Melatonin Treatment Alleviates Chilling Injury of Loquat Fruit via Modulating ROS Metabolism.

Cold storage is one of the most effective methods to maintain postharvest fruit quality. However, loquat fruits are prone to chilling injury (CI) during cold storage, appearing as symptoms such as browning and pitting, which leads to quality deterioration and economic losses. In this study, the effects of melatonin on CI alleviation and the potential role of reactive oxygen species (ROS) metabolism in loquat fruit were investigated. The results showed that 50 µM melatonin was the optimal concentration to inhibit the increase in CI index and cell membrane permeability. Moreover, compared to control fruits, 50 µM melatonin inhibited the malonaldehyde (MDA) content, O2-. production rate and H2O2 content (ROS accumulation) by 17.8%, 7.2% and 11.8%, respectively, during cold storage. Compared to non-treated loquats, 50 µM melatonin maintained higher levels of 1-diphenyl-2-picrylhydrazyl radical-scavenging ability and reducing power, as well as the contents of ascorbic acid (AsA) and glutathione (GSH). Additionally, 50 µM melatonin enhanced the activities of antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) by increasing relevant gene expressions. The activities of SOD, CAT and APX were increased by up to 1.1-, 1.1- and 1.1-times (16 d) by melatonin, as compared with the control fruits. These findings indicate that melatonin mitigation of CI is involved in maintaining cellular redox apphomeostasis in loquat fruit during cold storage.

Preparation and structural characteristics of polysaccharides from loquat peel waste, and their preliminary bioactivities.

BACKGROUND: Loquat peel, often as food waste, is a valuable source of bioactive polysaccharides. However, study of such polysaccharides is insufficient, leaving a significant gap in understanding their preparation, structure and bioactivities. RESULTS: In this study, three types of loquat peel polysaccharides (LPWP, LPHP and LPNP) were sequentially extracted using hot water, HCl and NaOH solutions, respectively. Among them, LPWP was the purest, with a yield of 3.4% and molecular weight of 470.6 kDa, and it differed from LPHP and LPNP in structure, as evidenced by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy, which demonstrated that LPWP consisted of more arabinose (Ara) but less galacturonic acid, rhamnose and galactose, with molar percentages of 71.3%, 23.3%, 3.5% and 1.9%, respectively. Besides, LPWP also exhibited superior antioxidant and antihyperglycemic activities in vitro, particularly in inhibiting α-amylase and α-glucosidase. Methylation and nuclear magnetic resonance analysis confirmed that LPWP was a methyl-esterified pectic polysaccharide rich in branched arabinan, as evidenced by the notable proportion of α-Ara residues, including T-α-Araf, 1,5-α-Araf and 1,2,3,5-α-Araf, with molar percentages of 27.1%, 23.1% and 10.2%, respectively. AFM imaging further revealed its branched-chain morphology and aggregation behavior. CONCLUSION: This study highlights the potential of loquat peel polysaccharides as a bioactive ingredient with significant antioxidant and antihyperglycemic properties, particularly LPWP, which was found as a methyl-esterified pectic polysaccharide with abundant-branched arabinan. Our work provides valuable insights into the application of loquat peel polysaccharides in functional foods. © 2024 Society of Chemical Industry.

Effect of a Mixed Fermented Loquat Leaf Tea By-Product on the Growth Performance and Meat Quality of Tsushima-Jidori Crossbred Chicken.

In the present study, the effects of dietary supplementation with a mixed fermented loquat leaf tea residue (MFL) were evaluated on muscle α-tocopherol concentration and drip loss of Tsushima-Jidori crossbred chicken. MFL contained significantly less ß-carotene, α-tocopherol, and total catechin than that of residues of green tea leaf infusion, although total polyphenol was significantly higher and 1,1-diphenyl-2-picrylhydrazyl radical-scavenging activity tended to be higher, indicating increased antioxidant properties. A total of 120 male Tsushima-Jidori crossbred chickens were divided into two groups at 62 days of age. The control group was fed a basal diet (commercial finisher diet containing 16.5% crude protein and 12.77 MJ/kg metabolizable energy) and the test group was fed a basal diet supplemented with MFL at a concentration of 1.0% until 90 days of age. Body mass, body mass gain, feed intake, and tissue mass did not significantly differ between the two groups. Dietary supplementation with MFL significantly increased breast muscle α-tocopherol concentration and reduced muscle drip loss. This was accompanied by a lower muscle K-value, which indicated the freshness of the meat. These results suggested that dietary supplementation with MFL improved the shelf life and water-holding capacity of breast muscles of Tsushima-Jidori crossbred chickens.

