Evaluation of apple juice quality using spectral fluorescence signatures

In current work the method of in vivo evaluation of apple juice degree of naturalness based on Spectral Fluorescence Signature (SFS) is proposed. SFS spectra of intact apple juice were measured as excitation-emission matrix by specially designed compact spectrofluorimeter with front-face optical layout - Instant Screener Compact (LDI AS, Estonia). The data were analysed using PCA method with a view to evaluate the information of polyphenol's content in different commercial juices. Results of PCA analysis have shown a clear separation of juice reconstituted from concentrate, unclarified pasteurised juice and personally squeezed apple juice at the two dimensional PCs space. For implementation of apple juice analysis into spectrofluorimeter software the k-Nearest Neighbor (kNN) Search technique was used. The implemented model was tested using 19 different samples of apple juice. Results of test demonstrate that SFS-PCA-kNN method can provide quick nondestructive analysis of naturalness degree of commercial apple juice.