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Abstract
Initial low oxygen stress (ILOS) followed by ultra low oxygen
(ULO) regimes was applied for many years on small quantities
of Red Delicious apples grown at 600 m altitude in Val di
Non valley in Trento province ( Italy ).The positive results,
obtained in more than six years commercial tests, in terms
of superficial scald prevention and inhibition, were confirmed
by the scientific evaluations done by the extension service
technicians of the IASMA (Istituto Agrario San Michele all’Adige).
In 2001 and 2002 the AVN Cooperative together with IASMA and
FCE (Fruit Control Equipments) in active interaction decided
to apply definitely the operating procedures for ILOS +ULO
on the CA storage rooms of Red apples, for a total amount
of fruits of more then 600.000kg. During 6 months storage
period of each year, fruits were evaluated at 2 weekly intervals
during 15 days of regular storage at 20°C directly by
the technician of the cooperative at site, while at same time
other laboratory tests were carried out at IASMA. Results
were always positive and well accepted by the Cooperative.
All tecniques involving no-chemical solutions are considered
of primary importance for AVN, in accordance with their rigid
integrated production protocol. It is therefore confirmed
that ILOS+ULO is practically applicable in harmony with qualified
technological solutions, validated by IASMAA with their on-site
extension service and laboratory evaluations and supported
by the Customer’s satisfaction. No chemicals application,
whenever possible is beneficial for Consumers health.
INTRODUCTION
The experimental application of initial low oxygen stress
(ILOS) for the superficial scald control, besides the beneficial
effects on apples' quality keeping, is known since long time
(Truter et al., 1994) with the best results obtained particularly
in combination with ultra low oxygen (ULO) conditions (Little
et al., 1982; Wang and Dilley, 2000). After six years of experimental
tests on small lots of Red Delicious and Golden Delicious
apples with positive evaluation on the effects of better quality
aspects such as pulp firmness and acidity (Rizzolo et al.,
1997), and superficial scald control ( Visai et al., 1997),
it was decided to apply on commercial scale the previous years
knowledge (Mattè and Buglia 1997) during the years
2000/01, 2001/02 and 2002/03. Commercial apple rooms of more
than 300 tons each of Red Delicious apples were treated with
ILOS + ULO, at the Cooperativa Alta Val di Non, in Casez (Val
di Non Valley-Trentino - Italy), belonging to Melinda Group.
This choice was agreed with the sales managers of Melinda,
strongly motivated by commercial reasons related to the sales
of Red Delicious apples on the market after few months of
storage with no chemical residues of post harvest treatments
(DPA 31%). Specific protocols were applied, considering the
variability of the apples introduced into the rooms and the
risks of the initial ILOS treatments: 1) reliability of the
technical plants ( room tightness, refrigeration system, CA
equipments); 2) harvesting (picking window); 3) continuous
monitoring of ILOS efficacy on the apples ( periodical shelf-life
tests); 4) ethanol check inside the apples after two weeks
of ILOS treatment. A synergic working group was established
among the technology supplier (Fruit Control Equipments),
research and extension service centre (I.A.S.M.A.) and the
qualified personnel of the technical storage staff and the
commercial staff of the AVN Cooperative in Casez with the
beneficial effects of reducing risks up to the AVN staff.
The evaluation of the results obtained in 3 different years
(2000/2001, 2001/2002, 2002/2003), out of the commercial aspects
during the shelf life period, comparing D.P.A treated apples
with ILOS+ULO treated ones, were looking at conventional laboratory
tests (physio-chemical analysis of fruits), at physio-pathological
tests (evaluation on scald effect) and tests on the aromatic
compounds emission (ethylene and other volatiles), as reported
with interesting results by Lopez et al., (1998 a-b), in combination
with a new research technology: P.T.R.M.S.(Proton Transfer
Reaction Mass Spectrometry) (Boschetti et al., 2003).
MATERIAL AND METHODS
The whole production of Red Delicious apples of the Cooperative
AVN in Casez (Val di Non Valley- Trento- Italy) have been
used in more than 320 tons CA rooms capacity (each room of
1410 m3) during the three years of commercial application
(2000/2001, 2001/2002, 2002/2003).
Apples have been picked by the associated growers, inside
the restricted picking window suggested by the "U.O.
