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Italy: The many negative repercussions of harvesting kiwis too soon


The problem for kiwis in September is avoiding the introduction of fruits on the market when it's too early. To better understand the negative effects of this phenomenon, we talked to professor Raffaele Testolin (in the photo) from the University of Udine, who also selects and develops promising cultivars.

Every year, the kiwi sector establishes some ground rules as regards Brix levels and dry matter content, but they are always disregarded. "The first problem is that these rules are established for green kiwis (i.e. a Brix level of at least 6.2°), while many harvest golden ones following the same parameters, which are thought insufficient." What we mean is that, while a Brix level of 7° is considered excellent for green kiwis, golden kiwis need to have at least 8° Brix.

The second problem is the lack of checks to monitor the parameters established by the interbranch organisation. Such checks should be carried out especially in September and until early October. Not to mention that almost all the kiwis that are harvested too early are destined for export, damaging the image of the entire sector.

Negative repercussions
"These practices lead of course to poor quality, as consumers don't like the fruit due to its herbaceous flavour and grainy texture. Harvesting too soon means kiwis do not reach a sugar content suitable for consumption (around 14° Brix, for example). In addition, shelf-life and texture during storage are also affected, with weight losses exceeding 5% in cold storage units."

"What is more, fruit that is harvested too early is unsuitable for long-distance trips and is more likely to be contested. It is also more easily attacked by mould (e.g. Botrytis) and rot, leading to further losses for producers." 

All this data has been collected through a series of experiments carried out on green Hayward kiwis, but the same results were confirmed for new golden varieties as well. 

"As regards golden kiwis, we also need to talk about flesh colour, which tends to remain greenish if the fruit is harvested too soon. The de-greening process (i.e. the degrading of chlorophyll and the development of a yellow colour) is still at the start and it may not complete."


Negative effect of early harvesting on golden kiwis: (above) fruits harvested at 7° Brix when ready for consumption. The incomplete degradation is evident. (Below) Fruits harvested at 8.5° Brix when ready for consumption. The colour is perfect.

The dry matter question
Dry matter content was introduced as a quality parameter by the New Zealanders, but it's actually not an indicator of when fruits are ready for harvesting.

Professor Testolin stresses that a high dry matter content reflects a positive season for plants and their fruits. In other words, if kiwis are cultivated well (non-excessive fruit load, well-balanced fertilisation, good pollination and light etc.) and the season was good (many sunny days, high temperatures etc.), then dry matter content will be high regardless of when they are harvested. A low dry matter content only means that incorrect cultivation techniques were carried out or that the season wasn't particularly favourable. Dry matter content is not really influenced by harvesting and is therefore not a suitable indicator.

"Quality recommendations establish that dry matter content should be 15%, but often kiwis reach this percentage before they develop the Brix level required. Therefore, if dry matter content is used as a parameter for harvesting, the quality of the fruit will be low."

In addition, it is not possible to establish a single harvesting date as ripening can vary between 20 and 30 days depending on the season.

The bacteriosis situation

"While we thought that bacteriosis was being contained in 2016, there was an upsurge in 2017 that affected even the Hayward variety, which we thought was more tolerant. Bacteriosis affected more or less all areas except Calabria, which should take all precautions so as to remain unaffected."

"Volumes will be lower, but fruits should be of a better quality, which is why it would be worth to wait for the perfect moment to harvest and have a shorter season in line with the lower volumes available."

The market is becoming increasingly crowded, as explained during the IX International Kiwi Symposium held in Portugal a few days ago. Testolin says that, although China is expanding its kiwi orchards, it may still not be a source of worry for operators in the northern hemisphere.

"The Chinese reassure us that, for at least 10 years, most of the domestic production will be used to meet the increasing domestic demand and that there is actually room for imports." Nonetheless, 10 years might not be as reassuring for professional operators.

Other operators becoming more and more important on the kiwi market are Iran and Turkey, while the most interesting areas for exports are Eastern European and Arab countries, where domestic production doesn't meet consumption demand, which is still low but might increase over the next few years. 

Finally, as regards varietal innovation, Uni Udine has two breeding programmes with interesting selections that will soon be issued. "We have five new selections of green and golden varieties which we would have released before, if bacteriosis had not dampened the spirits."

Publication date: 9/18/2017


 


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