Nondestructive Evaluation of Pickling Cucumbers Using Visible-Infrared Light Transmission

Abstract

A nondestructive method was developed utilizing a modified Trebor 101 watercore tester to evaluate the internal quality of pickling cucumbers. The method involved measuring the relative amount of visible-infrared light passing through the longitudinal midsection of whole cucumber fruit. Light transmission was quantified on a unitless sigmoid scale from 1 to 10, with light transmission and scale values positively related. Immediately after hand harvest, size 3F (47 to 51 mm in diameter) cucumbers exhibited transmission values between 2 and 3, regardless of cultivar. Following a mechanical-stress treatment, which simulated bruising incurred during harvesting and handling of cucumbers, the internal quality of the fruit declined and was associated with an increase to a value of 6 in light transmission compared to non-stressed fruit. Light transmission increased as the severity of stress applied to the fruit increased, and high light transmission values were evident throughout a 48 h storage period at room temperature. Light transmission values increased as fruit diameter decreased, but values within a particular size class of undamaged, hand-harvested fruit were consistent. Machine-harvested fruit (size 3F), evaluated just before processing, exhibited light transmission values from 2 to 8, but the majority of fruit fell within the transmission range of 2 to 3. When fruit exhibiting different light transmission values were speared (cut longitudinally into sixths), processed, and then visually evaluated by panelists, spears prepared from fruit exhibiting high transmission values were judged to be of lower quality than those prepared from fruit exhibiting low transmission values. Visible-infrared light transmission may be a valuable tool for detecting poor quality cucumbers before processing, and could allow the mechanical selection of high quality fruit on a large scale basis.