Dimitrios S. Kasampalis

Heat stress is considered as the most important limiting factor for the productivity of beans and the emerging increase in global temperature is estimated to have a strong negative impact on its yield. In this context, the green bean industry is looking for means to mitigate these adverse effects. Foliar application of amino acids-based bi-ostimulants, supplemented with silicon or sulfur, has been reported to have beneficial effects on bean crops to mitigate the effects of various stresses but not of heat stress, yet. Amino16 is a commercial biostimulant with 16 L-amino acids and was used as a basis so that two novel products; Amino16+Si and Amino16+S were further produced. Their efficacy was tested upon foliar application in two consecutive growing seasons (early and late) of green beans. The mitigation of the effects of heat stress in green bean crops was not achieved upon the combined application of amino acids supplemented with sulfur or silicon at several rates. Obviously, higher concentrations of sulfur and silicon are required to induce beneficial effects, and probably through drench application, especially in crops with high sulfur demand, such as beans, while silicon requires another form, other than silicon dioxide, which is not easily absorbed by the plant’s roots.

The objective of this study was to evaluate the feasibility of using visible, near-infrared, and short-wave infrared (VIS/NIR/SWIR) spectroscopy coupled with chemometrics for non-destructive prediction of nutritional components in Galia-type melon fruit. A total of 175 fully ripened melons were analyzed for soluble solids content (SSC), dry matter (DM), pH, and titratable acidity (TA) using partial least squares regression (PLSR), principal components regression (PCR), and multilinear regression (MLR) models. Reflectance spectra were captured at three fruit locations (pedicel, equatorial, and blossom end) in the 350–2500 nm range. The PLSR models yielded the highest accuracy, particularly for SSC (R = 0.80) and SSC/TA (R = 0.79), using equatorial zone data. Variable selection using the genetic algorithm (GA) successfully identified the spectral regions critical for each nutritional parameter at the pedicel, equatorial, and blossom end areas. Key wavelengths for SSC were found around 670–720 nm and 900–1100 nm, with important wavelengths for pH prediction located near 1450 nm, and, for dry matter, in the ranges 1900–1950 nm. Variable importance in projection (VIP) analysis confirmed that specific wavelengths between 680 and 720 nm, 900 and 1000 nm, 1400 and 1500 nm, and 1900 and 2000 nm were consistently critical in predicting the SSC, DM, and SSC/TA ratio. The highest VIP scores for SSC prediction were noted around 690 nm and 950 nm, while dry matter prediction was influenced most by wavelengths in the 1450 nm to 1950 nm range. This study demonstrates the potential of VIS/NIR/SWIR spectroscopy for rapid, non-destructive melon quality assessment, with implications for commercial postharvest management.

This study evaluates the potential of integrating visible and near-infrared (visNIR) spectroscopy, color analysis, and firmness testing for non-destructive tomato quality assessment and shelf-life prediction. Tomato fruit (cv. HM1823) harvested at four ripening stages were monitored over 12 days at 22 °C to investigate ripening stage-specific variations in key quality parameters, including color (hue angle), firmness (compression), and nutritional composition (pH, soluble solids content, and titratable acidity ratio). Significant changes in these parameters during storage highlighted the need for advanced tools to monitor and predict quality attributes. Spectral data (340–2500 nm) captured using advanced and cost-effective portable spectroradiometers, coupled with chemometric models such as partial least squares regression (PLSR), demonstrated reliable predictions of shelf-life and nutritional quality. The near-infrared spectrum (900–1700 nm) was particularly effective, with variable selection methods such as genetic algorithm (GA) and variable importance in projection (VIP) scores enhancing model accuracy. This study highlights the promising role of visNIR spectroscopy as a rapid, non-destructive tool for optimizing postharvest management in tomato. By enabling real-time quality assessments, these technologies support sustainable agricultural practices through improved decision-making, reduced postharvest losses, and enhanced consumer satisfaction. The findings also validate the utility of affordable spectroradiometers, offering practical solutions for stakeholders aiming to balance cost efficiency and reliability in postharvest quality monitoring.

