Post Harvest Protocols for New Kiwifruit

Three new kiwifruit cultivars have been released to growers by ZESPRI and in the build up to commercial crop loads, Plant & Food is developing postharvest protocols to make sure consumers get the best quality and growers get maximum returns.

Making sure NZ’s fresh produce gets to market with the best quality and freshness is important for retaining a premium position in the export market.

This is especially the case when the kiwifruit export crop has a six-week voyage to get it to European markets.

Each cultivar has its own postharvest personality so optimising postharvest protocols isn’t a one-stop-fits-all approach.

In June 2010, ZESPRI® Group Limited announced the commercialisation of three new kiwifruit cultivars developed by Plant & Food Research.

The three new commercial cultivars are

– two yellowfleshed varieties – an early season and potentially long-storing

– a new sweet green-fleshed kiwifruit.

The three new cultivars were chosen from 50,000 new varieties developed in the Plant & Food Research kiwifruit breeding programme. From this, 10,000 were initially selected, 40 went to growing trials and four were finally selected for on-orchard trials. The extensive screening included on-orchard, storage, shipping and taste tests.

The two new yellow-fleshed cultivars were developed specifically to widen the market window for New Zealand-grown ZESPRI®GOLD Kiwifruit. The early season cultivar is predicted to enter markets up to three weeks ahead of the existing variety, with the long storing variety expected to extend availability through the winter.

The new green-fleshed variety has the potential to establish a new market segment, with the sweet taste possibly appealing to new kiwifruit consumers.

Plant and Food tries to integrate their science with industry best practice to establish protocols for each cultivar.

They look at harvest timing, when the fruit comes to maturity – how that can be controlled and manipulated. What is ideal maturity? How to store and for how long can we store ? what are CA (controlled atmosphere) protocols? The use of ethylene treatment systems to delay or speed up ripening.

There are a large number of storage and CA facilities at Plant and Food – so a range of post harvest protocols can be trialled. The fruit is also tested for firmness and sweetness.

Among the challenges for longer term storage of the current kiwifruit cultivars is minimizing flesh softening after harvest. Flesh softening occurs rapidly during the first few weeks of air storage.

Controlled atmosphere is already used successfully with kiwifruit – but with existing cultivars there is research suggesting that should happen no later than 1 week after harvest… how do the new varieties respond to CA ?

Clearly there are a number of protocols in place for the two main varieties exported already – Gold and Green – but scientists want to see what the requirements of these new varieties are.

The researchers are also interested in how the fruit tastes and smells. It’s no good coming up with a protocol that keeps the fruit for 3 months if it doesn’t taste good when it is released – or has some strange after-taste.

With some fruit a short period of storage was beneficial to fruit quality, Flavour intensity was enhanced, and off-flavours, greenness and acidity were decreased.

Fruit stored at higher or lower temperatures may suffer in sweetness or acidity or produce off flavours.

The science around this is all about proofing the protocol with the sensory qualities of an eating-ripe fruit.

To that end they assemble a sensory panel to taste test fruit and rate it. This will be taking place while we are at Plant and Food.