Search Results (63)

Fermented strains play a crucial role in shaping the physicochemical properties and functionality of fermented cow’s milk. The natural fermentation system demonstrates a certain degree of stability and safety after undergoing continuous domestication. Fermented mare’s milk has been consumed for its intestinal health benefits in regions such as Xinjiang and Inner Mongolia in China. This consumption is closely related to the fermented strains present. Consequently, from the perspective of fermented strains, this study aimed to compare the microbiota diversity of naturally fermented mare’s milk with that of inoculated fermented cow’s milk, using it as a fermentation system to develop new functional fermented cow’s milk products. Water retention, rheology, texture, pH, and titration acidity were analyzed to evaluate the quality of fermented cow’s milk with the obtained transmission strain system. Importantly, the correlation between the property of fermented cow’s milk and the diversity of fermentation system has been thoroughly analyzed. The findings indicate that the gel property of fermented cow’s milk is not directly linked to the strain diversity or the core strain of fermentation. Instead, the abundance of Lactobacillus, Lactococcus, Hafnia-Obesumbacterium, Leuconostoc, Acetobacter, and Acinetobacter bacteria significantly influences the quality of fermented cow’s milk. Consequently, this study has successfully developed a new type of fermented cow’s milk and provided a reliable theoretical foundation for the functional enhancement of specialized fermented cow’s milk products. Full article

This study investigates the impact of honey concentrations (1%, 3%, and 5%) on the physicochemical, sensory, textural, rheological, and antioxidant properties of probiotic yogurt beverages made from sheep, cow, and blended milk. Honey, used as a natural fortifier, enhanced antioxidant activity, probiotic viability, and sensory attributes, particularly flavor and viscosity. Sheep milk yogurt exhibited superior nutritional and textural properties due to its higher solid and nutrient content. Increasing honey levels improved lactic acid fermentation, gel matrix stability, and water-holding capacity, though excessive concentrations occasionally increased syneresis and reduced bacterial counts. Texture profile analysis indicated that 3% honey optimized hardness, springiness, and cohesiveness, strengthening the yogurt matrix. This study highlights honey’s dual role as a sweetener and functional ingredient, enhancing yogurt beverages’ health benefits, stability, and consumer appeal. Full article

Purification and characterization of milk oligosaccharides is a challenging process due to the complexity of the constituent oligosaccharides, which behave differently under various chemical treatment procedures and often lose their structural properties in the process. Rathi cow’s milk is widely used in the Rajasthan region of India for its nutritional and medicinal benefits. Here, we aim to present an optimized method for the purification and analysis of oligosaccharides present in Rathi cow milk. Contrary to the freeze transport methods used earlier, we treated the collected milk with ethanol for preservation, followed by microfiltration, lyophilization, and fractionation on silica gel (60–120 mesh size) column chromatography (CC) coupled with chloroform/methanol-mediated gradient elution. Fractions 31–45 (1.78 g), 71–80 (470 mg), and 106–120 (498 mg) from CC-1 and fractions 26–49 (1.14 g) from CC-2 were analysed for sugar content via the phenol–sulfuric acid method. Fraction homogeneity was confirmed using high-performance liquid chromatography. Isolated analytes were treated with acetic anhydride/pyridine (1:1, v/v) to form less polar oligosaccharide derivatives, which could then be easily visualized and semi-quantitated using partition chromatography (thin later and paper) with chloroform/methanol. Structural identities of the purified oligosaccharides were determined using a combination of mass spectrometry and NMR (¹H, ¹³C, HSQC, TOCSY, COSY, HMBC) techniques. Our results clearly demonstrate that the ethanol-based preservation, transport, and purification of oligosaccharides is a simple and robust method for the analysis of Rathi cow’s milk oligosaccharides. Furthermore, using the acetylation, purified oligosaccharides allow for rapid analysis on thin-layer chromatography, which is quite cost effective compared with other analytical methods. Full article

