SmartFresh^SM Quality System is commonly applied to apples in the UK and throughout the world to maintain harvest attributes. It is an important supplementary measure to good storage practice and is particularly effective in maintaining the quality of fruit in-store and during subsequent marketing and distribution.

Extensive research was carried out at East Malling Research (EMR) from 2000 onwards under the sponsorship of Rohm and Haas. Most of the research at EMR was done on Bramley, Cox and Gala. SmartFresh^SM was approved for use on UK apples in September 2003. Since that time there has been considerable commercial experience with the product and there are now recommendations for its use with the following apple varieties in store: Bramley, Cameo, Cox, Egremont Russet, Empire, Gala, Golden Delicious, Jonagold, Rubens and Spartan.

The active ingredient of SmartFresh^SM is 1-methylcyclopropene (1-MCP) a potent inhibitor of ethylene action in plants. As it is very similar in its chemical structure to ethylene, it binds preferentially with ethylene receptors in the cells of the fruit at the beginning of fruit storage. Consequently, for a period after  SmartFresh^SM application, apples are insensitive to ethylene and consequently ripening events are retarded.

SmartFresh^SM is formulated as a powder that releases 1-MCP when mixed with water in the storage room. The process takes about 24 hours and does not leave any detectible residue on the apples or in the environment.

The application protocol decided universally for apples, based on work done in the UK and elsewhere, is 625 parts per billion of 1-MCP (calculated for empty store volume) applied for 24 hours with minimal delay between harvest and application.

SmartFresh^SM applications are now subject to legislation which came into effect in 2017, whereby applicators must be suitably qualified and certificated to undertake storage treatments. Landseer as nominated agents of AgroFresh are trained to meet these standards and ensure applications are carried out to meet product stewardship requirements.

Once the suitability of the rooms has been determined, commercial applicators are prepared with an amount of SmartFresh^SM that is appropriate for the volume of the store to be treated. Water is added and circulated through the SmartFresh^SM via an integral battery-driven pump. The applicator is then inserted into the sealed store where it remains for approximately 24 hours. After treatment the store is operated normally.

The latest recommendations for how long different apple varieties will store after being treated with SmartFresh^SM are found in the Optimal Storage Conditions chapter of this guide.

Results of SmartFresh^SM research done at EMR are summarised in reports of EMRA Members’ Days on Top Fruit Storage (Johnson and Pearson, 2002; 2003) and elsewhere (Johnson, 2008). The benefits of SmartFresh^TM for the main UK cultivars as determined from research done at EMR and from commercial experience are summarised below.

 

Cox’s Orange Pippin (and clones) – benefits

• SmartFresh^SM application provides a significant (>2-fold) extension to the storage life of fruit held in refrigerated air storage.
• A combination of a lower storage temperature (1.5^oC) and SmartFresh^SM application was particularly beneficial to the quality of air-stored fruit.
• SmartFresh^SM application consistently improved retention of firmness and reduced weight loss in store.
• Occasionally SmartFresh^SM application resulted in reduced yellowing, higher soluble solids and acidity levels and less bitter pit.
• Greatest effects of SmartFresh^SM application were achieved on fruit picked at the correct stage of maturity for medium to long-term storage.

 

Cox’s Orange Pippin (and clones) – constraints / limitations

 

Stem end russet browning

In some commercial consignments of Cox treated in the UK and also in New Zealand the russetted areas of the fruit have darkened in response to SmartFresh^SM application.  This is known as stem end russet browning.

• The precise cause of the disorder is unknown although it has been hypothesised that 1-MCP causes a stress response in the skin cells which leak cell contents that are rapidly oxidised to brown coloured compounds (McCormick and Streif, 2008).
• Development of browning symptoms is inhibited by low temperatures and low oxygen conditions so fluctuations in temperature or atmosphere after treatment should be avoided.
• Commercial experience also suggests that early picked fruit are particularly at risk from stem end russet browning.
• Tables of storage conditions for Cox contain information to remind growers of practices that minimise this disorder.
• It is advised by the suppliers (Landseer Ltd.) that SmartFresh^SM application should be restricted to fruit where starch coverage is 70% or less.
• This is to minimise the effects of stem end russet browning and encourage fruit above 75% starch and a pressure greater than 8.6 kg to be stored for March marketing without the use of SmartFresh^SM.

Core flush

Perhaps the most significant adverse effects of SmartFresh^SM is the increased susceptibility of stored fruits to core flush and flesh breakdown which has important limitations on the storage life of Cox stored in CA conditions.

