Kefir Research Articles

From Milk Kefir to Water Kefir: Assessment of Fermentation Processes, Microbial Changes and Evaluation of the Produced Beverages

The aim of the present study was to investigate the feasibly of using traditional milk kefir grains for the production of water kefir-like beverages and assess the changes in the physicochemical characteristics and the microbial populations of the fermented beverages. To this end, experiments of milk fermentation were primarily conducted at different temperatures and upon selection of the optimal, a gradual substitution of the substrate was performed by replacing milk from a sucrose-based solution. After the successful fermentation of the sucrose substrate, fruit juices were used as fermentation substrates. Sensory evaluation of the sugar-based beverages was also performed in order to access their acceptability for consumption. According to the results, the transition from milk to water kefir is indeed feasible, leading to the production of beverages with relatively higher ethanol concentrations (up to 2.14 ± 0.12% w/v) than milk kefir and much lower lactic acid concentrations (up to 0.16 ± 0.01% w/v). During the fermentation of the sugary substrates, yeasts seemed to be dominant over lactic acid bacteria, in contrast to what was observed in the case of milk kefir, where LAB dominated. The sensory evaluation revealed that all sugar-based beverages were acceptable for consumption, with the fruit-based ones obtaining, though, a better score in all attributes.

Survival of some food-borne bacteria in kefir produced by microbial levan and pullulan

Kefir is a fermented milk product produced by kefir grains traditionally or lyophilized starter culture. Some quality characteristics of kefir produced at 22 °C and 30 °C using kefir grains after addition of microbial levan and pullulan were investigated for 14 days. Additionally, the survival of different Gram-positive and Gram-negative bacteria strains which were inoculated before and after fermentation were investigated during storage. The pH and titratable acidity were in the ranges of 4.67–4.39 and 1.10–0.87%, respectively. The highest exopolysaccharide values (458.3–465.3 mg/kg) were found in the samples produced with the addition of 1% (w/v) of microbial levan at 30 °C. Yeast counts were in the ranges of 6.73–5.11 log CFU/mL while the lactobacilli and lactic streptococci counts were in the ranges of 9.64–7.91 and 9.64–8.69 log CFU/mL, respectively. The microbial polysaccharide addition did not show any significant differences in the enumeration of lactic acid bacteria in kefir (p > 0.05). All Gram-positive and Gram-negative bacteria grew/survived during fermentation however Listeria monocytogenes was the most susceptible test bacterium to metabolites during storage. The highest reduction in the counts of L. monocytogenes was determined as 2.39 log units after 24 h of fermentation at 30 °C in the samples which were inoculated before fermentation and produced with the addition of pullulan. Kefir samples produced at 30 °C without polysaccharide addition were considered as the best with respect to appearance, taste, consistency and overall acceptability.

Determination and standardization of the kefiran extraction protocol for possible pharmacological applications

The use of biopolymers in medicine and pharmacology is of great scientific, technological, and commercial interest. A possibility of biopolymer for use in pharmacological applications is the kefiran, an exopolysaccharide (EPS) produced by bacteria that form kefir grains during the milk fermentation process in which the grains are growing. The EPS extraction method can modify its concentration and structure. To establish the most appropriate kefiran extraction protocol and standardize this method, three different extraction processes were evaluated, which differ in the boiling times and in the presence (or not) of agitation. Kefiran obtained by different methods were characterized by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), electron scanning field emission microscopy (FESEM), and determination of antimicrobial potential. The samples showed differences in yield, chemical composition, degree of purity, thermal properties, and antimicrobial capacity. The results analyzed indicated that extraction protocol 1 (EP 1) with a longer heating time and constant agitation was able to provide the best thermal resistance, with a high degree of purity (93%), and yield (22.18 mg of kefiran obtained for each gram of kefir grains used). In addition, this method provides good biological activity as a potential antimicrobial agent and can be a potential biopolymer for pharmacological application.

Evaluation of the application of water kefir grains in the decolouration of solutions containg textile dye

One of the main environmental problems presented by the textile industry is the generation of effluents containing synthetic dyes. Because of that, studies have been carried out in order to remove or degrade the dyes present in wastewater and thus, the adsorption process in polymeric matrices has been highlighted due to its low cost and high efficiency in bioremediation. In this context, it was verified the potential of biodegradation of the anthraquinone C. I. Reactive Blue 4 HFG textile dye (Dianativo®) by water kefir grains, as well as the application of the insoluble exopolysaccharide produced by the grains as an adsorbent of the dye, evaluating the effect of pH and initial concentration of dyes in the reduction of staining in a model system. The grains and their insoluble polysaccharide matrix were presented as capable of decolourizing dye solutions under the evaluated conditions, reducing the dye concentration in the solution by up to 92%.

