of
high-power
ultrasound
the
Aben-
cor
thermo-malaxer
was
replaced
by
a
51
ultrasound
bath
(25
kHz,
Pacisa
SA,
Spain)
and
an
agitator
Eurostar
Power
control-visc
(IKA-Werke,
Germany)
that
stirred
at
similar
rotation
speed
to
the
Abencor
system
(60
rpm).
For
indirect
sonication
of
olive
paste,
the
stainless-steel
mixing
container
was
put
in
direct
contact
with
the
bottom
of
ultrasonic
bath
housing,
so
that
the
acoustic
vibrations
Fig.
1.
Schematic
disposition
of
the
experimental
thermo-mixer
for
(a)
indirect
sonication,
(b)
direct
sonication;
(1)
rod
agitator,
(2)
rod
stirrer,
(3)
mixer
container,
(4)
olive
paste,
(5)
water
bath,
(6)
ultrasonic
bath
generator,
(7)
piezoelectric
transducer,
(8)
ultrasonic
generator
UP
200s,
(9)
probe
horn.
of
the
piezoelectric
transducer,
at
25
kHz,
could
be
trans-
mitted
both
to
the
housing
and
to
the
olive
paste
container.
Direct
sonication
was
achieved
by
a
24
kHz
ultrasonic
generator
UP
200s
(Dr.
Hielscher
GMBH,
Germany),
fit-
ted
with
an
immersible
titanium
probe
horn
(14
mm
diam-
eter),
providing
105
W
cm
-2
output
power.
A
scheme
for
the
configuration
of
the
experimental
assembly
is
shown
in
Fig.
1.
2.3.
Olive
fruit
samples
Olive
fruit
samples
(0.
europaea
L.)
from
`Picual'
culti-
vars
were
collected
from
the
tree.
Sampling
was
carried
out
in
December
(first
week)
and
January
(last
week)
in
order
to
use
olive
pastes
with
different
characteristics.
Total
oil
content
and
moisture
content
were
determined
in
order
to
aid
their
characterization.
Moisture
(M)
(%
weight/weight)
was
determined
by
dry-
ing
of
milled
paste
at
105
°C
to
constant
weight.
Total
oil
content
(TOC)
was
determined
using
a
Mini-
spec
mq10
NMR
analyser
(Bruker
Analytik
GmbH,
Ger-
many)
and
expressed
as
percentage
on
fresh
matter
basis.
2.4.
Olive
oil
characterization
Determination
of
oil
quality
indexes:
acidity
value,
per-
oxide
value
and
UV
absorption
(K270
and
K232)
were
car-
ried
out
according
to
the
analytical
methods
described
in
Regulation
EEC/2568/91
of
the
European
Union
Commis-
sion
[1].
Phenolic
compounds
were
extracted
from
an
oil-in-hex-
ane
solution
with
methanol:
water
(60:40),
their
concentra-
tion
was
measured
using
Folin-Ciocalteau
reagent
and
colorimetric
measurement
at
725
nm
[21].
Results
were
expressed
as
mg
kg
-1
of
caffeic
acid.
A.
Jimenez
et
al.
1
Ultrasonics
Sonochemistry
14
(2007)
725-731
727
Bitter
index
was
determined
by
solid
phase
extraction
with
octadecyl
(C
18
)
packing
of
bitter
compounds.
Oil
dis-
solved
in
hexane
is
added
to
SPE
cartridge
and
bitter
com-
pounds
eluted
with
methanol:water
(1:1)
and
then,
absorbance
at
225
nm
was
measured
[22].
The
quantification
of
the
total
chlorophyll
and
caroten-
oid
pigments,
expressed
in
mg
kg
-1
,
were
evaluated
by
measuring
directly
the
adsorption
a
670
nm
and
450
nm,
respectively,
of
samples
diluted
in
cyclohexane
[23].
All
the
spectrophotometric
measurements
were
per-
formed
in
UV—Vis
diode
array
spectrophotometer
HP
8452
A
(Hewlett
Packard).
Tocopherols
content
[24]
were
determined
by
isocratic
HPLC
equipment
with
an
UV—Vis
detector
(Perkin
Elmer).
