Specification of a new de-stoner machine: evaluation of machining effects on olive paste's rheology and olive oil yield and quality


Romaniello, R.; Leone, A.; Tamborrino, A.

Journal of the Science of Food and Agriculture 97(1): 115-121

2016


An industrial prototype of a partial de-stoner machine was specified, built and implemented in an industrial olive oil extraction plant. The partial de-stoner machine was compared to the traditional mechanical crusher to assess its quantitative and qualitative performance. The extraction efficiency of the olive oil extraction plant, olive oil quality, sensory evaluation and rheological aspects were investigated. The results indicate that by using the partial de-stoner machine the extraction plant did not show statistical differences with respect to the traditional mechanical crushing. Moreover, the partial de-stoner machine allowed recovery of 60% of olive pits and the oils obtained were characterised by more marked green fruitiness, flavour and aroma than the oils produced using the traditional processing systems. The partial de-stoner machine removes the limitations of the traditional total de-stoner machine, opening new frontiers for the recovery of pits to be used as biomass. Moreover, the partial de-stoner machine permitted a significant reduction in the viscosity of the olive paste. © 2016 Society of Chemical Industry.

Research
Article
SCI
Received:
27
June
2015
Revised:
13
February
2016
Accepted
article
published:
1
March
2016
Published
online
in
Wiley
Online
Library:
(wileyonlinelibrary.com
)
DOI
10.1002/jsfa.7694
Specification
of
a
new
de-stoner
machine:
evaluation
of
machining
effects
on
olive
paste's
rheology
and
olive
oil
yield
and
quality
Roberto
Romaniello,a
Alessandro
Leonea
and
Antonia
Tamborrinob*
Abstract
BACKGROUND:An
industrial
prototype
of
a
partial
de-stoner
machine
was
specified,
built
and
implemented
in
an
industrial
olive
oil
extraction
plant.
The
partial
de-stoner
machine
was
compared
to
the
traditional
mechanical
crusher
to
assess
its
quantitative
and
qualitative
performance.
The
extraction
efficiency
of
the
olive
oil
extraction
plant,
olive
oil
quality,
sensory
evaluation
and
rheological
aspects
were
investigated.
RESULTS:
The
results
indicate
that
by
using
the
partial
de-stoner
machine
the
extraction
plant
did
not
show
statistical
differences
with
respect
to
the
traditional
mechanical
crushing.
Moreover,
the
partial
de-stoner
machine
allowed
recovery
of
60%
of
olive
pits
and
the
oils
obtained
were
characterised
by
more
marked
green
fruitiness,
flavour
and
aroma
than
the
oils
produced
using
the
traditional
processing
systems.
CONCLUSION:
The
partial
de-stoner
machine
removes
the
limitations
of
the
traditional
total
de-stoner
machine,
opening
new
frontiers
for
the
recovery
of
pits
to
be
used
as
biomass.
Moreover,
the
partial
de-stoner
machine
permitted
a
significant
reduction
in
the
viscosity
of
the
olive
paste.
2016
Society
of
Chemical
Industry
Keywords:
de-stoner
machine;
rheology;
olive
paste;
olive
oil
INTRODUCTION
Extraction
operations
are
the
most
important
factors
affecting
quality
and
bioactivity
level
of
virgin
olive
oil
(V00).
All
steps
of
the
olive
oil
extraction
influence
its
quality
and
yield.
This
aware-
ness
has
led
in
the
last
30
years
towards
a
continuous
improve-
ment
of
plants
and
olive
oil
process,
which
had
as
the
goal
the
high
quality
of
the
extra
virgin
olive
oil,
high
extraction
efficiency
of
the
plants
and
safer
processes
and
equipment.
Technological
innovations
to
produce
high
quality
and
to
improve
the
extraction
yield
were
implemented
according
to
the
literature.'"
Regard-
ing
the
milling
operation,
the
traditional
stone
mill
was
replaced
by
a
mechanical
crusher,
mainly
a
disc
and
hammer
crusher
and
the
effect
of
the
different
crushing
system
on
the
quality,
yield
and
degree
of
stone
and
oil
drops
fragmentation
was
studied.
18-21
In
early
2000,
a
new
concept
of
milling
operation
was
devel-
oped:
the
olive
pulp
processing
excluded
the
kernel,
that
is,
the
woody
portion
of
the
fruit.
22
The
proposed
technology
is
a
useful
alternative
operation
for
olive
oil
production,
which
involves
olive
de-stoning
before
oil
extraction
using
a
de-stoner
machine.
The
de-stoner
machine
removes
the
entire
stone
from
olives
before
their
malaxation.
According
to
some
authors
a
problem
occur-
ring
in
olive
oil
extraction
would
be
the
high
level
of
endogenous
oxido-reductase
enzymes,
in
particular
peroxidase,
present
in
the
woody
stone
kernel,
which
could
enhance
the
risk
of
oil
oxida-
tion.
Thus,
removal
of
stones
before
malaxation
partially
inhibits
peroxidase
activity
in
olive
paste
and
consequently
a
reduction
of
the
enzymatic
degradation
of
the
hydrophilic
phenols
can
occur.
