125: Optimization of MRI Parameters for the Water Uptake Process in Green Coffee Beans

Introduction

MRI is a non-invasive tool with significant potential to detect internal changes in agricultural products. It provides valuable insights into their structural and compositional properties. The internal moisture changes in green coffee beans are a crucial aspect for developing artificially fermented coffee in the future. MRI, which measures water protons, is well-suited for determining whether moisture has fully penetrated the beans. This study aimed to analyze changes in green coffee beans during the water uptake process using MRI system, focusing on the precise visualization of internal changes.

Methods

MRI images were acquired using various pulse sequences during the moisture uptake process. Spin Echo (SE) and Gradient Echo (GRE) pulse sequences with varying conditions were evaluated for their ability to capture moisture signals in ‘Robusta’ green coffee beans (Vietnam G1 Scr18 Polish). Coffee beans were placed in 50 mL beakers and Falcon tubes and imaged using 80 mm and 35 mm RF coils to determine optimal pulse sequences and parameters. The finalized parameters were used to monitor the process of 11 beans. A graphical user interface (GUI) program was developed to extract regions of interest (ROI), calculate signal-to-noise ratios (SNR), and reconstruct 3D visualizations.

Results

Optimal parameters for GRE were determined by adjusting Time Repetition (14 ms), Flip Angle (60°), and Time Echo (4.2ms) to minimize noise and enhance image clarity. MRI images revealed that water penetration, bean volume, and slice thickness increased rapidly for up to 5 hours after the onset of uptake process before stabilizing. The changes correlated well with previous studies, and regression analysis demonstrated the relationship between moisture content and time. Physical measurements of bean length and width showed increases of 17.3% and 19.8%, respectively, which were compared to MRI-derived measurements of 14.9% and 18.2%.

Significance

This study confirmed that MRI accurately captured moisture uptake processes in green coffee beans, offering a non-invasive alternative to physical measurements. MRI was more suitable than CT or ultrasound for visualizing moisture distribution due to its ability to utilize water nuclei for imaging. These findings suggested potential applications in predicting moisture content and optimizing moisture uptake levels during fermented coffee bean production.

Authors: Seung Hoon Baek, Soojin Jun, Seong Min Kim