AP509 Storage systems to control scald on apples & pears

Barry Tugwell & Louise Chvyl SARDI

AP509 This report is published by Hie Horticultural Researdi and Devdqpmoot Corporaticm to pass cm information aHiceming horticultural researdi and devdopment undertake for the { pple and pear industry.

The research contained in tiiis r^)ort was funded by the Horticultural Research and Devdopment Corporation with the financial support of the iqpple and pear industry.

All expressions of < inion are not to be r^arded as expressing the opinion of tiie Horticultural Researdi and Devdopmofit Corporati(»i or any autiiority of the Australian Govemmaat

The Corporaticm and tift Australian Govemmoit acc^t no responsibility for any <£ tiie opinions or the accuracy of the informati(m contained in this rqx>rt and readers should rely upcHi dieir own oiquiries in making decisions concerning their own interests.

Cover price: $20.00 HRDC ISBN I 86423 857 7 Published and distributed by: Horticultural Research & Developm^t Corporation Levd6 7 Merriwa Street Gordon NSW 2072 Telephone: (02) 9418 2200 Fax: (02) 9418 1352 E-Mail: hrdc@hrdc.gov.au

© Copyright 1999

HRDVC

HORTICULTURAL RESEARCH & DEVELOPMENT CORPORATION

Partnership in horticulture

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H.R.D.C. FINAL REPORT

PROJECT NO. AP 509

STORAGE SYSTEMS TO CONTROL SCALD ON APPLES AND PEARS

Barry Tugwell and Louise Chvyl

January 1999

Final report HRDC Project no. AP 509

STORAGE SYSTEMS TO CONTROL SCALD ON APPLES AND PEARS

Principal Investigator:-

Barry Tugwell Chief Scientist, Horticulture South Australian Research & Development Institute Plant Research Centre Hartley Grove URRBRAE SA5064

Postal address :-GPO Box 397, ADELAIDE SA 5001 Tel: 8303 9417 Fax: 8303 9424 email: tugwell.barry@pi.sa.gov.au

F.:\applerep.DOC

CONTENTS

Industry Summary 4

Technical Summary and Recommendations 6

Directions for Future Research 7

Storage Systems to control scald on apples and pears 8

Introduction..... 8 Method 9 Results 10

Evaluation of storage atmosphere for scald control 10 Evaluation of alcohol treatment for control of scald 16 Evaluation of petroleum oil for scald control 19 Evaluation of bulk treatment with alcohol in a C.A. room 20

Results of Research by K.J. Scott 22

References 24

Publications & Reports 25

Appendix 1 Maturity the Key to Quality for Apples, Pears and Cherries

Appendix 2 Predicting Harvest dates

INDUSTRY SUMMARY

Storage trials were carried out in 1995, 1996 and 1997 to evaluate low oxygen storage atmospheres and an alcohol vapour treatment for controlling scald on susceptible varieties of apples and pears. A petroleum based oil formulated for the surface disinfestation of citrus was also tested for effectiveness in controlling scald.

In 1995 a low oxygen storage atmosphere of less than 1% oxygen was compared with a nitrogen flushed atmosphere of 1.5% oxygen for controlling scald.

In 1996 apple and pear varieties were treated with alcohol in plastic bags, stored in a controlled atmosphere of 2% oxygen and assessed for scald control and quality.

In 1997 bulk bins of Granny Smith, Red Delicious apples and Packham pears were treated with alcohol, stored in a controlled atmosphere of 2% oxygen and assessed for scald control and quality.

HARVEST MATURITY Storage trials confirmed the ideal harvest maturity for Pink Lady apples intended for long term storage to be the last week of April extending into the first week of May. Sundowner apples should be harvested 2 weeks later than Pink Lady, harvesting should commence at the end of the first week of May and conclude by the end of the third week in May.

LOW OXYGEN STORAGE The apple varieties Pink Lady, Sundowner, Red Delicious, Fuji, Golden Delicious, Granny Smith and Packham pears stored well in <1% oxygen with carbon dioxide maintained at <1%. All varieties remained firmer in storage and scald susceptible varieties showed a lower incidence of scald when compared with fruit stored in a nitrogen flushed atmosphere of 2% oxygen and less than 1% carbon dioxide.

Low oxygen storage however did not consistently eliminate scald on early harvests of Red Delicious and Granny Smith apples.

A brown stain on Fuji apples was not affected by either storage system.

ALCOHOL TREATMENT Alcohol treatment controlled scald on early harvested Pink Lady apples and reduced scald by 50% on other scald susceptible varieties of apples and pears. However changes in skin colour on Red Delicious, core flush of Granny Smith apples and tainting of Jonathans were observed.

