On Tuesday 06 of December, the afternoon was definitely international on the French farm « Gaec des fruits de Bourgogne », managed by Mr Geoffroy. About 30 people participated in the event, including people from Poland, Netherland, Switzerland, Italy and Germany. They have followed the technical presentation by Mr Gratadour, Technical Manager of Rhône Chamber of Agriculture. After 100 days of preservation, the openning of Janny MT modules has shown the good results obtained and the evolution of the experimentation. Many technical exchanges took place while a comparison between the fruits preserved in ordinary cold and those preserved in Janny MT modules was held. This meeting has emphasized several key factors in order to carry out a successful preservation with Janny MT modules on pears.
New development of Dynamic Controlled Atmosphere storage of apples applying repeated and controlled Low Oxygen Stress treatments
Livio Fadanelli (1), F. Zeni (1), L.Turrini (1), P. Barchetti (1), P. Matte’ (2), L. Buglia (2)
(1) Centro di trasferimento Tecnologico FEM-IASMA S.Michele all’Adige (Trento) ITALY, Via E. Mach 1-38010 San Michele all’Adige-Italy
(2) Fruit Control Equipments, Via R. Luxemburg 55-20085 Locate di Triulzi– Italy
The first experiences carried out by U.O. Frutticoltura Segmento Conservazione del Dip. VRP, started in the Trentino region of Italy around year 2000 with trials testing the use of ILOS (Initial Low Oxygen Stress) techniques in commercial warehouses with Red Delicious , Cripps Pink and Granny Smith varieties. Right from the start the outcome was encouraging particularly for the results obtained with regards to scald control and quality preservation (pulp firmness and total acidity) even after 210 days of storage in CA ULO + ILOS and 10 days of shelf life (Mattè P. -Fadanelli L. et al ILOS + ULO AS A PRATICAL TECHNOLOGY FOR APPLES SCALD PREVENTION, 5th International Postharvest Symposium:( Verona, Italy, June 6-11, 2004 ).In 2007 and 2008, the trials continued with applications on 10 commercial cells at 4 cooperatives, all equipped with suitable technological solutions for maintaining and checking the stress conditions. The combination of I.L.O.S. techniques and repeated gas stress treatments in 2-3 intervals during the storage period has in fact produced a type of Dynamic Controlled Atmosphere (DCA). The gas stress treatment consists in maintaining the following conditions :O2=0,5 – 0,7% and CO2 = < 1% over a certain period of time ( 8-15 days). The factor that determines the end of the stress period and therefore the return to the gaseous parameters of U.L.O. (O2 = 1-1,3%, CO2= 1,0-1,3%) is the level of ethyl alcohol accumulated in the fruit pulp, determined by a representative sample batch (20 apples) at weekly intervals. The methods of determination of ethyl alcohol (in GC and by enzymatic reaction) have been perfected to obtain trustworthy and repeatable values. It has been proved that if the levels of ethyl alcohol do not exceed a certain limit, on return to normal respiratory parameters inside the cell, the alcohol content regresses to almost completely disappear and therefore without altering the flavour of the apples. The results obtained in 2007 and confirmed in 2008 for Red Delicious and Granny Smith cultivar. have lead to total control of damage due to scald up to over 8 months in storage without any preventive chemical treatment, as well as maintaining the top qualitative requirements even during the commercial phase of distribution (Shelf life 10-15 days).
The experience was acquired on large scale application of I.L.O.S. techniques on commercial rooms of apples since the beginning of the year 2000 (Mattè P. -Fadanelli L. et al ILOS + ULO AS A PRATICAL TECHNOLOGY FOR APPLES SCALD PREVENTION, 2004). During the years 2007-2009, the technique has developed into the realization of repetition of the low oxygen stress phases in a dynamic way (SwinglosTM), several times during the entire storage period. This technique was again applied on commercial rooms using equipment by Fruit Control Equipments (FCE), Italy and has allowed storage to be carried out in different situations corresponding to various apple production areas on the cultivars Red Delicious, Granny Smith and Pink Lady for up to 8 months + 10 days shelf life, without evidence of scald and/or pulp browning , with optimal quality requirements (Rizzolo.A., Vanoli.M., Visai.C., Fadanelli.L. 1997), & (Visai.C., Vanoli.M., Fadanelli.L. 1997).
To determine the start and the end of the gaseous stress periods a method of measurement of ethyl alcohol accumulated in the fruit pulp has been developed, on a representative sample of 20 apples periodically taken out of the same storage rooms. The gaseous stress conditions ( O2=0,5 – 0,7% and CO2 = < 1%) have been reached thanks to technical solutions (Fig 1) consisting of special N2 Generators, adsorbers with high CO2 adsorption capacity and excellent gas tightness requirements
(Table 1) of the rooms (from 30 or 25mm down to 26 or 22 mm of water column in 30’) The applicative experiences have allowed to identify the accumulation levels of alcohol until the point of interruption of the stress conditions , bringing the apples back to the condition of metabolic respiratory level that allows them to metabolize the alcohol accumulated (Tables 2, 3,4,5).
The repetition of this technique in a dynamic way for 2-3 periods ( 8÷15 days and more, each time) during the storage period, has demonstrated that a complete control over superficial scald even on sensitive cultivars such as Granny Smith (Table 6) and Red Delicious (Table 7)can be obtained.
This application has also shown interesting results with regards to the control of internal breakdown on the Cripps Pink cultivar (Table 8).
MATERIALS AND METHODS
Applicative testing of the new repeated gaseous stress technique were carried out at cooperatives with medium-large sized rooms (350-400 t).
In order to allow an experimental test of the trials , 4 lots of apples of 1000 units for each cultivar, were divided into 2 parts and stored in Dynamic L.O.S.(Low Oxygen Stress) rooms as well as in U.L.O.CA rooms (Red Delicious and Granny Smith cultivar : O2 = 1-1,3%, CO2= 1,0-1,3%), and in conventional C.A rooms (for Cripps Pink cultivar).
