Prunus persica (L.) Batsch blossom soluble dietary fiber synergia polyphenol improving loperamide-induced constipation in mice via regulating stem cell factor/C-kit, NF-κB signaling pathway and gut microbiota.

This study aimed to investigate the ameliorating effects of peach blossom soluble dietary fiber (PBSDF) and polyphenol (PBP) combinations on loperamide (Lop)-induced constipation in mice, together with the possible mechanism of action. The results demonstrated that the combined use of PBSDF and PBP could synergistically accelerate the gastrointestinal transit rate and gastric emptying rate, shorten first red fecal defecation time, accelerate the frequency of defecation, regulate the abnormal secretion of gastrointestinal neurotransmitters and pro-inflammatory cytokines, and down-regulate the expressions of AQP3 and AQP8. Western blotting and RT-qPCR analysis confirmed that PBSDF + PBP up-regulated the protein and mRNA expressions of SCF and C-kit in SCF/C-kit signaling pathway, and down-regulated pro-inflammatory mediator expressions in NF-κB signaling pathway. 16S rRNA sequencing showed that the diversity of gut microbiota and the relative abundance of specific strains, including Akkermansia, Bacteroides, Ruminococcus, Lachnospiraceae_NK4A136_group, and Turicibacter, rehabilitated after PBSDF + PBP intervention. These findings suggested that the combination of a certain dose of PBSDF and PBP had a synergistic effect on attenuating Lop-induced constipation, and the synergistic mechanism in improving constipation might associated with the regulating NF-κB and SCF/C-kit signaling pathway, and modulating the specific gut strains on constipation-related systemic types. The present study provided a novel strategy via dietary fiber and polyphenol interactions for the treatment of constipation.

Synergism of (E)-ß-farnesene and Its Analogue to Insecticides against the Green Peach Aphid Myzus persicae.

With high aphid-repellent activity but low stability, (E)-ß-farnesene (EßF), the major component of the aphid alarm pheromone, can be used as a synergist to insecticides. Some EßF analogues possess both good aphid-repellent activity and stability, but the synergistic effect and related mechanism are still unclear. Therefore, this study investigated the synergistic effect and underlying mechanism of the EßF and its analogue against the aphid Myzus persicae. The results indicated that EßF and the analogue showed significantly synergistic effects to different insecticides, with synergism ratios from 1.524 to 3.446. Mechanistic studies revealed that EßF and the analogue exhibited effective repellent activity, significantly upregulated target OBP genes by 161 to 731%, increased aphid mobility, and thereby enhanced contact with insecticides. This research suggests that the EßF analogue represents a novel synergist for insecticides, with the potential for further application in aphid control owing to its enhanced bioactivity and the possibility of reducing insecticide doses.

Fire-resistant and low-temperature self-healing bio-based hydrogel electrolytes based on peach gum polysaccharide/sisal nanofibers for flexible supercapacitors.

The introduction of flame retardancy and low-temperature self-healing capacities in hydrogel electrolytes are crucial for promoting the cycle stability and durability of the flexible supercapacitors in extreme environments. Herein, biomass-based dual-network hydrogel electrolyte (named PSBGL), was synthesized with borax crosslinked peach gum polysaccharide/sisal nanofibers composite, and its application in flexible supercapacitors was also investigated in detail. The dynamic cross-linking of the dual-network endows the PSBGL with excellent self-healing performance, enabling ultrafast self-healing within seconds at both room temperature and extreme low temperatures. The PSBGL bio-based hydrogel electrolyte can maintain the integrity of the carbon layer structure with limiting oxygen index of 56 % after 60 s of combustion under a flame gun. Additionally, the PSBGL exhibits high ionic conductivity (30.12 mS cm-1), good tensile strength (1.78 MPa), and robust adhesion to electrodes (1.15 MPa). The assembled supercapacitors demonstrate a high specific capacitance of 187.8 F g-1 at 0.5 A g-1, with 95.9 % capacitance retention rate after 10,000 cycles at room temperature. Importantly, even under extreme temperatures of 60 °C and -35 °C, the supercapacitors can also maintain high capacitance retention rates of 90.1 % and 86.5 % after 10,000 cycles. This work fills the gap between biomaterial design and high-performance flexible supercapacitors.

