SFF Project Summary
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Updated: 16 February 2009
A Best Practise Guide for Improving Persimmon Taste is available for all registered growers, exporters and packhouses at the PIC website.
Report: Best Practice Guide [887K PDF]
Project description
Project aim is to improve taste in New Zealand persimmons by:
- increasing sweetness (Soluble Solids content (Brix))
- educing astringency (dry taste).
The issue/opportunity
New Zealand persimmon growers export 450-600,000 trays annually, mostly to Asian markets. New Zealand persimmons have good external appearance (bright orange colour, good fruit finish).
In recent years persimmons from Australia and South Africa have entered the market at the same time as New Zealand Persimmons. Fruit from these countries tend to be less visually appealing, but have superior taste.
Improving persimmon taste will increase repeat purchases of New Zealand fruit, improve grower returns, and maintain the industry’s international competitiveness and economic viability.
The context/background
PIC identified Taste Improvement as the highest priority for industry research and improvement following the 2003 season. Poor taste in this season reduced grower returns by $3 per tray.
This project is a major component of the Industry’s Strategic Plan to Improve Persimmon Taste.
Methods
Commercial evaluation and demonstration trials
- Evaluate different orchard management techniques for their effect on sweetness and astringency (eg open canopies, reflective mulches, and novel techniques such as growth regulators)
- Trials undertaken in 3 regions with key growers over 3 seasons with most promising techniques re examined in seasons 2 and 3.
Technology Transfer
- Hold seasonal grower meetings in each region at orchards involved in commercial evaluations to discuss techniques identified for improving persimmon taste.
- Provide regular updates on the project through a Best Practise Guide, technical bulletins, the PIC website and the industry conference.
Latest update
This project aims to improve persimmon taste by:
- increasing sweetness (or soluble solids content (SSC)) measured as brix;
- reducing astringency - the "dry" taste in the mouth created by small soluble tannins.
The project has demonstrated that fruit with good sweetness related to fruit harvested at optimal colour grade (a minimum 5.5 for Fuyu). The former industry standard was to harvest at a minimum colour grade of 5.0. Delaying harvest by 5-10 days improved external fruit colour and fruit sweetness. This simple change to harvest practice is a cost effective means of increasing sweetness, while making the most of the higher skin colour that NZ fruit can achieve compared to its competitors.
Low fruit astringency is correlated with increased hours above 25°C during January and February. This trend has been observed in harvests 2005, 2006 and 2007. Fruit from orchards in Gisborne has had the lowest levels of astringency and the highest number of hours above 25°C in each season. The weather in the 2008 season was very warm, and this therefore appears to have resulted in minimal astringency, in line with the current model/theory.
Holding fruit with astringency levels which were bordering on unacceptable for 3-5 days at 15°C after harvest successfully reduced astringency. This process could easily be achieved as part of normal post harvest handling.
Update
This project aims to improve persimmon taste by:
- increasing sweetness (or soluble solids content (SSC)) measured as brix;
- reducing astringency, the "dry" taste in the mouth created by small soluble tannins.
During May 2007 fruit samples were harvested from 15 commercial persimmon orchards from Northland to Gisborne.
Fruit with good sweetness related to fruit harvested at optimal colour grade (a minimum 5.5 for Fuyu). Delaying harvest by 5-10 days improved external fruit colour and fruit sweetness. This confirms initial results from 2006 harvest. Fruit from Gisborne also had higher levels of sweetness due to dry conditions during summer/autumn.
Fruit astringency was generally acceptable and low astringency was again correlated with increased hours above 25°C during January and February. This confirms the trend observed in harvests 2005 and 2006. Fruit from Gisborne had the lowest levels of astringency and the highest number of hours above 25°C.
Holding fruit with astringency levels which were bordering on unacceptable for 3-5 days at 15°C after harvest, successfully reduced astringency. This process could easily be achieved as part of normal post harvest handling.
A Best Practise Guide for Improving Persimmon Taste is available for all registered growers, exporters and packhouses at the PIC website: www.nzpersimmons.org.nz
Update
During May fruit samples were harvested from 15 commercial persimmon orchards from Northland to Gisborne.
Fruit with good sweetness related to fruit harvested at optimal colour grade (a minimum 5.5 for Fuyu). Delaying harvest by 5-10 days improved external fruit colour and fruit sweetness. This confirms initial results from 2006 harvest.
Fruit from Gisborne also had higher levels of sweetness due to dry conditions during summer - autumn.
Fruit astringency was generally acceptable and low astringency was again correlated with increased hours above 25°C during January and February. This confirms the trend observed in harvests 2005 and 2006. Fruit from Gisborne had the lowest levels of astringency and the highest number of hours above 25°C.
Holding fruit with astringency levels which were bordering on unacceptable for 3-5 days at 15°C after harvest successfully reduced astringency. This process could easily be achieved as part of normal post harvest handling.
A Best Practise Guide for Improving Persimmon Taste has been mailed to all registered growers, exporters and packhouses is available for PIC members at the PIC website: www.nzpersimmons.org.nz
October 2006
This project aims to Improve Persimmon Taste by:
- Increasing sweetness or soluble solids content (SSC) measured as Brix
- Reducing astringency, the "dry" taste in the mouth created by small soluble tannins.
The approach involves:
1. Industry Wide Profiles of Persimmon Taste
- Regional differences in internal fruit quality, temperature and taste have been measured in 2005 and 2006
- It is believed that temperatures above 25ºC during 12-14 weeks After Full Bloom (Late January/February) are critical for reduction of tannins in fruit and the astringent taste.