For
chromatography
separation
the
stationary
phase
was
Lichrosphere
Si60,
250
mm
x
4
mm
i.d.
and
5
gm
of
parti-
cle
size
(Merck
Ltd.).
Absorbance
was
recorded
at
295
nm
and
results
were
expressed
as
mg
kg
-1
of
total
tocopherols.
Volatile
compounds
were
analysed
by
HS-SPME
and
GC-FID.
Volatile
extraction
conditions
for
HS-SPME
were
3.0
g
of
oil
was
placed
in
a
6
ml
vial
sealed
with
an
aluminium
cap
and
Teflon
septum,
then
placed
in
water
bath
at
40
°C
under
magnetic
stirring.
After
5
min
for
sam-
ple
conditioning,
the
SPME
fibre
with
50/30
gm
DVB/Car-
boxen/PDMS
coating
(Supelco,
Bellefonte,
PA,
USA)
was
exposed
15
min
to
oil
headspace
and
then
immediately
transferred
to
the
GC
injection
port
for
desorption,
for
3
min
in
splitless
mode,
and
analysis.
GC-FID
volatile
analyses
have
been
performed
using
a
HP
6850
series
II
(Hewlett—Packard)
gas
chromatograph
equipped
with
a
flame
ionization
detector
(FID)
and
a
splitt/splittless
injec-
tor.
For
chromatographic
separation
a
HP5
column
30
m
long,
internal
diameter
0.25
mm
and
a
0.25
gm
film
thick-
ness
(Agilent
Technologies,
Ins.
USA)
was
used.
The
initial
oven
temperature
was
maintained
at
40
°C
for
5
min,
and
then
increased
at
4
°C/min
up
to
220
°C,
the
final
temper-
ature
was
held
for
10
min.
The
injector
temperature
was
260
°C
and
the
detector
280
°C.
The
injector
was
equipped
with
a
0.75
mm
ID
glass
liner
(Supelco
Inc.,
Bellefonte,
PA).
The
carrier
gas
was
nitrogen
at
15
psi
on
column
head.
Volatile
compounds
were
identified
by
comparison
of
their
retention
times
with
those
of
pure
standard
sub-
stances.
FID
peak
area
normalization
was
used
for
quantification.
Sensory
analysis
was
performed
by
panel
test
procedure
according
to
EU
Regulation
1898/2003
[25].
The
oil
sam-
ples
were
evaluated
by
trained
and
selected
panelists.
Pan-
elists
evaluated
samples
by
flavour
and
off-flavours
descriptors,
in
a
profile
sheet
based
on
a
continuous
scale
0-10,
and
then
median
value
for
each
attribute
was
given.
2.5.
Statistical
analysis
To
analyse
the
ultrasound
effect
on
olive
paste
and
oils,
analysis
of
variance,
from
Statistix
7.0
software
(Analytical
Software,
USA),
was
applied
to
determine
the
significance
for
extractability
index
and
analytical
chemical
data.
A
Tukey's
test
for
means,
at
p
<
0.05,
was
applied.
3.
Results
and
discussion
3.1.
Effect
of
ultrasound
treatment
on
olive
paste
When
high-power
ultrasound
is
applied
to
a
solid—liquid
sample,
heating
and
other
phenomena
due
to
continued
fast
compressions
and
expansions
caused
by
the
acoustic
waves
are
observed.
One
such
phenomenon
is
the
so-called
`sponge
effect'
[26],
which
produces
liquid
movement
through
microchannels
originated
by
the
solid
parts.
This
behaviour
is
similar
to
that
occurring
during
olive
oil
extraction,
considered
as
a
solid—liquid
mass
transference
process
where
the
oil
crosses
the
solid
matrix
as
in
a
filtra-
tion
process
[3].
Fig.
2
shows
the
variation
in
olive
paste
temperature
during
its
malaxation
for
30
min
applying
three
kneading
treatments:
indirect
sonication
(IUSO)
with
the
ultrasound
bath,
direct
sonication
(DUSO)
with
the
probe
horn
and
reference
without
sonication
(TEST)
where
the
paste
heat-
ing
is
performed
in
thermo-malaxer
at
30
°C.