This study optimizes the process conditions for preparing angiotensin-converting enzyme (ACE) inhibitory peptides from skimmed goat milk (SGM) hydrolyzed by multi-enzymes using response surface methodology. When the enzymatic hydrolysis time was 90 min, the optimal hydrolysis conditions were a pH of 8.49, enzyme-to-substrate ratio (E/S ratio) of 8.04%, and temperature of 61.54 °C. The hydrolysis degree and ACE inhibitory activity were 65.39% ± 0.01% and 84.65% ± 0.03%, respectively. After purification by ultrafiltration, macroporous resin, and gel filtration, the ACE inhibitory activity of F2-2 in the two components of F2 was higher, with the ACE inhibitory rate of 93.97% ± 0.15% and IC₅₀ of 0.121 ± 0.004 mg/mL. The content of hydrophobic amino acids, fatty amino acids, and aromatic amino acids in component F2-2 accounts for 73.17%, 33.86%, and 33.72%, respectively. Eleven peptides were isolated and identified from the F2-2 components of the enzymatic hydrolysate of SGM, including two peptides without an established database. The peptides mainly came from β casein, α_S1 casein, and α_S2 casein. Full article

The present study aims to evaluate the physicochemical and sensory characteristics of A2 yoghurts (made with A2A2 β-CN milk), in comparison with Control yoghurts (elaborated from conventional milk, a mixture of A1 and A2 β-CN milk). The pH, acidity, water-holding capacity, spontaneous syneresis, firmness and color of yoghurts were monitored during their cold storage (4 °C) for 35 days. Two independent sensory tests (with expert judges and consumers) were also performed. The A2 yoghurts showed only minor differences in some of their physicochemical and sensory characteristics compared to those made with conventional milk. At specific storage times, the A2 yoghurt exhibited higher levels of acidity, luminosity (L*) and firmness, compared to the Control. No differences were observed in the growth curves of the starter (Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus) during the yoghurt production, nor in the water-holding capacity or spontaneous syneresis of the two types of gels. Regarding the sensory evaluation of samples, the A2 yoghurts were described as firmer and more adherent (by the expert panel), and brighter and more homogeneous (by the consumers) than the Control. In all cases, both consumers and expert sensory panels showed a preference for the A2 yoghurts. Therefore, these results demonstrate the suitability of A2A2 β-CN milk for producing yoghurts with similar characteristics to those obtained with conventional milk. Full article

Background/Objectives: The increasing occurrence of extended-spectrum β-lactamase (ESBL)–producing Enterobacterales, most commonly Escherichia coli, has become a serious problem. The aim of this study was to determine the presence of ESBL-producing Gram-negative bacteria in dairy cattle, goat and sheep farms located in southern Türkiye. Methods: Samples (409 quarter milk samples and 110 fresh faecal samples from cattle, 75 bulk tank milk samples and 225 rectal swab samples from goats and sheep) were subjected to selective isolation on MacConkey agar with ceftazidime (2 µg/mL). Isolates were identified by MALDI-ToF MS. The antimicrobial susceptibility profile of the isolates was determined by the broth microdilution method. To obtain a deeper insight into the genetic diversity of isolates substantially contributing to an efficient spread of their ESBL-determinants (23-MO00001: an E. coli from mastitis and 23-MO00002 Citrobacter freundii), the transmission potential and the genetic background of the plasmid carrying the bla_CTX-M determinant was studied with whole genome analysis using Illumina sequencing. Results: Of the samples tested, 47 from the bovine faecal samples, 1 from the subclinical mastitis milk sample, 9 from the goat/sheep rectal swab samples and 5 from the goat/sheep bulk tank milk samples had ceftazidime-resistant Gram-negative strains with the ESBL phenotype. Of the 33 ESBL-producing E. coli isolates, 66.6% were resistant to tetracycline, 57.6% to sulfamethoxazole, 48.9% to nalidixic acid, 42.4% to ciprofloxacin and 33.3% to trimethoprim. Pulsed field gel electrophoresis (PFGE) results showed that the majority of E. coli isolates (16/33) and all Enterobacter spp. isolates (n = 5) were not clonally related (80% similarity cut value). The sequenced strains were observed to efficiently transfer their ceftazidime resistance to the recipient strain E. coli J53 at 37 °C (transfer rates: 10¹–10² transconjugants per donor cell). S1-PFGE showed that the transconjugants J53(p23MO01-T1) and J53(p23MO02-T1) had acquired plasmids of about 82 kb and 55 kb plasmids, respectively. According to WGS results, the E. coli isolate was assigned to ST162, while the C. freundii isolate was assigned to ST95. Conclusions: This study demonstrates that dairy animals are reservoirs of ESBL-producing bacteria. Full article