• In air storage, core flush was evident in fruit treated with SmartFresh^SMafter 90 days but not after 60 days.
• It is difficult to set a precise termination date for air-stored Cox apples treated with SmartFresh^SM.
• It is currently advised that marketing should be concluded in December although regular monitoring of fruit condition will help determine more precisely the termination dates for particular consignments.
• The life of Cox apples treated with SmartFresh^SM and stored in CA conditions is limited by the development of core flush and flesh breakdown.
• The termination month for treated fruit is set at January but it may be possible to extend storage of some consignments, particularly in years where climatic conditions have conferred a low potential for core flush and low temperature breakdown.
• It is possible to make a general assessment of risk based on seasonal weather (Johnson and Ridout, 1998) but careful monitoring of the condition of the stored fruit is required to determine when to conclude storage.

 

The storage of SmartFresh^TM-treated Cox beyond January

Growers wishing to extend the storage of SmartFresh^SM-treated Cox beyond January are advised to store in CA conditions of 1.2% O₂ and <1% CO₂ and to ensure that fruit temperature is above 3.5^oC in all parts of the store.

• Carbon dioxide levels should remain below 1% for the entire period of storage i.e. from the day of sealing the store.
• The practice of allowing carbon dioxide levels to rise initially after store loading is to be avoided.
• In previous work pre-treating Cox apples with high concentrations of carbon dioxide for 15 days prior to low ethylene, low oxygen storage increased core browning and flesh breakdown (Stow, 1990).
• In view of the general heightened sensitivity of SmartFresh^SM-treated apples to carbon dioxide and low storage temperatures it seems sensible to adopt the strategy suggested for storage beyond January until further work can be done to optimise store environment parameters for maximum storage life of Cox.

 

 

Bramley’s Seedling – benefits

The effect of SmartFresh^SM in retarding scald development is the most commercially significant effect. For long-term storage, SmartFresh^SM should be applied within a minimum of 7 days of picking and within the early part of the harvest window. Bramley apples treated with SmartFresh^SM and stored in conventional ventilated CA conditions (9% CO₂ + 12% O₂) should remain free of scald until March and those stored in scrubbed low oxygen (5% CO₂ + 1% O₂) should remain free of scald until July. For storage up to August, the fruit must be treated within 3 days of picking in the early part of the harvest window and have a dark green background colour.

• SmartFresh^SM application consistently improved retention of firmness and reduced weight loss in store.
• SmartFresh^SM application provided greener, more acid fruit that were less susceptible to superficial scald and bitter pit.
• Occasional beneficial effects of SmartFresh^SM application included higher soluble solids in the fruit and reduced incidence of senescent breakdown and core flush.
• Greatest effects of SmartFresh^SM application were achieved on fruit picked at the correct stage of maturity for long-term storage.
• Growers should continue to select for long-term storage those orchards that comply with recommended standards for fruit mineral analysis.
• Regular and rigorous monitoring of the condition of fruit from store is essential and should include a shelf-life test to provide an indication of scald potential.

 

There is significant orchard variability in the quality of Bramley apples treated with SmartFresh^SM (Johnson, 2008) which demonstrates the need to maximise storage potential through attention to pre-harvest factors (see Sections 1, 2 and 3).  To minimise scald risk in Bramley there should be no more than 3 days between picking and application and fruit should stored in a scrubbed low oxygen regime.

 

Bramley’s Seedling – constraints / limitations

Bramley apples are susceptible to external CO₂ injury when stored in recommended CA conditions with or without SmartFresh^SM.

• It is necessary to delay the establishment of CA conditions in order to alleviate the problem (Johnson et al., 1998).
• Application of SmartFresh^SM  caused CO₂ injury in Bramley apples stored in 5% CO₂ + 1% O₂ (5/1) despite a 10-day delay in establishing CA conditions.
• For SmartFresh^SM treated fruit, it is recommended that the delay in establishing CA conditions is extended to 21 days.
• During this period the oxygen concentration in 5/1 stores can be allowed to decline to 10% but the CO₂ concentration should be scrubbed to <1%.
• Delay in establishing CA conditions would normally be considered to conflict with best practice but it is necessary to ameliorate the risk of CO₂ injury in Bramley apples.
• The consequences of any delay in terms of reduced storage potential / quality are minimal in SmartFresh^SM-treated fruit as the ethylene production and ripening processes are slowed immediately after application.

