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High-CO2 controlled atmospheres reduce decay incidence in Thompson Seedless and Red Globe table grapes
Postharvest Biology and Technology 29 (2003) 177 /182 www.elsevier.com/locate/postharvbio
High-CO2 controlled atmospheres reduce decay incidence in Thompson Seedless and Red Globe table grapes Julio Retamales a,b,*, Bruno G. Defilippi a,1, Marcela Arias b, Paula Castillo a, Daniel Manrı´quez a a
Institute for Agricultural Research, La Platina Experimental Station, Casilla 439/3, Santiago, Chile b Faculty of Agricultural Sciences, Universidad de Chile, Santiago, Chile Received 7 February 2002; accepted 20 January 2003
Abstract The efficacy of CO2-enriched atmospheres on decay control of organically-grown ‘Thompson Seedless’ and ‘Red Globe’ table grapes was evaluated during storage at 0 8C. Grapes in the treatments with controlled atmosphere (CA) were inoculated with a Botrytis cinerea culture (10 000 conidia per ml) at the beginning of the experiments. Control treatments were stored in air with or without SO2-generating metabisulphite pads and either with or without Botrytis inoculation. Fruit quality attributes including soluble solids, titratable acidity, incidence of decay, stalk and pedicel appearance were measured on removal from 0 8C and during subsequent shelf-life at 18 /20 8C. CAs with CO2 at 15% or higher resulted in as good control of Botrytis as using metabisulphite pads. Stalks and pedicels were greener when metabisulphite pads were included. # 2003 Elsevier B.V. All rights reserved. Keywords: Botrytis rot; SO2 replacement; Rachis appearance; Organic
1. Introduction Some consumers are concerned about fruit being treated with pre- and postharvest chemicals. Thus, demand for organic fruits in some markets has increased, encouraging organic cultivation of fruit crops in several countries. Unfortunately,
* Corresponding author. Tel.: /56-2-757-5161; fax: /56-2541-7667. E-mail address: [email protected] (J. Retamales). 1 Present address: Postharvest Laboratory, Pomology Department, University of California Davis, Davis, CA, USA.
acceptable nonchemical postharvest decay control treatments are not yet available. Infection with grey mold caused by Botrytis cinerea is the main factor limiting prolonged storage of table grapes. Initial SO2 fumigation and/or use of SO2-releasing metabisulphite pads during transport (Winkler et al., 1974) are presently used for grapes being shipped to export markets. However, use of SO2 is not permitted for organic produce and, thus, alternative treatments to SO2-fumigation and metabisulphite pads must be developed for fruit destined for export markets. Excessive SO2 concentrations during storage can cause bleaching, which is especially detrimental in
0925-5214/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0925-5214(03)00038-3
178
J. Retamales et al. / Postharvest Biology and Technology 29 (2003) 177 /182
colored table grape varieties (Winkler et al., 1974). Therefore, ‘Red Globe’, the second most important variety in Chile, was included in our trials. Further, it is suspected that some consumers develop allergic reactions to SO2 residues left on the fruit on consumption (Berry and Aked, 1997). Thus, exclusion of SO2 in the postharvest handling of table grapes is not only important for organic fruit, but also for conventionally-grown grapes. Limited research has been conducted using controlled atmospheres (CA) during postharvest handling of table grapes. ‘Thompson Seedless’ grapes tolerate high levels of CO2 for up to 2 weeks at 0 8C (Ahumada et al., 1996; Mitcham et al., 1997) and good control of Botrytis rot has been achieved using high CO2 levels (Berry and Aked, 1997). This indicates that there may be a potential for CA to replace SO2 for controlling decay in table grapes. In this study we investigated the effect of CO2-enriched CA storage on the postharvest behavior of both organic ‘Thompson Seedless’ and ‘Red Globe’ table grapes.
that the inoculum had ready points of entry. Source of SO2 consisted of metabisulphite pads (Fresca, Quimetal, containing 7 g of metabisulphite), that were individually placed as required on the top of the grapes within boxes before they were placed at 0 8C until evaluation.