The mutualistic relationship between Streptococcus thermophilus (S. thermophilus) and L. delbrueckii subsp. bulgaricus (L. bulgaricus) is responsible for milk coagulation, gel formation, and the flavour of yogurt. Under set-style yogurt processing conditions, the performance of a mixed culture composed of these species depends on key technological parameters such as the capacity for acidification and proteolytic activity. This study aimed to determine the extent of phenotypic diversity by comparing the key traits of acidification and proteolytic activity among isolates found in yogurt starter cultures. Seventy-two isolates from three industrial starter cultures were ranked by either their fast or slow acidification activity (time to reach pH 4.6, 16 h), proteolytic activity, cell envelope proteinase (CEP) activity, redox potential and titratable acidity. The integration of multiple phenotype measures by hierarchical clustering and non-metric dimensional scaling (NMDS) clustered groups of isolates by multifactor similarity. A significant difference (p-value < 0.05) was observed between the clusters regarding redox potential and the proteolytic activity of both S. thermophilus and L. bulgaricus. The integration of multiple phenotypes points to the diversification that may have occurred over repeated culturing of yogurt starter bacteria. The phenotypic diversity may explain the divergence in starter performance and be used to refine the formulation of new starter cultures. Future work will investigate the correlation between the activity of specific enzymes based on the phenotype to explain the separation between the fast and slow acidification of isolates. Full article

Micellar calcium phosphate (MCP) plays an important role in maintaining the structure and stability of the casein micelle and its properties during processing. The objective of this study was to investigate how heating (10 min at 80 or 90 °C) at different pH levels (6.3, 6.6, 6.9, or 7.2) impacted the acid-induced gelation of MCP-adjusted milk, containing 67 (MCP₆₇), 100 (MCP₁₀₀), or 113 (MCP₁₁₃) % of the original MCP content. The unheated sample MCP₁₀₀ at pH 6.6 was considered the control. pH acidification to pH 4.5 at 30 °C was achieved with glucono delta-lactone while monitoring viscoelastic behaviour by small-amplitude oscillatory rheology. The partitioning of calcium and proteins between colloidal and soluble phases was also examined. In MCP-depleted skim milk samples, the concentrations of non-sedimentable caseins and whey proteins were higher compared to the control and MCP-enriched skim milk samples. The influence of MCP adjustment on gelation was dependent on pH. Acid gels from sample MCP₆₇ exhibited the highest storage modulus (G′). At other pH levels, MCP₁₀₀ resulted in the greatest G′. The pH of MCP-adjusted skim milk also impacted the gel properties after heating. Overall, this study highlights the substantial impact of MCP content on the acid gelation of milk, with a pronounced dependency of the MCP adjustment effect on pH variations. Full article

Copper-chelated chitosan microgels were investigated as an immobilized metal affinity chromatography (IMAC) phase for peptide separation. The copper-crosslinked chitosan beads were shown to strongly interact with a range of amino acids, in a wide range of pH and saline conditions. The beads exhibited an affinity that seemed to depend on the isoelectric point of the amino acid, with the extent of uptake increasing with decreasing isoelectric point. This selective interaction with anionic amino acids resulted in a significant relative enrichment of the supernatant solution in cationic amino acids. The beads were then studied as a novel fractionation system for complex milk hydrolysates. The copper chitosan beads selectively removed larger peptides from the hydrolysate aqueous solution, yielding a solution relatively enriched in medium and smaller peptides, which was characterized both quantitatively and qualitatively by size exclusion chromatography (SEC). Liquid chromatography–mass spectrometry (LCMS) work provided comprehensive data on a peptide sequence level and showed that a depletion of the anionic peptides by the beads resulted in a relative enrichment of the cationic peptides in the supernatant solution. It could be concluded that after fractionation a dramatic relative enrichment in respect to small- and medium-sized cationic peptides in the solution, characteristics that have been linked to bioactivities, such as anti-microbial and cell-penetrating properties. The results demonstrate the use of the chitosan copper gel bead system in lab scale fractionation of complex hydrolysate mixtures, with the potential to enhance milk hydrolysate bioactivity. Full article

