Effects and improvement mechanisms of ultrasonic pretreatment on the quality of fermented skim milk.

Fermented skim milk is an ideal food for consumers such as diabetic and obese patients, but its low-fat content affects its texture and viscosity. In this study, we developed an effective pretreatment method for fermented skim milk using low-frequency ultrasound (US), and investigated the molecular mechanism of the corresponding quality improvement. The skim milk samples were treated by optimal ultrasonication conditions (336 W power for 7 min at 3 °C), which improved the viscosity, water-holding capacity, sensory attributes, texture, and microstructure of fermented skim milk (P < 0.05). Further mechanistic analyses revealed that the US treatment enhanced the exposure of fluorescent amino acids within proteins, facilitating the cross-linking between casein and whey. The increased surface hydrophobicity of fermented milk indicates that the US treatment led to the exposure of hydrophobic amino acid residues inside proteins, contributing to the formation of a denser gel network; the average particle size of milk protein was reduced from 24.85 to 18.06 µm, which also contributed to the development of a softer curd texture. This work is the first attempt to explain the effect of a low-frequency ultrasound treatment on the quality of fermented skim milk and discuss the molecular mechanism of its improvement.

Effect and potential mechanism of nitrite reductase B on nitrite degradation by Limosilactobacillus fermentum RC4.

Nitrite has the potential risk of hypoxic poisoning or cancer in pickled food. In our previous study, Limosilactobacillus fermentum (L. fermentum) RC4 is effective in nitrite degradation by producing nitrite reductase B (NirB). To investigate the detailed mechanism from the genome, response, and regulation of NirB, the whole-genome sequence of L. fermentum RC4 was analyzed, the L. fermentum-EGFP-nirB with enhanced green fluorescent protein (EGFP) labeled the nitrite reductase large subunit nirB, and the recombined L. fermentum-NirB with overexpression NirB strain was conducted. The key genes within the dominant metabolism pathways may be involved in stress tolerance to regulate the degrading process. The green fluorescence density of EGFP indicated that NirB activity has a threshold and peaked under 300 mg/L nitrite concentration. NirB overexpressed in L. fermentum RC4 boosted the enzyme activity by 39.6% and the degradation rate by 10.5%, when fermented in 300 mg/L for 40 h, compared to the control group. RNA-seq detected 248 differential genes mainly enriched in carbohydrate, amino acid, and energy metabolism. The ackA gene for pyruvate metabolism and the mtnN gene for cysteine metabolism were up-regulated. NirB regulates these genes to produce acid and improve stress resistance for L. fermentum RC4 to accelerate nitrite degradation.

Legume protein fermented by lactic acid bacteria: Specific enzymatic hydrolysis, protein composition, structure, and functional properties.

In recent years, with increasing emphasis on healthy, green, and sustainable consumption concepts, plant-based foods have gained popularity among consumers. As widely sourced plant-based raw materials, legume proteins are considered sustainable and renewable alternatives to animal proteins. However, legume proteins have limited functional properties, which hinder their application in food products. LAB fermentation is a relatively natural processing method that is safer than chemical/physical modification methods and can enrich the functional properties of legume proteins through biodegradation and modification. Therefore, changes in legume protein composition, structure, and functional properties and their related mechanisms during LAB fermentation are described. In addition, the specific enzymatic hydrolysis mechanisms of different LAB proteolytic systems on legume proteins are also focused in this review. The unique proteolytic systems of different LAB induce specific enzymatic hydrolysis of legume proteins, resulting in the production of hydrolysates with diverse functional properties, including solubility, emulsibility, gelability, and foamability, which are determined by the composition (peptide/amino acid) and structure (secondary/tertiary) of legume proteins after LAB fermentation. The correlation between LAB-specific enzymatic hydrolysis, protein composition and structure, and protein functional properties will assist in selecting legume protein raw materials and LAB strains for legume plant-based food products and expand the application of legume proteins in the food industry.

Preparation of modified chitosan-based nano-TiO2-nisin composite packaging film and preservation mechanism applied to chilled pork.