 

Gala (and clones) – benefits

• SmartFresh^SM application consistently improved retention of firmness of air-stored fruit and virtually eliminated softening in CA-stored fruit.
• SmartFresh^SM application reduced weight loss in air-stored fruit.
• SmartFresh^SM suppresses the development of skin greasiness.
• Some preliminary investigation in AHDB Project TF 221 indicated potentially improved flavours from higher levels of oxygen in the store (3% CO₂ + 2% O₂).
• Further investigation continues in Project TF 225 ‘Developing practical strategies to improve quality and storability of UK apples’. This research aims to identify best practice that needs to be adopted to extend the market window opportunities for English Gala.

 

Gala (and clones) – constraints / limitations

• No adverse effects of SmartFresh^SM application on CA-stored (<1% CO₂ + 1.2% O₂) fruit.
• SmartFresh^SM application aggravated core flush and flesh breakdown in fruits stored in air at 0-0.5^oC for 180 days. The storage of SmartFresh^TM-treated fruit in refrigerated air should be terminated in January.

 

Egremont Russet – benefits

• SmartFresh^SM application improved the quality of fruit stored in air and CA conditions.
• Fruit treated with SmartFresh^SM prior to air storage for 90 days remained firm and free of scald and other disorders. However, extending storage in air to 180 days proved too long for SmartFresh^SM-treated fruit with fruits being affected by rotting, scald and internal disorders.
• The storage of SmartFresh^SM-treated fruit in refrigerated air should be terminated in December.
• SmartFresh^SM application improved the firmness and reduced the development of breakdown and core flush in fruits stored in CA (5% CO₂ + 3% O₂) for 180 days. Termination dates for CA-stored fruit are similar for fruits treated or not treated with SmartFresh^SM .
• Since Egremont apples produce very high levels of ethylene the application of SmartFresh^SM should be carried out as soon as possible after harvest and preferably within 3 days.
• Where SmartFresh^SM has been applied to commercial stores of Egremont Russet improved control of bitter pit was evident in fruit picked at the mid-point of the harvesting ‘window’ and stored under appropriate CA conditions.

 

Egremont Russet – constraints / limitations

• There are concerns about the flavour quality of early-picked SmartFresh^SM-treated fruit removed from CA storage before Christmas.
• Consequently SmartFresh^SM should not be used on early-picked fruit for pre-Christmas marketing.

 

Other dessert cultivars of apple

Only limited research has been carried out at EMR on other dessert cultivars although commercial experience of the effects of SmartFresh^SM application is increasing. Lack of response in some of these preliminary trials may be due to harvesting fruit too late or removing fruit from store too early when untreated fruit may not have softened sufficiently to establish any potential firmness differences. For the latest information on the use of SmartFresh^SM on UK-grown apples contact the supplier, Landseer Ltd.

 

Jonagold, Idared and Fiesta

• CA-stored fruit responded well to SmartFresh^SM application in terms of firmness retention.

 

Spartan and Meridian

• No significant response to SmartFresh^TM application in fruit stored in CA for 90 days at EMR.
• However, in commercial SmartFresh^SM applications carried out over the past four years a firmness benefit was found in both varieties.

 

Braeburn

• Although Braeburn responded well in terms of firmness retention, SmartFresh^SM application induced core flush in 75% of fruits.
• Since development of core flush currently limits the storage life of CA-stored Braeburn. It is clear that SmartFresh^SM application cannot be recommended for this cultivar.

 

Empire

No research has been carried out in the UK but it is clear from work done in the USA and Canada that SmartFresh^SM application exacerbates the risk of external CO₂ injury.

• It appears that SmartFresh^SM application extends the ‘adaptation’ period between harvest and establishing CA conditions (Razafimbelo et al., 2006) that is necessary to eliminate the risk of CO₂ injury.
• In response to the heightened risk of CO₂ injury due to SmartFresh^SM application, it is recommended that the CO₂ concentration for CA-stored Empire apples is maintained below 0.5%.
• Successful commercials applications of SmartFresh^SM have been made to Empire in the UK.

 

Other traditional dessert cultivars

The following cultivars were reported as showing a firmness increase following SmartFresh^SM application when stored in air until Christmas (Tully, 2003):

Lord Lambourne, Ribston Pippin, Kidds OrangeRed, Elstar, Chivers Delight, Ashmeads Kernel, Falstaff, Blenheim Orange, Jupiter and D’Arcy Spice.