Controlled atmosphere storage alleviates internal browning in flat peach fruit by regulating energy and sugar metabolisms

Controlled atmosphere storage with high CO2 concentration extends storage life of fresh pomegranate fruit by regulating antioxidant capacity and respiration metabolism

BACKGROUND

Pomegranate is susceptible to low temperature. Controlled atmosphere (CA) with high CO2 concentration can prolong storage life by affecting fruit quality. Our study probed into the effect of CA storage on the pomegranate fruit quality as well as antioxidant attributes at 5 ℃ for 30 d, plus at 18 ℃ for 9 d in simulate marketing conditions. The atmosphere compositions of 7% O2 + 4% CO2 (CA1) and 2% O2 + 5% CO2 (CA2) were chosen, the regular air as control (CK).

RESULTS

In arils, the highest contents of total phenols, total flavonoids, and anthocyanins were all found after CA2 treatment, significantly higher 0.04 g kg-1 FW, 0.19 g kg-1 FW, and 0.70 g L-1 FW than those in CA1, respectively. Also, the highest enzyme activity of superoxide dismutase (SOD), glutathione reductase (GR), and ascorbate peroxidase (APX) in husks were presented in CA2, 36.30%, 36.05%, and 4.36%, higher than in CA1, respectively. Thus, CA2 treatment maintained better husk appearance due to significantly reducing chilling injury, malondialdehyde content, electrolyte leakage, and two enzymes activity, including peroxidase (POD) and/or polyphenol oxidase (PPO), meanwhile improving phenylalanine ammonia-lyase (PAL) enzyme activity. Also, CA2 effectively maintained the postharvest quality and reduced nutrition loss for fresh pomegranate fruit by reducing respiration rate, maintaining suitable energy charge, increasing ROS scavenging ability.

CONCLUSIONS

Totally, 2% O2 + 5% CO2 (relative higher CO2 concentration) could prolong the storage life of pomegranate fruit during cold storage by regulating antioxidant capacity and respiration metabolism, both higher nutrition value and better appearance.

Postharvest Flavor Quality Changes and Preservation Strategies for Peach Fruits: A Comprehensive Review

Peach (Prunus persica (L.) Batsch) is valued for its flavor, nutrition, and economic importance, yet as a climacteric fruit, it undergoes rapid postharvest senescence due to respiratory surges and ethylene production, leading to flavor loss and reduced marketability. Recent advances in postharvest physiology, including ethylene regulation, metabolic analysis, and advanced packaging, have improved preservation. Compared with traditional methods, emerging technologies, such as nanotechnology-based coatings and intelligent packaging systems, offer environmentally friendly and highly effective solutions but face high costs, technical barriers, and other constraints. This review examines changes in key flavor components-amino acids, phenolic compounds, sugars, organic acids, and volatile organic compounds (VOCs)-during ripening and senescence. It evaluates physical, chemical, and biotechnological preservation methods for maintaining quality. For instance, 1-MCP extends shelf life but may reduce aroma, underscoring the need for optimized protocols. Emerging trends, including biocontrol agents and smart packaging, provide a foundation for enhancing peach storage, transportation, and marketability.

Melatonin Rinsing Treatment Associated with Storage in a Controlled Atmosphere Improves the Antioxidant Capacity and Overall Quality of Lemons

Antioxidant capacity is one of the most important biological activities in fruits and vegetables and is closely related to human health. In this study, 'Eureka' lemons were used as experimental materials and stored at 7-8 °C MT (melatonin, 200 μmol, soaked for 15 min) and CA (controlled atmosphere, 2-3% O2 + 15-16% CO2) individually or in combination for 30 d. The changes in lemon fruits' basic physicochemical properties, enzyme activities, and antioxidant capacities were studied. Comparing the combined treatment to the control, the outcomes demonstrated a significant reduction in weight loss, firmness, stomatal opening, and inhibition of polyphenol oxidase (PPO) and peroxidase (POD) activities. Additionally, the combined treatment maintained high levels of titratable acidity (TA), vitamin C (VC), total phenolic content (TPC), and antioxidant capacity and preserved the lemon aroma. Meanwhile, the correlation between fruit color, aroma compounds, and antioxidant capacity was revealed, providing valuable insights into the postharvest preservation of lemons. In conclusion, the combined treatment (MT + CA) was effective in maintaining the quality and antioxidant capacity of lemons.

