Using ultrasonic-assisted sodium bicarbonate treatment to improve the gel and rheological properties of reduced-salt pork myofibrillar protein.

To study the impact of ultrasonic duration (0, 30, and 60 min) and sodium bicarbonate concentration (0% and 0.2%) on the gel properties of reduced-salt pork myofibrillar protein, the changes in cooking yield, colour, water retention, texture properties, and dynamic rheology were investigated. The findings revealed that added sodium bicarbonate significantly increased (P < 0.05) cooking yield, hardness, springiness, and strength of myofibrillar protein while reducing centrifugal loss. Furthermore, the incorporation of sodium bicarbonate led to a significant decrease in L⁎, a⁎, b⁎, and white values of cooked myofibrillar protein; these effects were further amplified with increasing ultrasonic duration (P < 0.05). Additionally, storage modulus (G') significantly increased for myofibrillar protein treated with ultrasonic-assisted sodium bicarbonate treatment resulting in a more compact gel structure post-cooking. In summary, the results demonstrated that ultrasonic-assisted sodium bicarbonate treatment could enhance the tightness of reduced-salt myofibrillar protein gel structure while improving the water retention and texture properties.

Natural polysaccharides protect against diet-induced obesity by improving lipid metabolism and regulating the immune system.

Unhealthy dietary patterns-induced obesity and obesity-related complications pose a great threat to human health all over the world. Accumulating evidence suggests that the pathophysiology of obesity and obesity-associated metabolic disorders is closely associated with dysregulation of lipid and energy metabolism, and metabolic inflammation. In this review, three potential anti-obesity mechanisms of natural polysaccharides are introduced. Firstly, natural polysaccharides protect against diet-induced obesity directly by improving lipid and cholesterol metabolism. Since the immunity also affects lipid and energy metabolism, natural polysaccharides improve lipid and energy metabolism by regulating host immunity. Moreover, diet-induced mitochondrial dysfunction, prolonged endoplasmic reticulum stress, defective autophagy and microbial dysbiosis can disrupt lipid and/or energy metabolism in a direct and/or inflammation-induced manner. Therefore, natural polysaccharides also improve lipid and energy metabolism and suppress inflammation by alleviating mitochondrial dysfunction and endoplasmic reticulum stress, promoting autophagy and regulating gut microbiota composition. Specifically, this review comprehensively summarizes underlying anti-obesity mechanisms of natural polysaccharides and provides a theoretical basis for the development of functional foods. For the first time, this review elucidates anti-obesity mechanisms of natural polysaccharides from the perspectives of their hypolipidemic, energy-regulating and immune-regulating mechanisms.

Antibacterial Effects of Theaflavins against Staphylococcus aureus and Salmonella paratyphi B: Role of Environmental Factors and Food Matrices.

This study aimed to investigate the effects of different environmental factors (temperature, pH, and NaCl) and food matrices (skimmed milk powder, lecithin, and sucrose) on the antibacterial activity of theaflavins (TFs) against Staphylococcus aureus (S. aureus) and Salmonella paratyphi B (S. paratyphi B). TFs showed a larger diameter of inhibition zone (DIZ, 12.58 ± 0.09 mm-16.36 ± 0.12 mm) value against S. aureus than that of S. paratyphi B (12.42 ± 0.43 mm-15.81 ± 0.24 mm) at the same concentration (2-10 mg/mL). When temperatures were 25-121 °C, the DIZ of TFs against both S. aureus and S. paratyphi B was not significantly different. As pH increased from 2 to 10, their DIZ values decreased significantly from 16.78 ± 0.23 mm to 13.43 ± 0.08 mm and 15.63 ± 0.42 mm to 12.18 ± 0.14 mm, respectively. Their DIZ values increased slightly as the NaCl concentration increased from 0.2 mol/L to 0.8 mol/L, while their DIZ values decreased significantly for skimmed milk powder concentrations in the range of 20-120 g/L. Regarding the concentrations of lecithin and sucrose were 2-12 g/L and 10-60 g/L, their DIZ values showed no significant change against S. paratyphi B, but an increased trend for S. aureus. Under the above different environmental factors and food matrices, TFs maintained excellent antibacterial activity against S. aureus and S. paratyphi B, providing a theoretical guidance for applying TFs as novel antibacterial additives in the food industry.

Effect of High-Intensity Ultrasound Pretreatment on the Properties of the Transglutaminase (TGase)-Induced ß-Conglycinin (7S) Gel.

