Nondestructive Early Detection of Bruising in Pear Fruit Using Optical Coherence Tomography

Abstract

Pear fruit is susceptible to mechanical injury during harvesting, packaging, and transportation. Optical coherence tomography (OCT) can provide information concerning chemical and microstructural changes of fruit tissues. Therefore, using OCT to evaluate fruit quality is of great significance. In this study, OCT was used for early detection of subtle bruise symptoms underneath the pear peel. First, the signal intensity versus depth in relation to the OCT images of fruit tissue was determined, which was derived from the values of the OCT signal slope (OCTSS) and 1/e light penetration depth (D1/e). Furthermore, shaping (α) and scaling (β) indices were estimated by fitting a gamma distribution function to the signal intensity profile. After mechanical injury, OCTSS, α, and β decreased and the D1/e value increased. Distribution analysis of the relationship between α versus β served as an effective method to identify tissue bruising at an early stage. In conclusion, the results suggest that OCTSS, D1/e, and the α versus β distribution are closely correlated with bruise injury in pear fruit tissues. Thus, OCT is a promising technology for early and nondestructive bruise detection.