Characteristics of pigment composition and colour value by the difference of harvesting times in Korean red pepper varieties (Capsicum annuum, L.)

Effects of moisture content and packaging on color stability of red pepper (Capsicum annuum L.) powder

The color stability and quality changes of red pepper powder of various initial moisture content (7%, 10%, and 13%) and packaged with different materials, low-density polyethylene (LDPE) and nylon layered polyethylene (Ny/PE) film pouches or plastic and glass bottles, were compared during storage at 20 °C for 126 days. In the 7% moisture content sample packaged in LDPE film and plastic bottles, the L* and b*-values increased from 48.2 ± 0.7 and 15.4 ± 1.1 to 65.2-65.9 and 29.5-30.3, respectively, while the a*-value decreased from 26.1 ± 0.7 to 14.2-15.9, indicating a noticeable color change from red to orange. However, the decrease in the capsaicinoid and free sugar content of red pepper powder over time was found to have no significant correlation with moisture content and packaging type. As a result, the color change during the long-term storage of red pepper powder was greatly influenced by the initial moisture content and gas permeability of the packaging material.

Correlation of Carotenoids Content and ASTA Values of Pepper (Capsicum chinense) Genetic Resources

In this study, 226 Capsicum chinense genetic resources were analyzed using high-performance liquid chromatography and a spectrophotometer to measure and compare their carotenoid content and American Spice Trade Association (ASTA) color values, respectively. The total carotenoid content and ASTA values of the 226 pepper genetic resources were found to be in the range of 7.04–2430.85 mg/100 g dry weight (DW) and 0–221.32, respectively. Capsanthin, capsorubin, lutein, zeaxanthin, antheraxanthin, violaxanthin, α-carotene, β-carotene, and β-cryptoxanthin were the individual carotenoids studied. The average content of each carotenoid (n = 226) in mg/100 g DW was as follows: capsanthin (325.77), antheraxanthin (136.34), capsorubin (82.36), β-carotene (59.11), violaxanthin (46.54), zeaxanthin (43.21), α-carotene (13.91), β-cryptoxanthin (9.67), and lutein (2.72). A strong positive correlation was observed between total carotenoid content and ASTA value (r = 0.965). Likewise, the individual carotenoid content and ASTA value revealed a strong correlation, such as antheraxanthin (r = 0.964), capsanthin (r = 0.946), and capsorubin (r = 0.858). Three genetic resources with a total carotenoid content above 2000 mg/100 g DW were obtained, such as IT261426 (2430.85 mg/100 g DW), IT183657 (2077.55 mg/100 g DW), and IT261213 (2062.54 mg/100 g DW). The findings of this study will assist in the selection of genetic resources with high carotenoid content and ASTA value that can be used to develop and breed new pepper varieties. Also, detailed results of ASTA value correlation with carotenoids in C. chinense genetic resources are provided.

Reducing extreme weather impacts in greenhouses: the effect of a new passive climate control system on nutritional quality of pepper fruits

BACKGROUND

Environmental conditions affect the quality of the fruits and their organoleptic properties. In low-tech greenhouses, these environmental conditions are frequently not optimal for crops. Therefore, the present study demonstrates the effects of the use of an integrated passive heating and cooling system in a greenhouse located in the Mediterranean area on the quality of pepper fruits.

RESULTS

The results indicate that the passive system utilized (i) improved many parameters, such as average weight of fruits, °Brix, glucose and fructose content, and P and K content; (ii) increased the values of b* and h_ab *; and (iii) reduced total phenolic compounds, total amino acids content, and Fe and Zn content. However, the degree of the effect of the climatic factors on these parameters was also affected by harvest time.

CONCLUSION

This novel study highlights the possibility of improving the nutritional quality of pepper fruits by modifying the environmental conditions through the use of passive heating and cooling systems at the same time as reducing the carbon footprint. © 2021 Society of Chemical Industry.