Research by Kevin Scott at the University of NSW established that alcohol treatment completely controlled scald on Graimy Smith apples when stored for 16 weeks. Scald control was also achieved with Red Delicious apples however a change in the red colour of the skin occurred.

Preliminary tests with several other alcohols has established that they also reduce superficial scald and one of these controlled scald without inducing a colour change on Red Delicious apples.

A petroleum based oil was effective in controlling scald but when used without a fungicide caused excessive mould wastage of treated fruit.

The varieties Sundowner and Golden Delicious remained scald free when removed from storage in November.

Pink Lady apples from the first harvest in mid April 1996 developed scald when removed from storage in September.

BULK TREATMENT WITH ALCOHOL Alcohol treatment of bulk bins of fruit in a C. A. room followed by storage for 6 months in 2% oxygen controlled scald on Granny Smith and Red Delicious apples and Packham Pears.

Scald on Packham Pears was controlled for up to 8 months however Granny Smith apples showed scalding after 7 months storage and developed severe core flush after 8 months storage. Red Delicious apples developed a skin discolouration after 7 months storage.

TECHNICAL SUMMARY AND RECOMMENDATIONS

For best retention of quality, scald susceptible apples and pears should be dipped after harvest in Diphenylamine (DPA) and stored in a controlled atmosphere (CA) of between 1.5% and 2.0% oxygen with carbon dioxide maintained at less than the oxygen concentration.

Pink Lady apples harvested in mid April for export or storage are susceptible to scald if stored beyond September. Treatment with a scald inhibitor and fungicide is recommended. Golden Delicious apples have a low risk of scalding but treatment with a scald inhibitor and fungicide is recommended for fruit from warmer growing regions.

Sundowner apples did not develop scald during storage however treatment with a fungicide is recommended to control postharvest rots.

Storage in less than 1% oxygen or an atmosphere continuously flushed with nitrogen cannot be recommended as an alternative to DPA for consistent control of scald.

Alcohol and oil are promising alternatives to DPA for scald control however further research is required to establish treatment rates and overcome negative effects on fruit quality.

DIRECTIONS FOR FUTURE RESEARCH

Low oxygen storage, treatment of fruit with alcohol or oil and harvesting fruit at ideal maturity can reduce the incidence and severity of scald but no single treatment is as effective as post harvest treatment with the antioxidant Diphenylamine.

Further research is required to develop application methods to maximise scald control with alcohol and oils, evaluate otiher alcohols that may not cause changes to red pigmentation on Delicious apples and identify a denaturant that can be safely used to allow excise free alcohol to be used.

STORAGE SYSTEMS TO CONTROL SCALD ON APPLES AND PEARS

Barry Tugwell and Louise Chvyl South Australian Research and Development Institute

Hartley Grove, Urrbrae, S.A. 5064

INTRODUCTION Increasing consumer demand for chemical residue free fruit may in the fixture prevent the use of antioxidant chemicals to control scald. Susceptibility of apples to scald reduces with maturity and accurate timing of harvest combined with new storage technology may be sufficient to control scald without using chemical antioxidants. In addition some new varieties may be less scald susceptible than existing commercial varieties.

Research from 1976 to 1989 (Tugwell, 1989) established and demonstrated practical systems for design and operation of CA stores to maintain specialised low oxygen atmospheres. Research in Victoria (Little, 1988) has shown that low oxygen storage atmospheres can reduce scald and overseas research (Dilley, 1989) has shown that nitrogen purging of CA stores can reduce or eliminate the need for chemical control of scald. More recent overseas research established that low oxygen levels controlled scald of Granny Smith apples (Patterson, 1993).

Fast cooling combined with rapid establishment of low oxygen CA atmospheres will reduce scald on susceptible varieties and the introduction of nitrogen separation equipment to continuously flush out ethylene and other volatiles from CA rooms has reduced scald on some varieties of apples and pears.

By determining the scald susceptibility of current and new varieties over a range of maturities, harvest dates can be set. When combined with new storage strategies, it should be possible to reduce scald to tolerable levels and eliminate the need to apply chemical antioxidants.

Storage trials fiinded under project AP123 showed some quality benefits from storage in Nitrogen flushed atmospheres but no significant reduction in scald.

During the 1994 season, commercial control of scald on Granny Smith apples harvested in late April was achieved with an atmosphere of 0.7% oxygen.

Low oxygen storage was fiirther evaluated in 1995 on Granny Smith and other varieties of apples and pears.

The timing of harvest is vital in ensuring that fruit has sufficient colour, size, texture and flavour to satisfy the consumer without compromising the internal condition necessary for long term storage.

Project AP123 established harvest criteria for W.A. grown Pink Lady and Sundowner apples. During 1994 it was established that S.A. grown fruit from young trees matured earlier than W.A. fruit and had a brighter red colour at maturity.

