Recent Advances in Postharvest Physiology and Preservation Technology of Peach Fruit: A Systematic Review

Abstract

Peaches are highly susceptible to rapid deterioration and bacterial infection during postharvest transportation and storage, leading to significant losses. In order to maintain peach fruit postharvest quality and extend its shelf life, it is critical to understand the physiological changes in postharvest fruit and implement effective postharvest technologies. This paper reviews the major postharvest physiological changes in peach fruit, including respiration, ethylene, hormones, texture, sugars, amino acids, phenolics, and volatiles, analyzes the major postharvest peach fruit diseases and their control techniques (covering brown rot, soft rot, and gray mold), and summarizes approaches to extend the storage life of peach fruit and maintain quality through physical, chemical, and biological preservation techniques. This review evaluates the advantages and disadvantages of postharvest peach fruit preservation techniques by analyzing postharvest physiological and nutritional quality, and suggests future research directions aimed at ensuring peach fruit safety and quality assurance.

1. Introduction

Peach (Prunus persica L. Batsch) belongs to the Rosaceae family, native to China, and after more than 4000 years of cultivation history, peach provides a rich variety of resources and cultivation types, planted in more than 80 countries around the world and constituting an important economic crop [1]. According to data from the Food and Agriculture Organization of the United Nations (FAO), the global peach cultivation area and production were 1.56 million hectares and 27.08 million tonnes, respectively, in 2023. China’s peach cultivation area and production were 886,200 hectares and 17.5165 million tonnes, respectively, accounting for 56.75% and 64.69% of the global total. China has thus become the world’s largest peach-producing country [2]. Peaches are a popular fruit enjoyed around the world. They contain minerals, sugars, organic acids, dietary fiber, vitamins, carotenoids, and phenolic compounds, and eating them has a positive effect on the body’s antioxidant and anticancer properties [3].

As a typical climacteric fruit, peach undergoes significant physiological alterations postharvest, characterized by accelerated respiration rates and enhanced ethylene biosynthesis. These metabolic changes trigger rapid fruit senescence, resulting in substantial degradation of flavor compounds and quality deterioration [4,5]. Additionally, peach fruit skin is relatively thin, making it susceptible to mechanical damage and metabolic changes caused by pathogens during transportation and storage. This accelerates postharvest quality deterioration [6]. As times change, consumer demand for fresh fruit and vegetables continues to grow, with a focus on freshness, convenience, and nutritional value. However, postharvest, fruits and vegetables face ongoing issues of physiological metabolism, pathogen spread, and nutrient loss. In the context of population growth and changing consumer habits, postharvest losses are detrimental to economic development [7]. According to statistics, approximately one-third of the annual production of the global peach fruit industry is lost or wasted due to improper storage. Postharvest loss rates for fresh fruit are 2–23% in developed countries and 20–50% in developing countries [8]. To address the challenge of postharvest losses in peach fruit, researchers have developed various preservation strategies aimed at extending storage periods and improving fruit quality. These techniques encompass physical, chemical, and biological methods, as well as their integrated applications, including low-temperature storage [4], heat treatment [9], controlled atmosphere storage [10], ultraviolet treatment [11], chemical preservatives (1-MCP [12], NO [13], H₂S [14]), and plant endogenous hormones (salicylic acid [4], methyl jasmonate [15], melatonin [16]). These technologies primarily function by regulating ethylene biosynthesis and signaling, reducing respiratory metabolic activity, enhancing fruit cold tolerance, and inhibiting microbial growth, thereby maintaining fruit nutritional quality and sensory characteristics while effectively extending storage time.

Although a large number of studies have reported on postharvest preservation techniques for peach fruit, there is still a lack of systematic and comprehensive reviews of the postharvest treatment process. This paper reviews research into the physiology and preservation of peach fruit after harvest, including physiological changes, disease control, and existing technologies. The aim is to provide a theoretical basis for developing and innovating postharvest preservation technology for peach fruit, while encouraging further research into this area.

2. Physiological

Peach fruit undergos a series of complex physiological and metabolic changes during postharvest storage, primarily manifested as a synergistic increase in ethylene production and respiratory rate [5], hormonal influence [17], softening of fruit texture, and alterations in nutrient content [18]. Understanding the dynamic patterns of these physiological activities provides significant guidance for regulating storage environmental parameters, extending fruit shelf life, and maintaining their sensory and nutritional quality.

2.1. Respiration and Ethylene

Ethylene (C₂H₄) is an endogenous hormone found in all higher plants, participating in processes ranging from seed germination to fruit ripening and senescence [19]. Ethylene is closely related to respiration in plant growth, development, and environmental adaptation. When the fruit matures, ethylene production increases greatly and the respiration rate increases simultaneously. The two are closely related and intertwined. Ethylene not only affects the respiration rate, but also affects fruit ripening speed and fruit quality by regulating its own production and signaling [20]. Plant respiration is the core mechanism of energy metabolism in plant cells. It occurs in the mitochondria, and this process involves the key enzyme for ATP synthesis, indicating that respiration is the foundation of energy metabolism, providing the energy for other biochemical reactions [20,21]. The biosynthesis of ethylene primarily involves the conversion of S-adenosylmethionine (SAM) into 1-aminocyclopropane-1-carboxylic acid (ACC) by 1-aminocyclopropane-1-carboxylic acid synthase (ACS), followed by the oxidation of ACC into ethylene by 1-aminocyclopropane-1-carboxylate oxidase (ACO). The activity of ACS and ACO in postharvest peach fruit increases gradually with fruit ripening, thereby promoting ethylene synthesis [22]. Therefore, ethylene production is mainly influenced by regulating the transcription, translation, and protein stability of ACS and AOC [23]. Research shows that the ethylene transcription factors ERF2 and ERF3 in the ethylene signaling pathway can regulate the transcription of ACS [24]. Gu [25] analyzed homeobox (HB) genes using RNA-Seq and qRT-PCR technologies and found that PpHB.G7 in HD-ZIP II participates in peach fruit ripening by affecting the expression of ethylene synthesis genes (PpACS1 and PpACO1). Wu [26] found that combined treatment with 1-Methylcyclopropene (1-MCP) and NO was effective in slowing the respiration rate and inhibiting ethylene production, thereby delaying peach ripening and maintaining fruit quality. Zhu [27] found that MeJA treatment reduced the respiratory rate and ethylene production of peaches during storage.

2.2. Hormone

Hormones can regulate multiple aspects of plant growth and development, and the regulatory role of plant hormones is relatively complex. A specific developmental process requires the coordinated action of multiple different hormones, and the same hormone can also regulate multiple developmental processes [28]. In addition to ethylene, other endogenous plant hormones such as auxin (IAA) and abscisic acid (ABA) also play important roles in regulating fruit ripening and senescence. Among these, auxin was the first plant hormone to be discovered and influences various aspects of plant development and fruit development [29,30]. IAA regulates the expression of target genes by modulating transcription factors (IAAs and ARFs) [31]. Wang [17] found that in peach fruit, the auxin response factor (PpIAA1) can increase the expression of PpACS1, while the ethylene response factor (PpERF4) can bind to the promoters of the PpACO1 and PpIAA1 genes to enhance their transcription. Additionally, the PpIAA1 and PpERF4 complex can elevate the transcriptional levels of abscisic acid biosynthesis genes (PpNCED2 and PpNCED3) and softening genes (PpPG1). Zhou [32] found that IAA treatment upregulated the expression of the IAA biosynthesis gene PpMES and the signaling pathway gene PpSAUR, and downregulated the transcription of the IAA degradation genes PpDAO, PpGH3, and PpIAMT, leading to the accumulation of endogenous IAA in peach fruits. ABA primarily participates in various physiological processes and abiotic stresses such as low temperature [33]. During postharvest storage of peach fruit, ABA content increases before ethylene content, stimulating ethylene production and causing fruit softening [34]. Wang [35] found that ABA can induce the upregulation of ethylene biosynthesis genes and ethylene content in peach fruits during cold storage, thereby causing fruit softening.

