A novel fluorescence microscopy approach to estimate quality loss of stored fruit fillings as a result of browning

The aim of the present study was to estimate the quality deterioration of apple fillings during storage. Moreover, a potentiality of novel time-saving and non-invasive method based on fluorescence microscopy for prompt ascertainment of non-enzymatic browning initiation in fruit fillings was investigated. Apple filling samples were obtained by mixing different quantities of fruit and stabilizing agents (inulin, pectin and gellan gum), thermally processed and stored for 6-month. The preservation of antioxidant capacity (determined by DPPH method) in apple fillings was indirectly correlated with decrease in total polyphenols content that varied from 34 ± 22 to 56 ± 17% and concomitant accumulation of 5-hydroxymethylfurfural (HMF), ranging from 3.4 ± 0.1 to 8 ± 1 mg/kg in comparison to initial apple puree values. The mean intensity of the fluorescence emission spectra of apple filling samples and initial apple puree was highly correlated (R2 > 0.95) with the HMF content, showing a good potentiality of fluorescence microscopy method to estimate non-enzymatic browning.