Exogenous Application of Glycine Betaine Maintains Bioactive Compounds, Antioxidant Activity, and Physicochemical Attributes of Blood Orange Fruit During Prolonged Cold Storage

The Simultaneous Use of 1-Methylcyclopropene and Methyl Jasmonate Vapor as an Innovative Strategy for Reducing Chilling Injury and Maintaining Pomegranate Fruit Quality at Suboptimal Temperatures

Spain is one of the main contributors to global pomegranate production. Pomegranate presents a challenge for preservation at suboptimal temperatures. Preserving this fruit for an extended period is challenging due to its susceptibility to chilling injury (CI). For this reason, we have examined different postharvest treatments to extend the pomegranate shelf life and their potential impact on reducing CI. For this reason, two postharvest treatments have been applied: 1-Methylcyclopropene (1000 nL L-1 1-MCP) and methyl jasmonate vapors (0.01 mM MeJA), a natural elicitor found in many plant organs that induces a wide range of physiological processes, including the activation of defense mechanisms against stress. Following the application of these treatments and subsequent fruit storage at 2 °C for 90 days, maintenance of firmness and membrane integrity was observed. Additionally, a positive synergic effect was observed in these quality traits when combining both substances (1-MCP + MeJA), especially with regard to delaying weight loss, the external color evolution, and total polyphenol accumulation. On the other hand, MeJA treatment alone or in combination with 1-MCP also increased the anthocyanin content in arils, thereby enhancing the fruit quality. In general, the best results were observed when these two different technologies were applied as a combined treatment, especially in terms of maintaining quality traits such as fruit firmness and total acidity and reducing weight loss and CI. This is the first time that these two substances have been tested together in any fruit species, and their simultaneous application in the same container represents an innovative approach that could be an interesting tool for commercial purposes.

Anthocyanin in blood oranges: a review on postharvest approaches for its enhancement and preservation

Anthocyanin concentration is considered an important fruit quality index of blood oranges and has gained popularity among consumers due to its antioxidant capacity, therapeutic properties, and prevention of some human diseases. Anthocyanin biosynthesis occurs in the cytoplasmic face of the endoplasmic reticulum by multi-enzymes complexes through the flavonoid pathway. Polyphenoloxidase (PPO) and β-glucosidase (anthocyanase) are the enzymes responsible for anthocyanin degradation. Blood oranges are cold-dependent for anthocyanin biosynthesis and accumulation, and thus, the low temperature of storage can enhance anthocyanin concentration and improve internal fruit quality. In addition, anthocyanin accumulation can be accelerated by postharvest technologies, either physical treatments or chemical elicitors. However, low temperatures can induce chilling injury (CI) incidence in blood oranges. Postharvest chemical elicitors treatments can enhance anthocyanin accumulation and prevent CI. This review provides the most updated information about postharvest tools modulating the anthocyanin content, and the role of enhancing and preserving pigmentation to produce blood orange with the highest quality standards.

Ultrasound Treatment Improves Fruit Quality of Postharvest Blood Oranges (Citrus sinensis L. Osbeck): Anthocyanin Enrichment and Its Biosynthesis

This study was to investigate the effects of different nonthermal treatments on quality attributes, anthocyanin profiles, and gene expressions related to anthocyanin biosynthesis during low-temperature storage, including pulsed light (PL), magnetic energy (ME), and ultrasound (US). Among these treatments, 1 min US treatment was the most effective method for improving fruit quality and increasing total anthocyanin contents (by 29.89 ± 3.32%) as well as individual anthocyanins during low-temperature storage of 28 days. This treatment resulted in high color intensity, intact cellular architectures, and positive sensory evaluation. In contrast, PL and ME treatments displayed negative effects on quality improvement, leading to the destruction of cell architectures and inhibiting anthocyanin levels. Furthermore, qPCR analysis revealed that the structural genes (C4H, CHS1, CHS2, CHI, F3H, ANS, and GST) related to anthocyanin biosynthesis and transport were the target genes and upregulated in response to the cavitation effect of US treatment.

