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Quality improvement of pears by predictive and adaptive technology

Contract nr: FAIR-CT96-1803
Project nr: 1803
Project type: SC
Starting date: 01/06/1997
Duration: 48 months
Total cost: 1,600,300 EUR
EC Contribution: 1,045,000 EUR
Scientific Officer: Richard HARDWICK
Research topic: Plant health

Conference is the most important pear species grown in the European Union. One important disorder that often develops is the so-called brown heart (BH), which is a synonym for browning of the flesh, especially the core region, and the subsequent development of cavities. Even pears with minor symptoms are not accepted by consumers. Losses due to BH can add up to 16 million Euro per year in the EU. Because the cultivation area of pears, and conference in particular, is increasing, the estimated losses are conservative. The disorder causes problems throughout Europe, but the intensity differs by country and by year. Thus far, research carried out in one country cannot simply be applied to other countries.

The main objective of the project is the optimisation of Conference pear quality and the reduction of losses by preventing the development of BH. The key element is the development of technology which predicts the susceptibility of pears to the disorder. Two pathways are most promising toward such a technology:
1) The development of a predictive model based on the registered orchard and weather conditions of a broad group of European countries. For this purpose, pears are grown in a range of climate zones, including climate zones with high and low risk of BH.
2) The development of a predictive model based on a rapid assessment of pear physiology after harvest, including gas exchange rates, fermentation rates, ATP production rates and resistance to gas diffusion. In addition to predictions, technology will be developed to prevent the disorder and to improve the storability of harvested pears.

The models enable a rapid decision on adaptations in post-harvest treatments and optimal storage conditions. Research on post-harvest treatments is thought to enable improved storability of pears. For a good selection of pears after storage, a technique is developed which enables the detection of BH without destruction. The prevention of BH in Conference pears will not only reduce losses, but also improve the market value of European pears. An improved quality of pears throughout the year should lead to better and stable prices of the product. Long-stored European pears which meet high-quality standards can also compete better with imported products from the southern hemisphere.

Current situation/results:
Climate data were collected by IRTA, IVTPA, FPO, VCBT and UHOH, resulting in 180 independent data sets after two years. Advice on a post-harvest method to reduce the risk was generated by FPO and confirmed by ATO. The method is based on delaying the application of Controlled Atmosphere conditions to harvested pears for a specific period. In addition to this, a rapid test to predict susceptibility of pears for the disorder was developed by FPO. The test is based on a temperature/CO2 treatment, and was validated in the second year. Methodology on gas exchange and diffusion resistance measurements was tested and optimised, and was used by three partners; ATO, VCBT and UHOH. Protocols were distributed by ATO, and implemented by VCBT and UHOH. Results indicate that there is not an obvious relation between internal CO2 concentrations (as calculated from metabolic rates and diffusion resistance) and increased brown heart at late harvest dates. Also, respiration measurements during the procedure to prevent the disorder (delaying CA) indicate that increased internal CO2 concentrations are not the primary cause of the problem.
The results can be explained by another hypothesis; the disorder will occur after a (temporary) shortage of metabolic energy (ATP). A simultaneous change in temperature and oxygen will lead to such a shortage, while a subsequent change in temperature and oxygen does not lead to (temporary) shortage in ATP. Energy metabolism will be a primary focus in the third year.
Comparable results on ascorbate/vitamin C content in the pears were found by ATO, IRTA and UHOH. Pears more susceptible to the disorder showed lower ascorbate levels, such as pears from a late harvest, pears after longer storage periods and pears stored at higher CO2 concentrations. Ascorbate levels continued to decrease during treatment with high CO2. Comparable results were also found by IRTA and ATO on ethane production, which was increased at high CO2. After extensive research on polyphenol-oxidases, ATO and IRTA concluded that there was no direct relation between PPO content (or activity) and the risk of brown heart. On the other hand, ascorbate levels, and possible other compounds of the oxygen scavenging system as well, are very promising for predicting the disorder and will very likely play a key role in the physiological model.

DLO-ATO - Agrotechnological Research Institute
Bornsesteeg 59
P.O. BOX 17
NL-6700 AA Wageningen
Tel.: +31 317 47 53 02
Fax: +31 317 47 53 47


    I.R.T.A. - Institut De Recerca I Tecnologia Agroalimentaries
    Avda. Alcalde Rovira Roure 177
    E-25198 Lleida
    Tel.: +34 973 70 51 28
    Fax: +34 973 23 83 01

  • Josef STREIF
    Universität Hohenheim
    D-88213 Ravensburg
    Tel.: +49 751 790 33 25
    Fax: +49 751 790 33 22

  • Bart NICALAï
    Vlaams Centrum voor de Bewaring van Tuinbouwproducten VCBT
    W. de Croylaan 42
    B-3001 Heverlee
    Tel.: +32 16 32 23 76
    Fax: +32 16 32 29 55

  • Paola ZERBINI
    Istituto Sperimentale per la Valorizzazione Tecnologica dei Prodotti Agricoli
    Via Venezian 26
    I-20133 Milano
    Tel.: +39 02 70 63 02 56
    Fax: +39 02 36 53 77

  • Anton DE JAGER
    Research Station for Fruit Growing Foundation
    Lingewal 1
    NL-6668 LA Randwijk
    Tel.: +31 488 47 37 34
    Fax: +31 488 47 37 17
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