Carlos Cruzat, Chilean Kiwifruit Committee
This was roughly the outline of the seminar organized by the Chilean kiwifruit committee in Ridderkerk, close to Rotterdam, last week.
One of the speakers featured at the seminar was Dr. Juan Pablo Zoffoli, professor of Physiology and Postharvest Technology of the Agriculture and Forestry faculty of the Catholic University, who has been leading a research teams for years and has taken on these challenges. This has led to the ripening protocols that are now in the process of implementation by the companies associated with the Chilean kiwifruit committee. All findings presented at the seminar and in this article are credited to the research of Zoffoli and his team.
The bottlenecks faced by the industry, are that the consumer often has the experience that the fruit takes two weeks to ripen at home. Problems for operators in the supply chain are often that the fruit is inconsistent in firmness and quality in the sense that in certain boxes, there may be a number of considerably more soft fruits, while the rest is harder.
The traditional solution from the perspective of receivers has been to ask for fruit with a firmness of around 10 or 12 Lbs. In order to maintain this, the fruit is harvested relatively hard and subsequently stored and shipped at temperatures varying between 0 and 1 degrees Celsius. However, this level of firmness in practice doesn’t help prevent the occurrence of the problems described in the previous paragraph. So what goes wrong and how can this be overcome?
To start off with the objective of reaching a fruit that is ripe and ready to eat on the consumers table, it’s important to note that the taste of kiwifruit is decided by the content of Soluble Solids (SS) and Acidity (TA). The level of SS has to be sufficiently high (12.5% or higher), as these contain the sugars that bring the sweet taste to the fruit, and the AC has to be sufficiently low (well below 1.17%), as this causes the sour taste of the fruit.
However, what decides the effective levels of these two parameters, is the level of ripeness of the central column of the fruit.
It’s important to observe that kiwifruit differs considerably from other fruits that need to ripen after shipping, like bananas, mangoes and avocados, as in that the starch and dry matter (DM) aren't distributed equally throughout the body of the fruit. Interestingly, SS and AC can be measured before harvesting, but both have been found to be unreliable indicators of the expected trajectory of firmness of the fruit through the supply chain. The level of SS at harvest doesn’t correlate well with the level of SS at ripen state.
However, the level of starch content (the Dry Matter), which can also be measured before harvesting, actually is a reliable indicator. It has been found that when the DM content is at least 15.5% at harvest, the level of SS when the fruit reaches its ripe condition is at least 12.5% or more.
Dr. Juan Pablo Zoffoli, professor of Physiology and Postharvest Technology of the Agriculture and Forestry faculty of the Catholic University
These findings mean that there is a reliable handle on when to harvest fruit to create a product with the right organoleptic characteristics when on the consumers’ table. The key however, is how to ship and store this product in the supply chain in a way that maintains uniform quality and avoids loss. In this respect it is important to note that when kiwifruit in transit is kept at a pressure of 10 Lbs it is susceptible to temperatures lower than -1 degrees Celsius. In fact, shipping and storing between zero and minus one degrees, will often lead to cell tissue damage, which in turn leads to the inhomogeneous qualities of fruits in the box, as some will have damaged cells. This results in fruits that go soft and dry, without actually being ripe. Their cell structure simply collapsed due to the prolonged exposer to low temperatures.
However, when the firmness in receivers storage of the fruit is lowered to 4 Lbs, the susceptibility of the fruit to cold damage actually decreases and the resulting quality of the lot is actually higher and more uniform than when the fruit is kept in a more firm condition.
The question that rises of course, is weather fruit of 4 Lbs still has sufficient robustness and expected storage and shelf life to be a workable fruit. Yet the answer to this is: yes. In fact, when the firmness of the fruit is 4 Lbs while at the receivers warehouse, it will still have a storage life of 45 to 60 days at a temperature of zero degrees, while reaching a firmness of 2 to 3 Lbs when reaching the consumers table. The fruit will be ripe and ready to eat in one or two days. The problem is reaching that level of 4 Lbs. When harvesting at a firmness of 18 Lbs, and storing at 0 degrees, it would take 4 months for the fruit to soften to 4 Lbs.
However, the Kiwifruit Committee has developed ripening protocols with certain levels of temperature and ethylene concentrations over variable periods of time, that will bring the fruit to the right level of firmness to be and stay around 4 Lbs throughout storage and distribution in Europe. This could be reached by applying a ripening treatment of no more than a day after the fruit arrives in Europe or by pre-ripening the fruit before shipping to Europe.
In short, when the Chilean kiwifruit supplier is trusted to harvest at the right level of firmness and dry matter, and the correct pre-ripening treatment is applied between exporter and receiver, the receiver can deal with a reliable fruit for a period up to 60 days, while consumers get their ready to eat fruit with high sugars and supermarkets get their short rotation cycles.
For more information about the kiwifruit committee and the ripening protocols it has developed, feel free to contact its president:
Carlos Cruzat
Chilean Kiwifruit Committee
Tel: +56224724783 or +56998254204
[email protected]