The
de-stoning
improves
the
phenol
concentration
in
oil
and
con-
sequently
its
oxidative
stability,
as
well
as
improves
the
sensorial
properties
and
the
volatiles
compounds;
23-26
a
negative
effect
on
pigment
transfer
(both
chlorophylls
and
carotenoids)
from
fruits
to
oil
was
observed
by
some
authors.
22,28
Using
the
de-stoner
machine
avoids
the
mechanical
and
thermal
stress
of
olive
paste
during
the
milling
operation,
increases
the
amount
of
olives
pro-
cessed
per
hour
(the
increment
corresponds
to
the
percentage
of
stones
with
respect
to
the
entire
olive
fruit),
and
changes
the
rhe-
ological
characteristics
of
olive
paste
as
a
result
of
its
increased
percentage
of
moisture.
23
In
a
previous
work
we
reported
that
the
use
of
this
technology
leads
to
a
decrease
of
yield
and
decanter
extraction
efficiency.
22
The
first
reason
for
this
weakness
is
the
absence
of
stone
frag-
ments,
which
makes
the
malaxation
less
efficient.
In
fact,
the
angular
and
sharp
stone
fragments
contribute
to
breaking
the
residual
uncrushed
olive
pulp
cells
during
malaxation
that
other-
wise
would
be
lost
in
the
waste
water
or
husk.
The
second
reason
*
Correspondence
to:
A
Tamborrino,
Department
of
Agricultural
and
Environ-
mental
Science,
University
of
Bari
Aldo
Moro,
Via
Amendola
165/A,
70126
Bart
Italy.
E-mail:
antonia.tamborrino@uniba.it
a
Department
of
the
Science
of
Agriculture,
Food
and
Environment
University
of
Foggia,
Via
Napoli
25,
71122
Foggia,
Italy
b
Department
of
Agricultural
and
Environmental
Science,
University
of
Bari
Aldo
Moro,
Via
Amendola
165/A,
70126
Bart
Italy
J
Sci
Food
Agric
(2016)
www.soci.org
©
2016
Society
of
Chemical
Industry
Waste
al
water
(b)
Leave
Figure
1.
Layout
of
industrial
olive
oil
extraction
plant
and
process:
(A)
loading
hopper;
(B)
defoliator;
(C)
washing
machine;
(D)
hopper;
(T)
three-way
valve;
(E)
partial
de-stoner
machine;
(F)
hammer
crusher;
(G)
malaxer
machines;
(H)
solid/liquid
horizontal
centrifugal
decanter;
(L)
liquid-liquid
vertical
centrifuges;
(P)
Cavity
Pump.
processed
olives'
weight.
Figure
1
shows
the
layout
of
industrial
olive
oil
extraction
plant
and
process.
Specification
of
partial
de-stoner
machine
The
project
parameters
used
for
the
partial
de-stoner
develop-
ment
are
listed
below:
Stainless
steel
AISI-316
used
for
all
parts
in
contact
with
olive
paste
Variable
paste
flow
rate
until
6000
kg
h
-1
[olives]
Modulation
of
discharged
pits'
quantity,
from
0
(traditional
configuration)
to
100%
(total
de-stoning
configuration)
Olives
irab
et
Washed
olives
EL
NOUOME•11111Mi
.1
(g)
'V
171,17
,
71174
P
Water
Waste
water
I
1
Oil
Husk
1
Wa
i
er
www.soci.org
R
Romaniello,
A
Leone,
A
Tamborrino
is
that
the
absence
of
the
stone
fragments
reduces
the
draining
effect
of
the
liquid
phase
in
the
decanter
during
the
centrifugation,
which
consequently
reduces
its
efficiency
and
the
extraction
yield.
These
negative
aspects
related
to
the
lack
of
these
actions
of
the
stone
fragments
in
olive
pastes
could
partly
be
solved
by
increas-
ing
the
malaxation
time
and
improving
the
decanter
setting,
i.e.
reducing
the
mass
flow
rate.
Despite
the
positive
aspects,
also
linked
to
the
stones'
recovery,
these
negative
aspects
have,
however,
limited
the
spread
of
the
total
de-stoner
machine,
which
achieves
a
total
removal
of
the
olive
stones.
In
recent
years,
however,
the
growing
market
demand
for
olive
stone
fragments
(OSFs)
to
be
used
for
energy
purposes,
has
led
an
Italian
machinery
company,
with
the
author's
support,
to
design
and
build
a
new
de-stoner
machine:
the
partial
de-stoner
machine
(PDM).
The
partial
de-stoner
machine
involved
in
this
research
does
not
remove
the
stone
in
full,
in
contrast
to
the
total
de-stoner
machine
used
in
all
the
previous
studies,
but
removes
only
a
variable
percentage
of
stone
fragments.
This
is
achieved
by
means
of
a
mechanical
solution
that
allows
crushing
of
the
olives
and
subsequently
the
separation
of
a
desired
quantity
of
fragmented
stones.
Thus,
if
an
amount
of
about
50%
of
OSF
is
removed,
the
remaining
50%
of
stone
fragments
with
all
the
pulp
continued
in
the
process.