For application of the dynamic L.O.S. technique, the necessary requirements of the rooms were:
- Apples with uniform maturity, of the same variety (avoid mixing spur clones and standard), delivered within the first 7 days of the harvest period indicated by the consultancy service (website www.iasma.it),
- Room loading at 25% per day with loading coefficient of 250-260 kg/m3, with uniform cooling and final desired fruit pulp temperature reached within 5-6 days from the first loading day,
- Preparation of representative samples of all lots of apples of the rooms (4-5 apples per lot until obtaining a mix of 4-5 boxes of apples),to be placed in front of the inspection port-hole.
The first oxygen pull down (initial stress) was made within 5-7 days from closing the room with O2 at 0,4-0,5% , maintaining the level of CO2 < 1% according to the varieties: Red Delicious 0,8-0,9 %, Granny Smith 0,7-0,8 %, Cripps Pink 0,5-0,7 %.
After 7 days from the start of gaseous stress the first sample checks were made on 20 apple samples for measurement of the accumulation of ethyl alcohol, repeating them on other samples every 7-10 days until the end of the stress period.
The level of ethyl alcohol detected each time determined the continuation or interruption of the anaerobic gaseous stress treatments.
In Table 9 is shown indicatively the relation between maximum ethanol thresholds verified in our works and considered tolerable for the different apple cultivars and the reversibility of alcohol accumulation without altering taste and flavour of the apples.
The stress periods were regulated in duration according to the level of ethyl alcohol measured in the 20 apple samples tested each time for each room, allowing a dynamic course of the controlled atmosphere with low levels of 02 and CO2.
At the end of each stress period the controlled atmosphere conditions in the rooms were brought back to typical U.L.O. values (O2 = 0,9-1-%, CO2= 0,8-1,0-1,3%) according to the different cultivars.
Determination of the ethyl alcohol content in the fruits. This represents the crucial point of the entire system and is the indicator of the metabolic behaviour of the fruits during the gas stress treatments. The sample analyses must be therefore carried out with great care.
The analyses method adopted initially was the one set up by the FEM-IASMA laboratory using GC-FID technique after centrifugation of the sample in terbutilic alcohol, followed by injection into a glass packed column, filled with 0,2% of stationary phase CW 1500 on Carbopack C, 60-80 mesh (Supelco Inc.)
The instrumental conditions were::
T of detector (FID) = 180°C
T of injector = 180°C
Carrier Gas = N2 at flow rate of ~30 ml/min;
Flame: air flow ~300 ml/min; H2 flow: ~20 ml/min.
Oven temperature setting: Ti= 40 °C; ti = 3 min; rateA = 6°C/min; TfA = 160°C; tfA = 10 min.; rateB = 10°C/min; TfB =170°C; tfB = 20 min.;
Attenuation : 20; range = 100.
Later on, from 2008 the GC method was substituted by a simpler method of ethyl alcohol determination in the fruit juice by enzymatic reaction, quicker and easier to apply. The simultaneous application of the two methods allowed us to compare the results obtained and to estimate the analytical error of the enzymatic method, which was demonstrated to be constant and repeatable (Table 10).
Repetition of the stress periods. At the end of the first stress period, after few weeks of aerobic conditions (O2 > 0,9 %) followed by ethanol tests (Tables 2, 4) , the rooms were pulled down again to low oxygen stress levels for 2 more periods at monthly intervals (during December-January and February-March). As shown, the ethanol levels during these last stress periods remained much lower than during the initial stress and even during the third stress period did not increase. It is therefore fundamental that after completing each stress period, aerobic respiratory conditions are re-established in order to metabolise the ethanol accumulated in the fruit pulp.
The length of the second and third stress periods were of 7-10 days (Tables 3, 5).
Controls. The qualitative methods at picking time and at the end of the storage period were applied with validated methods (Rossier J. Et All., 1998 and Zanella A. and Werth, 2002) on randomised lots of fruits , for Pimprenelle analysis to determine:
- firmness (kg/cm2)
- sugar content (°Brix )
- acidity (Malic acid, gr/l )
- quality index (Thiault )
The physio-pathological tests on 4 casual randomised lots of 400 apples of the cold room. were done on:
- evaluation (%) of superficial scald affected apples in different times (end storage period and after 10 days shelf life),
- disorders ( % of Internal breakdown etc) after 10 days shelf life at room temperature (20-22 °C) at the end of the storage period for Cripps Pink cultivar.
During the entire storage period (7 months), and in particular during the L.O.S. (Low Oxygen Stress) periods, the storage rooms’ gas concentrations were carefully controlled (O2 % -CO2%-N2%), checked with centralized analysers (paramagnetic for O2 and infrared for CO2), supervised by special FCE software with set points and alarms and every 5 days also with a portable analyser.
The room ventilation was guaranteed with 15 minutes of forced air for every hour of pause of the cooling system , in order to obtain from 6 to 7 hours of daily air recirculation inside the room.
The storage temperature was from +0,8 +1°C for Red Delicious and Granny Smith and +1,3 +1,6°C for Cripps Pink, relative humidity(R.H.) ranged from 90-95% for all three cultivars.
The results obtained in the last two years refer to the application of dynamic L.O.S. regimes on 10 commercial apple storage rooms, for a total amount of stored apples of approximately 3.500 tons per year.
The storage was extended in some cases for up to 8 months from harvesting, on average up to 7 months, as evidenced in the enclosed graphs.
On the basis of previous experience, these parameters were realized mainly with the purpose to prevent scald disorder on Red Delicious and Granny Smith and to contain internal breakdown on Pink Lady. These results were confirmed as reported in the graphs with control of superficial scald equal to 98-99% with respect to the Test NT and in accordance with the efficiency of DPA 31% treatment (1800ppm) and U.L.O. storage.
The incidence of internal breakdown on Cripps Pink cultivar was contained after 6 months of storage + 10 days shelf life at 1,0% compared to 8,3% of the thesis in conventional C.A.(T°1,5-2 , RH 90-93% , O2 1,5-2,0%, CO2 1-1,3 %) (Table 8).
