Extending Shelf Life and Maintaining Quality of Tomato Fruit by Calcium Chloride, Hydrogen Peroxide, Chitosan, and Ozonated Water

Hydrogen peroxide and salt stress in radish: effects on growth, physiology, and root quality

Hydrogen peroxide (H2O2) plays a central role in responses to salt stress, a major abiotic stress that impacts crop yield worldwide. Despite the evidence that H2O2 mitigates salt stress and improves post-harvest quality on several species, its effects on radish were not investigated so far. Thus, the objective of this study was to evaluate the exogenous application of H2O2 on salt stress mitigation of radish growth, physiology, and post-harvest quality. For this, radish plants were grown in pots for 30 days, being watered with non-saline (0.31 dS m-1) or saline water (120 mM NaCl, 12.25 dS m-1). Plants were leaf-sprayed weekly with water (control - 0 µM H2O2) or H2O2 (150 or 1500 µM) solutions. The experimental design was completely randomized in a 3 × 2 factorial scheme (H2O2 treatments × salt stress conditions). The growth, physiology (gas exchanges, photochemical efficiency, relative water content, electrolyte leakage, and the contents of chlorophylls and carotenoids), and post-harvest attributes of globular roots (color, anthocyanins, vitamin C, phenolic compounds, and soluble solids) were determined. Salt stress decreased gas exchanges and increased electrolyte leakage, which resulted in stunted radish growth, and increased the contents of antioxidants, such as anthocyanins, soluble solids, and vitamin C, improving globular root quality. Conversely, H2O2 did not mitigate salt stress effects on radish growth, photosynthetic capacity, and oxidative damages. Although H2O2 increased vitamin C under non-stressed condition, it was decreased under salt stress. Thus, we conclude that H2O2 did not mitigate salt stress on radish growth and quality.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-024-01476-z.

Antimicrobial Activity of Hydrogen Peroxide for Application in Food Safety and COVID-19 Mitigation: An Updated Review

Hydrogen peroxide (H2O2) is a well-known agent with a broad-spectrum antimicrobial activity against pathogenic bacteria, fungi, and viruses. It is a colorless liquid and commercially available in aqueous solution over a wide concentration range. It has been extensively used in the food industry by virtue of its strong oxidizing property and its ability to cause cellular oxidative damage in microbial cells. This review comprehensively documents recent research on the antimicrobial activity of H2O2 against organisms of concern for the food industry, as well as its effect against SARS-CoV-2 responsible for the COVID-19 pandemic. In addition, factors affecting the antimicrobial effectiveness of H2O2, different applications of H2O2 as a sanitizer or disinfectant in the food industry as well as safety concerns associated with H2O2 are discussed. Finally, recent efforts in enhancing the antimicrobial efficacy of H2O2 are also outlined.

Integrative analysis of the methylome and transcriptome of tomato fruit (Solanum lycopersicum L.) induced by postharvest handling

Tomato fruit ripening is triggered by the demethylation of key genes, which alters their transcriptional levels thereby initiating and propagating a cascade of physiological events. What is unknown is how these processes are altered when fruit are ripened using postharvest practices to extend shelf-life, as these practices often reduce fruit quality. To address this, postharvest handling-induced changes in the fruit DNA methylome and transcriptome, and how they correlate with ripening speed, and ripening indicators such as ethylene, abscisic acid, and carotenoids, were assessed. This study comprehensively connected changes in physiological events with dynamic molecular changes. Ripening fruit that reached 'Turning' (T) after dark storage at 20°C, 12.5°C, or 5°C chilling (followed by 20°C rewarming) were compared to fresh-harvest fruit 'FHT'. Fruit stored at 12.5°C had the biggest epigenetic marks and alterations in gene expression, exceeding changes induced by postharvest chilling. Fruit physiological and chronological age were uncoupled at 12.5°C, as the time-to-ripening was the longest. Fruit ripening to Turning at 12.5°C was not climacteric; there was no respiratory or ethylene burst, rather, fruit were high in abscisic acid. Clear differentiation between postharvest-ripened and 'FHT' was evident in the methylome and transcriptome. Higher expression of photosynthetic genes and chlorophyll levels in 'FHT' fruit pointed to light as influencing the molecular changes in fruit ripening. Finally, correlative analyses of the -omics data putatively identified genes regulated by DNA methylation. Collectively, these data improve our interpretation of how tomato fruit ripening patterns are altered by postharvest practices, and long-term are expected to help improve fruit quality.