External and internal changes in tomato fruit harvested at various ripening stages (from mature green to red ripe) were monitored during postharvest storage at 22 oC for 12 days. Non-destructive measurements of color, compression firmness and spectral reflectance data were captured with two portable, but differently technologically advanced spectroradiometers (a PSR+ 3500, Spectral Evolution and a DLP NIR Nano Scan, Texas Instruments) spectroradiometers in the visible-near infrared (visNIR) (340-2500 nm) or only the NIR (900-1700 nm) region. Significant changes in color, firmness, pH and soluble solids to titratable acidity ratio were observed during storage, especially in the less ripe fruits and were reliably assessed by all nondestructive techniques, especially by the spectral reflectance data captured at the 340-2500 nm part with the most sophisticated device. In general, visNIR spectroscopy, combined with chemometric techniques, is a powerful non-destructive method for assessing tomato quality and predicting shelf life. Although using both the visible and the near infrared part of the spectrum (340-2500 nm) provides more accurate assessments, the NIR part (900-1700 nm) alone can support reliable predictions, while the consumers are not capable of perceiving most of the changes that accompany postharvest ripening before consuming the products.

The market demand for baby leaf lettuce is constantly increasing, while safety has become one of the most important traits in determining consumer preference driven by human health hazards concerns. In this study, the performance of visible and near-infrared (vis/NIR) spectroscopy was tested in discriminating pesticide-free against pesticide-treated lettuce plants. Two commercial fungicides (mancozeb and fosetyl-al) and two insecticides (deltamethrin and imidacloprid) were applied as spray solutions at the recommended rates on baby leaf lettuce plants. Untreated-control plants were sprayed with water. Reflectance data in the wavelength range 400–2500 nm were captured on leaf samples until harvest on the 10th day upon pesticide application, as well as after 4 and 8 days during post-harvest storage at 5 °C. In addition, biochemical components in leaf tissue were also determined during storage, such as antioxidant enzymes’ activities (peroxidase [POD], catalase [CAT], and ascorbate peroxidase [APX]), along with malondialdehyde [MDA] and hydrogen peroxide [H₂O₂] content. Partial least square discriminant analysis (PLSDA) combined with feature-selection techniques was implemented, in order to classify baby lettuce tissue into pesticide-free or pesticide-treated ones. The genetic algorithm (GA) and the variable importance in projection (VIP) scores identified eleven distinct regions and nine specific wavelengths that exhibited the most significant effect in the detection models, with most of them in the near-infrared region of the electromagnetic spectrum. According to the results, the classification accuracy of discriminating pesticide-treated against non-treated lettuce leaves ranged from 94% to 99% in both pre-harvest and post-harvest periods. Although there were no significant differences in enzyme activities or H₂O₂, the MDA content in pesticide-treated tissue was greater than in untreated ones, implying that the chemical spray application probably induced a stress response in the plant that was disclosed with the reflected energy. In conclusion, vis/NIR spectroscopy appears as a promising, reliable, rapid, and non-destructive tool in distinguishing pesticide-free from pesticide-treated lettuce products.

Profitable hydroponic production requires high quality fresh water, which is often not available for agricultural use, while desalinisation of salty water is an expensive and unsustainable technology. In the present study, we assessed the effect of mild salinity stress during the soilless cultivation of fresh peppermint and spearmint in the floating system on biomass yield, produce quality and plant secondary metabolite content. Peppermint and spearmint plants were grown for 25 days on a nutrient solution (NS) supplemented with three different NaCl concentrations (0 mM, 10 mM or 20 mM NaCl). The plant height, root length, fresh and dry weight were recorded and composition was determined on fresh tissue. The composition of essential oil was determined upon hydrodistillation and that of polyphenolic compounds by targeted ultra-performance liquid chromatography coupled with mass spectrometer (UPLC-MS/MS). Plant growth was not suspended by the addition of NaCl in the NS, except for the plant height at the highest salinity level. In peppermint, the nutritional composition was not affected by the salinity, whereas it was significantly improved in spearmint as confirmed by the nitrate content decrease and the total antioxidant capacity, total soluble phenol, total carotenoid and essential oil content increases. Simultaneously, no effect of the salinity on essential oil or polyphenolic composition in both plants was induced. In conclusion, peppermint and spearmint production is feasible in the floating system even under mild salinity conditions, without negatively affecting either the crop yield or the plant's essential oil or phenolic composition. Indeed, low salinity levels improved the nutritional composition of spearmint plants.

