###### Abstract  
The main challenge of this scientific work was the implementation on an industrial olive oil extraction plant of an NIR device for the multispectral analysis of pomace to predict the percentage of humidity and oil contained in it. Subsequent to the implementation of the NIR device on the oil extraction line on the solid's outlet from the decanter, NIRS interaction measurements in the 761-1081 nm region were used to probe the pomace. NIRS calibration models for the prediction of water and oil content in the pomace were obtained and successfully tested and validated. The correlations of calibration results for oil and water content were 0.700 and 0.829, while the correlations of validation were 0.773 and 0.676, respectively. Low values of root mean square error were found for both the prediction and validation set. The results highlight the good robustness of an NIR approach based on a PLS calibration model to monitor the industrial olive oil process. The results obtained are a first step toward the large-scale implementation of NIR devices for monitoring pomace in oil mills. The possibility of knowing the oil lost in the pomace, moment by moment, would open a new frontier towards system control and the sustainability of the olive oil extraction process. in-line NIR; industrial instrumentation; olive oil process; PLS regression model; water/oil content +
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of the oil [17; 18; 19]. It has also been demonstrated that the type of crusher, diameter of the holes in the grid, malaxation times, and temperatures can influence extractability [20]. In the end, the adjustment of the decanter can have a strong impact on the amount of oil extracted [4; 5; 21; 22]. It has been demonstrated that when the process is strictly controlled in each phase and when the decanter is adjusted optimally, the extractability can even exceed 90%, peaking at 92.5%, as reported in [23]. To improve the olive oil process by reducing the oil losses in pomace, the addition of technological supports such as talc or enzymes can, respectively, promote the breakdown of oil-in-water emulsions [24; 25; 26] and the breakdown of cellular structures in pulp [27; 28], with a consequent increase in oil extractability and decrease in pomace oil loss. Recently, different innovative technologies based on the use of microwaves, ultrasound, and pulsed electric fields have been introduced in the extraction process, often increasing the extractability of the oil [29; 30; 31]. Knowing the percentage of residual oil in pomace is considered a crucial aspect for optimizing extraction plants, which is influenced by the choice of machines and their adjustment. Currently, the official method to determine the amount of oil lost in pomace requires a time-consuming drying step, followed by solvent extraction [32]. This technique, although accurately returning the humidity and oil content percentage of the sample analyzed, takes more than one day. Considering the long time necessary to obtain the result, this type of analysis is used for machine optimization during the testing phase, at the beginning of each harvest season, or periodically during harvesting to evaluate plant performance. However, to achieve real-time feedback and control, mainly of the decanter, but also of the entire extraction plant, continuous measurement of the water and oil content of the pomace discharged from the decanter is crucial. These measurements make it possible to evaluate whether the decanter or the plant are meeting optimal extraction conditions [33]. In recent years, it has been demonstrated that the use of near-infrared (NIR) spectrometry allows for the measurement of the oil and water content in olives and pomace with satisfactory results in a very short time.