Immunochromatographic strip for rapid and sensitive detection of bupirimate residues in peach, orange, and carrot.

Bupirimate (BPM) is a high-efficiency and low-toxicity fungicide used to combat powdery mildew in crops. To mitigate potential health risks to consumers resulting from improper BPM usage, we prepared a monoclonal antibody against BPM based on novel hapten synthesis, which has high sensitivity and strong specificity, and then successfully designed a colloidal gold-based immunochromatographic (ICG) strip. The newly designed ICG strip was then employed for detecting BPM residues in peach, orange, and carrot. The results show that for the peach, orange, and carrot samples, the calculated detection limits of the ICG strip are 9.36, 0.79, and 0.57 ng/g, respectively, and that it is resistant to the matrix effect and meets the maximum residue limit requirements of European Commission for BPM. Therefore, this developed ICG strip is expected to enable swift detection of BPM residues on the spot.

Zein-based nisin-loaded electrospun nanofibers as active packaging mats for control of Listeria monocytogenes on peach.

Zein-based nanofibers (NFs) functionalized with nisin (NS), reinforced with montmorillonite nanoclay (nMMT) were fabricated by uniaxial electrospinning (ES) for the first time to preserve yellow peach. Spinnability/viscosity/conductivity optimizations generated porous (95.09%), bead-free, ultrathin (119 nm) NFs of low hydrophobicity (26.05°). Glutaraldehyde (GTA) crosslinking fostered positive outcomes of tensile strength (1.23 MPa), elongation (5.0%), hydrophobicity (99.46°), surface area (201.38 m2.g-1), pore size (2.88 nm), thermal stability (Tmax = 342 °C), antioxidant/cytotoxic activities in optimized NFs that released NS sustainably according to Korsmeyer-Peppas model indicating a Fickian diffusion mechanism with R2 = 0.9587. The novel NFs inhibited growth of Listeria monocytogenes/aerobic mesophilic populations in peach after 4 days of abusive storage, evincing their robustness in food contact applications. Simultaneously, quality parameters (moisture/texture/browning/total soluble solids/pH) and peach physical appearance were maintained for up to 8 days, endorsing the practical value of zein-based NFs as a non-thermal postharvest intervention for prolonging fruits storage life.

Absorption enhancement of peach kernel oil on hydroxysafflor yellow A in safflower extracts and its mechanisms.

Carthamus tinctorius L. (Safflower) is extensively used as a functional food and herbal medicine, with its application closely associated with hydroxysafflor yellow A (HSYA). However, the low oral bioavailability of HSYA in safflower extract (SFE) limits its health benefits and application. Our study found that co-administration of 250, 330, and 400 mg/kg peach kernel oil (PKO) increased the oral bioavailability of HSYA in SFE by 1.99-, 2.11-, and 2.49-fold, respectively. The enhanced bioavailability is attributed to improved lipid solubility and intestinal permeability of HSYA in SFE due to PKO. PKO is believed to modify membrane fluidity and tight junctions, increase paracellular penetration, and inhibit the expression and function of P-glycoprotein, enhancing the transcellular transport of substrates. These mechanisms suggest that PKO is an effective absorption enhancer. Our findings provide valuable insights for developing functional foods with improved bioavailability.

Effects of ultraviolet C on the quality and aroma volatile in peach fruit during postharvest storage.