Storage performance of fruit grown under cooler conditions in the southern area of Australia was assessed during the 1995 season.

In December 1995, Kevin Scott from the University of N.S.W. presented results of his research which showed that alcohol or oils applied after harvest controlled scald on Granny Smith and Red Delicious apples. During the 1996 storage season the effect of alcohol treatment combined with low oxygen storage on scald and quality of apple and pear varieties was determined. In 1997 the alcohol treatment was applied to bulk lines of fruit which were then stored in a low oxygen CA atmosphere.

METHOD In 1995 three harvests were made at fortnightly intervals from mature trees carrying a heavy crop of averaged size fruit of the varieties Granny Smith, Red Delicious (Hi Early), Red Fuji, Sundowner, Golden Delicious and Packham pears.

Fruit maturity factors (starch index, sugar, fumness and colour) were measured. On each harvest date the fruit were rapidly cooled to 0°C and stored in specialised CA atmospheres for examination afto* 6, 8 and 10 months storage.

Half of the fruit was stored in a CA atmosphere of less than 0.7% carbon dioxide maintained by product generation and lime to absorb carbon dioxide. The second room was continuously purged with nitrogen from a P.S.A. air sq)arator to maintain 1.5% oxygen and 1.5% carbon dioxide.

On removal from storage the fruit was assessed for internal quality, scald and storage disorders. The data was analysed to determine effects of harvest maturity and storage method on fruit maturity and scald.

In 1996 Granny Smith, Red Delicious (Hi Early), Red Fuji, Pink Lady and Sundowner apples and Packham pears were harvested at fortnightly intervals, treated with the equivalent of 0.2g of alcohol per fruit and sealed in plastic bags. Prior to storage in an atmosphere of 2% oxygen and less than 1% carbon dioxide, the bags were opened to allow equilibration with the C. A. atmosphere.

Equivalent harvests of fruit not treated with alcohol were stored in a separate CA room. On removal from storage fruit was evaluated for scald, skin blemish^, internal quality and off flavours.

In 1997 bulk bins of Granny Smith, Red Delicious apples and Packham pears were treated with 1 litre of alcohol per bin (the equivalent of 0.3g of alcohol per fruit) in a CA room, stored in 2% oxygen and assessed for scald and storage disorders after 6, 7 and 8 months storage.

Kevin Scott, consultant in postharvest horticulture, evaluated alcohol and other alternative treatments for overcoming colour changes in Red Delicious apples following treatment.

RESULTS

EVALUATION OF STORAGE ATMOSPHERES FOR SCALD CONTROL Storage in low oxygen atmospheres of less than 1 % oxygen was more effective in controlling scald than continuous flushing with nitrogen to maintain oxygen at 2%. Complete control of scald was not achieved for scald susceptible varieties stored for more than 6 months.

GRANNY SMITH

Effect of Low Oxygen Storage and Nitrogen Flushing on Scald of Granny Smith Apples after 7 months storage

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10/04/95 24/04/95 8/05/95

Harvest Date

After 5 months C.A. storage Granny Smith apples harvested during early April had developed severe superficial scald. Low oxygen storage reduced the severity and incidence of scald at all harvests however after 8 months storage more than 50% of the fruit had developed scald. Nitrogen flushing was not effective in controlling scald with most fruit from all harvests scalding after 5 months storage.

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RED DELICIOUS

Neither low oxygen storage or nitrogen flushing were effective in controlling scald on Red Delicious apples after 6 months C.A. storage.

Scald on Red Delicious Apples

Effect of low oxygen storage on firmness of Red Delicious apples after 8 months storage

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Low oxygen storage however increased the firmness of fruit at all harvest maturities. Fruit harvested on the 23rd March and stored in less than 1% oxygen for 8 months was 1 kg firmer than fruit stored in a nitrogen flushed atmosphere.

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FUJI

Very little scald developed on Fuji apples of all maturities but a brown staining which developed on fruit harvested in mid April was not affected by either storage system.

I Fuji Apples stored well in low oxygen

Fuji apples stored in a low oxygen atmosphere were firmer than fruit stored in a nitrogen flushed atmosphere after 7 months storage.

PINK LADY

Pink Lady apples harvested prior to the 20th of April scalded after 5 months storage however low oxygen storage considerably reduced the incidence and severity of scald after 7 months storage.

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Effect of low oxygen storage and maturity on scald on Pink Lady Apples after 7 months storage

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1 5th April '95 20th April '95

Harvest Date 4th May '95

PACKHAM PEARS

Packham pears harvested from the 16th February 1995 to the 16th March 1995 stored well in both low oxygen storage and a nitrogen flushed atmosphere for 8 months until November 1995.