Therefore,
the
olive
oil
obtained
is
not
classified
as
'de-stoned
oil'
but
'partial
de-stoned
oil'.
As
with
all
new
ideas,
the
concept
of
innovation
requires
exten-
sive
investigation,
testing
and
development.
This
paper
analyses
a
new
de-stoner
machine
as
a
case
study
of
the
technological
changes
associated
with
the
proposal
innovation.
The
aim
of
this
study
was
to
investigate
the
machining
effects
of
the
innovative
partial
de-stoned
machine
on
rheological
aspects
of
the
olive
paste,
on
olive
oil
quality
and
on
the
plant
efficiency
by
processing
Coratina
(Olea
europaea
L.)
olives.
The
experiments
were
carried
out
comparing
the
partial
de
stoner
machine
with
a
hammer
crusher
machine
(Control)
in
an
industrial
plant.
The
paper
includes
research
design,
procedures,
quantitative
and
qualitative
analyses
for
furthering
understanding
of
the
role
played
by
and
consequences
of
this
new
de-stoner
machine
included
in
the
olive
oil
extraction
plants.
MATERIALS
AND
METHODS
Olives
and
experimental
plant
Coratina
olives
were
mechanical
harvested
near
Foggia,
Puglia
region,
south
Italy,
during
the
crop
season
2014-2015.
The
olive
maturity
index
(MI)
was
determined
according
to
the
method
proposed
by
the
International
Olive
Oil
Council,
29
based
on
the
skin
colour
evaluation.
The
MI
was
1.4.
Olives
was
milled
in
an
industrial
extraction
plant
constituted
by
a
leaf
removing
machine,
washing
machine,
hammer
crusher
(mod.
Hammer
Mill
Crusher;
Alfa
Laval
Corporate
AB,
Lund,
Sweden)
with
grid
hole
of
7
mm,
or
an
innovative
PDM
(mod.
Moliden;
Pietro
Leone
e
Figli
s.n.c.,
Foggia,
Italy),
group
of
six
open
malaxer,
a
3-phase
decanter
(mod.
NX
X32;
Alfa
Laval
Corporate
AB)
and
two
vertical
plate
centrifuges
(mod.
UVPX
507;
Alfa
Laval
Corporate
AB).
Each
trial
was
replicated
three
times
using
a
homogenous
olive
batch
divided
in
three
sub-batches
of
700
kg
each.
Process
parameters
were:
(1)
malaxation
time
=
40
min;
(2)
malaxation
temperature
=
27
°C;
(3)
plant
mass
flow
rate=
3000
kg
h
-l
;
(4)
water
added
to
the
decanter
=
15%
of
the
©
2016
Society
of
Chemical
Industry
J
Sci
Food
Agric
(2016)
A
new
de-stoner
machine
for
efficient
recovery
of
olive
stones
www.soci.org
SCI
B
Figure
2.
Partial
de-stoner
machine:
(A)
chassis;
(B)
mechanical
crusher;
(C)
de-stoner
section;
(D)
cochlea
conveyor
for
pits
extraction;
(E)
malaxing
section;
(F)
olive
feeding
section.
Pool
for
temporary
containment
of
partial
de-stoned
olive
paste.
Figure
2
shows
the
PDM.
The
chassis
(A)
is
constructed
in
welded
stainless-steel
sections.
A
mechanical
crusher
(B)
constitutes
the
crushing
section.
A
horizontal
bowl
made
in
perforated
plate,
having
inspection
panels
on
its
top,
constitutes
the
de-stoner
section
(C).
The
de-stoning
shaft
is
mounted
in
the
inner
bowl
through
specific
rolls,
and
moved
by
an
electric
motor
through
mechanical
transmission.
The
de-stoner
is
included
in
a
couple
of
safety
carters.
A
cochlea
conveyor
moved
by
a
motor-reducer,
allows
extraction
of
the
pits
from
the
de-stoner
section
(D).
A
hopper
is
placed
between
the
crushing
and
de-stoning
sections
in
order
to
recover
the
olive
paste.
The
paste
is
transferred
in
the
hopper
by
a
cochlea,
moved
by
a
motor-reducer.
The
malaxing
basin
(E)
is
equipped
by
a
shaft,
moved
by
a
motor-reducer,
which
has
the
scope
to
temporarily
contain
the
partially
de-stoned
olive
paste,
until
it
is
sent
to
the
malaxer
machines.
The
olives
feed
in
continuous
mode,
and
pass
into
the
crushing
machine
through
a
cochlea
from
point
F.
The
crusher
lightly
breaks
the
olive
pulp
and
stones.
Then,
the
paste
obtained
passes
into
the
de-stoning
section.
The
olive
paste
is
further
broken
by
impacting
the
shaft's
blades
and
rubbing
the
perforated
plate.
Then
broken
olive
paste
and
broken
stones
having
dimensions
smaller
than
plate
holes,
are
removed
from
the
bowl.The
remaining,
largest
part
of
the
stones,
are
held
in
the
bowl
and
successively
discharged.
Finally,
the
partially
de-stoned
olive
paste
is
conveyed
in
the
malaxing
pool.