2.3. Texture

Fruit softening, as a key process in fruit ripening and postharvest storage, has a significant impact on the quality maintenance of juicy fruits such as peach fruit, tomatoes, kiwifruit, and strawberries. The softening process is influenced by both internal physiological mechanisms (cell wall metabolism, transcriptional regulation, hormone signaling, etc.) and external environmental factors (temperature, humidity, infection, and damage, etc.). This not only leads to a decrease in fruit hardness and deterioration in flavor but also increases the risk of spoilage caused by softening during postharvest storage and transportation, resulting in economic losses [36]. The texture of fruit mainly varies due to changes in pectin content. Pectin forms a gel matrix embedded in microfibrils to constitute the cell wall structure. PME, PG, β-Glu, β-Gal, and Cx are the main cell wall degradation enzymes. They participate in cell wall degradation through enzymatic reactions, leading to softening and a decrease in hardness [37]. Ethylene can independently induce the expression of the PpPG gene and regulate fruit softening. The ethylene response factor (PpERF/ABR1) can activate the promoter of the PpPG gene, promote the expression of PpPG, and cause fruit softening [38,39]. PpERF61 can directly activate maturity-related genes or activate PpERF61-PpSEP1 (transcription activator) to regulate ethylene biosynthesis and texture changes in peach fruit [40]. The upregulation or downregulation of the PpFUL4 gene can directly affect the expression of the PpACO1 gene, thereby controlling ethylene biosynthesis and the softening of peach fruit [41]. Li [42] used VIGS (virus-induced gene silencing) technology to suppress the expression of SEP1 in the SEPALLATA (SEP) gene of MF peach fruit, which significantly reduced the expression levels of softening genes such as PME1, ACS2, EIN2, and Endo-PG3, thereby delaying fruit softening. Rothkegel [43] found that downregulation and methylation of cytopigment 82A (CYP450 82A) and UDP-arabinose 4-epimerase 1 in peach fruit flesh can also regulate fruit softening. Low-temperature blanching reduces pectin esterification and increases pectin cross-linking, giving frozen yellow peaches superior texture and stronger water retention capacity [44]. The PG enzyme genes PpPG1, PpPG21, and PpPG22 are key genes that influence the softening of non-melting flesh (NMF) and melting flesh (MF) peach fruit, respectively. Downregulation of PpPG21 and PpPG22 reduces water-soluble pectin (WSP) content and delays changes in the texture of MF peach fruit [45]. Lu [36] identified that the PpGATA4 transcription factor in peach fruit activates the promoter of the non-enzymatic protein extensin PpEXPA1 and interacts with it to participate in cell wall degradation, resulting in softening of the texture.

2.4. Nutrition

The nutritional value of peach fruit is primarily composed of sugars, amino acids, phenolic compounds, and volatile substances. After harvest, the nutritional content of peach fruit undergoes changes due to respiratory metabolism and fluctuations in hormone levels [18]. Understanding the patterns of change in these key components during storage is crucial for maintaining the optimal flavor and nutritional quality of the fruit.

2.4.1. Sugar

Postharvest sugar metabolism in peach fruit involves multiple metabolic pathways, primarily including sucrose metabolism, hexose metabolism, and sorbitol metabolism. Sugar metabolism is a complex regulatory process involving multiple key enzymes, including sucrose phosphate synthase (SPS), sucrose synthase (SUS), hexokinase (HK), fructokinase (FK), and neutral invertase (NINV) [46]. Unripe peach fruit primarily contain hexoses, while ripe fruits are dominated by sucrose. Sucrose accumulation plays a key role in determining fruit sugar content, and there are significant differences in sucrose content among different varieties. The transcription levels of the six genes SUS4, NINV8, SPS3, SUT2, SUT4, and TMT2 are associated with sucrose accumulation, indicating that sucrose accumulation involves the synergistic action of genes related to sucrose hydrolysis, resynthesis, and transport [47]. During cold storage, the content of sucrose and sorbitol in peach fruit decreases, while the content of fructose and glucose increases. This indicates that sucrose and sorbitol are being converted into hexoses. These hexoses then serve as substrates for energy metabolism, helping the fruit to maintain an energy balance and resist cold stress [46]. Five key functional genes (PpSS, PpINV, PpMGAM, PpFRK, and PpHXK) and eight transcription factors (PpMYB1/3, PpMYB-related1, PpWRKY4, PpbZIP1/2/3, and PpbHLH2) jointly regulate postharvest sugar metabolism and cold tolerance in peach fruit [48]. Liu [49] found that when peaches are stored at 4 °C for two days, their sucrose and glucose content increases, their sorbitol content decreases, and the content of aromatic active compounds such as γ-decalactone increases, which enhances consumers’ perception of sweetness.

2.4.2. Amino Acid

Amino acids are one of the main components of peach fruit and are essential to living organisms. As subunits of proteins, enzymes, and nucleic acids, amino acids play a role in anabolic metabolism, osmotic regulation, defense against stress, and other processes. Their concentration increases during peach fruit development and is an important indicator of quality [50]. During the ripening process of peach fruit, amino acids serve as key precursors for the synthesis of aromatic compounds and can be further metabolized into substances such as alcohols, aldehydes, organic acids, phenols, and lactones. Different amino acids contribute to distinct flavor profiles, and there are significant differences in amino acid concentrations among various peach varieties. Yellow peach fruit have higher total amino acid concentrations than other varieties, resulting in a more appealing aroma after ripening [18]. Sun [50] studied ten peach varieties and concluded that peach fruit mainly contain the amino acids glycine and glutamic acid. They also found that both yellow-fleshed and white-fleshed peach fruit have higher amino acid content than red-fleshed peach fruit, whether the amino acids are considered individually or in total. During the softening process of peach fruit, amino acids accelerate metabolism, while amino acid biosynthesis decreases [51].

2.4.3. Phenolics

Phenolic compounds are secondary metabolites synthesized by plants via various metabolic pathways. They possess antioxidant, antibacterial, melanogenesis-inhibiting, and UV-protective properties, and influence the astringency, bitterness, and aroma of fruits. The primary synthesis pathway is phenylalanine, with the mevalonic acid and malonic acid pathways playing auxiliary roles [18]. Phenolic compounds can be classified into phenolic acids, flavonoids, coumarins, lignans, and flavonoids based on their structure. The main phenolic components in peach fruit are chlorogenic acid, catechin, epicatechin, and rutin, accounting for approximately 70% of the total polyphenol content [18]. Moderate amounts of phenolic compounds can improve the flavor of fruit, but high levels of phenolic compounds (such as proanthocyanidins) can make it taste astringent. Manzoor [52] found that the skin of peach fruit has significantly higher mineral, antioxidant, and phenolic content than the flesh. Unpeeled peach fruit is an excellent source of valuable nutrients, and peach skin could be a good source of natural antioxidants for use in functional foods and nutritional supplements. Phenolic compounds in peach fruit are key antioxidant components, and their content is significantly positively correlated with total antioxidant activity. Their ability to scavenge free radicals and reduce power has been verified through PFRAP, DPPH, and ABTS antioxidant capacity tests [53].