Packham Pears C.A. stored for 8 months

No scald developed on pears stored in either atmosphere after 6 months storage however a trace of scald developed on C.A. stored fruit after 8 months storage.

E:\applerep.IXX: 13 28/01/99

SUNDOWNER

Sundowner apples stored well in both storage atmospheres over a range of harvest maturities from 20th April 1995 to 18th May 1995. Fruit retained a firmness of 9.0 kg after 6 months storage and remained scald free when removed from storage.

Sundowner Apples scald free after 6 months storage

GOLDEN DELICIOUS -

Golden Delicious apples rapidly softened in storage dropping 2 kg in firmness from 8.0 kg at harvest to 5.6 kg after 7 months storage.

Storage in a low oxygen atmosphere resulted in fruit 0.5 kg firmer than that stored in a nitrogen flushed atmosphere.

Scald developed on fruit harvested early during the first week of March stored in a nitrogen flushed atmosphere but was not observed on fruit stored in a low oxygen atmosphere.

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Effect of Harvest Maturity on Storage Rots of Golden Delicious Apples

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Over mature Golden Delicious apples were very susceptible to the development of storage rots. 80% of fruit harvested on the 5th of April 1995 developed storage rots after 5 months storage.

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EVALUATION OF ALCOHOL TREATMENT FOR CONTROL OF SCALD

GRANNY SMITH APPLES

Effect of Alcohol Treatment on Scald Incidence on Granny Smith Apples Harvested on 16/4/96

•Alcohol .Treated I C.A.

Months Storage

Alcohol treatment applied to Granny Smith apples sealed in a plastic liner followed by C.A. storage reduced scald by 50% for up to 5 months storage. The treatment was not effective in controlling scald on fruit stored for 7 or 9 months.

RED DELICIOUS APPLES

Alcohol treatment reduced scald on fruit harvested in mid March and stored for 6 months however brown staining and skin discolouration spoilt the appearance of fruit when removed from storage.

EAapplerep.DOC 16 28/01/99

PINK LADY APPLES

Effect of Alcohol Treatment on Scald Incidence on Pink Lady Apples Harvested on 16/4/96

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Pink Lady apples harvested on the 16th April 1996 developed superficial scald after 5 months storage in a C.A. atmosphere of 2% O2. Scald increased from 20% on removal from storage in September to 78% in February (9 months storage).

Delaying harvest until the 1st of May 1996 completely controlled scald.

Alcohol treatment in plastic liners completely controlled scald on fruit harvested on the 16th ofAprill996.

Early harvested Pink Lady Apples may develop scald during storage

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PACKHAM PEARS

Effect of Alcohol Treatment on Scald Incidence on Packham Pears Harvested on 29/2/96

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80 70 60 50 40 30 20 10 0

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7 9 11 Months stored

Packham pears harvested on 29th February 1996 developed superficial scald after 7 months storage. Alcohol treatment controlled scald for up to 7 months storage however after 9 or 11 months storage scald was reduced by only 50%.

FUJI APPLES

Effect of Alcohol treatment on scald incidence on Fuji apples harvested on 10/4/96

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•Alcohol Treated

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i 8 Months stored

10

Fuji apples harvested in late March scalded severely after 5 months storage. Fruit harvested during the last week of April did not develop scald until after 9 months storage. Treatment with alcohol controlled scald after up to 5 months storage however after 7 months or 9 months storage scald was only reduced by 50%.

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EVALUATION OF A PETROLEVMOIL FOR SCALD CONTROL

GRANNY SMITH APPLES Giaony Smith ^ples dipped in a petroleum based post harvest dipping oil £q)peared to be fiee of scald after 5 months storage however a high incidence of storage rots made it difficult to assess the fruit for scald.

Tlie dip solution did not include a post harvest fungicide which is necessary to prevent a high incidence of wastage following post harvest dipping.

EVALUATION OF BULK TREATMENT WITH ALCOHOL IN A CA. ROOM

GRANNY SMITH

Effect of Alcohol Treatment in a CA. Room on scald of Granny Smith Apples

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Alcohol treatment controlled scald for up to 6 months of storage however after 7 and 8 months of storage the incidence of scald increased to 10%. After 8 months of storage all fruit treated with alcohol had developed core flush.

Alcohol treatment controlled scald for 6 months

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DELICIOUS

Effect of Alcohol Treatment in a C.A. room on Scald of Red Delicious

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•Alcohol •C.A.

6 Months 7 Months

Storage Time

8 Months

Alcohol treatment controlled scald for up to 6 months storage however the development of skin discolouration after 7 months storage negated the benefits of scald control.