Effect of substrates on the kefir grain biomass production and antioxidant activity

ABSTRACT
 Kefir is a fermented milk with proven bioactivities and popularity worldwide. However, kefir grains biomass (KGB) limits its production. The effect of different substrates on the KGB increase and antioxidant activity (AC) was investigated. Kefir grains were inoculated (6 % w/v) into nonfat goat milk (GMK), nonfat goat milk with brown sugar (GMBSK), cow (1 % fat) milk (CMK), and cow milk brown sugar (CMBSK). The substrates were fermented at 25 ± 3 °C and stopped at 4.7 pH, approximately. Samples were taken at 0, 4 and 8 h incubation time. KGB increase kinetics, productivity, growth rate parameters, physicochemical composition changes, and antioxidant activity were evaluated. Goat milk substrates kefirs had the highest AC values. GMBSK and GMK had 44.8 ± 1.4 % and 37.6 ± 3.6 % AC, respectively. GMK and GMBSK had the highest biomass increments, 147 ± 23 % and 136 ± 7 %, respectively. Also, GMK had the highest (p < 0.01) kefir grains biomass productivity, 2.49 ± 0.24 g/L.h. Goat milk substrate has the potential to increase kefir grains biomass and to improve the bioactivity of kefir beverages.

Characterization of Tibetan kefir grain-fermented milk whey and its suppression of melanin synthesis

Tibetan kefir grain as the starter of milk fermentation has been applied as functional food with many bioactive characteristics. In this study, the milk whey product (TKG-MW) was obtained through the milk fermentation of Tibetan kefir grain containing the dominant Lactobacillus, Acetobacter, and Bacillus after 3 and 6 days of cultivation. Antioxidant, anti-inflammatory, and melanogenesis inhibition capacities under TKG-MW treatment were analyzed. Results revealed that the antioxidation of TKG-MW at 6 days of fermentation was higher than that at 3 days of fermentation according to the DPPHand ABTS+ radical scavenging analysis. However, the anti-inflammation of TKG-MW was only observed at 6 days of fermentation by using lipopolysaccharide-stimulated RAW 264.7 macrophages. The inhibition of mushroom tyrosinase activity by TKG-MW was demonstrated. The decrease of melanin content was verified using α-melanocyte-stimulating hormone-stimulated B16-F10cell. The real-time quantitative reverse transcription polymerase chain reaction result indicated that the mRNA levels of Tyr, Trp-1, and Trp-2 of the B16cell involved in melanin synthesis were down-regulated over a two-fold change by the TKG-MW treatment. Additionally, the protein expressions of Tyr, Trp-1, Trp-2, and Mitf of the B16cell were reduced with the TKG-MW treatment. Organic acids, such as lactic acid, succinic acid, 3-phenyllactic acid, l-pyroglutamic acid, and malic acid, were identified by liquid chromatography-mass spectrometry in TKG-MW and were found to significantly inhibit tyrosinase activity. To the best of our knowledge, this work is the first to report melanogenesis suppression by TKG-MW. Results suggested that the fermentation product of TKG could be applied as a depigmenting agent in food and cosmetics.

Functional Properties of Kefiran in the Medical Field and Food Industry.

Kefir is produced through the fermentation of milk using kefir grain as a starter culture. Kefir grains include heterogeneous microorganisms embedded in a polysaccharide matrix called kefiran which is considered a biofilm; it also has many uses due to its therapeutic values. Kefiran is a microbial exopolysaccharide (EPS) obtained from the flora (acid-lactic bacteria and yeasts) of kefir grains and glucose units, in almost the same proportion. Kefiran has prebiotic nature agitating the growth of probiotics in the gastrointestinal tract of the human entity. It extends certain therapeutic benefits by balancing the microbiota in the intestine. This review presents the most recent advances regarding kefir and kefiran, their cultural condition, biological activities, and potential applications in the health and food industries.

