Improved top fruit storage technology has extended the availability of fruit in the domestic market and has prolonged the English apple season. Since the beginning of commercial growing in the UK the evolution and innovation in storage technology and science has played a vital role for the retail chain.
When it comes to the storage potential of fruit, the last century saw scientific testing methodology develop to establish storage regimes that have allowed fruit growers in the UK to store fruit for longer. Whilst this science has been useful the fundamental rule of fruit growing is to grow a great product and to understand the history of the orchard it is grown in. Growers are able to create a framework of how each orchard is likely to store. There are other factors which come in to play such as aspect, soil quality and micro climates but it is quite likely that a grower will have a record of an orchard’s history and capability to be stored long term.
Growers in the UK do this very well and have a wide range of tools to help ensure the quality, flavour and properties of the fruit are not compromised if stored longer. Hand in hand with a grower’s experience and knowledge of his orchards comes the science. The mineral status of the fruit going into store is critical to the success of long-term storage. Fruit, which does not have the correct mineral balance will inevitably break down with internal disorders if stored beyond its capabilities. To gain an early indication of how well an orchard will store, samples can be taken in the fruitlet stage and analysed. This allows the creation of a draft storage plan. In this instance the historic record of an orchard’s mineral status and the known storage performance will give the grower and his advisor a head start in the planning process. Using this formula reduces the pressure to analyse all orchards just prior to harvest. However, it is the status at harvest, which is critical, and since weather patterns in the growing season can influence the mineral status, further testing will be carried out to confirm the storage capability.
On a small farm with detailed historic records, it is probable that taking samples pre-harvest is sufficient. But on a large unit with hundreds of acres and a multitude of orchard variables, the early sampling gives more time for adequate planning.
The first rule of storage is that you cannot store a fruit that does not have the right mineral content and potential and the second golden rule is picking it at exactly the right time.
This picking window is determined by a set of qualitative forecasts that are produced by Dr Martin Luton and FAST for The Quality Fruit Group funded by English Apples and Pears Ltd. The data has been gathered since 1994 and has become the industry bible over the past couple of decades. In 2011 due to climate conditions the English apple season was between two and three weeks earlier than usual and was hailed as ‘The earliest season on record’. Fruits began maturing both early and rapidly and the results of testing for firmness and starch were crucial.
The data supplied by the Quality Fruit Group during August and September provided analysis results in table format for growers to determine their picking windows for each variety and for the desired length of storage. Sometimes fruit is left in the orchard to mature on the trees for immediate market and orchards that have historically performed well in the past would be selected to go in to storage for selling the fruits in January, February and March. Other fruit would be selected for mid term storage for the autumn and Christmas market.
Dr Martin Luton from the Quality Fruit Group and Marden Fruit Show Society Judge explained: “The table will give the firmness in kilograms, the percentage of starch and the recommended dates by which picking should be completed. As a fruit matures and ripens the level of starch and its firmness decreases so calculating the optimum equation is an exact science.”
Growers during this time are testing their own fruit to identify the level of starch and firmness, the result is checked against the indicators. This is important as the aforementioned variables of soil type, aspect and micro climate can mean the orchards on a single farm may not follow the same maturity pattern each year. The test is taken from 20 individual fruits from random trees and repeated in each orchard. For example in a Cox apple for immediate market the starch would be less than 50% with a firmness of 6.5kg. If that same apple was going to be stored until December the starch would be 60% and firmness 8kg and if the grower wanted that apple to be sold in February and March the starch content would need to be 75% and 8.6kg firmness at the point of picking.
Apples have a limited life once they have reached eating maturity. This is because once ripe, they are physiologically programmed to deteriorate and become unpalatable very quickly.
The Marden Fruit Show Society hold a Long Term Farm Stored Competition each year and link the prize giving with the Annual General Meeting. This year the event will take place at East Malling Research Conference Centre on Wednesday 28th March. Samples are delivered to East Malling before the end of February where the apples are tested and judged by Karen Thurston, David Johnson and Martin Luton.
A total of 100 points are awarded, covering ground colour of skin, absence of shrivel or greasiness, firmness of flesh and the absence of disorders and rot. There are three classes; Bramley, Cox, Any Other Variety Dessert Apple. The fourth class is for pears, the judging criteria changes slightly to include ripening at 18°C and excluding greasiness, which is not a trait found in that particular fruit.
In the early days of the apple industry in the UK growers used a wide range of varieties with different maturity dates to maintain continuity of supply to the markets. The marketing management was determined by the fruits natural ripening properties and varieties that had a short shelf life were consumed soon after picking, and those that would remain palatable when stored at or near room temperature were kept for many months. Eventually even these became unpleasant to eat and apples were then not available until the next season.
Throughout the 20th century, the number of varieties grown reduced dramatically and was limited to a group more suited to refrigerated storage. The development of refrigerated coolstores in the early decades of the 20th century allowed the season to be extended until as late as Easter time. Some varieties were found to perform better in cool storage than others. The Cox apple had good store qualities and as such became the UK’s most prolific apple for a number of decades only to be surpassed this year by Gala.
Apart from a grower picking his fruit at exactly the right time for short, mid and long term storage the other vital component in the chain of events is to cool the fruit as rapidly as possible. The fruit needs to be refrigerated to slow down the ripening process and which type of refrigerated store they go to depends on when they will be sold. An air store is more or less a giant domestic fridge although the technology behind it and the computerised systems allow growers to maintain constant temperatures and test for the amount of gases the fruit gives off naturally to signal the ripening process.
Fruit that has been selected for mid and long term storage will begin a different storage regime in Controlled Atmosphere stores. These allow the grower to regulate the amount of gases in the store, which further helps to slow down the maturity process and also helps reduce post-harvest disorders.
Each month growers will select fruit from each store to make sure its natural behaviour is still as predicted and that the apples are on track to be stored for the initial predicted timescale. This is a skilled and dedicated job for the Store Manager who will be constantly monitoring the computerised data and making considered decisions. Regulating the amount of oxygen in a store is vital, different varieties behave in different ways and too much or too little oxygen can damage the whole store.
A display of the Long Term Farm Stored fruit with Judges scores will be at the Marden Fruit Show Society AGM on 28th March. Sarah Calcutt, Marden Fruit Show Society Chair explained: “the ability to store good quality English fruit is hugely important. The key for growers getting a good return for their fruit is dependent on the ability to deliver fruit to the consumer as and when required. With modern storage regimes we know how much fruit will be available months in advance and this is wonderful news for the industry. The competition fruit goes back in to store at East Malling Research and we take it to the ‘Living Land’ event in May where 3,000 primary school children get to try perfect samples of new varieties such as Rubens and Jazz almost 8 months after the fruit was picked.”