Out of the positive results obtained in controlling important physio-pathological disorders , it was also evident how the internal quality of the repeated low oxygen stressed fruits is much better compared to the Test fruits :
- Firmness: +0,4 , +0,8 and +0,4 Kg/cm2 at the end of storage + 10 days shelf life respectively for Red Delicious, Granny Smith and Cripps Pink (Table 11, 12, 13 )
- Acidity: + 0,5 +0,6, 0,5 gr/l of ;Malic acid at the end of storage + 10 days shelf life respectively for Red Delicious, Granny Smith and Cripps Pink (Table 14, 15, 16).
- Sugar content °Brix : the evolution of the sugars during storage appears lower for the Granny Smith (Table 17), while there are no interactions for Red Delicious(Table 18), and Cripps Pink (Table 19).
In conclusion the quality parameters at the end of storage + 10 days shelf life are better in the repeated L.O.S. thesis than with respect to the Test ones.
The evolution of the I.L.O.S. technique applied since the 1990’s (A.B. Truter , J.C. Combrink and S.A. Burger 1994) with the best results obtained particularly in combination with ultra low oxygen (U.L.O.) conditions (C.R. Little et al 1982 and Wang and Dilley 2000) has undergone various evolutions and studies in particular with regards to the effects of ethanol on superficial scald either when applied alone (Chervin C., Raynal J.,Andrè N., Bonneau A., and Westercamp P., 2001 :Combining Controlled atmosphere storage and ethanol vapour to control superficial scald on apple. Hort Science 36) or combined with oxygen stress (Gharhamani F., Scott K.J., and Holmes R., 2000, Effects of alcohol vapours and oxygen stress on superficial scald and red colour of stored Delicious apples. Hort Science 35).
The concept of dynamic gas stress treatments carried out keeping under control the ethanol concentration in the fruit pulp has found practical application on a wide scale, thanks to technology (storage room construction, equipment, software) which enable the realization and control of the CA rooms with very low gas concentrations especially O2 and CO2 and thanks to a simple and rapid method for checking the dosage of ethanol in the fruits.
Correct sampling methods and uniformity of the apples placed in L.O.S. storage rooms, allow for optimal results to be obtained in the control of superficial scald and brown core physiological disorders , as well as in maintaining high standards of organoleptical and commercial qualities for the Consumers.
Special thanks to Mr Pio de Concini and Mr Moreno Sabadini, technicians in charge of postharvest activities (refrigeration and CA), respectively at AVN Cooperative of Casez (Melinda group) and Salvi Group Ferrara, for their professional and precious collaboration given to the working group.
Literature cited :
Chervin C., Raynal J.,Andrè N., Bonneau A., and Westercamp P., 2001 :Combining Controlled atmosphere storage and ethanol vapors to control superficial scald on apple. Hort Science 36.
Golding J.B., Zhenyong W., and David R.Dilley: Role of Alcohol dehydrogenase in preventing superficial scald in apples .8°Int.CA Conference Acta Horticolture 600, 2003.
Gharhamani F., Scott K.J., and Holmes R., 2000,Effects of alcohol vapors and oxygen stress on superficial scald and red color of stored Delicious apples. Hort Science 35).
Little, C.R.,Faragher, J.D., Taylor H.S., 1982. Effects of initial low oxygen stress treatments in low oxygen modified atmosphere storage of Granny Smith apples: J. Amer Soc.Hort Sci. 107, 320-323.
Mattè P, Fadanelli L, Chistè C, Zeni F, Buglia L. Boschetti A ILOS + ULO AS A PRACTICAL TECHNOLOGY FOR APPLES' SCALD PREVENTION Acta Horticolture 5th International Postharvest Symposium Verona, Italy, June 6-11, 2004
Rizzolo, A., M. Vanoli, Visai C., and Fadanelli L., Ultra- low oxygen storage of “Golden Delicious” apples. Proc.Seventh International Controlled Atmosphere Research Conference. July. 1997 Davis CA ,USA
Truter, A.B. , Combrink, J.C. ,Burger, S.A. 1994. Control of superficial scald in Granny Smith apples by ultra-low levels of oxygen as an alternative to diphenylamine. J. Hort.Sci. 69, 581-587.
Van der Merwe J.A., Combrink J.C., Calitz F.J., 2001. Effect of Controlled Atmosphere Storage(CA) after initial Low Oxygen Stress Treatment (ILOS) on superficial scald development on South African-grown Granny Smith and Topred Apples. VIII Int. Controlled Atmosphere Research Conference 8/13-07-2001 Rotterdam Holland.
ILOS + ULO AS A PRACTICAL TECHNOLOGY FOR APPLES' SCALD PREVENTION
Mattè P., Buglia L.,
Fruit Control Equipments, via R. Luxemburg 55-20085 Locate di Triulzi– Italy
Fadanelli L., Chistè C., Zeni F.
I.A.S.M.A. Istituto Agrario San Michele all’Adige, U.O. Frutticoltura-Conservazione, via E. Mach 1-38010 San Michele all’Adige-Italy
Istituto di Fotonica e Nanotecnologie,CNR-ITC,Trento,Italy
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.
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.
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).
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.
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.
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.
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).
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.
Alavoine, F., Crochon, M., Fady, C., Fallot J., Moras P. and Pech J. 1988. La qualitè gustative des fruits-Bases physiologiques ef methodes pratiques d’ analyse.Ed. CEMAGREF-DICOVA, 92160 Antony, France.
Boschetti, A., Collini, A., Fadanelli L., Groot T., Mon G., Raimondi S. and Iannotta S. 2003. PTR-MS studies to assess and monitor fruit qualità during preservation. I° Int. Conf. On Proton Transfer Reaction –Mass Spectrometry and its Applications.Innsbruck 18/23 -01-2003
Bramlage, W. and Meir S., 1989 . Potential method for predicting susceptibility of apples to superficial scald. ACTA Horticulturae 258: 397-401.