2.4.4. Volatile

Volatile substances significantly impact the aroma quality of fruit. Peach fruit contain approximately 100 volatile compounds, primarily aldehydes, alcohols, terpenes, esters, and lactones. These compounds’ synthetic precursors mainly originate from fatty acid, terpene, and amino acid metabolism [54]. Research shows that there are significant differences in the composition of volatile components between different peach varieties, and that the concentration of volatiles in red- and white-fleshed peach fruit differs during ripening. However, these differences are insufficient to distinguish effectively between flesh types or varieties. Current research has focused primarily on comparisons between different peach varieties and the exploration of peel functional characteristics, with limited attention given to the volatile components of peach flesh. Therefore, the volatile components of peach flesh hold significant scientific research potential [55]. Long-term storage at low temperatures reduces the content of esters, lactones, and terpenoids in the fruit, while causing the accumulation of aldehydes and alcohols. These changes in concentration could potentially be used as biomarkers to assess the extent of low-temperature damage to peach fruit [55]. The aroma of soft peach fruit is more pronounced than that of hard peach fruit, mainly due to differences in volatile compounds such as isopentyl acetate, cis-3-hexenol, pentyl acetate, trans-2-hexenal, dihydro-β-ionone, benzaldehyde acetate, cis-3-hexenyl acetate, and lactones [56].

2.5. Flavor

Flavor characteristics have been demonstrated to be a significant indicator of peach fruit quality, directly influencing market acceptance. The unique flavor characteristics of different peach varieties are primarily determined by the composition and concentration of key biochemical components such as sugars, amino acids, phenolic compounds, and volatile substances [57]. As a typical respiratory-active fruit, peaches undergo rapid senescence postharvest, leading to significant degradation of flavor compounds and a decline in quality [5]. Consequently, the preservation of flavor stability has emerged as a pivotal research priority in the field of postharvest peach conservation. Wang [58] found that storage at 12 °C, a non-chilling temperature, effectively maintained the normal ripening process of peach fruit, prevented CI symptoms, and preserved a favorable flavor balance. Although storage at 4 °C effectively delayed fruit softening and ripening, it potentially led to CI and abnormal flavor changes, particularly an increase in bitterness. Under 12 °C storage conditions, fruit maintained higher sourness and umami taste, while storage at 4 °C preserved higher sweetness levels. Controlled atmosphere (CA) treatment of peach fruits can significantly accumulate volatile compounds derived from fatty acids, such as C6 compounds, three types of esters, and three types of lactones, resulting in high consumer acceptance. The high expression level of the key gene PpAAT1 corresponds to the enrichment trend of fruit aroma esters and lactones under CA treatment [59]. Yang [60] found that treating peach fruits with salicylic acid (SA) could delay the decrease in the content of volatile esters and lactones responsible for fruit aroma by affecting the transcriptional levels of the lipoxygenase PpLOX1, superoxide dismutase PpHPL1, alcohol dehydrogenase PpADH1, and alcohol acyltransferase PpAAT1 genes. 1-methylcyclopropene (1-MCP) can inhibit the release of aroma compounds in peaches during the early stage of room-temperature storage, increase the levels of positive flavor compounds (acetyl linalool and sucrose) during the later stage of storage, and reduce the levels of negative flavor compounds (benzaldehyde and histidine), thereby extending the time required to achieve maximum consumer acceptance from 2 days to 4 days [57]. Cai [61] found that methyl jasmonate (MeJA) upregulates the expression of PpSAMS, PpACS3/4, and PpACO genes in peach fruits, increases ethylene production, and promotes the release of aroma-related esters in peach fruits during room-temperature shelf life.

In summary, postharvest respiration and ethylene in peach fruit interact with each other to accelerate fruit senescence and softening. Sugars provide sweetness and energy, while amino acids contribute to the umami flavor. Together with sugars, they also serve as precursors for volatile compounds. Phenolic compounds constitute flavor components and possess antioxidant properties. Low temperature, CA, SA, 1-MCP, and MeJA treatments are beneficial for maintaining and releasing the aroma of fruits, and enhancing consumer acceptance (Figure 1).

3. Diseases and Control

Diseases are a key factor in postharvest losses of peach fruit, severely limiting their storage life and market value [62]. The primary diseases responsible for postharvest rot in peach fruit are brown rot caused by Monilinia fructicola (M. fructicola), soft rot caused by Rhizopus stolonifer (R. stolonifer), and gray mold caused by Botrytis cinerea (B. cinerea) (

Table 1. Common diseases affecting peach fruits after harvest and treatment measures.

Disease	Postharvest Treatment	Main Findings	Refs.
Brown rot	Plant glycerol combined with Silwet L-77 surfactant treatment	Increases antioxidant enzyme activity and SA content, activating the G3P pathway.	[63]
	Marine yeast (Sporidiobolus pararoseus) and alginate oligosaccharide	Increases the activity and gene expression of catalase, phenylalanine ammonia lyase, chalcone isomerase, and other resistant enzymes.	[64]
	Streptomyces virginiae (XDS1-5)	Destroys the cell membrane structure of M. fructicola.	[65]
	Tea tree oil	Increases fruit antibacterial properties.	[66,67]
	Agaro-oligosaccharides	Increases antioxidant capacity and phenylalanine metabolism.	[68]
	2-decanone	Downregulation of MfBmp1 and MfPls1 expression reduces spore germination and adhesion formation, inhibiting the growth of M. fructicola mycelium.	[69]
Soft rot	Bacillus licheniformis HG03	Increases free radical scavenging capacity, activates MAPK signaling pathways and WRKY transcription factor expression.	[6]
	Carvacrol and eugenol	Increases the activity of defense-related enzymes and improves the content of phenols, flavonoids, lignin, and glycoproteins rich in hydroxyproline.	[70]
	Bacillus cereus AR156	Increases the activity and antioxidant properties of chitinase and β-1,3-glucanase.	[71]
	Thymus vulgaris	Maintains anthocyanin and carbohydrate content.	[72]
Gray mold	Chlorogenic acid	Reduces ergosterol content and synthetic enzyme gene expression, thereby inhibiting the activity of B. cinerea proteins.	[73]
	Natural peptide (Epinecidin-1)	Destroys the B. cinerea structure.	[74]

). These three diseases directly cause fruit rot and spoilage, resulting in significant economic losses. Their infection process may also lead to severe deterioration in fruit quality, such as flavor and texture. This makes them a critical issue in postharvest research and the development of peach preservation technologies.

3.1. Brown Rot

Peach fruit and other stone fruits are susceptible to brown rot caused by M. fructicola during postharvest storage. This is a major economic disease that can cause serious losses to the fruit industry [62]. Zhang [63] found that glycerol treatment increased antioxidant enzyme activity and SA content, while activating the G3P pathway, indicating that multiple mechanisms work together to inhibit the development of brown rot. Combined treatment with marine yeast (Sporidiobolus pararoseus) and alginate oligosaccharide (AOS) enhances the activity and gene expression of stress-resistant enzymes, such as catalase (CAT), phenylalnine ammonialyase (PAL), and chalcone isomerase (CHI). This significantly reduces the incidence of brown rot disease in peach fruit during postharvest storage [64]. Streptomyces virginiae (XDS1-5) can destroy the structure of M. fructicola. Additionally, the indole produced during metabolism can inhibit M. fructicola’s postharvest infection of peach fruit, effectively reducing brown rot disease [65]. Tea tree oil can prevent brown rot caused by M. fructicola from developing, and slows the aging and deterioration of peach fruit during storage [66,67]. Agaro-oligosaccharides increase the resistance of peach fruit to brown rot by boosting antioxidant activity and the expression of enzymes and genes associated with phenylalanine metabolism [68]. Postharvest fumigation with the natural volatile organic compound 2-decanone inhibits the growth of M. fructicola mycelium. It also reduces spore germination and adhesion formation by downregulating the expression of MfBmp1 and MfPls1, thereby reducing the prevalence of brown rot disease [69].

