Japanese plums: Post-harvest treatments for a better quality

In the last years, the consumption of Japanese plums has been increasing in Turkey.

The fruit softening is a major problem for the marketing and for the eating quality. The marketing quality of plums can be maintained up to 2 months in cold storage at 0°C; however, the plums are very susceptible to low temperatures that are responsible of chilling injuries occurring in the fruit. The flesh browning is the main chilling injury symptom in plums and its severity depends on plum variety and storage temperature.

During storage, the flesh softening is due to ethylene presence around or in the fruit. Many studies on plum postharvest storage demonstrated that 1-MCP (1-MethylCycloPropene) can reduce the respiration rate and the ethylene production improving the retention of flesh firmness. The efficacy of 1-MCP depends on cultivar, growing conditions, maturity stage, and ethylene presence.
In addition, quality decay, respiration rate, ethylene production and enzymatic activity can be retarded also by using MAP (Modified Atmosphere Packaging), whose efficacy depends on physical properties of the film and the respiration rate of the product.

The aim of the research on Japanese plums conducted by a Turkish team (Erkan and Eski, 2012) was to evaluate the efficacy of 1-MCP alone or combined with MAP on postharvest quality of two plum cultivars, "Autumn Giant" and "Black Beauty", during 2-month storage at 0°C and 7-day shelf-life at 20°C.

For the work, the plums were treated with 500 ppb of 1-MCP on the day of harvest before the storage at 0°C; for packaging was used a polyethylene film with a thickness of 30 µm and with O2 and CO2 permeability of 1,614.32 e 546. 24 mL (m2 day atm), respectively.

The treatments tested were:
  1. Plums stored at 0°C (Control);
  2. Plums packaged in MAP and stored at 0°C (MAP);
  3. Plums treated with 1-MCP and stored at 0°C (1-MCP);
  4. Plums treated with 1-MCP, packaged in MAP, and stored at 0°C (1-MCP + MAP).
Fresh weight loss, flesh firmness, titratable acidity, soluble solids, and external quality were evaluated every 10 days. For the external appearance was used a value scale from 0 (= very poor) to 4 (=excellent).

Results showed that:
  1. The treatment with 1-MCP alone and combined with MAP were more effective in retarding the timing of respiration and ethylene peaks compared to the control and MAP treatment, and in reducing the incidence of the flesh browning and softening;
  2. The treatment with MAP alone and combined with 1-MCP were more effective in reducing the fresh weight loss compared to control and 1-MCP treatment;
  3. The treatment with 1-MCP alone or combined with MAP allowed to preserve postharvest quality up to 2 months at 0°C without compromising the overall quality of the plums and controlling the flesh softening;
  4. The treatment 1-MCP combined with MAP resulted the most effective in maintaining the plum quality during shelf-life of 7 days at 20°C, after storage at 0°C.
A table with some results of the present work is following reported

Click here to enlarge the table.

Original research. Erkan M., Eski H., "Combined treatment of modified atmosphere packaging and 1-methylcyclopropene improves postharvest quality of Japanese plums", The Turkish Journal of Agriculture and Forestry, 2012, Issue N0. 36, pagg. 563-575. Further info: http://journals.tubitak.gov.tr/agriculture/issues/tar-12-36-5/tar-36-5-5-1111-34.pdf

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