Applied_Spectroscopy_Practica_01_01 - 39

Nakashima et al.
277
Fig. 2f), and the Brix values showed a maximum of about 14 at
45 days (Fig. 2d). Therefore, the harvesting and shipping timing
of mini tomato can be decided based on these daily data. The
authors are applying this daily monitoring of the same samples
to various fruits and vegetables including tomatoes, which will
be reported in future reports. The present portable spectrometer
is expected to be useful for future farmers for providing
high-quality agricultural products to consumers.
Conclusion
A handheld visible and shortwave NIR spectrometer (400-
1050 nm) was developed for monitoring daily changes in
fruits and vegetables. This instrument was used for monitoring
the ripening processes of the same position of a mini
tomato sample daily for about 100 days. The following results
were obtained.
The a* color value (green/red) of the mini tomato
increased rapidly from 35 to 42 days, while the b* color
value (yellow) first decreased and then increased from 35
to 42 days. Brix values showed a maximum at about 45 days.
Reflection spectra in the 400-1050 nm range were converted
to absorption spectra and daily changes of band areas of Chl 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 around 565 nm increased rapidly
from 36 to 44 days associated with the increases in a*
and b* values, indicating that the increase in the reddish
color originated from the increase of lycopene.
The band area of Chl a around 670 nm decreased exponentially
over 100 days. This Chl a decrease could be well fitted
by the first-order reaction giving the rate constant k=
4.1 ×10-7 s-1 at an average temperature of 26 °C.
The quasi-exponential increase of the band area of lycopene
around 565 nm from 36 to 44 days could be fitted by
the first-order reaction giving the rate constant k= 3.2 ×
10-6 s-1 at an average temperature of 23 °C.
The band areas for water plus sugars around 970 nm fluctuated
and did not correlate with the Brix values.
The present study provides the detailed daily changes of
chlorophyll and lycopene and their relations to color values.
These quantitative data will be useful to decide the timing of
the harvest of tomatoes. The portable spectrometer is
expected to provide quantitative bases for the cultivation
and harvest of fruits and vegetables.
Author Contributions
Satoru Nakashima contributed to conceptualization, methodology,
software, validation, formal analysis, investigation, supervision, project
administration, writing-original draft, writing-review, and editing.
Aika Nagasawa contributed to the investigation, data curation,
visualization, writing-original draft, writing-review, and editing.
Kazuto Yokokura contributed to methodology, software, validation,
investigation, resources, writing-review, and editing. Yasuaki Shukuin
contributed to methodology, software, validation, investigation,
resources, and project administration. Naoto Takeda contributed
to methodology, software, validation, investigation, resources, and
project administration. Kiyotaka Yamamoto contributed to methodology,
software, validation, investigation, resources, and project
administration.
Declaration of Conflicting Interests
The authors declared no potential conflicts of interest with respect
to the research, authorship, and/or publication of this article.
Funding
The authors received no financial support for the research, authorship,
and/or publication of this article.
ORCID iD
Satoru Nakashima
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