Nondestructive Monitoring of Ripeness in Mango Cultivars by Acoustic Resonance Spectroscopy

Abstract

Mango cultivars, i.e. Neelam, Alphonso, Banganapalli, Totapuri, and Mallige were subjected to acoustic resonance spectroscopy at unripe, semi-ripe, and ripe stages, as well as in case of ripe bruised fruits. The Neelam variety of mango was screened for internal infestation by means of acoustic spectroscopy. Acoustic data on dominant and first frequencies, damping ratio, and firmness indices were obtained and correlated with mechanical penetration tests as well as a/b values of the tristimulus color profile. The correlations between mechanical tests and acoustic parameters varied from 0.81 to 0.933. However, damping ratio and dominant frequency along with firmness index showed a better correlation with penetration test vis-à-vis first frequencies. The correlations between acoustic parameters and a/b tristimulus color values showed lesser extent and significance of correlations ranging from 0.416 to 0.667. The correlations were found to be positive or negative depending on the specific acoustic parameters. However, in the case of internally infested Neelam, the drop in the first frequency was found to be a significant acoustic indicator. Nondestructive quality monitoring by acoustic spectroscopy was found as such to be consistent as far as the tissue softening and bruising are concerned.