Comparative Analysis of Fermentation Conditions on the Increase of Biomass and Morphology of Milk Kefir Grains

Kefir grains represent a symbiotic association group of yeasts, lactic acid bacteria and acetic acid bacteria within an exopolysaccharide and protein matrix known as kefiran. The mechanism of growth of a biomass of kefir after successive fermentations and optimal conditions is not well understood yet. Biomass growth kinetics were determined to evaluate the effects of temperatures (10 °C to 40 °C) and different substrates, such as monosaccharides (fructose, galactose, glucose), disaccharides (lactose, saccharose) and polysaccharides (Agave angustifolia fructans) at 2%, in reconstituted nonfat milk powder at 10% (w/v) and inoculated with 2% of milk kefir grain (105 CFU/g), after determining the pH kinetics. The best conditions of temperature and substrates were 20 °C and fructans and galactose. An increase in cells, grain sizes and a change in the morphology of the granules with the best substrates were observed using environmental scanning electron microscopy, confocal laser scanning microscopy and Image Digital Analysis (IDA). Kefir grains with agave fructans as their carbon source showed the higher fractal dimension (2.380), related to a greater co-aggregation ability of LAB and yeasts, and increase the formation of exopolysaccharides and the size of the kefir grains, which opens new application possibilities for the use of branched fructans as a substrate for the fermentation of milk kefir grains for the enhancement of cellular biomasses and exopolysaccharide production, as well as IDA as a characterization tool.

Lacticaseibacillus rhamnosus GG Survival and Quality Parameters in Kefir Produced from Kefir Grains and Natural Kefir Starter Culture.

The study aimed to determine the effect of starter cultures (kefir grains and natural kefir starter culture without grains) on Lacticaseibacillus rhamnosus GG (LGG) survival and on the quality characteristics of kefir. To this end, the viability of probiotic L. rhamnosus GG strain and the rheological properties and quality parameters of kefir beverages were tested during storage over 21 days at 4 °C. The final LGG counts were 7.71 and 7.55 log cfu/mL in natural kefir starter culture and kefir grain, respectively. When prepared with probiotic bacteria, the syneresis values of kefir prepared using natural kefir starter culture was significantly lower (p < 0.05) than that of kefir made using grains. However, the viscosity indices, hysteresis loop, and dynamic moduli were similar between kefir made with natural kefir starter culture and other kefir formulations (p > 0.05). Moreover, all samples showed shear-thinning behavior. The flavor scores for kefir prepared using natural kefir starter culture were significantly higher than for the other samples (p < 0.05), but overall acceptability was similar at the 10-day assessment across both starters (with and without grain) after the addition of probiotic bacteria (p > 0.05). Overall, the results indicate that natural kefir starter culture could be a potential probiotic carrier.

Recent developments in dairy kefir-derived lactic acid bacteria and their health benefits

Kefir is one of the most consumed traditional fermented dairy products and it has a complex probiotic and nutritional composition. Kefir grain contains casein and other milk solids together with the yeasts and lactobacilli that cause the characteristic kefir fermentation and serve as a starter to induce this fermentation when introduced into fresh milk. Both kefir and kefir grains have a rich microbiota and their composition is affected by many parameters like kefir origin, production method (artisanal or industrial), kefir grain: milk ratio, type of milk, fermentation conditions, inoculum source, equipment used in production and storage conditions. Lactic acid bacteria (LAB) are a significant part of the kefir's microbial composition and the health-promoting effects. Kefir-derived LAB have beneficial effects on colorectal cancer, cardiovascular diseases, type 2 diabetes mellitus, obesity, kidney diseases, modulation of the immune system as well as intestinal microbiota through different biological mechanisms. In addition, bioactive peptides and metabolic products of kefir have shown promising results as health beneficial components along with certain antiviral effects including COVID-19. Therefore, this article is up-to-date information about the production, processing as well as health benefits of dairy kefir-derived LAB with future prospect of work.

Aflatoxin M1 reduction by microorganisms isolated from kefir grains

Aflatoxin M1 (AFM1) is a mycotoxin that often contaminates milk. Like other mycotoxins, it is thermostable and potentially carcinogenic. The present work was carried out to evaluate the ability of microorganisms isolated from Indonesian kefir grains to reduce AFM1 in contaminated phosphate buffer saline (PBS). Fourteen isolates of lactic acid bacteria, both aerobic (LAE) and anaerobic (LAN), and nine isolates of yeast (YEA) were used. The significantly highest AFM1 reduction percentage was shown by the isolate LAE7 (29.3 ± 0.6%) after 4 h incubation. DNA sequencing of LAE7 and YEA2 isolates showed that these isolates had homology (level of similarity) with species of Lactobacillus kefiri strain A/K and Saccharomyces cerevisiae NRRL Y-12632, respectively. The present work proved that isolates from Indonesian kefir grains could reduce AFM1 and have the potential for practical use.