As
can
be
observed,
IUSO
and
DUSO
paste
treatments
both
pro-
duced
a
quick-heating
of
olive
paste.
The
heating
rate
was
higher
than
those
by
the
traditional
heat
transfer
trans-
mission
(TEST),
showing
higher
rate
DUSO
than
IUSO.
Sonic
energy
of
ultrasounds
is
transformed
into
calorific
energy
that
is
distributed
to
the
paste
by
kneading.
IUSO
treatment
includes
maintained
sonication
during
malaxation
time,
under
these
conditions,
the
optimal
olive
paste
kneading
temperature
(29
±
1
°C)
is
achieved
in
less
than
10
or
15
min,
while
the
TEST
treatment
needs
at
least
20
min
to
reach
it.
For
DUSO
treatment,
sonication
time
and
frequency
achieve
great
importance
since
a
continuous
application
38
-
36
-
34
-
g
32
-
30-
E
28
-
g
26
-
a
24
-
0
22
-
20
-
18
0
5
10
15
20
25
30
Olive
paste
malaxation
time
(min)
Fig.
2.
Effect
of
power
ultrasound
treatment
on
olive
paste
temperature,
during
the
malaxation.
•,
4
min
cyclic
direct
application
by
horn
during
malaxation;
4
min
direct
application
by
horn
from
malaxation
start;
0,
indirect
ultrasound
treatment
by
bath
during
malaxation;
A,
test
without
ultrasound
treatment.
728
A.
Jimenez
et
al.
1
Ultrasonics
Sonochemistry
14
(2007)
725-731
during
malaxation
produced
high
temperature
of
paste,
above
38-40
°C
in
less
than
10
min,
that
can
affect
nega-
tively
the
oil
quality.
If
sonication
is
applied,
during
malax-
ation,
in
on—off
periods
of
4
min,
quick-heating
to
30
°C
occurs
and
then
a
gradual
heating
of
the
paste
until
the
end
of
malaxation
achieving
a
final
36
°C.
The
optimal
application
might
be
a
unique
initial
4
min
sonication,
when
mixing
had
started,
that
produces
a
quick-heating
to
30
°C
reached
in
less
than
8
min,
keeping
the
paste
tem-
perature
at
30
°C
by
heat
transfer from
water
bath
until
the
end
of
malaxation.
In
both
cases,
for
the
experimental
conditions,
the
first
consequence
of
the
quick-heating
observed
was
an
increase
of
time
that
olive
paste
remains
at
optimal
temperature,
20
or
15
min
for
DUSO
and
IUSO
respectively,
that
those
heated
by
traditional
heat
transfer
(less
than
10
min).
In
the
olive
oil
extraction
process,
it
is
known
that
to
extract
a
greater
amount
of
oil
a
longer
kneading
time
at
optimal
temperature
is
needed.
However,
both
high
tem-
perature
and
long
time
of
malaxation
damages
the
oil
qual-
ity,
as
oxidation
processes
are
enhanced
and
losses
in
sensory
characteristics
take
place.
At
industry
scale,
extra
malaxation
time
is
required
to
reach
the
optimal
paste
temperature,
usually
around
15-
20
min
for
30
°C.
In
the
malaxer,
olive
paste
heating
is
car-
ried
out
by
heat
transfer
from
surface
of
heat
chamber
toward
the
paste
that
is
produced
slowly
due
to
the
low
heat
capacity
of
olive
paste
and
the
use
of
non-elevate
tem-
perature
to
avoid
an
overheat
because
of
its
thermal
inertia.
In
Table
1,
the
effect
of
the
paste
treatments
on
yield
and
oil
extractability
are
shown.
It
can
be
seen
that
ultrasound
application
on
olive
paste
can
produce
a
significant
improvement
(p
<
0.05)
on
oil
extractability.
This
behav-
iour
looks
different
according
to
the
olive
characteristics.
Mulet
et
al.
[26]
indicated
different
effects
of
ultrasounds
on
mass
transfer
depending
to
the
characteristics
of
the
products.
In
olives
with
high
moisture
content,
as
first
har-
vesting
date
(63.6%),
DUSO
was
the
best
treatment
with
significant
differences
in
extractability
(45.9%)
with
TEST
(42.5%),
while
IUSO
had
non-significant
extractability
dif-
ferences.