2. Material and methods
Fruit quality was evaluated immediately after removal from 0 8C after 20 and 40 days for ‘Thompson Seedless’ and after 45 days for ‘Red Globe’ grapes, followed in each case by evaluations after 4 days shelf life at 18 /20 8C. Soluble solids content (SSC) was measured in ten indivi-
2.1. Plant material Organically-grown ‘Thompson Seedless’ grapes, as commercially defined for European markets, were harvested (19.2% soluble solids and 0.71% tartaric acid) from a vineyard located in the Rengo area (120 km south of Santiago). ‘Red Globe’ grapes (19.0% soluble solids and 0.41% tartaric acid) were harvested from a vineyard in ‘transition to organic’ production located in the San Vicente area (140 km south of Santiago). Immediately after harvest, grapes were packed into 5 kg cartons in the same vineyard without being subjected to SO2 fumigation, and cooled to 2 8C with forced air. Cartons were transported to the Postharvest Laboratory, La Platina Experimental Station, Institute of Agricultural Research (INIA), in Santiago. Where required, grapes were inoculated (10 000 conidia per ml) with a culture of B. cinerea, isolated from grapes, by puncturing one grape in each bunch in the box with a tool immerged in the culture solution and having three tips, ensuring
2.2. Treatments CA-treatments used are shown in Table 1. Fruit for air and CA-treatments were maintained in airtight, 140 l sealed plastic containers at 0 8C. Gas concentrations were attained initially by adding nitrogen to containers having four fruit cartons each and then adding CO2 to the desired concentration. O2 and CO2 concentrations were measured daily using a MAPTest 3000G gas analyzer (Hitech Instruments, Luton, England) and adjusted as needed to maintain them within9/1.0% of the desired concentrations. 2.3. Quality evaluations
Table 1 Description of the treatments used in ‘Thompson Seedless’ and ‘Red Globe’ grapes Treatments
Gas levels (%)
Description
CO2 O2 (1) Air, inoc (2) Air/pad, inoc (3) Air
0 0 0
(4) Air/pad (5) CA 15/5 (CO2/O2) (6) CA 20/5 (CO2/O2) (7) CA 25/5 (CO2/O2) (8) CA 30/5 (CO2/O2) (9) CA 35/5 (CO2/O2) (10) CA 30/15 (CO2/ O2)
0 15 20 25 30 35 30
21 Inoculated, without pad 21 Inoculated, with pad 21 Non-inoculated, without pad 21 Non-inoculated, with pad 5 Inoculated, without pad 5 Inoculated, without pad 5 Inoculated, without pad 5 Inoculated, without pad 5 Inoculated, without pad 15 Inoculated, without pad
2.1 2.0 2.1 2.6 3.3 3.4 3.0 2.8
a a a b c c bc bc
2.0 1.2 2.0 1.3 1.4 1.8 2.0 2.1
a a a a a a a a
179
* Rachis appearance: 1, sound; 2, yellowish; 3, light brown; 4, brown.
48.8 d 8.2 ab 1.8 a 10.1 bc 21.6 bc 11.7 bc 10.3 bc 14.2 bc b ab ab ab a ab ab a 2.0 0.9 1.0 1.0 0.5 1.2 1.0 0.5 1.3 1.3 2.0 2.0 2.3 2.3 2.6 2.3 cd c a a a a a a 2.1 1.8 0.1 0.0 0.1 0.2 0.0 0.0
a a b b bc bc c bc
1.5 a 2.3 a 2.0 a 2.0 a
Rachis appearance* (1 / Additional water loss (% in 4) weight) Rotting (% in weight)
72.8 e 21.8 c 1.0 ab 0.9 ab 1.0 a 1.3 a 3.3 d 1.6 bc
(1) Air, inoc (2) Air/pad, inoc (3) Air (4) Air/pad (5) CA 15/5 (6) CA 20/5 (7) CA 25/5 (8) CA 30/5 (9) CA 35/5 (10) CA 30/15
3.1.1. Evaluation after 20 days at 0 8C Grapes kept at 0 8C for 20 days had the same SSC and TTA as at harvest (data not shown). Rotting incidence (Table 2) was lower in CAtreatments (T5 to T10) than in treatments with metabisulphite pads (T2 and T4). Those treatments lacking pads (T1 and T3) had the highest incidence of decay, whether or not they were inoculated, probably because of the presence of Botrytis inoculum in untreated grapes. No berry browning occurred in any treatment. Rachis appearance was negatively affected by CA-treatments. Water loss was minimal in all treatments as fruit was stored in closed containers and maintained in static conditions with only minor correc-
Rachis appearance* (1 / Water loss (% in 4) weight)
3.1. ‘Thompson Seedless’ grapes
Rotting (% in weight)
3. Results
After 20 days at 0 8C/4 days at 20 8C
Experimental design was completely randomized. The experimental unit was one bunch replicated four times within different boxes. Analysis of variance and Duncan’s test were used for analysis with a level of significance at P B/0.05.
After 20 days at 0 8C
2.4. Statistical analysis
Treatments
dual berries per bunch with a refractometer (Atago); and total titratable acidity (TTA) was determined on a composite sample of the same berries by using 0.1 N KOH up to a pH of 8.2 and expressed as percentage of tartaric acid. Water loss was measured by weighing individual bunches at the beginning of the experiments and again at each evaluation. Rachis appearance was rated as follows: (1) green; (2) yellow; (3) light brown; and (4) brown. On removal of ‘Red Globe’ grapes from 0 8C, damage caused by B. cinerea was rated as follows: (1) no Botrytis damage; (2) isolated berries infected; (3) infection in one isolated nest; and (4) a number of infection nests. After 4 days shelf life at 20 8C, degree of Botrytis infection was assessed quantitatively in both ‘Thompson Seedless’ and ‘Red Globe’ grapes by detaching and weighing affected grapes.