3.2. Soft Rot

Rhizopus stolonifer is the primary pathogen responsible for postharvest diseases in peach fruit. The spores of this fungus are widely distributed in the natural environment and are transmitted by air currents. Once they settle on the fruit’s surface, the spores invade it, growing and multiplying rapidly, which leads to softening and rotting [6]. Treating postharvest peach fruit with Bacillus licheniformis HG03 increases the activity of enzymes associated with resistance to crown gall disease and the capacity to scavenge free radicals. It also reduces the accumulation of membrane lipid peroxidation products, activates the MAPK (mitogen-activated protein kinase) signaling pathway and modulates the expression of genes related to antioxidant activity and various WRKY transcription factors [6]. Steaming peach fruit with carvacrol and eugenol can enhance the activity of defense-related enzymes, and increase the content of phenolic compounds, flavonoids, lignin, and glycoproteins rich in hydroxyproline, thereby reducing the incidence and severity of soft rot disease [70]. Bacillus cereus AR156 can effectively increase the activity of chitinase and β-1,3-glucanase in peach fruit, while enhancing antioxidant activity and inhibiting the incidence of root rot disease [71]. Thyme essential oil (Thymus vulgaris) can inhibit the growth of R. stolonifer on peach fruit, reduce the rate of decay, and maintain anthocyanin and carbohydrate content [72].

3.3. Gray Mold

Postharvest peach fruit are susceptible to infection by B. cinerea during storage, which can lead to gray mold disease in postharvest fruits and vegetables, causing fruit rot [75]. Dai [73] found that treating postharvest peach fruit with 5 g L⁻¹ chlorogenic acid (CGA) downregulated the expression of key enzymes in the ergosterol (a essential sterol for fungal cell membranes) synthesis pathway [sterol C-24 reductase (ERG4) and sterol C-24 methyltransferase (ERG6)], inhibiting the growth of gray mold fungal hyphae and spore production. Additionally, CGA can delay fruit senescence. The natural peptide (Epinecidin-1) extracted from orange-spotted grouper (Epinephelus coioides) can cause ROS accumulation in B. cinerea cells, disrupt cell membranes, leak nucleic acids, and inhibit the occurrence of gray mold disease in peach fruit [74].

In summary, the main methods currently used to control common diseases in peach fruit focus on antagonistic bacteria, plant essential oils, natural polysaccharides, and chemical preservatives. These methods inhibit the spread of pathogens by either disrupting their cellular structure or enhancing antioxidant content, enzyme activity, disease-resistant enzyme activity, and gene expression, thereby strengthening disease resistance.

4. Physical Preservation

Physical postharvest preservation techniques for fruits primarily involve controlling environmental conditions through temperature regulation, gas control and radiation technology. These techniques delay ripening, inhibit microbial growth, and reduce moisture loss, thereby maintaining color, firmness and flavor while extending shelf life (

Table 2. Physical postharvest techniques for peach fruit.

Postharvest Treatment	Main Findings	Ref.
Low-temperature	Storage at 0 °C maintains higher levels of phosphatidylcholine and phosphatidylethanolamine than storage at 4 °C.	[76]
	4 °C delays fruit softening and preserves sweetness, but can cause cold damage and bitterness.	[58]
	4–6 °C is conducive to the accumulation of phenolic substances, while 0–2 °C delays browning.	[77]
	−1 °C improves antioxidant capacity and enhances proline accumulation	[78]
	Inhibition of pectinase gene expression.	[79]
Hot air	Increases antioxidant enzyme activity and reduces reactive oxygen species accumulation and malic acid degradation.	[80]
	Increase the metabolism of phenylpropane and promote the synthesis of anthocyanins and proanthocyanidins.	[81]
Hot water	Activates the transcription of heat shock proteins PpHSPs and PpAPXs to reduce ROS accumulation and alleviate CI.	[82]
	Reduces the expression levels of genes encoding cell wall degradation enzymes and increases the expression levels of phenylalanine ammonia lyase, chalcone isomerase, heat shock protein 7, and reactive oxygen species scavenging genes.	[83]
Modified atmosphere	PpERF61 can activate jasmonic acid and gamma-aminobutyric acid biosynthesis gene expression.	[84]
Controlled atmosphere	Increases the levels of total phenols, total flavonoids, epicatechin, neochlorogenic acid, and chlorogenic acid.	[10]
	Maintains higher energy levels and sucrose content.	[85]
	Increases the accumulation of highly aromatic volatile compounds, raises the double bound index values of fatty acids and sucrose, and enhances flavor.	[59]
UV-B	Reduces cell wall degradation enzyme activity and maintain fruit hardness.	[86]
	Affects the metabolism of biochemical substances such as phenols, terpenoids, lipids, and alkaloids.	[87]
	Increases levels of terpenoids, phenylpropanoids, phytochemicals, and fatty acid metabolites in peach flesh.	[88]
UV-C	Promotes ester and lactone synthesis to enhance fruit aroma.	[89]
	Upregulate genes related to antioxidant and defense responses, while downregulating the expression of genes related to cell wall degradation, membrane lipid oxidation, ethylene synthesis, and oxidative stress.	[90]
	Reduces ethylene production rate and increase sucrose accumulation.	[91]

).

4.1. Low-Temperature Storage

Low-temperature storage is the most common method of storing fruit and vegetables. Peach fruit quickly ripens and deteriorates at room temperature after harvest, but low-temperature storage can effectively delay this process. However, peach fruit is sensitive to the cold and prone to chilling injury (CI) during storage at low temperatures. The main symptoms of CI are browning of the flesh, deterioration of flavor, and the development of off-flavors [4]. Song [76] found that compared with storage at 4 °C, storage at 0 °C was more effective in delaying the onset of CI symptoms in peach fruit. This was related to the enhanced expression of genes associated with lipid metabolism in a low-temperature environment, the slowing of phospholipid degradation and fatty acid desaturation processes, and the maintenance of high levels of phosphatidylcholine (PC) and phosphatidylethanolamine (PE). Liu [77] suggested that for peach fruit intended for short-term storage or immediate consumption, storage at 4–6 °C is beneficial for accumulating phenolic compounds and maintaining high antioxidant activity. Storage at 0–2 °C can delay flesh browning and maintain an appealing appearance, making it more suitable for long-term storage. Storing peach fruit at near-freezing temperatures (−1 °C) can enhance their cold tolerance by regulating proline metabolism and antioxidant defenses [78]. Low-temperature inhibits the expression of the pectin-degrading enzyme genes PpPME3, PpPL2 and PpPG by activating the C-repeat binding factors (CBFs) PpCBF2 and PpCBF3 via the cold signal pathway. This maintains pectin content and fruit firmness [79].

