UV-C Treatment Maintains the Sensory Quality, Antioxidant Activity and Flavor of Pepino Fruit during Postharvest Storage

The effect of ultraviolet-C on the senescence of bitter gourd fruit and the key factors analyzed by transcriptomic and metabolomic analyses

Bitter gourd (Momordica charantia L.) is a tropical and subtropical vegetable that is popular for its rich nutritional content. However, its immature fruit has a short shelf life and spoils easily. This study assessed the effects of ultraviolet-C (UV-C) irradiation on the storage and quality of postharvest bitter gourd fruit. Exposure for 40 s maintained fruit firmness, delayed senescence, increased the antioxidant capacity and minimized damage by reactive oxygen species. Transcriptomic and metabolomic analyses identified 12,733 differentially expressed genes and 282 metabolites during storage. The downregulation of genes for ethylene synthesis and cell wall degradation delayed ripening and senescence, while the upregulation of phenylpropanoid biosynthetic genes enhanced its antioxidant properties. Key transcription factors, such as MYB, bHLH, and bZIP, were implicated in the delayed senescence treatment. This research elucidates the mechanisms of prevention of bitter gourd with UV-C and offers insights into the genetic and metabolite candidates for enhanced strategies of postharvest preservation.

Preparation of bioactive film for regulating chlorine dioxide release based on the hygroscopic properties of chitosan and its application in broccoli preservation

An active packaging film was developed by integrating sodium chlorite (SC) and citric acid (CA) into a Poly(lactic acid)/Poly(butylene adipate-co-terephthalate) (PLA/PBAT) matrix, enabling the controlled release of chlorine dioxide (ClO2) gas. The release of ClO2 was further regulated by introducing chitosan (CS) into the film, leveraging its hygroscopic properties. The results showed that when the addition amount of CS was 4 wt%, the water vapor transmission rate increased by 41.41 %, the water contact angle decreased by 24.4 %, the ClO2 release increased by 2.81 times after 72 h, and the scavenging rate of DPPH free radicals reached 96.26 % after 96 h. When the film was applied to broccoli packaging, it successfully protected the appearance and color of broccoli, effectively inhibited the activity of oxidase and reduced the reduction of active substances, and maintained the marketable quality for up to 8 days. Therefore, this ClO2-releasing active film has application potential in the color protection and preservation of broccoli and other green vegetables.

The mechanism by which oriented polypropylene packaging alleviates postharvest 'Black Spot' in radish root (Raphanus sativus)

INTRODUCTION

The postharvest physiological disorder known as 'black spot' in radish roots (Raphanus sativus) poses a significant challenge to quality maintenance during storage, particularly under summer conditions. The cause of this disorder, however, is poorly understood.

OBJECTIVES

Characterize the underlying causes of 'black spot' disorder in radish roots and identify strategies to delay its onset.

METHODS

Radish roots were placed in either polyvinyl chloride (PVC) or oriented polypropylene (OPP) packaging and stored for 4 days at 30 °C. Appearance and physiological parameters were assessed and transcriptomic and metabolomic analyses were conducted to identify the key molecular and biochemical factors contributing to the disorder and strategies for delaying its onset and development.

RESULTS

OPP packaging effectively delayed the onset of 'black spot' in radishes, potentially due to changes in phenolic and lipid metabolism. Regarding phenolic metabolism, POD and PPO activity decreased, RsCCR and RsPOD expression was downregulated, genes involved in phenols and flavonoids synthesis were upregulated and their content increased, preventing the oxidative browning of phenols and generally enhancing stress tolerance. Regarding lipid metabolism, the level of alpha-linolenic acid increased, and genes regulating cutin and wax synthesis were upregulated. Notably, high flavonoid and low ROS levels collectively inhibited RsPLA2G expression, which reduced the production of arachidonic acid, pro-inflammatory compounds (LTA4 and PGG2), and ROS, alleviating the inflammatory response and oxidative stress in radish epidermal tissues.