Table 2 Rotting incidence, rachis appearance and water loss of ‘Thompson Seedless’ table grapes after 20 days at 0 8C and shelf life
J. Retamales et al. / Postharvest Biology and Technology 29 (2003) 177 /182
a a a a a a a a 2.4 1.5 2.0 1.4 1.1 1.7 2.1 1.7 a a c c d e e bc 2.0 2.0 2.8 2.6 3.5 4.0 4.0 2.8 * Rachis appearance: 1, sound; 2, yellowish; 3, light brown; 4, brown.
100.0 d 24.0 c 8.7 b 3.0 ab 4.1 ab 6.1 b 0.5 a 3.6 ab a a a a a a a a 1.2 1.1 1.0 0.7 1.1 0.8 0.9 0.6 1.0 1.3 1.8 2.0 3.0 3.4 2.8 2.6 c c a a ab a b a 7.6 5.6 0.0 0.2 1.0 0.0 1.9 0.3
a ab bc cd ef f e e
1.7 a 2.4 a 2.1 ab 2.1 ab 100.0 d 2.8 ab 1.3 a 1.0 a 1.0 a 1.0 a 13.1 d 1.5 b
(1) Air, inoc (2) Air/pad, inoc (3) Air (4) Air/pad (5) CA 15/5 (6) CA 20/5 (7) CA 25/5 (8) CA 30/5 (9) CA 35/5 (10) CA 30/15
Rachis appearance* (1 / Additional water loss (% in 4) weight) Rotting (% in weight) Rachis appearance* (1 / Water loss (% in 4) weight)
3.2.1. Evaluation after 45 days at 0 8C No changes in SSC and TTA of ‘Red Globe’ grapes were noted after 45 days at 0 8C (data not shown). No decay was present in CA-treatments (T5 to T10), irrespective of CO2 concentration (Table 4), or in treatments having metabisulphite pads (T2 and T4). Both treatments lacking pads (T1 and T3) showed a very high incidence of rotting (a rating of almost 4). There was no difference between inoculated and non-inoculated fruit, probably because of a high concentration of Botrytis inoculum in the untreated grapes. Rachis appearance was better in fruit from treatments
Rotting (% in weight)
3.2. ‘Red Globe’ grapes
After 40 days at 0 8C
3.1.2. Evaluation after 40 days at 0 8C After 40 days at 0 8C some increase in decay was observed as compared with 20 days, with the highest incidence occurring in inoculated fruit stored in air without a pad (Table 3) and with CA-treatments attaining generally the best results. Again rachis appearance was negatively affected by CA-treatments. After an additional period of 4 days at 20 8C, decay incidence in air treatments without pads affected the entire bunches. Decay control by CA was as effective or even better than that obtained by using metabisulphite pads although there was no definite relationship between degree of decay control and CO2 concentration (Table 3). Rachis appearance was adversely affected by CA-treatments.
Treatments
tions in gas flow to compensate for changes caused by respiration. Incidence of decay increased during shelf life evaluation (4 days at 20 8C), particularly in control treatments kept in air without SO2-generating pads, with the highest incidence recorded in the treatment with Botrytis inoculation (Table 2). Inclusion of metabisulphite pads reduced the effect of inoculation to a similar extent to that of CAtreatments. The treatment with 15% CO2 was the most effective in reducing incidence of Botrytis . Again, CA-treatments affected rachis appearance, but fruit in the 15% CO2 treatment were indistinguishable from those in air.
After 40 days at 0 8C/4 days at 20 8C
J. Retamales et al. / Postharvest Biology and Technology 29 (2003) 177 /182
Table 3 Rotting incidence, rachis appearance and water loss of ‘Thompson Seedless’ table grapes after 40 days at 0 8C and shelf life
180
a a a a a a a a 1.2 0.7 0.7 1.1 3.0 0.7 0.4 1.5 a a a a a a a a b a c c c b ab ab 3.0 2.4 4.0 4.0 3.6 3.0 2.6 2.5 52.0 d 1.0 a 1.0 ab 1.5 ab 1.0 a 3.7 b 1.8 ab 1.1 ab