The study investigated the impact of UV-C irradiation on peach fruit quality during postharvest storage, with a focus on aroma changes and the mechanisms involving lipoxygenase metabolism. Results showed that UV-C irradiation at a dosage of 1.5 kJ/m2 was found to preserve the quality attributes of peach fruit during ambient storage, as evidenced by high flesh firmness, inhibition of weight loss and respiration rate, as well as high values of L* and ascorbic acid. Meanwhile, UV-C irradiation led to an increase in the contents of aroma-related volatiles, particularly esters and lactones, compared to non-irradiated fruit. Our results suggested that the enhanced emission of aroma-related volatiles in UV-C irradiated peach fruit was linked to elevated levels of unsaturated fatty acids. Besides, UV-C induced the expressions and activities of enzymes in the lipoxygenase pathway, thus promoting the synthesis of esters and lactones, which contribute to the enhanced aroma in peach fruit.

Gum arabic coating alleviates chilling injury of cold-stored peach by regulating reactive oxygen species, phenolic, and sugar metabolism.

In this study, gum arabic (GA) coating was employed to mitigate chilling injury in peach fruit, and it was observed that 10% GA coating exhibited the most favorable effect. GA coating significantly inhibited the decline of AsA content and enhanced antioxidant enzyme activity in peach fruit, thereby enhancing reactive oxygen species (ROS) scavenging rate while reducing its accumulation. Simultaneously, GA coating inhibited the activity of oxidative degradation enzymes for phenolics and enhanced synthase activity, thus maintaining higher levels of total phenolics and flavonoids in fruits. Additionally, compared to the control fruit, GA-coated fruits demonstrated higher concentrations of sucrose and sorbitol, accompanied more robust activity of sucrose synthase and sucrose phosphate synthase, as well as reduced activity of acid invertase and neutral invertase. Our study demonstrates that GA coating can effectively enhance the cold resistance of peach fruit by regulating ROS, phenolics, and sugar metabolism, maintaining high levels of phenolics and sucrose while enhancing antioxidant activity.

Unsaponifiable Compounds and Phenols Content, Antioxidant and Antitrypsin Activities of Prunus persica Kernel Oil.

Although peach kernels are rich in oil, there is a lack of information about its chemical and biological properties. Therefore, the purpose of this study was to determine the lipid profile, antioxidant capacity, and trypsin inhibitory propriety of peach oil extracted from two varieties (sweet cap and O'Henry) cultivated in Tunisia. The investigated peach kernel oil contains significant amount of unsaponifiable (2.1±0.5-2.8±0.2% of oil) and phenolic compounds (45.8±0.92-74.6±1.3 mg GAE/g of oil). Its n-alkane profile was characterized by the predominance of tetracosane n-C24 (47.24%) followed by tricosane n-C23 (34.43%). An important total tocopherol content (1192.83±3.1 mg/kg oil) has been found in sweet cap cultivar. Although rich in polyphenols and tocopherols, the tested oil did not display an inhibitory effect on trypsin. However, all peach oil samples showed effective antioxidant capacity and the highest values (86.34±1.3% and 603.50±2.6 µmol TE/g oil for DPPH test and ORAC assay, respectively) were observed for sweet cap oil. Peach oil has an excellent potential for application in the food and pharmaceutical industries as source of naturally-occurring bioactive substances.

Effect of pH on the emulsifying performance of protein-polysaccharide complexes.

BACKGROUND: Protein-polysaccharide complexes have been successfully used for emulsion stabilization. However, it is unclear how the complex's surface charge influences aggregation stability and coalescence stability of emulsions, and whether a low charged interfacial film can still maintain the coalescence stability of oil droplets. In the present study, the effects of pH (around the pI of protein) on the aggregation and coalescence stability of emulsions were investigated. RESULTS: Whey protein isolate (WPI) and peach gum polysaccharides (PGP) complexes (WPI-PGP complexes) were synthesized at pH 3, 4 and 5. Their sizes were 598, 274 and 183 nm, respectively, and their ζ-potentials were +2.9, -8.6 and -22.8 mV, respectively. Interface rheological experiments showed that WPI-PGP complex at pH 3 had the lowest interfacial tension, and formed the softest film compared to the complexes at pH 4 and 5. Microfluidic experiments showed that all WPI-PGP complexes were able to stabilize droplets against coalescence within short timescales (milliseconds). At pH 3, no coalescence was observed even under conditions where the continuous phase flow influenced the shape of oil droplets (from spheres to ellipsoids). At pH 4 and 5, the model emulsions were stable over 16 days of storage, extensive aggregation and creaming occurred at pH 3 after 8 days. Importantly, no coalescence took place. CONCLUSION: The present study confirmed that the aggregation stability of the emulsions was mainly determined by the surface charge of the complex, whereas the coalescence stability of emulsions is expectedly determined by steric repulsion, providing new insights into how to prepare stable food emulsions. © 2024 Society of Chemical Industry.

