Search Results (72)

Kefiran is a bioactive exopolysaccharide produced by kefir grains, whose synthesis is strongly influenced by culture medium composition. In this study, cheese whey was evaluated as an alternative fermentation substrate for kefiran production, and the effect of supplementation with fermentable sugars (glucose, galactose, and lactose) and casein was assessed under controlled conditions. Kefir grains were cultivated in whey- and milk-based media, and kefiran production was quantified using an anthrone-based method, while grain growth and carbohydrate consumption were monitored. Supplementation with sugars and casein reduced kefiran production by up to 34.6% and did not improve yield, whereas unsupplemented whey supported the highest kefiran concentration (86.9 ± 3.7 mg/L), comparable to that obtained in semi-skimmed milk (84.0 ± 3.0 mg/L). The recovered polysaccharide was characterized by Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (¹H NMR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC), showing structural and physicochemical properties comparable to kefiran obtained from semi-skimmed milk. These results indicate that whey constitutes a feasible and simple fermentation medium for kefiran production, and that increased medium complexity does not necessarily improve process performance. Full article

This study evaluated the fermentation kinetics and properties of kefir beverages produced from whole milk using milk kefir grains (MKGs) or water kefir grains (WKGs) over 48 h. MKGs showed higher initial microbial loads and promoted rapid acidification, with pH decreasing from 6.70 to 4.99 and significant production of lactic acid (10.58 g/L) and ethanol (5.17 g/L), compared with WKGs (final pH 6.20, <0.5 g/L lactic acid, and <0.3 g/L ethanol). However, the final concentration of acetic acid in WKG fermentation (1.93 g/L) was comparable to that in MKG fermentation (2.02 g/L). Microbial populations increased in both systems, exceeding 10⁶ CFU/mL—one of the requirements for conferring probiotic relevance to a beverage—with MKGs reaching higher counts. Lactose and protein consumption were greater in MKGs, suggesting more intense metabolic activity. Fermentation enhanced nutritional value by increasing vitamins B2, B3, B5, and pyridoxine, while vitamin D3 decreased. Mineral composition remained largely unchanged. Volatile analysis identified 31 compounds: MKGs favored fatty acids and lactones associated with creamy notes, whereas WKGs promoted ester formation and fruity aromas. Overall, both grain types produced microbiologically safe beverages with distinct biochemical and sensory profiles, demonstrating the feasibility of using WKGs for milk fermentation. Full article

Kefir grains are a valuable source of exopolysaccharide (EPS)-producing lactic acid bacteria (LAB) with potential applications in fermented dairy products. In this study, LAB isolated from kefir grains originating from five regions were screened for EPS production and probiotic-related properties. Three strains, Lactiplantibacillus plantarum XZ61, Lactobacillus kefiranofaciens EG10, and Lentilactobacillus kefiri EG12, were selected based on high EPS yield, antimicrobial activity, antioxidant capacity, and tolerance to acidic and bile salt conditions. After optimization, the highest EPS yield (539.57 μg/mL) was obtained from strain EG10.The purified EPS consisted of two molecular weight fractions (≈1.4 and 23~25 kDa) and was rich in mannose (33.38~61.58%). Among the three EPS, EG10-EPS exhibited superior emulsifying and flocculating properties comparable to commercial stabilizers, as well as notable ABTS^•+ and hydroxyl radical scavenging activities. Furthermore, co-fermentation of L. kefiranofaciens EG10 with conventional yogurt starter cultures significantly improved exopolysaccharide content, water-holding capacity, texture, and antioxidant activity of fermented milk, particularly in cow milk. These results demonstrate the potential of kefir-derived EPS-producing LAB as natural functional cultures for fermented dairy applications. Full article