Mechanisms of Litchi Response to Postharvest Energy Deficiency via Energy and Sugar Metabolisms

In the post-harvest phase, fruit is inexorably subjected to extrinsic stressors that expedite energy expenditure and truncate the storage lifespan. The present study endeavors to elucidate the response strategies of litchi to the alterations of energy state caused by 2,4-Dinitrophenol (DNP) treatment through energy metabolism and sugar metabolism. It was observed that the DNP treatment reduced the energy state of the fruit, exacerbated membrane damage and triggered rapid browning in the pericarp after 24 h of storage. Furthermore, the expression of genes germane to energy metabolism (LcAtpB, LcAOX1, LcUCP1, LcAAC1, and, LcSnRK2) reached their peak within the initial 24 h of storage, accompanied by an elevation in the respiratory rate, which effectively suppressed the rise in browning index of litchi pericarp. The study also posits that, to cope with the decrease of energy levels and membrane damage, litchi may augment the concentrations of fructose, glucose, inositol, galactose, and sorbose, thus safeguarding the canonical metabolic functions of the fruit. Collectively, these findings suggest that litchi can modulate energy and sugar metabolism to cope with fruit senescence under conditions of energy deficiency. This study significantly advances the understanding of the physiological responses exhibited by litchi fruit to post-harvest external stressors.

Photocatalytic titanium dioxide reduces postharvest decay of nectarine fruit packaged in different materials through modulating central carbon and energy metabolisms

The capacity of titanium dioxide (TiO2) photocatalysis photocatalytic reactor to prevent and control pathogen infection in nectarine fruit packed in laminated nylon/LDPE, low density polyethylene and microperforated LDPE films was evaluated. Results showed that TiO2 combined with microperforated LDPE packaging (TPL) exhibited superior inhibition of microbial growth, reducing total viable counts by 4.18 log CFU g-1 and yeast and mold counts by 3.20 log CFU g-1, compared to microperforated LDPE packaging alone. TiO2 photocatalysis primed the defense systems in nectarine fruit packed in microperforated LDPE, improving the activity of defense-related enzymes. Metabolomics analysis indicated that l-aspartate, oxaloacetate, and succinic acid involved in central carbon metabolism including the glycolysis and tricarboxylic acid cycle pathways, were significantly upregulated by TPL. TiO2 increased the activity of energy metabolism-related enzymes, adenosine triphosphate, adenosine diphosphate, and energy charge levels to provide adequate energy, thus reducing fruit decay.

Synergistic Effects of 1-MCP Fumigation and ε-Poly-L-Lysine Treatments on Delaying Softening and Enhancing Disease Resistance of Flat Peach Fruit

Flat peach, a predominant fruit consumed in China, is highly susceptible to softening and perishable. The impact of 1-methylcycloproene (1-MCP) fumigation combined with ε-poly-L-lysine (ε-PL) on softening and postharvest reactive oxygen species (ROS) and phenylpropanoid pathway metabolisms in peaches and its relationship to disease resistance were investigated. Findings revealed that a combination of 1 µL L-1 1-MCP and 300 mg L-1 ε-PL effectively suppressed the activity of cell-wall-degrading enzymes and the disassembly of cell wall structure, thus maintaining higher firmness and lower decay incidence. Compared to the control group, the synergistic approach bolstered enzymatic responses linked to disease resistance and ROS-scavenge system, consistently preserving total phenolics, flavonoids, ascorbic acid, and glutathione levels. Concurrently, the accumulation of hydrogen peroxide and malondialdehyde was significantly diminished post-treatment. These results show that there is good synergistic effect between 1-MCP and ε-PL, which could effectively maintain the quality of flat peach fruit by modulating cell wall metabolism and enhancing the resistance.

Transcriptome Co-Expression Network Analysis of Peach Fruit with Different Sugar Concentrations Reveals Key Regulators in Sugar Metabolism Involved in Cold Tolerance

Peach fruits are known to be highly susceptible to chilling injury (CI) during low-temperature storage, which has been linked to the level of sugar concentration in the fruit. In order to better understand the relationship between sugar metabolism and CI, we conducted a study examining the concentration of sucrose, fructose, and glucose in peach fruit with different sugar concentrations and examined their relationship with CI. Through transcriptome sequencing, we screened the functional genes and transcription factors (TFs) involved in the sugar metabolism pathway that may cause CI in peach fruit. Our results identified five key functional genes (PpSS, PpINV, PpMGAM, PpFRK, and PpHXK) and eight TFs (PpMYB1/3, PpMYB-related1, PpWRKY4, PpbZIP1/2/3, and PpbHLH2) that are associated with sugar metabolism and CI development. The analysis of co-expression network mapping and binding site prediction identified the most likely associations between these TFs and functional genes. This study provides insights into the metabolic and molecular mechanisms regulating sugar changes in peach fruit with different sugar concentrations and presents potential targets for breeding high-sugar and cold-tolerant peach varieties.