Frutticoltura-Conservazione", the extension service operating
group of the IASMA:
The compared thesis were for all the apples of each room as
following:
Room A 2000 ppm DPA 31% (by drencher) + ULO (0,9-1% O2; 1-1,2%CO2
at T 0,8-1,2 °C and 95% RH
Room B ILOS (15 days at 0,5 % O2 ) + ULO as for room A
Room C ULO Test
ILOS and ULO conditions inside the commercial rooms at AVN
were possible thanks to the high technological level of the
installation:
perfect gas tightness of the rooms (from an initial pressure
test of 30 mm of water column, down to 25 mm in 30 min); refrigeration
system (NH3 + glycol) with cooling capacity of 60,000 kg/day
of apples (20 % of the capacity of each room) and large surface
evaporators of about 0,6 m2 /m3 of room with fans capacity
of 35-40 air recycling /hr , Delta T of 2°C , defrosting
system by water + air; membranes Nitrogen generator, type
SWAN with >320 m3/h of N2 and possibility to pull-down
the oxygen in each room at 5-6% in less than 8 hrs, followed
by final adjustment at 0.5% ,done by fruits respiration in
other 7 days; single CO2 adsorbers for each room, with capacity
of 25 Kg CO2/day at 1% of CO2 in the room; gas analysers(thermo-paramagnetic
for O2 and infrared for CO2 ) and sophisticated computerized
control system, in combination with daily manual control;
high professional technical education of the personnel in
charge of the CA system and comprehensive attention of the
sales department of the cooperative. The storage periods of
the apples were:
a) 32 + 1 weeks in 2000/2001; b) 30 + 1 weeks in 2001/2202
c) 27 +2 and + 3 weeks in 2002/2003.
Quality measurements and physio-pathological controls were
applied on 4 bins of Red D. apples (for a total amount of
~1400 Kg) stored in each room, coming from the same grower.
An equal quantity of control fruits from the same grower were
stored in normal ULO conditions.
The preliminary checks were done on: 1) ethylene production
by treated fruits ( ILOS and DPA+ULO ); 2) ethanol concentration
inside the apples after treatments (ILOS and DPA+ULO ); 3)
periodical visual evaluation of superficial scald on apples
taken at room temperature for 7 +7 days, in order to determine
the eventual anticipated opening of the room and consequent
sale of the apples in time, in case of high scald development.
The qualitative methods at picking time and at the end of
the storage period were applied with validated methods (Rossier
et al., 1998; Zanella and Werth, 2002 ) on randomised 400
fruits , divided in 4 lots and for Pimprenelle analysis to
determine: 1) firmness ( kg/cm2); 2) sugar content (°
Brix ); 3) acidity (Malic acid, gr/l ) quality index ( Thiault
). In 2001-2002, at three different storage periods, volatiles
produced by apples were also measured using PTR-M;S method.
The physio-pathological checks were done on: 1) evaluation
( % ) of superficial scald affected apples at different stage
(slight: < 30% of the skin; medium: 30-60% ; high: >60%);
2)disorders ( % of Internal breakdown etc) after 7+7 days
shelf life at room temperature (20-22 °C) at the end of
the storage period.
RESULTS
Year 2000-2001:
Superficial scald: ILOS+ULO and DPA+ULO treatments, after
32 weeks of storage, resulted similar in response to scald
control (0.25 – 0.00 %) compared to non DPA treated
apples, where scald developed at 35.7%.
Increased incidence of total scald development (10.5 -20.5
%) and appearance severity (sever 0-6.3 %; medium 0-3.7%-6.5%)
were noticed after 7 and 14 days shelf life at room temperature.
Under same conditions, DPA+ULO has a good total scald control
(5.5%) even after 7+7 days with a slight gravity increase
( 0-0.25%, medium and severe ). The ULO Test apples have a
continuous progressive incidence of scald from the opening
time of the room until 7+7 days of shelf live period (from
35.7 to 79.9 % of total scald and % of incidence from 13.2
to 21.6 slight , from 10.2 to 23.2 medium and from 12.3 to
35.1 severe).
Other pathologies: Gleosporium spp., Monilia spp. and Penicillium
spp are reported at lower incidence (0.5%) even after 7+7
days shelf life on ILOS+ULO apples, while in the other two
thesis are reported at higher incidence (2.1 and 2.8%).