When
olive
fruits
were
overripe
and
contained
low
moisture,
e.g.
at
the
second
harvesting
(46.6%),
IUSO
was
the
best
treatment
with
an
extractability
of
73.2%,
sig-
nificatively
different
to
TEST
(72.0%),
but
DUSO
had
the
lowest
extractability
(70.7%),
it
might
be
originated
by
a
poor
contact
probe-paste
for
these
low
moisture
fruits.
3.2.
Effect
of
ultrasound
treatment
on
olive
oil
When
high-power
ultrasound
is
applied
to
olive
pastes,
their
effect
on
chemical,
nutritional
and
sensorial
character-
istics
of
oil
obtained
should
be
considered.
In
Table
2
the
chemical
quality
parameters
of
oils
are
presented,
according
to
UE
Regulation,
from
the
different
paste
treatments.
All
the
oils
obtained
were
classified
into
`extra
virgin'
category.
For
the
first
harvesting
date
non-
significant
differences
were
found
between
treatments
for
acidity
value,
peroxide
value
and
UV
absorbance
at
270
nm;
only
values
for
K232
in
IUSO
treatment
were
found
significatively
different
to
DUSO
and
TEST,
with
values
of
1.465
±
0.064,
1.570
±
0.057
and
1.590
±
0.014,
respectively.
In
general,
for
quality
parameters
IUSO
oils
showed
the
lowest
values.
In
second
harvesting
date,
IUSO
oils
showed
again
the
lowest
values
for
all
the
quality
parameters,
with
significant
differences
in
peroxide
value
and
K232.
In
general,
no
oxi-
dation
or
hydrolysis
effects
were
observed
in
oils
when
ultrasounds
were
applied.
In
Table
2,
the
effect
of
olive
paste
treatments
on
some
important
nutritional
parameters
of
the
olive
oil
are
shown.
Significant
differences
between
mean
values
for
TEST
and
ultrasound
treatments
were
found
for
both
har-
vesting
dates.
For
total
polyphenol
content,
the
lower
values
were
obtained
from
olive
paste
treated
with
ultrasound:
DUSO
oils
from
first
harvesting
date
and
IUSO
oils
from
second
harvesting
date,
with
349
±
30
and
273
±
2
ppm,
respec-
tively.
These
compounds
are
important
components
in
Table
1
Effect
of
ultrasound
treatment
on
process
yield
and
oil
extractability
Treatment
Yield
efficiency
(%)
Oil
extractability
(%)*
Olives
composition
Fat
(%)
Moisture
(%)
First
harvesting
date
TEST
7.23
±
0.12
42.5
±
0.71
b
17.1
63.6
IUSO
7.80
±
0.53
45.9
±
0.71'
DUSO
7.63
±
0.34
44.9
±
1.98
th
Second
harvesting
date
TEST
15.85
±
0.07
72.0
±
0.28
th
22.1
46.6
DUSO
15.55
±
0.21
70.7
±
0.92
b
IUSO
16.1
±
0.14
73.2
±
0.64
a
TEST,
olive
past
without
treatment;
DUSO,
direct
ultrasound
application
by
probe
horn;
IUSO,
indirect
ultrasound
application
by
bath.
Mean
values
±
SD
(n
=
2).
Different
letters
by
harvesting
date,
indicate
significative
differences
at
p
<
0.05.
A.
Jimenez
et
al.