4. Discussion * Rachis appearance: 1, sound; 2, yellowish; 3, light brown; 4, brown.
a a a a a a a a 1.6 0.9 1.1 0.8 1.6 1.2 0.9 1.5 bc b bc de e bc cde e 2.4 1.8 2.0 2.8 3.0 2.0 2.5 3.0 b a a a a a a a 3.8 1.0 1.0 1.0 1.0 1.0 1.0 1.0
(1) Air, inoc (2) Air/pad, inoc (3) Air (4) Air/pad (5) CA 15/5 (6) CA 20/5 (7) CA 25/5 (8) CA 30/5 (9) CA 35/5 (10) CA 30/15
181
having pads than in those without pads (T2 and T4), possibly because SO2 prevented browning of the stalk and pedicels. Despite differences within CA-treatments in rachis appearance, no clear relationship could be established with the CO2 concentration of particular treatments. Water loss was low in all treatments. After an additional period of 4 days at 20 8C, fruit showed the same pattern in SSC and TTA as on removal from 0 8C (data not shown). Decay incidence was very high in fruit from treatments not having metabisulphite pads (Table 4). Again, inoculation of berries did not result in increased decay. CA-treatments, irrespective of the CO2 concentration, showed a good control of decay, similar to that of SO2 treatments. In general, rachis appearance was better in SO2-treated fruit than in controls; CA-treatments with 15 /20% CO2 resulted in fruit with the worst appearance. Water loss during 4 days in shelf life was then approximately the same as during 45 days at 0 8C and 95% relative humidity.
1.6 0.9 1.1 0.8 1.6 1.2 0.9 1.5
1.7 a 2.2 a 0.8 a 1.2 a 3.0 b 2.6 ab 32.6 c 1.0 a 2.2 bc 1.2 a 3.8 b 1.0 a
0.8 a 1.2 a
Rachis appearance* (1 /4) Rotting (% in weight) Rotting (1 /4)
Rachis appearance* (1 /4)
Water loss (% in weight)
After 45 days at 0 8C/4 days at 20 8C After 45 days at 0 8C Treatments
Table 4 Rotting incidence, rachis appearance and water loss of ‘Red Globe’ table grape after 45 days at 0 8C and shelf life
Additional water loss (% in weight)
Berry drop (%)
J. Retamales et al. / Postharvest Biology and Technology 29 (2003) 177 /182
Elevated concentrations of CO2 in CA, (15% and higher), effectively controlled Botrytis rot infection, either naturally occurring or artificially inoculated, to levels comparable to those attained by SO2 produced out of metabisulphite pads in both ‘Thompson Seedless’ and ‘Red Globe’ table grapes. This agrees with previous research where control of germination of B. cinerea in vitro was achieved with CO2 concentrations of 16% and higher in the presence of high oxygen (Wells and Uota, 1970). Similarly, Berry and Aked (1997) controlled Botrytis rot in ‘Thompson Seedless’ grapes with CO2 concentrations higher than 15%, with best results obtained with 20% CO2 and higher. These results indicate that use of CA with elevated CO2 concentrations has the potential to replace the present technology of applying SO2 for organically-grown or sulfite-free table grapes under prolonged storage/transport conditions. Possible limitations to the use of such treatments are related to the poorer rachis appearance in fruit from CA-treatments; this effect increased
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J. Retamales et al. / Postharvest Biology and Technology 29 (2003) 177 /182
with extended duration of the storage period. Such problems were reported with insecticidal CA treatments (Ahumada et al., 1996) but only after storage at 20 8C and not at 5 8C, being attributed to a storage temperature effect rather than to the CA-treatments themselves. However, the short duration of such treatments (6 days) made it difficult to compare directly with the present results. On the other hand, Berry and Aked (1997) did not report problems of rachis browning with extended periods (7 and 12 weeks) of CAtreatments. Rachis appearance could represent a limitation to extended storage periods and warrants further experiments, especially using lower CO2 concentrations and for shorter storage periods than used in this work.
Acknowledgements Professor Errol Hewett, Massey University and Professor Adel Kader, University of CaliforniaDavis are gratefully acknowledged for critical reading of the manuscript. Thanks are given to
Marisol Pe´rez for skillful technical support and Rosita Avile´s for providing fruit for the experiments.
References Ahumada, M.H., Mitcham, E.J., Moore, D.G., 1996. Postharvest quality of Thompson Seedless grapes after insecticidal controlled-atmosphere treatments. HortScience 31 (5), 836 /939. Berry, G., Aked, J., 1997. Controlled atmosphere alternatives to the post-harvest use of sulphur dioxide to inhibit the development of Botrytis cinerea in table grapes. Proceedings of the Seventh International Controlled Atmosphere Research Conference, vol. 3. UC Davis Postharv. Hortic. Series No. 17, pp. 160 /164. Mitcham, E.J., Zhou, S., Bikoba, V., 1997. Controlled atmospheres for quarantine control of three pests of table grape. J. Econ. Entomol. 90, 1360 /1370. Wells, J.M., Uota, M., 1970. Germination and growth of five fungi in low-oxygen and high-carbon dioxide atmospheres. Phytopathology 60, 50 /53. Winkler, A.J., Cook, J.A., Kliewer, W.M., Lider, L.A., 1974. General Viticulture, second ed. University of California Press, p. 710.