During
the
tests,
about
60%
of
stone
fragments
were
extracted.
Samples
were
collected
according
to
the
following
schedule:
Before
every
test,
olives
were
sampled
and
stored
at
4.0
°C
in
plastic
containers.
After
the
centrifugal
separation
in
a
vertical
plate
centrifuge,
oil
was
sampled
and
stored
at
4.0
°C
in
dark
glass
bottles.
Rheological
measurements
The
olive
paste
samples
obtained
using
the
two
different
crush-
ing
machines
were
subjected
to
rheological
analysis
through
a
Brookfield
rotational
remoter,
model
DV2-HBT
(Brookfield
Engi-
neering
Laboratories,
Inc.,
Stoughton,
MA,
USA)
equipped
with
interchangeable
disc
spindles,
2-7
(model
RV/HA/HB;
Brookfield
DVII
+
Brookfield
Engineering
Laboratories).
Viscosity
measure-
ments
were
carried
using
600
mL
of
olive
paste,
loaded
into
1000-mL
glass
containers
conditioned
at
27
°C
in
a
thermostatic
bath.
The
apparent
viscosity
of
each
sample
was
recorded
at
10
rotational
speeds
ranging
from
0.5
to
100
rpm,
using
the
RV/HA/HB-4
spindle.
To
interpret
the
experimental
results
in
terms
of
viscosity,
the
torque-speed
data
and
scale
readings
were
con-
verted
into
shear
stress-shear
rate
relationships
using
numerical
conversion
values.
An
empirical
power-law
model
was
used
to
cal-
culate
the
apparent
viscosity
and
flow
behaviour
index
from
the
shear
rate
using
the
equation
ti
app
=
kyfr
7-11
,
where
tj
app
is
the
appar-
ent
viscosity,
y
is
the
shear
rate
(s
-1
),
n
is
the
flow
behaviour
index
(dimensionless),
k
is
the
consistency
index
(Pa
s").
Three
replicate
trials
were
performed
for
each
sample.
Quantitative
index
determinations
During
the
comparative
tests
the
yield
(Y)
was
measured,
olives
and
olive
oil
was
sampled
in
order
to
determine
the
extraction
efficiency
(EE)
and,
finally,
the
quality
of
the
oil
obtained
from
whole
and
partially
de-stoned
olives
was
determined.
To
determine
the
amount
of
stone
recovered
from
the
machine,
during
each
experimental
test
all
the
stone
output
from
the
machines
has
been
stored
in
a
bin
and
subsequently
weighed.
To
determinate
the
percentage
of
stone
in
the
olives,
a
represen-
tative
sample
of
olives
(200
units)
was
manually
de-stoned.
Subse-
quently,
the
stones
was
cleaned
and
weighed.
Qualitative
index
determinations
Free
fatty
acids,
peroxide
index
and
ultra-violet
light
absorption
K232
and
K270
were
determined
by
the
methods
reported
in
Regulation
EEC/2568/91
of
the
European
Union.
Total
phenolic
content
The
phenols
were
recovered
from
the
oils
using
a
liquid-liquid
extraction
with
methanol,
following
the
procedure
reported
by
Gambacorta
et
a1.
30
Phenolic
extract
(100µL)
were
pipetted
in
a
10
mL
test
tube,
mixed
with
100µL
2
mol
L
-1
Folin
-Ciocalteu
reagent
and
after
4
min,
with
800
5%
Na
2
CO
3
.
The
mixture
was
then
heated
in
a
40
°C
water
bath
for
20
min
and
the
total
phenol
content
was
determined
colorimetrically
at
750
nm.
The
standard
curve
was
prepared
using
diluted
solutions
of
gallic
acid
in
methanol/water
(70:30,
v/v),
using
the
same
procedure
described
for
the
phenolic
extracts.
The
total
phenolic
content
was
expressed
as
gallic
acid
equivalents
(mg
kg
-
').
Analyses
of
volatile
compounds
Extraction
For
each
treatment
replicate,
40.0
g
of
oil
was
added
with
0.50
mL
of
2-methyl-1-pentanol
as
internal
standard
(IS),
obtaining
a
con-
centration
of
10.3
mg
kg
-
'.
Three
grams
of
sample
of
the
spiked
oil
were
introduced
into
a
10
mL
headspace
vial
fitted
with
a
Teflon-lined
septum
sealed
with
an
aluminium
seal
and
anal-
ysed.
The
volatile
compounds
were
extracted
by
exposing
the
solid-phase
microextraction
(SPME)
fibre
(PDMS/DVB,
50/30
µm,
20
mm
long)
for
30
min
in
the
sample
headspace
kept
in
a
40
°C
water
bath,
and
subsequently
inserted
into
the
injection
port
of
the
gas
chromatography-
mass
spectrometry
(GC/MS)
system.
The
J
Sci
Food
Agric
(2016)
©
2016
Society
of
Chemical
Industry
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Romaniello,
A
Leone,
A
Tamborrino
www.soci.org
fibre
was
conditioned
for
20
min,
before
the
exposure
to
the
sam-
ple
head-space,
by
placing
the
fibre
in
the
GC
injector
under
con-
stant
flow
of
helium
at
a
temperature
of
210
°C.
