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BACKGROUND Hydrogen sulfide (H2 S) is a known signaling molecule in plants, which has the ability to delay fruit ripening. Our previous studies have shown that H2 S treatment could delay the maturation of kiwifruits by inhibiting ethylene production, improving protective enzyme activities, and decreasing the accumulation of reactive oxygen species to protect the cell membrane during storage. The mechanism related to the way in which H2 S affected kiwifruit maturation was still unclear. We performed transcriptome sequencing to explore the influences of H2 S on the softening of kiwifruit. RESULTS The firmness and the soluble solids content (SSC) of the kiwifruit were significantly better maintained with H2 S treatment compared to the control during the storage period (P

This work investigates the role of hydrogen sulfide (H2S) in the browning and regulating the antioxidant defensive system in fresh-cut Chinese water chestnuts. The samples were fumigated with 0, 10, and 15 μl L−1 of H2S and stored at 10°C for 8 days. The results indicated that the H2S treatment significantly inhibited the browning of fresh-cut Chinese water chestnuts, reduced superoxide anion (O2·-) production rate and H2O2 content accumulation, promoted the increase of total phenol content, and enhanced activities of catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX), and glutathione reductase (GR) (P < 0.05). On the other hand, phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), and peroxidase (POD) activities remained at a low level in the H2S treatment (P < 0.05). This result suggested that H2S treatment might be a promising approach to inhibit browning and prolong the shelf life by enhancing oxidation resistance and inhibiting browning enzyme activity of fresh-cut Chinese water chestnuts during storage. Among them, the 15 μl L−1 H2S treatment had the best effect on fresh-cut Chinese water chestnuts.

BACKGROUND The texture and structure of the duck egg white (DEW) gel under salt and heat treatment are crucial to its digestibility. Specifically, the structural changes of food protein gels have been recognized for their potential to regulate in vitro digestion. In this study, the effects of gel characteristics and simulated in vitro gastrointestinal digestion of DEW under combined salt and heat treatment were investigated. RESULTS With the increase in salting time and temperature, a porous opaque gel with large particles was formed, the moisture content of DEW showed a downward trend, and the same was true for hardness changes. The microstructure suggested that, with the penetration of NaCl, DEW proteins were denatured, and the protein molecules gradually unfolded and then aggregated after 7 days. The secondary structure revealed that, as the salting time and temperature increased, the proportion of intermolecular β-sheets and α-helices decreased. In terms of in vitro digestion, the highest digestibility was obtained at 14 days of salting combined with 100 °C heat treatment, and the digestibility was the lowest when marinated for 7 days at 121 °C. Liquid chromatography and tandem mass spectrometry (LC-MS/MS) indicated that the number of different types of peptides and specific peptides was positively correlated with the salting time and temperature of the DEW at the end of gastric digestion. CONCLUSIONS Heat treatment at 100 °C has a higher in vitro digestibility than at 121 °C. Gels with low hardness, large pores, and rough textures are easier to digest by pepsin and release more peptides. © 2021 Society of Chemical Industry.

Current research aimed at studying the effect of benzothiazole (BTH) on the fruit quality and resistance against Penicillium italicum (P. italicum). Recently, a synthetically prepared novel BTH was introduced that elicits the induction of resistance against various diseases of fruits. However, little was reported on the effect of BTH on the disease resistance and fruit quality of postharvest navel orange fruit. In this study, 50 mg·L−1 BTH significantly reduced the decay rate of fruits during 36 days of storage at 20 ± 0.5°C ( P < 0.05 ). BTH markedly inhibited the weight loss rate in fruits ( P < 0.05 ) and effectively maintained higher soluble solid content (SSC), titratable acid (TA), and vitamin C (VC) content compared with control navel orange fruits. Further, BTH significantly suppressed the increase of disease incidence and lesion area of orange fruits challenged with P. italicum ( P < 0.05 ). BTH treatment significantly enhanced antioxidant capacity (DPPH, ABTS radical scavenging activity, and reducing power), and superoxide dismutase (SOD) and peroxidase (POD) activities were significantly increased, while the activity of catalase (CAT) was opposite to the former ( P < 0.05 ). The activities of β-1,3-glucanase (GLU), phenylalanine ammonia-lyase (PAL), and chalcone isomerase (CHT) were significantly higher in BTH-treated navel orange fruits ( P < 0.05 ). Our results suggested that BTH treatment may be a promising treatment for maintaining the quality and inhibiting blue mold of postharvest navel orange in the future.