Evaluation of gases emission and enzyme dynamics in sheep manure compost occupying with peach shell biochar.

The effect of peach shell biochar (PSB) amendment on sheep manure (SM) composting was investigated. Five different ratios of PSB were applied (0%, 2.5%, 5%, 7.5%, and 10% PSB), and named T1 to T5, and run 50 days of composting experiment. It was found that PSB (especially 7.5% and 10%) could improve the compost environment, regulate the activity of microorganisms and related enzymes, and promote the decomposition of compost. 7.5% and 10% PSB advanced the heap into the thermophilic stage and increased the maximum temperature, while also increasing the germination index by 1.40 and 1.39 times compared to control. Importantly, 10% PSB effectively retained more than 60% of carbon and 55% of nitrogen by inhibiting the excess release of NH3 and greenhouse gases. High proportion PSB amendment increased the activity of dehydrogenase and cellulase, but inhibited protease and urease. The correlation results indicated that PSB changed the key bacterial genus, and there was a stronger association with environmental factors at 7.5% and 10%. Therefore, 7.5% and 10% peach shell biochar can be used as appropriate proportions to improve composting conditions.

Thermodynamic and structural investigation of oily wastewater treatment using peach kernel and walnut shell based activated carbon.

Despite the many articles about activated carbon with different precursors in adsorption process, no in-depth research has been carried out to understand the causes of the difference in surface adsorption characteristics of activated carbon with different precursors and different activation processes. In this work, the ability of two active carbon adsorbents made of walnut shell and peach kernel by two chemical and physical methods (totally 4 different types of activated carbon) in treatment of oily wastewater including diesel, gasoline, used oil or engine lubricant has been compared. The results show that the chemical activated peach carbon active with 97% hardness has provided the highest hardness and physical activated walnut carbon active has obtained the lowest hardness value (87%). It is also found that peach activated carbon has a higher iodine number than walnut activated carbon, and this amount can be increased using chemical methods; Therefore, the highest amount of Iodine Number is related to Peach activated carbon that is made by chemical method (1230 mg/g), and the lowest amount of iodine number is seen in walnut activated carbon that is made by physical method (1020 mg/g). moreover, the pore diameter of physical activated carbon is lower than chemical activated carbon in all cases. So that the pore diameter of chemical activated peach carbon active is equal to 22.08 µm and the measured pore diameter of physical activated peach carbon active is equal to 20.42 µm. These values for walnut are obtained as 22.74 µm and 21.86 µm, respectively. Furthermore, the temperature and pH effects on the adsorption of different synthesized oily wastewater was studied and it was found that a decrease in adsorption can be seen with an increase in temperature or decreasing the pH value, which can be referred to this fact that the process of adsorption is an exothermic process. Finally, to analyze the compatibility of adsorption isotherms with experimental data and to predict the adsorption process, three different isotherms named Langmuir, Temkin, and Freundlich isotherms were applied and their parameters were correlated. The correlation results show that the Langmuir isotherm had the best correlation in all cases compared to the Freundlich and Temkin isotherms, based on the correlation coefficient, and the calculated R2 values which was greater than 0.99 in all the studied cases.

The impact of ultrasonic-assisted extraction on the in vitro hypoglycemic activity of peach gum polysaccharide in relation to its conformational conversion.