4.2. Heat Treatment

Peach fruit heat treatment is a method of pretreating peach fruit by controlling temperature and time. It is mainly used for preservation, inhibiting enzyme activity, delaying fruit aging, and improving the fruit’s cold resistance and disease resistance. Heat treatment mainly involves hot air (HA) and hot water (HW), the advantage of which is that no chemicals are used. It is often used together with other methods to preserve peach fruit after harvest and can alleviate symptoms of cold damage [9]. Studies have shown that both HA and HW treatments improve the quality of peach fruit stored at low temperatures by enhancing antioxidant capacity and reducing ROS accumulation. However, HW treatment was found to be more effective than HA treatment in alleviating internal browning during storage. Furthermore, HW treatment was found to enhance ascorbate–glutathione (AsA-GSH) metabolism and the expression of antioxidant enzyme genes (PpaSOD5, PpaCAT1, and PpaAPX2) [9]. HA enhances antioxidant enzyme activity, reduces ROS accumulation and malic acid degradation, and lowers CI [80], and also enhances phenylpropanoid metabolic enzyme activity and gene expression to promote anthocyanin and proanthocyanidin synthesis [81]. HW causes the heat shock factor PpHSFA4c gene to interact with its promoter, reducing ROS accumulation by activating the transcription of heat shock proteins PpHSPs and PpAPXs, thereby alleviating CI [82]. Treatment with HW downregulated the expression levels of cell wall degradation enzymes and upregulated the expression of the PAL, CHI, HSP7, APX, CAT, GR, and MNSOD genes [83].

4.3. Controlled Atmosphere Storage

Controlled atmosphere (CA) and modified atmosphere (MA) have been shown to have a positive effect on maintaining the quality of peach fruit during storage [10,84]. Storage treatment using CA (3.5–4% CO₂, 2–3% O₂, 92–95.5% N₂, 1 ± 0.5 °C) increases the content of total phenols, total flavonoids, yellow peach catechins, neochlorogenic acid, and chlorogenic acid. It also enhances the fruit’s free radical scavenging capacity and alleviates browning [10]. Ai [84] studied MA (3% O₂, 0 °C) treatment of peach fruit stored at low temperatures and found that PpERF61 can activate the expression of JA biosynthesis genes Pp13S-LOX, PpAOS, and PpOPR3, as well as the GABA synthesis gene PpGAD, playing an important role in cold tolerance. Storing peach fruit using CA (3–5% O₂, 3–5% CO₂, 1 ± 0.5 °C) inhibited the expression of the V-type proton ATPase subunit protein and induced the expression of pyruvate decarboxylase and sucrose synthase, thereby maintaining a higher energy state and sucrose content and inhibiting fruit browning [85]. Treatment with CA (5% O₂, 10% CO₂, 0 °C) increased the accumulation of volatile compounds derived from fatty acids. The double bond index (DBI) values for fatty acids and sucrose also increased, which alleviated cold damage to the fruit and improved flavor [59].

4.4. UV Treatment

Ultraviolet (UV) radiation is a type of electromagnetic radiation that is invisible to the human eye. It is classified into four categories based on wavelength: vacuum ultraviolet (100–200 nm), short-wave ultraviolet (UV-C, 200–280 nm), medium-wave ultraviolet (UV-B, 280–320 nm), and long-wave ultraviolet (UV-A, 320–390 nm) [11]. Research has shown that UV-B radiation can regulate secondary plant metabolism, triggering the accumulation of nutrients that benefit both plants and humans [92]. UV-C has a positive effect on improving the nutritional value of harvested fruits and vegetables, enhancing disease resistance, inhibiting the reproduction of pathogens, and increasing secondary metabolites to maintain storage quality [93]. Han [11] studied the effects of different doses of UV-C irradiation (0, 0.5, 1.0, 2.0, and 4.0 kJ m⁻²) on peach fruit. The results showed that 2.0 kJ m⁻² best preserved peach fruit quality and enhanced antioxidant capacity. UV-B radiation does not affect soluble solids content and titratable acidity, but it can reduce cell wall degradation enzyme activity and delay fruit hardness decline [86]. Santin [87] found through non-targeted metabolomics research that UV-B treatment led to a reduction in the accumulation of most phenolic compounds within 24 h, but increased the content of anthocyanins, flavonoids, and dihydroflavonols after 36 h, while also reducing the content of carotenoids and most lipids. UV-B treatment for 60 min can effectively increase the content of biochemical substances such as phenols, terpenoids, lipids, and alkaloids after 36 h [88]. UV-C treatment can upregulate enzyme activity and gene expression in the lipoxygenase pathway of peach fruit, thereby promoting ester and lactone synthesis, which increases the content of aroma-related volatiles and unsaturated fatty acid levels [89]. UV-C radiation upregulates genes related to antioxidant and defense responses and downregulates the expression of genes related to cell wall degradation, membrane lipid oxidation, ethylene synthesis, and oxidative stress, affecting the softening and aging of peach fruit [90]. UV-C treatment reduces ethylene production rates, upregulates PpaSS1 gene expression, induces sucrose accumulation, and maintains fruit edible quality [91].

In summary, low-temperature storage of peach fruit plays a crucial role in extending storage life and maintaining fruit quality, but it still faces challenges such as cold damage. In the future, through genetic engineering breeding to enhance the expression of cold-resistant genes in fruits, low-temperature storage will be the most economical, effective, and safe storage method. Heat treatment technology, as an effective method for preservation and processing pretreatment, requires optimization based on specific conditions to achieve the best results. Controlled atmosphere storage is also an effective preservation method, but it requires adjustments and optimizations based on specific varieties and conditions in practical applications. UV primarily improves the storage quality of peach fruit through multiple mechanisms, including inducing enzyme activity and regulating biochemical metabolism.

5. Chemical Preservation

Chemical preservation technology refers to the use of exogenous compounds to influence the metabolism of fruits during transportation and storage, thereby delaying aging or inhibiting microbial growth and maintaining stable quality. Currently, the chemical preservatives most commonly used in the postharvest storage of peach fruit are 1-MCP, NO, and H₂S (

Table 3. Chemical postharvest techniques for peach fruit.

Postharvest Treatment	Main Findings	Ref.
1-MCP	Upregulates epidermal wax crystal formation genes to improve fruit resistance.	[12]
	Reduces sweetness and bitterness, enhances sourness and umami, and lowers CI.	[94]
	Increases proline and polyamine content to enhance cold resistance.	[95]
	Reduces ethylene production and delays the synthesis of volatile substances.	[96]
	Enhances anthocyanin synthase activity and the expression of related genes and transcription factors to improve fruit skin coloration.	[97]
NO	Enhances the antioxidant system and ascorbic acid glutathione cycle.	[13]
	Inhibits cell wall hydrolase activity and related gene expression, upregulates key lipid metabolism gene expression, maintains hardness, and alleviates CI.	[98]
	Increases endogenous NO and gamma-aminobutyric acid content, upregulates key enzymes and gene expression involved in gamma-aminobutyric acid shunting, increases ATP levels and energy charge, and enhances resistance to M. fructicola.	[99]
	Maintains DNA methyltransferase activity and transcription levels, mediates methylation of cold-resistant genes, and enhances cold resistance.	[100]
	By regulating fatty acid metabolism, promotes the synthesis and release of volatile organic compounds, thereby alleviating loss.	[101]
H2S	Inhibits cell wall degradation enzyme activity, increases proline and total phenol content, and alleviates IB.	[14]
	Increasing cellular calcium ion concentration and expression of calmodulin genes PpCaM and PpLCD2, as well as increasing H2S synthesis, enhances cold resistance.	[102]
	Activates the activity and gene expression of sucrose phosphate synthase (SPS) and sucrose synthase (SS-s) to promote sucrose accumulation and enhance the cold tolerance of refrigerated peach fruit.	[103]

).