Little, C.R., Faragher, J.D. and Taylor H.S. 1982. Effects of initial low oxigen stress treatments in low oxygen modified atmosphere storage of Granny Smith apples: J. Amer Soc.Hort Sci. 107: 320-323.
Lopez, M.L., Lavilla, M.T., Riba, M. and Vendrell, M. 1998a.Comparison of volatile compounds in two seasons in apples :Golden Delicious and Granny Smith. J. Food Qual. 21: 155-166.
Lopez, M.L., Lavilla,.T., Recasens, L., Riba, M. and Vendrell, M. 1998b. Influence of different Oxygen and Carbon Dioxide Concentrations during Storage on Production of Volatile Compounds by Starking Delicious Apples. J. Agric.Food Chem. 46: 634-643.
Mattè P.and Buglia L. 1997. New engineering development of U.L.O. technology in Italy – Commercial ad research applications. Proc.Seventh International Controlled Atmosphere Research Conference. July. 1997 Davis CA ,USA.
Rizzolo, A., M. Vanoli, Visai C., and Fadanelli L. 1997. Ultra- low oxygen storage of “Golden Delicious” apples. Proc.Seventh International Controlled Atmosphere Research Conference. July. 1997 Davis CA ,USA.
Rossier, J., Pfammater, W. and Aerny, J. 1998. Determination de la qualitè interne des pommes à l’ aide du laboratoire d’ analyse “Pimprenelle”. Revue Suisse de Viticulture, Arboriculture et Horticulture. 30: 247-252.
Truter, A.B., Combrink, J.C. and Burger, S.A. 1994. Control of superficial scald in Granny Smith apples bY ultra-low levels of oxygen as an alternative to diphenylamine. J. Hort.Sci. 69: 581-587.
Van der Merwe, J.A., Combrink, J.C. and Calitz, F.J. 2001. Effect of Controlled Atmosphere Storage(CA) after initial Low Oxigen Stress Tratment (ILOS) on superficial scald development on South African-grown Granny Smith and Topred Apples.VIII Int. Controlled Atmosphere Research Conference 8/13-07-2001 Rotterdam Holland.
Visai, C., Vanoli, M. and Fadanelli, L. 1997. Influence of controlled atmosphere on quality and scald development in “Stark Delicious” apples. Proc.Seventh International Controlled Atmosphere Research Conference. July. Davis CA ,USA.
Wang, Z. and Dilley, D.R. 2000. Initial low oxygen stress control superficial scald of apples.Postharvest Biol. Tech. 18: 201-213.
Zanella, A. and Werth, E., 2004. Vergleich der Analyse chimico-phisikalicher qualitatsparameter von Apfeln mittels eines automatischen Messgerates („Pimprenelle“) mit konventioneller Analitik. Laimburg Journal 1: 51-57.
Paper presented at ”POSTHARVEST2004”, the 5th International Postharvest Symposium, 6th -11th June 2004 Verona –Italy-
1. PLANT ENGINEERING FOR THE STORAGE OF DESSERT GRAPES WITH INDIRECT REFRIGERATION USING PLASTIC TENTS
(BONOMI SYSTEM TECHNOLOGIES, TRADE MARK AQUIRED BY FRUIT CONTROL S.R.L. IN 1988)
( ING F. BONOMI )
The author, with reference to the research carried out by CRIOF of Bologna on the refrigerated storage of dessert grapes, lists the conditions in which it is possible to obtain good storage results. The techical solutions adopted in industrial plants are illustrated; precisely: indirect refrigeration of the stored product, periodic sulphuration , absorption of SO2 in closed cycle,with brief mentions of the type of apparatus and materials used. The Author also mentions the use of plants for disinfestation and pre-refrigeration for transport.
The operators in this field agree that there is a considerable interest in having at disposition, for sale on the market, several varaieties of dessert grapes for a period of 2-3 months, and above all to be able to offer the product in coincidence with the Christmas period and even after. While in other countries the refrigerated storage of grapes is applied with interesting economic results, in Italy it generally represents an intervention of the duration of 10-20 days which is resorted to so as to lighten the markets during the harvest period. Also in this case, the technical results are poor, given the empiricism with which it differentiates from the other fruits normally stored.
The point about the technique for cold storage of grapes has been made in two notes published by CRIOF in 1968 and 1969 (1), (2). n these two papers the Authors, taking up the argument already dealt with in 1962 by Prof. G.C.Pratella (3), refer on the results of research carried out at CRIOF of Bologna since 1963 until today and mention new constructive techniques for grape storage plants, techniques which, after the experimental phase referred to by the authors, have been applied in industrial plants where hundreds of tons of fresh grapes of the most requested cultivars in have been stored over the last years. In the aforementioned notes the conditions for good dessert grape storage are clearly stated , for periods of 2-3 months and more for some varieties, precisely: temperature -1 - 0ï¿½ C; relative humidity 95% and over ; periodic sulphuration with treatments at various concentrations. In order to obtain these conditions certain technical problems needed to be overcome and which only in the last few years have been resolved. It is known that, storing grapes at 0ï¿½ C, with relative humidity of 80 -85% (good for normal refrigeration plants), there is consistent loss of water due to transpiration - which causes withering and the successive browning of the grape stalks while the grapes gradually lose turgidity. It is therefore essential to realize and maintain relative humidity at about 95% or more in the ambient in which the grapes are stored, a condition that is very difficult to reach with the normal industrial refrigerators built for the conservation of fruit in general.
