Quantitative proteomic analysis of tomato fruit ripening behavior in response to exogenous abscisic acid.

BACKGROUND: To determine how abscisic acid (ABA) affects tomato fruit ripening at the protein level, mature green cherry tomato fruit were treated with ABA, nordihydroguaiaretic acid (NDGA) or sterile water (control, CK). The proteomes of treated fruit were analyzed and quantified using tandem mass tags (TMTs) at 7 days after treatment, and the gene transcription abundances of differently expressed proteins (DEPs) were validated with quantitative real-time polymerase chain reaction. RESULTS: Postharvest tomato fruit underwent faster color transformation and ripening than the CK when treated with ABA. In total, 6310 proteins were identified among the CK and treatment groups, of which 5359 were quantified. Using a change threshold of 1.2 or 0.83 times, 1081 DEPs were identified. Among them, 127 were upregulated and 127 were downregulated in the ABA versus CK comparison group. According to KEGG and protein-protein interaction network analyses, the ABA-regulated DEPs were primarily concentrated in the photosynthesis system and sugar metabolism pathways, and 102 DEPs associated with phytohormones biosynthesis and signal transduction, pigment synthesis and metabolism, cell wall metabolism, photosynthesis, redox reactions, allergens and defense responses were identified in the ABA versus CK and NDGA versus CK comparison groups. CONCLUSION: ABA affects tomato fruit ripening at the protein level to some extent. The results of this study provided comprehensive insights and data for further research on the regulatory mechanism of ABA in tomato fruit ripening. © 2023 Society of Chemical Industry.

Pickering emulsions synergistically stabilized by sugar beet pectin and montmorillonite exhibit enhanced storage stability and viscoelasticity.

Sugar beet pectin (SBP) is a naturally occurring emulsifying type of pectin fabricated into nanocomposites with montmorillonite (MMT) and then introduced as a stabilizer for high internal phase emulsions (HIPEs). SBP-MMT composites performed well in emulsifying medium-chain triglyceride with an oil volume fraction (φ) of 0.1-0.85 and SBP/MMT mass ratios of 1:0.1-1:0.75. The two representative high internal phase emulsions stabilized by SBP-MMT composites at different SBP/MMT mass ratios exhibited good stability against creaming and coalescence. In these emulsion systems, SBP and MMT formed a network in the continuous phase that markedly improved the rheological properties, including the storage modulus (by 3 orders of magnitude). Confocal light scattering microscopy analysis indicated that a fraction of MMT could work synergistically with SBP in adsorbing on oil droplet surfaces, enhancing stability. SBP-MMT composites stabilized high internal phase emulsions destabilized after the freeze-thaw treatment (-40 °C for 20 h and 25 °C for 4 h) but could be facilely re-emulsified via high-speed shearing. The gastrointestinal digestion behaviors were also modified by stabilizing SBP and MMT. Overall, this work reveals a hitherto undocumented strategy for fabricating highly stable emulsions based on SBP-MMT composites which have huge prospects for application in the food and related industries.

Metabolites of sea cucumber sulfated polysaccharides fermented by Parabacteroides distasonis and their effects on cross-feeding.

Sea cucumber sulfated polysaccharide (SCSPsj) is one of the dietary components which effectively modulates gut microbiota; however, the underlying mechanism remains unclear. In the present study, the interaction between SCSPsj and its utilizer (Parabacteroides distasonis) was investigated. Further study was carried out to explore the cross-feeding between intestinal Bacteroidales mediated by SCSPsj. The results revealed that SCSPsj can be fermented by P. distasonis to produce various microbial metabolites, including organic acids and derivatives, lipids and lipid-like molecules, organoheterocyclic compounds. SCSPsj can regulate the succinate pathway and acetyl-CoA pathway to influence the production of propanoic acid and acetic acid, respectively. Moreover, the SCSPsj-fermented supernatants of P. distasonis can only promote the growth of B. stercoris, B. vulgatus and P. johnsonii among 8 intestinal Bacteroidales strains through cross-feeding. The effect of cross-feeding was related to spatial distances and bacterial species. Moreover, the cross-feeding was correlated with compounds belonging to organic acids and derivatives, lipids and lipid-like molecules. These findings could provide new insights into the interaction between SCSPsj and gut microbiota.