In this study, we investigated the effects of different high-intensity ultrasound (HIU) pretreatment times (0-60 min) on the structure of ß-conglycinin (7S) and the structural and functional properties of 7S gels induced by transglutaminase (TGase). Analysis of 7S conformation revealed that 30 min HIU pretreatment significantly induced the unfolding of the 7S structure, with the smallest particle size (97.59 nm), the highest surface hydrophobicity (51.42), and the lowering and raising of the content of the α-helix and ß-sheet, respectively. Gel solubility showed that HIU facilitated the formation of ε-(γ-glutamyl)lysine isopeptide bonds, which maintain the stability and integrity of the gel network. The SEM revealed that the three-dimensional network structure of the gel at 30 min exhibited filamentous and homogeneous properties. Among them, the gel strength and water-holding capacity were approximately 1.54 and 1.23 times higher than those of the untreated 7S gels, respectively. The 7S gel obtained the highest thermal denaturation temperature (89.39 °C), G', and G″, and the lowest tan δ. Correlation analysis demonstrated that the gel functional properties were negatively correlated with particle size and the α-helix, while positively with Ho and ß-sheet. By contrast, gels without sonication or with excessive pretreatment showed a large pore size and inhomogeneous gel network, and poor properties. These results will provide a theoretical basis for the optimization of HIU pretreatment conditions during TGase-induced 7S gel formation, to improve gelling properties.

Microbial characteristics and metabolite profiles of high-temperature Daqu in different maturation stages.

The maturation period of high-temperature Daqu (HTD) is usually 3-6 months, and the characteristics of HTD at different maturation stages were different. In this study, the microbial characteristics and metabolite profiles of HTD at different maturation stages were revealed with the combination of physicochemical detection, the third generation Pacific Biosciences (PacBio) single-molecule, real-time (SMRT) sequencing technology, gas chromatography-mass spectrometry (GC-MS), and gas chromatography-ion mobility spectrometry (GC-IMS). Results showed that HTD matured for 6 months (Mix_m6) had higher saccharification power but less culturable thermotolerant bacteria and fungi than HTD matured for 3 months (Mix_m3). The average relative abundances of Thermoactinomyces, Paenibacillus, and Rasamsonia in Mix_m3 were higher than that in Mix_m6, while the average relative abundances of Bacillus, Pseudomonas, Thermoascus increased obviously with the prolongation of the maturation period. Streptomyces and Thermoactinomyces were biomarkers in Mix_m3, while Burkholderia and Pseudomonas were regarded as biomarkers in Mix_m6. Differences in microbiota structure led to different enrichment of metabolic pathways in HTD at different maturation stages, resulting in different flavor profiles, especially in ethyl acetate, 1-octen-3-one, (E)-3-Hexen-1, 2,3,5-trimethy-6-ethylpyrazine, pyrazine, tetramethyl content. The microbiota and metabolite characteristics of HTD comprehensively reflected the HTD quality in different maturation stages, which provided a reference for determining the optimal maturation time.

Multidimensional profiling indicates the shifts and functionality of wheat-origin microbiota during high-temperature Daqu incubation.

Wheat-origin microbiota is a critical factor in the assembly of the microbial community during high-temperature Daqu incubation. However, the succession and functional mechanisms of these microbial communities in Daqu are still unclear. This study investigated the shifts in microbiota diversity from the wheat to the end of incubation by the third generation Pacific Biosciences (PacBio) single-molecule, real-time (SMRT) sequencing technology. Results indicated that Staphylococcus, Pantoea, Alternaria, and Mycosphaerella were the dominant genera of wheat-origin microbiota while Bacillus and Thermoascus were the most predominant bacterial and fungal genera of Daqu microbiota, respectively. Metabolite detection revealed that volatile organic compounds (VOCs) changed obviously in different incubation stages and the 7th day to the 15th day of incubation was the critical period for the formation of VOCs. The content of non-VOCs, especially sugars, increased steeply in the first four days of incubation. The network analysis between microbes and metabolites showed that Thermoactinomyces and Staphylococcus had opposite correlations with most non-VOCs. Alternaria and Mycosphaerella had strong positive correlations with fructose. As key functional fungal genera in wheat-origin microbiota, Mycosphaerella, Aspergillus, and Alternaria participated in multiple metabolic pathways (gluconeogenesis I, sucrose degradation III, pentose phosphate pathway, 5-aminoimidazole ribonucleotide biosynthesis I, methyl ketone biosynthesis, and GDP-mannose biosynthesis) at the early stage of incubation, which played an important role in the formation of flavors and succession of microbiota. This work highlighted the shifts and functionality of wheat-origin microbiota in Daqu incubation, which can be a guideline to stabilize Daqu quality by wheat-origin microbiota control.

Comparative study on inhibitory effects of ferulic acid and p-coumaric acid on Salmonella Enteritidis biofilm formation.

