“Written by Dr Malcolm Dodd (Cold Storage Solutions) & Samapro Trading”
The fresh produce group called berries (Blueberry, raspberry and strawberry) have different respiration classifications. Blueberries (Vaccinium spp.) and blackberries (Rubus spp.) have a climacteric fruit ripening behaviour (as do pome fruit) but others such as strawberries (Fragaria spp.) are non-climacteric.
This classification of the respiration pattern during ripening is internally driven by the ripening plant growth regulator called ethylene. The role ethylene plays in these respiratory behaviours was first described in 1960, with it being shown that the climacteric fruits experience a rise in ethylene production prior to an increase in respiration rate. The non–climacteric fruit do not experience this climacteric rise in ethylene when the respiration rate increases.
However, and this is very important to note, that this does not mean that low ethylene producing climacteric fruits, such as berries or the non-climacteric fruit varieties such as strawberries do not respond to the presence of ethylene in the storage air. The ISHS 7th International Postharvest symposium presented an interesting paper illustrating the benefit of removing ethylene from the air during the storage strawberries…. the simple finding was ….an increase in shelf life being reported through this simple technique of scrubbing the storage atmosphere.
At this stage it is important to also realise that whenever any fruit is bruised or damaged the response of the subtending fruit tissue is to produce ethylene. This then stimulates further ethylene production in an auto catalytical process and so the ripening process is accelerated. Similarly, fungi which cause post harvest disease, when present as spores on the surface of fruit, are stimulated to germinate by ethylene and other volatiles. Research has shown that by “scrubbing” the air in the storage environment to remove ethylene and volatiles results is a lower incidence of postharvest disease breaking out. In addition by removing ethylene from whatever source, from the berry storage environment by scrubbing the air with ethylene filters, the risk of fruit ripening being accelerated will be reduced. This will ensure that the berry fruit will not soften too quickly nor develop post harvest infection due to fungi. Maintaining a proactive approach to post harvest treatment of fruit by scrubbing the air at all stages is simply translated into the berry fruits shelf life marketability being maintained for longer along with the resulting better value of the product.
The most important means of managing postharvest life of berries is to remove the field heat as soon as possible after harvest and maintain the temperature as close to set point as possible, preferably at a relative humidity of between 90 to 95%. Scrubbing ethylene from the storage air will complement the fruit quality maintenance during refrigeration and packing .
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