In this study, we aimed to investigate the changes in gelation behavior of raw (without heating) and cooked (with heating) salted egg yolks during pickling. Results indicated that the decreasing trend in the main peak T22 of raw and cooked salted egg yolks. Cooked salted egg yolks after 28 days of pickling had a higher release of free lipids as visualized using a confocal laser scanning microscope (CLSM). Transmission electron microscope (TEM) micrographs showed that protein granules were distributed together with lipid spheres in raw and cooked salted egg yolks, and the liberated constituents (lipids and proteins) reorganize and aggregate in cooked salted egg yolks after 28 days of pickling. As the pickling proceeded, the soluble protein content and free sulfhydryl content of raw salted egg yolks, the free sulfhydryl content and surface hydrophobicity of cooked salted egg yolks showed an overall increasing trend, followed by significant decrease. The surface hydrophobicity of raw salted egg yolks exhibited an increasing trend. Differential scanning calorimetry (DSC) results demonstrated that salting can stabilize the protein molecules by an increase in denaturation temperatures. Fourier transform infrared spectroscopy (FTIR) revealed that the secondary structures of egg yolk proteins underwent changes, but no difference in protein patterns of either raw or cooked salted egg yolks was observed by SDS–PAGE during pickling. These results suggested that the characteristic gel of salted egg yolks is formed, as the result of multiple interactions between protein molecules and between protein and lipid molecules.

To improve the foaming properties of egg white powder (EWP), the effects of incorporating four different kinds of peptides (soy peptides, corn peptides, whey peptides, and fish skin peptides) were evaluated. The addition of soy peptides (SP) enhanced the foamability, foam stability, and solubility of EWP, whereas whey peptides (WP) significantly reduced the foam stability and solubility. Adding corn peptides (CP) and fish skin peptides (FP) notably improved the foaming properties but had no significant effect on solubility. The addition of SP, WP, and CP markedly reduced zeta potential and surface tension and increased surface hydrophobicity. The rheology data showed that adding SP, CP, and FP significantly increased the elastic modulus of the foam, yet WP notably reduced the elastic modulus. The results obtained by Fourier infrared spectroscopy indicated that the addition of the four kinds of peptides made the secondary structure of egg white protein more flexible. In short, SP, CP, and FP could improve the foaming performance of EWP.

The poor emulsifying property of Ovalbumin (OVA) greatly restricted the overall development of eggs in the food industries. In this paper, we investigated the effects of different xanthan gum (XG) concentrations and different pH value on OVA-stabilized oil-in-water emulsions. From the results of turbidity, ultraviolet absorption spectra and fluorescence spectra, we could find that OVA and XG had an obvious interaction. With increasing XG concentration (0–0.4%), the particle size of OVA-XG complex-stabilized emulsions gradually decreased and absolute value of zeta potential significantly increased. The storage stability of the emulsions was obviously improved by increasing the amount of XG. The apparent viscosity of complex-stabilized emulsions significantly increased, thereby improving the emulsions stability. In addition, our results confirmed emulsions stability largely depended on the pH value. OVA-XG composite emulsion showed a better stability at pH 5.5. Our findings indicated that XG had the potential as an emulsions stabilizer and could be used in egg white-derived foods.