Here, we developed a nano-TiO2-nisin-modified chitosan composite packaging film and investigated its properties and antibacterial activity, as well as its effect on chilled pork preservation time. The results indicated that the preservation time of chilled pork coated with a nano-TiO2-nisin-modified chitosan film (including 0.7 g/L nano-TiO2, irradiated with ultraviolet light for 40 min, and dried for 6 h) followed by modified atmosphere packaging (50% CO2 + 50% N2) increased from 7 to 20 days at 4 °C. Both nano-TiO2 and nisin enhanced the mechanical strength of the chitosan film, and nisin promoted nano-TiO2 dispersion and compatibility in chitosan. Treatment with 0.4 g/L nano-TiO2 for 60 min considerably inhibited spoilage bacteria, particularly Acinetobacter johnnii XBB1 (A. johnnii XBB1). As nano-TiO2 concentration and photocatalytic time increased, K+, Ca2+, and Mg2+ leakage in A. johnnii XBB1 increased but Na+/K+-ATPase and Ca2+/Mg2+-ATPase activities decreased. In A. johnnii XBB1, TiO2 significantly downregulated the expression of putrefaction-related genes such as cysM and inhibited cell self-regulation and membrane wall system repair. Therefore, our nano-TiO2-nisin-modified chitosan film could extend the shelf life without the addition of any chemical preservatives, demonstrating great potential for application in food preservation.

Elimination of Pathogen Biofilms via Postbiotics from Lactic Acid Bacteria: A Promising Method in Food and Biomedicine.

Pathogenic biofilms provide a naturally favorable barrier for microbial growth and are closely related to the virulence of pathogens. Postbiotics from lactic acid bacteria (LAB) are secondary metabolites and cellular components obtained by inactivation of fermentation broth; they have a certain inhibitory effect on all stages of pathogen biofilms. Postbiotics from LAB have drawn attention because of their high stability, safety dose parameters, and long storage period, which give them a broad application prospect in the fields of food and medicine. The mechanisms of eliminating pathogen biofilms via postbiotics from LAB mainly affect the surface adhesion, self-aggregation, virulence, and QS of pathogens influencing interspecific and intraspecific communication. However, there are some factors (preparation process and lack of target) which can limit the antibiofilm impact of postbiotics. Therefore, by using a delivery carrier and optimizing process parameters, the effect of interfering factors can be eliminated. This review summarizes the concept and characteristics of postbiotics from LAB, focusing on their preparation technology and antibiofilm effect, and the applications and limitations of postbiotics in food processing and clinical treatment are also discussed.

New clues for postbiotics to improve host health: a review from the perspective of function and mechanisms.

Strain activity and stability severely limit the beneficial effects of probiotics in modulating host health. Postbiotics have emerged as a promising alternative as they can provide similar or even enhanced efficacy to probiotics, even under inactivated conditions. This review introduces the ingredients, preparation, and identification techniques of postbiotics, focusing on the comparison of the advantages and limitations between probiotics and postbiotics based on their mechanisms and applications. Inactivation treatment is the most significant difference between postbiotics and probiotics. We highlight the use of emerging technologies to inactivate probiotics, optimize process conditions to maintain the activity of postbiotics, or scale up their production. Postbiotics have high stability which can overcome unfavorable factors, such as easy inactivation and difficult colonization of probiotics after entering the intestine, and are rapidly activated, allowing continuous and rapid optimization of the intestinal microecological environment. They provide unique mechanisms, and multiple targets act on the gut-organ axis, co-providing new clues for the study of the biological functions of postbiotics. We summarize the mechanisms of action of inactivated lactic acid bacteria, highlighting that the NF-κB and MAPK pathways can be used as immune targeting pathways for postbiotic modulation of host health. Generally, we believe that as the classification, composition, and efficacy mechanism of postbiotics become clearer they will be more widely used in food, medicine, and other fields, greatly enriching the dimensions of food innovation. © 2024 Society of Chemical Industry.

Effects of Semen Ziziphi Spinosae extract and binary probiotics co-fermentation on the quality of yogurt and their underlying molecular mechanisms.