Physiological changes in green and red cherry tomatoes after photocatalytic ethylene degradation using continuous air flux

In this work photocatalytic ethylene degradation (TiO₂-UV) was applied in green cherry tomatoes with the aim to control biochemical and physiological changes during ripening. Photocatalytic process was performed at 18 °C  ±  2 °C and 85% HR for 10 days using continuous air flux. Ethylene, O₂ and CO₂ concentration from cherry tomatoes under TiO₂-UV and control (c) fruits, were measured by GC-MS for 10 days. After that, the tomatoes were stored for 20 days. During the photocatalysis process, ethylene was completely degraded and control fruits, the ethylene was 28.73 nL g^-1. Respiration rate was lower for fruits under TiO₂-UV than control. During storage period, cherry tomatoes treated by TiO₂-UV, showed lower ethylene concentration, respiration rate, total soluble solid, lycopene, sugar and organic acid content than control showing that the fruits treated with photocatalysis did not reach the full maturity. In addition, all the cherry tomatoes showed different maturity stages. Fungal incidence was higher in control fruits than fruits treated with photocatalysis. This research showed for the first time that photocatalytic technology preserved the physiological quality of cherry tomatoes for 30 days of storage, being a promised technology to preserve cherries tomatoes.

Transcriptomic analysis of a wild and a cultivated varieties of Capsicum annuum over fruit development and ripening

Chili pepper (Capsicum annuum) is one of the most important crops worldwide. Its fruits contain metabolites produced over the maturation process like capsaicinoids and carotenoids. This metabolic process produces internal changes in flavor, color, texture, and aroma in fruits to make them more attractive for seed dispersal organisms. The chiltepin (C. annuum L. var. glabriusculum) is a wild variety of the C. annuum L. species that is considered a source of genetic resources that could be used to improve the current chili crops. In this study, we performed a transcriptomic analysis on two fruit maturation stages: immature stage (green fruit) and mature stage (red fruit) of a wild and a cultivated pepper variety. We found 19,811 genes expressed, and 1,008 genes differentially expressed (DEGs) in at least one of the five contrast used; 730 DEGs were found only in one contrast, and most DEGs in all contrasts were downregulated. GO enrichment analysis showed that the majority of DEGs are related to stress responses. KEGG enrichment analysis detected differences in expression patterns in metabolic pathways related to phenylpropanoid biosynthesis, secondary metabolites, plant hormone signal transduction, carotenoid biosynthesis and sesquiterpenoid and triterpenoid biosynthesis. We selected 105 tomato fruit ripening-related genes, and found 53 pepper homologs differentially expressed related to shape, size, and secondary metabolite biosynthesis. According to the transcriptome analysis, the two peppers showed very similar gene expression patterns; differences in expression patterns of genes related to shape, size, ethylene and secondary metabolites biosynthesis suggest that changes produced by domestication of chilli pepper could be very specific to the expression of genes related to traits desired in commercial fruits.

Foliar Application of Zinc Oxide Nanoparticles and Zinc Sulfate Boosts the Content of Bioactive Compounds in Habanero Peppers

The physiological responses of habanero pepper plants (Capsicum chinense Jacq.) to foliar applications of zinc sulphate and zinc nano-fertilizer were evaluated in greenhouse trials. The effect of the supplement on fruit quality of habanero pepper was particularly observed. Habanero pepper plants were grown to maturity, and during the main stages of phenological development, they were treated with foliar applications of Zn at concentrations of 1000 and 2000 mg L-1 in the form of zinc sulfate (ZnSO4) and zinc oxide nanoparticles (ZnO NPs). Additional Zn was not supplied to the control treatment plants. ZnO NPs at a concentration of 1000 mg L-1 positively affected plant height, stem diameter, and chlorophyll content, and increased fruit yield and biomass accumulation compared to control and ZnSO4 treatments. ZnO NPs at 2000 mg L-1 negatively affected plant growth but significantly increased fruit quality, capsaicin content by 19.3%, dihydrocapsaicin by 10.9%, and Scoville Heat Units by 16.4%. In addition, at 2000 ZnO NPs mg L-1 also increased content of total phenols and total flavonoids (soluble + bound) in fruits (14.50% and 26.9%, respectively), which resulted in higher antioxidant capacity in ABTS (2,2'azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)), DPPH (2,2-diphenyl-1-picrylhydrazyl), and FRAP (ferric reducing antioxidant power) (15.4%, 31.8%, and 20.5%, respectively). These results indicate that application of ZnO NPs could be employed in habanero pepper production to improve yield, quality, and nutraceutical properties of fruits.

