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WSU-TFREC/Postharvest Information Network/Factors Affecting Braeburn Browning Disorder



Factors Affecting Braeburn Browning Disorder


Introduction

Braeburn is susceptible to the erratic development of Braeburn browning disorder (BBD) and formation of internal cavities (IC; resembling those of internal CO2 injury). This study quantified the effects of cool growing season, advanced harvest maturity, shellac waxing, storage temperatures, elevated storage CO2, and low storage O2 on the development of BBD and IC in British Columbia-grown Braeburn apples.

Braeburn samples were harvested four times at weekly intervals in 1993-95 or three times at biweekly intervals in 1996, from two to six orchards in the southern interior of British Columbia. Harvesting commenced on 4 Oct. in 1993, 21 Sept. in 1994, 25 Sept. in 1995, and 1 Oct. in 1996, 1 to 2 weeks before anticipated commercial harvest. Starch index and fruit disorders were determined immediately after harvest.

The storage treatments were: air and 1.2% O2 + 1.0% CO2 in 1993, air and 1.5% O2+ 1.2% CO2 in 1994, and various combinations of O2 (21% and 1.5%) and CO2 (0.1%, 1.2%, and 3.0%) in 1996. The air storage samples were held in a 0°C room. All CA samples were cooled in 0°C air overnight prior to storage in gas-tight cabinets kept at 0°, 1.7°, or 3.0°C. The O2 and CO2 atmospheres were established within 1 to 2 days of sealing by purging with N2 and additions of CO2.


CA vs. Air Storage

Except for the last pick (with 10% BBD and 12% IC) in 1996, the 1993-96 samples had <3% BBD and IC varied greatly with orchard and season (Table 2). In New Zealand, Elgar et al. observed that BBD is more prevalent in colder regions, or within colder districts, or at higher altitudes within a region. It is possible that cool growing conditions alter cellular metabolism, reduce skin and tissue diffusivity, and/or increase susceptibility to elevated CO2 and low O2. Park has shown seasonal variability of tissue resistance to gas diffusion in 'McIntosh' apples. Cool growing seasons have increased the risks of core browning and low temperature breakdown in apples.


Advanced Harvest Maturity

BBD and IC increased in CA-stored fruit as harvest was delayed in 2 of the 4 years (Table 1). This may be the result of increased respiration, tissue and skin resistance to gas exchange, and/or sensitivity to low O2 and elevated CO2 atmospheres. Meheriuk has shown more extensive internal CO2 injury in later-picked 'Golden Delicious' apples. Park has observed a change in tissue resistance to gas diffusion in 'McIntosh' apples during development and storage. Resistance first increases and then decreases rapidly during the period of fruit maturation, with the highest resistance registered before or on the ethylene climacteric dates.


Elevated CO2 and Low O2

The presence of IC in air-stored fruit and the development of BBD and IC in CA-stored fruit (Table 1) were indicative of a buildup of internal CO2 and/or depletion of internal O2, caused by low tissue diffusivity and/or high skin resistance. This view was supported by the results of the 1996 experiment: that BBD and IC were more prevalent (1) in an atmosphere of 1.2% or 3.0% CO2 with 21% O2 than if CO2 was maintained at 0.1% and (2) in an atmosphere of 1.5% O2 than if O2 was kept at 21% (Figure 1). The results explain why 'Braeburn' apples held in CA were more susceptible to BBD and IC than fruit held in air (Table 1). Tolerance to external CO2 generally decreases as external O2 is decreased, while tolerance to low external O2 decreases as external CO2 is increased.

Table 1. Effect of harvest datez and storage regime on Braeburn browning disorder (BBD, %) and internal cavities (IC, %) in Braeburn apples after 6 months in 0C air or CAy storage plus 7 days in 20°C air.

Year=1993
HarvestStarch IndexAir BBDCA BBDAir ICCA IC
11.103310
22.708215
33.638023
44.5031421
HarvestNSNS
Storage***
H x S*NS
Year=1994
HarvestStarch IndexAir BBDCA BBDAir ICCA IC
11.40000
22.50000
33.20001
44.70007
HarvestNS**
StorageNSNS
H x SNSNS
Year=1995
HarvestStarch IndexAir BBDCA BBDAir ICCA IC
11.701314
22.519427
33.309323
44.2313330
Harvest*****
Storage*****
H x SNSNS
Year=1996
HarvestStarch IndexAir BBDCA BBDAir ICCA IC
10.81326
22.506221
34.710331224
Harvest**
Storage***
H x SNSNS
zHarvest commenced on 4 Oct. 1993, 21 Sept. 1994, 25 Sept. 1995, and 1 Oct. 1996 at weekly (1993-95) or biweekly (1996) intervals.
y1.2% O2 + 1.0% CO2 (1993) or 1.5% O2 + 1.2% CO2 (1994-96)
xStarch index values of 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9 on a 0-9 scale represent 1, 10, 17, 26, 38, 51, 67, 78, 85, and 99%, respectively, of the cross-sectional area of fruit clear of starch.