5.1. 1-MCP

1-Methylcyclopropene (1-MCP) is a widely used ethylene inhibitor. Compared with other postharvest technologies, 1-MCP has several advantages: it is environmentally friendly, highly safe, energy efficient, and highly effective. It can effectively extend the shelf life of fruit and vegetables while maintaining their quality, making it a popular choice for preserving produce [104]. 1-MCP has a significant regulatory effect on quality deterioration symptoms in peach fruit, such as softening, loss of flavor, and postharvest diseases. Many scholars have analyzed its regulatory mechanisms. 1-MCP treatment upregulates the expression of genes involved in the formation of wax crystals on the skin of yellow peach fruit (PpaCER, PpaKCS, PpaKCR1, and PpaCYP86B1), enhancing the fruit’s wax resistance to environmental stress and thereby maintaining postharvest quality [12]. Treatment with 1-MCP can effectively reduce CI, decrease sweetness and bitterness, and increase acidity and umami [94]. Treatment with 1-MCP can stimulate proline and polyamine metabolism in peach fruit, thereby increasing their content and enhancing cold tolerance [95]. 1-MCP delays the formation of volatile compounds responsible for peach aroma by downregulating the expression of PpaLOX1/2/3 and PpaHPL1 and upregulating the expression of PpaLOX5, thereby reducing ethylene biosynthesis and signal transduction genes, lowering production, and delaying the rise in fatty acid levels [96]. Zhang [97] found that treatment with 1-MCP could offset the inhibitory effect of ethylene on the accumulation of total anthocyanins and anthocyanin-3-glucoside, enabling the skin of peach fruit to turn red.

5.2. NO

NO is a key gaseous signaling molecule in plant metabolism that participates in the regulation of physiological processes such as root development, flowering, fruit ripening, and responses to biotic and abiotic stresses. It also plays a role in cellular signaling. Research has shown that short-term treatment at low concentrations can effectively delay the ripening and aging of fruit and vegetables, thereby extending their shelf life after harvest [105,106]. NO enhances the antioxidant capacity of peach fruit by increasing the transcriptional levels and enzymatic activities of the enzyme-mediated antioxidant system and the AsA-GSH cycle in mitochondrial mitochondria, thereby increasing the content of antioxidants (AsA, GSH, GSSG), alleviating oxidative stress, and delaying mitochondrial damage, ultimately extending the storage life of postharvest fruit [13]. NO fumigation treatment upregulates the expression of the sucrose phosphate synthase gene (PpaSPS1/2) in peach fruit to enhance enzyme activity, while simultaneously suppressing the expression level and enzyme activity of the sucrose lyase gene (PpaAI1), thereby maintaining the accumulation of sucrose content within the fruit [106]. Treatment with the NO donor sodium nitroprusside (SNP) maintains fruit firmness by inhibiting cell wall hydrolase activity and related gene expression, while also upregulating the expression of key genes involved in lipid metabolism. This synergistically regulates the cell wall and lipid metabolism networks, thereby reducing the damage caused to peach fruit by low-temperature storage [98]. Jing [99] found that NO treatment increased endogenous NO levels in peach fruit, upregulating the activity and gene expression of key enzymes in the GABA shunt (GAD, GABA-T, SSADH), simultaneously upregulating glutamate receptors (PpGLR) and glutamate dehydrogenase (PpGDH), and driving Ca²⁺ influx and activating the tricarboxylic acid cycle (TCAC), thereby increasing ATP content and energy metabolism efficiency. This synergistically activates the GABA shunt network, enhancing fruit energy supply and disease defense capabilities, ultimately inducing resistance to M. fructicola. NO enhances the cold tolerance of peach fruit by alleviating the decrease in DNA methyltransferase (DNMT) activity and transcript levels, while mediating the methylation of four cold-tolerant genes (PpCBF5-IS2, PpICE1-IS, PpMYC2-IS, PpCOR-IS1) [100]. Treatment with nitric oxide (NO) regulates the metabolism of fatty acids and the expression of PpFADs, PpLOXs, PpHPL, PpADH, PpAATs, and PpACXs. This promotes the synthesis and release of key volatile organic compounds (VOCs), such as C6 aldehydes, C6 alcohols, straight-chain esters, and lactones, in refrigerated peach fruit. This mitigates the loss of VOCs during the transition from low-temperature storage to shelf life [101].

5.3. H₂S

H₂S is a colorless, low-molecular-weight, lipophilic gas signal molecule similar to NO [107]. H₂S is primarily detoxified in plants through L-cysteine desulfurase (LCD) and D-cysteine desulfurase (DCD) in conjunction with sulfite reductase (SIR), O-acetylserine lyase (OAS-TL), and β-cyanoalanine synthase (β-CAS) [14]. H₂S directly reacts with thiol groups (-SH) to form persulfides (-SSH) through its ability to freely penetrate cell membranes, thereby achieving a signal transduction mechanism that does not depend on membrane receptors [14]. H₂S is commonly used to prevent cold damage and delay the ripening and aging processes in harvested fruit and vegetables [108]. H₂S inhibits the activity of cell wall modification enzymes, such as polygalacturonase (PG) and cellulose xylanase (Cx), thereby maintaining the structure of the fruit cell wall. It also enhances total phenolic content and alleviates IB symptoms by promoting proline accumulation and phenylalanine metabolism. This regulatory mechanism may involve controlling anthocyanin synthesis by modifying the Cys192/217 site of the PpMYB75 protein [14]. H₂S inhibits the activity of key enzymes (HK, PGI, PFK, PK) in glycolysis (EMP) and the tricarboxylic acid cycle (TCA), thereby reducing glucose, pyruvate, and NAD(H) levels to slow down respiratory consumption. Simultaneously, it activates the pentose phosphate pathway (PPP) enzymes NADK, G6PDH, 6PGDH, and energy metabolism enzymes (ATPases, SDH, CCO) in the PPP, thereby increasing NADP(H), ATP, and energy charge (EC), and maintaining the structural integrity of peach fruit membranes and reducing CI [21] in peach fruit. Exogenous H₂S increases intracellular Ca²⁺ concentration and calmodulin PpCaM expression, leading to higher PpLCD2 expression and H₂S synthesis, which contributes to the cold tolerance of peach fruit [102]. Treatment with H₂S promotes sucrose accumulation and enhances the cold tolerance of refrigerated peach fruit by inhibiting the activity and gene expression of vacuolar invertase (VIN) and neutral invertase (NI), while activating the activity and gene expression of sucrose phosphate synthase (SPS) and sucrose synthase (SSS) [103].

In summary, 1-MCP inhibits ethylene production and affects auxin and cell wall degradation genes, influencing fruit flavor and color. NO plays a role in multiple pathways, including the antioxidant system, energy metabolism, cell wall metabolism, and lipid metabolism. It inhibits oxidative damage, cold injury, and pathogen infection; maintains cellular structural integrity; delays maturation and senescence; and preserves aromatic components. H₂S influences cell wall metabolism, energy supply, the antioxidant system, ethylene production, and sucrose levels in peach fruit, alleviating fruit softening and oxidative damage.

6. Biological Preservation

Biological preservation technology is an environmentally friendly and safe preservation method that primarily utilizes natural plant extracts or bioactive substances to inhibit fruit decay, delay ripening and aging, and maintain quality [109]. Currently, the main biological materials studied for application on peach fruit include plant hormones, plant essential oils, and natural coating materials (

Table 4. Biological postharvest techniques for peach fruit.