Periodic sulphuration treatment poses other technical problems, such as, for example, the aggressiveness of SO2 on metals in general but particularly the ferrous type, of which most of the apparatus placed in the cold storage cells are made. The susceptibility of grapes to the damage caused by sulphurous anhydride imposes the utmost precision in dosing the fumigant used for germicidal purposes, dosage which is variable over time (larger doses at the beginning of storage and then reduced during) and also depending on the sensitivity of the different cultivar. The exposure times of the product to sulphurous anhydride are short (20-30 mins.), the removal of the fumigant from the ambient must also be rapid and the residues must be quickly reduced to only a few parts per million in volume to avoid possible damage due to the long exposure even at low concentrations. On the other hand the necessity to keep a constant hygrometric grade of 95% in the storage ambient excludes the practice of sulphurous acid removal using atmospheric air. This practice brings about sensitive variations in the hygrometric grade of the ambient (reduction of relative humidity) and therefore causes a lack of water for transpiration from the fruit to the ambient to reconstruct the balance between vapour tension of the gases contained in the intercellular spaces of he fruit and the vapour tension of the atmosphere in the storage ambient. This consideration leads to further examination of the problem of SO2 absorption used for disinfestation in closed cycle trying to realize absorption without modifying minimally in the negative sense the hygrometric grade of the ambient. All of these considerations, which emerged, as already cited, during the course of a long experiment conducted by CRIOF the university of Bologna, have been the basis of studies which have brought about the most ideal technical solutions. With regard to the most important condition, maintainence of humidity at about 95%, this problem has been resolved with the use of indirect refrigeration, keeping the grapes inside plastic wrappers that ar impermeable to gases, placed inside the normal refrigeration cells.
In normal refrigeration plants the problem of the hygrometric grade is rarely brilliantly solved, and the effects are the phenomen of weight loss and depreciation of the product, as all operators know. In fact, when a cold storage cell is in temperature regimen, when a thermal balance has been created and which is imagined to be existent in the mass of the stored product, each time that the refrigeration plant starts up and therefore the air contained in the cell circulates towards the cooler, normally a layer of ice forms on the cold surface of the evaporator (pipes, fins); 1 millimeter of ice on each square meter of cooling surface represents about one litre of water that is taken fron the ambient. This phenomen is even more evident during the pull - down phase.
Considering that inside the cold store a balance will be created between the vapour tension of the air surrounding the fruit and the vapour tension existent in intercellular spaces of the same fruits, each time that a certain quantity of vapour condenses on the cold surface of the evaporator the same quantity is immediately ceded by the fruits to the ambient. In order to have an idea of the amount of water lost by the fruits due to this phenomen, it is to be noted that an average evaporator with a surface of 400 sq.m. is capable of subtracting about 400 litres of water from the fruits per mm. of ice that forms on the surface of the cooler. Obviously any relative humidity measurement apparatus placed inside the cold storage cell, ends up measuring the effect that derives from this mechanism of the removal of water vapour from the ambient (action of the evaporators) and the contemporaneous transfer of an equal amount of water vapour from the fruits. For this fundamental reason, when a hygrometric grade of 90% is measured inside the cold store, a condition considered optimal, there is still a loss of weight from the fruit.
To reduce the effects of these phenomen, particular devices are used for the distribution of the refrigerant liquid to the evaporators. Theoretically one of the most valid contrivances is that of increasing the cooling surfaces so as to reduce thermic shock, equal to the frigorie delivered, between the circulating air temperature and that of the finned pipes, so as to contain the condensation phenomen. This device, however, is costly and rarely realized in a rational manner. This is the situation existant today in the construction of refrigeration plants, a situation which is determined not so much by a lack of good will and capability of the builders as by certain commercial factors which often deteriorate during negotiations of the plant sale. The solution of indirect refrigeration represents a new criteria for the refrigeration plants destined for long term storage of hortofloricultural products and eliminates the inconveniences due to the lack of the hygrometric grade. With this technique the products are stored within the plastic wrappers placed inside normal cold-stores and the refrigeration of the product happens indirectly through the walls of the wrappers and not by effect of direct ventilation onto the fruit.
The fundamental characteristic of the system is in the fact that a very high hygrometric grade may be maintained (over 95%) in the ambient in which the produce is stored because the refrigeration of the fruit happens over a wide surface (walls and ceiling of the wrapper) with a low thermic fall (ie.temperature of cold store + 1ï¿½C and temperature stored produce +2ï¿½C) and without loss f atmospheric water vapour contained inside the wrapper and at contact with the products. Using the indirect refrigeration system, with regards to the hygrometric grade, one may prescind from the performance of the refrigeration system, because, in fact, inside the plastic wrapper relative humidity may be measured at 92 - 95%, whereas outside the wrapper this normally reaches only 50 - 60% or less. It is implicit that with such a performance it has been possible to widen controlled atmosphere storage to species up to now stored rarely or not at all, such as vegetables, flowers and grapes. Another fundamental characteristic of this system resolves one of the most important problems for longterm storage of grapes represented by the necessity of placing the product in optimal storage conditions the least amount of time possible after picking. The large capacity cold stores, that are the least expensive from the installation point of view, as evident, are the least suited for this. Using the indirect refrigeration system, it is possible to take advantage of a refrigerated ambient, even of large capacity, for the storage of grapes, dividing up the refrigerated space in several plastic wrappers, with the advantage of storing, for long term conservation, grapes of different cultivars harvested in different periods, at the same thermic regimen, and reaching in a short time after picking the optimal storage conditions, including the sulphuration treatment, for each lot of grapes in each wrapper. The division of the large refrigerated space into several cells (wrappers) of small capacity also gives the possibility of lightening the loading and unloading operations of the cells with regard to both the harvest period of the varieties and the market requests during merchandising of the products, with much lower costs in respect to the probable costs if smaller capacity cells had been built.