Improving the physicochemical stability of Pickering emulsion stabilized by glycosylated whey protein isolate/cyanidin-3-glucoside to deliver curcumin.

Protein-polysaccharide-polyphenol delivery systems function as a promising tool to deliver bioactive ingredients aiming to improve their solubility and bioavailability. In this study, whey protein isolate (WPI), short-chain inulin (SCI), and cyanidin-3-glucoside (C3G) were first used to stabilize Pickering emulsions. The physicochemical properties and stability of curcumin encapsulated or not in Pickering emulsions were explored. Results showed that glycosylation and C3G reduced surface and interfacial tension on protein surfaces and inhibited the aggregation of emulsion droplets, thereby reducing the emulsion's particle size. WPI-SCI/C3G stabilized Pickering emulsion had the best stability. The CLSM results showed that the WPI-SCI and WPI-SCI/C3G stabilized emulsions were uniformly dispersed, suggesting that glycosylation and the interaction between protein and C3G enhanced the adsorption capacity of the interfacial protein and improved the stability of the Pickering emulsion. The retention rates of curcumin-loaded WPI-SCI- (67.34 %) and WPI-SCI/C3G- (77.07 %) stabilized Pickering emulsions on day 8 of storage were higher than those in WPI- (33.97 %) and WPI/C3G- (37.02 %) stabilized emulsions, and the degradation half-life was also extended from 7 days to >15 days. These findings provide a theoretical basis for the application of WPI Pickering emulsion and indicate a useful means for the delivery of bioactive components.

Understanding of physicochemical properties and antioxidant activity of ovalbumin-sodium alginate composite nanoparticle-encapsulated kaempferol/tannin acid.

In this research, ovalbumin (OVA) and sodium alginate (SA) were used as the materials to prepare an OVA-SA composite carrier, which protected and encapsulated the hydrophobic kaempferol (KAE) and the hydrophilic tannic acid (TA) (OVA-SA, OVA-TA-SA, OVA-KAE-SA, and OVA-TA-KAE-SA). Results showed that the observation of small diffraction peaks in carriers proved the successful encapsulation of KAE/TA. The protein conformation of the composite nanoparticles changed. OVA-TA-SA composite nanoparticles had the highest α-helix content and the fewest random coils, so the protein structure of it had the strongest stability. OVA-TA-KAE-SA composite nanoparticles had the strongest system stability and thermal stability, which might be due to the synergistic effect of the two polyphenols, suggesting the encapsulation of KAE/TA increased the system stability and the thermal stability of OVA-SA composite nanoparticles. Additionally, the composite nanoparticles were endowed with antioxidant ability and antibacterial ability (against Staphylococcus aureus and Escherichia coli) in the order OVA-TA-SA > OVA-TA-KAE-SA > OVA-KAE-SA based on the difference in antibacterial diameter (D, mm) and square (S, mm2), indicating that polyphenols enhanced the antibacterial and antioxidant ability of OVA-SA composite nanoparticles, and the enhancement effect of TA was stronger than that of KAE. These results provide a theoretical basis for the application of OVA-SA composite nanoparticles in the delivery of bioactive compounds.

Influence of polyphenol-metal ion-coated ovalbumin/sodium alginate composite nanoparticles on the encapsulation of kaempferol/tannin acid.

In this research, ovalbumin (OVA) and sodium alginate (SA) were used as the materials to prepare OVA-SA composite carriers, which protected and encapsulated the hydrophobic kaempferol (KAE) and the hydrophilic tannic acid (TA). To achieve the purpose of targeted delivery, the TA-Fe3+ coating film was prepared. Results showed that the observation of small diffraction peaks in carriers proved the formation of TA/Fe3+ coating film on the surface of four composite nanoparticles (pOVA, pOVA-SA, pOVA-KAE-SA, and pOVA-KAE-TA-SA). The protein structure of the composite nanoparticles coated with TA/Fe3+ changed, and the order of the changes was pOVA-KAE > pOVA > pOVA-KAE-SA > pOVA-KAE-TA-SA > pOVA-SA. This phenomenon is due to the fact that the chromophore -C=O and the auxo-chromophore -OH are in the opposite position in the benzene ring of TA, and the two substituents have opposite effects and synergize, resulting in the different degrees of redshift of the composite nanoparticle λmax. Additionally, pOVA-SA had the highest α-helix content and the lowest random coils, conferring the protein structure the strongest stability. The coating of TA/Fe3+ increased the system stability and the thermal stability of the composite nanoparticles. Additionally, the carriers were endowed with antioxidant activity, and their antibacterial ability against Staphylococcus aureus and Escherichia coli was pOVA-KAE-TA-SA > pOVA-KAE-SA > pOVA-KAE > pOVA-SA > pOVA based on the difference in antibacterial diameter (D, mm) and square (S, mm2). pOVA-KAE-TA-SA had the strongest antioxidant activity and antibacterial ability, which improved the bioavailability of TA/KAE. These results provide a theoretical basis for the application of OVA-SA composite nanoparticles in the delivery of bioactive compounds.

