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Experiment Objectives

The Australian fresh peach industry can export fruit to China using a methyl bromide (MB) quarantine treatment. High quality peaches are the most suitable to export as costumers are willing to pay up to double their market value, therefore fruit quality is the most important parameter. However, producers complain that the high MB dosage can damage fruit.  To our knowledge scarce information is available regarding the effects of MB on fruit quality.

It is known, however, that fruit require less fumigation and contain lower residues when applying this protocol to warm fruit (Hartsell et al., 1986a). The challenge is that Australian peach industries are selecting their fruit for export after it has been in cold storage. This means that the fruit needs to warm up to 18ºC to apply the fumigation protocol. Although it is well known that temperature changes will affect the fruit quality, it is not known what the actual effects are.

Volatile organic compounds are important fruit markers, i.e. fruit composition and flavour volatiles in particular, are a fundamental element of fruit quality for consumer acceptance. MB is respired through the peel and can reach internal parts of the fruit, therefore there could be additional residues or effects not limited to the peel. It is important to evaluate volatiles in both peel and flesh as some people do not eat the peel of the peach.

Accordingly, the aims of this study are to solve several questions:
1) Does methyl bromide fumigation reduces fruit quality?
2) How does warming-up the fruit affect fruit quality after storage and shelf life?
3) Does fumigation have any effect on volatile organic compounds in fruit peel or flesh?

Video: Introduction to the Stonefruit sanitation through fumigation experiment for export opportunities

Stonefruit sanitation through fumigation experiment for export opportunities. Dr Dario Stefanelli - Agriculture Victoria

Fumigation protocol experiment

Researchers will apply 18g/m3 of MBR to fruit for 5.5 hours duration at pulp temperature of 18 degrees Celsius or above, with no more than 34 percent chamber load.
Fruit will be in cold storage for 4 and 8 day durations to simulate fruit being sent by air freight to China.
Researchers will then compare fruit quality and volatile organic compounds in fumigated, non-fumigated and non-warmed fruit.

Figure 1. Experimental design

10 fruit are removed from cold storage at each stage for analysis. The following qualities of each individual fruit are measured: weight, DA-meter (maturity), firmness, sugars and titratable acidity. Volatiles in peel and flesh will be measured in 5 fruit per treatment. Fruit maturity determination, using the DA-meter, will be measured for all fruit inside the chamber at every removal time.

The whole experiment is repeated three times, once for each peach variety - Snow Flame 25 (SF-25); August Bright (AB); & August Flame (AF).

Results

Video: Presentation by Laia Torregrosa-Sauret, Agribio (agriculture Victoria) May 2018

Does methyl bromide affect fruit quality?

Conclusions (20min 39sec):

The effect of the fumigation treatment is very much affected by the variety of the peach.

AF is affected by cold storage.

F (fragrance), TSS (sugars) or TTA (acids) are not affected by the fumigation treatment.

However, metabolic process (ethylene production and respiration) show that fruit was stressed due to the fumigation treatment.

Warming the fruit did not affect fruit quality during the short storage period tested.

Future work: would be interesting to have an omics approach to the effects of fumigation on fruit quality.

This information is brought to you by the Serviced Supply Chain Project (Horticulture Innovation Australia, Queensland Government, Victorian Government, Chinese Academy of Sciences, and the University of Southern Queensland)