Quality parameters: Physical-chemical parameters were obtained
in three different periods: at harvest, after 32 storage weeks
and 32 weeks + 1 week at room temperature with following results:
Flesh firmness: ILOS + ULO and DPA + ULO resulted beneficial
in keeping firmness higher compared to ULO test apples particularly
after 32+1 weeks (6.8 and 6.5 Kg/cm2 against 5.9 Kg/cm2).
Soluble solids: there was no effect by the different treatments
on the natural S.S. °Brix increase during the storage
period, as well as after 32+1 weeks. Acidity: ILOS+ULO treated
apples show a higher malic acid content (5,6 g/l) after the
storage period compared to the other two thesis (4.1 and 4,1
g/l), which was even kept after 1 week at room temperature
(4.3 g/l compared to 4.0 g/l DPA+ULO and 3.8 g/l ULO Test).
Quality Index: the I.Thiault quality Index, evaluated as reported
by Alavoine et al., (1988), show a significant higher value
for the ILOS+ULO apples after 32 weeks of storage, as well
as after 32 weeks + 1 week at room temperature, compared to
the other two thesis. Internal ethanol: in order to determine
the level of anoxia risk of the apples after the ILOS storage
period, the evaluation of the ethanol content inside the apple
flesh was done. GC-HPLC was used to evaluate the ethanol content
after extraction from apples samples (1.5 kg). The ethanol
content was higher (140 ppm) after 15 days of ILOS treatments,
decreasing to 60 ppm after 10 days of ULO. Ethanol content
was normal in the other two thesis(80 ppm for DPA+ULO and
40 ppm for ULO Test).
Year 2001-2002
Superficial scald: ILOS+ULO and DPA+ULO treatments, after
25 weeks of storage, resulted similar in response to scald
control (0.25- 0.00 % )
ILOS+ULO apples show an increase of total scald incidence
as well as gravity in appearance after 30 weeks storage +1
week at room temperature, but at similar levels to those ones
of DPA+ULO (8.0 % total scald against 6 %). The 2 % points
difference for ILOS+ULO is related to a light superficial
scald. Other pathologies: No particular fungus attacks were
observed during the first 25 weeks of storage in both observed
thesis (ILOS+ULO and DPA+ULO). Gleosporium spp., Monilia spp.
and Penicillium spp are reported at lower levels ( 1.2% )
even after 30 weeks + 1 week shelf life on ILOS+ULO apples,
while in the other DPA+ULO thesis are reported at slight higher
levels ( 2.2 % ). Quality parameters: Physical-chemical parameters
were obtained in four different periods: at harvest, after
25 W, after 28 W + 1 W at room temperature, after 30 W+ 1
W at room temperature with following results:
Flesh firmness: ILOS + ULO resulted beneficial in keeping
firmness higher after all storage periods compared to DPA+ULO,
with less decrease after picking even after 28 and 30 W +
1 (6.8 kg/cm2 against 4.8 Kg/cm2). Soluble solids: there was
no effect by the different treatments on the natural S.S.
°Brix increase during the storage period up to 21 + 1
W, while an increase of sugar was reported after 30+1 W for
ILOS+ULO apples. Acidity: ILOS+ULO treated apples show a higher
malic acid content during all the three post harvest checks
(4.8- 4.6- 4.1 g/l) compared to the DPA+ULO thesis (4.4- 3.7-
3.1 g/l). The decrease of apples acidity in ILOS+ULO apples
from harvest to 25 storage W later was extremely low (-0.3
g/l of malic acid). Quality Index: The Thiault Q.Index, evaluated
as reported by Alavoine et al., (1988), shows a similar values
for both thesis, but significant higher value for the ILOS+ULO
apples after 30 W + 1 W at room temperature (due to the increase
of soluble solids). Internal ethanol: The ethanol content
was higher (125 ppm) after 15 days of ILOS treatments, decreasing
to 56 ppm after 10 days of ULO. Ethanol content was absolutely
normal (20 ppm) in the DPA+ULO treated fruits. Ethanol values
were generally lower compared to the previous 2000-2001 years.
Volatile component emission (VOC): The study of the ethylene
dynamic evolution from apples samples (µl/kg/h) from
both thesis show that ILOS+UlO treated apples after storage
have much lower ethylene production (from 3 to 6 times) than
those stored under DPA+ULO . After 1+1 weeks of shelf life
storage the production rate of ethylene are quite similar
in both thesis. Other volatile compounds produced by the apples
have been determined using non destructive methods PTR-MS
in three different periods of storage (after 2-5-7.5 months
of storage).