Postharvest Treatment	Main Findings	Ref.
Salicylic acid	Increases antioxidant capacity and raises energy levels.	[4]
	Delays the decline in volatile ester and lactone content and promotes sucrose accumulation.	[60]
	Inhibits the activity of M. fructicola spores and increases the content of chlorogenic acid, anthocyanin-3-glucoside, and anthocyanin-3-rutinoside.	[110]
	Inhibits the activity and gene expression of enzymes related to membrane lipid and cell wall degradation	[37]
Methyl jasmonate	Maintains membrane integrity, increases phospholipid enrichment, and activates the JA signaling pathway.	[15]
	Activates JA biosynthesis, enhances the expression levels of PpCHI, PpGLU, PpPR-like, PpLOX, PpAOS, and PpOPR3, and improves resistance to R. stolonifer.	[111]
	Increases antioxidant enzyme activity and the ascorbic acid glutathione cycle.	[27]
	Increases the transcriptional level of PpNAC1 and PpMYC2.2, which reduces the degree of DNA methylation in fruits during cold storage and shelf life.	[112]
	Maintains fatty acid unsaturation, increases α-linolenic acid accumulation, and promote jasmonic acid and jasmonic acid-isoleucine synthesis.	[113]
Melatonin	Increases the accumulation of polyamines, gamma-aminobutyric acid, and proline.	[114]
	Upregulates PpGAD1 and PpGAD4 expression and downregulates PpGABA-T expression, leading to gamma-aminobutyric acid accumulation.	[115]
	Enhances the activity of methylesterase and demethylase, mediates DNA methylation of browning genes, and increases the content of phenolic substances.	[16]
	Inhibits ethylene production and reduces anthocyanin content.	[116]
	Increases α-linolenic acid metabolism, enhances JA and MeJA accumulation, strengthens glutathione metabolism, and increases the proportion of unsaturated fatty acids.	[117]
Syringa essential oil	Promotes the synthesis of esters and terpenoids while inhibiting the production of aldehydes.	[118]
Rose essential oil	Damages the morphology and structure of M. fructicola, affecting the respiration process and inhibiting the decrease in total phenolic content.	[119]
Trans-cinnamic acid gelatin	Enhances antioxidant activity, inhibits weight loss, and increases total soluble solids.	[120]
Gum arabic	Maintains phenolic compounds and sucrose content, enhances antioxidant activity, and reduces ROS levels.	[121]
Chitosan–chlorogenic acid conjugate	Enhances ROS scavenging capacity and antioxidant activity.	[122]
Rhubarb extract and sodium alginate	Reducing the respiration rate has a significant inhibitory effect on Penicillium expansum.	[123]
1-MCP and Aloe Arborescens	Reduces transpiration and respiration.	[124]

).

6.1. Endogenous Plant Hormones

6.1.1. Salicylic Acid

Salicylic acid (SA) is an endogenous plant hormone that plays a role in regulating multiple developmental stages, from seed germination to fruit ripening. Its functions include delaying fruit ripening and softening, enhancing disease resistance, and maintaining flavor compounds, thereby effectively maintaining the quality and shelf life of fruit and vegetables after harvest [4]. Zhang [4] found that postharvest SA treatment can enhance the antioxidant capacity of peach fruit and promote the AsA-GSH cycle, maintaining higher ATP and EC levels, thereby alleviating softening and reducing cold damage symptoms. Yang [60] used a combination of an electronic nose and electronic tongue with discriminant factor analysis (DFA) to demonstrate that SA treatment can delay the decline in the content of aromatic volatile esters and lactones in refrigerated peach fruit, and regulate the expression of PpLOX1 and promote sucrose accumulation (PpSUS4, PpNINV8, PpTMT2) to regulate the synthesis of volatile compounds and sucrose accumulation, thereby maintaining the flavor quality of peach fruit during cold storage and transition to shelf display. Postharvest SA immersion can effectively inhibit the development of M. fructicola spores, suppress brown rot, and increase the content of phenolic compounds such as chlorogenic acid, anthocyanin-3-glucoside, and anthocyanin-3-rutinoside [110]. Zhang [37] found that SA treatment can inhibit the activity of enzymes that degrade membrane lipids and cell walls, while regulating the expression of related genes.

6.1.2. Jasmonic Acid

Jasmonic acid (JA) and its derivative, methyl jasmonate (MeJA), are important signaling molecules that regulate various physiological processes in the development and maturation of plant fruits, as well as secondary metabolism [125]. Treatment with MeJA inhibits the expression of PpPAL1, PpPPO1, and PpPOD1/2 in order to maintain membrane integrity, while promoting the enrichment of linoleic acid in phospholipid components such as phosphatidylcholine and phosphatidylethanolamine. Furthermore, it activates the JA signaling pathway by upregulating PpMYC2.2 and PpCBF3, while downregulating PpMYC2.1. This synergistic regulation alleviates CI to peach fruit [15]. Ji [111] found that MeJA treatment activated the WRKY transcription factor gene (PpWRKY45) in peach fruit, which in turn activated JA biosynthesis and defense-related enzyme genes, thereby achieving defense against R. stolonifer. Postharvest application of MeJA can reduce ROS accumulation, maintain fruit quality, and enhance antioxidant capacity by promoting antioxidant enzyme activity and the AsA-GSH cycle [27]. Duan [112] found that the peach fruit transcription factors PpNAC1 and PpACS1 are involved in ethylene synthesis: PpExp1 is involved in softening and PpAAT1 is involved in the production of volatile esters and lactones. They also discovered that treatment with methyl jasmonate (MeJA) increased the transcription levels of PpNAC1 and PpMYC2.2, while reducing the degree of DNA methylation in fruits during cold storage and shelf life. Treatment with MeJA maintains fatty acid unsaturation, and activates α-linolenic acid metabolism and promotes its accumulation. This upregulates PpCOI1, PpJAZ, and PpMYC2, activating the JA signaling pathway and driving JA and JA-Ile synthesis. This synergistically enhances membrane stability and cold-resistant metabolic regulation, effectively alleviating CI in peach fruit during cold storage [113].

6.1.3. Melatonin

Melatonin (N-acetyl-5-methoxytryptamine, MT) is a hormone found naturally in both animals and plants. It plays an important role in stress resistance, as well as in plant growth and development. Its functions include reducing postharvest decay, alleviating cold damage, maintaining quality, and extending the shelf life of fruit and vegetables [114,115]. MT and its metabolites can significantly reduce oxidative damage to biomolecules such as lipids, proteins, and DNA by scavenging free radicals [126]. Cao [114] found that MT treatment upregulated the expression of PpADC, PpODC, and PpGAD genes and inhibited PpPDH activity, significantly increasing the accumulation of polyamines, GABA, and proline in refrigerated peach fruit, thereby effectively enhancing fruit cold tolerance and alleviating cold damage. Wu [115] reported similar findings: MT treatment upregulates the expression of PpGAD1 and PpGAD4 while downregulating PpGABA-T expression, leading to γ-aminobutyric acid (GABA) accumulation in yellow peach fruit, which is beneficial for enhancing fruit resistance. MT treatment promotes the accumulation of phenolic compounds by upregulating PpPAL expression and inhibiting the transcription of PpPPO and PpPOD, while activating methyltransferases and demethylases to regulate the DNA methylation levels of related genes, thereby significantly reducing the incidence of browning in refrigerated peach fruit [16]. Wu [116] found that MT treatment inhibited the upstream transcriptional regulation, expression, and downstream metabolite accumulation of anthocyanin synthesis-related genes, reducing the anthocyanin content of peach fruit, and speculated that this was related to the inhibition of ethylene production. MT treatment increases the expression of genes involved in the metabolism of α-linolenic acid (PpLOX, PpAOS, PpAOC, and PpJMT), thereby promoting the accumulation of JA and MeJA. It also enhances glutathione metabolism and increases the proportion of unsaturated fatty acids. This strengthens cell wall stability and improves the cold tolerance of refrigerated peach fruit [117].