Many materials had been examined for the realisation of indirect refrigeration which, in the specific case of grape storage, must meet certain requisites: gas impermeability, sufficient mechanical resistence, imperviousness to the effects of SO2 gas, easy assembly, sufficiently high heat transmission coefficient and low cost. The choice, after numerous experiments, fell upon plastified polyester material. This material, used for the realization of the wrappers, have completely answered to all the requirements and five years of industrial plant construction have confermed the validity of the solution. In fact, the use of plastic wrappers, inalterable against the action of SO2 gas, resolves the other big problem of the corrosion of large part of the apparatus placed inside the refrigerated cells. Using indirect refrigeration, the cooling apparatus with their relative ventilators, thermostats etc. are placed outside the actual staorage ambient (represented by the inside of the tends) where the grapes are placed and where sulphuration is carried out. The gas impermeability of the plastic material allows precise dosage of the SO2 gas and also helps maintain constant a constant gas concentrationduring the sulphuration operation. These conditions are indispensable for assuring the effectiveness of the treatment and to surely avoid damage to the grapes caused by SO2.
The operation of SO2 dosage, in order to give the necessary guarantees, is achieved by measuring liquid sulphurous anhydride with a special apparatus. The desired quantity of liquid SO2 is gassified with a hot water vaporizer, specifically studied to guarantee the inlet into cell (tend) of the SO2 gas and avoid any type of SO2 gas condensation forming on the stored grapes. Groups of ventilators, opportunely protected against the sulphurous anhydride, are provided inside the wrapper, these make the atmospheric air, within the wrapper, circulate in closed cycle in the grape mass so favouring the thermal exchange between the refrigerated ambient outside the wrapper and that within and therefore avoiding the creation of differences in temperature in the various points of the mass of the stored product. The action of these groups of ventilators also allows the uniform distribution of SO2 gas in the grape mass, while in the meantime maintaining a homogenous concentration of the gas for the whole period of sulphuration. The problem of removing the SO2 from the grape storage ambient has been resolved by employment of a closed cycle absorber using water, this omits communication between the storage ambient and the outside. The apparatus consists of a tower connected to the wrapper using pipes of a suitable diameter. A low power centrifugal pump, installed at the base of the tower, provides the closed cycle circulation in the tower of the atmosphere containing sulphurous anhydride drawn from the cell in contro-flow with water coming from the mains which, in turn,descends the tower through an inert mass. The precise control of the water delivery is possible due to the flowmeter inserted in the distribution pipe on which a a special regulation valve is foreseen. The whole apparatus, in the parts at contact with the sulphurous anhydride, is protected by a special paint, the base of which is a synthetic elastomer impervious to the action of sulphurous anhydride. The absorption yield of this apparatus is such that it guarantees the total removal of sulphurous anhydride from the ambient,without the use of special chemical absorbents which needto be substituted when reaching complete saturation. The simplicity and functional safety are the fundamental characteristics of this machine, given the elementary principle on which sulphurous anhydride removal is based (physical absorption). Furthermore, the use of water in an apparatus in closed cycle consents enrichment of the ambient of water vapour and therefore maintains a high hygrometric grade (tending to saturation) which is required in order to avoid weight loss and depreciation of the stored product. The SO2 concentration is kept under control during both the sulphuration treatment (control of dosage) and after the absorption of the gas (control of residues) by a special immediate analysis apparatus (sensitivity up to 20 p.p.m.).
DISINFECTION TREATMENTS AND PRE-REFRIGERATION
An interesting note was surveyed while using these plants over the last four years in Italy, France, Portugal and Latin America; (1) the cells and relative apparatus may be used for preventive disinfection for transport, disinfection accompanied by pre-refrigeration. In fact, for the commercialization of grapes the problem is that of getting the product onto to the market in the best possible conditions given the distance from the production centres and the rate at which the product deteriorates. The development of Botrytis during the time that the product is on the means of transport and at the sorting stations can compromise the results of merchandising. For this reason normally, in this type of plant destined for long term grape storage, one or two cells are destined for disinfection treatments and pre-refrigeration for transport. These cells are used up until the end of the grape harvest and then loaded with produce from the last picking for storage. The disinfection treatments and pre-refrieration for transport are pratically carried out during the night by sulphuration of the produce placed in the indirect refrigeration cells, this treatment lasts about 20 minutes. Afterwards, de-sulphuration of the ambient is made and this treatment happens contemporaneously with the indirect refrigeration of the product so as to obtain a lowering of the temperature in the mass to 7-8 ï¿½C without loss of water from the grapes. The product, refrigerated and disinfected, is put onto the consumer market, having avoided the risk of developing Botrytis, at least for the period in which sale of the produce is effectuated. (1) - In these plants the following cultivar were stored : Alphonse Lavallèe, Italia, Cardinal,Regina,Chasselas, Dattier, Servant, Rosaky, Donna Maria.
ULTRA-LOW OXYGEN STORAGE of APPLES cv 'Golden Delicious'
Anna Rizzolo, Maristella Vanoli (1), Costanza Visai (1), Livio Fadanelli (2)
Istituto Sperimentale per la Valorizzazione Tecnologica dei Prodotti Agricoli (I.V.T.P.A.)
via Venezian, 26, 20133 Milano, Italy (1)
Istituto di Coltivazioni Arboree, Università degli Studi, via Celoria,2, 20133 Milano, Italy (2)
Istituto Agrario di S.Michele a/A, Centro Sperimentale, via Mach, 1, S.Michele a/A (TN), Italy
In Italy, "Golden Delicious" apples are stored in controlled atmosphere (CA) until May; but, CA apples suffer from a lack of flavour at the end of storage. Improved fruit quality and extended storage life can be achieved by storing apples in ultra-low oxygen (ULO) atmosphere. The aim of this work is to study the feasability of ULO storage for 'Golden Delicious' apples, which is not a well-established technique in Italy for this cultivar. Apples were harvested at the commercial maturity in Val di Non Valley (600 m a.s.l.) and were stored in 3500 q commercial storage rooms at 1°C (R.H. 97%) in CA (1.5 % O2; 2.0 % CO2) and in ULO (0.9% O2; 1.2% CO2) for seven months. At harvest and at the end of storage, apples were analysed for flesh firmness, color (L*, a*, b*), titratable acidity, soluble solids, sugars and organic acids by HPLC, and ethylene and volatile composition (headspace cGC on intact fruits) during ripening at 20°C. Quality parameters soon after removal from CA and ULO storage rooms, defined ULO apples as less ripe than CA fruits; total volatiles and volatile compositions were similar for the two storage modes. With the post-storage ripening, ULO stored apples produced more total volatiles than CA; ULO atmosphere delayed maximum ethylene and volatile productions, as well as the development of selected volatiles. At tasting, ULO apples were firmer, more juicy and sour and had a good distinct flavour. key words: Golden Delicious apples, ULO, quality parameters, volatile composition.