Effects of Exogenous Application of Glycine Betaine Treatment on 'Huangguoggan' Fruit during Postharvest Storage

Loss of quality in citrus fruit is a common occurrence during postharvest storage due to oxidative stress and energy consumption. In recent years, glycine betaine (GB) has been widely applied to postharvest horticulture fruit. This study aimed to investigate the effect of GB treatment (10 mM and 20 mM) on the quality and antioxidant activity of 'Huangguogan' fruit during postharvest storage at room temperature. Our results indicated that both 10 mM and 20 mM treatments effectively reduced weight and firmness losses and maintained total soluble solid (TSS), titratable acidity (TA), and ascorbic acid contents. Additionally, GB treatment significantly increased the activity of antioxidant enzymes, maintained higher levels of total phenols and total flavonoids, and led to slower accumulation of H2O2. A transcriptome analysis conducted at 28 days after treatment (DAT)identified 391 differentially expressed genes (DEGs) between 20 mM GB (GB-2) and the control (CK) group. These DEGs were enriched in various pathways, particularly related to oxygen oxidoreductase, peroxidase activity, and flavonoid biosynthesis. Overall, the application of GB proved beneficial in enhancing the storability and extending the shelf life of 'Huangguogan' fruit.

Glycine betaine inhibits postharvest softening and quality decline of winter jujube fruit by regulating energy and antioxidant metabolism

Winter jujube fruit easily softens after harvest. To investigate the effects of glycine betaine (N,N,N-trimethylglycine; GB) treatment on the quality of postharvest jujubes, fresh winter jujubes (Zizyphus jujuba Mill. cv. Dongzao) were immersed in 20 mmol·L^-1 GB for 20 min. The results showed that GB application can effectively maintain cell wall component content by restraining gene expression and enzyme activities, including PG, CX, PME and β-Glu. Meanwhile, the activities of antioxidant enzymes (APX, CAT, SOD, POD) and the contents of nonenzymatic antioxidants (MDA, H₂O₂, ASA, GSH) were enhanced in treated jujubes, thereby reducing the content of ROS. In addition, energy metabolism enzyme activities (H⁺-ATPase, Ca²⁺-ATPase, SDH and CCO) and gene expression were also significantly increased, thus maintaining higher energy levels (ATP, ADP, AMP and EC). In summary, GB enhances ATP biosynthesis by increasing energy metabolism. It offers essential energy for the antioxidant metabolism, thus retarding the softening of postharvest jujubes.

An up-to-date review: differential biosynthesis mechanisms and enrichment methods for health-promoting anthocyanins of citrus fruits during processing and storage

Anthocyanins, naturally found in citrus, play key roles in improving the qualities of citrus fruits and products. Dietary consumption of fruit-derived anthocyanins is concerned increasingly owing to health-promoting properties. However, anthocyanins are vulnerable to many physical and chemical factors during processing and storage, affecting fruit qualities and consumer acceptance. Thus, the aim of this review is to focus on main advances in chemical structures, differential biosynthesis mechanisms, enrichment methods, and bioactivities of anthocyanins in pigmented and unpigmented citrus fruits. In this review, anthocyanin species and concentrations display tissue specificity in citrus, and the chemical structures and contents of main anthocyanins are summarized. For differential biosynthesis mechanisms, the reasons why most citrus fruits lose the ability of anthocyanin biosynthesis compared with pigmented fruits, and the molecular differences of biosynthesis mechanisms in pigmented citrus fruits are both discussed in detail. Furthermore, anthocyanins' enrichment methods (low-temperature stimulus, light irradiation, xenobiotics inductions, and ripeness influence) during processing and storage have been summarized, which achieve quality improvement by promoting structural gene expression, reducing anthocyanin-degrading enzyme activities, or altering DNA methylation status. Meantime, the health benefits of extract from pigmented citrus and their waste are mentioned, which provides a new approach for citrus waste recycling. HIGHLIGHTSChemical structures of individual anthocyanins in citrus are reviewed.Differential anthocyanin biosynthesis in citrus depends on mutations of Ruby genes.Anthocyanins are enriched in response to exogenous stimulus during storage.Health benefits of extract in blood oranges and their waste are summarized.