Prediction of quality of intact olives by near infrared spectroscopy

Abstract

AbstractIn this work we investigated the intact olive fruit quality prediction parameters measured directly by visible and near infrared spectroscopy (Vis/NIRS); the usefulness of a portable spectrometer is also assessed. The analysed parameters of the olive fruits were moisture, dry matter, oil content, oil free acidity and fruit maturity index. It was also studied whether NIR prediction of dry matter on olives may be more useful than NIR moisture measurement. Likewise, the results from the NIR prediction of olive oil contents related to dry matter as well as to fresh weight, were compared. Models for oil content were developed using Soxhlet extraction from dried olive paste as the reference analysis. Results indicate a good prediction potential of the models for the olive quality parameters analysed, with RPD ratios from 2.51 to 3.18. The successful NIR predictions of these quality parameters are reported for the first time.Practical applications: The technique presented here can expedite the milling procedure by allowing early detection of the olive quality and a quick calculation of the economic returns to the producers becomes possible. Furthermore, since oil quality depends largely on the optimal harvesting date when the olives should be taken to the mill, techniques that enable the monitoring of the oil content in olive fruit at different stages of maturity, even while still on the tree, become a useful and practical tool. This technique could allow monitoring the quality attributes of large amounts of the olive fruit entering the mill without the need of laboratory analysis that can only be conducted on a small number of olive fruit samples.