Changes of Morphology, Chemical Compositions, and the Biosynthesis Regulations of Cuticle in Response to Chilling Injury of Banana Fruit During Storage

Postharvest Physiology and Handling of Guava Fruit

Guavas are typical tropical fruit with high nutritional and commercial value. Because of their thin skin and high metabolic rate, guavas are highly susceptible to water loss, physical damage, and spoilage, severely limiting their shelf-life. Guavas can typically only be stored for approximately one week at room temperature, making transportation, storage, and handling difficult, resulting in low profit margins in the industry. This review focuses on the physiological and biochemical changes and their molecular mechanisms which occur in postharvest guavas, and summarizes the various management strategies for extending the shelf-life of these sensitive fruits by means of physical and chemical preservation and their combinations. This review also suggests future directions and reference ideas for the development of safe and efficient shelf-life extension techniques.

Enhanced Preservation of Climacteric Fruit with a Cellulose Nanofiber-Based Film Coating

Bananas are a typical climacteric fruit with high respiration and ethylene production rates after harvest, and they show rapid ripening-senescence phenotypes. Here, we demonstrate that carboxymethylcellulose nanofibers (CM-CNFs) and red cabbage extracts (RCE) can be used as a unique film coating formulation for enhancement of the shelf-life of fruit. A CM-CNF suspension solution is created through a process involving chemical modification, followed by mechanical grinding. It has a high aspect ratio that allows for the creation of a thin and transparent film on the surface of bananas. The cross-linked CM-CNF hydrogel forms a dense film layer on the banana surface during dehydration and prevents respiration and weight loss. RCE contains polyphenols acting as antioxidants, which prevent the appearance of black dots on the banana peels. It serves to mitigate the browning of banana skins and also hinders the respiration process, consequently slowing the aging of bananas.

A comprehensive study from the micro- to the nanometric scale: Evaluation of chilling injury in tomato fruit (Solanum lycopersicum)

Tomato fruit is susceptible to chilling injury (CI) during its postharvest handling at low temperature. The symptoms caused by this physiological disorder have been commonly evaluated by visual inspection at a macro-observation scale on fruit surface; however, the structure at deeper scales is also affected by CI. This work aimed to propose a descriptive model of the CI development in tomato tissue under the micro-scale, micro-nano-scale and nano-scale approaches using fractal analysis. For that, quality and fractal parameters were determined. In this sense, light microscopy, Environmental Scanning Electron Microscopy (ESEM) and Atomic Force Microscopy (AFM) were applied to analyse micro-, micro-nano- and nano-scales, respectively. Results showed that the morphology of tomato tissue at the micro-scale level was properly described by the multifractal behaviour. Also, generalised fractal dimension (Dq=0) and texture fractal dimension (FD) of CI-damaged pericarp and cuticle were higher (1.659, 1.601 and 1.746, respectively) in comparison to non-chilled samples (1.606, 1.578 and 1.644, respectively); however, FD was unsuitable to detect morphological changes at the nano-scale. On the other hand, lacunarity represented an appropriate fractal parameter to detect CI symptoms at the nano-scale due to differences observed between damaged and regular ripe tissue (0.044 and 0.025, respectively). The proposed multi-scale approach could improve the understanding of CI as a complex disorder to the development of novel techniques to avoid this postharvest issue at different observation scales.

Development and Application of Poly (Lactic Acid)/Poly (Butylene Adipate-Co-Terephthalate)/Thermoplastic Starch Film Containing Salicylic Acid for Banana Preservation

Bananas are susceptible to the effects of endogenous enzymatic, leading to their rapid decay and deterioration. In order to mitigate economic losses and prolong the shelf life of bananas, the objective of this study was to develop a new and green gas-regulating packaging film. In this study, an active gas-regulating packaging film was prepared by extrusion, with mobil composition of matter (MCM)-41 loaded with salicylic acid (SA) as the active agent and poly (lactic acid) (PLA), poly (butylene adipate-co-terephthalate) (PBAT), and thermoplastic starch (TPS) as the base materials. The obtained films included PLA/PBAT/TPS, PLA/PBAT/TPS-SA, and PLA/PBAT/TPS-MCSA. These films were subsequently applied to banana preservation. The study focused on the variations in soluble solid content (SSC), rate of weight loss (RWL), malondialdehyde (MDA) content, and polyphenol oxidase (PPO) activity of bananas during the preservation process. The results showed that, compared with the PLA/PBAT/TPS film, the oxygen transmission rate of the PLA/PBAT/TPS-MCSA film increased from 384.36 ± 22.06 cm3·m-2·24 h-1·0.1 MPa-1 to 543.10 ± 3.47 cm3·m-2·24 h-1·0.1 MPa-1. Throughout the preservation period, the PLA/PBAT/TPS-MCSA film exhibited superior performance, effectively retarding the increase in banana SSC, RWL, and MDA while inhibiting the elevation of PPO activity and prolonging the shelf life of bananas by 4-5 days. However, this study needs to further investigate the mechanism of function of MCM-41 loaded with SA in banana preservation.