Properties of Guar Gum/Pullulan/Loquat Leaf Extract Green Composite Packaging in Enhancing the Preservation of Chinese Water Chestnut Fresh-Cut Fruit.

Loquat leaf extract (LLE) was added to guar gum and pullulan as an environmentally friendly packaging film (GPE) to preserve Chinese water chestnuts (CWCs). The effect of the amount of LLE on the guar gum/pullulan composite film was investigated. The optimal amount of LLE was 4% (GPE4), with lower water vapor permeability (WVP) and greater mechanical strength, antioxidant, and comparable antibacterial performance than many pullulan-based films. Upon packing the CWCs for 4 days, the weight loss rate of GPE4 was only 1.80 ± 0.05%. For GPE4, the POD activity, the soluble solid content, and the vitamin C (Vc) content of the CWCs were 21.61%, 36.16%, and 26.22% higher than those of the control sample, respectively. More importantly, GPE4 was effective in preserving the quality of CWCs after 4 days of storage, better or at least comparable to non-biodegradable plastic wrapping (PE). Therefore, it can be concluded that GPE films hold significant promise as a sustainable alternative packaging material for preserving fruit-based foods like CWCs, potentially replacing PE in the future.

Isolation and identification of epiphytic Pichia kudriavzevii from loquat peels and investigation of its fermentation characteristics for liquor production.

During the process of fruit wine production, yeast plays a crucial role in influencing the taste, flavor, and overall quality of the wine. This study aims to enhance the flavor and quality of loquat wine by isolating strains of Pichia kudriavzevii (P. kudriavzevii) with desirable winemaking characteristics from loquat fruit fermentation broth. A total of 12 strains of P. kudriavzevii were isolated and subjected to morphological and molecular biological identification. Their fermentation performance, ethanol production, ester production, hydrogen sulfide production, killer activity, and tolerance were evaluated. The results revealed that strains Q-2, Q-9, Q-10, Q-12, Q-20, and Q-42 exhibited robust growth and strong tolerance under conditions of 40 °C temperature, 12% ethanol concentration, 350 g/L glucose concentration, and pH 2.8. Strain Q-42 demonstrated the strongest gas production capacity, killer activity, and good ester and ethanol production. As a highly active fermentation strain with excellent wine making characteristics, P. kudriavzevii Q-42 provides a valuable yeast resource for the industrial production of loquat wine and offers technical support for improving the overall quality of loquat wine.

EjWRKY6 Is Involved in the ABA-Induced Carotenoid Biosynthesis in Loquat Fruit during Ripening.

The yellow-fleshed loquat is abundant in carotenoids, which determine the fruit's color, provide vitamin A, and offer anti-inflammatory and anti-cancer health benefits. In this research, the impact of abscisic acid (ABA), a plant hormone, on carotenoid metabolism and flesh pigmentation in ripening loquat fruits was determined. Results revealed that ABA treatment enhanced the overall content of carotenoids in loquat fruit, including major components like ß-cryptoxanthin, lutein, and ß-carotene, linked to the upregulation of most genes in the carotenoid biosynthesis pathway. Furthermore, a transcription factor, EjWRKY6, whose expression was induced by ABA, was identified and was thought to play a role in ABA-induced carotenoid acceleration. Transient overexpression of EjWRKY6 in Nicotiana benthamiana and stable genetic transformation in Nicotiana tabacum with EjWRKY6 indicated that both carotenoid production and genes related to carotenoid biosynthesis could be upregulated in transgenic plants. A dual-luciferase assay proposed a probable transcriptional control between EjWRKY6 and promoters of genes associated with carotenoid production. To sum up, pre-harvest ABA application could lead to carotenoid biosynthesis in loquat fruit through the EjWRKY6-induced carotenoid biosynthesis pathway.

