Influence of precipitation on Vis/NIR spectra of ‘Gala’ apples

Vis/NIR (visible/near infrared) scanning is a promising tool to obtain non-destructive information on apple fruit quality parameters.
Changes in plant pigments like chlorophyll, anthocyanins and carotenoids can be followed in the Vis region during fruit growth.
Soluble solids and dry matter content are obtained from partial least square regression models developed from the NIR spectra.
However, the light absorption in the NIR wavelength range is particularly influenced by water and carbohydrates.
This study investigates, if precipitation before field scanning can lead to changes in the NIR absorption.
In Southwest Germany Vis/NIR orchard and lab scanning of ‘Gala’ apples were undertaken for seven weeks around harvest in 2019. Apples were either covered with hail net (standard orchard practice) or plastic sheet rain covers (RC). RC were installed to protect fruit from direct precipitation in order to reduce plant protection applications.
The study showed no influence of precipitation on the Vis spectra.
The NIR spectra revealed a 4-5% lower water concentration for the RC treatment in the lab, but no distinct effects for field scanning at 975 nm after rain events.
Results from spectral indices and standard maturity testing during fruit ripening are shown.

IV International Symposium on Horticulture in Europe – SHE2021

K. Biegert, S.A. Lohner, R.J. McCormick, A. Kienle, P. Braun

absorbance, scattering, fruit water content, field spectrometer, integrating sphere

https://doi.org/10.17660/ActaHortic.2021.1327.88