Non-contact bruise detection in apples by thermal imaging
J. Varith , G. M. Hyde, A. L. Baritelle, J. K. Fellman and T. Sattabongkot
Innovative Food Science & Emerging Technologies Volume 4, Issue 2 , June 2003, Pages 211-218
2003
บทคัดย่อ
Thermal imaging is a non-destructiveand non-contact infrared sensing technique. Such imaging creates a bit-map called a thermogram by detecting infrared radiation emitted from an object. Up to 100% of apple bruises were detected using thermal imaging during warming of thefruitsby discriminating surface temperature between bruised and sound tissues. Apples were bruised by dropping them from 0.46 m onto a smooth concrete floor and then were held at 26 °C and 50% RH for 48 h. They were then thermally imaged using a ThermaCam™ PM390 (FLIR Systems, Inc., Portland, OR) during heating and cooling treatments. Thermal images of bruised tissue showed at least 1–2 °C difference from sound tissue within 30–180 s. The temperature differences between bruised and sound tissues were possibly due to the differences in thermal diffusivity. Under steady-state temperature, thermal imaging did not detect bruises, indicating that the temperature differences were not due to emissivity differences. The technique could provide a basis for automatic bruise sorting, and possibly a better understanding of bruised tissue.
Subject-index terms: Industrial relevance: Mechanically damagedfruitsand vegetables account for tremendous economic losses in developed and especially in less developed regions of the world. In addition to attempt to avoid mechanical damage in the first place it is essential to identify such damages since increased microbial contamination and accelerated ripening of plant products can result from such damages. This paper describes the possible application of non-contact infrared sensing technique for bruise detection, which could possibly also be used to identify pre-treatment related changes in thermal diffusivity of food systems.