Mechanical properties of plantains by vibrational method

Abstract

Hard, green plantain fruits (Musa AAB Group) were obtained, sorted, weighed, labelled, and stored for 2 weeks in a chamber maintained at 20° C and relative humidity of 90±4%. On daily basis, for a period of 2 weeks, the fruits were removed from the storage chamber and each was weighed and vertically vibrated on a low-level mechanical vibration exciter through a range of frequencies 10 to 2000 Hz. The frequency response was modeled by a 2-degrees of freedom model. The model successfully separated the vibrational effect due to the peel from that due to the pulp, and the transmissibility of vibration through the fruit decreased with storage time. The first natural frequency (mode) of green plantains occurred at an average value of about 90 Hz with the amplitude ratio of above unity, while the second mode occurred between 200 and 300 Hz. The model prediction of the amplitude ratio agreed well with the observed data within the range of frequencies between 10 and 200 Hz, but deviated at higher frequencies.