6.2. Essential Oils

Essential oils (EOs) are natural bacterial inhibitors that are extracted from various parts of plants, such as flowers, seeds, leaves, bark, and fruits. These aromatic, oily liquids have powerful antibacterial properties. They penetrate cell membranes, disrupt cell structures and inactivate drug-resistant enzymes, thereby exerting their antibacterial effects. In addition, gaseous EOs can inhibit the life cycle of filamentous fungi, including conidial germination, mycelial growth, and spore formation. EOs are an environmentally friendly alternative that can be used for postharvest disease control and preservation of fruit, and have attracted widespread attention in antimicrobial research in recent years [127]. Using microencapsulated Syringa essential oil to treat peach fruit promotes the synthesis of esters and terpenoids while inhibiting the production of aldehydes. This effectively extends the fruit’s shelf life [118]. Rose essential oil (REO) can disrupt the cell morphology and structure of M. fructicola, reduce the activity of its respiratory metabolic enzymes, affect the cellular respiration process, and inhibit the decline in total phenolic content and hardness of peach fruit [119].

6.3. Coating Preservation

Coating preservation is a new type of preservation material that can protect fruits and vegetables physically by blocking the penetration of moisture and gases, thereby reducing moisture evaporation and oxidative damage. Currently, commonly used coating films can be classified into the following categories: polysaccharides (gelatin, starch, gum, alginate, chitosan, cellulose, etc.), proteins (gelatin, egg white, alcohol-soluble protein, whey protein, casein, soy protein, etc.), and lipids (fatty acids, waxes, etc.). Additionally, there are coatings composed of multiple substances or materials [128]. Trans-cinnamic acid gelatin can enhance the antioxidant activity of peach fruit, inhibit weight loss, increase total soluble solids, and delay low-temperature softening [120]. Gan [121] found that gum arabic increases antioxidant activity and reduces reactive oxygen species (ROS) levels by maintaining the content of phenolic compounds and sucrose, thereby improving the cold tolerance of peach fruit. The chitosan–chlorogenic acid conjugate enhances ROS scavenging capacity and antioxidant activity, maintaining fruit firmness [122]. The combination of rhubarb extract and sodium alginate has a significant effect on maintaining the firmness of fruit, slowing the respiration rate, and suppressing the growth of Penicillium expansum [123]. The 1-MCP and Aloe arborescens complex can delay the ripening of peach fruit, maintain their firmness and weight, preserve their sensory quality, and reduce their rate of transpiration and respiration [124].

In summary, SA, JA, and MT can all increase the cold tolerance and antioxidant capacity of peach fruit. As signaling molecules within plants, they are also involved in many physiological activities and metabolic processes. SA and JA are effective against pathogens, while JA and MT can reduce DNA methylation and regulate α-linolenic acid metabolism. All three can slow the aging process in fruits and vegetables, preventing deterioration in quality. EOs extend the shelf life of fruit and reduce rot and quality deterioration by inhibiting microbial growth and regulating physiological metabolism. They are an environmentally friendly and efficient preservation technology. Although experimental research has proven that edible coatings have a significant positive effect on the postharvest preservation of peach fruit, further exploration is needed to transform this technology into economical, efficient, stable, reliable, and compliant industrial processes and products that meet market demand. With more in-depth research into efficient and safe fruit and vegetable preservation methods in the future, it is hoped that consumers will be provided with higher-quality agricultural products.

7. Summary and Prospects

This review provides a comprehensive examination of recent advances in the postharvest physiology of peach fruit (Figure 2), offering an in-depth analysis of respiratory metabolism, ethylene production, hormonal balance, texture evolution, and the dynamic changes in sugars, amino acids, phenolic compounds, and volatile substances that occur during storage after harvest. These key physiological factors collectively influence the quality and value of peach fruit. The review also provides a detailed explanation of the pathogenic mechanisms and control methods for common peach fruit diseases, including brown rot, soft rot, and gray mold. The system evaluated the impact of different preservation technologies on peach quality, including physical technologies (low temperature, heat treatment, controlled atmosphere, and UV), chemical technologies (1-MCP, NO, and H₂S), and biological technologies (endogenous hormones, essential oils, and coatings).

Different preservation technologies each have their own characteristics: (1) Low-temperature storage can effectively extend the storage period, but prolonged use may induce cold damage. Temperatures that are too low may cause frostbite, while temperatures that are too high may exacerbate cold damage, necessitating precise temperature and time control. (2) Heat treatment and irradiation treatment offer stable results, with easily controllable parameters, and are compatible with other reagents. (3) Controlled atmosphere storage helps maintain fruit flavor and reduce cold damage, but it requires significant equipment investment and energy consumption. (4) 1-MCP fumigation takes effect quickly and is suitable for large-scale postharvest treatment; however, it must be applied before the ethylene surge in the fruit, otherwise the effect will decrease, and it may cause abnormal softening of the fruit. (5) NO and H₂S treatment can enhance the antioxidant capacity of the fruit, but high concentrations are toxic to the fruit and humans, so the dosage must be precisely controlled. (6) Endogenous hormones, plant essential oils, and coating technologies demonstrate significant preservation effects, but they are primarily applied via immersion or spraying, and improper application may cause mechanical damage and rot. It should be noted that their safety requires comprehensive assessment, preparation methods need improvement, and most preservatives face constraints such as low solubility and susceptibility to degradation.

With the increasing demand for high-quality fresh fruit among consumers and the expansion of the global agricultural supply chain, innovation and optimization of postharvest preservation technology for peaches has become critical to the sustainable development of the industry. Future research will focus on the following areas:

• Intelligent dynamic monitoring and control: Sensor technology will be deeply integrated into the preservation process, collecting real-time data on temperature, humidity, ethylene concentration, and fruit physiological indicators. Combined with AI predictions of ripeness and disease risk, this will enable automatic optimization of the storage environment. Controlled atmosphere (CA) storage technology will focus on precise control of the O₂/CO₂ ratio to effectively slow down fruit respiration metabolism.
• Synergistic effects of green preservation technologies: The utilization of natural plant hormones, essential oils, and coating technologies will employ nano-microcapsule encapsulation technology to enhance the sustained release performance of active ingredients. This will reduce material volatilization while extending preservation time. The synergistic application of physical and biological preservation technologies will help further reduce the risk of chemical residues.
• Molecular mechanism analysis and development of storage-resistant varieties: The utilization of multi-omics technologies, encompassing transcriptomics and metabolomics, will facilitate an exhaustive examination of the molecular regulatory networks implicated in postharvest softening, browning, and cold damage in peach fruits. The findings of this research will provide a theoretical basis for the development of storage-resistant varieties and the mitigation of cell wall degradation and membrane lipid peroxidation processes.
• The integration of whole-chain preservation technology is a subject that has been the focus of much recent research. The integration of preharvest cultivation management, harvest maturity grading, pretreatment technology, and low-temperature logistics is imperative to establish an integrated preservation technology system encompassing the entire field–storage–transportation–retail process.