PACKHAM PEARS

Effect of Alcohol Treatment in a C.A. room on scald of Packham Pears

18 16 14 12 10 8 6 4 2 0

HAIcohol —Treatment BC.A.

6 months 7 months

Storage Time

Alcohol treatment controlled scald for up to 7 months storage when 16% of C.A. stored fruit had developed scald. After 8 months storage the pears had reached the end of their storage life with 80% of the fruit developing storage rots.

E:\applerep.DOC 21 28/01/99

22

RESULTS OF RESEARCH BY K.J. SCOTT OF THE DEPARTMENT OF FOOD SCIENCE AND TECHNOLOGY. THE UNIVERSITY OF NEW SOUTH WALES TO EVALUATE ALCOHOL TREATMENT FOR SCALD CONTROL.

There has been concern both in Australia and overseas that the use of diphenlyamine to control superficial scald may no longer be permitted. There have been unconfirmed reports that some coimtries have acted already to prevent the use of diphenylamine on apples for scald control. There is no proved alternative to the use of diphenylamine. Studies have been carried out for several years at the University of New South Wales to develop alternative (preferably natural treatments) for the control of superficial scald.

Early studies showed that exposure of Granny Smith £^ples to ethanol (the ordinary alcohol in alcoholic drinks) gave excellent control of scald. Similar control was also obtained by £q)pl)dng undiluted vegetable oil directly to the skin of the fiuit by hand.

There is a high excise tax (administrated by Customs) on food grade alcohol which is over 30 times the wholesale price. When this was realised, the HRDC project concentrated on developing a vegetable oil treatment. Application of oil direct to tiie skin by hand before storage was obviously unsuitable and emulsified oil treatment that could be applied using the equipment now used for DPA qiplication were studied.

The ethanol vz^our treatment appeared to have many advantages, it seems simple to apply and without the tax the cost would be less than DPA. The avoidance of dipping should greatly reduce the need for fimgicides and probably no fungicide would be needed. Ethanol has some fungicidal properties and this attribute should be a bonus. By using the &cilities at the University of New South Wales, K. J. Scott investigated the excise tax both in Australia and the U.S.A. and found that it was possible to obtain tax fiiee alcohol for scald control provided the alcohol was made undiinkable. This aspect required fiirther study to find an additive that did not effect the fruit. Such an additive has been found and has been successfully tested on Granny Smith. Funds were provided fiiom a HRDC project AP509 to re-start the programme on the use of ethanol vapour.

These studies have shown that complete control of superficial scald can be obtained without injmy or obvious off flavour on Granny Smith. However there was an imexpected result with Red Delicious. While scald was controlled, higher levels of pure ethanol induced an unacceptable change in the red colour. The flesh did not appear to be affected. Work aimed at preventing the objectionable colour change has begun. There are several aspects being considered. Firstly all Red Dehcious are now all virtually stored in C.A. This reduces scald so that the use of reduced amounts of ethanol may be adequate for scald control without inducing the colour change. Secondly, a pos^raduate student has examined the specificity of ethanol for controlling scald and has found that several higher alcohols are also effective, some more effective than ethanol. In a preliminary test low levels of one of these alcohols has controlled scald without inducing the colour change. These other alcohols occur in food, some in fiiiits and there is no problem with excise tax.

It is not possible to recommend the use of ethanol on ples at present xmtil ethanol and other alcohols are approved by health authorities. This is required for ethanol even though it is widely consumed in many coimtries. Before recommendations can be made for fiuit to be treated and then sold, health qiproval will need to be obtained both for the alcohols themselves and the denaturant rendering ethanol undiinkable. This will require analysis of residues afler fiuit are treated and again when sold. There does not pear to be any great

23

difiSculty in obtaining health clearance but it will take time and the analytical costs need to be met.

The denaturant is not considered toxic. When used at very low concentrations it renders ethanol undiinkable. When the denatured ethanol ev^orates in the C.A. room, the denaturant will not evzporaie at the low temperature and thus should not contaminate the atmosphere or the fiuit. The amount required is so low that even if the denaturant evaporated and was absorbed by the fiuit, it would be di£Gcult to detect its presence ia the fiuit even with modem chemical techniques.

Some people may be concerned at using a flammable substance ia their C.A. rooms. Although ethanol is flammable, a concentration of over 3% is required at room temperature. The amount required to control scald if ^plied at one time would not reach the flammable level. In fact, it is proposed to apply the ethanol over several weeks at low temperature and probably after C.A. conditions are established. These factors would further reduce any possibility of ignition.

