Chyngyz Erkinbaev

Optical properties-microstructure-texture relationships of dried apple slices: spatially resolved diffuse reflectance spectroscopy as a novel technique for analysis and process control

The potential of spatially resolved diffuse reflectance spectroscopy in the 500-1000 nm range by means of a fiber-optics probe was investigated for acquiring scattering and absorption properties of air dried apple rings subjected to different pre-treatment conditions: without osmo-dehydration (TQ) and with osmo-dehydration for 1 (OSMO1) and 3 hours (OSMO2). The fresh apple rings were produced from ‘Golden Delicious’ apples at harvest (H) and 5 month storage at 2 conditions: controlled atmosphere (CA) and normal atmosphere (NA). Microstructure properties of the dried apple rings were also obtained from X-ray micro-CT measurements. The TQ samples were found to have significantly higher scattering properties, thicker tissue, smaller pore sizes, were less crispy, and required higher snapping work or rupture energy than the OSMO1 and OSMO2 samples. On the other hand, no significant differences were observed between the scattering properties, microstructure, and textural quality of the OSMO1 and OSMO2 apple rings. From these results, it was concluded that there is a clear process-microstructure-quality relation in osmo-air-dried apples which can be measured non-destructively with spatially resolved diffuse reflectance spectroscopy. AC C EP TE D M AN U SC R IP T ACCEPTED MANUSCRIPT 2 Therefore, this study confirmed the potential of spatially resolved diffuse reflectance spectroscopy for non-destructive quality assessment of air-dried apple slices, which provides perspectives for drying process optimization.

Metamodeling approach for efficient estimation of optical properties of turbid media from spatially resolved diffuse reflectance measurements

A metamodeling approach is introduced and applied to efficiently estimate the bulk optical properties of turbid media from spatially resolved spectroscopy (SRS) measurements. The model has been trained on a set of liquid phantoms covering a wide range of optical properties representative for food and agricultural products and was successfully validated in forward and inverse mode on phantoms not used for training the model. With relative prediction errors of 10% for the estimated bulk optical properties the potential of this metamodeling approach for the estimation of the optical properties of turbid media from spatially resolved spectroscopy measurements has been demonstrated.

Estimation of bulk optical properties of turbid media from hyperspectral scatter imaging measurements: metamodeling approach

In many research areas and application domains, the bulk optical properties of biological materials are of great interest. Unfortunately, these properties cannot be obtained easily for complex turbid media. In this study, a metamodeling approach has been proposed and applied for the fast and accurate estimation of the bulk optical properties from contactless and non-destructive hyperspectral scatter imaging (HSI) measurements. A set of liquid optical phantoms, based on intralipid, methylene blue and water, were prepared and the Vis/NIR bulk optical properties were characterized with a double integrating sphere and unscattered transmittance setup. Accordingly, the phantoms were measured with the HSI technique and metamodels were constructed, relating the Vis/NIR reflectance images to the reference bulk optical properties of the samples. The independent inverse validation showed good prediction performance for the absorption coefficient and the reduced scattering coefficient, with R(2)(p) values of 0.980 and 0.998, and RMSE(P) values of 0.032 cm(-1) and 0.197 cm(-1) respectively. The results clearly support the potential of this approach for fast and accurate estimation of the bulk optical properties of turbid media from contactless HSI measurements.

Spatially resolved spectroscopy for nondestructive quality measurements of Braeburn apples cultivated in sub-fertilization condition

A contact spatially resolved spectroscopy (SRS) setup based on a fiber-optics probe in the Vis/NIR range (400-1000 nm) was developed, calibrated, and validated for its measurements and optical properties estimation by means of a metamodeling method on a set of liquid optical phantoms. Thirty Braeburn apples cultivated in sub-fertilization condition were harvested and measured before and after shelf-life storage (2 weeks at 18 °C) by the setup and were analyzed for quality attributes (firmness and soluble solids contents (SSC)) by destructive reference methods. Estimated optical properties (absorption and reduced scattering coefficients) acquired from SRS measurements at the beginning and the end of the shelf-life indicated changes in chemical composition of the apples. Partial Least Squares Regression (PLSR) was employed to construct calibration models relating the estimated optical properties to the reference quality attributes. The constructed PLS models based on the absorption coefficient spectra gave good prediction performance for the quality attributes of the apples in the validation set with correlation coefficients r of 0.901 and r of 0.844, respectively for SSC and firmness. The obtained results clearly show the potential of the SRS measurements for nondestructive quality evaluation of apples.