Advancements in coating technologies: Unveiling the potential of chitosan for the preservation of fruits and vegetables

Post-harvest losses of fruits and vegetables pose a significant challenge to the agriculture industry worldwide. To address this issue, researchers have turned to natural and eco-friendly solutions such as chitosan coatings. Chitosan, a biopolymer derived from chitin, has gained considerable attention due to its unique properties such as non-toxicity, biodegradability, biocompatibility and potential applications in post-harvest preservation. This review article provides an in-depth analysis of the current state of research on chitosan coatings for the preservation of fruits and vegetables. Moreover, it highlights the advantages of using chitosan coatings, including its antimicrobial, antifungal, and antioxidant properties, as well as its ability to enhance shelf-life and maintain the quality attributes of fresh product. Furthermore, the review discusses the mechanisms by which chitosan interacts with fruits and vegetables, elucidating its antimicrobial activity, modified gas permeability, enhanced physical barrier and induction of host defense responses. It also examines the factors influencing the effectiveness of chitosan coatings, such as concentration, molecular weight, deacetylation degree, pH, temperature, and application methods.

Development of chitin nanofiber coatings for prolonging shelf life and inhibiting bacterial growth on fresh cucumbers

The widespread usage of petroleum-based polymers as single-use packaging has had harmful effects on the environment. Herein, we developed sustainable chitin nanofiber (ChNF) coatings that prolong the shelf life of fresh cucumbers and delay the growth of pathogenic bacteria on their surfaces. ChNFs with varying degrees of acetylation were successfully prepared via deacetylation using NaOH with treatment times of 0-480 min and defibrillated using mechanical blending. With longer deacetylation reaction times, more acetamido groups (-NHCOCH3) in chitin molecules were converted to amino groups (-NH2), which imparted antibacterial properties to the ChNFs. The ChNF morphologies were affected by deacetylation reaction time. ChNFs deacetylated for 240 min had an average width of 9.0 nm and lengths of up to several μm, whereas rod-like structured ChNFs with a mean width of 7.3 nm and an average length of 222.3 nm were obtained with the reaction time of 480 min. Furthermore, we demonstrated a standalone ChNF coating to extend the shelf life of cucumbers. In comparison to the rod-like structured ChNFs, the 120 and 240-min deacetylated ChNFs exhibited a fibril-like structure, which considerably retarded the moisture loss of cucumbers and the growth rate of bacteria on their outer surfaces during storage. Cucumbers coated with these 120 and 240-min deacetylated ChNFs demonstrated a lower weight loss rate of ⁓ 3.9% day-1 compared to the uncoated cucumbers, which exhibited a weight loss rate of 4.6% day-1. This protective effect provided by these renewable ChNFs holds promising potential to reduce food waste and the use of petroleum-based packaging materials.

Postharvest Calcium Chloride Treatment Strengthens Cell Wall Structure to Maintain Litchi Fruit Quality

Litchi (Litchi chinensis Sonn.) fruit deterioration occurs rapidly after harvest and is characterized by pericarp browning, pulp softening, and decay. In this study, we found that calcium chloride (CaCl₂) treatment (5 g L^-1 CaCl₂ solution vacuum infiltration for 5 min) affected the cell wall component contents and cell wall-degrading enzyme activities of litchi fruit during storage at room temperature. CaCl₂ treatment significantly increased the contents of Ca²⁺ and cellulose, while it decreased the water-soluble pectin content, and the activities of polygalacturonase, β-galactosidase, and cellulase in the litchi pericarp. Meanwhile, the treatment resulted in significantly increased contents of Ca²⁺, water-soluble pectin, ionic-soluble pectin, covalent-soluble pectin and hemicellulose, and upregulated activities of pectinesterase and β-galactosidase, while significantly decreasing the activities of polygalacturonase and cellulase in litchi pulp. The above results indicate that CaCl₂ treatment strengthened the cell wall structure of litchi fruit. More importantly, the enzymatic browning of the pericarp, softening of the pulp, and disease incidence were delayed. The treatment had a more pronounced effect on the pericarp than on the pulp. We consider CaCl₂ treatment to be a safe and effective treatment for maintaining the postharvest quality of litchi fruit.