Alteration of surface morphologies and chemical composition of cuticle in response to chilling injury in papaya (Carica papaya L.) after harvest

The alteration of surface microstructures and chemical composition in cuticle of papaya fruit in response to chilling stress were comparatively studied between cultivars of 'Risheng' and 'Suihuang' after harvest. Fruit surface was covered by fissured wax layers in both cultivars. The presence of granule crystalloids was cultivar dependent, with higher abundance in 'Risheng' and lower in 'Suihuang'. Various typical very-long-chain aliphatics i.e., fatty acids, aldehydes, n-alkanes, primary alcohols, and n-alkenes dominated waxes; and cutin monomers were prominently 9/10,16-dihydroxyhexadecanoic acid in papaya fruit cuticle. Chilling pitting symptom was accompanied by modification of granule crystalloids into flat appearance and decreased primary alcohols, fatty acids, and aldehydes in 'Risheng', but no evident changes in 'Suihuang'. The response of cuticle to chilling injury in papaya fruit might be not directly related to the overall amount of waxes and cutin monomers, but more likely to the alteration of appearance morphologies and chemical composition in cuticle.

Composition, metabolism and postharvest function and regulation of fruit cuticle: A review

The cuticle of plants, a hydrophobic membrane that covers their aerial organs, is crucial to their ability to withstand biotic and abiotic stressors. Fruit is the reproductive organ of plants, and an important dietary source that can offer a variety of nutrients for the human body, and fruit cuticle performs a crucial protective role in fruit development and postharvest quality. This review discusses the universality and diversity of the fruit cuticle composition, and systematically summarizes the metabolic process of fruit cuticle, including the biosynthesis, transport and regulatory factors (including transcription factors, phytohormones and environmental elements) of fruit cuticle. Additionally, we emphasize the postharvest functions and postharvest regulatory technologies of fruit cuticle, and propose future research directions for fruit cuticle.

Morphological and antioxidant responses of Nopalea cochenillifera cv. Maya (edible Opuntia sp. "Kasugai Saboten") to chilling acclimatization

To clarify the wintering ability of the cactus Nopalea cochenillifera cv. Maya (edible Opuntia sp., common name "Kasugai Saboten"), we investigated the effects of temperature and antioxidant capacity on chilling acclimatization. We analyzed the anatomy of cladode chlorenchyma tissue of plants exposed to light under chilling. We found that chilling acclimatization can be achieved by exposure to approximately 15 °C for 2 weeks and suggest that it is affected by whether or not antioxidant capacity can recover. The overwintering cacti had the thinnest cuticle but firm cuticular wax, which is important in the acquisition of low temperature tolerance under strong light. In cacti with severe chilling injury, round swollen nuclei with clumping chloroplasts were localized in the upper part (axial side) of the cell, as though pushed up by large vacuoles in the lower part. In overwintering cacti, chloroplasts were arranged on the lateral side of the cell as in control plants, but they formed pockets: invaginations with a thin layer of chloroplast stroma that surrounded mitochondria and peroxisomes. Specific cellular structural changes depended on the degree of chilling stress and provide useful insights linking chloroplast behavior and structural changes to the environmental stress response.

The role of cuticle in fruit shelf-life

Ensuring the availability of high-quality fresh fruits requires the development of strategies to maintain prolonged shelf-life. The plant cuticle is a modification of the outer epidermal cell wall and, as such, acts as a barrier with the environment. Understanding how the cuticle naturally changes during postharvest is crucial to address the potential effect of different storage conditions on the cuticle biophysical properties. The impact of different cuticle traits in fruit water loss, its relevance in several fruit-skin disorders, and its participation in postharvest decay caused by pathogens are discussed. Future challenges to study in vivo the physicochemical properties of the cuticle are also addressed.