Intensity-modulated optical fiber strain sensor for continuous measurements of below-the-surface food deformation during drying

TL;DR

This paper introduces a novel optical fiber strain sensor capable of continuous, in-situ measurement of below-the-surface deformation in food during drying, providing insights into internal structural changes.

Contribution

The work presents a new mm-scale fiber sensor with a soft buffer for large deformation range, enabling detailed internal deformation monitoring during food drying.

Findings

Sensor accurately measured ~20% strain in banana slices.

Revealed shell-hardening characteristics during drying.

Demonstrated potential for improved food drying process control.

Abstract

We present a mm-scale optical fiber strain sensor to continuously measure the food deformation below the surface during the drying process. The sensor has a soft buffer sleeve, which enables a large measurable deformation range and minimizes the influence on the native food deformation. The sensor performance was investigated both theoretically and experimentally. To demonstrate the application in foods, we embedded the sensor inside fresh banana slices during a 4-hour-long air-drying process, where its wet basis moisture contents dropped from around 80% to 40%. The fiber sensor measurements covered the full normal strain of ~20% of the banana slices and revealed the shell-hardening characteristics in both the spatial and time dependences, by the comparison with the surface strains measured by the computer vision. Our work provides an unprecedented strain sensor that holds a high potential to contribute to improving both fundamental understandings and process monitoring of food drying processes.