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Case Report
Daily Monitoring of Ripening Processes
of a Tomato Using an Original Handheld
Visible-Near-Infrared Spectrometer
Satoru Nakashima1
, Aika Nagasawa2, Kazuto Yokokura3,
Yasuaki Shukuin3, Naoto Takeda3, and Kiyotaka Yamamoto4
Abstract
A handheld visible- and shortwave near-infrared spectrometer has been developed for monitoring daily changes in fruits and
vegetables. The ripening processes of a mini tomato sample have been monitored daily for about 100 days by this instrument
and color values L*a*b* and Brix were measured. Obtained reflection spectra in the 400-1050 nm range were converted to
absorption spectra and daily changes of band areas of chlorophyll a (Ch1 a; 640-710 nm), carotenoids (460-520 nm), lycopene
(545-600 nm), and water + sugar (920-1050 nm) were determined. The band area of lycopene increased rapidly from
36 to 44 days associated with the increase in a* value, indicating that the increase in the reddish color originated from the
increase of lycopene. On the other hand, the band area of Chl a decreased exponentially over 100 days. This Chl a decrease
could be well fitted by the first-order reaction giving the rate constant k= 4.07 ×10-7 s-1. These quantitative daily changes of
pigments in fruits and vegetables are expected to provide comprehensive bases for their cultivation and harvest.
Keywords
Visible reflectance spectroscopy, handheld spectrometer, visible-near-infrared, Vis-NIR, tomato, ripening, color change,
chlorophylls, lycopene, rate constants, kinetics
Date received: 11 April 2023; accepted: 25 May 2023
Introduction
The ripening processes of vegetables and fruits such as tomatoes
have been extensively studied by dividing them into several
stages and analyzing representative chemical components.1-4
Tomatoes are one of the most important vegetables/fruits,
since they contain sugars and many health-promoting compounds
including carotenoids, phenols, and vitamins.2-4
Biochemistry and metabolic pathways of tomato fruit development
have been studied through conventional chemical analyses
by taking samples with their processing to powders or liquids.2-4
Visible spectroscopy with color measurements has often
been conducted for fruits/vegetable ripening processes,
since dramatic color changes occur during their ripening.5-8
For tomatoes, several visible wavelengths including 570 nm
for lycopene8 and 675 nm for chlorophylls,6 and color a*
(green/red) and b* (blue/yellow) values (Commission
Internationale de l'Eclairage [CIE] 1976)5,9 have been used
to correlate these with lycopene contents and ripening stages.
Near-infrared (NIR) spectroscopy has also been performed
for fruits/vegetable ripening processes, especially for
evaluating water and soluble solids such as sugars.10,11 For
tomatoes, the Vis-NIR region was analyzed by chemometrics
to evaluate the contents of chemical components with their
sensory qualities,12 and soluble solids and lycopene.11
However, for farmers working at cultivation sites, the
decision of harvesting and shipping of fruits and vegetables
needs detailed data on quantitative daily changes of main
chemical components in response to different ripening
stages. Conventional analytical chemical methods are timeconsuming
and cannot be applied to the same samples.
Therefore, nondestructive methods such as visible and NIR
spectroscopy are required to provide quantitative daily
changes of some representative chemical components during
the ripening of fruits and vegetables.
1Research Institute for Natural Environment, Science and Technology
(RINEST), Osaka, Japan
2Department of Life Science and Biotechnology, Faculty of Chemistry,
Materials and Bioengineering, Kansai University, Osaka, Japan
3Fuso Precision Co. Ltd, Kyoto, Japan
4Alpha-Prompt Co. Ltd, Hyogo, Japan
Corresponding Author:
Satoru Nakashima, Research Institute for Natural Environment, Science and
Technology (RINEST), Osaka, Japan.
Email: SatoruNakashima.ed@gmail.com
Creative Commons Non Commercial CC BY-NC: This article is distributed under the terms of the Creative Commons AttributionNonCommercial
4.0 License (https://creativecommons.org/licenses/by-nc/4.0/) which permits non-commercial use, reproduction and distribution
of the work without further permission provided the original work is attributed as specified on the SAGE and Open Access page (https://us.sagepub.com/enus/nam/open-access-at-sage).
Applied
Spectroscopy Practica
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© The Author(s) 2023
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DOI: 10.1177/27551857231181923
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