We constructed a sodium alginate/soy protein isolate/chitosan gel system and incorporated silver nanoparticles reduced by capsaicin into the system, forming a sodium alginate–soy protein isolate–chitosan–capsaicin–silver nanoparticle composite gel (SA/SPI/CTS/CAP/Ag). In tests, the SA/SPI/CTS/CAP/Ag gel exhibited excellent antimicrobial properties. Using the agar diffusion method, the inhibition zone diameter for Staphylococcus aureus was determined to be 29.5 mm. Soy protein isolate (SPI), containing a large number of hydrophobic amino acid residues, effectively enhanced the moisture retention capability of the gel and improved its stability to a certain extent at an appropriate addition concentration. In a milk preservation experiment, the SA/SPI/CTS/CAP/Ag gel significantly extended the shelf-life of the milk. In dye adsorption experiments, the adsorption curve of the SA/SPI/CTS/CAP/Ag gel well fitted a pseudo-second-order kinetic model. It showed a degree of adsorption capacity for methylene blue, malachite green, methyl orange, and Congo red, with the most significant adsorption effect for malachite green being 42.48 mg/g. Considering its outstanding antimicrobial performance, preservation ability, and adsorption capacity, the SA/SPI/CTS/CAP/Ag gel holds significant potential in wastewater treatment and as an antimicrobial gel in the exploration of food preservation. Full article

Ultra-high temperature sterilized milk (UHT) is a popular dairy product known for its long shelf life and convenience. However, protein gel aging and fat quality defects like creaming and flavor deterioration may arise during storage. These problems are primarily caused by thermostable enzymes produced by psychrotrophic bacteria. In this study, four representative psychrotrophic bacteria strains which can produce thermostable enzymes were selected to contaminate UHT milk artificially. After 11, 11, 13, and 17 weeks of storage, the milk samples, which were contaminated with Pseudomonas fluorescens, Chryseobacterium carnipullorum, Lactococcus raffinolactis and Acinetobacter guillouiae, respectively, demonstrated notable whey separation. The investigation included analyzing the protein and fat content in the upper and bottom layers of the milk, as well as examining the particle size, Zeta potential, and pH in four sample groups, indicating that the stability of UHT milk decreases over time. Moreover, the spoiled milk samples exhibited a bitter taste, with the dominant odor being attributed to ketones and acids. The metabolomics analysis revealed that three key metabolic pathways, namely ABC transporters, butanoate metabolism, and alanine, aspartate, and glutamate metabolism, were found to be involved in the production of thermostable enzymes by psychrotrophic bacteria. These enzymes greatly impact the taste and nutrient content of UHT milk. This finding provides a theoretical basis for further investigation into the mechanism of spoilage. Full article

This research aimed to develop jelly soup for dysphagia patients at the International Dysphagia Diet Standardization Initiative (IDDSI) Framework levels 4 (puree) and 5 (minced and moist), who require swallow training to regain normal swallowing ability due to neurological issues. The study comprised three main parts: (1) an investigation of hydrocolloid types and concentrations for texture-modified foods to aid dysphagia patients during training; (2) a study of sterilization conditions and ascorbic acid’s impact on physical properties (e.g., texture, viscosity, color) of the texture-modified foods; and (3) an evaluation of changes in physical, chemical, and microbial properties of the product during storage. Results revealed that the ideal recipe involved using pork bone broth with 1% κ-carrageenan for texture modification, which closely matched the properties of hospital jelly samples in terms of hardness, adhesiveness, and viscosity. Sterilization at 110 °C for 109 min effectively eliminated microorganisms without affecting the product’s appearance or texture, albeit causing a slight increase in brownness. Adding ascorbic acid helped to prevent the Maillard reaction but reduced the gel strength of the sample and induced milk protein denaturation, leading to aggregation. During storage at room temperature for 9 weeks, the product became browner and less firm. Notably, no bacteria were detected throughout this period. In conclusion, this heating process is suitable for producing jelly soup to support swallow training for dysphagia patients with neurological problems. It offers invaluable assistance in their daily training to regain normal swallowing function. Full article