1H NMR-based metabolomic fingerprinting to determine metabolite levels in serrano peppers (Capsicum annum L.) grown in two different regions

Chili pepper (Capsicum annuum) is the most important and emblematic condiment in Mexican food. Serrano pepper is a variety of C. annuum that is traditionally cultivated in Mexico and commercialized in local markets. The aim of this study was to describe the ¹H NMR metabolomic profiling of the aqueous phase of serrano peppers harvested from two distinct regions, in the states of Veracruz and Oaxaca, Mexico. According to the current results, aspartate citrate, lactate, leucine and sucrose were found at higher amount in the serrano peppers from Veracruz. On the other hand, acetate, formate, fumarate, malonate, phosphocholine, pyruvate and succinate showed the highest abundance in this product from Oaxaca. These are the main metabolites that distinguish one group from the other. The spectrometric method reported presently is characterized by great simplicity, robustness and reproducibility. Thus, this technique can be used for establishing reliable metabolomic fingerprints of serrano peppers grown under different environmental conditions.

RGB color calibration for quantitative image analysis: the "3D thin-plate spline" warping approach

In the last years the need to numerically define color by its coordinates in n-dimensional space has increased strongly. Colorimetric calibration is fundamental in food processing and other biological disciplines to quantitatively compare samples' color during workflow with many devices. Several software programmes are available to perform standardized colorimetric procedures, but they are often too imprecise for scientific purposes. In this study, we applied the Thin-Plate Spline interpolation algorithm to calibrate colours in sRGB space (the corresponding Matlab code is reported in the Appendix). This was compared with other two approaches. The first is based on a commercial calibration system (ProfileMaker) and the second on a Partial Least Square analysis. Moreover, to explore device variability and resolution two different cameras were adopted and for each sensor, three consecutive pictures were acquired under four different light conditions. According to our results, the Thin-Plate Spline approach reported a very high efficiency of calibration allowing the possibility to create a revolution in the in-field applicative context of colour quantification not only in food sciences, but also in other biological disciplines. These results are of great importance for scientific color evaluation when lighting conditions are not controlled. Moreover, it allows the use of low cost instruments while still returning scientifically sound quantitative data.

Biochemical and molecular analysis of some commercial samples of chilli peppers from Mexico

The genus Capsicum provides antioxidant compounds, such as phenolics and carotenoids, into the diet. In Mexico, there is a wide diversity of species and varieties of chilli peppers, a fruit which has local cultural and gastronomic importance. In the present study, the relationship of the carotenoid and phenolic profiles with the RAPD fingerprint of three different commercial cultivars of chilli peppers of seven regions of Mexico was investigated. Through RAPD, the species of chilli were differentiated by means of different primers (OPE-18, MFG-17, MFG-18, C51, and C52). The genetic distance found with OPE 18 was in the order of 2.6. The observed differences were maintained when the chromatographic profile of carotenoids, and the molecular markers were analyzed, which suggest a close relationship between carotenoids and the genetic profile. While the chromatographic profile of phenols and the molecular markers were unable to differentiate between genotypes of chilli peppers. In addition, by using infrared spectroscopy and statistical PCA, differences explained by geographic origin were found. Thus, this method could be an alternative for identification of chilli species with respect to their geographic origin.

Influence of different drying methods on carotenoids and capsaicinoids of paprika (Cv., Jalapeno)

Influence of Refractance Window™ Drying (RWD), a novel contact drying method, on carotenoids, capsaicinoids, Retinol Activity Equivalent (RAE) and Scoville Heat Unit (SHU) of paprika (Cv., Jalapeno) was investigated in comparison with freeze drying (FD), oven drying (OD), and natural convective drying (NCD) methods. Eight carotenoids (capsanthin, capsorubin, capsolutein, β-carotene, β-cryptoxanthin, mutatoxanthin, violaxanthin and zeaxanthin) and five capsaicinoid analogues (capsaicin, dihydrocapsaicin, homodihydrocapsaicin, isodihydrocapsaicin, nordihydrocapsaicin) were identified in paprika. All these components were significantly (P<0.05) decreased by the RWD, FD and OD methods. However, due to ongoing synthesis, the NCD method resulted in higher carotenoids, except violaxanthin and mutatoxanthin, and capsaicinoids content than those of the others, even puree. Mutatoxanthin, naturally occurring pigment in red pepper, could only be detected in FD paprika. The highest RAE and SHU values, which were derived from the data of carotenoids and capsaicinoids, respectively, were also determined in NCD paprika.