Screening of antioxidant properties of the apple juice using the front-face synchronous fluorescence and chemometrics

Fluorescence spectroscopy is gaining increasing attention in food analysis due to its higher sensitivity and selectivity as compared to other spectroscopic techniques. Synchronous scanning fluorescence technique is particularly useful in studies of multi-fluorophoric food samples, providing a further improvement of selectivity by reduction in the spectral overlapping and suppressing light-scattering interferences. Presently, we study the feasibility of the prediction of the total phenolics, flavonoids, and antioxidant capacity using front-face synchronous fluorescence spectra of apple juices. Commercial apple juices from different product ranges were studied. Principal component analysis (PCA) applied to the unfolded synchronous fluorescence spectra was used to compare the fluorescence of the entire sample set. The regression analysis was performed using partial least squares (PLS1 and PLS2) methods on the unfolded total synchronous and on the single-offset synchronous fluorescence spectra. The best calibration models for all of the studied parameters were obtained using the PLS1 method for the single-offset synchronous spectra. The models for the prediction of the total flavonoid content had the best performance; the optimal model was obtained for the analysis of the synchronous fluorescence spectra at Delta lambda = 110 nm (R (2) = 0.870, residual predictive deviation (RPD) = 2.7). The optimal calibration models for the prediction of the total phenolic content (Delta lambda = 80 nm, R (2) = 0.766, RPD = 2.0) and the total antioxidant capacity (Delta lambda = 70 nm, R (2) = 0.787, RPD = 2.1) had only an approximate predictive ability. These results demonstrate that synchronous fluorescence could be a useful tool in fast semi-quantitative screening for the antioxidant properties of the apple juices.info:eu-repo/semantics/publishedVersio

Analysis of apple (Malus domestica Borkh.) wax by means of chromatographic techniques and confocal microscopy

The wax of three economically important Belgian apple cultivars, 'Jonagold', 'Jonagored' and 'Elstar', was analysed chemically and structurally before and after 4 and 8 months of optimal ultra low oxygen (ULO) storage and during shelf life. Macroscopically and microscopically the surface properties of 'Elstar' were clearly different from the two other cultivars. These properties changed similarly for all cultivars during storage and shelf life. Chromatographic patterns of the three cultivars were dominated by the carbohydrate fraction with nonacosane (C29) as the major component. Again 'Elstar' differed in composition compared to 'Jonagold' and 'Jonagored'. For the non-destructive structural analysis confocal microscopy was used, and this led to the development of a new technique for the determination of the wax layer thickness. This technique was compared with the chemical technique known for determination of wax layer thickness. With the confocal technique 'Elstar', 'Jonagold' and 'Jonagored' could be significantly (p=0.05) discriminated based on wax-layer thickness, showing values of 4.14 mum, 2.58 mum and 3.41 mum, respectively

Ethylene metabolism in 'Jonagold' apple during CA storage and shelf life : a modeling approach

To be able to preserve climacteric fruit like Malus domestica for a long time suppression and control of the ripening process is crucial. Based on measurements of metabolites and enzymes of ethylene biosynthesis and taking into account the underlying pathway, a kinetic model to predict and simulate ethylene metabolism during storage and shelf life of Jonagold apple was developed. Data was gathered during ripening, storage and shelf life experiments. The obtained model explains 80% of the data