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The aim of this research was to systematically evaluate the impact of varying ripeness stages (categorized into five distinct levels: I, II, III, IV, and V) on the drying behavior, moisture status, cellular injury, texture, rehydration properties, bioactive compounds, antioxidant activities, and sensory attributes of peaches. The ultimate goal was to identify the optimal ripeness stage of peaches for hot-air drying. Results demonstrated that significant disparities exist in drying characteristics among peaches of different ripeness levels. Peaches at ripeness stage III exhibited the most efficient drying kinetics, characterized by the shortest drying duration, highest drying rate, and maximum moisture diffusion coefficient. This was followed by peaches in stages II, I, IV, and V, the differences being attributed to variances in moisture mobility, content, and cellular injury. Additionally, stage III peaches displayed optimal levels of ascorbic acid, total phenolics, antioxidant capacity, and rehydration ratio. Conversely, peaches at stage V excelled in visual appearance, sugar-to-acid ratio, and flavor profile. Consequently, peaches at ripeness stage III are recommended for hot-air drying due to their superior drying efficiency and quality attributes. This study serves as a theoretical foundation for future work on quality categorization and drying methodologies for peaches.

Melatonin reportedly increases chilling tolerance in postharvest peach fruit during cold storage, but information on its effects on cell-wall disassembly in chilling-injured peaches is limited. In this study, we investigated the role of cell-wall depolymerization in chilling-tolerance induction in melatonin-treated peaches. Treatment with 100 μM melatonin alleviated chilling symptoms (mealiness) characterized by a decrease in fruit firmness and increase in juice extractability in treated peaches during storage. The loss of neutral sugars, such as arabinose and galactose, in both the 1,2-cyclohexylenedinitrilotetraacetic acid (CDTA)- and Na2CO3-soluble fractions was observed at 7 days in treated peaches, but the contents increased after 28 days of storage. Atomic-force-microscopy (AFM) analysis revealed that the polysaccharide widths in the CDTA- and Na2CO3-soluble fractions in the treated fruit were mainly distributed in a shorter range, as compared with those in the control fruit. In addition, the expression profiles of a series of cell-wall-related genes showed that melatonin treatment maintained the balance between transcripts of PpPMEand PpPG, which accompany the up-regulation of several other genes involved in cell-wall disassembly. Taken together, our results suggested that the reduced mealiness by melatonin was probably associated with its positive regulation of numerous cell-wall-modifying enzymes and proteins; thus, the depolymerization of the cell-wall polysaccharides in the peaches treated with melatonin was maintained, and the treated fruit could soften gradually during cold storage.

Low temperatures are known to destroy cell membranes’ structural integrity by affecting the remodeling of their phospholipids. Fruits stored at low temperature are prone to chilling injury, characterized by discoloration, absence of ripening, surface pitting, growth inhibition, flavor loss, decay, and wilting. Phosphatidic acid, a vital second-messenger lipid in plants, is known to accumulate in response to different kinds of stress stimuli. However, the regulatory mechanism of its production from the degradation of phospholipids remains poorly understood. We identified two cold-responsive NAC (NAM/ATAF1/CUC2) transcription factors from bananas, namely, MaNAC25 and MaNAC28, which negatively regulated cold tolerance in banana fruits by upregulating the expression of phospholipid degradation genes in banana fruits. Furthermore, MaNAC25 and MaNAC28 formed a positive feedback loop to induce phospholipid degradation and produce phosphatidic acid. In contrast, ethylene directly inhibited the degradation of phospholipids in banana and transgenic tomato fruits. In addition, ethylene reduced the activity of MaNAC25 and MaNAC28, thereby inhibiting phospholipid degradation. To conclude, NAC-mediated membrane lipid remodeling negatively regulates the cold tolerance of banana and transgenic tomato fruits.

The carrier-envelope phase of the ultrashort pulsed Laguerre-Gaussian beam is studied. The order of Laguerre function affects seriously the variations of the carrier-envelope phase with the propagation distance increasing. The beam waist also affects the carrier-envelope phase in a few Rayleigh distances. The variation of the carrier-envelope phase is larger on the axis than on the beam periphery in propagation.