Near infrared imaging to detect Aspergillus flavus infection in three varieties of dates

Abstract

The present manual sorting technique is not effective to detect fungal infection in dates; especially at the early stage. The potential of near infrared (NIR) area scan imaging (900–1700 nm together as one image) to detect fungal contamination in three popular varieties of dates (Fard, Khalas and Naghal) was investigated. Date samples were treated as three groups: untreated control (UC), sterile control (SC) (surface sterilized, rinsed and dried) and infested samples (IS) (surface sterilized, rinsed, dried and fungal inoculated). The IS was then incubated for 10 days and imaged every 48hr to obtain 5 infection stages namely IS Day2, IS Day4, IS Day6, IS Day8 and IS Day10. In total, 3150 NIR images (UC + SC + five fungal infection stages × 150 images × three date varieties) were acquired and analyzed. The overall highest classification accuracy was 97, 96 and 100% for two-class, six-class and pair-wise models, respectively while comparing IS with UC. Similarly, it was 94, 89 and 94% for two-class, six-class and pair-wise models, respectively while comparing IS with SC. However, when the developed algorithm was tested on pooled dates images (all three varieties combined), the two class model yielded a higher classification accuracy of 83 and 86% for UC and IS, respectively; and 71 and 85% for SC and IS, respectively. Thus, NIR area-scan imaging has the potential to be used as a fast and cheaper technique to detect fungal infection in food industries.