Reducing Mechanical Damage in Bell Peppers by Applying Calcium Chloride

Green bell peppers (Capsicum annuum L., Solanaceae family) are vibrant in color, have a crisp texture, a unique flavor, and are rich in various nutrients such as sugars, vitamins, minerals, and other organic acids. They also contain capsaicin, an antioxidant compound associated with analgesia, antipyresis, cancer prevention, fat reduction, and weight loss. However, the thin skin, crispy flesh, and especially the hollow structure of green bell peppers make them susceptible to mechanical damage resulting from vibration, compression, and impact during post-harvest handling and transportation, leading to irreversible damage to the fruit's appearance and internal structure. Additionally, wounds increase the likelihood of microbial infection, causing decay and a loss of quality. Consequences of Mechanical InjuriesThe fruit undergoes a series of physiological and metabolic changes after a mechanical injury that accelerates senescence. These alterations include the disassembly of cell tissue, wound-induced ethylene production, higher respiration rates, faster oxidation, and increased catalase and polyphenol oxidase activities, leading to enzymatic browning. At the same time, mechanical injury promotes the generation of signal transduction molecules to activate the expression of defense genes in the fruit. Plant cells also synthesize secondary substances, including phenylpropanoids, lignin, phenols, flavonoids, terpenoids, alkaloids, tannins, long-chain fatty acids, and alcohols; these are concentrated around the wound and its surroundings and participate in the healing response. Furthermore, suberization or lignification of adjacent cell walls results in the formation of calluses that resist disease and pest invasion. These defensive reactions, on one hand, aid in healing the wounded parts and, on the other hand, induce systemic responses to further inhibit the local damage from spreading to distant, undamaged tissues. The Effects of CalciumCalcium ions (Ca2+) play multiple roles in plants, maintaining membrane integrity and cell wall strength. Ca2+ can reduce softening, browning, and the rate of fruit ripening and senescence. Calcium chloride (CaCl2), one of the most soluble forms of calcium salt, is classified as safe by the U.S. Food and Drug Administration (FDA). Post-harvest application of CaCl2 increases antioxidant capacity, delays softening, and reduces the occurrence of physiological disorders and diseases in fruits and vegetables. The Protective Effect of Calcium Chloride Treatment in Bell PeppersScientists evaluated the effects of CaCl2 treatment on mechanically damaged green bell peppers concerning physiology and potential regulatory mechanisms, using combined transcriptome, metabolome, and ATAC-seq (Assay for Transposase-Accessible Chromatin using sequencing) analyses. The results of these experiments showed the expression of key genes related to color change and fruit softening, active oxygen metabolism, and hormonal response, as well as changes in metabolite concentrations. It was also confirmed that CaCl2 treatment delays the ripening processes, maintains sensory and nutritional quality, and reduces the level of malondialdehyde (a marker of oxidative stress). Thus, the treatment with calcium chloride (CaCl2) is considered a safe, effective, and economical method to maintain fruit quality during post-harvest storage. *ATAC-seq is a technique used in molecular biology to evaluate chromatin accessibility throughout the genome. It identifies regions of accessible DNA by probing open chromatin with the transposase enzyme Tn5, which inserts sequencing adapters into specific genome regions. ReferencesMa, L.; Zheng, Y.; Sang, Z.; Ge, Y.; Bai, C.; Fu, A.; Wang, Q.; Watkins, C. B.; Zuo, J. (2023). Multi-omics analysis reveals the mechanism of calcium-reduced quality deterioration in mechanically injured green pepper fruit. Postharvest Biology and Technology, 204:112437. Tatara, M.; Ikeda, T.; Namekawa, S.; Maezawa, S. (2023). ATAC-Seq Analysis of Accessible Chromatin: From Experimental Steps to Data Analysis. Methods Mol Biol, 2577:65-81. Grandi, F.C.; Modi, H.; Kampman, L.; Corces, M. R. (2022). Chromatin accessibility profiling by ATAC-seq. Nat Protoc, 17(6):1518-1552. Imagehttps://www.autopista.es/planeta2030/descubre-propiedades-pimiento-verde_238708_102.html Accessed on 09/30/2023.