The study aimed to investigate the impact of water-soluble extract from Semen Ziziphi Spinosae (SZSE) on yogurt quality and understand the underlying mechanism. The results demonstrated that adding 0.5% (w/v) SZSE had a significant effect on reducing yogurt syneresis and resulted in a more compact and uniform casein gel. Notably, the co-fermented yogurt with binary probiotics (Lacticaseibacillus casei CGMCC1.5956 and Levilactobacillus brevis CGMCC1.5954) along with SZSE led to increased viable probiotics and a higher odor score (23.23). This effect might be attributed to the increased amino acid utilization by binary probiotics through biosynthesis of valine, leucine and isoleucine, metabolic pathways, and amino acid biosynthesis to produce amino acid derivatives such as N5-(l-1-carboxyethyl)-l-ornithine and diaminopyrimidine acid. The yogurt contained 79 volatile flavor compounds, with hexanoic acid, 2-heptanone, and 2-nonanone potentially contributing to the high odor scores. These findings have strategic implications for developing yogurt with high gel characteristics and distinctive flavor.

Recent Advances on Antimicrobial Peptides from Milk: Molecular Properties, Mechanisms, and Applications.

Traditional antibiotics are facing a tremendous challenge due to increased antimicrobial resistance; hence, there is an urgent need to find novel antibiotic alternatives. Milk protein-derived antimicrobial peptides (AMPs) are currently attracting substantial attention considering that they showcase an extensive spectrum of antimicrobial activities, with slower development of antimicrobial resistance and safety of raw materials. This review summarizes the molecular properties, and activity mechanisms and highlights the applications and limitations of AMPs derived from milk proteins comprehensively. Also the analytical technologies, especially bioinformatics methodologies, applied in the process of screening, identification, and mechanism illustration of AMPs were underlined. This review will give some ideas for further research and broadening of the applications of milk protein-derived AMPs in the food field.

Transcriptomic Responses to Nitrite Degradation by Limosilactobacillus fermentum RC4 and Effect of ndh Gene Overexpression on Nitrite Degradation.

The excessive nitrite residue may increase cell damage and cancer risk. Limosilactobacillu fermentum RC4 exhibited excellent nitrite degradation ability. Herein, the molecular mechanism of nitrite degradation by L. fermentum RC4 was studied by integrating scanning electron microscopy analysis, transcriptomics, and gene overexpression. The results demonstrated that the gene profile of RC4 cultured in MRS broth with 0, 100, and 300 mg/L NaNO2 varied considerably; RC4 responded to nitrite degradation by regulating pyruvate metabolism, energy synthesis, nitrite metabolism, redox equilibrium, protein protection, and signaling. High nitrite concentrations affected the morphology of RC4 with a longer phenotype, rough and wrinkle cell and reduced cell surface hydrophobicity. Moreover, an up-regulated expression of gene ndh encoding NADH dehydrogenase, which provides electrons for nitrite reduction by catalyzing NADH, was identified when RC4 was exposed to nitrite. Overexpression of ndh in RC4 increased the nitrite degradation rate by 2-9.5% in MRS broth with 100 mg/L NaNO2. Thus, the findings of this study could be helpful for the application of L. fermentum to reduce nitrite residues and improve food safety in fermented food products.

Plant-based meat analogs and fat substitutes, structuring technology and protein digestion: A review.

There is currently an increasing trend in the consumption of meat analogs and fat substitutes due to the health hazards by excessive consumption of meat. Simulating the texture and mouthfeel of meat through structured plant-derived polymers has become a popular processing method. In this review, the mechanical structuring technology of plant polymers for completely replacing real meat is mainly introduced in this review, which mainly focuses on the parameters and principles of mechanical equipment for the production of vegan meat. The difference in composition between plant meat and real meat is mainly reflected in the protein, and particular attention should be paid to the digestive characteristics of plant meat protein in the gastrointestinal tract. Therefore, the differences in the protein digestibility properties of meat analogs and real meat is discussed in this review, focusing primarily on protein digestibility and peptide/amino acid composition of mechanically structured vegan meats. In terms of fat substitutes for meat products, the types of plant polymer colloidal systems used for meat fat substitutes is comprehensively introduced, including emulsion, hydrogel and oleogel.

Nanocoating of lactic acid bacteria: properties, protection mechanisms, and future trends.

