Application of Spectrofluorimetry to Evaluate Quality Changes in Stored Blue Honeysuckle Berry (Lonicera kamtschatica) Preserves

The aim of this study was to use a rapid and non-invasive spectrofluorimetric method to evaluate the qualitative changes occurring in stored Kamchatka berry preserves. Honeysuckle berries were preserved by freezing (-24 °C) and pasteurisation with and without sugar addition. Pasteurised samples were stored at 6 ± 1 °C and 22 ± 1 °C for 9 months. During storage, spectrofluorimetric spectra in the bioactive compounds' fluorescence range were registered. The obtained synchronous spectra were used in a statistical analysis involving principal component analysis (PCA) and linear discriminant analysis (LDA). The analysis of both types of registered spectra indicated that sugar addition could stabilise some phenolic compounds, like gallic acid, p-coumaric acid, and phloridzin. Moreover, some differences in the degradation rate of each analysed compound were observed depending on the preservation method used. Besides the phenolic compounds, other fluorescent compounds like B-vitamins and chlorophyll forms were also observed. Pasteurisation caused the distinct degradation of protochlorophyll forms, whereas practically no changes in the amounts of vitamins B₃ and B₉ were observed. Based on the results of statistical analyses of PCA and LDA, the effect on the products' composition was moderate for the storage time and relatively low in the case of the storage temperature. The obtained results indicated that spectrofluorimetry would be a useful method for the detailed characterisation of fruit products.