Effects of Exogenous Abscisic Acid on Bioactive Components and Antioxidant Capacity of Postharvest Tomato during Ripening.

Abscisic acid (ABA) is a phytohormone which is involved in the regulation of tomato ripening. In this research, the effects of exogenous ABA on the bioactive components and antioxidant capacity of the tomato during postharvest ripening were evaluated. Mature green cherry tomatoes were infiltrated with either ABA (1.0 mM) or deionized water (control) and stored in the dark for 15 days at 20 °C with 90% relative humidity. Fruit colour, firmness, total phenolic and flavonoid contents, phenolic compounds, lycopene, ascorbic acid, enzymatic activities, and antioxidant capacity, as well as the expression of major genes related to phenolic compounds, were periodically monitored. The results revealed that exogenous ABA accelerated the accumulations of total phenolic and flavonoid contents; mostly increased the contents of detected phenolic compounds; enhanced FRAP and DPPH activity; and promoted the activities of PAL, POD, PPO, CAT, and APX during tomato ripening. Meanwhile, the expressions of the major genes (PAL1, C4H, 4CL2, CHS2, F3H, and FLS) involved in the phenylpropanoid pathway were up-regulated (1.13- to 26.95-fold) in the tomato during the first seven days after treatment. These findings indicated that ABA promoted the accumulation of bioactive components and the antioxidant capacity via the regulation of gene expression during tomato ripening.

Isolation and characterization of virulent phages infecting Shewanella baltica and Shewanella putrefaciens, and their application for biopreservation of chilled channel catfish (Ictalurus punctatus).

The growth of Shewanella spp., mainly S. baltica and S. putrefaciens, is responsible for the spoilage of chilled fresh fish. Phages are an alternative tool to control bacterial growth. In this study, virulent phages infecting 4 S. baltica and 6 S. putrefaciens strains were isolated and characterized. Transmission electron microscopy revealed that 6 out of 10 phages (3 phages infecting S. baltica and 3 phages infecting S. putrefaciens) belonged to Myoviridae, while the other 4 phages (1 phage infecting S. baltica and 3 phages infecting S. putrefaciens) belonged to Siphoviridae. Phage SppYZU01 and SppYZU05 showed the broadest host range, being lytic towards all the 4 S. baltica strains and 5 out of the 6 S. putrefaciens strains, respectively. The genome sequence of SppYZU01 had no similarity with known genome sequences, while that of SppYZU05 was 88.5% similar to the genome of a virulent S. putrefaciens-infecting phage (Spp001). According to the host range and lytic activity, 3 phages, including SppYZU01, SppYZU05, and SppYZU06, were combined into a cocktail (designated as SPMIX3-156). SPMIX3-156 showed potential as an antimicrobial agent to control S. baltica and S. putrefaciens strain growth in catfish matrices. Bacterial growth in the catfish muscle juice inoculated with 104 colony-forming units (CFU)/mL of Shewanella strains was partially inhibited by 105 plaque-forming units (PFU)/mL of SPMIX3-156 at both 25 °C and 4 °C. The catfish fillets inoculated with Shewanella strains were used as a model to evaluate the biopreservative effects of SPMIX3-156. Total viable counts of fillet samples treated with 107 PFU/mL of SPMIX3-156 were reduced by 3.21 and 2.75 log units after 1 day at 25 °C and 10 day at 4 °C, respectively, compared to those of untreated samples. Fillet quality indices, including pH, total volatile basic nitrogen, and sensory value of the SPMIX3-156-treated samples, considerably improved compared to those of the control samples at both 4 °C and 25 °C. Our results suggest that SPMIX3-156 is a promising biological agent against S. baltica and S. putrefaciens, and may have a potential use in chilled fish fillet biopreservation.