Lactic acid bacteria (LAB) is a type of probiotic that may benefit intestinal health. Recent advances in nanoencapsulation provide an effective strategy to protect them from harsh conditions via surface functionalization coating techniques. Herein, the categories and features of applicable encapsulation methods are compared to highlight the significant role of nanoencapsulation. Commonly used food-grade biopolymers (polysaccharides and protein) and nanomaterials (nanocellulose and starch nanoparticles) are summarized along with their characteristics and advances to demonstrate enhanced combination effects in LAB co-encapsulation. Nanocoating for LAB provides an integrity dense or smooth layer attributed to the cross-linking and assembly of the protectant. The synergism of multiple chemical forces allows for the formation of subtle coatings, including electrostatic attractions, hydrophobic interactions, π-π, and metallic bonds. Multilayer shells have stable physical transition properties that could increase the space between the probiotic cells and the outer environment, thus delaying the microcapsules burst time in the gut. Probiotic delivery stability can be promoted by enhancing the thickness of the encapsulated layer and nanoparticle binding. Maintenance of benefits and minimization of nanotoxicity are desirable, and green synthesized nanoparticles are emerging. Future trends include optimized formulation, especially using biocompatible materials, protein or plant-based materials, and material modification.

Intelligent Evaluation Method of Human Cervical Vertebra Rehabilitation Based on Computer Vision.

With the changes in human work and lifestyle, the incidence of cervical spondylosis is increasing substantially, especially for adolescents. Cervical spine exercises are an important means to prevent and rehabilitate cervical spine diseases, but no mature unmanned evaluating and monitoring system for cervical spine rehabilitation training has been proposed. Patients often lack the guidance of a physician and are at risk of injury during the exercise process. In this paper, we first propose a cervical spine exercise assessment method based on a multi-task computer vision algorithm, which can replace physicians to guide patients to perform rehabilitation exercises and evaluations. The model based on the Mediapipe framework is set up to construct a face mesh and extract features to calculate the head pose angles in 3-DOF (three degrees of freedom). Then, the sequential angular velocity in 3-DOF is calculated based on the angle data acquired by the computer vision algorithm mentioned above. After that, the cervical vertebra rehabilitation evaluation system and index parameters are analyzed by data acquisition and experimental analysis of cervical vertebra exercises. A privacy encryption algorithm combining YOLOv5 and mosaic noise mixing with head posture information is proposed to protect the privacy of the patient's face. The results show that our algorithm has good repeatability and can effectively reflect the health status of the patient's cervical spine.

Competitive binding of maltodextrin and pectin at the interface of whey protein hydrolyzate-based fish oil emulsion under high temperature sterilization: Effects on storage stability and in vitro digestion.

Whey protein hydrolysate (WPH), maltodextrin (MD), low methoxy pectin (LMP) and high methoxy pectin (HMP) were used to study the interface binding under high temperature sterilization conditions (121 °C, 15 min). The effect of competitive binding of MD and pectin with interface protein on the storage stability and gastrointestinal fate of fish oil emulsion was studied. The low-molecular-weight MD and the interface protein undergo a wide range of covalent binding through the Maillard reaction, while a small amount of high-molecular-weight pectin can form a protective shell with the interface protein through electrostatic interaction to inhibit the covalent reaction of MD, which was called competitive binding. However, due to the bridging and depletion flocculation of pectin, the emulsification stability of fish oil emulsion reduced. After 13 days of storage, compared with the particle size of the WPH fish oil emulsion (459.18 nm), the fish oil emulsion added with LMP and HMP reached 693.58 nm and 838.54 nm, respectively. In vitro digestion proved that WPH fish oil emulsion flocculated rapidly in the stomach (1.76 µm), while WPH-MD and WPH-MD-pectin fish oil emulsions flocculated slightly (less than800 nm). WPH-MD-pectin delayed digestion in the gastrointestinal tract, and HMP exhibited a better slow-release effect. This study provides reference for the design of multi-component functional drinks and other bioactive ingredient delivery system.

Interaction between Kidney-Bean Polysaccharides and Duck Myofibrillar Protein as Affected by Ultrasonication: Effects on Gel Properties and Structure.