High-CO2 controlled atmospheres reduce decay incidence in Thompson Seedless and Red Globe table grapes Julio Retamales a,b,*, Bruno G. Defilippi a,1, Marcela Arias b, Paula Castillo a, Daniel Manrı´quez a a
Institute for Agricultural Research, La Platina Experimental Station, Casilla 439/3, Santiago, Chile b Faculty of Agricultural Sciences, Universidad de Chile, Santiago, Chile Received 7 February 2002; accepted 20 January 2003
Abstract The efficacy of CO2-enriched atmospheres on decay control of organically-grown ‘Thompson Seedless’ and ‘Red Globe’ table grapes was evaluated during storage at 0 8C. Grapes in the treatments with controlled atmosphere (CA) were inoculated with a Botrytis cinerea culture (10 000 conidia per ml) at the beginning of the experiments. Control treatments were stored in air with or without SO2-generating metabisulphite pads and either with or without Botrytis inoculation. Fruit quality attributes including soluble solids, titratable acidity, incidence of decay, stalk and pedicel appearance were measured on removal from 0 8C and during subsequent shelf-life at 18 /20 8C. CAs with CO2 at 15% or higher resulted in as good control of Botrytis as using metabisulphite pads. Stalks and pedicels were greener when metabisulphite pads were included. # 2003 Elsevier B.V. All rights reserved. Keywords: Botrytis rot; SO2 replacement; Rachis appearance; Organic
1. Introduction Some consumers are concerned about fruit being treated with pre- and postharvest chemicals. Thus, demand for organic fruits in some markets has increased, encouraging organic cultivation of fruit crops in several countries. Unfortunately,
* Corresponding author. Tel.: /56-2-757-5161; fax: /56-2541-7667. E-mail address: [email protected] (J. Retamales). 1 Present address: Postharvest Laboratory, Pomology Department, University of California Davis, Davis, CA, USA.
acceptable nonchemical postharvest decay control treatments are not yet available. Infection with grey mold caused by Botrytis cinerea is the main factor limiting prolonged storage of table grapes. Initial SO2 fumigation and/or use of SO2-releasing metabisulphite pads during transport (Winkler et al., 1974) are presently used for grapes being shipped to export markets. However, use of SO2 is not permitted for organic produce and, thus, alternative treatments to SO2-fumigation and metabisulphite pads must be developed for fruit destined for export markets. Excessive SO2 concentrations during storage can cause bleaching, which is especially detrimental in
0925-5214/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0925-5214(03)00038-3
178
J. Retamales et al. / Postharvest Biology and Technology 29 (2003) 177 /182
colored table grape varieties (Winkler et al., 1974). Therefore, ‘Red Globe’, the second most important variety in Chile, was included in our trials. Further, it is suspected that some consumers develop allergic reactions to SO2 residues left on the fruit on consumption (Berry and Aked, 1997). Thus, exclusion of SO2 in the postharvest handling of table grapes is not only important for organic fruit, but also for conventionally-grown grapes. Limited research has been conducted using controlled atmospheres (CA) during postharvest handling of table grapes. ‘Thompson Seedless’ grapes tolerate high levels of CO2 for up to 2 weeks at 0 8C (Ahumada et al., 1996; Mitcham et al., 1997) and good control of Botrytis rot has been achieved using high CO2 levels (Berry and Aked, 1997). This indicates that there may be a potential for CA to replace SO2 for controlling decay in table grapes. In this study we investigated the effect of CO2-enriched CA storage on the postharvest behavior of both organic ‘Thompson Seedless’ and ‘Red Globe’ table grapes.
that the inoculum had ready points of entry. Source of SO2 consisted of metabisulphite pads (Fresca, Quimetal, containing 7 g of metabisulphite), that were individually placed as required on the top of the grapes within boxes before they were placed at 0 8C until evaluation.