CONCLUSION

PVC packaging enhanced the postharvest onset of 'black spot' in radishes, while OPP packaging delayed both its onset and development. Our study provides insights into the response of radishes to different packaging materials during storage, and the causes and host responses that either enhance or delay 'black spot' disorder onset. Further studies will be conducted to confirm the molecular and biochemical processes responsible for the onset and development of 'black spot' in radishes.

Review of fruits flavor deterioration in postharvest storage: Odorants, formation mechanism and quality control

Fruits flavor deterioration is extremely likely to occur during post-harvest storage, which not only damages quality but also seriously affects its market value. This work focuses on the study of fruits deterioration odorants during storage by describing their chemical compositions (i.e., alcohols, aldehydes, acids, and sulfur-containing compounds). Besides, the specific flavor deterioration mechanisms (i.e., fermentation metabolism, lipid oxidation, and amino acid degradation) inducing by factors (temperature, oxygen, microorganisms, ethylene) are summarized. Moreover, quality control strategies to mitigate fruits flavor deterioration by physical (temperature control, hypobaric treatment, UV-C, CA) and chemical (1-MCP, MT, NO, MeJA) techniques are also proposed. This review will provide useful references for fruits flavor control technologies development.

Post-harvest ultraviolet irradiation induces changes in physical-chemical properties and levels of polycyclic aromatic hydrocarbons and gene expression in mulberry fruit

BACKGROUND

Earlier studies reported that post-harvest ultraviolet (UV) irradiation could increase the health-promoting compounds in fruit but the effects of UV irradiation on the reduction of the polycyclic aromatic hydrocarbon (PAH) content in mulberries remain less known. Black mulberry fruit were exposed to two UV illumination dosages (3.5 and 7 kJ m-2 ) and were stored for 4, 8, and 12 days.

RESULTS

Mulberries treated in this way displayed higher antioxidant enzyme activity and phenolic compound content in comparison with a control condition. The transcription factors (TFs) MdoMYB121, MdoMYB155, MdbZIP2, and MdbZIP48 were strongly expressed in two UV illumination dosages (about 45-95% higher than the control). The fluorine (Flu) and naphthalene (Nap) content in treated fruit decreased by 21-85% in comparison with the control condition.

CONCLUSION

The findings of this study indicate that UV irradiation can be considered as a promising technique to remove some PAHs in black mulberries, to increase their health-promoting potential, and indirectly to improve their aesthetic quality due to the resulting desirable color parameters. © 2023 Society of Chemical Industry.

Biochemical dynamics during postharvest: Highlighting the interplay of stress during storage and maturation of fresh produce

The lifecycle of fresh produce involves a sequence of biochemical events during their ontology, and these events are particularly significant for climacteric fruits. A high demand during ripening is observed in these plant products, which is reflected in a high rate of respiration and ethylene production. Increased respiratory demand triggers the activation of secondary pathways such as alternate oxidase, which do not experience critical increases in energy consumption in non-climacteric fruit. In addition, biochemical events produced by external factors lead to compensatory responses in fresh produce to counteract the oxidative stress caused by the former. The dynamics of these responses are accompanied by signaling, where reactive oxygen species play a pivotal role in fresh product cell perception. This review aims to describe the protection mechanisms of fresh produce against environmental challenges and how controlled doses of abiotic stressors can be used to improve quality and prolong their shelf-life through the interaction of stress and defense mechanisms.

Post-Harvest Application of Nanoparticles of Titanium Dioxide (NPs-TiO2) and Ethylene to Improve the Coloration of Detached Apple Fruit

