Assessment Of Antioxidant Level Of Tomato Based On FT-IR Technology

The overall objective of this thesis was to assess the antioxidant level of tomato simultaneously and systematically through the application of infrared spectroscopy (IR) technology. Here the antioxidant level stood for both antioxidants and the antioxidant activity parameters. The former was including flavonoids, lycopene, phenolics and ascorbic acid while the later was represented by FRAP value, DPPH radical scavenging activity and CLA antioxidant activity coefficient.Different dozes of short wave ultraviolet irradiation (UV-C) along with different storage time were applied to create gradients of antioxidant level, while freeze-dry processing was carried out to de-moisture the samples. Spectra wave numbers from 400 cm-1 to 7000 cm-1 were employed in different models. Savitizky-Golay smoothing (SG), baseline offset correction (BOC), standard normalized variate (SNV), area normalization (AN), noise addition (NA) and 1st derivative (1st Der) were adopted as pre-treatment methods while peak find and chemical reference (PFCR) method and principle components analysis (PCA) were applied to reduce the inputs; PCA was also used for clustering analysis for UV-C dozes and storage time. In this thesis, partial least squares regression (PLS) and least squares-support vector machine (LS-SVM) were adopted to build the models while they were evaluated by correlation coefficient (R) and root mean squares error (RMSE) for their performance in calibration, validation and prediction.The results were as follows:PCA has showed obvious clustering effect for UV-C dozes so did for storage time. For the prediction of antioxidants:models for flavonoids, lycopene and total phenolics were preferable, their Rp and RMSEP were 0.8649,0.8928, 0.7592 and 1.3585,1.2466,1.8903 separately. The prediction for ascorbic acid (VC) was not satisfactory. For the prediction of overall antioxidant activity tested by ferric reducing/antioxidant power assay (FRAP),2,2-diphenyl-l-picrylhydrazyl assay (DPPH) were pleasing. For FRAP value:R=0.8963, RMSEP=0.6466; for DPPH scavenging activity:R=0.9111, RMSEP=1.8172; while for antioxidant activity coefficient tested byβ-carotene/linoleic acid system assay (CLA), the results was not valuable. Through the results of this thesis, we validated that IR technology could be adopted for the evaluation of tomato's antioxidant level with the character of simultaneous, convenient, accurate and rapid.