2. Material and methods
Fruit quality was evaluated immediately after removal from 0 8C after 20 and 40 days for ‘Thompson Seedless’ and after 45 days for ‘Red Globe’ grapes, followed in each case by evaluations after 4 days shelf life at 18 /20 8C. Soluble solids content (SSC) was measured in ten indivi-
2.1. Plant material Organically-grown ‘Thompson Seedless’ grapes, as commercially defined for European markets, were harvested (19.2% soluble solids and 0.71% tartaric acid) from a vineyard located in the Rengo area (120 km south of Santiago). ‘Red Globe’ grapes (19.0% soluble solids and 0.41% tartaric acid) were harvested from a vineyard in ‘transition to organic’ production located in the San Vicente area (140 km south of Santiago). Immediately after harvest, grapes were packed into 5 kg cartons in the same vineyard without being subjected to SO2 fumigation, and cooled to 2 8C with forced air. Cartons were transported to the Postharvest Laboratory, La Platina Experimental Station, Institute of Agricultural Research (INIA), in Santiago. Where required, grapes were inoculated (10 000 conidia per ml) with a culture of B. cinerea, isolated from grapes, by puncturing one grape in each bunch in the box with a tool immerged in the culture solution and having three tips, ensuring
2.2. Treatments CA-treatments used are shown in Table 1. Fruit for air and CA-treatments were maintained in airtight, 140 l sealed plastic containers at 0 8C. Gas concentrations were attained initially by adding nitrogen to containers having four fruit cartons each and then adding CO2 to the desired concentration. O2 and CO2 concentrations were measured daily using a MAPTest 3000G gas analyzer (Hitech Instruments, Luton, England) and adjusted as needed to maintain them within9/1.0% of the desired concentrations. 2.3. Quality evaluations
Table 1 Description of the treatments used in ‘Thompson Seedless’ and ‘Red Globe’ grapes Treatments
Gas levels (%)
Description
CO2 O2 (1) Air, inoc (2) Air/pad, inoc (3) Air
0 0 0
(4) Air/pad (5) CA 15/5 (CO2/O2) (6) CA 20/5 (CO2/O2) (7) CA 25/5 (CO2/O2) (8) CA 30/5 (CO2/O2) (9) CA 35/5 (CO2/O2) (10) CA 30/15 (CO2/ O2)
0 15 20 25 30 35 30
21 Inoculated, without pad 21 Inoculated, with pad 21 Non-inoculated, without pad 21 Non-inoculated, with pad 5 Inoculated, without pad 5 Inoculated, without pad 5 Inoculated, without pad 5 Inoculated, without pad 5 Inoculated, without pad 15 Inoculated, without pad
2.1 2.0 2.1 2.6 3.3 3.4 3.0 2.8
a a a b c c bc bc
2.0 1.2 2.0 1.3 1.4 1.8 2.0 2.1
a a a a a a a a
179
* Rachis appearance: 1, sound; 2, yellowish; 3, light brown; 4, brown.
48.8 d 8.2 ab 1.8 a 10.1 bc 21.6 bc 11.7 bc 10.3 bc 14.2 bc b ab ab ab a ab ab a 2.0 0.9 1.0 1.0 0.5 1.2 1.0 0.5 1.3 1.3 2.0 2.0 2.3 2.3 2.6 2.3 cd c a a a a a a 2.1 1.8 0.1 0.0 0.1 0.2 0.0 0.0
a a b b bc bc c bc
1.5 a 2.3 a 2.0 a 2.0 a
Rachis appearance* (1 / Additional water loss (% in 4) weight) Rotting (% in weight)
72.8 e 21.8 c 1.0 ab 0.9 ab 1.0 a 1.3 a 3.3 d 1.6 bc
(1) Air, inoc (2) Air/pad, inoc (3) Air (4) Air/pad (5) CA 15/5 (6) CA 20/5 (7) CA 25/5 (8) CA 30/5 (9) CA 35/5 (10) CA 30/15
3.1.1. Evaluation after 20 days at 0 8C Grapes kept at 0 8C for 20 days had the same SSC and TTA as at harvest (data not shown). Rotting incidence (Table 2) was lower in CAtreatments (T5 to T10) than in treatments with metabisulphite pads (T2 and T4). Those treatments lacking pads (T1 and T3) had the highest incidence of decay, whether or not they were inoculated, probably because of the presence of Botrytis inoculum in untreated grapes. No berry browning occurred in any treatment. Rachis appearance was negatively affected by CA-treatments. Water loss was minimal in all treatments as fruit was stored in closed containers and maintained in static conditions with only minor correc-
Rachis appearance* (1 / Water loss (% in 4) weight)
3.1. ‘Thompson Seedless’ grapes
Rotting (% in weight)
3. Results
After 20 days at 0 8C/4 days at 20 8C
Experimental design was completely randomized. The experimental unit was one bunch replicated four times within different boxes. Analysis of variance and Duncan’s test were used for analysis with a level of significance at P B/0.05.
After 20 days at 0 8C
2.4. Statistical analysis
Treatments
dual berries per bunch with a refractometer (Atago); and total titratable acidity (TTA) was determined on a composite sample of the same berries by using 0.1 N KOH up to a pH of 8.2 and expressed as percentage of tartaric acid. Water loss was measured by weighing individual bunches at the beginning of the experiments and again at each evaluation. Rachis appearance was rated as follows: (1) green; (2) yellow; (3) light brown; and (4) brown. On removal of ‘Red Globe’ grapes from 0 8C, damage caused by B. cinerea was rated as follows: (1) no Botrytis damage; (2) isolated berries infected; (3) infection in one isolated nest; and (4) a number of infection nests. After 4 days shelf life at 20 8C, degree of Botrytis infection was assessed quantitatively in both ‘Thompson Seedless’ and ‘Red Globe’ grapes by detaching and weighing affected grapes.