The above information suggests that providing the red colour change can be overcome, there is a good possibility of developing a new commercial treatment fi)r preventing scald which is based on natural food substances. It is proposed to carry out a study on a commercial scale on Grranny Smith copies as soon as funds can be obtained. These studies would probably use mainly juice fiuit to reduce costs as fiuit could not be sold until health approval was obtained. A fiuther joint programme mvolving NSW, Victoria and South Australia is proposed and an plication for funds fix>m HRDC has been made through Department of Agriculture, Victoria.

24

REFERENCES

Little, C. (1990). Scald control methods under attack. Successful Horticulture, November 1990 (22-24).

Dilley, D.R. Air Separator Technology Development for Controlled Atmosphere Storage. Fifth International Controlled Atmosphere Research Conference Weratchee, Washington, 1989.

Cripps, J., Mackay, A. and Broughton, T. (1990) Apple varieties for Western Australian orchids. Bulletin 4169 ofWA Department of Agriculture.

Ben-Arie, R., Levin, A. and Zutki, Y. (1993) Elevated C02 for control of Superficial Scald on CA-stored Apples. Washington State University Tree Fruit Postharvest Journal Vol. 4, No. 2 - August 1993.

Patterson, M.E. (1993) Harvest and CA Storage Regime for Arresting Scald in Granny Smith Apples. Washington State University Tree Fruit Postharvest Journal Vol. 4, No. 2-August 1993.

Scott, K.J., Yuen, C.M.C. and Kim, G.H. (1995). Reduction of superficial scald of qiples with vegetable oils. Postharvest Biology and Technology, 6: 219-223.

Scott, K.J. Yuen, C.M.C. and Ghabramani, F. (1995). Etfaanol v^our - anew anti-scald treatment for ^ples. Postharvest Biology and Technology, 6: 201-208.

25

PUBLICATIONS AND REPORTS

Harvesting, handling and storage of new apple varieties - presentation to Lenswood/Forest Range growers, December, 1992.

New varieties - storage trial revelations. Seminars: Get It Right and Appeal to Bite, The Apple and Pear Growers Association of SA Inc., 1992, presentation by B.L. Tugwell.

New £^ple varieties - improvement in postharvest quality - p^per presented by Barry Tugwell to the Australian Institute of Food Science and Technology Convention -Adelaide, May, 1993.

Evaluation of harvest maturity, storage life and storage conditions for new ^ple varieties by Louise Chvyl and Barry Tugwell - presented to the Australasion Postharvest Conference - Gatton, September, 1993.

New q)ple varieties show breeding benefits by J Cripps, Barry Tugwell and Eleanor Melvin-Carter. Good Fruit & Vegetables, April, 1994.

Storage recommendations for new varieties by Barry Tugwell and Louise Chvyl. Pome Fruit Australia, p4-5. May 1995.

Harvesting, handling and storage of Red Fuji by Barry Tugwell and Louise Chvyl -presentation to National Seminar "Searching for Better Selections of Striped Red Fuji Apples", Huonville, Tasmania, May, 1995.

Gas levels critical for effective C.A. storage by Barry Tugwell and Louise Chvyl. Pome Fruit Australia, Jan-Feb 1996.

Harvest maturity key to successful storage by Barry Tugwell and Louise Chvyl. Pome Fruit Australia, Jan-Feb, 1997.

Predicting Harvest Dates by Bany Tugwell Pome Fruit Australia, p.9, March 1998.

Maturity tiie key to quality for Apples, Pears and Cherries by Barry Tugwell -presentation to Australian Apple and Pear Growers Conference "Integrated Frait Production" 1998.

A comparison of the effects of ethanol and higher alcohols for the control of superficial scald of apples by F. Ghahramani, K.J. Scott, K.A. Buckle and J.E. Paton - 1998 in press.

Maturity the Key to Quality for Apples, Pears and Cherries

By Bkrry Tligwell

Consumers expect to obtain a year round supply of attractive, crisp full flavoured apples and pears from storage or sweet juicy fresh cherries when in season.

Maturity is a critical factor in determining quality and consumer acceptability of fruit out of storage. Maturity not only affects fruit appearance but also deteriniries tiie rate of loss quality especially flavour and firmness.

Early maturing varieties generally have a shorter storage life, soften niore rapidly in storage and develop storage, disorders that spoil their appearance iind texture.

Guidelines for harvesting apples and pears at the correct maturity for storage have been established by storage trials, which in recent years were funded by the Horticultural Research and Development Corporation.

Maturity forecasting has for; 25 years provided South Australian growers with reliable harvest dates for the main apple and pear varieties in January giving growers time to arrange harvest labour and complete harvesting before early varieties become over-mature. Forecasts are based on temperature data from bud burst until the end of December, which provides an accurate prediction of seasonal variation in fruit maturity. Ideal harvest dates

for Jonathan and delicious apples have varied on a seasonal basis by up to 4 weeks.