Identification
by
gas
chromatography-mass
spectrometry
A
6890
N
series
gas
chromatograph
(Agilent
Technologies
Inc.,
Santa
Clara,
CA,
USA)
with
an
Agilent
5975C
mass
selective
detector
(MSD)
and
equipped
with
a
DB-Wax
capillary
column
(60
m
x
0.25
mm
I.D,
0.25
µm
film
thickness;
J&W
Scientific
Inc.,
Fol-
som,
CA,
USA)
was
used.
Helium
was
used
as
carrier
gas
at
a
flow
rate
of
1.0
mL
min'.
Oven
temperature
was
set
at
40
°C
for
4
min,
followed
by
a
temperature
gradient
of
3
°C
min'
to
140
°C,
with
a
final
post-run
of
10
min
at
200
°
C.
The
mass
spectrometer
operated
in
the
electron
impact
mode
(ionisation
energy,
70
eV)
using
a
mass
range
of
m/z
30-400
amu.
The
identification
of
compounds
was
performed
comparing
the
retention
times
with
those
of
standard
compounds,
when
avail-
able,
and
mass
spectra
with
those
of
the
data
system
library
(N
IST011,
P>
90%).
For
quantitative
analysis
purposes,
the
method
error
was
minimised
by
using
internal
standard
peak
area
normal-
isation.
Quantification
of
volatile
compounds
from
olive
oil
was
achieved
by
multiplying
the
ratio
of
analyte
peak
area
to
IS
peak
area
(mean
value,
n
=
3)
by
the
IS
concentration,
expressed
as
mg
internal
standard
equivalents
kg
-
'
oil.
The
associated
standard
deviation
was
determined
by
means
of
error
propagation
calcula-
tion
taking
into
account
the
estimated
error
due
to
the
IS-spiked
oil
preparation
and
the
standard
deviation
obtained
from
replicates
for
each
compound.
All
analyses
have
been
made
in
triplicate.
Sensory
analysis
Sensory
analysis
was
performed
according
to
the
EU
Regulation
1989/2003
(2003),
in
a
sensory
room
equipped
with
boots
accord-
ing
to
ISO
standard
8589.
3
'
Statistical
analysis
Averages
and
standard
deviations
calculation,
and
ANOVA
(using
Tukey's
HSD),
calculated
with
a
95%
confidence
interval)
were
performed
using
the
MATLAB
statistics
toolbox
(The
MathWorks,
Inc.,
Natick,
MA,
USA).
In
particular,
for
each
trial
(HC
and
PDM),
three
items
of
analytical
data
were
collected
for
each
of
three
replicas.
The
three
analytical
data
were
meant
obtaining
one
data
for
each
trial
(HC
and
PDM).
RESULTS
AND
DISCUSSION
Rheological
characteristics
of
olive
pastes
The
different
rheological
characteristics
of
the
two
of
olive
paste's
type
are
shown
in
Fig.
3.
The
characteristics
of
the
shear
stress/shear
rate
relationship
were
a
downward
concav-
ity,
denoting
the
pseudo-plastic
characteristic
of
both
olive
pastes
considered.
The
apparent
viscosity
was
determined
applying
the
power
law
model
and
plotted
in
log-log
scale
(Fig.
4),
to
better
compare
the
behaviour
of
HC
and
PDM
pastes.
PDM
paste
shows
lower
values
of
apparent
viscosity
than
HC
paste,
because
the
higher
adherence
due
to
the
less
quantity
of
stone
respect
to
HC
paste.
The
apparent
viscosities
were
statistically
different.
These
results
could
be
associated
with
the
absence
of
an
olive
stone
fraction.
Viscosity
is
an
important
process
parameter
of
the
olive
oil's
extraction
cycle.
It
influences
the
liquid-solid
separation
in
500000
450000
400000
L
i.
350000
g
macron
250000
200000
150000
100000
50000
500
10.00 15.00
20.00
25.00
3000
35,09
Shaer
rate
(al
Figure
3.
Effect
of
shear
rate
on
shear
stress,
for
the
two
trials
(HC
and
PDM).
10000000
1000000
mom
a
10000
1000
0.10
11,0
10.00
Shear
rate
I's')
Figure
4.
Effect
of
shear
rate
on
apparent
viscosity,
plotted
in
log-log
scale,
for
the
two
trials
(HC
and
PDM).
Different
letters
denote
significant
differences
(ANOVA
and
HSD
test,
P
<
0.05).
Table
1.
Quantitative
parameters
Test
Yield
(%
wt/wt)
EE
(%
wt/wt)
Stone
recovered
(%
dried
basis)
HC
PDM
14.9
+
0Aa
15.4
±
0.5a
83.5
+
2.3
a
86.3
±
2.5a
0.00
65.1
±
0.7
The
extraction
efficiency
(EE)
was
calculated
considering
17.84%
of
oil
contained
in
the
olives.
Stone
recovered
was
calculated
considering
12.00%
(dried
basis)
of
stones
contained
in
the
olives.