In this study, kefir production was investigated using both commercial kefir cultures and kefir grains, with milk treated at different UV-C doses and flow rates. The flow rate was set to 25 or 50 mL/min, and doses of 43.2 and 21.6 J/mL were applied at each flow rate, respectively. In all samples subjected to UV-C treatment, pH values decreased during storage, while % titratable acidity values increased. The kefir samples produced with UV-C-irradiated milk showed increased hardness and consistency, while cohesion and the index of viscosity decreased. The highest effect was observed in samples produced with kefir grain and at a flow rate of 50 mL/min. Lactic acid bacteria, Streptococcus/Lactococcus, and yeast counts in kefir samples produced from UV-C-treated milk increased. Flow rate affected the increase in microorganism counts. The physicochemical, textural, and microbiological changes during storage were more pronounced in kefir samples produced with kefir grains than with powdered cultures. The organic acid levels of kefir samples produced from milk treated with UV-C decreased compared to those of control samples. Furthermore, organic acid values increased during storage in all samples. As the flow rate increased, the amount of organic acids formed decreased (except for malic and formic acid levels). Full article

Kefir grains, originating from the Caucasus, are irregularly shaped, semi-solid granules resembling popcorn or cauliflower (0.3 to 3.5 cm), composed of bacteria and fungi embedded in extracellular polysaccharides such as kefiran. In this study, kefir samples were produced using different ratios of goat’s and cow’s milk (100:0, 75:25, 50:50, 25:75, and 0:100) to examine microbial populations, physicochemical and volatile properties, rheological behaviour, antioxidant capacity, and organic acid content. The type of milk used significantly affected the chemical composition and pH (p < 0.05), although titratable acidity remained stable during storage. Increasing the proportion of goat’s milk decreased viscosity but enhanced the total free amino acid (FAA) content. Goat milk kefir exhibited stronger antioxidant activity than cow milk kefir due to the formation of bioactive peptides and FAAs through proteolysis, with the highest values observed in samples with a higher proportion of goat’s milk and the lowest in 100% cow’s milk kefir. Organic acid levels increased during fermentation and, in 100% goat milk kefir, lactic, acetic, propionic, hippuric, butanoic, and citric acids reached their highest concentrations. The diversity and intensity of volatile compounds also increased proportionally with the goat milk ratio. In conclusion, considering antioxidant activity, volatile aroma components, organic acid content, sensory properties, and viscosity values, sample D, which is 75% goat milk kefir, is recommended for consumers. Full article

Kefiran, the extracellular polysaccharide produced by Generally Recognized as Safe (GRAS) bacteria found in kefir grains, is a promising biopolymer with multiple applications in agri-food and biomedical fields. Besides its characteristics and potential applications, the factors that affect its production remain a prime subject of interest. Lactic acid bacteria synthesize polysaccharides to protect their cells from adverse conditions. Therefore, low-temperature storage (4 °C) of kefir grains inoculated into Ultra-High-Temperature (UHT) milk at two different concentrations (5% and 30%) was studied as a factor for increasing kefiran production in the medium. The cryoprotectant disaccharide trehalose, which comprises a carbon and energy source for many microorganisms, was also evaluated for its effectiveness in enhancing kefiran production. The pH, the increase in kefir grain mass, the amount of kefiran produced, and the rheological properties of the acidified milk were determined during two distinct storage periods, depending on kefir grain concentration. For comparison, kefir grains were also fermented at 25 °C and 30 °C. Low-temperature storage at a kefir grain concentration of 30% resulted in an increase in the amount of polysaccharide produced beyond that obtained through fermentation. Fermentation of a 5% grain inoculum at 30 °C resulted in the lowest kefiran production. In the presence of trehalose, prolonged low-temperature storage favored an increase in the biosynthesis of kefiran, especially at a 30% kefir grain inoculum. Trehalose, however, was not a significant factor in the fermentation experiments. Proper selection of low-temperature storage time is required to avoid a reduction in kefiran concentration due to the metabolic activity of the microorganisms in kefir grains. The acidified milk (low-temperature storage) and kefir (fermentation) samples both exhibited increased elasticity and apparent viscosity with increasing kefir grain concentration. However, the rheological behavior of acidified milk was greatly affected by protein degradation during low-temperature storage. As shown by the findings of the present study, low-temperature storage (4 °C) of a 30% kefir grain inoculum in the presence of trehalose (3% w/w) until a final pH of 4.2 proves to favor kefiran production in the medium the most. Full article

