According to Adamson the capillary pressure of the plant tissues affects penetration of solvents significantly. The capillary pressure is influenced by factors such as the surface tension between the solvent and the gas phase, the solvent contact wetting angle and the capillary radius. Because of the presence of waxes and resins on the surfaces of plant tissues, the surfaces become resistant to the solvent giving a high wetting angle. Hence the amount of extractable pectin is reduced considerably. The ethanol, as a surfactant solvent, significantly reduces the wetting angle of the plant tissues by modifying the drainage properties of the plant tissues. Consequently, the capillary pressure of the plant tissues is increased, and this condition causes an improvement in the penetration rate of the solvent.