Visible-NIR ‘point’ spectroscopy in postharvest fruit and vegetable assessment: The science behind three decades of commercial use

The application of visible (Vis; 400–750 nm) and near infrared red (NIR; 750–2500 nm) region spectroscopy to assess fruit and vegetables is reviewed in context of ‘point’ spectroscopy, as opposed to multi- or hyperspectral imaging. Vis spectroscopy targets colour assessment and pigment analysis, while NIR spectroscopy has been applied to assessment of macro constituents (principally water) in fresh produce in commercial practice, and a wide range of attributes in the scientific literature. This review focusses to key issues relevant to the widespread implementation of Vis-NIR technology in the fruit sector. A background to the concepts and technology involved in the use of Vis-NIR spectroscopy is provided and instrumentation for in-field and in-line applications, which has been available for two and three decades, respectively, is described. A review of scientific effort is made for the period 2015 - February 2020, in terms of the application areas, instrumentation, chemometric methods and validation procedures, and this work is critiqued through comparison to techniques in commercial use, with focus to wavelength region, optical geometry, experimental design, and validation procedures. Recommendations for future research activity in this area are made, e.g., application development with consideration of the distribution of the attribute of interest in the product and the matching of optically sampled and reference method sampled volume; instrumentation comparisons with consideration of repeatability, optimum optical geometry and wavelength range). Recommendations are also made for reporting requirements, viz. description of the application, the reference method, the composition of calibration and test populations, chemometric reporting and benchmarking to a known instrument/method, with the aim of maximising useful conclusions from the extensive work being done around the world

Estimation of daily carbon demand in sweet cherry (Prunus avium L.) production

In cherry production, the assimilate supply to the fruit is a crucial factor for growth and formation of quality parameters. The assimilate supply per fruit is limited by the relative growth capacity of trees, represented by the leaf area to fruit ratio (LA:F). In the present study, the required leaf area per fruit (LAdemand [cm² fruit-1]) of two sweet cherry cultivars, 'Bellise' and 'Regina', was estimated in 2018 and 2019, based on measured and interpolated values of fruit growth and fruit respiration rates. LAdemand changed daily with an overall increase during fruit development, showing average values in stage III in 2018 and 2019 of 139 cm² and 175 cm² in 'Bellise', while 199 cm² and 212 cm² were found in 'Regina', respectively. Estimated LAdemand for both cultivars was compared with measurements in cherries grown on girdled branches. In both years, estimated values exceeded measured values. In both years, positive correlation between LA:F and fresh mass, soluble solids content, and coloration was observed. The data obtained can be applied to evaluate the tree’s crop load for precise management

Modeling of Individual Fruit-Bearing Capacity of Trees Is Aimed at Optimizing Fruit Quality of Malus x domestica Borkh. 'Gala'

The capacity of apple trees to produce fruit of a desired diameter, i.e., fruit-bearing capacity (FBC), was investigated by considering the inter-tree variability of leaf area (LA). The LA of 996 trees in a commercial apple orchard was measured by using a terrestrial two-dimensional (2D) light detection and ranging (LiDAR) laser scanner for two consecutive years. The FBC of the trees was simulated in a carbon balance model by utilizing the LiDAR-scanned total LA of the trees, seasonal records of fruit and leaf gas exchanges, fruit growth rates, and weather data. The FBC was compared to the actual fruit size measured in a sorting line on each individual tree. The variance of FBC was similar in both years, whereas each individual tree showed different FBC in both seasons as indicated in the spatially resolved data of FBC. Considering a target mean fruit diameter of 65 mm, FBC ranged from 84 to 168 fruit per tree in 2018 and from 55 to 179 fruit per tree in 2019 depending on the total LA of the trees. The simulated FBC to produce the mean harvest fruit diameter of 65 mm and the actual number of the harvested fruit >65 mm per tree were in good agreement. Fruit quality, indicated by fruit's size and soluble solids content (SSC), showed enhanced percentages of the desired fruit quality according to the seasonally total absorbed photosynthetic energy (TAPE) of the tree per fruit. To achieve a target fruit diameter and reduce the variance in SSC at harvest, the FBC should be considered in crop load management practices. However, achieving this purpose requires annual spatial monitoring of the individual FBC of trees

Estimation of daily carbon demand in sweet cherry (Prunus avium L.) production

In cherry production, the assimilate supply to the fruit is a crucial factor for growth and formation of quality parameters. The assimilate supply per fruit is limited by the relative growth capacity of trees, represented by the leaf area to fruit ratio (LA:F). In the present study, the required leaf area per fruit (LAdemand [cm² fruit-1]) of two sweet cherry cultivars, 'Bellise' and 'Regina', was estimated in 2018 and 2019, based on measured and interpolated values of fruit growth and fruit respiration rates. LAdemand changed daily with an overall increase during fruit development, showing average values in stage III in 2018 and 2019 of 139 cm² and 175 cm² in 'Bellise', while 199 cm² and 212 cm² were found in 'Regina', respectively. Estimated LAdemand for both cultivars was compared with measurements in cherries grown on girdled branches. In both years, estimated values exceeded measured values. In both years, positive correlation between LA:F and fresh mass, soluble solids content, and coloration was observed. The data obtained can be applied to evaluate the tree’s crop load for precise management

Coulomb fragmentation and Coulomb fission of relativistic heavy-ions and related nuclear structure aspects

The Coulomb excitation of 208Pb projectiles has been studied at an energy of 640 A MeV. Cross sections for the excitation of the two-phonon giant dipole resonance were measured for different targets, and show clear evidence for a two-step electromagnetic excitation mechanism. The experimental cross sections exceed those calculated in the harmonic oscillator approximation by a factor of 1.33 ± 0.16. The deduced 27-decay probability is consistent with the expectation in the harmonic limit. Finally, the excitation of the two-phonon giant dipole resonance in the deformed and fissile nucleus 238U is discussed

Identification of the apple firmness: two case studies

Firmness tests were performed with peeled and entire fruits of Elstar and Jonagold apple cultivars for identification and comparison. The normal distribution of the tested population was acceptable (level: 95%). The green and the red sides did not show differences within the cultivar but they were different in firmness. There was not significant difference between the flesh tissue firmness values, however the firmness of the entire (not peeled) fruits was different. This result was caused by the effect of the peel. The variability of the firmness with Jonagold was caused by the peel, but such a result was not found with Elstar. The test of the peel effect would be interesting with different cultivars and a sequence according to the firmness can be estimated. &nbsp