Fluorescence time series monitoring of different parts of green pepper (Capsicum annuum L.) under different storage temperatures

Determining the index for monitoring the freshness of green pepper during storage is still a challenge to be solved in research to avoid food loss, linked to the economical loss. The aim of the present study was to investigate the potentiality of fluorescence spectroscopy for the determination of the freshness index. Time series fluorescence characteristics from different parts of green pepper (Capsicum annuum L.) at different temperatures of storage were determined. Three replicate measurements of Excitation and Emission Matrix (EEM) fluorescence were conducted on every single evaluation during 20 days of storage with a 1-day interval starting from day 4 after harvest. Physical evaluation of color change, firmness, and weight loss were observed to have a correlation with the EEM fluorescence intensity. It was observed that fluorescence components could be extracted from green pepper, the intensity of chlorophyll-a EEM significantly dropped after day 16th from 2822 a.u and 2810 a.u to 2038 a.u and 2106 a.u in day 20th stored at 20 degrees C and 4 degrees C respectively as well as the color change behaved the same as the R/G value increased from 0.541 and 0.535 to 0.655 and 0.610 at 20 degrees C and 4 degrees C respectively. Finally, it is suggested that two suspected flavonoids substances with EEM 230-nm/310 nm and 270-nm/310 nm are potential to be a probe for freshness index in green pepper as the ratio of these EEMs increased linearly during storage with R2 0.96 and R2 0.91 for both temperatures 20 degrees C and 4 degrees C respectively.