Laser Doppler forced vibrology of soft agricultural products

Abstract

We describe methodology of laser Doppler forced vibrology (LDFV) applied to texture assessment of soft agricultural products. The method is applied to a melon. The lowest frequency resonant peak (mode Mo) is used for corrections of the whole amplitude frequency plot expressed in relation to the forcing deformation level. The main differences between vibrology in vertical and horizontal laser positions are described. Missing and/or degeneration of some modes in the laser horizontal position are explained. Peak analysis of the results obtained reveals the parameters connected with information on internal damping, i.e. internal viscosity. Modulus of elasticity is calculated either from the peak frequency of the M1 mode or by a new method from the Mo peak frequency. The modulus of elasticity of the latter method is nearly one order higher and is more variable than the former probably because the Mo mode is related to physical properties of the surface of the melon in contact with the vibrating table. Fine structure of the skin can lead to possible degenerated forms with more sub-peaks. © Appl. Rheol.