BACKGROUND: Peach gum (PG) is an exudate of the peach tree (Prunus persica of the Rosaceae family), which consists primarily of polysaccharides with a large molecular weight and branching structure. Consequently, PG can only swell in water and does not dissolve easily, which severely limits its application. Current conventional extraction methods for PG polysaccharide (PGPS) are time consuming and inefficient. This study investigated the impact of ultrasonic-assisted extraction (UAE) on PGPS structure and conformation, and their relationship to hypoglycemic activity in vitro. RESULTS: In comparison with conventional aqueous extraction, UAE enhanced PGPS yielded from 28.07-32.83% to 80.37-84.90% (w/w) in 2 h. It drastically decreased the molecular size and conformational parameters of PGPS, including weight-average molecular weight (Mw), number-average molecular weight (Mn), z-average radius of gyration (Rg), hydrodynamic radius (Rh) and instrinsic viscosity ([η]) values. Peach gum polysaccharide conformation converted extended molecules to flexible random coil chains or compact spheres with no obvious primary structure alteration. Furthermore, UAE altered the flow behavior of PGPS solution from that of a non-Newtonian fluid to that of a Newtonian fluid. As a result, PGPS treated with UAE displayed weaker inhibitory activity than untreated PGPS, mostly because UAE weakens the binding strength of PGPS to α-glucosidase. However, this negative effect of UAE on PGPS activity was compensated by the increased solubility of polysaccharide. This enabled PGPS to achieve a wider range of doses. CONCLUSION: Ultrasonic-assisted extraction is capable of degrading PGPS efficiently while preserving its primary structure, resulting in a Newtonian fluid solution. The degraded PGPS conformations displayed a consistent correlation with their inhibitory effect on α-glucosidase activity. © 2024 Society of Chemical Industry.

The potential of glucosidase and glucose oxidase for aroma improvement in concentrated peach puree based on volatilomics and metabolomics.

Cooked off-flavor was produced during the processing of concentrated peach puree (CPP), which led to aroma deterioration. Enzymatic treatment was beneficial in eliminating off-flavors and improving the aroma quality. Herein, the efficacy of glycosidase (AR2000), glucose oxidation (GOD), and their combination on the inhibition of off-flavors and aroma enhancement were evaluated. Compared with CPP, contents of benzaldehyde, benzyl alcohol, nonanal, and linalool increased by 198%, 1222%, 781%, and 71% after AR2000 treatment via the metabolisms of shikimate, glucose, linoleic acid, and linolenic acid, leading to the strengthening of floral and grassy. Due to the removal of 1-octen-3-one via linolenic acid metabolism, cooked off-flavor could be significantly weakened by GOD. Furthermore, Furthermore, the combination of AR2000 and GOD could not only inhibit the production of 1-octen-3-one to weaken the cooked note but also enhance grassy and floral attributes via the increase of aldehydes and alcohols.

Understanding the two-stage degradation process of peach gum polysaccharide within ultrasonic field.

This study investigated the dynamic degradation process of peach gum polysaccharide (PGPS) within ultrasonic field. The results show that the molecular weight, intrinsic viscosity, and polydispersity of PGPS were rapidly reduced within the initial 30 min and then gradually decreased. The solubility of PGPS was drastically improved from 3.0% to 40.0-42.0% (w/w) after 120 min. The conformation of PGPS changed from an extended chain to a flexible random coil within initial time of ultrasound, and gradually tended to be compact spheres. The apparent viscosity of PGPS significantly decreased after 30 min, and PGPS solution exhibited a near-Newtonian fluid behavior. It is possible that these above changes are a result of random cleavage of the decrosslinking and the backbone of PGPS, resulting in the preservation of its primary structure. The results will provide a fundamental basis for orientation design and process control of ultrasonic degradation of PGPS.

[In silico analysis of Cit s 2: A highly conserved profilin]. / Análisis in silico de cit s 2: una profilina altamente conservada.