In this study, we analyzed the effects of treatments with titanium dioxide nanoparticles (NPs-TiO2) and ethylene on anthocyanin biosynthesis and reactive oxygen species (ROS) metabolism during light exposure in ripe 'red delicious' apples. Both treatments led to improved anthocyanins biosynthesis in detached mature apples, while the NPs-TiO2 had less impact on the fruit firmness, TSS, TA, and TSS/TA ratio. Furthermore, the effects of both treatments on the expression of anthocyanin-related enzymes and transcription factors in the apple peel were evaluated at the gene level. The differentially expressed genes induced by the two treatments were highly enriched in the photosynthesis and flavonoid biosynthesis pathways. The expression of structural genes involved in anthocyanin biosynthesis and ethylene biosynthesis was more significantly upregulated in the ethylene treatment group than in the NPs-TiO2 treatment group, and the opposite pattern was observed for the expression of genes encoding transcription factors involved in plant photomorphogenesis pathways. In addition, the ROS levels and antioxidant capacity were higher and the membrane lipid peroxidation level was lower in fruit in the NPs-TiO2 treatment group than in the ethylene treatment group. The results of this study reveal differences in the coloration mechanisms induced by NPs-TiO2 and ethylene in apples, providing new insights into improving the color and quality of fruits.

Determination of antioxidant capacity, citric acid, phenolic compounds, physicochemical and sensory properties of Pepino marmalade yogurts enriched with erythritol and amaranth flour at different concentrations

This work aimed to evaluate the feasibility of fortifying Pepino marmalade containing erythritol and amaranth flour (1, 2, and 3%) as the source of antioxidants, dietary fiber, and polyphenols in yogurt for increasing nutritional value and improving storability. Both Pepino marmalade and amaranth flour increased the phenolic content, citric acid value, viscosity, and WHC of the yogurt samples. The diphenyl-1 picrylhydrazyl scavenging activity (DPPH), radical cation (ABTS^*+) scavenging assay, oxygen radical absorption capacity (ORAC), and ferric-reducing antioxidant capacity (FRAP) were found to be in the range of 4.5-46.6%, 166.2-1022 µg AAE/g, 2.61-4.49 µmol Trolox/g, and 4.9-23.88 µmol Fe²⁺/g respectively. As the concentration of marmalade and amaranth flour increased, the samples showed higher b* and lower a* and L* values. In addition, the panelists stated that they enjoyed the yogurt samples with Pepino marmalade and amaranth flour.

An Exploration of Pepino (Solanum muricatum) Flavor Compounds Using Machine Learning Combined with Metabolomics and Sensory Evaluation

Flavor is one of the most important characteristics that directly determines the popularity of a food. Moreover, the flavor of fruits is determined by the interaction of multiple metabolic components. Pepino, an emerging horticultural crop, is popular for its unique melon-like flavor. We analyzed metabolomics data from three different pepino growing regions in Haidong, Wuwei, and Jiuquan and counted the status of sweetness, acidity, flavor, and overall liking ratings of pepino fruit in these three regions by sensory panels. The metabolomics and flavor ratings were also integrated and analyzed using statistical and machine learning models, which in turn predicted the sensory panel ratings of consumers based on the chemical composition of the fruit. The results showed that pepino fruit produced in the Jiuquan region received the highest ratings in sweetness, flavor intensity, and liking, and the results with the highest contribution based on sensory evaluation showed that nucleotides and derivatives, phenolic acids, amino acids and derivatives, saccharides, and alcohols were rated in sweetness (74.40%), acidity (51.57%), flavor (56.41%), and likability (33.73%) dominated. We employed 14 machine learning strategies trained on the discovery samples to accurately predict the outcome of sweetness, sourness, flavor, and liking in the replication samples. The Radial Sigma SVM model predicted with better accuracy than the other machine learning models. Then we used the machine learning models to determine which metabolites influenced both pepino flavor and consumer preference. A total of 27 metabolites most important for pepino flavor attributes to distinguish pepino originating from three regions were screened. Substances such as N-acetylhistamine, arginine, and caffeic acid can enhance pepino‘s flavor intensity, and metabolites such as glycerol 3-phosphate, aconitic acid, and sucrose all acted as important variables in explaining the liking preference. While glycolic acid and orthophosphate inhibit sweetness and enhance sourness, sucrose has the opposite effect. Machine learning can identify the types of metabolites that influence fruit flavor by linking metabolomics of fruit with sensory evaluation among consumers, which conduces breeders to incorporate fruit flavor as a trait earlier in the breeding process, making it possible to select and release fruit with more flavor.