Determining the optical properties of apple tissue and their dependence on physiological and morphological characteristics during maturation. Part 1: Spatial frequency domain imaging

Lohner, Stefan A.; Biegert, Konni; Nothelfer, Steffen; Hohmann, Ansgar; McCormick, Roy; Kienle, Alwin

doi:10.1016/j.postharvbio.2021.111647

Cited by 17 publications

(17 citation statements)

References 60 publications

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“…To our knowledge, this is the first time that the optical properties of apple tissue were determined from different sizes of ROI. Based on SFDI measurements of “Braeburn” apples, Lohner et al (2021) recently observed that μ a was about 0.01–0.04 mm –1 for the cortex tissue at 656 nm, which covers the μ a range at 630 nm in this study (0.021–0.024 mm –1 ), if the value from the ROI of 10 × 10 is excluded. As known from the previous work, the wavelength of 656 nm is mainly related to the presence of chlorophyll b ( Merzlyak and Solovchenko, 2002 ), and it is thus reasonable that the μ a value is larger than the present results.…”

Section: Resultssupporting

confidence: 67%

“…However, most of the efforts were made to obtain the optical property of single point (usually one pixel in the tissue). To our knowledge, SFDI is the sole technique which is capable of measuring the optical property mappings (in the axial and transverse directions), and till now, only apple and pear fruit have been studied ( Hu et al, 2020a ; He et al, 2021 ; Lohner et al, 2021 ). The apple flesh, as a relatively uniform tissue, should present homogeneous optical property mapping, which was confirmed by the results observed in this paper.…”

Section: Discussionmentioning

confidence: 99%

“…By demodulating the emitted images under structured illuminations with changed frequencies and phases, the μ a and μ s ′ can be estimated using inverse algorithm based on appropriate light transfer models ( Hu et al, 2016 ). Owing to the capabilities of wide-field and non-contact imaging, and depth-varying and signal-enhanced characterization ( Gigan, 2017 ), SFDI has been applied for measuring the optical property mappings of apple, kiwi, mango, and pear ( Hu et al, 2020a ; He et al, 2021 ; Lohner et al, 2021 ; Sun et al, 2021 ). However, no reports were found on the prediction of apple quality properties based on the measured optical property mappings.…”

Section: Introductionmentioning

confidence: 99%

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Optical Property Mapping of Apples and the Relationship With Quality Properties

Peng

Zhang²,

Sun

et al. 2022

Front. Plant Sci.

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This paper reports on the measurement of optical property mapping of apples at the wavelengths of 460, 527, 630, and 710 nm using spatial-frequency domain imaging (SFDI) technique, for assessing the soluble solid content (SSC), firmness, and color parameters. A laboratory-based multispectral SFDI system was developed for acquiring SFDI of 140 “Golden Delicious” apples, from which absorption coefficient (μa) and reduced scattering coefficient (μs′) mappings were quantitatively determined using the three-phase demodulation coupled with curve-fitting method. There was no noticeable spatial variation in the optical property mapping based on the resulting effect of different sizes of the region of interest (ROI) on the average optical properties. Support vector machine (SVM), multiple linear regression (MLR), and partial least square (PLS) models were developed based on μa, μs′ and their combinations (μa × μs′ and μeff) for predicting apple qualities, among which SVM outperformed the best. Better prediction results for quality parameters based on the μa were observed than those based on the μs′, and the combinations further improved the prediction performance, compared to the individual μa or μs′. The best prediction models for SSC and firmness parameters [slope, flesh firmness (FF), and maximum force (Max.F)] were achieved based on the μa × μs′, whereas those for color parameters of b* and C* were based on the μeff, with the correlation coefficients of prediction as 0.66, 0.68, 0.73, 0.79, 0.86, and 0.86, respectively.

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Section: Resultssupporting

confidence: 67%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Optical Property Mapping of Apples and the Relationship With Quality Properties

Peng

Zhang²,

Sun

et al. 2022

Front. Plant Sci.

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“…The examined apple samples are identical to those investigated by Lohner et al [21,45]. They were collected from the research orchard of the Kompetenzzentrum Obstbau Bodensee ( 47 • 46 ′ 01.8 ′′ N 9 • 33 ′ 30.3 ′′ E) during the 2019 harvest season between July and November.…”

Section: Fruit Samplesmentioning

confidence: 99%

Chlorophyll- and anthocyanin-rich cell organelles affect light scattering in apple skin

Lohner

Biegert

Hohmann

et al. 2022

Photochem Photobiol Sci

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Apple skin contains several groups of strongly absorbing cell organelles with pigments that change dynamically in type and concentration during fruit maturation. Chlorophylls and carotenoids, both primarily involved in photosynthesis, are found in the grana of chloroplasts, while anthocyanin vacuolar inclusions (AVIs) accumulate for light protection in red-skinned cultivars. A Mie model describing light scattering by absorbing spherical particles in a non-absorbing medium allowed to theoretically investigate the explicit influence of grana and AVIs on the effective scattering coefficient ′ s and the absorption coefficient a . The reconstruction of the complex refractive indices of the organelles predicted anomalous dispersion, i.e., a local increase in the real part of the refractive index in the spectral regions with high chlorophyll and anthocyanin absorption, in agreement with the Kramers-Kronig relations. As a result, peaks in ′ s were predicted to be shifted to longer wavelengths compared to the corresponding a bands. This selective scattering effect was confirmed experimentally with integrating sphere measurements for red-or green-skinned apple samples of the cultivars 'Elstar', 'Gala' or 'Jonagold'. Comparison between simulations and measurements indicated that the Soret bands of chlorophyll a and chlorophyll b are at 435 nm and 469 nm, respectively, and overlap with the absorption of carotenoids, whose red-most edge is at 488 nm. For anthocyanin absorption, a pronounced blue shift from 550 to 520 nm was observed, indicating structural or chemical changes of AVIs.

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“…From an experimental point of view, extensive studies on the optical properties of apple tissue are available. Using various time-, spatially-, and spatial frequency-resolved techniques, a characteristic decrease in µ ′ s was observed during maturation (Van Beers et al, 2017, Seifert et al, 2015, Lohner et al, 2021, while an increase in µ ′ s was partially observed during storage (Vanoli et al, 2020, Rowe et al, 2014. Spatially resolved scattering property studies showed a high degree of heterogeneity with a tendency for µ ′ s to increase from the core to the skin (Lohner et al, 2021).…”

Section: Introductionmentioning

confidence: 97%