Improving bitter pit prediction by the use of X-ray fluorescence (XRF): a new approach by multivariate classification

Autor
Moggia, Claudia
Bravo, Manuel A.
Baettig, Ricardo M.
Valdés, Marcelo
Romero-Bravo, Sebastián
Zuñiga, Mauricio
Cornejo, Jorge
Gosetti, Fabio
Ballabio, Davide
Cabeza, Ricardo A.
Beaudry, Randolph
Lobos, Gustavo A.
Fecha
2022Resumen
Bitter pit (BP) is one of the most relevant post-harvest disorders for apple
industry worldwide, which is often related to calcium (Ca) deficiency at the
calyx end of the fruit. Its occurrence takes place along with an imbalance with
other minerals, such as potassium (K). Although the K/Ca ratio is considered a
valuable indicator of BP, a high variability in the levels of these elements occurs
within the fruit, between fruits of the same plant, and between plants and
orchards. Prediction systems based on the content of elements in fruit have a
high variability because they are determined in samples composed of various
fruits. With X-ray fluorescence (XRF) spectrometry, it is possible to characterize
non-destructively the signal intensity for several mineral elements at a given
position in individual fruit and thus, the complete signal of the mineral
composition can be used to perform a predictive model to determine the
incidence of bitter pit. Therefore, it was hypothesized that using a multivariate
modeling approach, other elements beyond the K and Ca could be found that
could improve the current clutter prediction capability. Two studies were
carried out: on the first one an experiment was conducted to determine the
K/Ca and the whole spectrum using XRF of a balanced sample of affected and
non-affected ‘Granny Smith’ apples. On the second study apples of three
cultivars (‘Granny Smith’, ‘Brookfield’ and ‘Fuji’), were harvested from two
commercial orchards to evaluate the use of XRF to predict BP. With data
from the first study a multivariate classification system was trained (balanced
database of healthy and BP fruit, consisting in 176 from each group) and then
the model was applied on the second study to fruit from two orchards with a
history of BP. Results show that when dimensionality reduction was performed
on the XRF spectra (1.5 - 8 KeV) of ‘Granny Smith’ apples, comparing fruit with
and without BP, along with K and Ca, four other elements (i.e., Cl, Si, P, and S)
were found to be deterministic. However, the PCA revealed that the
classification between samples (BP vs. non-BP fruit) was not possible by
univariate analysis (individual elements or the K/Ca ratio).Therefore, a
multivariate classification approach was applied, and the classification
measures (sensitivity, specificity, and balanced precision) of the PLS-DA
models for all cultivars evaluated (‘Granny Smith’, ‘Fuji’ and ‘Brookfield’) on
the full training samples and with both validation procedures (Venetian and
Monte Carlo), ranged from 0.76 to 0.92. The results of this work indicate that
using this technology at the individual fruit level is essential to understand the
factors that determine this disorder and can improve BP prediction of
intact fruit.
Fuente
Frontiers in Plant Science, 13, 1033308Link de Acceso
Click aquí para ver el documentoIdentificador DOI
doi.org/10.3389/fpls.2022.1033308Colecciones
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