Search Results (141)

This study examined Kefiran, an exopolysaccharide derived from milk kefir grains, as a novel biopolymer for encapsulating phenolic extracts from sunflower cake and its antimicrobial properties in the development of natural and functional food ingredients. Kefiran was obtained from kefir grains using three extraction protocols: hot water (M1), hot water with 30% trichloroacetic acid (M2), and mild heat combined with ultrasound at 60 °C (M3). The ultrasound-assisted method produced the highest carbohydrate concentration. Spectrophotometric assays (phenol–sulfuric and Bradford), Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and water-holding capacity were employed to characterize the composition, structure, and morphology of the extracts, revealing well-preserved polysaccharide fingerprints and a highly porous microstructure, consistent with their potential application in food systems. Kefiran was then evaluated as an encapsulating agent in complex coacervation at pH 3.75, using three Kefiran-based wall formulations (M1, M2, and M3) with gum arabic and whey protein isolate (WPI) as co-wall materials, and their performance was compared with gum arabic and WPI controls. Across formulations, coacervate microcapsules achieved high encapsulation efficiencies (83–93%), tunable particle sizes, and predominantly negative zeta potentials, indicative of good colloidal stability. The Kefiran extract and coacervate microcapsules demonstrated significant antioxidant and antimicrobial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans, with minimum inhibitory concentrations ranging from 250 to 1000 µg/mL. The findings support ultrasound-extracted Kefiran as a multifunctional biopolymer suitable for bioactive delivery and as a natural antimicrobial component in advanced functional food formulations. Full article

Probiotic yeasts are increasingly proposed as adjuncts in fermented dairy products, but their behavior in kefir is still poorly described. This proof-of-concept study examined the effect of Saccharomyces boulardii CNCM I-745 supplementation on kefir produced with two traditional grain cultures and two industrial direct-vat-inoculation cultures during 21 days of cold storage at 4 °C. Microbiological, physicochemical, and sensory parameters were monitored on days 1, 7, 14, and 21. The starter culture type was the main source of variation, with traditional grain kefirs showing higher microbial counts and better sensory scores than industrial cultures. S. boulardii did not change pH, titratable acidity, Lactococcus spp., or total mesophilic aerobic bacteria, indicating that it can be added without disturbing the established kefir microbiota or its acidification pattern. The probiotic yeast increased the total yeast count, slightly modulated Lactobacillus spp., and gave a small improvement in taste–aroma scores. In the yeast-free industrial culture, S. boulardii maintained viable counts above 6 log CFU/g throughout storage, showing that it can act as the sole yeast source in kefir matrices that lack indigenous yeast. Traditional grain kefirs kept a more stable overall sensory quality across 21 days than industrial cultures. The multivariate analysis confirmed two largely independent quality dimensions, one related to lactic acid bacteria and acidity and another to sensory perception. The study supports the use of S. boulardii as a probiotic adjunct in kefir and provides preliminary effect-size information for future, adequately replicated trials. Full article

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

Foodborne diseases represent a major public health concern, particularly those associated with dairy products contaminated with Staphylococcus aureus, a pathogen capable of producing heat-stable enterotoxins. This study evaluated the potential of native lactic acid bacteria (LAB) isolated from artisanal kefir grains as natural biocontrol agents in fermented dairy foods. Kefir grains obtained from three artisanal producers were microbiologically characterized, revealing LAB as the dominant group and the absence of Enterobacteriaceae. Strains belonging mainly to the genera Lactobacillus sensu lato, Leuconostoc, and Pediococcus were isolated and exhibited differentiated metabolic profiles. Safety assessment showed no hemolytic activity and an overall susceptibility to clinically relevant antibiotics, although genus-dependent intrinsic resistance patterns were observed. Several strains displayed enzymatic activities related to carbohydrate digestion and high tolerance to simulated gastrointestinal conditions, with survival rates exceeding 90% during both gastric and intestinal phases. Neutralized cell-free supernatant (CFS) demonstrated differential inhibitory activity, with significant antagonism of S. aureus and E. coli, comparable to those of commercial reference strains. In a yogurt model system stored at 4 °C, selected Lactobacillus and Pediococcus strains induced a progressive and significant reduction in S. aureus populations, achieving complete elimination to undetectable levels in shorter times than commercial probiotic strains. Overall, these results demonstrate that native LAB from artisanal kefir grains exhibit an adequate safety and functional profile, together with strong antagonistic activity, supporting their potential application as natural protective cultures to improve the food hygiene of fermented dairy products. 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