Changes in some fruit quality characteristics which may be indicators of fruit maturity have been recorded for each apple and pear variety. Changes in background colour, sugar and starch levels and fruit firmness have been found to confirm maturity but actual values at maturity vary from year to year.

Measurement of fruit colour, sugar levels and firmness ate essentially quality factors for which minimum specifieatidns can be agreed with buyers. Depending on seasonal conditions these specifications may be recorded ahead of the ideal maturity for storage.

In order for growers to satisfy "customer specifications" for fruit quality on a year round basis I suggest adoption of the following strategies :-

• Plan your harvesting season based on maturity forecasts provided by SARDI in January.

• Do not store "off crop" or "light crop" from young trees it has a short storage life and rapidly loses quality in storage.

• Commence harvesting as the early ripening fruit reaches minimum specifications for

size, colour and flavour so as to i ensure the majority of the fruit is harvested at ideal maturity.

• Do not store fruit damaged by sunburn, or severely affected by water core (Fuji is an exception to this rule).

• Use the following quality guidelines for each variety to confirm suitabiUty for storage.

• Measure and document fruit I quality criteria on removal from storage to ensure compliance with customer quality specifications.

Cherries

• Flavour development only, occurs on the tree, sugar accumulation stops at harvest so "what you pick is what you j ge t !

• Harvest fruit according to colour development, this is the i most consistent and reliable indicator of maturity of red, cherries.

• Sugar levels vary from season to season but check to ensure compliance with minimum quality specifications.

Pears

• Pressure testing or finnness is| the best indicator of maturity.

• If fruit is of adequate size harvest Williams at 7-9kg and

Conference Proceedings 1998 - 65

Packhams and Buerre Bosc at 8-10kg.

Nashi- Nijisseiki

® Harvest when the background colour changes from green to green yellow as indicated by background colour charts.

• Check sugar levels at harvest, sugar does not increase during storage.

Royal Gala

• Background colour change from green to green yellow is a reliable indicator with an increase in sugar and some loss in finnness.

• Late harvested fruit rapidly loses flavour in storage.

• Storage beyond July is not recommended due to loss of flavour.

Jonathan

• Change in background colour from green to green yellow is the best indicator of ideal maturity for storage.

• Sugar levels do not change sufficiently to indicate maturity however a minimum specification of 12% is suggested for fresh fruit marketing.

Golden Delicious

• Harvest as for red delicious usually 2 weeks after Jonathan maturity.

« Harvest according to flavour as,

it changes from "starchy" to slightly sweet.

• Fruit colour is affected by seasonal conditions and is not a reliable indicator of maturity.

• Regularly check fruit firmness as an indicator of quaUty out of storage. Rapid loss of firmness is a characteristic of this variety.

Red Delicious

• Clearing of starch from the centre of the fruit combined with the development of "delicious" flavour coincides witfi maturity.

• Sugar levels increase during storage as starch converts to sugar. A minimum level of 10% is suggested for fresh marketing.

• Check firmness out of storage as an indicator of quality and customer acceptability.

Fuji

• Harvest 2 to 3 weeks after delicious when water core appears in about 50% of fruit sampled.

" Background colour from green to green yellow is also a useful indicator.

» Check sugar levels since sugar will not increase during storage. Consumers expect between 12 and 15% sugar in this variety.

Pink Lady

• Harvest during the last week of April when background colour changes from green to green yellow.

• Sugar levels increase during storage.

• Firmness is retained during storage but avoid long term storage of fruit from young trees.

Sundowner

• Harvest 2 weeks after pink lady when background colour changes from green to green yellow.

• Sugar levels increase during storage and firmness is well maintained.

Granny Smith

• Fruit is harvested between 2 and 4 weeks after delicious based on "green" colour.

• Best flavour results from harvesting fruit during the last week in April however market specifications require green coloured fruit to be harvested up to 2 weeks earlier.

Summary

In order to satisfy customer specifications for quality fruit growers should plan harvesting according to forecast maturity dates for each variety, check for changes in maturity indicators and measure and record quality specifications at harvest and on removal from storage.

66 - Conference Proceedings 1998

HARVEST '<;:'

by Barry Tugwel, Chief Scientist, Horticulture South Australian Research and Development Institute (SARDI)

1 I he recent benchmark ing study of the

I Austral ian apple and pear industries

established that harvest maturity is a key

factor in supplying consumers with crisp full

f lavoured apples and pears.

In order to harvest fruit at the peak of

maturity growers need to commence

harvesting at least a week before opt imal

maturity to complete harvesting for early

varieties within a two week harvesting window.