THE MAKING OF RICE BRAN FLOUR-BASED SOURDOUGH BREAD

Sourdough is a bread made with the involvement of Lactobacillus bacteria and yeast that are naturally present in wheat flour. This study used rice bran and milk kefir grains to speed up the preparation of starters. Rice bran is used to reduce gluten content in bread as well as add nutritional value to bread. This research aims to determine the impact of the concentration of rice bran flour (0, 25, and 50% w/w of total flour) on the physical, chemical, and organoleptic parameters of sourdough. An increase in the rice bran flour concentration leads to an increase in the pH, hardness and brittleness of the bread. Besides, it also causes a decrease in lactic acid levels and bread expansion volume which makes the bread taste less sour. The results of the organoleptic analysis showed that sourdough with a concentration of 25% rice bran flour was the most preferred bread, as it is less sweet, without sour and bitter taste and a little bit salty. Moreover, it has a less unpleasant aftertaste, non-sour aroma, brown colour and it is not too soft in texture.

Black Cumin (Nigella sativa L.) Seed Press Cake as a Novel Material for the Development of New Non-Dairy Beverage Fermented with Kefir Grains.

In recent years, there has been a growing interest from the food industry in new products that are increasingly desired by consumers because of the functional ingredients they contain. This category certainly includes fermented plant-based beverages, which combine the properties of plant substrates with the beneficial effects of fermentation on human health. In our study, two trial variants containing 20% and 30% black cumin (Nigella sativa L.) seed press cake (BCPC) were inoculated with kefir grain cultures and then incubated at 25 °C for 24 h. The resulting beverages were stored under refrigeration (6 °C) for 28 days. During storage, pH, total free amino acids, reducing sugars, changes in the microbial population, viscosity, textural parameters, and color were measured on days 1, 5, 7, 14, 21, and 28. Throughout the storage period, the number of lactic acid bacteria, as well as yeasts, exceeded the recommended minimum level. Numerous changes in product parameters were observed in the tested beverages as a result of fermentation compared to non-fermented products. This study indicates the possibility of using BCPC as a valuable matrix for the production of a functional kefir-like beverage.

Prominent strains of kefir grains in the formation of volatile compound profile in milk medium; the role of Lactobacillus kefiranofaciens subsp. kefiranofaciens, Lentilactobacillus kefiri and Lentilactobacillus parakefiri

Prominent strains of kefir grains in the formation of volatile compound profile in milk medium; the role of Lactobacillus kefiranofaciens subsp. kefiranofaciens, Lentilactobacillus kefiri and Lentilactobacillus parakefiri

Surface dynamics, fractal features, and micromorphology analysis of kefir biofilms.

We introduce a study of image analysis of kefir biofilms associated with Acai extract prepared by fermentation of fresh kefir grains natural. Atomic force microscopy data were studied, aiming to understand how the concentration of acai berry (Euterpe oleracea Mart.) influences the surface morphology as well as the texture complexity, evaluated by the fractal dimension. The results showed that the superficial morphology was affected by the increase of Acai concentration in the biofilms, as well as the fractal dimension. It has also been observed that the surface of the biofilm presented saturation when concentration changes from 40 to 60 ml. On the other hand, it was observed that the intermediate sample produced with 20 ml of acai berry seems to be the best point for biofilms production that can serve as a skin dressing since other studies related to mechanical properties and in vitro and in vivo tests can confirm this applicability. Thus, the characterization of the surface morphology of kefir biofilms by the evaluation of surface statistical parameters and fractal geometry may provide promising results regarding the applicability of these films. RESEARCH HIGHLIGHTS: We characterized the structural complexity of the 3-D surface of the kefir biofilms associated with açaí extract. The 3-D surface analysis of the samples was performed using an atomic force microscope operating in contact mode. We determined the stereometric and fractal dimension of the analyzed samples.

Rheological properties and microbiological characteristics of kefir produced from different milk types

Kefir is a refreshing fermented dairy product which has flowing consistency, uniform and bright appearance with mild yeast taste and flavor. Traditional or industrial methods can be applied for the production of kefir using kefir grains or lyophilized culture. Changes in product rheology caused by the using different types of milk and different incubation temperatures in kefir production are effective on selecting the equipment such as pump, pipeline, mixer, filling machine. In this study, microbiological flora and rheological properties of kefir were investigated for cow, sheep or goat milks with kefir grain or lyophilized culture. The pasteurized cow, sheep and goat milk were cooled to 28 °C and fermented with kefir grain and incubated at 20 °C, 25 °C or 30 °C for 24 hours. Then, the grains were filtered and stored at + 4 °C for 24 hours. At the end of the storage period, rheological and microbiological analyzes were carried out on kefir samples. The same procedures and analyzes were carried out lyophilized culture. It was found that the incubation application at different temperatures was effective on the consistency coefficient even in the fluid type unchangeable samples.