Hydrogen sulfide attenuates chilling injury in loquat fruit by alleviating oxidative stress and maintaining cell membrane integrity.

The effects of hydrogen sulfide (H2S) on chilling injury (CI), reactive oxygen species (ROS) metabolism, sugar metabolism, pentose phosphate pathway (PPP), and membrane lipid metabolism in loquat fruit throughout the refrigerated period were investigated in this study. The findings indicated that H2S application restrained the increase in internal browning (IB), malondialdehyde (MDA) content, and electrolyte leakage, while sustaining higher total phenolic and total flavonoid levels, and lower soluble quinone content in loquat fruit. Besides, H2S promoted antioxidant accumulation and increased antioxidant enzyme activities by the regulation of ROS metabolism, along with increasing fructose and glucose levels and reducing power by activating sugar metabolism and PPP. Furthermore, H2S treatment retarded the degradation of phospholipids and fatty acids in loquat fruit by modulating membrane lipid metabolism relevant enzyme activities. These findings indicated that H2S application mitigated CI in loquat fruit by alleviating oxidative stress and maintaining cell membrane structural integrity.

Global analysis of gene expression in response to double trisomy loquat (Eriobotrya japonica).

Aneuploidy generally has severe phenotypic consequences. However, the molecular basis for this has been focused on single chromosomal dosage changes. It is not clear how the karyotype of complex aneuploidies affects gene expression. Here, we identified six different double-trisomy loquat strains from Q24 progenies of triploid loquat. The differences and similarities of the transcriptional responses of different double trisomy loquat strains were studied systematically via RNA-seq. The global modulation of gene expression indicated that both cis and trans-effects coordinately regulated gene expression in aneuploid loquat to some extent, and this coordinated regulation was determined by different gene functional groups. Aneuploidy can induce specific transcriptional responses on loquat chromosomes. The differentially expressed genes exhibited regional gene expression dysregulation domains along chromosomes. Furthermore, Aneuploidy could also promote the expression of genes with moderate and high in loquats. Our results provide new insights into the genome-wide transcriptional effects of karyotypes with complex aneuploidies.

Inhibitive Mechanism of Loquat Flower Isolate on Tyrosinase Activity and Melanin Synthesis in Mouse Melanoma B16 Cells.

Melanin naturally exists in organisms and is synthetized by tyrosinase (TYR); however, its over-production may lead to aberrant pigmentation and skin conditions. Loquat (Eriobotrya japonica (Thunb.) Lindl.) flowers contain a variety of bioactive compounds, while studies on their suppressive capabilities against melanin synthesis are limited. Loquat flower isolate product (LFP) was obtained by ethanol extraction and resin purification, and its inhibitory efficiency against TYR activity was investigated by enzyme kinetics and multiple spectroscopy analyses. In addition, the impact of LFP on melanin synthesis-related proteins' expression in mouse melanoma B16 cells was analyzed using Western blotting. HPLC-MS/MS analysis indicated that LFP was composed of 137 compounds, of which 12 compounds, including flavonoids (quercetin, isorhamnoin, p-coumaric acid, etc.) and cinnamic acid and its derivatives, as well as benzene and its derivatives, might have TYR inhibitory activities. LFP inhibited TYR activity in a concentration-dependent manner with its IC50 value being 2.8 mg/mL. The inhibition was an anti-competitive one through altering the enzyme's conformation rather than chelating copper ions at the active center. LFP reduced the expression of TYR, tyrosinase-related protein (TRP) 1, and TRP2 in melanoma B16 cells, hence inhibiting the synthesis of melanin. The research suggested that LFP had the potential to reduce the risks of hyperpigmentation caused by tyrosinase and provided a foundation for the utilization of loquat flower as a natural resource in the development of beauty and aging-related functional products.