Biofilm cells exhibit higher resistance than their planktonic counterparts to commonly used disinfectants in food industry. Phenolic acids are promising substitute offering less selective pressure than traditional antibiotics. This study aims to evaluate the inhibitory effects of ferulic acid (FA) and p-coumaric acid (p-CA) on Salmonella Enteritidis biofilm formation and explore the underlying inhibitory mechanisms. The minimal inhibitory concentration (MIC) of FA and p-CA were 1.0 and 0.5 mg/ml, respectively. The sub-inhibitory concentration (1/8 MIC) significantly decreased biofilm formation without growth inhibitory effects. The biomass and extracellular polymeric substances (EPS) of S. Enteritidis biofilm as well as the bacterial swimming and chemotaxis abilities were significantly decreased when exposed to sub-MIC concentrations of FA and p-CA. These two phenolic acids showed high affinity to proteins involved in flagella motility and repressed the S. Enteritidis biofilm formation-related gene expressions. Furthermore, these two phenolic acids maintained high antibiofilm efficiency in simulated food processing conditions. This study provided valuable information of multiple phenotypic and molecular responses of S. Enteritidis to these two phenolic acids.

Characterization and comparison of the bacterial community on environmental surfaces through a fresh-cut vegetables processing line in China.

Zoning is typically adopted by food manufacturers and classified into three different zones including Zone 1 (food contact surface), Zone 2 (proximity to food and food contact surfaces) and Zone 3 (remote surfaces from processing). In this study, environmental surfaces belonging to these three zones were sampled during food processing in a fresh-cut vegetables (FVs) processing facility located in Beijing, China. Bacterial loads in terms of aerobic plate count and coliform count were evaluated by culture-dependent techniques. The profile and diversity of bacterial community in these three zones were investigated by high-throughput sequencing. Zone 1 showed similar microbiota and predominated by Pseudomonas and Acinetobacter, while the predominant genera on Zone 2 or 3 were quite varied among different processing steps. The SourceTracker analysis showed that most of the bacteria (above 80%) on surfaces were from unknown sources, while sorting and disinfection & cleaning steps contributed equally to the bacterial community of cutting areas. Microbial association network analysis revealed strong positive interactions of Comamonas and Janthinobacterium with Myroides and Serratia, respectively, whereas Pseudomonas showed no significant correlation with other genera. The function of microbial communities was predicted based on BugBase 16S rRNA database, and the results indicated that the proportions of potential biofilm-forming bacteria were above 70% in all samples, and species of Pseudomonas, Comamonas, Chryseobacterium and Janthinobacterium were opportunistic pathogens or spoilage bacteria. This study evaluated the bacteria risks including bacterial load, composition, as well as potential bacterial interaction, function and microbial transfer on food processing surfaces, which will facilitate our better understanding on the cross-contaminations and preventions of harmful microorganism in FVs processing industry.

Occurrence of disinfectant-resistant bacteria in a fresh-cut vegetables processing facility and their role in protecting Salmonella enteritidis.

Chemical disinfectants are widely used to control foodborne pathogen contamination in fresh-cut vegetables (FVs) processing facilities. In this study, we investigated the disinfectant-resistant bacteria in a FVs processing facility and evaluate the effects of these bacteria on Salmonella enteritidis biofilm formation and disinfectant resistance. The disinfectant-resistance profiles were determined using 0.02% sodium hypochlorite (NaClO), 0.2% benzalkonium bromide (BAB) and 2% hydrogen peroxide (H2O2) solutions. The results showed the high occurrence of disinfectant resistant bacteria in the FVs processing environment, especially in the clean area. All isolates showed planktonic susceptibility to H2O2 and BAB, while the Gram-positive isolates were specifically resistant to NaClO. Isolates with biofilm-forming ability showed resistance to tested disinfectants. Disinfectant resistance of S. enteritidis was not significantly enhanced in most of the mixed-species biofilms, except for Bacillus paramycoides B5 which not only increased the biomass but also enhanced the survival ability of the Salmonella under NaClO treatment. Increased biomass and compact biofilm structures were observed in mixed-species biofilms by scanning electron microscopy (SEM). This study provides new insights into the disinfectant-resistant bacteria from food processing facilities and highlights their relevance for foodborne pathogen contamination.

The role of osmoregulated periplasmic glucans in the biofilm antibiotic resistance of Yersinia enterocolitica.

