Detection of Monilia Contamination in Plum and Plum Juice with NIR Spectroscopy and Electronic Tongue

Abstract

Plums are one of the commercially important stone fruits that are available on the market in both fresh and processed form and the most sought-after products are prunes, cans, jams, and juices. Maturity, harvest, and post-harvest technologies fundamentally determine the relatively short shelf life of plums which is often threatened by Monilinia spp. Causing brown rot worldwide. The aim of the present research was to use advanced analytical techniques, such as hand-held near infrared spectroscopy (NIRS) and electronic tongue (e-tongue) to detect M. fructigena fungal infection on plums and quantify this fungal contamination in raw plum juices. For this purpose, plums were inoculated with fungal mycelia in different ways (control, intact, and through injury) and stored under different conditions (5 °C, and 24 °C) for eight days. The results obtained with the two instruments were analyzed with chemometric methods, such as linear discriminant analysis (LDA) and partial least squares regression (PLSR). The NIRS-based method proved successful when detectability before the appearance of visible signs of the infection was studied. E-tongue was able to detect and quantify the concentration of juice derived from plum developed with M. fructigena with RMSECV lower than 5% w/w. Overall, the two methods proved to be suitable for discriminating between the treatment groups, however, the classification accuracy was higher for samples stored at 24 °C. The research results show both NIRS and e-tongue are beneficial methods to reduce food waste by providing rapid determination of fruit quality.

Electronic Tongues and Noses: A General Overview

“…This step aims to transform high-dimensional data into lower-dimensional data without losing essential information by identifying relevant features that capture the essential characteristics of data [76]. Some of the strategies used in these systems include Principal Component Analysis (PCA) [77,78], Kernel principal component analysis [7], project pursuit [79], isomap [7], Laplacian Eigenmaps, Locally Linear Embedding (LLE), modified LLE [79], Hesian LLE [80], t-distributed Stochastic Neighbor Embedding (t-SNE) [79], and Linear Discriminant Analysis (LDA) [77,81], among others.…”

Prunus spp. Fruit Quality and Postharvest: Today’s Challenges and Future Perspectives

“…In the last years, several works have been developed in plums, employing NIR technology for the rapid evaluation of quality parameters, among them the detection of Monilia contamination and prediction of quality parameters (SSC, TA, ratio SSC/ TA and firmness) [50,51].…”

Application of Near Infrared Spectroscopy to Monitor the Quality Change of Sour Cherry Stored under Modified Atmosphere Conditions

“…In connection with plums, Guo et al effectively applied NIR spectroscopy combined with qualitative and quantitative chemometric modelling for the fast determination of optimal storage time [ 28 ]. Vitalis et al have repeatedly applied NIR spectral monitoring for controlled refrigerated and ambient storage, besides the detection of brown rot caused by Monilinia on plums [ 29 , 30 ] and sour cherries [ 31 ].…”