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Predicting the Electric Conductivity and Potassium Leaching of Coffee by NIR Spectroscopy Technique Cintia da Silva Araújo 1 & Wallaf Costa Vimercati 1 & Leandro Levate Macedo 1 & Adésio Ferreira 2 & Luiz Carlos Prezotti 3 & Luciano José Quintão Teixeira 4 & Sérgio Henriques Saraiva 4 Received: 29 April 2020 / Accepted: 25 August 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020

Abstract This study aimed to investigate the relationship between the experimental values of electrical conductivity and potassium leaching and near-infrared (NIR) spectra of green coffee beans. Analyses of electrical conductivity and potassium leaching were performed on two hundred fifty samples of green coffee beans. The near-infrared spectra of these samples were collected. The spectra were subjected to pretreatments of multiplicative scatter correction (MSC), standard normal variate (SNV), first derivative, and second derivative. The multivariate statistical method of partial least square (PLS) regression was used in the elaboration of calibration models, which were later applied to forecast external samples. The results obtained demonstrate that good calibration models were developed. The best model obtained for estimating electrical conductivity showed a correlation of 0.97, while for potassium leaching, the maximum correlation between experimental and predicted values was 0.88. These results demonstrate good prospects for predicting the coffee bean cell membranes integrity through spectroscopic techniques. Keywords NIRS . Chemometrics . Partial least squares . Cell membrane permeability

Introduction Coffee is one of the most consumed beverages in the world, with wide popularity in Europe and the USA. Its consumption is stimulated by its pleasant flavor and aroma, as well as by its physiological effects. The beverage has a high content of antioxidants, such as polyphenols, which are influenced by several factors, such as plant species and degree of grain roasting (Vignoli et al. 2011, 2014; Heeger et al. 2017; Araújo et al. 2020). The fruit of the coffee tree consists of a more external region, called pericarp which, during ripening, changes its

color. Below the pericarp is the pulp, which is followed by a thin, viscous layer, known as mucilage. After the mucilage, we find the endocarp (parchment), and finally, there is the silver skin that covers the entire coffee bean, which is also called the endosperm (Esquivel and Jiménez 2012). Among the various elements that make up coffee beans are minerals. These are inorganic compounds that have a high correlation with the type of soil and forms of coffee cultivation (Semen et al. 2017) and perform essential functions for maintaining the physiological processes of the plant (Poltronieri et al. 2011).

* Cintia da Silva Araújo [email protected] Wallaf Costa Vimercati [email protected]

Sérgio Henriques Saraiva [email protected] 1

Postgraduate Program in Food Science and Technology, Center of Agrarian Sciences and Engineering, Federal University o