Detection and monitoring of internal browning development in 'Fuji' apples using MRI

Magnetic resonance imaging (MRI) experiments were used to detect and monitor the progression of internal browning (IB) in Fuji apples (Malus domestica Borkh.). The apples were stored in two different controlled atmosphere (CA) conditions: 30% CO2 at 0 degreesC and 18% CO2 at 20 degreesC. The apples stored under 18% CO2, were imaged at 1, 3, 5, 7 and 9 days. Apples stored under 3%, CO2 were imaged once a week for the first 7 weeks and then every 2 weeks until the 12th week. Three distinct regions were identified in the MR images of apples with internal browning: normal, light brown and dark brown tissue. Light brown regions, more prominent in apples stored in 3% CO2 at 0 degreesC, had a lower signal intensity than normal tissue because of lower proton density (PD) and smaller transverse relaxation times (T-2). Dark brown regions predominated in apples stored in 18% CO2 at 20 degreesC and displayed higher signal intensity than the normal apple tissue because of larger T-2 values. The speed of image acquisition was improved from 5.5 min to 20 s, by reducing the spatial resolution of the images. Both types of IB were detected by images acquired using coarse spatial resolution and correlated well to the IB detected by the images acquired using fine spatial resolution. (C) 2001 Elsevier Science B.V. All rights reserved.