THE MECHANISM OF THE INCREASE OF FIRMNESS IN STRAWBERRY FRUIT TREATEDWITH 100-PERCENT CO2

In this paper, ire studied tile mechanism of the increase of firmness in strawberry fruit treated with 100% CO2. Internal CO2 concentration in treated fruit increased immediately after the treatment and maintai ned the high level during treatment. But, ii decreased rapidly after r elease of the treatment and reached the same level of untreated ones. This treatment rapidly decreased the ratio of water soluble pectin con tent against total pectin content and increased the ratio of hexa meta phosphate soluble pectin content during and after the treatment, hut d id not affect the ratio of hydrochloric acid soluble pectin to total p ectin in the fruit, Pectin methyl esterase activity was higher in trea ted fruit than the one in untreated fruit during and after the treatme nt. The ratio of Cn content of NaCl-soluble fraction (contained pectin substances) to total Ca content was higher in the treated fruit durin g and after treatment than the one in untreated fruit. These results s uggest thai the increase of firmness of strawberry fruit by 100% CO2 t reatment may be due to the formation of intramolecular bridges in pect in, mediated by Ca2-.