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Food quality is an important aspect for the food industry which refers to the production of safe, high nutritional as well as tasty food products. To meet consumer requirements food manufacturers would like to have fast, accurate and non-destructive quality control techniques. Visible (Vis) and Near Infrared (NIR) spectroscopy has been extensively applied as non-destructive quality inspection technique. Traditionally, the quality attributes are predicted based on statistical relations between the acquired spectra and the properties of interest, which are established through the use of multivariate calibration methods. Although these multivariate statistical methods have been extensively used for non-destructive prediction of quality attributes, in complex biological materials such as food these data-based models often prove not to be robust, due to the complex interaction of incident light with food involving both absorption and scattering of the light. Inability of conventional Vis/NIR spectroscopy to separate scattering and absorption information contained in the spectra limits its robustness for prediction of the chemical composition and its usefulness for determination of the microstructure of foods. To overcome the limitations of classical Vis/NIR spectroscopy this PhD research aimed to separate the information on the scattering and absorption properties of food samples by combining multiple diffuse reflectance measurements which are resolved in space. For this purpose, a setup for contactless spatially resolved spectroscopy (SRS) in the 500-960 nm range has been elaborated by combining a focused broadband light beam for the illumination with a hyperspectral line-scan camera for contactless acquisition of SRS profiles. To estimate the absorption coefficient and the reduced scattering coefficient from the SRS profiles acquired at every wavelength, an iterative estimation has been implemented around a data based light propagation model. This metamodel was trained and validated by means of liquid and solid phantoms covering a wide range of optical properties relevant for food products. The reference optical properties of these phantoms were calculated from double integrating spheres (DIS) measurements, the reference technique for bulk optical properties measurement on turbid samples. The forward and inverse validation of the metamodeling approach on the optical phantoms showed good prediction accuracy. This indicates that this combination of hyperspectral scatter imaging with an inverse light propagation model can provide a fast and accurate estimation of the bulk optical properties of turbid samples, such as foods. This technique was then used to estimate the bulk optical properties of different model foods: sugar foams with the same composition, but different microstructures induced by different foaming times, crispy breads produced with different extruder settings, and Braeburn apples stored for a longer period under controlled atmosphere (CA) conditions and exposed to shelf-life. The estimated optical properties were then used to evaluate the food quality attributes by relating them to the composition and microstructure for better understanding the structure-property relations. Finally, the estimated scattering properties of these food samples were correlated with destructive measurements: X-ray micro-CT (sugar foam), universal texture analyzer (crispy breads and Braeburn apples) for non-destructive estimation of the microstructure parameters of the aforementioned samples. Clear relations were observed between the estimated bulk optical properties (scattering property) and microstructure of the sugar foams and crispy bread samples. These results support the potential of hyperspectral scatter imaging to provide an indirect estimation of the food composition and texture parameters in a rapid and non-contact way. This makes it a very interesting technique for online quality inspection and process monitoring in the food industry. While good results were reported for the model foods, the results for apple fruit with its more complex microstructure were inconclusive with respect to the potential of hyperspectral scatter imaging for non-destructive assessment of the consumption quality. The estimated absorption coefficient spectra of the Braeburn apple fruits clearly showed the changes in chemical composition of the apples during CA storage over a longer period (up to 6 months) and shelf-life exposure (14 days). Mainly, these changes were observed as a decrease in the absorption coefficient values around 670 nm which was due to the degradation of chlorophyll during storage. Also, a clear decrease in the scattering properties of the apples was observed after 14 days of shelf-life exposure. However, no clear differences were observed in the optical properties estimated for the apples which had been stored under optimal and brown inducing CA storage conditions. This was explained by the fact that hyperspectral scatter imaging only probes the outer layers of the fruit, while the browning typically starts at the center of the fruit. Quantitative prediction of the internal apple quality in terms of soluble solids content (SSC) and fruit firmness (FF) based on respectively the bulk absorption coefficient and the reduced scattering coefficient did not result in higher prediction accuracy than prediction based on single point Vis/NIR reflectance spectra. The overall results clearly support a strong potential of the combination of the line-scanning hyperspectral scatter imaging technique with the computationally fast and accurate inverse metamodeling approach for fast, contactless and non-destructive optical properties estimation of food products to separate the information on the microstructure from that on the chemical composition.

664.017 --- Academic collection --- Properties of preserved foods and foodstuffs. Food quality --- Theses --- 664.017 Properties of preserved foods and foodstuffs. Food quality

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577.114 <063> --- 664.017 --- Food --- -Foods --- Dinners and dining --- Home economics --- Table --- Cooking --- Diet --- Dietaries --- Gastronomy --- Nutrition --- Carbohydrates. Monosaccharides. Polysaccharides--Congressen --- Properties of preserved foods and foodstuffs. Food quality --- Polysaccharide content --- -Congresses --- Congresses. --- -Carbohydrates. Monosaccharides. Polysaccharides--Congressen --- 664.017 Properties of preserved foods and foodstuffs. Food quality --- 577.114 <063> Carbohydrates. Monosaccharides. Polysaccharides--Congressen --- -664.017 Properties of preserved foods and foodstuffs. Food quality --- Foods --- Polysaccharide content&delete& --- Congresses --- Primitive societies

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Food --- Testing --- Congresses --- 641.1 --- 664.017 --- -Foods --- Dinners and dining --- Home economics --- Table --- Cooking --- Diet --- Dietaries --- Gastronomy --- Nutrition --- Foodstuffs from the point of view of properties. Nutritional value --- Properties of preserved foods and foodstuffs. Food quality --- -Congresses --- -Foodstuffs from the point of view of properties. Nutritional value --- 664.017 Properties of preserved foods and foodstuffs. Food quality --- 641.1 Foodstuffs from the point of view of properties. Nutritional value --- -664.017 Properties of preserved foods and foodstuffs. Food quality --- Foods --- Testing&delete& --- Primitive societies --- Food - Testing - Congresses

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Alimentation --- Aliments --- Besoins --- Composition --- 641.1 --- 613.2 --- 664.017 --- Foodstuffs from the point of view of properties. Nutritional value --- Voedingsleer. Dieet --- Properties of preserved foods and foodstuffs. Food quality --- 664.017 Properties of preserved foods and foodstuffs. Food quality --- 641.1 Foodstuffs from the point of view of properties. Nutritional value

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641.1 --- 664.017 --- Academic collection --- Foodstuffs from the point of view of properties. Nutritional value --- Properties of preserved foods and foodstuffs. Food quality --- 664.017 Properties of preserved foods and foodstuffs. Food quality --- 641.1 Foodstuffs from the point of view of properties. Nutritional value