The transcription factor EjNAC5 regulates loquat fruit chilling lignification.

Changes in both lignin biosynthesis and DNA methylation have been reported to be associated with chilling stress in plants. When stored at low temperatures, red-fleshed loquat is prone to lignification, with increased lignin content and fruit firmness, which has deleterious effects on taste and eating quality. Here, we found that 5 °C storage mitigated the increasing firmness and lignin content of red-fleshed 'Dahongpao' ('DHP') loquat fruit that occurred during 0 °C storage. EjNAC5 was identified by integrating RNA sequencing with whole-genome bisulfite sequencing analysis of 'DHP' loquat fruit. The transcript levels of EjNAC5 were positively correlated with changes in firmness and negatively correlated with changes in DNA methylation level of a differentially methylated region in the EjNAC5 promoter. In white-fleshed 'Baisha' ('BS') loquat fruit, which do not undergo chilling-induced lignification at 0 °C, the transcripts of EjNAC5 remained low and the methylation level of the differentially methylated region in the EjNAC5 promoter was higher, compared with 'DHP' loquat fruit. Transient overexpression of EjNAC5 in loquat fruit and stable overexpression in Arabidopsis and liverwort led to an increase in lignin content. Furthermore, EjNAC5 interacts with EjERF39 and EjHB1 and activates the transcription of Ej4CL1 and EjPRX12 genes involved in lignin biosynthesis. This regulatory network involves different transcription factors from those involved in the lignification pathway. Our study indicates that EjNAC5 promoter methylation modulates EjNAC5 transcript levels and identifies novel EjNAC5-EjERF39-Ej4CL1 and EjNAC5-EjHB1-EjPRX12 regulatory modules involved in chilling induced-lignification.

Chloroplast genomes of Eriobotrya elliptica and an unknown wild loquat "YN-1".

The chloroplast genomes of wild loquat can help to determine their place in the history of evolution. Here, we sequenced and assembled two novel wild loquat's chloroplast genomes, one is Eriobotrya elliptica, and the other is an unidentified wild loquat, which we named "YN-1". Their sizes are 159,471 bp and 159,399 bp, respectively. We also assembled a cultivated loquat named 'JFZ', its chloroplast genome size is 159,156 bp. A comparative study was conducted with six distinct species of loquats, including five wild loquats and one cultivated loquat. The results showed that both E. elliptica and "YN-1" have 127 genes, one gene more than E. fragrans, which is psbK. Regions trnF-GAA-ndhJ, petG-trnP-UGG, and rpl32-trnL-UAG were found to exhibit high variability. It was discovered that there was a positive selection on rpl22 and rps12. RNA editing analysis found several chilling stress-specific RNA editing sites, especially in rpl2 gene. Phylogenetic analysis results showed that "YN-1" is closely related to E. elliptica, E. obovata and E. henryi.

Effects of Loquat Juice Addition on Sensory Characteristics and Volatile Organic Compounds of Loquat Beer.

Beer, as an ancient and widely consumed alcoholic beverage, holds a rich cultural heritage and history. In recent years, fruit beer has gained significant attention as a distinct beer type produced by incorporating fruit juice into traditional beer ingredients. This study employed headspace solid-phase microextraction-gas chromatography-mass spectrometry techniques, redundancy analysis, and orthogonal projections to latent structures discriminant analysis to analyze the sensory evaluation, physicochemical properties, organic acids, and volatile organic compounds (VOCs) of loquat beer with different proportions of loquat juice. The results shown that the addition of an appropriate amount of loquat juice (40%) enhanced the overall sensory quality of the beer; as the proportion of loquat juice increased, the contents of malic acid and tartaric acid significantly increased (p < 0.05). A total of 100 VOCs were identified, among which 23 key VOCs (VIP > 1, p < 0.05) represented the most important characteristic flavor components in loquat beer based on their odor activity value (OAV). This study holds significant importance for the value-added processing and economic development of loquat.

