A Cork Cell Wall Approach To Swelling And Boiling

The bark of cork oak ( Quercus suber L.) is mostly used for cork stopper production, whereas bark is undergoing a series of industrial procedures, boiling usually leading to changes in the characteristics of the tissue. Trees are traditionally grown under natural conditions; however, irrigation is now being used in plantations. These permanent water availability affects cork-oak development, while its effects on industrial procedures is unknown. This study provides a first insight into the behaviour of the cell walls of cork during the process of swelling and boiling when trees have been grown under irrigation, subject to a specific water regime. Cork tissue was analysed using environmental and scanning electron microscopy under three regimes: raw conditions; following immersion in water; and after boiling. Additionally, the radial expansion of samples was determined. The results showed greater cell-wall expansion in cork from the irrigated site than cork from the traditional rainfed plot, when hydrated for 24h. After boiling, the cell walls of the rainfed site were thinner than in the raw stage, in contrast to the irrigated cork. This study suggests that irrigation during cork-oak growth produces a higher capacity for adsorption, increasing cell-wall thickness from the raw stage to the boiling stage.