Same
letters
in
the
same
column
indicate
not-significant
difference
among
mean
values
(ANOVA
and
HSD
test,
P
<
0.05)
for
the
two
trials
(HC
and
PDM).
HC,
hammer
crusher;
PDM,
partial
de-stoner
machine.
the
horizontal
centrifugation.
Thus,
it
is
important
to
reduce
the
viscosity
before
the
olive
paste
enters
the
horizontal
cen-
trifuge.
To
achieve
this
goal
the
olive
paste
is
subjected
to
thermo-mechanical
conditioning,
through
malaxation,
and
to
the
addition
of
water
before
the
horizontal
centrifugation.
Therefore,
further
investigations
are
necessary
in
order
to
verify
if
the
viscos-
ity
decrease
due
to
the
absence
of
an
olive
stone
fraction
could
lead
to
a
decrement
of
malaxation
time
or
to
an
increment
of
the
horizontal
centrifuge's
flow
rate.
Quantitative
performance
of
the
virgin
olive
oil
extraction
plant
The
extraction
plant's
performances,
shown
in
Table
1,
have
been
calculated
considering
that
the
oil
percentage
in
the
olives
was
17.84%
and
the
stone
percentage
in
the
olives
was
12
%
(dried
basis).
HO
PM
power
fitting
HC
KW
—power
Ming
y=
2104690
,92
R'-0.99011.
y
=1209580
0
2
=0.99422
100.00
©
2016
Society
of
Chemical
Industry
J
Sci
Food
Agric
(2016)
A
new
de-stoner
machine
for
efficient
recovery
of
olive
stones
www.soci.org
SCI
Table
2.
Qualitative
index
and
phenolic
content
Test
Free
acidity
()
Peroxide
value
(meq
[0
2
]
kg
-1
)
K232
K270
Total
phenolic
content
(mg
kg
-1
)
HC
0.50
±
0.03
a
5.5
+
0.1a
1.84
+
0.02
a
0.13±0.01
a
342
+10a
PDM
0.46
±
0.02
a
4.8
+
0.1b
1.81
+
0.02a
0.12+
0.01
a
348
+
14a
Different
letters
in
the
same
column
indicate
significant
difference
among
mean
values
(ANOVA
and
HSD
test,
P
<
0.05)
for
the
two
trials
(HC
and
PDM).
HC,
hammer
crusher;
PDM,
partial
de-stoner
machine.
Table
3.
Volatiles
compound
of
olive
oils
obtained
from
whole
and
partial
de-stoned
olives
Compound
RT
(min)
HC
PDM
C
5
and
C
6
compounds
Aldehydes
Hexanal
15.0
1.09
+
0.01b
1.28
+
0.04a
(E)-2-Pentenal
16.6
0.141
+
0.005b
0.181
+
0.007a
(Z)-3-Hexenal
17.6
0.051
±0.003
b
0.061
±0.001
a
(E)-2-Hexenal
21.6
17.03
+
0A2b
24.27
+
0.87a
2-Methyl-butanal
8.7
0.33
+
a02a
0.26
+
0.01
b
3-Methyl-butanal
8.8
0.295
±
0.016a
0.252
±
aoob
Ketones
Pentan-3-one
10.8
4.09
+
0.31a
4.23
+
0.17a
Penten-3-one
12.5
0.31
±0.01
b
2A2
+
0.19
a
Alcohols
Pentanol
23.1
0.088
±
0.002a
0.078
±
0.006b
Penten-3-ol
18.8
1.24
+
0.0V
1.31
±0.10
a
(E)-2-Pentenol
26.0
0.102
±
0.008
a
0.091
±
0.007a
(Z)-2-Pentenol
26.4
0.65
±
0.02a
0.70
±
0.05a
Hexanol
27.9
1.98
+
ao6b
2.15
+
0.05
a
(E)-2-Hexenol
30.2
4.14
+
0.11a
3.79
+
0.26
a
(Z)-3-Hexenol
29.3
0.233
±
0.009a
0.231
±
0.006a
2-Methyl-propanol
15.8
0.279
±
0.020a
0.218
±
0.006b
2-Methyl-butanol
21.0
0.156
+
0.012
a
0.109
+
0.005
b
3-Methyl-butanol
21.1
0.66
+
a03a
0.47
+
ao2b
Other
volatile
compounds
Acetic
acid
ethyl-ester
8.0
0.78
+
0.01a
0.58
+
0.03
b
3-Ethyl-1,5-octadiene
12.0
0.255
±
aoosb
0.293
±
0.018a
Sum
of
all
compounds
-
33.91
+
0.55b
42.96
+
0.96
6
Different
letters
in
the
same
row
indicate
significant
difference
among
mean
values
(ANOVA
and
HSD
test,
P<
0.05)
for
the
two
trials
(HC
and
PDM).
HC,
hammer
crusher;
PDM,
partial
de-stoner
machine.
As
reported
in
Table
1
no
significant
differences
were
registered
for
Y
and
EE
in
both
trials.
As
reported
in
Amirante
et
al.,
22
the
decanter
decreased
its
efficiency
when
totally
de-stoned
pastes
were
used,
whereas
the
present
study
shows
there
were
no
losses
in
efficiency
when
partially
de-stoned
olive
pastes
were
processed.