1
Ultrasonics
Sonochemistry
14
(2007)
725-731
729
Table
2
Effect
of
ultrasound
treatment
on
quality
and
nutritional
parameters
of
virgin
olive
oil
First
harvesting
date
Second
harvesting
date
test
TEST
DUSO
IUSO
TEST
DUSO
IUSO
Quality
parameters
Acidity
value
(%
oleic
fatty
acid)
0.17
±
0.02a
0.15
±
0.00a
0.15
±
0.00a
0.15
±
0.00a
0.17
±
0.02a
0.14
±
0.01a
Peroxide
value
(meq
0
2
/kg)
4.84
±
0.14'
5.47
±
1.09'
4.56
±
0.17'
7.93
±
1.01'
7.19
±
0.25
a
5.61
±
0.00
b
K270
0.115
±
0.007a
0.120
±
0.014'
0.105
±
0.007'
0.105
±
0.007'
0.120
±
0.028'
0.090
±
0.014'
K232
1.590
±
0.014'
1.570
±
0.057
th
1.465
±
0.064
b
1.435
±
omor
1.440
±
0.028'
1.355
±
0.007
b
Nutritional
parameters
Total
polyphenols
(ppm)
419
±
37'
349
±
8
b
352
±
30
b
293
±
0'
288
±
3
b
273
±
2C
Total
tocopherols
(ppm)
245
±
O
a
225
±
9
b
234
±
la
b
232
±
6'
245
±
5
a
226±
13'
Carotenoids
(ppm)
4.0
±
0.1
b
4.7
±
0.1a
4.8
±
0.1"
7.4
±
0.1
b
8.6
±
0.1"
8.4
±
0.3"
Chlorophylls
(ppm)
2.6
±
0.0
b
4.0
±
0.2a
4.4
±
0.2a
5.5
±
0.1
b
8.1
±
0.6"
7.4
±
0.5
a
TEST,
olive
past
without
treatment.
DUSO,
direct
ultrasound
application
by
probe
horn.
IUSO,
indirect
ultrasound
application
by
bath.
Mean
values
±
SD
(n
=
2).
*
For
each
parameter,
different
letters
by
harvesting
date
indicate
significant
differences
at
p
<
0.05.
Table
3
Effect
of
ultrasound
treatment
on
sensorial
characteristics
of
virgin
olive
oil
Treatment
Bitterness
(K225)
Hexanal/E-2-hexenal
(ratio)
Total
volatile
area
(10
4
AV)
1st
harvesting
date
TEST
0.28
±
0.00'
2.10
99.64
Organoleptic
panel
test
evaluation
DUSO
0.24
±
0.01
b
1.76
99.02
Positive
characteristics
Off-flavours
IUSO
0.25
±
0.01
b
1.29
95.18
Fruit
Bitterness
Green
Pungent
Wine
2nd
harvesting
date
TEST
0.20
±
0.00'
1.75
95.28
4.3
4.0
3.9
4.9
1.5
DUSO
0.21
±
0.00'
1.50
93.45
4.9
3.1
4.3
5.1
0.8
IUSO
0.19
±
0.00
b
1.35
94.14
5.3
2.4
5.3
5.3
0.0
TEST,
olive
past
without
treatment;
DUSO,
direct
ultrasound
application
by
probe
horn;
IUSO,
indirect
ultrasound
application
by
bath.
Mean
values
±
SD
(n
=
2).
olive
oil
due
both
to
their
antioxidant
effect
and
organolep-
tic
characteristics
since
they
have
been
related
to
pungency
and
bitterness.
High
polyphenol
content
give
oils
with
high
stability,
but
very
pungent
and
bitter
which
may
be
rejected
by
some
consumers.
In
total
tocopherols,
only
significant
differences
were
found
at
first
harvesting
date
between
DUSO
and
TEST,
showing
DUSO
the
lowest
value
(225
±
9
ppm).
At
second
harvesting
date
no
differences
were
noticed
between
paste
treatments,
with
higher
value
for
DUSO
treatment
(245
±
5
ppm)
and
lower
for
IUSO
(226
±
13
ppm).
Ultrasound
treatments
gave
oils
with
significant
higher
contents
in
carotenoids
and
chlorophylls
that
those
untreated.
A
similar
behaviour
was
observed
in
both
har-
vesting
dates,
since
no
differences
between
DUSO
and
IUSO
were
found.
Therefore
oils
from
ultrasound
treat-
ments
were
more
green
and
had
greater
provitamin
A
con-
tent
than
those
obtained
without
sonication.
With
regard
to
the
sensorial
characteristics,
these
were
analysed
first
chemically
for
both
harvesting
dates
measur-
ing
bitterness
by
K225
and
volatiles
by
SPME-GC-FID;
second
by
panel
test
on
oils
obtained
at
second
harvesting
date.
Results
are
presented
in
Table
3.
At
the
first
harvesting
date
oils
were
more
bitter
than
those
from
the
second
one.