Table 2 Rotting incidence, rachis appearance and water loss of ‘Thompson Seedless’ table grapes after 20 days at 0 8C and shelf life
J. Retamales et al. / Postharvest Biology and Technology 29 (2003) 177 /182
a a a a a a a a 2.4 1.5 2.0 1.4 1.1 1.7 2.1 1.7 a a c c d e e bc 2.0 2.0 2.8 2.6 3.5 4.0 4.0 2.8 * Rachis appearance: 1, sound; 2, yellowish; 3, light brown; 4, brown.
100.0 d 24.0 c 8.7 b 3.0 ab 4.1 ab 6.1 b 0.5 a 3.6 ab a a a a a a a a 1.2 1.1 1.0 0.7 1.1 0.8 0.9 0.6 1.0 1.3 1.8 2.0 3.0 3.4 2.8 2.6 c c a a ab a b a 7.6 5.6 0.0 0.2 1.0 0.0 1.9 0.3
a ab bc cd ef f e e
1.7 a 2.4 a 2.1 ab 2.1 ab 100.0 d 2.8 ab 1.3 a 1.0 a 1.0 a 1.0 a 13.1 d 1.5 b
(1) Air, inoc (2) Air/pad, inoc (3) Air (4) Air/pad (5) CA 15/5 (6) CA 20/5 (7) CA 25/5 (8) CA 30/5 (9) CA 35/5 (10) CA 30/15
Rachis appearance* (1 / Additional water loss (% in 4) weight) Rotting (% in weight) Rachis appearance* (1 / Water loss (% in 4) weight)
3.2.1. Evaluation after 45 days at 0 8C No changes in SSC and TTA of ‘Red Globe’ grapes were noted after 45 days at 0 8C (data not shown). No decay was present in CA-treatments (T5 to T10), irrespective of CO2 concentration (Table 4), or in treatments having metabisulphite pads (T2 and T4). Both treatments lacking pads (T1 and T3) showed a very high incidence of rotting (a rating of almost 4). There was no difference between inoculated and non-inoculated fruit, probably because of a high concentration of Botrytis inoculum in the untreated grapes. Rachis appearance was better in fruit from treatments
Rotting (% in weight)
3.2. ‘Red Globe’ grapes
After 40 days at 0 8C
3.1.2. Evaluation after 40 days at 0 8C After 40 days at 0 8C some increase in decay was observed as compared with 20 days, with the highest incidence occurring in inoculated fruit stored in air without a pad (Table 3) and with CA-treatments attaining generally the best results. Again rachis appearance was negatively affected by CA-treatments. After an additional period of 4 days at 20 8C, decay incidence in air treatments without pads affected the entire bunches. Decay control by CA was as effective or even better than that obtained by using metabisulphite pads although there was no definite relationship between degree of decay control and CO2 concentration (Table 3). Rachis appearance was adversely affected by CA-treatments.
Treatments
tions in gas flow to compensate for changes caused by respiration. Incidence of decay increased during shelf life evaluation (4 days at 20 8C), particularly in control treatments kept in air without SO2-generating pads, with the highest incidence recorded in the treatment with Botrytis inoculation (Table 2). Inclusion of metabisulphite pads reduced the effect of inoculation to a similar extent to that of CAtreatments. The treatment with 15% CO2 was the most effective in reducing incidence of Botrytis . Again, CA-treatments affected rachis appearance, but fruit in the 15% CO2 treatment were indistinguishable from those in air.
After 40 days at 0 8C/4 days at 20 8C
J. Retamales et al. / Postharvest Biology and Technology 29 (2003) 177 /182
Table 3 Rotting incidence, rachis appearance and water loss of ‘Thompson Seedless’ table grapes after 40 days at 0 8C and shelf life
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a a a a a a a a 1.2 0.7 0.7 1.1 3.0 0.7 0.4 1.5 a a a a a a a a b a c c c b ab ab 3.0 2.4 4.0 4.0 3.6 3.0 2.6 2.5 52.0 d 1.0 a 1.0 ab 1.5 ab 1.0 a 3.7 b 1.8 ab 1.1 ab