This
means
that
probably
an
amount
of
about
40%
of
the
stone
fragments
in
the
olive
paste
is
sufficient
to
avoid
the
technological
problems
during
the
malaxation
and
centrifugation
reported
in
the
introduction
section.
This
result
appears
to
be
very
important
for
the
use
of
de-stoning
systems
in
the
mill,
also
considering
the
percentage
of
recovered
stone
(about
65%)
to
be
used
for
energy
production
or
other
purposes.
Fruity
8.0
7.0
6.0
5.0
3.0
2
4.1.20
1
/0
av„
Pungent
\
17
Bitter
Figure
5.
Positive
attributes
of
oils
obtained
using
the
partial
de-stoner
machine and
the
hammer
crusher.
Qualitative
index
and
phenolic
content
of
the
virgin
olive
oils
analysed
Table
2
shows
the
effects
of
the
PDM
on
the
main
quality
indices
of
the
obtained
oils.
In
all
samples
the
main
quality
indices
analysed
remained
below
the
limits
reported
by
Regulation
EEC/1989/2003
(22)
of
the
European
Union
Commission,
which
prescribes
free
fatty
acid
content
<
0.8
g
[oleic
acid]/100
g
[oil],
peroxide
value
<20
meq
[0
2
]
kg
-1
,
K232
<2.50,
K270
<0.22.
All
samples
showed
very
low
percentages
of
free
fatty
acids
and
the
data
highlighted
that
the
partial
de-stoning
did
not
affect
oil
acidity
confirming
the
results
reports
in
literature.
26
Opposite
results
were
reported
by
Del
Caro
et
aL
32
Concerning
the
peroxide
index,
the
difference
between
HC
and
PDM
samples
was
statistically
significantly
different,
in
agreement
with
the
results
obtained
by
Saitta
et
aL
33
but
not
in
agreement
with
the
results
obtained
by
Del
Caro
et
aL
32
or
by
Gambacorta
et
al.
34
Finally,
the
total
phenolic
content
of
oils
obtained
using
PDM
and
HC
did
not
show
significant
differences.
The
phenolic
compounds
affect
quality
of
virgin
olive
oil
since
they
contribute
to
the
sensory
characteristics
and
delay
the
oxida-
tive
degradation
process,
thus
prolonging
the
product
shelf
life.
Several
researches
have
shown
that
the
total
olive
de-stoning
dur-
ing
the
mechanical
extraction
process
of
V00
increases
the
phe-
nolic
concentration
in
V00.
22
'
25
'
35
'
36
As
already
reported
by
Servili
et
a
I.,
23
oils
from
de-stoned
olives
showed
higher
concentrations
of
phenol
compounds
than
oils
from
whole
fruits,
with
significant
difference
Volatile
compounds
The
influence
of
PDM
on
volatile
compounds
in
the
extracted
oils
has
been
investigated.
All
analysed
EVOOs
showed
significant
modifications
in
terms
of
volatile
compounds.
HC
PDM
J
Sci
Food
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(2016)
©
2016
Society
of
Chemical
Industry
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Romaniello,
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Leone,
A
Tamborrino
www.soci.org
The
identified
volatile
compounds,
including
C5
and
C6
compounds
classified
in
aldehydes,
ketones,
alcohols
and
other
volatile
compounds,
are
reported
in
Table
3.
All
of
these
compounds
are
known
as
contributors
to
the
olive
oil
aroma.
In
both
trials,
(E)-2-hexenal,
a
product
of
the
lipoxygenase
pathway,
37
which
provides
the
typical
'green
note'
of
olive
oil,
resulted
the
C6
dominant
aldehyde.
(Z)-3-Hexenal,
(E)-2-pentenal,
and
hexanal
were
detected
in
lower
quantity
than
(E)-2-hexenal
but
all
of
the
five
aldehydes
resulted
statistically
plentiful
in
the
trial
PDM.
On
the
other
hand,
despite
2-
and
3-methyl-butanal
being
statistically
different
among
the
trials,
they
were
detected
in
a
higher
amount
in
CM
than
PDM.
In
the
other
volatile
com-
pounds,
aldehydes
including
2-
and
3-methyl-butanal
(sweet,
fruity,
malty
notes),
38
come
from
possible
fermentations
or
amino
acid
conversion
pathways.
If
present
in
large
amounts,
these
aldehydes
are
generally
negatively
attributed
to
off-flavour
tastes.
Similarly,
pentan-3-one
was
also
among
the
most
abundant
ketones,
but
it
did
not
showed
statistical
differences
among
HC
and
PDM
trials.
On
the
contrary,
penten-3-one
was
statistically
different
among
the
trials.
Penten-3-one
is
usually
found
in
oils
principally
produced
from
unripe
olives.
This
compound
has
been
attributed
to
fruity,
green
and
pleasant
scents
38,
"
and
positively
correlated
with
pungency
and
bitterness,'
but
has
also
been
associated
with
a
metallic
off-flavour."