Maillard reaction was progressed by incubating the mixture of egg white (EW) and alkali at different temperatures (4 °C, 25 °C and 37 °C) for different days (0, 1, 3, 5 and 7 days), to explore the effects of temperatures and incubating days on physicochemical and antioxidant properties of EW during the treatment of alkali. The results revealed that the color, browning intensity and fluorescence intensity increased with the extended incubating days (P

Changes in the gelation behavior and mechanism were investigated in low-density lipoprotein (LDL) and high-density lipoprotein (HDL) under the treatment of alkali. Three textural parameters of two kinds of alkali-induced lipoprotein increased, especially the springiness of LDL and the hardness of HDL. Alkaline treatment contributes to the sulfhydryl (SH) oxidation and SH-disulfide bonds (SS) exchange reactions to produce SS, promoting the aggregation of proteins and the formation of lipoprotein gels. For LDL gels, the increased hydrophobic interaction improves its thermal stability. HDL underwent deep unfolding and reassemble to form a network structure with high thermal stability and uniform density. Continuously alkaline treatment destroyed less SS and exposed more buried SH. The decrease of β-structures in both lipoproteins was observed by Fourier Transform Infrared (FTIR). These results suggested that alkali-induced LDL and HDL gelation behavior highly related to the protein structure, SS and hydrophobic interactions.

In this study we investigated the changes in the physicochemical properties, microstructure, protein structure, and intermolecular forces in egg yolk, plasma, and granule gels induced with a strong alkali. The results showed that egg yolks formed a three-dimensional gel, maintained by ionic and disulfide bonds from plasma and granules, respectively. According to spin–spin relaxation time, these gel systems fixed numerous water and lipid protons. Microstructure showed that egg yolks, plasma, and granules liberated their constituents on disruption, which randomly aggregated or bonded. Under a continuous strong alkali treatment, the second-derivative spectra of egg yolks and plasma appeared as an “aggregation band”, while the ordered structure of granules decreased. The results suggested that the aggregation of alkali-induced egg yolks formed mainly due to structural changes in plasma proteins. Granules contributed to the increased hardness and the bonding of egg yolk gels via disulfide bonds induced by alkali treatment.

Changes in physico-chemical properties, microstructure, protein structures and intermolecular force of egg yolk, plasma and granule gels during salting were investigated, using low-field nuclear magnetic resonance (LF-NMR), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and chemical analysis. The results showed that the contents of soluble protein and free sulfhydryl increased and, with D2O treatment, T21 and T22 decreased in egg yolks and plasma salted for 2 d. The particles of egg yolks, plasma and granules in the later stage of salting were disrupted and they liberated their constituents (phospholipids, neutral lipids and proteins), which randomly aggregated. The treatment with NaCl changed the spatial structure of egg yolk proteins. The results suggested that the oil exudation of salted egg yolks was mainly due to structural changes in the low-density lipoproteins. Granules were shown to contribute to the higher hardness and gelation of salted egg yolks.

In order to illuminate the forming process of salted egg, the effects of the brine solution with different salt concentrations on the physicochemical properties, textural properties, and microstructures of duck eggs were evaluated using conventional physicochemical property determination methods. The results showed that the moisture contents of both the raw and cooked egg whites and egg yolks, the springiness of the raw egg yolks and cooked egg whites exhibited a decreasing trend with the increase in the salting time and salt concentration. The salt content, oil exudation and the hardness of the raw egg yolks showed a constantly increasing trend. Viscosity of the raw egg whites showed an overall trend in which it first deceased and then increased and decreased again, which was similar to the trend of the hardness of the cooked egg whites and egg yolks. As the salting proceeded, the pH value of the raw and cooked egg whites declined remarkably and then declined slowly, whereas the pH of the raw and cooked egg yolks did not show any noticeable changes. The effect of salting on the pH value varied significantly with the salt concentration in the brine solution. Scanning electron microscopy (SEM) revealed that salted yolks consist of spherical granules and embedded flattened porosities. It was concluded that the treatment of salt induces solidification of yolk, accompanied with higher oil exudation and the development of a gritty texture. Different salt concentrations show certain differences.