Impact of Isonicotinic Acid Blending in Chitosan/Polyvinyl Alcohol on Ripening-Dependent Changes of Green Stage Tomato

The effect of isonicotinic acid (INA) in a chitosan (CS)/polyvinyl alcohol (PVA) blend on ripening-dependent changes of preserved green tomatoes (Solanum lycopersicum L.) was examined at room temperature. The results showed that CS/PVA/INA 0.5 mM and CS/PVA/INA 1.0 mM formulations retarded firmness loss and delayed the pigmentation parameters i.e., lycopene (LYP), total carotenes (TCs), and titratable acidity (TA). The CS/PVA/INA 0.5 mM and CS/PVA/INA 1.0 mM formulations were able to delay the increase in malondialdehyde (MDA) and total polyphenol (TP) contents. Furthermore, the peroxidase (POD), polyphenoloxidase (PPO), and phenylalanine ammonia-lyase (PAL) activities of tomatoes coated with CS/PVA/INA 0.5 mM and CS/PVA/INA 1.0 mM formulations were lower than those in other treatments. Meanwhile, the CS/PVA blend had the highest TP content, as well as the highest PPO and PAL activities, at the late stage of maturation. The UV analysis showed that the CS/PVA/INA blend film is a promising UV-protective food packaging material. The pure CS, PVA, and INA formulations, as well as the CS/PVA, CS/PVA/INA 0.5 mM, and CS/PVA/INA 1.0 mM formulations, were characterized by infrared (FTIR). The three polymer formulations showed strong antifungal activity against Alternaria alternata and Botrytis cinerea.

Chitosan nano-biopolymer/Citrus paradisi peel oil delivery system enhanced shelf-life and postharvest quality of cherry tomato

Grapefruit peel essential oil (CpEO) was loaded on chitosan (Cs) nano-biopolymer by ionic gelation method and its effect on physicochemical properties of cherry tomatoes was evaluated during 18 days of storage at 10 °C. The highest loading capacity and encapsulation efficiency were obtained from the weight ratio of 1:0.25 Cs to oil. TEM, DLS and FTIR were used to characterize the nanoparticles. The release of the oil from the nanoparticles followed the Fickian diffusion model. CpEO-CsNPs-CO and CpEO-CsNPs-RE treatments reduced ethylene production and respiration rate and indicated a significant and promising effect on increasing the level of antioxidant enzymes (CAT and POD), slowing down the loss of ascorbic acid and total phenolic content and consequently, maintaining antioxidant capacity. These treatments prevented a rapid decline in TSS and TA and an increase in lycopene and MDA level, and maintained the firmness, weight, and color of the fruits throughout storage period.

Bio-Stimulants Extend Shelf Life and Maintain Quality of Okra Pods

Okra (Abelmoschus esculentus L.), a tropical annual crop, is a highly perishable vegetable. Okra pods deteriorate rapidly after harvesting. The pods undergo physical and physiological changes that diminish storability and quality. The purpose of this study was to investigate the effect of bio-stimulants on the storability and quality of okra pods stored at 4 °C and 25 °C for 12 days. Dipping okra pods for 5 min in a solution of 0.5% ascorbic acid, citric acid, or salicylic acid pre-storage significantly extended the shelf life and preserved the quality of the pods compared to the control condition at 4 °C and 25 °C. Citric acid and ascorbic acid were the most effective in preserving most traits. Citric acid reduced the loss in weight, firmness, appearance, and prevented decay at 4 °C and 25 °C. Ascorbic acid decreased the loss of moisture and the degradation of carbohydrates, vitamin C and lycopene at 4 °C and 25 °C. Salicylic acid decreased the degradation of protein at 25 °C. The low temperature was highly effective in decreasing the loss or degradation of most of the studied traits. Taken together, bio-stimulants and storing at 4 °C played a prominent role in extending the shelf life and preserving the quality of okra pods.

Exogenous Proline, Methionine, and Melatonin Stimulate Growth, Quality, and Drought Tolerance in Cauliflower Plants

The impact of proline, methionine, and melatonin on cauliflower plants under drought stress is still unclear in the available publications. So, this research aims to study these biochemical compounds’ effects on cauliflower plants grown under well-irrigated and drought-stressed conditions. The obtained results showed that under drought-stressed conditions, foliar application of proline, methionine, and melatonin significantly (p ≤ 0.05) enhanced leaf area, leaf chlorophyll content, leaf relative water content (RWC), vitamin C, proline, total soluble sugar, reducing sugar, and non-reducing sugar compared to the untreated plants. These treatments also significantly increased curd height, curd diameter, curd freshness, and dry matter compared to untreated plants. Conversely, the phenolic-related enzymes including polyphenol oxidase (PPO), peroxidase (POD), and phenylalanine ammonia-lyase (PAL) were significantly reduced compared to the untreated plants. A similar trend was observed in glucosinolates, abscisic acid (ABA), malondialdehyde (MDA), and total phenols. Eventually, it can be concluded that the foliar application of proline, methionine, and melatonin can be considered a proper strategy for enhancing the growth performance and productivity of cauliflower grown under drought-stressed conditions.