Figure1. Effect of harvest maturity (starch index), storage CO2 and storage O2 on the incidence of "Braeburn browning disorder" (BBD) and "internal cavities" (IC) in Braeburn apples held for 4.5 months in 0° storage and 7 days in 20° air (n=5 orchards, 1996).



Table 2. Variation in preharvest temperaturez, degree-day >10Cy, and incidence of Braeburn browning disorder (BBD) in Braeburn apples after 6 months in 0°C air or CAx storage plus 7 days in 20°C air.

 Mean temperatureDegree-dayBBD (%)
YearMayJuneJulyAugSep>10°CAverageLow-high
199414.717.123.920.617.0130000-0
199515.518.120.917.217.0118390-20
199316.816.817.619.115.41131129-15
199610.816.621.720.413.01042140-25
zCollected at the Agriculture and Agri-Food Canada weather station, Summerland, B.C.
yCumulated between 1 May and harvest.
x 1.2% O2 + 1.0% CO2 (1993) or 1.5% O2 + 1.2% CO2 (1994-96)


Wax Coating and CO2 Scrubbing

Coating apple with NurtiSave modifies the natural permeability of fruit skin to gases and results in changes in internal gas compositions. Coating fruit with shellac (but not carnauba) wax increased BBD after 1 month in 0°C air storage; the disorder did not increase further during subsequent shelf-life tests and additional air storage (Table 3). IC was, however, unaffected by either wax treatment. Hagenmaier and Shaw have shown that resistance to CO2 and O2 is higher for coatings made from shellac than those made from carnauba. In this study, placement of hydrated lime in packed boxes did not reduce BBD or IC in both waxed and non-waxed fruit (Table 3). The results suggest that diffusion of CO2 across 'Braeburn' apple tissue and skin was low or nonexistent. Rajapakse et al. have reported that skin resistance of 'Braeburn' apples to O2 diffusion is two and four times higher than those of 'Granny Smith' and 'Cox's Orange Pippin', respectively. Park et al. have observed that skin discoloration associated with low O2 is positively correlated with fruit resistance to gas diffusion at harvest. Johnson et al. have found correlation between increased internal injury and high resistance to gas diffusion.

Table 3. Effect of postharvest wax treatment and CO2 scrubbing with hydrated lime on Braeburn browning disorder and internal cavities in late-picked Braeburn apples after 1 and 2 months in 0°C air (at removal) plus 7 days in 20°C air (after shelf-life test).

Braeburn browning (at removal)
 1-month2-month
Wax treatmentLime-+-+
Control11ay17a14a17a
Carnuba15a19a>24b11a
Shellac25b47b23ab38b
Lime**NS
% of fruit affected (after shelf-life test)
 1-month2-month
Wax treatmentLime-+-+
Control13a11a13a14a
Carnuba23b27ab15a17a
Shellac37c41b30b41b
LimeNSNS
Internal cavities (at removal)
 1-month2-month
Wax treatmentLime-+-+
Control0a2a1a2a
Carnuba1a1a1a4a
Shellac1a1a2a1a
LimeNSNS
% of fruit affected (after shelf-life test)
 1-month2-month
Wax treatmentLime-+-+
Control4a5a10a7a
Carnuba1a4a3a9a
Shellac5a7a9a10a
LimeNSNS
zStarch index=3.6 on a 0 to 9 scale, BBD = 3%, and watercore = 29%. After 19 days in 0C air storage prior to waxing: BBD = 14% and watercore = 15%.
yMean separation, within column, by Duncan's new multiple range test at P<=0.05.


Storage Temperature

Storage in CA at 1.7° and 3.0°C instead of 0°C had no consistent effect on BBD and IC (data not shown). Elgar et al. reported similar results.

Acknowledgment: This work was not possible without the capable assistance of R. Yastremski, P. Schofield, W. Urban, S. Horton, and E. Huffman and the financial support of the Okanagan Valley Tree Fruit Authority and the Okanagan Federated Shippers Association.

Dr. O. L. (Sam) Lau, Postharvest Physiologist

Industry Research Program, Okanogan Federated Shippers Association

Tree Fruit Postharvest Journal 10(1):6-9
February 1999

Dr. O. L. (Sam) Lau, Postharvest Physiologist

Industry Research Program, Okanogan Federated Shippers Association

Tree Fruit Postharvest Journal 10(1):6-9
February 1999

Dr. O. L. (Sam) Lau, Postharvest Physiologist

Industry Research Program, Okanogan Federated Shippers Association

Tree Fruit Postharvest Journal 10(1):6-9
February 1999

Dr. O. L. (Sam) Lau, Postharvest Physiologist

Industry Research Program, Okanogan Federated Shippers Association

Tree Fruit Postharvest Journal 10(1):6-9
February 1999

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