OBJECTIVE: Analyze phylogenetic relationships and molecular mimicry of Cit s 2 and other plant profilins. METHODS: Online bioinformatics tools including Basic Local Alignment Search Tool (BLASTP), PRALINE and MEGA were used for multiple alignments and phylogenetic analysis. A 3D-homology model of Cit s 2 was predicted. Models were calculated with MODELLER. The best model was selected with the model scoring option of MAESTRO. Conserved regions between Cit s 2 and other profilins were located on the 3D model and antigenic regions were predicted by ElliPro server (3-5). RESULTS: Cit s 2 amino acid sequence (Uniprot code:P84177) was compared with other 30 profilins from different allergenic sources. The identity between Cit s 2 and other profilins ranged between 82 and 99%. The highest identity was observed with Cucumis melo (99%) followed by Prunus persica (98%) and Malus domestica (92%). High conserved antigenic regions were observed on the 3D predicted model. Seven lineal and six discontinuous epitopes were found in Cit s 2. CONCLUSION: High conserved antigenic regions were observed on the 3D predicted model of Cit s 2, which might involve potential cross-reactivity between Cit s 2 and other profilins. Future studies are needed to further analyze these results.

OBJETIVO: Analizar las relaciones filogenéticas y el mimetismo molecular de Cit s 2 y otras profilinas vegetales. MÉTODOS: Se utilizaron herramientas bioinformáticas en línea, incluida la de búsqueda de alineación local básica (BLASTP), PRALINE y MEGA, para alineamientos múltiples y análisis filogenético. Se predijo un modelo de homología 3D de Cit s 2. Los modelos se calcularon con MODELLER. El mejor modelo fue seleccionado con la opción de puntuación de modelo de Maestro. Las regiones conservadas entre Cit s 2 y otras profilinas se ubicaron en el modelo 3D y las regiones antigénicas fueron predichas por el servidor ElliPro (3-5). RESULTADOS: La secuencia de aminoácidos de Cit s 2 (código Uniprot: P84177), se comparó con otras 30 profilinas de diferentes fuentes alergénicas. La mayor identidad se observó con Cucumis melo (99%) seguida de Prunus persica (98%) y Malus domestica (92%). Se observaron regiones antigénicas altamente conservadas en el modelo predicho en 3D. Se encontraron siete epítopes lineales, y seis epítopes discontinuos en Cit s 2. CONCLUSIÓN: Se observaron regiones antigénicas altamente conservadas en el modelo 3D predicho de Cit s 2, lo que podría implicar una posible reactividad cruzada entre Cit s 2 y otras profilinas. Se necesitan estudios futuros para analizar más a fondo estos resultados.

1-MCP treatment improves the postharvest quality of Jinxiu yellow peach by regulating cuticular wax composition and gene expression during cold storage.

This study aimed to analyze the effect of 1-methylcyclopropene (1-MCP) treatment on the postharvest quality, epidermal wax morphology, composition, and gene expression of Jinxiu yellow peach during cold storage. The results showed that 1-MCP treatment could maintain the postharvest quality of peach fruit as compared to control (CK) during cold storage. The wax crystals of peach fruit were better retained by 1-MCP, and they still existed in 0.6 and 0.9 µL/L 1-MCP treated fruit at 36 days. The total wax content in all the fruit increased first and then decreased during cold storage. Meanwhile, n-alkanes and primary alcohols were the main wax components. Compared to CK, 1-MCP treatment could delay the reduction of wax content during cold storage. The correlation analysis indicated that the postharvest quality of yellow peach was mainly affected by the contents of fatty acids and triterpenoids in cuticular wax. The transcriptomics results revealed PpaCER1, PpaKCS, PpaKCR1, PpaCYP86B1, PpaFAR, PpaSS2, and PpaSQE1 played the important roles in the formation of peach fruit wax. 1-MCP treatment upregulated PpaCER1 (18785414, 18786441, and 18787644), PpaKCS (18774919, 18789438, and 18793503), PpaKCR1 (18790432), and PpaCYP86B1 (18789815) to deposit more n-alkanes and fatty acids during cold storage. This study could provide a new perspective for regulating the postharvest quality of yellow peach in view of the application of cuticular wax. PRACTICAL APPLICATION: 'Jinxiu' yellow peach fruit is favorable among consumers because of its high commercial value. However, it ripens and deteriorates rapidly during storage, leading to serious economic loss and consumer disappointment. The effect of 1-methylcyclopropene (1-MCP) treatment on the postharvest quality, epidermal wax morphology, composition, and genes regulation of 'Jinxiu' yellow peach during cold storage was assessed. Compared to control, 1-MCP treatment could retain the storage quality of yellow peach by affecting cuticular wax composition and gene expression. This study could provide new perspective for regulating the postharvest quality of yellow peach in view of the application of cuticular wax.