Maturity indices such as sugar and starch

levels, fruit f irmness, and changes in

background co lour can conf i rm maturity but

give no advance warning on when to harvest.

South Austral ian apple and pear growers

have for 25 years p lanned hol idays,

scheduled maintenance work and ar ranged

harvest labour based o n the predicted

harvest dates for early varieties of apples and

pears which are made avai lable by SARDI

dur ing early January each year.

A project has been submitted to the

Hort icul tural Research and Development

Corpora t ion to Implement the forecast ing

system in all major Austral ian app le and

pear product ion areas dur ing the 1999

harvest season and at the same t ime

demonstrate the value and l imitat ions of

apple maturity criteria in conf i rming maturity.

If you, as apple and pear growers believe

that predicting seasonal variat ion in harvest

maturity up to two months ahead of t ime is of

value, make sure you talk to your

representatives on the HRDC research

commit tee or if you want more informat ion

talk to South Austral ian app le and pear

growers about the reliability and value of

predicted harvest maturity,

The project "Prediction and Mon i to r ing for

the Determinat ion of O p t i m u m Harvest

Matur i ty" has been submitted by Dr G o r d o n

Brown from Tasmania in co l laborat ion with

Michael Rettke, Barry Tugwell and Louise

Chvyl f rom SARDI who have 70 years com­

bined experience in assessing apple maturity.

ACTION PLAN FOR 1998 APPLE HARVEST

<i Variety 1998 Estimated Harvest Date for L o n g - t e r m

Storage Apples: Royal Gala 16 February Jonathan 2 March Delicious 16 March Fuji 6 April Pink Lady first week May Sundowner mid-May Lady Williams mid-June (or May

if Ethrel is sprayed) Pears: Williams last week January Packhams/Bosc first week March Others NashI (Nijisseiki) kist full week February

Already the year is running awtiy f rom us -

the op t imum maturity harvest date In 1998

fo r Jonathans f rom the Lenswood area ,

Intended for long term storage is 2 March .

A l though the green tip date of 15 September

1 9 9 7 was three days later than that of last

year the growing season has overall been

milder and Oc tobe r and November

especially have been warmer.

Harvesting for long term storage of

Jonathans should commence in the last week

of February and be completed during the

second week of March In the Lenswood

district.

Growers with light cropping or young trees

cou ld be caught very soon as fruit f rom these

trees will mature up to three weeks earlier,

while trees at lower altitudes than Lenswood

may mature up to one week earlier.

Because of the shorter growing season and

the consequent lack of cool nights, fruit may

not colour or size up as much as would be

liked to enable easy maturity assessment.

Growers should watch the change in

background co lour on Jonathans during the

second half of February and commence

harvesting when the colour changes f rom

green to green-yellow.

Royai G n i o are ready in the middle of

February when they show adequate co lou t

and size but growers need to undertak^

several picks to avoid mixed maturity.

Del ic ious apples will be ready on 16 March

with harvesting possibly starting up to one

week earlier when they have lost some o |

their starchy taste and some sweetness one

Delicious f lavour can be detected.

w I I I e

I The harvest of Fuji apples should peak on ^M

Apr i l , having started in the first week and be

finished in the week leading up to Easter. Fuji

apples are ready for harvesting when a b o u j

5 0 per cent have signif icant water core.

As usual. Pink Lady will be ready to harvest in

the first week of May when the background

colour changes from green to green-yellov]

and a decrease in firmness occurs. Fruit fron

young trees will mature up to two weeks earlier

In the week leading up to Anzac day.

Sundowner ready in m id -May will also show

a change In background colour, a long with i

loss of starch f rom the centre of the fruit.

If the Lady Wi l l i ams have been sprayed wit l i

Ethrel® to advance maturity and avoid

unfavourable weather effects, their harvest

overlaps with those of Sundowner and Pinli

Lady over May. Without an Ethrel spray Lad j

Wi l l iams naturally mature In mid-June.

1 P

nd

° 1 ' a r

I w

1 I iSt

1 I ut

1 ]rs

1

I hope growers of W i l l i ams pears meant fo

storage are already harvesting, or are about

to , as they are ready In the last week

January when they have a pressure of 8-

kg . The Packham and Buerre Bosc pears

mature In the last week of the Jonotha

harvest - the first week of March , with

pressure of 7-9 kg.

Nashi or Nijisseiki pears are ready to ha rvesH

in the last week of February.

Temperatures will still be quite high at t h l H

early harvest t ime so care should be taken to

coo l fruit as quickly as possible. The heat wi

increase the rate of moisture loss resulting i

shr inkage, loss of quality and loss of dol lars. I

The above infomiation is jointly funded by the Horticultural Research and Development Corporation and the apple and pear industr/'s R&D levy. I I