Loquat (Eriobotrya japonica) Is a New Natural Host of Tomato Mosaic Virus and Citrus Exocortis Viroid.

Loquat leaves exhibiting obvious yellowing, blistering, mosaic, leaf upward cupping, crinkle, and leaf narrowing were identified in Panzhihua City, Sichuan Province, China. High-throughput sequencing (HTS) with the ribo-depleted cDNA library was employed to identify the virome in the loquat samples; only tomato mosaic virus (ToMV) and citrus exocortis viroid (CEVd) were identified in the transcriptome data. The complete genome sequence of ToMV and CEVd were obtained from the loquat leaves. The full-length genome of the ToMV-loquat is 6376 nt and comprises four open reading frames (ORFs) encoding 183 kDa protein, RNA-dependent RNA polymerase (RdRp), movement protein (MP), and coat protein (CP), respectively. A pairwise identity analysis showed that the complete sequence of the ToMV-loquat had a nucleotide identity between 98.5 and 99.3% with other ToMV isolates. A phylogenetic analysis indicated that ToMV-loquat was more closely related to ToMV-IFA9 (GenBank No. ON156781). A CEVd sequence with 361 nt in length was amplified based on the HTS contigs, sequence alignment indicated CEVd-loquat had the highest identity with the strain of CEVd-Balad (GenBank No. PP869624), phylogenetic analysis showed that CEVd-loquat was more closely related to CEVd-lettuce (GenBank No. ON993891). This significant discovery marks the first documentation and characterization of ToMV and CEVd infecting loquat plants, shedding light on potential threats to loquat cultivation and providing insights for disease management strategies.

Genome-wide identification of R2R3-MYB family in Eriobotrya japonica and functional analysis of EjMYB5 involved in proanthocyanidin biosynthesis.

Loquat (Eriobotrya japonica Lindl.) is a popular fruit and medicinal plant. Proanthocyanidins (PAs), as one of the main types of flavonoids, are the key components of loquat fruit quality and medicinal properties. However, the identification of transcription factors (TFs) involved in PA accumulation in loquat remains limited. R2R3-MYB TFs play key regulatory role in PA accumulation in plants. In this study, 190 R2R3-MYB TFs were identified in loquat genome. Combined with transcriptome data, R2R3-MYB TF EjMYB5 involved in PA accumulation in loquat was isolated. EjMYB5 was transcriptional activator localized to nucleus. Expression of EjMYB5 was closely related to PA accumulation in loquat fruits. Heterogenous overexpression of EjMYB5 in tomato (Solanum lycopersicum) inhibited anthocyanin accumulation and promoted PA accumulation. Additionally, transient overexpression of EjMYB5 in tobacco (Nicotiana benthamiana) leaves promoted PA accumulation by upregulating flavonoid biosynthesis genes (NtDFR, NtANS, and NtLAR). Transcriptome analysis of EjMYB5-overexpressing tomato fruits suggested that EjMYB5 was involved in several biological pathways, including lipid metabolism, MAPK signaling, phenylpropanoid biosynthesis, and flavonoid biosynthesis. Collectively, our findings provided basic data for further analysis the function of R2R3-MYB TFs in loquat, and revealed that EjMYB5 functioned as PA accumulation in loquat.

Genome-wide identification and expression analysis of the Eriobotrya japonica TIFY gene family reveals its functional diversity under abiotic stress conditions.