Nowadays, consumer demand for functional foods with health benefits has grown significantly. In response to this trend, a variety of potentially probiotic foods have been developed—most notably kefir and kefir-like beverages, which are highly appreciated for their tangy flavor and health-promoting properties. Traditionally, kefir is made by fermenting cow’s milk with milk kefir grains, although milk from other animals—such as goats, ewes, buffalo, camels, and mares—is also used. Additionally, non-dairy versions are made by fermenting plant-based milks (such as coconut, almond, soy, rice, and oat) with the same type of grains, or by fermenting fruit and vegetable juices (e.g., apple, carrot, fennel, grape, tomato, prickly pear, onion, kiwifruit, strawberry, quince, pomegranate) with water kefir grains. Despite their popularity, many aspects of kefir production remain poorly understood. These include alternative production methods beyond traditional batch fermentation, kinetic studies of the process, and the influence of key cultivation variables—such as temperature, initial pH, and the type and concentration of nutrients—on biomass production and fermentation metabolites. A deeper understanding of the fermentation process can enable the production of kefir beverages tailored to meet diverse consumer preferences. Full article

This present study investigated the microbial dynamics, physicochemical and functional properties, and sensory characteristics of kefir produced by two different approaches: traditional kefir obtained directly from grains and kefir manufactured through a double-fermentation process in cow milk. For the first fermentation, kefir grains were inoculated in milk at different levels (1%, 3%, and 5% w/v) and incubated at 30 °C for 24 h. The lowest inoculation level promoted the greatest increase in grain biomass, whereas higher inoculation levels produced more pronounced pH decreases. All products maintained stable pH values during refrigerated storage at 4 °C for 15 days. Products derived from initial fermentations with 1% and 3% inoculum were subsequently used in a second fermentation step at two inoculation levels (1% and 10% v/v) to produce double-fermentation kefir products. These products exhibited higher counts of lactic acid bacteria and reduced yeast populations compared with traditional grain kefir. After 15 days of storage, all kefir samples maintained more than 10⁸ CFU/mL of lactic acid bacteria, more than 10⁷ CFU/mL of acetic acid bacteria, and around 10⁵ CFU/mL of yeasts. Protein content was comparable among all kefir products and unfermented milk. The product obtained with 1% grains followed by 10% v/v inoculation showed enhanced biofilm formation that increased during storage and displayed the strongest antimicrobial activity, and was therefore selected for sensory evaluation, where it achieved favorable acceptance by regular kefir consumers. Full article

Fermented beverages have been highlighted for their beneficial effects on health, especially due to the presence of probiotic microorganisms. This study aimed to develop and characterize a beverage fermented from the aqueous extract of licuri (Syagrus coronata) with grains of milk kefir and water kefir. Physical–chemical properties, microbial viability, storage stability, and in vitro resistance to the gastrointestinal tract (GIT), as well as microbiological safety and identification of isolated bacteria, were evaluated. The grains were fermented in licuri for 24 and 48 h, and the samples were compared with their respective controls. The analyses revealed that the licuri drink favored the growth of kefir grains, maintaining adequate microbial viability (>7 log CFU mL⁻¹ for lactic acid bacteria and >4 log CFU mL⁻¹ for yeasts), with good resistance to GIT (>60%) and physical–chemical properties for 20 days. The bacterial isolate was identified as Lacticaseibacillus paracasei, with a satisfactory safety profile. Licuri extract is therefore a promising matrix for the development of non-dairy functional beverages with potential probiotic properties. Full article

Dairy products harbor complex and dynamic microbial communities that contribute to their sensory properties, safety, and cultural distinctiveness. Raw milk contains a diverse microbiota shaped by seasonality, storage conditions, lactation stage, animal health, farm management, and genetics, serving as a variable starting point for further processing. Fermentation, whether spontaneous or starter driven, selects for subsets of lactic acid bacteria (LAB), yeasts, and molds, resulting in microbial succession that underpins both artisanal and industrial products such as kefir and cheese. Kefir represents a balanced LAB–yeast symbiosis, with species composition influenced by grain origin, milk type, and processing parameters, whereas the cheese microbiota reflects the interplay of starter and non-starter LAB, coagulants, ripening conditions, and “house microbiota”. Methodological factors—including DNA extraction, sequencing platform, and bioinformatic pipelines—further impact the reported microbial profiles, highlighting the need for standardization across studies. This review synthesizes current knowledge on raw milk, kefir, and cheese microbiomes, emphasizing the biological, technological, environmental, and methodological factors shaping microbial diversity. A holistic understanding of these drivers is essential to preserve product authenticity, ensure safety, and harness microbial resources for innovation in dairy biotechnology. Full article