Controlled atmosphere (CA) storage is a well-established technique used to extend the storage life of apples (Gorini, 1987). Firmness, acidity, color and other quality parameters are maintained in CA, whereas the ability of apples to produce volatile compounds is suppressed during and after CA storage. The aroma suppression depends on both the atmosphere composition and the length of storage time (Yahia, 1994). Improved fruit quality and extended storage life are achieved by lowering the oxygen concentration to less than 1%, i.e. storing in ultra-low oxygen (ULO) atmosphere (Brackmann et al., 1993). The lower limit for oxygen, at which no accumulation of anaerobic respiration products (acetaldehyde, ethanol, lactate) occurs, .is connected to the cultivar, growing area conditions and climate (Blanpied and Jozwiak, 1993; Meheriuk, 1993). In Italy ULO storage is used to reduce physiological disorders in Red Delicious and Granny Smith apples, but it is not widely used for Golden Delicious apples (Eccher Zerbini et al., 1996; Nardin, 1994). Therefore, the aim of this work is to study the feasability of ULO storage for 'Golden Delicious' apples in Italy, by evaluating physical and chemical characteristics of stored fruits and ethylene and volatile composition during ripening at ambient temperature.
MATERIALS AND METHODS
Apples (Malus domestica Borkh., cv 'Golden Delicious') from 11 year old trees, grafted on M9 rootstock were harvested on 6th october 1994 at the commercial maturity in Val di Non Valley (600 m a.s.l.) and stored in 3500 q commercial storage rooms at 1°C (RH 97 %) in CA (1.5 % O2; 2.0 % CO2) and in ULO (0.9 % O2; 1.2 % CO2) for seven months. The storage conditions were obtained pulling down oxygen from 21% to 5% over 8-10 hours. At harvest and at the end of storage, 30 apples were analysed for flesh firmness (11 mm plunger), color (in reflectance with Minolta Chroma-Meter- CR-300, L*, a*, b*), titratable acidity (TA) and soluble solids (SS). Then, apples were pooled into six replications of five fruits and each replication was analysed for sugar (sucrose, glucose, fructose, sorbitol) and organic acid (malic, citric, succinic and quinic acids) composition by HPLC on the aqueous extract from the pulp (Forni et al., 1992; Vanoli et al., 1995). Other 3 replications of 8 fruits were put into glass flow-through systems, and analysed for ethylene (Eccher Zerbini et al., 1996) and volatile compounds during the ripening at 20°C by dynamic headspace/capillary gas chromatography on intact fruits (Rizzolo et al., 1992). At the end of the post-storage ripening, fruits from each replication were analysed for flesh firmness, TA, SS and, after being pooled into two groups of 4 fruits, for sugar and organic acid compositions. Data were submitted to analysis of variance and the means compared by Tukey test.
At harvest Quality parameters and organic acid and sugar compositions of 'Golden Delicious' apples at harvest are shown in Tables 1 and 2, respectively. Ethylene and total volatile evolutions during the fifteen-day postharvest ripening at 20°C (Figure 1) had a maximum between 11 and 13 days, reaching 53 mL L-1 kg-1 h-1 of ethylene and 41.5 mg kg-1 h-1 for total volatiles. Maximum production of volatiles coincided with maximum production of butyl acetate (20.73 mg kg-1 h-1), hexyl butanoate (0.31 mg kg-1 h-1), 2-methyl-propyl hexanoate (0.73 mg kg-1 h-1), hexanol (0.35 mg kg-1 h-1), hexyl propanoate (0.50 mg kg-1 h-1), hexyl acetate (7.88 mg kg-1 h-1), butyl butanoate (1.05 mg kg-1 h-1), pentyl acetate (0.36 mg kg-1 h-1) and butanol (2.88 mg kg-1 h-1).
After CA and ULO storage At the end of storage there were differences between the fruit stored in the two atmospheres (Table 3): ULO apples had higher L* value, were firmer and contained lower quantities of succinc acid, citric acid, malic acid, sorbitol, fructose and glucose.CA apples developed similar amounts of total volatiles to ULO fruits (CA: 0.55 mg kg-1 h-1; ULO: 0.73 mg kg-1 h-1), having similar compositions, with hexyl acetate and butyl acetate the main compounds.
With the post-storage ripening (Table 3), citric acid, malic acid, quinic acid, fructose, glucose, sucrose, L*, a* and b* increased, while TA and firmness decreased. Only for firmness the interaction between storage atmosphere and days of post-storage ripening was significative (F ratio = 5.066; P< 0.05 %). After eleven days of post-storage ripening, ULO apples showed a firmness not statistically different from that of CA apples just removed from storage rooms; moreover, at the end of post-storage ripening the firmness of the apples from the two storage modes was not different. Just as at harvest, total volatile and ethylene evolution coincided (Figure 2): ULO apples had maxima productions of ethylene and volatiles at the end of post-storage ripening, whereas CA apples after four days. With ripening, ULO apples developed more total volatiles than CA fruits (CA: 3.77 mg kg-1 h-1; ULO: 6.61 mg kg-1 h-1). ULO storage delayed the production of propyl acetate, propyl butanoate and butanol during the post-storage ripening. At the end of post-storage ripening (Table 4), ULO apples produced higher amounts of hexyl butanoate, 2-methyl-propyl hexanoate and hexyl propanoate than CA apples. A consumer test carried out after 7 days of post-storage ripening , whose results are discussed by Mattè (1997), defined ULO apples firmer, more juicy and sour and with a good distinct flavour.