Foliar application of salicylic acid and calcium chloride delays the loss of chlorophyll and preserves the quality of broccoli during storage

Consumer awareness of broccoli's unusual color, rich flavor, and concentration of desired phytochemicals has led to a steady increase in consumption in recent years. However, its short shelf-life, which is linked with quick discoloration and degeneration after harvest, limits industrial production and marketing. The effect of pre-harvest salicylic acid (SA) and calcium chloride (Ca) and their combination on the post-harvest quality of broccoli during storage (5 ± 1°C) was explored in this study. The foliar spray treatments reduced weight loss of broccoli head during storage. At the end of storage, Ca (2%) alone and in combination with SA (0.01%) significantly maintained the chlorophyll concentration rather than control. The total phenols, flavonoid, and antioxidant capacity of the Ca (2%) + SA (0.01%) treated samples was significantly greater than the control. SA (0.01%) alone or in conjunction with Ca (2%), showed higher catalase (CAT) activity; however, Ca (1%), alone or in combination with SA (0.01%), showed higher peroxidase (POD) activity. Generally, the marketability of the treated broccoli was significantly greater than the control at the end of storage. Based on these findings, we believe Ca (2%) + SA (0.01%) improves the antioxidant system, delays chlorophyll degradation, and extends the shelf life of broccoli heads stored at 5 ± 1°C. It is proposed that the green color, marketability, and nutrient content of broccoli during postharvest handling and storage can be retained longer by foliar application of this treatment. PRACTICAL APPLICATIONS: Broccoli (Brassica oleracea L. Italaia) is a widely-consumed floral green vegetable due to its high content of nutrients and bioactive compounds. However, after harvest, florets rapidly senesce and suffer from yellowing which affects the quality of broccoli. The senescence of post-harvest broccoli is characterized by fresh weight loss, chlorophyll degradation, and a significant reduction in nutritional content. Therefore, preventing the decline in the quality of harvested broccoli is essential to maintain its economic and nutritional value. The results of this study showed that pre-harvest foliar application of Ca (2%) + SA (0.01%) with delayed weight loss, chlorophyll degradation, preservation of antioxidant compounds, and increased enzyme activity has a positive effect in maintaining broccoli heads quality during cold storage.

Unravelling the Role of Piriformospora indica in Combating Water Deficiency by Modulating Physiological Performance and Chlorophyll Metabolism-Related Genes in Cucumis sativus

Water stress is the most critical aspect restricting the development of agriculture in regions with scarce water resources, which requires enhancing irrigation water-saving strategies. The current work discusses the potential application of the plant-strengthening root endophyte Piriformospora indica against moderate (25% less irrigation water) and severe (50% less irrigation water) water stress in comparison to the optimum irrigation conditions of greenhouse cucumbers. P. indica improved growth, nutrient content, and photosynthesis apparatus under normal or water-stress conditions. On the other hand, moderate and severe water stress reduced yield up to 47% and 83%, respectively, in non-colonized cucumber plants, while up to 28 and 78%, respectively, in P. indica-colonized plants. In terms of water-use efficiency (WUE), P. indica improved the WUE of colonized cucumber plants grown under moderate (26 L/kg) or severe stress (73 L/kg) by supporting colonized plants in producing higher yield per unit volume of water consumed by the crop in comparison to non-colonized plants under the same level of moderate (43 L/kg) or severe (81 L/kg) water stress. Furthermore, P. indica increased the indole-3-acetic acid (IAA) content, activity levels of catalase (CAT) and peroxidase (POD) with an apparent clear reduction in the abscisic acid (ABA), ethylene, malondialdehyde (MDA), proline contents and stomatal closure compared to non-stressed plants under both water-stress levels. In addition, chlorophyll a, b, a + b contents were increased in the leaves of the colonized plants under water-stress conditions. This improvement in chlorophyll content could be correlated with a significant increment in the transcripts of chlorophyll biosynthesis genes (protochlorophyllide oxidoreductase [POR], chlorophyll a oxygenase [CAO]) and a reduction in the chlorophyll degradation genes (PPH, pheophorbide a oxygenase [PAO], and red chlorophyll catabolite reductase [RCCR]). In conclusion, P. indica has the potential to enhance the cucumber yield grown under moderate water stress rather than severe water stress by improving WUE and altering the activity levels of antioxidant enzymes and chlorophyll metabolism-related genes.