The aim of this study was to assess the gelling potential of chiral oxalamide derivatives in vegetable oils. Special emphasis was given to the potential applications of the examined oil gels as sustained delivery systems and as fat substitutes in food products. The applicability of oil gelators is envisaged in food, cosmetics, and the pharmaceutical industry. The regulations requiring the elimination of saturated fats and rising concerns among consumers health motivated us to investigate small organic molecules capable of efficiently transforming from liquid oil to a gel state. The oxalamide organogelators showed remarkable gelation efficiency in vegetable oils, thermal and mechanical stability, self-healing properties, and a long period of stability. The physical properties of the gels were analysed by TEM microscopy, DSC calorimetry, and oscillatory rheology. The controlled release properties of acetylsalicylic acid, ibuprofen, and hydrocortisone were analysed by the LC–MS method. The influence of the oil type (sunflower, soybean, and olive oil) on gelation efficiency of diverse oxalamide derivatives was examined by oscillatory rheology. The oxalamide gelators showed thermoreversible and thixotropic properties in vegetable oils with a minimum gelation concentration of just 0.025 wt%. The substitution of palm fats with gelled sunflower oil applied in cocoa and milk spreads at gelator concentrations lower than 0.2 wt% have shown promising viscoelastic properties compared to that of the original food products. Full article

Extracellular polysaccharide (EPS) produced by five lactic acid bacteria (Limosilactobacillus fermentum B55, Limosilactobacillus fermentum B62, Lactiplantibacillus plantarum 7830, Pediococcus acidilactici B30, and Lactobacillus helveticus K2) were purified and identified, and their effects on the texture of fermented goat milk were evaluated. The purified EPS fractions EPS 1a, EPS 2b, EPS 3c, EPS 4d, and EPS 5e of strains B62, 7830, K2, B55, and B30 were obtained with ion exchange chromatography, and their molecular weights were 2.41 × 10⁴, 1.62 × 10⁴, 6.42 × 10³, 6.45 × 10³, and 1.26 × 10⁴ Da, found using gel permeation chromatography. The infrared spectrum results showed that these substances all contained polysaccharide characteristic absorption peaks, most of which contained O-H bonds, C-H bonds, hydroxyl and carboxyl bonds, and groups. The analysis of monosaccharide composition presented that EPS1a was composed of guluronic acid, rhamnose, and galactose, with a molar ratio of 2.7:1:2.4; EPS2b and EPS3c were composed of guluronic acid; EPS4d was composed of guluronic acid, glucose, and galactose, with a molar ratio of 1:1.1:1.2; and EPS5e was composed of glucose and galactose, with a molar ratio of 1.6:1, indicating the differences in the composition and structure of EPS produced by various strains. Compared with the control group that only had the starter added, adding EPS-producing strains could promote acid production and improve the texture of fermented goat milk, and its acidity, hardness, consistency, viscosity, and viscosity index were higher. Full article

During the last decade, research into genetic markers in the casein gene cluster has been actively introduced in cattle breeding programs. A special interest has been paid to the polymorphism of the CSN3 gene, responsible for the expression of the k-casein, playing a key role in protein coagulation, interaction with whey proteins, stabilization, and aggregation of casein micelles. This paper aimed to determine the effect of CSN3 genetic polymorphism on acid; rennet; acid–rennet; heat- and acid-induced as well as heat- and calcium-induced coagulation in skimmed milk; and protein-standardized milk systems (UF, NF, RO, VE). The influence of polymorphic variants of the CSN3 gene on the coagulation ability of milk proteins was assessed by the particle size of casein micelles, protein retention factor in the clot, and coagulation ability (duration of induction period, mass coagulation period, dynamic viscosity in gel point). The correlation between CSN3 gene polymorphism and protein coagulation was revealed. Milk systems obtained from CSN3 BB milk were found to have the shortest duration of coagulation, formation of better gel strength values, and increased yield compared to CSN3 AA. This study will improve the efficiency of milk processing and optimize the technology of dairy product production. Full article