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The bulk optical properties (BOP) of two bovine muscles were studied in the 500 nm to 1850 nm wavelength range. Over a two-week period of wet aging, the BOP of the biceps femoris (BF) and longissimus lumborum (LL) were determined and related to moisture content, tenderness and cooking loss. The absorption by myoglobin and reduced scattering coefficient were higher in the BF compared to the LL. The scattering anisotropy factor was relatively high (> 0.95 for LL), representing dominant forward scattering. Two-toning effects in the BF could be attributed to significant scattering differences, as no differences in absorption properties were observed. During wet aging, the anisotropy factor decreased, while tenderness increased. It was hypothesized that this might be related to proteolysis of cytoskeletal proteins. The results show the potential use of BOP to monitor tenderization and the cause of color differences in beef muscles. Moreover, this information could be used to develop and optimize optical sensors for non-destructive meat quality monitoring. [ABSTRACT FROM AUTHOR]

To facilitate the design of new optical measurement systems for biological systems, the knowledge of light propagation properties is essential. Therefore, the bulk optical properties of skin and cortex of three apple cultivars were studied during maturation, in the 500 nm–1850 nm range. A clear absorption signature was observed with absorption peaks which can be related to present anthocyanins, chlorophyll, carotenoids and water. During maturation, the skin absorption at 550 nm increased in the bicolored cultivars ‘ Braeburn ’ and ‘ Kanzi ’, while the absorption at 680 nm decreased in the cortex. Both the bulk scattering coefficient and the anisotropy factor were larger for the skin compared to the cortex tissue. Also during maturation, the skin scattering increased in the two bicolored cultivars, while a general decrease was seen in the apple cortex. Physiological changes during maturation, like cell growth, the formation/degradation of pigments and the formation of a cuticle layer on the skin, may explain the observed evolutions. As a result, using the bulk optical properties, these physiological changes can be monitored and linked to the maturity stage in the orchard, supporting the selective harvest of apples. [ABSTRACT FROM AUTHOR]

A global optimizer has been developed, capable of computing the optimal configuration in a probe for spatially resolved reflectance spectroscopy (SRS). The main objective is to minimize the number of detection fibers, while maintaining an accurate estimation of both absorption and scattering profiles. Multiple fibers are necessary to robustify the estimation of optical properties against noise, which is typically present in the measured signals and influences the accuracy of the inverse estimation. The optimizer is based on a robust metamodel-based inverse estimation of the absorption coefficient and a reduced scattering coefficient from the acquired SRS signals. A genetic algorithm is used to evaluate the effect of the fiber placement on the performance of the inverse estimator to find the bulk optical properties of raw milk. The algorithm to find the optimal fiber placement was repeatedly executed for cases with a different number of detection fibers, ranging from 3 to 30. Afterwards, the optimal designs for each considered number of fibers were compared based on their performance in separating the absorption and scattering properties, and the significance of the differences was tested. A sensor configuration with 13 detection fibers was found to be the combination with the lowest number of fibers which provided an estimation performance which was not significantly worse than the one obtained with the best design (30 detection fibers). This design resulted in the root mean squared error of prediction (RMSEP) of 1.411 cm −1 ( R 2 = 0.965) for the estimation of the bulk absorption coefficient values, and 0.382 cm −1 ( R 2 = 0.996) for the reduced scattering coefficient values. [ABSTRACT FROM AUTHOR]

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 h (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. 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. [ABSTRACT FROM AUTHOR]

Highlights: [•] The optical properties of Braeburn apples before and after shelf-life were measured with a setup for spatially resolved diffuse reflectance spectroscopy. [•] The estimated absorption spectra showed good correlation with the SSC. [•] The estimated absorption spectra gave better prediction of the soluble solids content and firmness than the scattering spectra. [•] The diffuse reflectance spectra gave comparable prediction accuracies to the μ a spectra. [ABSTRACT FROM AUTHOR]

Abstract: The potential of spatially resolved diffuse reflectance spectroscopy in the 500–1000nm 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 3h (OSMO2). The fresh apple rings were produced from ‘Golden Delicious’ apples at harvest (H) and 5month 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. 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. Industrial relevance: Dried fruit is an important category of processed foods on the market with a worldwide annual production of 9.5×109 kg in 2012, which is 13% higher than the production in 2011 (International Nut and Dried Fruit Council, 2013). Besides the nutritional value the textural properties also have a strong impact on the consumption quality as they determine the taste sensation and digestibility. Therefore, the food industry is demanding fast and non-destructive measurement techniques which could be used on-line/in-line for the evaluation of the texture and microstructure of individual products and for realtime process control and optimization. The spatially resolved spectroscopy technique investigated in this research allows to detect textural quality differences in dried food products (apples in this study) and has high potential for use in the food industry thanks to the non-invasive, sensitive and fast interaction of the propagating light with food matrices. [Copyright &y& Elsevier]

Abstract: Non-invasive and non-destructive Near Infrared Reflectance Spectroscopy (NIRS) analysis of pork quality parameters is challenging due to the presence of a structured skin layer. The optical characterization (absorption coefficient, scattering coefficient and anisotropy factor) of porcine skin tissue can help in a better understanding of the light-tissue interaction, more efficient instrumental sensor designs and data modeling. For this purpose, double integrating spheres combined with an unscattered transmittance measurement system working in the range 1150–2250nm (interval step of 10nm) were used for optical characterization of pig epidermis and dermis. The estimated pig skin absorption coefficient spectra were dominated by water, while scattering coefficient spectra showed a steady decreasing tendency with increasing wavelength, except at strong absorption bands. The anisotropy factor spectra showed a stable value for each layer, although also some signatures were observed at strong absorption bands. Industrial relevance: A novel double integrating sphere system combined with an unscattered transmittance detector based both on a supercontinuum laser is used for optical characterization (absorption, scattering and angular scattering distribution) of pig skin tissues (epidermis and dermis) in the 1150–2250nm wavelength range. The estimated data reported are relevant to understand individual effects of absorption, scattering and angular scattering distribution of NIR light through the tissue. Moreover, it can be used for simulating non-destructive NIRS measurement what can have an impact in the advance of NIRS technology toward in vivo/intact analysis. [Copyright &y& Elsevier]