The formation of biofilms by bacteria is of great significance because it involves many physiological changes that serve to protect the cells from various stresses. One of the best-known biofilm-specific properties of bacteria is that bacteria that grow in biofilms are generally more resistant to antibiotics than their planktonic counterparts. In a previous study, osmoregulated periplasmic glucans (OPGs), catalyzed by the opgGH operon, were identified and found to function in Rcs signalling in Yersinia enterocolitica. In this study, the possible contribution of OPGs to antimicrobial resistance of Y. enterocolitica biofilms were investigated, and the results showed that OPGs, especially when overexpressed, conferred a high level of biofilm resistance to two different classes of antibiotics onto Y. enterocolitica. Subsequent analysis revealed that OPGs regulated the biofilm architecture in Y. enterocolitica by promoting the bacteria to form large cell aggregates. Moreover, the opgGH genes in biofilms showed higher expression than in planktonic cultures. OPGs were required to induce the expression of genes related to flagella, extracellular polysaccharide, and c-di-GMP biosynthesis in Y. enterocolitica biofilms and this effect was more significant when OPGs were overproduced. The current investigation showed an extension in the biological role of OPGs in Y. enterocolitica and provided a strong theoretical basis to further study this resistance mechanism at the molecular level to identify new drug targets or disinfectants for the treatment of infections caused by Y. enterocolitica within biofilms.

An aptasensor for staphylococcus aureus based on nicking enzyme amplification reaction and rolling circle amplification.

An ultra-sensitive aptamer-based biosensor for the detection of staphylococcus aureus was established by adopting the nicking enzyme amplification reaction (NEAR) and the rolling circle amplification (RCA) technologies. Aptamer-probe (AP), containing an aptamer and a probe sequence, was developed to act as the recognition unit of the biosensor, which was specifically bound to S. aureus. The probe was released from AP and initiated into the subsequent DNA amplification reactions where S. aureus was present, converting the detection of S. aureus to the investigation of probe oligonucleotide. The RCA amplification products contained a G-quadruplex motif and formed a three dimensional structure in presence of hemin. The G4/hemin complex showed horseradish peroxidase (HRP)-mimic activity and catalyzed the chemiluminescence reaction of luminol mediated by H2O2. The results showed that the established biosensor could detect S. aureus specifically with a good linear correlation at 5-104 CFU/mL. The signal values based on NEAR-RCA two-step cycle were boosted acutely, much higher than that relied on one-cycle magnification. The limit of detection (LoD) was determined to be as low as 5 CFU/mL. The established aptasensor exhibited a good discrimination of living against dead S. aureus, and can be applied to detect S. aureus in the food industry.

Isolation, characterization and antimicrobial activities of polyacetylene glycosides from Coreopsis tinctoria Nutt.

Polyacetylene glycosides, (6Z, 12E)-tetradecadiene-8,10-diyne-1-ol-3(R)-O-ß-D-glucopyranoside (trivially named coreoside E) and (6Z, 12E)-tetradecadiene-8,10-diyne-1-ol-3(R)-O-ß-L-arabinopyranosyl-(1 â†’ 2)-ß-D-glucopyranoside (trivially named coreoside F), were isolated from buds of Coreopsis tinctoria Nutt., together with one known compound, coreoside B. Their chemical structures were elucidated by extensive spectroscopic analysis and on the basis of their chemical reactivities. Coreoside E exhibited high levels of antimicrobial activity against Staphylococcus aureus and Bacillus anthracis with minimum inhibitory concentrations of 27 ± 0.27 and 18 ± 0.40 µM, respectively, whereas coreoside F and coreoside B showed weak antimicrobial activity against S. aureus and B. anthracis.

Comparative effects of hawthorn (Crataegus pinnatifida Bunge) pectin and pectin hydrolyzates on the cholesterol homeostasis of hamsters fed high-cholesterol diets.

This study aims to compare the effects of feeding haw pectin (HP), haw pectin hydrolyzates (HPH), and haw pectin pentasaccharide (HPPS) on the cholesterol metabolism of hypercholesterolemic hamsters induced by high-cholesterol diets. The animals were fed a standard diet (SD), high-cholesterol diet (HCD), or HCD plus HP, HPH, or HPPS at a dose of 300mg/kg body weight for 4weeks. Results showed that HPPS was more effective than HP and HPH in decreasing the body weight gain (by 38.2%), liver weight (by 16.4%), and plasma and hepatic total cholesterol (TC; by 23.6% and 27.3%, respectively) of hamsters. In addition, the bile acid levels in the feces were significantly higher by 39.8% and 132.8% in the HPH and HPPS groups than in the HCD group. Such changes were not noted in the HP group. However, the HP group had higher cholesterol excretion capacities than the HPH and HPPS groups by inhibiting cholesterol absorption in the diet, with a 21.7% increase in TC excretion and a 31.1% decrease in TC absorption. Thus, HPPS could be a promising anti-atherogenic dietary ingredient for the development of functional food to improve cholesterol metabolism.