SYNBIOTIC FUNCTIONAL DRINK FROM COW MILK FERMENTED WITH KEFIR AND SUPPLEMENTED WITH INULIN

Increasing awareness on health has increased demand for healthy food confirmed by raising market sales of functional food. This study aims to develop a new synergetic drink from cow milk fermented by kefir grains and supplemented by inulin. Firstly, the inulin was isolated from dahlia flower tuber while fresh cow milk was incubated with kefir grains to produce kefir probiotic drink. Next, inulin with different concentrations was added to the probiotic drink and was fermented for 48 hours at room temperature generating a symbiotic functional drink. Analysis of antimicrobial properties revealed that synbiotic drinks have antimicrobial activity and the colony unit bacteria was met the standard to be claimed as a probiotic supplement. The microbiology and physicochemical properties of kefir synbiotic drink were analyzed and the result showed better properties than the control. There was no significant difference in taste between control and kefir enriched inulin drink assessed by the panelist. Only kefir synbiotic drink supplemented by inulin of 3 and 5% determined has a significant difference in aroma. Based on that kefir enriched inulin drink has the potency to be used as a functional drink that has a synergistic combination of prebiotics and probiotics.

Water Kefir Grains - Microbial Biomass Source for Carbonaceous Materials Used as Sulfur-Host Cathode in Li-S Batteries

Water Kefir Grains - Microbial Biomass Source for Carbonaceous Materials Used as Sulfur-Host Cathode in Li-S Batteries

Lactobacillus kefiranofaciens JKSP109 and Saccharomyces cerevisiae JKSP39 isolated from Tibetan kefir grain co-alleviated AOM/DSS induced inflammation and colorectal carcinogenesis.

This study aimed to investigate the alleviative effects of Lactobacillus kefiranofaciens JKSP109 (LK) and Saccharomyces cerevisiae JKSP39 (SC) isolated from Tibetan kefir grain on colon inflammation and colorectal carcinogenesis. Azoxymethane (AOM) and dextran sulfate sodium (DSS) were used to establish a mouse model of colorectal cancer (CRC). The treatment group mice were administered with LK, SC, or the combination of LK and SC for five days per week from the day of receiving AOM. The composition of the gut microbiota was assessed using internal transcribed spacer 2 and 16S rRNA gene high-throughput sequencing. Furthermore, the biomarkers associated with gut barrier integrity, inflammation, regulators of cell proliferation, and apoptosis were evaluated. The results showed that the administration of LK, SC, and their combination increased the body weights and decreased the disease activity index (DAI) score and tumor multiplicity. As compared to the CRC model group, the three treatment groups positively regulated the gut microbiota. Meanwhile, the three treatments also enhanced the gut barrier, decreased the expression of proinflammatory cytokines and oncocyte proliferation indicators, and increased the expression of terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL)-positive tumor epithelial cells and content of short chain fatty acids in fecal samples. All these results indicated that the LK and SC alleviated the inflammation and colorectal carcinogenesis in AOM/DSS-induced CRC mouse models, and the majority of tested indexes in the combination group were superior to single strain groups.

Antimikrobna aktivnost i senzorna prihvatljivosti napitka na bazi fermentisane kozije surutke - optimizacija procesnih uslova metodom odzivnih površina

Even though it contains high levels of many important nutritive compounds, whey has not been widely accepted by consumers due to its unappealing taste and texture. Whey fermentation could improve its sensory properties and result in a functional beverage with appealing characteristics and a clear potential to replace traditional functional milk-based beverages. Therefore, this work aimed to develop a goat whey-based functional beverage fermented with kefir grains and to examine the influence of fermentation temperature and inoculum size on the overall sensorial acceptability of the product and its antimicrobial activity. Response surface methodology along with the central composite design was used to estimate the individual and combined effect of temperature and inoculum size on lactic and acetic acid, ethanol, antimicrobial activity and overall sensory acceptability of the obtained beverage. The experimental data for lactic and acetic acid, antimicrobial activity and overall sensory acceptance of beverage were fitted to a quadratic model, while a linear 2FI model was proposed for the ethanol content. Temperature and inoculum size have been found to affect the quality of the obtained beverage. Multi-response optimization provided an optimum solution for the production of the most acceptable beverage with the highest antimicrobial activity. According to desirability criteria, with overall desirability of 0.79, the following fermentation conditions were proposed for the fermentation of goat whey using kefir: temperature of 27.5 ° C and inoculum size of 7.36%. Proposed values were validated confirming the minimum deviation of experimental and predicted values.