Structural Changes Caused by CO₂ or Ethanol Deastringency Treatments in Cold-Stored ‘Giombo’ Persimmon

Abstract

Persimmon cv. Giombo is astringent at harvest and must be subjected to astringency removal treatment. To date, the most widespread treatment for this variety involves applying ethanol instead of high CO2 concentrations, which is the usual treatment with other varieties. This study aims to evaluate the effect of high CO2 or ethanol concentrations as deastringency treatments on the quality and flesh structure of ’Giombo´ persimmon during cold storage. The deastringency process was faster in the fruit treated with CO2 than with ethanol. One day after treatment, the CO2-treated fruit showed lower soluble tannin levels than those detected sensorially for this variety, while with the ethanol-treated fruit, these values were obtained after 25 storage days plus the shelf-life period. The tannin insolubilisation process was observed by light microscopy. Loss of flesh firmness during storage was more pronounced when fruit were previously treated with ethanol than with CO2. This is closely related to greater parenchyma degradation during storage caused by ethanol treatment, which was observed by a microstructural study by cryo-scanning electron microscopy. Therefore, as deastringency treatment for ‘Giombo’, applying CO2 instead of ethanol treatment is recommended for better fruit quality, especially when fruit are to be cold-stored.

Keywords

• fruit anatomy
• astringency
• <i>Diospyros kaki</i> Thunb.
• CO₂
• deastringency