- In 2005 there were regional differences in astringency with Gisborne fruit having little or no astringency and Auckland having moderately high levels.
- Canopy air temperatures in orchards in Gisborne were significantly higher than Auckland orchards during this period and we are testing the hypothesis that temperatures over 25°C are the key environmental factor.
- I2006 was a warmer season in all regions and astringency levels were barely detectible.
2. Treatments for Improving Persimmon Taste
- This area examines possible novel management techniques for improving taste.
- Small scale trials evaluating management techniques such as the impact of girdling, leaf thinning, anti-transpirant sprays, irrigation, harvest maturity and post harvest curing on fruit taste were carried out in 2006.
- Important Taste Improvements were achieved by harvesting at correct maturity, and curing post harvest for 3 days at 15°C prior to coolstorage.
3. Development of a New Objective Measure of Astringency
- A promising laboratory test has been developed which measures only the small soluble tannins in fruit. These are the ones which human pallets detect as the "dry" taste perception. There were good correlations with astringency rated by expert tasters in 2005, however in 2006 measurements were difficult due to low levels of astringency in fruit
A Best Practise Guide for Improving Persimmon Taste has been mailed to all registered growers, exporters and packhouses is available for PIC members at the PIC website: www.nzpersimmons.org.nz
June 2006
Key Results to Date:
Results from preliminary studies on persimmon taste undertaken during harvest 2005, which was funded by Persimmon Industry Council were presented at 3 industry Roadshows in November 2005:
- A laboratory test has been developed which measures only the small soluble tannins in fruit (these are the ones which human pallets detect as the "dry" taste perception). So far there have been good correlations with astringency rated by expert tasters.
- There were regional differences in astringency in the 2005 season with Gisborne fruit having little or no astringency and Auckland having moderately high levels. Differences in astringency may be linked to canopy air temperature.
- It is believed that temperatures above 25ºC during 12-14 weeks AFB (Late January/February) are critical for reduction of tannins in fruit.
- Canopy air temperatures in orchards in Gisborne were significantly higher than Auckland orchards during this period and we are testing the hypothesis that temperatures over 25C are the key environmental factor.
This season's work involves:
- Continued development and testing of the astringency test to enable objective measurement of soluble tannins.
- Industry-wide trials measuring orchard air temperatures under different orchard management systems and linking these to fruit taste at harvest. 14 temperature loggers were set out in December in orchards from Kerikeri to northern Hawkes Bay.
- Research into the impact of girdling, leaf thinning, anti-transpirant sprays and irrigation on fruit taste. This area examines possible novel management techniques for improving taste.
- Update of the Taste Best Practice Guide based on this seasons results.
Fruit was harvested from commercial evaluations and trials in May. Assessments have been conducted but detailed analysis is not yet complete. One preliminary result indicates persimmon taste is improved by harvested fruit at higher skin colour:
Harvest maturity and colour grade (CG)
- For each of early, mid and late season harvests, higher colour grades resulted in significantly higher Soluble Solid Content (Brix).
| Harvest | Colour grade 4.5 | Colour grade 5.5 | Colour grade 6.5 |
| Early | 12.4 | 13.4 | 14.9 |
| Mid | 12.4 | 13.8 | 13.6 |
| Late | 12.3 | 13.3 | 14.1 |
The Best Practise Guide for Improving Persimmon Taste has been mailed to all registered growers, exporters and packhouses is available for PIC members at the PIC website: www.nzpersimmons.org.nz
September 2005
Milestone 1, October 2005
Convene a Persimmon Taste Working Group to review existing information and develop a Draft Best Practise Guide for Improving Persimmon Taste, and determine management practices to be evaluated in Year 1.
On 19 August a group comprising persimmon growers from the main growing districts, an exporter, post harvest operators, and three researchers met to exchange and review information on persimmon taste.
Richard Jackman (Hort Research) presented preliminary results of fruit quality comparisons undertaken during the 2005 harvest. A key result was the use of a laboratory method to objectively measure soluble tannins. This method had good correlation to the perception of astringent taste.
Comparisons of fruit quality included the effect on Soluble Solid Content and astringency of:
- Region: Pukekohe vs Gisborne
- Orchard Floor Management: Reflective mulch vs grass sward
- Harvest Date: early, mid or late
- Fruit Position: upper, middle or lower tree position
Further analysis will include relating orchard temperature records to soluble solid and tannin content.
As a result of this meeting a Draft Recommended Best Practise Guide for Improving Persimmon Taste has been prepared for distribution to all growers and will be posted on the Persimmon Industry Council website. Key recommendations are:
Summary Best Practice guide for maximising soluble solids and minimising astringency
- Maintaining an open canopy through pruning strategies (winter and summer)
- Fruit thinning to appropriate level
- Reflective mulch to increase canopy temperatures
- Harvest maturity of a minimum of colour grade 5, preferable colour grade 6
- Postharvest curing at packhouse of 4- 6 days at approximately 15oC
We recommend the use of as many of these practices as possible since each strategy provides additional gains in improvement in soluble solids and/or astringency reduction.
To reinforce this message field days are to be held mid November in Gisborne, Pukekohe and North Auckland.
Progress with other Sustainable Farming Fund projects relating to persimmons will also be covered at these field days:
- Commercial Evaluation of the Persimmon Green & Gold IPM system including work to improve sprayer coverage
- Botrytis and its effects on Persimmons
