PEACH FIRMNESS DETERMINATION USING TWO DIFFERENT NONDESTRUCTIVE VIBRATIONAL SENSING INSTRUMENTS
Two nondestructive methods employing acoustic resonance analysis were used to test for firmness of fresh 
market peaches (‘Red Haven’ and ‘Crest Haven’). Both devices deliver an impulse to the fruit to induce resonance but 
vibrations are sensed differently. One device uses a contacting piezo-electric disk (piezo instrument) while the other uses 
a non-contacting microphone (acoustic instrument). Frequency spectral parameters were defined to characterize the 
fruit’s impulse response. Objectives were to determine if spectral parameters generated from fruit resonance could be 
used to determine Effe-gi pentrometer firmness. 
Multiple linear regression between derived spectral parameters and Effe-gi firmness for the acoustic instrument 
revealed the strength of the relationships were about the same for two peach cultivars (adjusted r2 = 0.64 to 0.74). The 
piezo instrument produced a poor relationship for the ‘Crest Haven cultivar but a closer relationship for the ‘Red Haven’ 
cultivar (adjusted r 2 = 0.26 to 0.53, respectively). Including mass as a variable with spectral parameters in MLR analysis 
generally increased the r2 values by a small amount for both instruments and cultivars. The ability to accurately predict 
Effe-gi firmness with either instrument was limited due to the lack of a strong relationship between spectral parameters 
and Effe-gi firmness. However, there is potential for sorting out excessively soft, ripe or hard, immature fruit from 
desirable fruit with the acoustic instrument. This could result in a longer or more predictable shelf life. Sorting cost would 
be influenced by the percentage of good fruit falsely rejected (based on Effe-gi firmness) which ranged from 5% to 14% in 
this study.