Macroscopic and microscopic characterization of fluorescence properties of multiple sweet pepper cultivars (Capsicum annuum L.) using excitation-emission matrix and UV induced fluorescence imaging

Zichen Huang; Tetsuyuki Takemoto; Ken Abamba Omwange; Yoshito Saito; Makoto Kuramoto; Naoshi Kondo

doi:10.1016/j.saa.2022.122094

Macroscopic and microscopic characterization of fluorescence properties of multiple sweet pepper cultivars (Capsicum annuum L.) using excitation-emission matrix and UV induced fluorescence imaging

Spectrochim Acta A Mol Biomol Spectrosc. 2023 Mar 5:288:122094. doi: 10.1016/j.saa.2022.122094. Epub 2022 Nov 9.

Authors

Zichen Huang¹, Tetsuyuki Takemoto², Ken Abamba Omwange³, Yoshito Saito⁴, Makoto Kuramoto⁵, Naoshi Kondo³

Affiliations

¹ Laboratory of Biosensing Engineering, Graduate School of Agriculture, Kyoto University, Kitashirakawa, Kyoto 6068267, Japan; JSPS International Research Fellow, Kyoto University, Kyoto, Japan.
² Laboratory of Biosensing Engineering, Graduate School of Agriculture, Kyoto University, Kitashirakawa, Kyoto 6068267, Japan; Agriculture and Forestry Technology Department, Kyoto Prefectural Agriculture, Forestry and Fisheries Technology Center, Kameoka, Kyoto 621-0806, Japan.
³ Laboratory of Biosensing Engineering, Graduate School of Agriculture, Kyoto University, Kitashirakawa, Kyoto 6068267, Japan.
⁴ Institute of Science and Technology, Niigata University, 8050 2-no-cho, Ikarashi, Nishi-ku, Niigata 950-2181, Japan. Electronic address: ysaito@agr.niigata-u.ac.jp.
⁵ Advanced Research Support Center, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan.

PMID: 36442342
DOI: 10.1016/j.saa.2022.122094

Abstract

Sweet peppers are a popular vegetable with various surface colors, such as green, purple, red, or yellow. To characterize the unique fluorescence properties associated with a broad range of sweet peppers of various colors (14 varieties), a fluorescence spectrofluorometer and imaging were used. The results showed that all cultivars in the experiment had blue fluorescence emissions when excited with light in the UV-A region, while chlorophyll fluorescence could be observed in green peppers. The emitted blue fluorescence originated from the epidermis (cuticle layer). The color distribution of these sweet peppers in the a* and b* color space were compared to the image obtained under white LED light. Yellow and red pepper cultivars have thicker, multiple cuticular wax layers and more distinct maturity stages than other sweet pepper varieties observed. With the establishment of this basic fluorescence database, further applications of fluorescence-based techniques and the unification of evaluation methods for pepper quality will be more easily established.

Keywords: Capsicum annuum L.; Excitation-emission matrix (EEM); Fluorescence characteristics; Fluorescence imaging; Sweet pepper.

MeSH terms

Capsicum*
Light
Optical Imaging