The interaction of polysaccharides-protein with varied origins and structures provides opportunities for tailoring the physicochemical qualities of food protein-based materials. This work examined the feasibility of ultrasound-modified interaction between kidney bean dietary fiber (KSDF) and duck myofibrillar proteins (MP) to improve the physicochemical properties of the gel matrices. Accordingly, gel strength, water holding capacity, solubility, chemical interaction, secondary structure, and network structure of MP were determined. The addition of KSDF combined with the ultrasound treatment contributed to the improved water retention capability, G' values, and the reduced particle size of protein molecules, corresponding with the formation of dense pore-like structures. The results demonstrated that 1% KSDF and ultrasonication at 400 W significantly enhanced gel strength by up to 109.58% and the solubility increased by 213.42%. The proportion of α-helices of MP gels treated with 1% KSDF and ultrasonication at 400 W was significantly increased. The sonication-mediated KSDF-MP interaction significantly improved hydrophobic interactions of the proteins, thus explaining the denser network structure of the MP gels incorporated KSDF with ultrasound treatments. These results demonstrated the role of ultrasonication treatments in modifying KSDF-protein interaction to improve the gel and structural properties of the MP gels.

miR-26b-5p suppresses chemoresistance in breast cancer by targeting serglycin.

Chemoresistance is a crucial barrier to limit the therapeutic outcome of breast cancer (BC), and the mechanism underlying chemoresistance development in BC is not fully understood. In this study, we aimed to investigate the potential involvement of miR-26b-5p/serglycin (SRGN) axis in BC drug resistance. The expression level of SRGN in drug-resistant BC cells was investigated by western blotting analysis, real-time quantitative PCR (qRT-PCR), immunohistochemical staining, and ELISA. Its expression between chemoresistant and sensitive patient samples was compared by qRT-PCR. Bioinformatics tool and dual-luciferase reporter assay were employed to identify miR-26b-5p as a regulator of SRGN. Functional assays were performed to examine cell proliferation, cell viability, apoptosis, migration, and invasion ability in vitro. Xenograft tumorigenesis experiment was conducted to evaluate the tumor suppressor effect of miR-26b-5p on chemoresistant BC cells. SRGN expression was significantly upregulated in both chemoresistant BC cell lines and chemoresistant patient samples. miR-26b-5p was identified as an upstream regulator of SRGN. Overexpression of miR-26b-5p downregulated SRGN expression, overcame chemoresistance, and suppressed cell proliferation, migration, and invasion in BC cells. Overexpression of miR-26b-5p also suppressed the tumorigenesis of chemoresistant BC cells in vivo. Mechanistically, the downregulation of SRGN by miR-26b-5p decreased the expression of breast cancer drug-resistant protein and multidrug-resistant protein 1 in chemoresistant BC cells. Our study identified miR-26b-5p as a tumor suppressor which targets SRGN to sensitize BC cells to chemotherapeutics. These results suggest that miR-26b-5p and SRGN may serve as potential biomarkers and targets for BC chemotherapy.

The complex of whey protein and pectin: Interactions, functional properties and applications in food colloidal systems - A review.

This review describes the mechanism of non-covalent/covalent interaction of whey protein-pectin (WPP) complexes, including electrostatic interaction, steric hindrance, cross-linking and Maillard reaction. The interaction between whey protein and pectin determines the form of the complex in the system, i.e. co-dissolution, precipitation, separation, complex coacervation and compounding. The interaction of WPP is affected by environmental conditions and its own properties, including several factors such as pH, polymer concentration and ratio, temperature, and ionic strength. In addition, the functional properties of WPP complexes are discussed through illustrative examples. The complexes with good emulsification, heat stability, gelling properties and biological activity have promising application prospects. WPP complexes have been widely studied for application in food colloidal systems, including protein beverages, delivery systems for bioactive substances, fat substitutes and food preservation films/coatings. The understanding of the interaction and functional properties of WPP complexes provides theoretical support for the improvement and design of new food colloidal systems.

Recent Progress on Protein-Polyphenol Complexes: Effect on Stability and Nutrients Delivery of Oil-in-Water Emulsion System.

