Determination of the mechanical properties of the grape berry skin by hydraulic measurements

Theory and instrumentation are presented for determination of the mechanical properties of the grape berry skin. Water under pressure is slowly injected into the grape berry and the pressure and the increase of volume are measured. The stress and the strain in the skin are calculated and presented in the form of a stress-strain diagram. The pressure may be increased until the burst strength of the skin is reached. Examples of measurements are given and discussed. The method may be used to select cultivars resistant to splitting and for the investigation of the properties of the berry which are related to its turgor pressure.