Storage atmosphere influenced quality characteristics, ethylene evolution and volatile composition of 'Golden Delicious' stored for seven months. Lowering O2 level from 1.5 % of CA storage to 0.9 % of ULO storage, there was a delay in the maturation process of apples; in fact after removal from storage rooms, quality parameters defined ULO apples as less ripe than CA fruits, according to Greene et al. (1993) and DeEll and Prange (1993). Our work confirmed that CA storage suppresses volatile production. During post-harvest ripening 'Golden Delicious' apples produced 41 mg kg-1 h-1 of total volatiles compared to 6 and 3 mg kg-1 h-1 for ULO and CA apples, respectively. Moreover, the suppression of volatiles was particularly evident for acetate esters, as found by Brackmann et al. (1993) and Harb et al. (1994). The composition of storage atmosphere had no effect on total volatile production and volatile compound composition in apples just removed from storage rooms, but it had a strong influence on post-storage ripening. With the post-storage ripening, ULO atmosphere delayed maximum ethylene and volatile compound production, as well as the development of selected volatiles (propyl acetate, propyl butanoate and butanol); however, at the end of post-storage ripening, ULO apples developed more volatile substances than CA ones Our results enphasize the feasability of ULO storage for 'Golden Delicious' apples for the following reasons: higher firmness and lower organic acid content at the end of storage, and greater ability of producing volatiles with post-storage ripening.
(Paper presented at the International Conference on Controlled Atmosphere Davis
- U.S.A. - 1997)
CA AT THE APPOINTMENT WITH THE THIRD MILLENNIUM
Paper presented at the " Fruit growing symposium and demostration" for the opening Cerimony of the new facilities at Ujfeherto Research Center-Hungary, June 22th 1999
Fruit Control Equipments srl
Fruit Control Equipment ,an italian company, leader in the field of controlled atmosphere technology. It is owner since 1989 of the prestigeous Bonomi's trade marks and pursues a qualified research programme for improving CA technology. Throughout a network of companies, each one qualified a specific area for manufacturing parts for the systems, FCE controls all the passages of the various processes and also offers turn- key solutions for their CA projects to the Customers when required. FCE operates in Italy and in the majority of apple-producing Countries in the world . Apples in fact still represent up to 70% of CA investments world wide, followed by pears and kiwifruit.
Our Company has always proposed and introduced new storage methods as well as classic CA we also propose ULO ( Ultra Low Oxigen ), LECA ( Low Ethylene Controlled Atmosphere), ILOS ( Initial Low Oxygen Stress ), RCA ( Rapid CA ) and DCA ( Dynamic CA ). The interrelationship between FCE, Research centers , Univerity Institutes specializing in post-harvest is indicated as one of the best and most practical ways to reach positive resuls for fruit growers, implementing formation and information together with training in fruit storage. It is important to establish world wide simple, clear and appliable standards for fruit storage technology. FCE is also involved in suggesting the correct method concearning the CA applications. Technology is evolving very quickly, with specific regards to electronics and official standards must be established to be applied in: CO2 adsorbing plants, O2 pull down systems and pull-down time, C2H4 ( ethylene ) control, Analysing systems, computerized controls etc. FCE is leader in the market of the single units for CO2 adsorption. The solution was conceived by Bonomi in the late 70's and has been improved by FCE and updated with PLC technology inside each unit.
Nowadays FCE produces a wide range of CO2 adsorbers for differente room sizes and of course fruit varieties with different respiratory rates. Full automatic devices ( with analysers and microprocessors on board ) can be adopted for special applications, including regeneration with nitrogen for the off-limits of the gas concentrations. Concearning oxygen pull-down, FCE has been always insisted on pushing the market towards short term solutions, which means the installation ( one per plant ) of an inert gas generator ( now mainly nitrogen generators ). The shorter the amount of time that passes from harvesting date to when the product reaches the final CA storage conditions, the better it is for the apples' quality and the longer the shelf-life will be on the market, with the best commercial results for the fruit growers and the satisfaction of the customer. We sometimes suggest installing nitrogen generators to pull down the oxygen ( from 21% to 5-6% ) in less than 24 hours. Regarding ethylene control, FCE applies with great success LECA ( Low Ethylene CA ) solutions for all fruits with high sensitivity to this gas. Particularly interesting applications are for kiwifruit, but now and in the future will be used even more for some apples varieties like Fuji, Gala, Elstar, for maintaining freshness, acidity and firmness longer on the market. What about the control systems ? Here is the fantastic area for developing the most advanced control systems. FCE has been proposing over the last 12 months a new application for its GAC5000 computerized system, which will be improved further during the near future. Our appointment with the Y2K will be based on a Supervised Dynamic Atmosphere ( SDA ) which means integration of automation and human resources for better surveillance on the life and of course the quality of the stored fruits.
The concept is to take care of the fruits from the point of view of respiration rate, firmness, brix values and according to these values apply the best O2 and Co2 concentrations. We will be testing new probes for ethylene and alcohols, which could be applied inside each storage room and report important informations to the computer system for the Dynamic Atmosphere to be adopted. Man will always be the supervisor of this information and will check manually from time to time some parameters to verify the storage process. In the following years of next millenium there will be a lot to do together with the consumers in order to establish the preferable characteristics and taste of the fruits in the different period of the year ( i.e. yellow, red, green, acid, juicy,crispy etc ). Non distructive methods are now under testing on line in sorting machines to check by laser the quality. It will be possible in short time to calibrate probably the fruits under their intrinsec quality and of course the fruit growers could be also payed according to new parameters. According to the panel tests it is possible to verify also the best storage conditions to apply in order to keep fruit quality as required by the consumers. The picking dates windows for the fruit will be the main job to do, out of the most important one belonging to the fruit growers , which is to produce quality and not quantity. The distribution systems ( large supernmarket chanes ) will pay more attention to all these developments and hopefully improve their distribution areas for the fruit and vegetables. FCE will be also working for these purposes , with friendly environmental solutions.