Kefir is a fermented dairy product whose structural properties can be modified to enhance its nutritional and sensory profile. The objective of this study was to develop spoonable milk kefir gels by optimizing fermentation conditions and incorporating psyllium and calcium chloride as structuring agents. In the initial phase of the study, a full factorial design was employed to conduct a comparative analysis of whole milk and skimmed milk during the fermentation process of kefir. The study encompassed the evaluation of the impact of various parameters, including inoculum level, temperature, and fermentation time, on the acidification kinetics of the fermentation process. This evaluation was facilitated through the measurement of pH and total acidity levels. Skimmed milk demonstrated accelerated acidification, consistently attaining a final pH of 4.08 and a total acidity of 9.99 g·L⁻¹ lactic acid equivalents under optimized conditions (5.5% weight:weight grains, 26 °C, 24 h). In the subsequent phase, kefir obtained under these conditions was gelled with varying concentrations of psyllium and calcium chloride. Rheological characterization revealed that psyllium markedly strengthened the gel network: at 3.06% w:w psyllium, the elastic modulus increased up to 209.6 Pa, while the critical stress improved from 0.64 Pa at low psyllium/Ca²⁺ to 10.42 Pa at high psyllium content. Furthermore, zero-shear viscosity increased substantially, exceeding 1500 Pa·s in high-psyllium, low-calcium formulations. The findings demonstrate that combining fermentation optimization with clean-label structuring agents enables the development of low-fat kefir gels with enhanced textural and processing properties, supporting their potential as synbiotic, functional dairy products. Full article

Microbial detoxification, as an environmentally friendly strategy, has been widely applied for benzo[a]pyrene (BaP) degradation. Within this approach, food-derived microbial strains offer unique advantages in safety, specificity, and sustainability for detoxifying food-borne BaP. In this study, we aimed to explore the potential of such strains in BaP degradation. Bacillus mojavensis TC-5, a strain that degrades BaP, was isolated from kefir grains. Surprisingly, 12 genes encoding dehydrogenases, synthases, and oxygenases, including betB, fabHB, qdoI, cdoA, and bioI, which are related to BaP degradation, were up-regulated by 2.01-fold to 4.52-fold in TC-5. Two potential degradation pathways were deduced. In pathway I, dioxygenase, betaine aldehyde dehydrogenase, and beta-ketoacyl-ACP synthase III FabHB act sequentially on BaP to form 4H-pyran-4-one,2,3-dihydro-3,5-dihydroxy-6-methyl via the phthalic acid pathway. In the presence of the cytochrome P450 enzyme, BaP progressively mediates ring cleavage via the anthracene pathway, eventually forming 3-methyl-5-propylnonane in pathway II. Notably, TC-5 achieved an impressive BaP removal efficiency of up to 63.94%, with a degradation efficiency of 32.89%. These results suggest that TC-5 has significant potential for application in addressing food-borne BaP contamination. Moreover, our findings expand the application possibilities of Xinjiang fermented milk products and add to the available green strategies for BaP degradation in food systems. Full article