Water kefir grains are complex probiotic granules that can efficiently ferment fruit and vegetable juices and significantly improve product flavor. However, the mechanisms of flavor formation remain unclear, which limits the process optimization of this technology. This study investigated the mechanisms involved in flavor formation during the fermentation of strawberry juice with water kefir grains. The results showed that as fermentation progressed, the total acidity increased, whereas the pH value and soluble solids content decreased. Additionally, the contents of citric acid and malic acid gradually decreased with fermentation, while the contents of lactic, acetic, and succinic acid increased, and three soluble sugars showed reduced levels. A total of 218 volatile compounds were identified. Eight dominant bacterial genera and one dominant yeast species were detected. Significant correlations between some key microorganisms and flavor compounds were observed. Specifically, Lactiplantibacillus was positively correlated with hexyl acetate. Meanwhile, Gluconobacter and Acetobacter were positively correlated with methyl (Z,Z)-9,12-octadecadienoate, isoamyl acetate, etc. In contrast, LAB such as Lacticaseibacillus and Schleiferilactobacillus showed the opposite correlations with these key flavor compounds. Saccharomyces showed a positive correlation with ethyl palmitate, ethyl propionate, phenylsuccinic acid, and 1-pentanol. The main flavor compound metabolic pathways were predicted and they were significantly related with yeasts, acetic acid bacteria, and lactic acid bacteria. Overall, this study offers a theoretical basis for the directional regulation and optimization of the flavor quality of strawberry juice fermented with water kefir. 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

Obesity is a complex metabolic disorder characterized by excessive accumulation of adipose tissue, resulting from an imbalance between energy intake and expenditure. It is associated with an increased risk of chronic diseases such as type 2 diabetes, cardiovascular disease, and cancer. Kefiran is a water-soluble exopolysaccharide produced by lactic acid bacteria, Lactobacillus kefiranofaciens, in kefir grains, composed primarily of glucose and galactose. It has garnered scientific interest due to its antioxidant, anti-inflammatory, and antimicrobial properties. Rice Kefiran (RK) is a functional food made with culturing L. kefiranofaciens in a medium containing rice. It is standardized to contain at least 5 mg/g of kefiran. This study investigated the anti-obesity effect of RK on a high-fat diet (HFD)-induced obese mouse model. HFD-fed mice exhibited marked increases in body weight gain (10.3 g vs. 2.0 g in controls) and adipose tissue mass (2.4 g vs. 0.4 g in controls). RK administration significantly attenuated weight gain to 8.3 g and 6.0 g at doses of 10 and 50 mg/kg, respectively, and reduced adipose tissue mass to 2.2 g (RK10) and 1.7 g (RK50). Oral glucose tolerance testing revealed impaired glucose clearance in HFD-fed mice, with blood glucose levels of 403.5 mg/dL at 15 min and 314.6 mg/dL at 120 min, compared with 348.8 mg/dL and 232.2 mg/dL in controls. RK treatment improved glucose tolerance, particularly at 50 mg/kg, reducing glucose levels to 359.0 mg/dL at 15 min and 263.8 mg/dL at 120 min. Biochemical analyses demonstrated that RK significantly reduced serum total cholesterol (213.6 mg/dL in HFD vs. 178.0 and 184.0 mg/dL in RK10 and RK50), triglycerides (379.0 mg/dL in HFD vs. 228.8 and 234.6 mg/dL), and non-esterified fatty acids (0.89 mEq/mL in HFD vs. 0.54 and 0.35 mEq/mL), while phospholipid levels remained unchanged. Furthermore, RK increased serum nicotinamide phosphoribosyltransferase (NAMPT) levels from 15.8 ng/mL in HFD-fed mice to 30.0 and 50.0 ng/mL in the RK10 and RK50 groups, respectively, and restored hepatic NAD⁺/NADH ratios toward control levels (1.78 µmol/L in HFD vs. 1.90 µmol/L and 2.07 µmol/L in RK10 and RK50). Gene expression analysis showed that RK increased Nampt mRNA expression and decreased the mRNA expression of adipogenic and lipogenic genes, including Srebp-1c, Acc-1, and Fas. These findings suggest that RK may ameliorate obesity-related metabolic disturbances and its associated metabolic dysfunctions by modulating lipid metabolism, glucose tolerance, and NAD⁺ biosynthesis pathways. Full article