After two months of storage, ILOS treated apples show higher
quantity emission of some compounds (mass=M43 propanol, M45
acetaldehyde, M61 acetic acid, M89 ethyl acetate, M101 esenal)
compared to the ULO stored apples; After 5 and 7.5 months
of storage there is a substantial reduction of the quantities
emitted and for some of these compounds (M43, M61, M71 methyl-butanol,
M89, M103, M117) a counter trend was shown or equal production
from ILOS+ULO and DPA+ULO apples;
For longer storage periods, some of these compounds, which
characterized the typical Red Delicious "perfume"
(M101, M131, M145 =esters), are equally produced by ILOS+ULO
and ULO Test apples.
Year 2002-2003
Superficial scald: ILOS+ULO and DPA+ULO treatments , after
21 W + 2W of shelf life at room temperature, resulted similar
in response to scald control (0.00 % ) tab8b
ILOS+ULO apples show an increase of 6.2 % of total scald incidence
at light gravity after further 7 days at room temperature.
ILOS+ULO apples show after 26 and 30 weeks of storage + 2
and + 3 weeks of shelf life at room temperature an increase
of the scald as well as its gravity in appearance (from light
2.5% up to severe 10.7%). After 30 weeks storage +2 and 3
weeks at room temperature, DPA+ULO apples show a light medium
1.2% up to 3.5 %.
Internal ethanol and exogenous ethylene production: ILOS treatment
induces ethanol production in the flesh of apples lower than
the previous years, but in any case sufficient to reduce the
exogenous ethylene production up to 3 times less than DPA+ULO
treatment.
DISCUSSION
While ILOS beneficial effects on keeping quality of apples
and preventing scald development are well known and were deeply
studied in the past in experimental tests (Little et al.,
1982, Van Der Merwe et al., 2001; Truter et al., 1994, Wang
and Dilley , 2000), the same cannot be said for commercial
applications, where valuable quantity of apples ( > 300
tons ) are involved. Our commercial application tests done
in last 4 years have shown that this is possible, with very
interesting results on quality and commercial aspects of the
apples as well as for the lower costs in comparison to alternative
solutions ( i.e. post-harvest DPA treatments). In order to
obtain such positive results it is necessary to pay professional
attention either to the equipment reliability or to the periodical
provisional checks. Never to forget that ILOS gives good results
in terms of scald prevention on medium term periods (23 -26
WEEKS), while special attention has to be paid whenever the
storage length should be up to 28-31 weeks. Periodical spot
weekly checks, together with analytical lab tests (ethylene,
VOC, ethanol etc.), allow to ILOS treatments to be fully reliable,
with very low risks for the apples.
tab.8a
tab8b
Three years of commercial tests with different climatic scald
sensibility can easily permit a better comprehension of the
results of ILOS+ULO application (i.e in the years 2001/2002
and 2002/2003), in comparison with the traditional ULO application
in Trentino. From the practical point of view we can summarize:
ILOS choice can represent a “clean” answer to
the market of scald sensibile apples varieties like Red Delicious
even after 6 – 7 months after harvest. Specific technical
requirements must be adopted for the ILOS rooms, specially
on gas tightness and gas analysing and control systems.
Apple lots in each room should be homogeneous (if possible),
cooling and O2 pull-down should be as quick as possible, high
management capacity required for the technician, quick response
in sales planning of apples in between 7-14 days from room
opening date; all these points, together represent indispensable
requirements for applying in the best way ILOS technology
and get the best beneficial effects.
Keeping quality characteristics of apples longer, with no
chemical post-harvest treatments residues, may represent for
ILOS a strategic application for a better qualified distribution
of apples on specific markets, sensible to these points.
The present job may be considered useful not only for opening
new research areas ( i.e. further development of VOC and prevision
scald development survey ), but also to express the validity
of the co-operation between Research and Extension Service
( I.A.S.M.A., San Michele all’Adige, Trento ), the advanced
technology (Fruit Control Equipments , Milano) and the end
user (AVN Cooperative, Melinda group, Casez , Trento).
ACKNOLEDGEMENTS
Special thanks to Mr de Concini Pio, the technician in charge
of refrigeration and CA at AVN Cooperative of Casez (Melinda
group), for his professional and precious collaboration given
inside the working group.
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Paper presented at ”POSTHARVEST2004”, the 5th
International Postharvest Symposium, 6th -11th June 2004 Verona
–Italy-
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