Kefiran, the extracellular polysaccharide produced from the Generally Recognized as Safe (GRAS) bacteria in kefir grains, with its well-documented functional and health-promoting properties, constitutes a promising biopolymer with a variety of possible uses. Its compatibility with other biopolymers, such as milk proteins, and its ability to form standalone cryogels allow it to be utilized for the fabrication of films with improved properties for applications in the food and biomedical–pharmaceutical industries. In the present work, the properties of kefiran films were investigated in the presence of milk proteins (sodium caseinate, native and heat-treated whey proteins, and their mixtures), alongside glycerol (as a plasticizer) and cryo-treatment of the film-forming solution prior to drying. A total of 24 kefiran films were fabricated and studied for their physical (thickness, moisture content, water solubility, color parameters and vapor adsorption), mechanical (tensile strength and elongation at break), and optical properties. Milk proteins increased film thickness, solubility and tensile strength and reduced water vapor adsorption. The hygroscopic effect of glycerol was mitigated in the presence of milk proteins and/or the application of cryo-treatment. Glycerol was the most effective at reducing the films’ opacity. Heat treatment of whey proteins proved to be the most effective in increasing film tensile strength, reducing, at the same time, the elongation at break, while sodium caseinates in combination with cryo-treatment resulted in films with high tensile strength and the highest elongation at break. Cryo-treatment, carried out in the present study through freezing followed by gradual thawing of the film-forming solution, proved to be the most effective factor in decreasing film roughness. Based on our results, proper selection of the film-forming solution composition and its treatment prior to drying can result in kefiran–glycerol films with favorable properties for particular applications. Full article

This study analyzes the aromatic profiles of kiwi-based fermented beverages, inoculated with varying proportions of milk kefir grains and incubated under different shaking rates. The experiments were designed using response surface methodology and three consecutive batch cultures were performed under each experimental condition. At the end of each fermentation, the grains were separated from the beverage and reused as the inoculum for fermenting fresh kiwi juice in the subsequent batch. Based on the results, together with the previously determined microbiological and chemical characteristics, two beverages were identified as having broader aromatic profiles, lower contents of sugars, ethanol, and acids, and high counts of lactic acid bacteria (LAB) and yeasts (>10⁶ CFU/mL). These beverages were produced under relatively low agitation rates (38 and 86 rpm) and high inoculum proportions (4.33% and 4.68% w/v) during the second and third batch cultures, respectively. Over 28 days of refrigerated storage, the pH values of both beverages remained relatively stable, and the LAB counts consistently exceeded 10⁶ CFU/mL. Yeast counts, along with the production of ethanol, glycerol, lactic acid, and acetic acid, increased slightly over time. In contrast, the concentrations of citric acid, quinic acid, total sugars, and acetic acid bacteria declined by day 28. Full article

This study aimed to manufacture kefir from camel milk using an extensive production system with different amounts of kefir grains, as well as to highlight their nutritional, sensorial, and technological characteristics. During processing, the pasteurization of camel milk, the addition of three doses of kefir grains (2%, 5%, and 10%), and incubation for 18 h were carried out. The microbiological and nutritional properties of the camel milk, kefir grains, and resulting kefirs were assessed. The sensory evaluation and technological processes involved in the production of the selected kefir were then carried out. The results showed that the chemical composition of the camel milk was as follows: fat: 41.7 ± 3.18 g/L; protein content: 37.82 ± 0.66 g/L; ash: 8.92 ± 0.61 g/L; dry matter: 114.21 ± 0.11 g/L; and lactose: 41.3 ± 0.21 g/L. Kefir grains were acidic and moist and contained low fat content (0.02 ± 0.01). The total aerobic flora in camel milk was FAMT 4.77 × 10⁴ CFU/mL. The bacterial load of lactic acid bacteria in the camel kefir prepared with 10% kefir grains was 5.1 ± 0.6 log₁₀ CFU/mL, while the yeast and mold load was 4.24 ± 0.83 log₁₀ CFU/mL. The amount of kefir grains present had a significant effect (p < 0.05) on pH, acidity, and viscosity and improved the protein content, resulting in higher nutritional quality. According to a sensory evaluation, the ranking test showed that the best camel kefir can be produced by the addition of 2% kefir grains. It was the most appreciated by 73% of the tasters based on its physicochemical, microbiological, and sensory characteristics. All obtained camel kefirs were able to fulfill the Codex Alimentarius requirements, ensuring their safety and quality, with overall improvements in taste, texture, and acceptability. A phenotypic and morphological study of lactic acid bacteria isolated from the selected kefir (CK 2%, 18H) showed that these bacteria are Gram+, citrate+, catalase−, shell−, and rod-shaped. All the strains isolated showed good lipolytic and proteolytic activity, with areas of proteolysis between 8 and 15 mm. These strains were also revealed to have antibacterial activity and good acidifying and texturizing effects. Full article