Alcohols
identified
included
mainly
C5
and
C6
compounds,
such
as
pentanol,
penten-3-ol,
(E)-2-pentenol
and
(Z)-2-pentenol,
(E)-3-hexenol
and
(Z)-3-hexenol,
(E)-2-hexenol
and
hexanol,
2-methyl-propanol,
and
2-
and
3-methyl-butanol.
All
of
these
compounds
derive
from
the
lipoxygenase
pathway.'
(Z)-3-Hexenol
has
been
negatively
associated
with
bitter
taste.
Hexanol
and
(E)-2-hexenol
have
both
been
considered
as
eliciting
odours
that
are
not
very
agreeable,'
whose
accumulation
was
shown
to
be
favoured
by
high
malaxation
temperatures.
Results
are
statistically
different
among
trials.
These
results
are
in
agreement
with
those
reported
by
several
authors
who
have
shown
that
olive
stoning
during
the
mechanical
extraction
process
of
EVOO
increases
the
composition
of
volatile
compounds
produced
by
the
LOX
pathway,
increasing
the
concen-
tration
of
those
volatile
substances
correlated
to
the
'green'
sen-
sory
notes.
These
results
are
particularly
important,
because
they
would
appear
to
demonstrate
that
the
enzymes
involved
in
the
LOX
pathway
have
a
different
activity
in
the
pulp
and
in
the
seed
of
the
olive.
23
Sensory
evaluation
Figure
5
shows
the
positive
attributes
(fruitiness,
bitterness
and
pungency)
of
oils
from
whole
and
partial
de-stoned
olives,
respec-
tively.
All
oils
were
free
from
defects.
After
the
production,
oils
from
PDM
showed
a
more
intense
fruity
and
bitter
attributes
and
a
little
difference
in
the
pungent
attribute
than
oils
from
whole
olives.
In
addition,
the
fruity
attribute
of
the
oil
from
PDM
showed
green
fruity
and
green
almond
attribute
than
the
whole
oil,
which
showed
ripe
fruity
and
ripe
almond.
The
partial
de-stoned
oils
were
more
fragrant
with
respect
to
the
controls
and
had
a
delicate,
delicious
and
harmonic
aroma
and
flavour.
The
sensory
evaluation
confirms
the
results
obtained
in
terms
of
volatile
compounds
and
is
in
agreement
with
data
reported
in
the
literature
by
Servili
et
a1.
23
and
Ranalli
et
al?'
CONCLUSIONS
The
total
de-stoner
machines
are
efficient
and
capable
of
separat-
ing
the
olive
fruit
stone
from
the
pulp.
Using
the
total
de-stoner
instead
of
mechanical
crusher
led
to
disequilibrium
in
the
pro-
cess
cycle
determining
an
increase
of
oil
lost
in
the
husk
and
then
a
reduction
in
extraction
yield.
The
latter
is
determined
by
a
reduction
in
efficiency
both
in
the
malaxation
process
and
in
the
solid-liquid
separation
process,
caused
by
the
total
absence
of
olive
pits.
Thus,
as
this
study
pointed
out,
it
can
be
asserted
that
using
the
PDM
the
problems
described
above
were
eliminated,
allowing
the
correct
functionality
of
the
centrifugal
decanter
and
consequently
the
correct
solid-liquid
separation
process.
In
fact,
the
present
research
demonstrated
that
leaving
40%
of
pits
in
olive
paste
(as
pits
fragments)
the
EE
loss
at
decanter
level
is
avoided.
The
EE
measured
when
PDM
and
mechanical
crusher
were
used
did
not
show
statistical
differences.
Additionally,
it
is
notable
that
the
oils
obtained
using
PDM
are
characterised
by
higher
green
fruitiness,
flavour
and
aroma
with
respect
to
those
produced
using
traditional
processing
systems.
These
oils
may
result
in
better
acceptance
by
consumers
who
able
to
appreciate
the
sensorial
peculiarity
of
the
oils.
In
addi-
tion,
the
PDM
allows
the
pits
recovery
to
be
used
as
biomass.
It
is
to
be
noted
that
nowadays
the
goal
of
environmental
sustain-
ability
is
oriented
to
the
use
of
renewable
energy
instead
of
fos-
sil
fuels
and
the
global
goal
is
to
increase
the
use
of
biomasses
for
energy-consuming
processes.
In
the
last
years
a
machine
to
recover
50%
of
olive
pits
from
husks
was
developed
and
inserted
in
olive
oil
plants
but
its
use
represents
an
additive
cost
for
the
miller.
The
PDM
allows
substituting
the
crusher
machine
and,
in
addition,
produces
de-stoned
paste
with
about
60%
of
olive
pits
recovered
and
usable
as
biomass.
Considering
the
results
obtained,
the
authors
can
assert
that
the
use
of
PDM
represent
a
new
solution
to
obtaining
oils
having
different
sensorial
characteristics
with
respect
to
those
obtained
through
the
traditional
technology
(mechanical
crushers)
and
to
produce
biomass.
Further
investigations
are
necessary
to
assess
the
PDM
setting,
considering
different
percentages
of
olive
stones
recovered,
in
order
to
evaluate
yield
and
olive
oil
quality.
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