Contribution of abscisic acid to aromatic volatiles in cherry tomato (Solanum lycopersicum L.) fruit during postharvest ripening.

Fruit aroma development depends on ripening. Abscisic acid (ABA) has been reported to be involved in the regulation of tomato fruit ripening. In the present study, the effects of exogenous ABA on aromatic volatiles in tomato fruit during postharvest ripening were studied. The results showed that exogenous ABA accelerated color development and ethylene production as well as the accumulation of carotenoids, total phenolics and linoleic acid in tomato fruit during ripening. Moreover, exogenous ABA increased the accumulation of volatile compounds such as 1-peten-3-one (2.06-fold), ß-damascenone (1.64-fold), benzaldehyde (3.29-fold) and benzyl cyanide (4.15-fold); induced the expression of key genes implicated in the biosynthesis pathways of aromatic volatiles, including TomloxC, HPL, ADH2, LeCCD1B and SlBCAT1 (the values of the log2 fold changes ranged from -3.02 to 2.97); and promoted the activities of lipoxygenase (LOX), hydroperoxide lyase (HPL) and alcohol dehydrogenase (ADH). In addition, the results of promoter analyses revealed that cis-acting elements involved in ABA responsiveness (ABREs) exist in 8 of the 12 key genes involved in volatile biosynthesis, suggesting that ABA potentially affects aromatic volatile emissions via the regulation of gene expression profiles.

Hyperspectral Imaging for Predicting the Internal Quality of Kiwifruits Based on Variable Selection Algorithms and Chemometric Models.

We investigated the feasibility and potentiality of determining firmness, soluble solids content (SSC), and pH in kiwifruits using hyperspectral imaging, combined with variable selection methods and calibration models. The images were acquired by a push-broom hyperspectral reflectance imaging system covering two spectral ranges. Weighted regression coefficients (BW), successive projections algorithm (SPA) and genetic algorithm-partial least square (GAPLS) were compared and evaluated for the selection of effective wavelengths. Moreover, multiple linear regression (MLR), partial least squares regression and least squares support vector machine (LS-SVM) were developed to predict quality attributes quantitatively using effective wavelengths. The established models, particularly SPA-MLR, SPA-LS-SVM and GAPLS-LS-SVM, performed well. The SPA-MLR models for firmness (R pre = 0.9812, RPD = 5.17) and SSC (R pre = 0.9523, RPD = 3.26) at 380-1023 nm showed excellent performance, whereas GAPLS-LS-SVM was the optimal model at 874-1734 nm for predicting pH (R pre = 0.9070, RPD = 2.60). Image processing algorithms were developed to transfer the predictive model in every pixel to generate prediction maps that visualize the spatial distribution of firmness and SSC. Hence, the results clearly demonstrated that hyperspectral imaging has the potential as a fast and non-invasive method to predict the quality attributes of kiwifruits.

Comprehensive RNA-Seq Analysis on the Regulation of Tomato Ripening by Exogenous Auxin.

Auxin has been shown to modulate the fruit ripening process. However, the molecular mechanisms underlying auxin regulation of fruit ripening are still not clear. Illumina RNA sequencing was performed on mature green cherry tomato fruit 1 and 7 days after auxin treatment, with untreated fruit as a control. The results showed that exogenous auxin maintained system 1 ethylene synthesis and delayed the onset of system 2 ethylene synthesis and the ripening process. At the molecular level, genes associated with stress resistance were significantly up-regulated, but genes related to carotenoid metabolism, cell degradation and energy metabolism were strongly down-regulated by exogenous auxin. Furthermore, genes encoding DNA demethylases were inhibited by auxin, whereas genes encoding cytosine-5 DNA methyltransferases were induced, which contributed to the maintenance of high methylation levels in the nucleus and thus inhibited the ripening process. Additionally, exogenous auxin altered the expression patterns of ethylene and auxin signaling-related genes that were induced or repressed in the normal ripening process, suggesting significant crosstalk between these two hormones during tomato ripening. The present work is the first comprehensive transcriptome analysis of auxin-treated tomato fruit during ripening. Our results provide comprehensive insights into the effects of auxin on the tomato ripening process and the mechanism of crosstalk between auxin and ethylene.