4. Discussion * Rachis appearance: 1, sound; 2, yellowish; 3, light brown; 4, brown.
a a a a a a a a 1.6 0.9 1.1 0.8 1.6 1.2 0.9 1.5 bc b bc de e bc cde e 2.4 1.8 2.0 2.8 3.0 2.0 2.5 3.0 b a a a a a a a 3.8 1.0 1.0 1.0 1.0 1.0 1.0 1.0
(1) Air, inoc (2) Air/pad, inoc (3) Air (4) Air/pad (5) CA 15/5 (6) CA 20/5 (7) CA 25/5 (8) CA 30/5 (9) CA 35/5 (10) CA 30/15
181
having pads than in those without pads (T2 and T4), possibly because SO2 prevented browning of the stalk and pedicels. Despite differences within CA-treatments in rachis appearance, no clear relationship could be established with the CO2 concentration of particular treatments. Water loss was low in all treatments. After an additional period of 4 days at 20 8C, fruit showed the same pattern in SSC and TTA as on removal from 0 8C (data not shown). Decay incidence was very high in fruit from treatments not having metabisulphite pads (Table 4). Again, inoculation of berries did not result in increased decay. CA-treatments, irrespective of the CO2 concentration, showed a good control of decay, similar to that of SO2 treatments. In general, rachis appearance was better in SO2-treated fruit than in controls; CA-treatments with 15 /20% CO2 resulted in fruit with the worst appearance. Water loss during 4 days in shelf life was then approximately the same as during 45 days at 0 8C and 95% relative humidity.
1.6 0.9 1.1 0.8 1.6 1.2 0.9 1.5
1.7 a 2.2 a 0.8 a 1.2 a 3.0 b 2.6 ab 32.6 c 1.0 a 2.2 bc 1.2 a 3.8 b 1.0 a
0.8 a 1.2 a
Rachis appearance* (1 /4) Rotting (% in weight) Rotting (1 /4)
Rachis appearance* (1 /4)
Water loss (% in weight)
After 45 days at 0 8C/4 days at 20 8C After 45 days at 0 8C Treatments
Table 4 Rotting incidence, rachis appearance and water loss of ‘Red Globe’ table grape after 45 days at 0 8C and shelf life
Additional water loss (% in weight)
Berry drop (%)
J. Retamales et al. / Postharvest Biology and Technology 29 (2003) 177 /182
Elevated concentrations of CO2 in CA, (15% and higher), effectively controlled Botrytis rot infection, either naturally occurring or artificially inoculated, to levels comparable to those attained by SO2 produced out of metabisulphite pads in both ‘Thompson Seedless’ and ‘Red Globe’ table grapes. This agrees with previous research where control of germination of B. cinerea in vitro was achieved with CO2 concentrations of 16% and higher in the presence of high oxygen (Wells and Uota, 1970). Similarly, Berry and Aked (1997) controlled Botrytis rot in ‘Thompson Seedless’ grapes with CO2 concentrations higher than 15%, with best results obtained with 20% CO2 and higher. These results indicate that use of CA with elevated CO2 concentrations has the potential to replace the present technology of applying SO2 for organically-grown or sulfite-free table grapes under prolonged storage/transport conditions. Possible limitations to the use of such treatments are related to the poorer rachis appearance in fruit from CA-treatments; this effect increased
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with extended duration of the storage period. Such problems were reported with insecticidal CA treatments (Ahumada et al., 1996) but only after storage at 20 8C and not at 5 8C, being attributed to a storage temperature effect rather than to the CA-treatments themselves. However, the short duration of such treatments (6 days) made it difficult to compare directly with the present results. On the other hand, Berry and Aked (1997) did not report problems of rachis browning with extended periods (7 and 12 weeks) of CAtreatments. Rachis appearance could represent a limitation to extended storage periods and warrants further experiments, especially using lower CO2 concentrations and for shorter storage periods than used in this work.
Acknowledgements Professor Errol Hewett, Massey University and Professor Adel Kader, University of CaliforniaDavis are gratefully acknowledged for critical reading of the manuscript. Thanks are given to
Marisol Pe´rez for skillful technical support and Rosita Avile´s for providing fruit for the experiments.
References Ahumada, M.H., Mitcham, E.J., Moore, D.G., 1996. Postharvest quality of Thompson Seedless grapes after insecticidal controlled-atmosphere treatments. HortScience 31 (5), 836 /939. Berry, G., Aked, J., 1997. Controlled atmosphere alternatives to the post-harvest use of sulphur dioxide to inhibit the development of Botrytis cinerea in table grapes. Proceedings of the Seventh International Controlled Atmosphere Research Conference, vol. 3. UC Davis Postharv. Hortic. Series No. 17, pp. 160 /164. Mitcham, E.J., Zhou, S., Bikoba, V., 1997. Controlled atmospheres for quarantine control of three pests of table grape. J. Econ. Entomol. 90, 1360 /1370. Wells, J.M., Uota, M., 1970. Germination and growth of five fungi in low-oxygen and high-carbon dioxide atmospheres. Phytopathology 60, 50 /53. Winkler, A.J., Cook, J.A., Kliewer, W.M., Lider, L.A., 1974. General Viticulture, second ed. University of California Press, p. 710.