Ratiometric Fluorescence and Reflectance Imaging of Rhodamine B and Curcumin Strips for Meat Spoilage Detection
Sandra, Yusuf Hendrawan, Dewi Maya Maharani, Rut Juniar Nainggolan*, Mitha Sa^diyah

Department of Biosystem Engineering, Faculty of Agricultural Technology, Universitas Brawijaya, Malang, 65145, Indonesia
*Email: niar.1906.rut[at]gmail.com

Abstract

Food safety and waste reduction require rapid, portable, and low-cost methods to monitor meat freshness. Paper based fluorescence sensors are attractive because they are simple to fabricate, economical, and responsive to volatile organic compounds released during spoilage. This study evaluates rhodamine B (synthetic) and curcumin (natural) dyed paper strips to track spoilage of beef and pork at ambient temperature. Strips were attached to the inner surface of plastic cup lids above 10 g of meat so that only headspace volatiles reached the strips. Observations were made every two hours from 2 to 12 hours. At each time point, reflectance and fluorescence images of strips and meats were acquired in a mini studio using a camera with white light and an ultraviolet ring at 365 nm. Images were processed in MATLAB 2025 for segmentation and feature extraction from red, green, and blue- hue, saturation, and value- and CIELAB coordinates, and ratiometric colour indices were tracked over time. Results showed consistent patterns: under ultraviolet excitation, beef exhibited a progressive shift toward greener emission, while reflectance images became lighter with reduced apparent redness- pork also brightened, with a shallower ultraviolet trajectory. Curcumin strips displayed stronger and more discriminative changes than rhodamine B, suggesting greater sensitivity to amine volatiles. Strip lightness correlated positively with meat lightness, supporting noncontact headspace sensing. These findings support ratiometric imaging on low cost paper strips for early spoilage tracking in tropical settings and provide a basis for freshness classification and smart packaging.

Keywords: Meat spoilage- rhodamine B- curcumin- fluorescence imaging- reflectance imaging- ratiometric analysis

Topic: Agricultural and bioprocess engineering