Oil-in-water emulsions are widely encountered in the food and health product industries. However, the unsaturated fatty acids in emulsions are easily affected by light, oxygen, and heat, which leads to oxidation, bringing forward difficulties in controlling emulsion quality during transportation, storage, and retail. Proteins are commonly used as emulsifiers that can enhance the shelf, thermal and oxidation stability of emulsions. Polyphenols are commonly found in plants and members of the family have been reported to possess antioxidant, anticancer, and antimicrobial activities. Numerous studies have shown that binding of polyphenols to proteins can change the structure and function of the latter. In this paper, the formation of protein-polyphenol complexes (PPCs) is reviewed in relation to the latters' use as emulsifiers, using the (covalent or non-covalent) interactions between the two as a starting point. In addition, the effects polyphenol binding on the structure and function of proteins are discussed. The effects of proteins from different sources interacting with polyphenols on the emulsification, antioxidation, nutrient delivery and digestibility of oil-in-water emulsion are also summarized. In conclusion, the interaction between proteins and polyphenols in emulsions is complicated and still understudied, thereby requiring further investigation. The present review results in a critical appraisal of the relevant state-of-the-art with a focus on complexes' application potential in the food industry, including digestion and bioavailability studies.

The interfacial covalent bonding of whey protein hydrolysate and pectin under high temperature sterilization: Effect on emulsion stability.

In this study, the effect of high-pressure steam sterilization (121 °C for 15 min) on whey protein hydrolysate-pectin solutions and emulsions was studied. The interaction and emulsification characteristics of pectin and whey protein concentrate (WPC) were evaluated from the solution system to the emulsion system. Enzymatic hydrolysis of WPC (WPH, 2 % and 8 % degree of hydrolysis) increased the covalent binding with pectin, which reduced the heat-induced aggregation of protein and improved emulsification. The thermodynamic incompatibility between WPC and pectin was not conducive to the covalent bonding under high temperature sterilization and produced serious aggregates, which also made a rapid increase in particle size (up to ∼3 µm), compared to WPH-pectin emulsion (∼ 400 nm). In addition, if emulsion was stirred during the sterilization, the creaming and protein aggregation could be avoided. By comparing low methoxy pectin (LMP) and high methoxy pectin (HMP), it was found that the whey protein-HMP complex had better emulsification stability, and the steric stabilization played a more important role in emulsion stability than the electrostatic repulsion. The changes of whey protein and pectin at the oil-water interface of the emulsion during the sterilization process may provide a reference for the sterilized bioactive ingredient delivery system.

Characterization of silver carp myosin glycated with phosphorylated konjac oligo-glucomannan.

BACKGROUND: Myosin (Ms) is abundant in fish meat, but it has limited application in the food industry because of its low solubility and thermal stability. Our previous reports found that these functional properties of Ms can be significantly improved after glycation with konjac oligo-glucomannan (KOG). However, the effects of phosphorylated KOG (PKOG) on physicochemical, structural and functional properties of silver carp Ms are still unknown. RESULTS: This study characterized the silver carp Ms protein glycated with PKOG at 50 °C and 75% relative humidity for 48 h. As degree of phosphorylation increased, free amino content increased, whereas degree of grafting decreased. Meanwhile, isoelectric point (pI) reduced, however, PKOGs showed no differences in pI. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis suggested the formation of glycoconjugates, and scanning electron microscopy revealed thinner flakes and uneven appearance of glycoconjugates. Fourier transform infrared spectroscopy indicated that the amide I, II and III bands of Ms were changed by the glycation. Ms became highly soluble in 0.5 mol L-1 NaCl with increased phosphate addition in PKOGs. Thermal stability of Ms was effectively improved when heated at 80 °C for 60 min. CONCLUSION: Glycation with appropriate PKOG might be a promising method for Ms modification because of the resulting improvement in solubility and thermal stability. © 2021 Society of Chemical Industry.

Whey protein and maltodextrin-stabilized oil-in-water emulsions: Effects of dextrose equivalent.

The aim of this work is to evaluate the effect of dextrose equivalent (DE) of maltodextrins (MD) on the stability of whey protein and maltodextrin stabilized oil-in-water (o/w) emulsions. Emulsions with DE 15 maltodextrin (MD 15) exhibited better stability under light acidic (pH 6), neutral and alkaline (pH 8-9) conditions, as well as during temperature ramps (20-60 °C). After 15-days of storage, MD 15 emulsion showed increase in polydispersity and decrease in the average droplet size. The apparent viscosity of the emulsions decreased with increasing DE. The shear stresses of all emulsions fitted well with the power law model (R2 > 0.9), while MD 15 showed the most stable k and n indexes. The brightness and whiteness of emulsion decreased with increases in DE. In conclusion, emulsions with MD 15 exhibited better stability, which suggests their good potential for use in the preparation of energy drinks.