BACKGROUND: Plant-specific TIFY proteins are widely found in terrestrial plants and play important roles in plant adversity responses. Although the genome of loquat at the chromosome level has been published, studies on the TIFY family in loquat are lacking. Therefore, the EjTIFY gene family was bioinformatically analyzed by constructing a phylogenetic tree, chromosomal localization, gene structure, and adversity expression profiling in this study. RESULTS: Twenty-six EjTIFY genes were identified and categorized into four subfamilies (ZML, JAZ, PPD, and TIFY) based on their structural domains. Twenty-four EjTIFY genes were irregularly distributed on 11 of the 17 chromosomes, and the remaining two genes were distributed in fragments. We identified 15 covariate TIFY gene pairs in the loquat genome, 13 of which were involved in large-scale interchromosomal segmental duplication events, and two of which were involved in tandem duplication events. Many abiotic stress cis-elements were widely present in the promoter region. Analysis of the Ka/Ks ratio showed that the paralogous homologs of the EjTIFY family were mainly subjected to purifying selection. Analysis of the RNA-seq data revealed that a total of five differentially expressed genes (DEGs) were expressed in the shoots under gibberellin treatment, whereas only one gene was significantly differentially expressed in the leaves; under both low-temperature and high-temperature stresses, there were significantly differentially expressed genes, and the EjJAZ15 gene was significantly upregulated under both low- and high-temperature stress. RNA-seq and qRT-PCR expression analysis under salt stress conditions revealed that EjJAZ2, EjJAZ4, and EjJAZ9 responded to salt stress in loquat plants, which promoted resistance to salt stress through the JA pathway. The response model of the TIFY genes in the jasmonic acid pathway under salt stress in loquat was systematically summarized. CONCLUSIONS: These results provide a theoretical basis for exploring the characteristics and functions of additional EjTIFY genes in the future. This study also provides a theoretical basis for further research on breeding for salt stress resistance in loquat. RT-qPCR analysis revealed that the expression of one of the three EjTIFY genes increased and the expression of two decreased under salt stress conditions, suggesting that EjTIFY exhibited different expression patterns under salt stress conditions.

Multi-omics analysis provides new insights into the changes of important nutrients and fructose metabolism in loquat bud sport mutant.

Bud sport is a common and stable somatic variation in perennial fruit trees, and often leads to significant modification of fruit traits and affects the breeding value. To investigate the impact of bud sport on the main metabolites in the fruit of white-fleshed loquat, we conducted a multi-omics analysis of loquat fruits at different developmental stages of a white-fleshed bud sport mutant of Dongting loquat (TBW) and its wild type (TBY). The findings from the detection of main fruit quality indices and metabolites suggested that bud sport resulted in a reduction in the accumulation of carotenoids, fructose, titratable acid and terpenoids at the mature stage of TBW, while leading to the accumulation of flavonoids, phenolic acids, amino acids and lipids. The comparably low content of titratable acid further enhances the balanced and pleasent taste profile of TBW. Expression patterns of differentially expressed genes involved in fructose metabolism exhibited a significant increase in the expression level of S6PDH (EVM0006243, EVM0044405) prior to fruit maturation. The comparison of protein sequences and promoter region of S6PDH between TBY and TBW revealed no structural variations that would impact gene function or expression, indicating that transcription factors may be responsible for the rapid up-regulation of S6PDH before maturation. Furthermore, correlation analysis helped to construct a comprehensive regulatory network of fructose metabolism in loquat, including 23 transcription factors, six structural genes, and nine saccharides. Based on the regulatory network and existing studies, it could be inferred that transcription factors such as ERF, NAC, MYB, GRAS, and bZIP may promote fructose accumulation in loquat flesh by positively regulating S6PDH. These findings improve our understanding of the nutritional value and breeding potential of white-fleshed loquat bud sport mutant, as well as serve as a foundation for exploring the genes and transcription factors that regulate fructose metabolism in loquat.

Transcriptome and biochemical analyses reveal phenolic compounds-mediated flavor differences in loquat (Eriobotrya japonica Lindl.) cultivars Chunhua No.1 and Dawuxing.

The novel loquat cultivar 'Chunhua No.1' (CH1) is a promising commercial cultivar. However, CH1 has texture characteristics different from those of common loquat, and its formation mechanism remains unclear. Here, we first identified the phenolic compounds of CH1 and its parent ('Dawuxing', DWX) and the effect on texture formation. The special presence of stone cells explained the flavor differences in CH1. Chlorogenic acid, neochlorogenic acid, and coniferyl alcohol were the main phenolic compounds in loquat, and the high content of coniferyl alcohol was a potential factor for the rough texture of CH1. Transcriptome reveals that phenylpropanoid metabolism was activated during CH1 fruit texture formation. Kyoto Encyclopedia of Genes and Genomes (KEGG) identified 51 structural genes involved in phenylpropanoid biosynthesis, and Weighted Gene Co-expression Network Analysis (WGCNA) identified four structural genes and 88 transcription factors. These findings provide new insights into the phenolic metabolism and flavor formation of loquat fruit.