Water kefir is a non-dairy fermented water drink which includes lactic acid bacteria, acetic acid bacteria and yeasts which provide probiotic as well as antioxidant properties. Prunus armeniaca (apricot) is a promising raw material to develop a functional beverage because it is rich in carotenoids, vitamins, and phenolics. Coconut water is a natural hydrating substance and plant-based substrate. The aim of this study was to prepare and characterize apricot-coconut water kefir beverage, (ACWB) a fermented beverage having 20 g (w/v) dried apricot, 8 g (w/v) brown sugar, and 8 g (w/v) water kefir grains fermented together in 100 mL coconut water and compare its physicochemical, microbial, and antioxidant properties with a control sample excluded with dried apricot but having same concentration of rest of the ingredients. After fermentation, total soluble solids (TSS), pH, titratable acidity (TA), water activity (aw), total bacterial count (TBC), DPPH radical-scavenging activity, and total phenolic contents (TPC) were measured. ACWB exhibited significantly higher values (p < 0.05) in terms of TSS (10.07 ± 0.01 °Brix), TA (0.298 ± 0.01%), and TBC (1.92 × 10⁷ CFU/mL), with lower pH (3.98 ± 0.07) and aw (0.94 ± 0.02) compared to the control. Enhanced antioxidant activity (DPPH = 62.7 ± 0.86%) and TPC (19.92 ± 0.32 mg CE/100 mL) confirmed its superior bioactive potential. Sensory evaluation of ACWB also found it to be more preferred, with statistically significant difference in majority of the tested attributes. The apricot supplement enhanced the fermentation activity, microbial growth, as well as the antioxidant capacity of the end product, creating a stable, tangy, and nutritionally enriched non-dairy functional beverage that could be consumed by healthy and lactose intolerant consumers. 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

Extracellular vesicles (EVs) derived from probiotic bacteria have recently emerged as postbiotic mediators that regulate host cellular responses. This study investigated the effects of EVs from Lactobacillus rhamnosus BS-Pro-08, isolated from kefir grains (Lacto EV), on adipocyte differentiation and lipid metabolism. Lacto EV treatment markedly suppressed the differentiation of 3T3-L1 preadipocytes into mature adipocytes, as reflected by reduced lipid accumulation and decreased expression of the adipogenic transcription factors peroxisome proliferator-activated receptor γ (PPARγ) and CCAAT/enhancer-binding protein α (C/EBPα). This inhibitory effect was most pronounced at the early stage of adipogenesis. In mature adipocytes, Lacto EV enhanced lipolysis in a dose-dependent manner, accompanied by increased glycerol release and total lipase activity. Interestingly, these lipolytic responses occurred despite reduced protein levels of adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL), suggesting that Lacto EVs may mediate an EV-enhanced lipolysis that is not fully explained by canonical ATGL/HSL signaling. Collectively, these findings demonstrate that Lacto EV modulates both adipogenic and lipolytic processes in vitro, providing insight into the metabolic actions of probiotic-derived vesicles. 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