Bitterness
index
(K225)
is
related
with
total
polyphenol
content
Thus,
oils
obtained
from
sonicated
olive
paste
were
significatively
less
bitter
than
those
untreated;
the
lower
values
are
shown
by
DUSO
oils
(0.24
±
0.01)
at
first
harvesting
date,
and
IUSO
(0.19
±
0.00)
at
the
last
one.
The
hexanal/E-2-hexenal
ratio
was
found
to
be
lower
in
oils
from
olive
paste
ultrasound
treated
at
both
harvesting
dates;
these
volatiles
are
related
to
oxidation
of
linolenic
and
linoleic
fatty
acids,
E-2-hexenal
from
lipoxygenase
pathway
and
hexanal
from
direct
autoxidation,
respec-
tively.
They
are
present
at
different
concentrations
in
virgin
olive
oils.
High
quality
oils
show
higher
E-2-hexenal
levels
than
hexanal.
When
oil
oxidation
is
induced
a
fast
increase
of
hexanal
and
decrease
of
E-2-hexenal
levels
takes
place,
and
then
off-flavour
'rancid'
appears.
From
experimental
samples,
the
hexanal/E-2-hexenal
ratio
became
smaller
in
oils
from
sonicated
paste,
this
indicates
that
oil
oxidation
did
not
occur
being
confirmed
because
no
increase
in
total
area
of
volatile
and
another
compounds
were
observed,
compared
with
TEST
oils
(Fig.
3).
With
regard
to
the
panel
test
evaluation
at
second
harvesting
date,
the
overripe
fruits
gave
a
slightly
`winey'
off-flavour
in
TEST
oils,
appearing
at
lower
intensity
in
oils
from
DUSO
treatment
and
was
not
detected
in
IUSO
oils.
730
A.
Jimenez
et
al.
1
Ultrasonics
Sonochemistry
14
(2007)
725-731
a
r
-
mol
Ui
I
AI
co
L
u
,
FID1
A,
Of
USO,,OSAVI.1.)
CJ
C;
Fl
D1
A,
of
118035400.D
C
rA)
-0•••••1
5
10
15
26
Fig.
3.
SPME-GC-FID
chromatographic
profiles
of
volatiles
of
oils
obtained
from
olive
paste
treated
with
direct
sonication
(DUSO),
(a);
with
indirect
sonication
(IUSO),
(b);
without
ultrasound
treatment
(TEST),
(c).
Standard
hexanal,
t
r
=
2.75
min;
standard
E-2-hexenal,
t
r
=
4.15
min.
Oils
from
ultrasound
treatments
were
more
fruity,
green,
pungent
and
less
bitter
than
those
from
TEST.
IUSO
oils
showed
the
lower
bitterness,
as
observed
for
K225
value;
other
positive
attributes
were
higher
than
those
obtained
in
DUSO
oils.
Briefly,
for
the
experimental
conditions
tested,
high-
power
ultrasound
application
on
olive
paste
has
shown
a
positive
effect
on
malaxation
step.
It
provides
a
quick-heat-
ing
of
olive
paste,
improvement
in
process
extractability
and
modulation
of
olive
oil
composition
without
alter-
ation.
Instrumentation
and
conditions
on
ultrasound
appli-
cation
are
needed
to
be
optimized
according
to
olive
fruit
characteristics
and
the
sensory
and
nutritional
properties
of
oil
required.
All
suggest
the
viability
of
application
of
this
technology
in
malaxation
step
of
olive
oil
process;
translation
to
industrial
plant
will
be
the
following
step
to
be
carried
out.
Acknowledgements
To
Pedro
Quesada
for
his
work
in
laboratory.
This
pa-
per
has
been
supported
by
FAGA-FEOGA:
Program
for
the
improvement
in
the
olive
oil
production
quality
Project
CA001-019:
'Effect
of
kneading
time
and
temperature
on
different
compounds
with
nutritional
and
sensorial
interest
of
virgin
olive
oil'
and
FEDER-INIA
RTA
04-128
'Re-
search
and
application
of
new
technologies
in
the
on-line
characterization
of
the
virgin
olive
oil
during
its
production
on
oil-mill'.
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