Textural formation of instant controlled pressure drop-dried peach chips: Investigation of the electrical, thermal, and textural properties of predried peach slices with osmotic dehydration pretreatment.

In this study, the effect of osmotic dehydration (OD) pretreatment with various sugar (erythritol, glucose, and trehalose) on the quality of hot-air-predried peach slices was investigated, particularly focusing on electrical properties, texture, thermal stability, and cell wall strength. Furthermore, the correlation between the properties of predried peach slices and the texture of the instant controlled pressure drop (DIC) dried peach chips was explored. OD pretreatments improved the stability and integrity of the cell wall and cell membrane of pre-dried peach slices, which inhibited the excessive expansion of samples during DIC drying. Especially, peach chips with trehalose-OD exhibited the highest crispiness (1.05 mm), the highest hardness (101.34 N) was obtained in erythritol-OD samples. Overall, the type of osmotic agents affected the texture of DIC peach chips with OD pretreatments. It should be noted that trehalose is a promising osmotic agent for controlling and regulating the quality of DIC peach chips.

Insight into the effect of osmosis agents on macro- and micro- texture, water distribution, and thermal stability of instant controlled pressure drop drying peach chips.

To investigate the influence of sugar structure on the quality of peach chips produced using osmotic dehydration (OD) in combination with instant controlled pressure drop (DIC) drying, erythritol, glucose, maltose, and trehalose were selected as osmotic agents. The properties of the osmotic solutions, as well as the macro- and micro-texture, water distribution, and thermal stability of peach chips were investigated. Results showed that OD pretreatments inhibited the formation of large cavity structures. The highest hardness (101.34 N) and the lowest hydrophobicity (0°) were obtained in erythritol-OD samples. Trehalose-OD samples with the most homogeneous pore structure exhibited the highest crispness (1.05 mm) and the highest glass transition temperature (52.06 °C). Various absorption peaks of peach chips pretreated with different OD methods, characterized by Raman spectroscopy, suggested changes in composition and functional groups due to the diffusion of sugars into the cells of peach tissues, which also contributed to the higher Tg.

Postharvest melatonin treatment enhanced antioxidant activity and promoted GABA biosynthesis in yellow-flesh peach.

The effects of postharvest melatonin treatment on antioxidant activity and γ-aminobutyric acid (GABA) biosynthesis in yellow-flesh peach fruit stored at 4 °C and 90% RH for 28 d were explored. Results showed that melatonin treatment was effective in maintaining firmness, total soluble solids content and color in peach fruit. Melatonin treatment significantly reduced H2O2 and MDA contents, enhanced high level of non-enzymatic antioxidant system (ABTS∙+ scavenging capacity), and increased the activity or content of antioxidant enzymes including CAT, POD, SOD and APX. Melatonin treatment increased the contents of total soluble protein and glutamate, while reducing total free amino acid content. Moreover, melatonin treatment up-regulated the expression of GABA biosynthesis genes (PpGAD1 and PpGAD4) and suppressed the expression of GABA degradation gene (PpGABA-T), resulting in the accumulation of endogenous GABA. These findings indicated that melatonin treatment exerted positive effects on improving antioxidant activity and promoting GABA biosynthesis in yellow-flesh peach fruit.