BACKGROUND: Nutritional quality in bell pepper is related to the ripening stage of the fruit at harvest and postharvest storage. Its determination requires time‐consuming, tissue‐destructive, analytical laboratory techniques. The objective of this study was to investigate the effect of ripening stage and of postharvest storage period on fruit nutritional quality, and whether it is feasible to develop reliable models for assessing the nutritional components in peppers using non‐destructive methods. The dry matter, soluble solids, ascorbic acid, phenolics, chlorophylls, carotenoids and the total antioxidant capacity were determined in bell pepper fruits at six ripening stages, from green to full red, during storage at 10 °C for 8 days. Color, chlorophyll fluorescence, visible/near infrared (Vis/NIR) spectroscopy, red‐green‐blue (R‐G‐B) and red‐green‐near infrared (R‐G‐NIR) digital imaging were tested for assessing the nutritional quality of peppers.RESULTS: The nutritional composition was mainly affected by the ripening stage of bell pepper fruits at harvest and only to a small degree by the storage period. Indeed, the more advanced ripening stage of fruit at harvest resulted in superior nutritional quality. Most of the non‐destructive techniques reliably predicted the internal quality of the fruit. The genetic algorithm (GA), the variable importance in projection (VIP) scores, and the variable inflation factor (VIF) tests identified nine distinct regions and four specific wavelengths on the whole visible/NIR electromagnetic spectrum that exhibited the most significant effect in the assessment of the nutritional components.CONCLUSION: It is possible to predict individual nutritional components in bell pepper fruit reliably and non‐destructively, and irrespective of the ripening stage of fruits at harvest. © 2021 Society of Chemical Industry.

A floating system was established in a heated glass greenhouse in order to investigate whether the effect of amino acids (0.25 or 0.50% of a commercial amino acid (AA) solution Amino16^®) during peppermint and spearmint production on plant developmental and nutritional status may be in part attributed to salinity induced osmotic stress. For this reason, in some nutrient solutions, three levels of salinity were induced by adding 0, 10, or 20 mM NaCl. According to the results, it can be concluded that spearmint is mostly favored by the highest amino acid supplement of the nutrient solution (0.50%) in terms of a substantial improvement of the antioxidant nutritional quality (by up to 130%) at the expense of a reduced biomass production (by 2O₂ and maintaining the proline content at the normal levels. The osmotic stress that was induced by the excessive AA concentration and confirmed by the chlorophyl fluorescence variations was probably related to NH₄⁺ excess supply in the growing media and was not associated with the elevated electrical conductivity in the solution. The absence of any adverse stressful consequences upon the addition of 20 mM NaCl may be attributed to the high salt tolerance of peppermint and spearmint species.

Background: Quality and safety of potato is both cultivar and postharvest management dependent. The precise assessment of freshness and cultivar are complex tasks requiring time-consuming, expensive, and destructive techniques. Method: Potatoes from three commercial cultivars were stored for 5 months at 5 °C. Color and chlorophyll fluorescence were recorded, Red-Green-Blue (R-G-B), Red-Green-Near infrared (R-G-NIR) and Red-Blue-Near infrared (R-B-NIR) digital images, as well as hyperspectral images were acquired both on the external periderm of the tuber and in the inner flesh part. Partial least square regression (PLSR) and discriminant analysis, combined with feature selection techniques were implemented, in order to assess the potato freshness and to classify them into the respective genotypes. Results: The PLSR analysis of visible/near infrared (Vis/NIR) spectra reflectance most reliably predicted potato freshness, with a cross-validated regression coefficient equal to 0.981 and 0.947, as determined by external or internal measurements, respectively. Variance inflation factor, variable importance scores, and genetic algorithms identified specific wavelength regions that mostly affected the accuracy of the model in terms of strongest regression and lowest collinearity and root mean cross validation error. Conclusions: Vis/NIR spectra reflectance data from the skin of the potato tubers may be reliably used in the assessment of postharvest storage life, as well as in the cultivar discrimination process.

The present study investigated the potential of fresh peppermint (Mentha × piperita L.) and spearmint (Menthaspicata L.) production on a floating raft system combined with a commercial protein hydrolysate supplement (Amino16^®) in a nutrient solution aiming to improve plant product quality. Three levels of the protein hydrolysate solution (0, 0.25 and 0.50%) were added in the nutrient solution, and the plants were harvested after twenty-four days. Plant growth characteristics were recorded, and nutritional, essential oil and polyphenolic composition were determined in fresh tissue. The addition of protein hydrolysates did not affect the fresh or dry weight but reduced plant height. Nitrate content significantly decreased, while total chlorophyll and essential oil content increased in both species. Moreover, the protein hydrolysate solution further increased total antioxidant capacity, total soluble phenol and carotenoid contents in spearmint plants, while it did not affect the essential oil and polyphenolic composition in both species. In conclusion, protein hydrolysates solution may be added in the nutrient solution, to improve the quality of peppermint and spearmint grown in a floating system, without adverse effects on crop yield or the essential oil and polyphenolic profile.