Abstract: Optical properties of pig subcutaneous adipose tissue were estimated using double integrating sphere (DIS) measurements in combination with an inverse adding doubling (IAD) light propagation model. Total reflectance, total transmittance and unscattered transmittance were measured for the wavelength range 1150–2250nm with 10nm resolution. These measurements were used to estimate the bulk optical properties (absorption coefficient, scattering coefficient and anisotropy factor) of 10 Iberian pig adipose tissue samples. The estimated absorption coefficient spectra were dominated by water and lipid absorption bands, the main chemical components of the adipose tissue. These values showed a suitable match with the theoretical values calculated based on the average composition of the tissue. The obtained scattering coefficient spectra showed a smooth decrease with increasing wavelength, which is typical for biological tissues. The anisotropy factor spectra of adipose tissue were obtained, which describe the angular scattering pattern, instead of using a fixed value for the estimation procedure. The optical characterization described in this paper is crucial for a better understanding of the impact of pure absorption and scattering on the NIR spectra collected by a single measurement in the laboratory, process line at the slaughterhouse or on the farm. Moreover, the estimated data reported in this study would promote a more efficient sensor design and data processing optimization. Industrial relevance: This paper provides an optical characterization (absorption, scattering and angular scattering distribution) of pig adipose tissues in a wide near-infrared wavelength range (1150–2250nm) based on a novel spectroscopic setup. The estimated data reported are relevant to promote the design of innovative NIRS sensors and the development of new modeling procedures in order to optimize the non-destructive analysis of intact adipose tissues. This can have an important impact on the implementation of NIRS quality control systems in the agro-industry. [Copyright &y& Elsevier]

Abstract: Continuous wave (CW) and time-resolved (TRS) near infrared (NIR) reflectance measurements were carried out on ‘Conference’ pear fruit. While the absorption coefficient spectra obtained from the TRS measurements were dominated by the overtone of the hydroxyl moiety at 975nm, the scattering coefficient spectra were almost flat. The spectral data were used to construct calibration models for the soluble solids content (SSC) and Magness Taylor firmness of ‘Conference’ pear fruit. Reasonable models for SSC (RMSEP=0.44 °Brix) were obtained when the CW spectra in the range 780–1700nm were used, but not when the range was limited to that of the TRS equipment (875–1030nm). No satisfactory calibration model could be established between the TRS absorption coefficient spectrum and SSC. With none of the spectroscopic techniques could significant calibration models for firmness be constructed, although a highly nonlinear relationship between scattering coefficients at 900nm and firmness was observed. [Copyright &y& Elsevier]

• TRS absorption coefficients are more related to pigment and water of the fruit flesh. • SRS absorption coefficients are strongly affected by pigments in the fruit skin. • Fruit softening was accompanied by increasing values of reduced scattering coefficient. • TRS and SRS capture valuable information on the changes in flesh texture. Bulk optical properties, in terms of absorption (μ a) and reduced scattering coefficients (μ ′ s), can be used for the non-destructive monitoring of fruit quality during ripening. In this study, the performance of time-resolved (TRS) and spatially-resolved (SRS) spectroscopy were compared by analyzing 'Braeburn' apples over a 21 d period of ripening. Nine batches of 20 apples each were measured on the blush side by TRS (540−1064 nm) and SRS (550−1000 nm). Every fruit was analyzed for skin color, texture characteristics, relative internal space volume (RISV), total solid soluble and titratable acidity contents. TRS absorption spectra showed two maxima, the highest at 980 nm (water) and the second at 670 nm (chlorophyll), while in SRS spectra the main peak was measured at 550 nm (anthocyanins) followed by that at 670 nm. The values of μ a 580 SRS and of μ a 670 SRS were much higher than those measured at the same wavelengths by TRS suggesting that TRS and SRS actually explore the apple tissue (skin and/or flesh) in a different way. The values of μ a 980 TRS were higher than those of μ a 980 SRS , probably due to the fact that water content was lower in the skin (mostly probed by SRS) than in the flesh (mostly probed by TRS). No significant correlations were found between μ a 580 SRS and μ a 580 TRS and between μ a 980 SRS and μ a 980 TRS but a low positive relationship was observed between μ a 670 TRS and μ a 670 SRS. On the contrary, high correlations were found between μ a 670 SRS and the spectral index I AD (index of absorbance difference) related to chlorophyll in the skin and between μ a 580 SRS and the spectral index ARI (anthocyanin reflectance index), related to anthocyanin content in the peel, suggesting that μ a 580 SRS is linked to the development of the red color in the peel. Both μ a 670 TRS and μ a 670 SRS decreased during fruit ripening, indicating a decline in chlorophyll in the flesh and skin, respectively. During the shelf life period, apples became soft and mealy, as mechanical and acoustic parameters decreased and RISV increased. Fruit softening was accompanied by increasing values of both μ ′ sTRS and μ ′ sSRS. The μ ′ sTRS and μ ′ sSRS were positively related to each other, were positively correlated to RISV and negatively related to mechanical and acoustic parameters. Both the TRS and SRS technique were able to follow ripening processes in 'Braeburn' apples during the shelf life period, as absorption phenomena were related to changes in pigments present in the fruit flesh and skin, while scattering events mirrored changes in the flesh texture. [ABSTRACT FROM AUTHOR]