A new technique that uses short bursts of low oxygen to prolong the life of organic fruit could see costs of organic produce drop close to those of the conventionally grown variety.
The big price difference between organic and conventionally grown produce means that going organic is something that only the most well off among us can afford. For example, organic apples currently cost the consumer about twice as much as their conventionally grown counterparts (see box below).
One of the reasons that organic is so much more expensive is because the storage and shelf life of organic food is shorter than non-organic, according to Claudia Ruane, spokesperson for Abel & Cole organic produce retailers. With some organic fruit and vegetables, there can be large losses [during storage], she said. And although many organic farms do have reasonably sophisticated refrigeration units, these may only be used for a few days while awaiting collection. These are costly but if paying out for these facilities can ensure a whole crop is not rejected by a retailer because it is a little limp or dehydrated, then it is a cost that has to be absorbed, she added.
Conventionally grown fruit like apples last longer on the shelf because they are treated with chemicals like diphenylamine (DPA) or 1-methylcylopropene (1-MCP). These help prevent the formation of scalds, a type of chilling injury that occurs when fruit is held in cold storage. However, organic produce cannot be treated with chemicals, as doing so would mean they are no longer organic. Therefore cheap and effective non-chemical alternatives are needed.
Currently, the only effective treatment that prolongs storage of organic apples is low oxygen stress followed by exposure to a controlled atmosphere (0C and low oxygen, normally obtained by continuous flushing with N2). But maintaining these conditions is very expensive, which means that it is not widely used.
Now scientists have devised what they expect to be an equally effective but cheaper technique. Edna Pesis and her team at the Volcani Center, Israel, found that a simple week-long pre-treatment with low oxygen (LO2-20C) at 20C is sufficient to keep apples in cold storage for up to eight months without scald formation (Journal of the Science of Food and Agriculture DOI: 10.1002/jsfa2873).
Granny Smith apples were sealed in jars and flushed with nitrogen until the oxygen concentration dropped to 3% (compared to 21% in normal air), and kept at 20C for seven days. Once removed from the treatment jars, they were stored in cartons at 0C for up to eight months, under normal oxygen concentrations.
Pesis observed a 100% loss of fruit after six to eight months when apples were stored without this treatment. However, 90% of apples subjected to the new low oxygen treatment were saved from the scald problem in addition to other physiological diseases, according to Pesis.
Pesis said that the technique may also prove applicable to avocados, tomatoes and other organic produce.
An apple a day costs...
At time of going to press, conventionally grown Braeburns cost 25p each in Sainsburys compared to 44p each for the organic fruit (when bought in a bag). Conventional Fujis cost £1.49/kg, compared to £3.13/kg for organic Fujis. Waitrose organic Gala apples cost nearly 50p each compared to just over 26p for the conventionally-grown apples. Braeburn apples are £1.99/kg, over a pound cheaper per kilo than the organic at £3.11. In Tesco, a bag of organic Gala apples cost £1.99 while a standard bag costs £1.29. Tescos organic Pink Lady fruits cost approximately 50p each compared to 33p per non-organic apple.
Prices correct as of 30/5/07 (some calculated from pack prices) on www.tesco.com, www.ocado.com, www.sainsburystoyou.com