Methyl jasmonate-loaded composite biofilm sustainably alleviates chilling lignification of loquat fruit during postharvest storage.

In this work, the MeJA-loaded gelatin/pullulan/chitosan composite biofilm was prepared to inhibit the chilling lignification of the loquat fruit during storage at 0 °C. The firmness and lignin content were decreased by 89 % and 81.77 % after MeJA-loaded biofilm treatment. Malondialdehyde (MDA) production was almost completely suppressed and chilling injury of loquat fruit was significantly reduced. Enzyme activity results show that the biofilm alleviated chilling lignification mainly by inhibiting peroxidase (POD) activity in the phenylpropanoid pathway (PCCs = 0.715, with lignin content). Also, the conventional MeJA vapor treatment only alleviated lignification on day 3, but the biofilm treatment had a better and more sustained effect throughout the whole storage due to its sustained release ability. Besides, the biofilm had good mechanical properties, transparency and water vapor transmission rate. This work indicates that loading preservatives into biofilms has a promising application prospect for inhibiting the postharvest quality deterioration of fruit and vegetables.

Evaluation of Loquat Jam Quality at Different Cooking Times Based on Physicochemical Parameters, GC-IMS and Intelligent Senses.

The study compared and analyzed the quality of loquat jam with different cooking times through physicochemical parameters, headspace-gas chromatography-ion migration spectroscopy (HS-GC-IMS) and intelligent senses. The results showed that with the prolongation of the cooking time, the color of loquat jam slowly deepened, the energy significantly increased, the adhesiveness, gumminess, hardness and chewiness enhanced, the free amino acid content increased from 22.40 to 65.18 mg/g. The organic acid content increased from 1.64 to 9.82 mg/g. Forty-seven volatile flavor compounds were identified in five types of loquat jam using HS-GC-IMS, among which the relative content of aldehydes was sharply higher than that of other chemical substances, playing an important role in the flavor formation of loquat jam. LJ0, LJ1 and LJ2 had higher aldehyde content, followed by LJ3 and LJ4 had the lowest aldehyde content. The orthogonal partial least squares-discriminant analysis (OPLS-DA) screened 15 marker compounds that could distinguish five types of loquat jam. The E-nose results showed a significant difference in olfactory sense between loquat jam cooked for 100 and 120 min. The E-tongue results corroborated the results of free amino acids (FAAs) and organic acids, indicating that the gustatory sense of loquat jam changed significantly when the cooking time reached 120 min. The results provided a basis for further research on the relationship between the cooking process and quality characteristics of loquat jam.

Organic acid and sugar components accumulation and flavor associated metabolites dynamic changes in yellow- and white-fleshed seedless loquats (Eriobotrya japonica).

Triploid loquats are divided into yellow- and white-fleshed cultivars. To better understand taste variations in triploid loquat fruits, we used a UPLC-ESI-QTRAP-MS/MS-based widely targeted metabolomic analysis to examine the metabolic composition of two different color fleshed triploid loquats with a sample size of 54 and external validation method within a confidence level of P＜0.05. We identified key flavor-related differentially accumulated metabolites using the variable importance in projection (VIP) value (VIP ≥ 1.0) and fold change ≥ 2 or ≤ 0.5. Furthermore, the results of the HPLC analysis showed that white-fleshed loquats had a low malic acid content. We also performed the UPLC-MS/MS system to investigate the carotenoids contents and lipidome in four triploid cultivars. In the fruits of white-fleshed varieties, the carotenoids contents were significantly downregulated, but the contents of most glycerolphospholipids were increased. Our results reveal the metabolomic changes between the yellow- and white-fleshed cultivars.