Kefir Research Articles

Microbiological profiles, physiochemical properties and volatile compounds of goat milk kefir fermented by reconstituted kefir grains

Kefir is a health-promoting fermented dairy products, consisting in a variety of bacterial and fungal species. The physical and chemical properties and the correlation between the microbiota and volatile compounds of goat milk kefir fermented by reconstituted kefir grains were investigated. Cluster analysis showed that a strong symbiotic homeostasis system existed in goat milk kefir, indicating that the composition of microorganism in reconstituted kefir grains was still restricted by the original one. Compared with other kefir samples, goat milk kefir 80DE20CN (ratios of kefir grains CN/DE = 80/20) showed significant improvement in physiochemical properties and “Fruity” flavor. Positive correlations among Lactobacillus helveticus and ethyl acetate, amyl acetate and ethanol, Kazachstania unispora and octyl formate, 1-heptanol and hexanoic acid were obtained by Partial least squares regression analysis (PLSR) model. The results showed that changes in microbial succession patterns may be useful to optimize the physiochemistry and flavor of goat milk kefir or related products.

Copper-Contaminated Substrate Biosorption by Penicillium sp. Isolated from Kefir Grains.

In this bioremediation study, the fungus Penicillium sp. isolated from kefir grains was evaluated for its resistance to copper in the culture medium. Penicillium sp. was cultivated in liquid medium prepared using 2% malt-agar at pH 7.0. Biomass of the fungus was significantly reduced, but only when 800 mg·L-1 of Cu(NO3)2 copper nitrate was used. The effect on radial growth of the fungus in experiments combining different pH values and the inorganic contaminant showed an inhibition of 73% at pH 4.0, 75% at pH 7.0 and 77% at pH 9.0 in liquid medium. Thus, even though the growth of Penicillium sp. could be inhibited with relatively high doses of copper nitrate, images obtained with scanning electron microscopy showed the preservation of fungal cell integrity. Therefore, it can be concluded that Penicillium sp. isolated from kefir grains can survive while performing bioremediation to minimize the negative effects of copper on the environment through biosorption.

Effects of fermentation with Kefir grains on nutrient composition, flavor volatiles, and product physical stability of a hemp seed (Cannabis sativa L.) beverage

This study investigated the effects of fermentation with kefir grains on the nutritional composition, flavor, and physical stability of hemp seed, and explored its potential as a probiotic plant-based beverage. After fermentation of a homogenized hemp seed water suspension, the concentrations of organic acids (lactic, acetic, tartaric, butyric, succinic, and malic acids) increased. The content of nutritional components, amino acids, and free fatty acids increased, as well as the number (from 16 to 21) and concentrations of flavor compounds, such as alcohols, acids, and esters. Fermentation also increased the particle size, viscosity, and phase-separation resistance of the final product. Therefore, kefir grains improved the nutritional composition, flavor, and physical stability of the hemp seed beverage, indicating its potential as a functional beverage, and providing a theoretical basis for the development of plant-based fermented beverages.

Metagenomic analysis and antibacterial activity of kefir microorganisms.

The microbiota composition of kefir grain and milk kefir was assessed via a metagenomic approach. Significant microorganisms were isolated and identified using molecular methods. A safety assessment was conducted based on antibiotic susceptibility and blood hemolysis. Probiotic traits such as resistance to gastric tract conditions, surface characteristics, adhesion to intestinal cells, and antibacterial activity were also assessed. Metagenomic analysis revealed that kefir grains are a more stable community with clear dominant species as compared to milk kefir. Lactobacillus kefiranofaciens BDGO-A1, Lactobacillus helveticus BDGO-AK2, and Lactobacillu kefiri strains showed tolerance to acidic pH and the presence of bile salts, adhesion capability to Caco-2 cells, in vitro antibacterial activity, and the production of antibacterial proteins. In the metagenomic analysis, contigs associated with these species showed the presence of genes involved in exporting polyketide antibiotics and bacteriocin production. To fully exploit the potential probiotic properties of these microorganisms to help human health, further investigation is necessary to elucidate the mechanisms behind the biological activity and the genotypic characteristics of the isolated strains.

Biotechnological Features of a Functional Non-Dairy Mixed Juice Fermented with Lacticaseibacillus paracasei SP5

In the present study, a wild-type Lacticaseibacillus paracasei SP5 (L. paracasei SP5) potential probiotic strain (previously isolated from kefir grains) was applied for the 1-day fermentation of an apple–orange–carrot mixed juice. After the fermentation, the mixed juice was refrigerated in cold storage at 4 °C, and the microbiological stability, characterization of volatiles, physicochemical properties (pH, total titratable acidity (TTA), residual sugar content and organic acids content), the sensorial validation (aroma, taste and overall acceptability) of the juice, and the viability of the potential probiotic strain were analyzed. The stored juice exhibited zero colonies of yeasts/fungi and simultaneously the viability of L. paracasei SP5 was retained to 8.28 Log CFU/mL, even after the 4th week of cold storage. The pH values ranged from 3.80 to 3.35 and the TTA values ranged from 0.1344% to 0.1844% lactic acid for the unfermented juice up until the 4th week of cold storage. Furthermore, the organic acids content consisted mostly of lactic acid (4.6 to 9.1 g/L), while malic acid (3.7 to 1.5 g/L), acetic acid (0.6 g/L) and propionic acid (0.3 g/L) were detected only after the 4th week of cold storage. Residual sugar content ranged from the initial value of 122.2 g/L and 106.6 g/L at the end of cold storage. As far as the volatiles’ characterization is concerned: 9 esters, 2 organic acids, 12 alcohols, 3 aldehydes, 1 ketone, 6 terpenes and 4 sesquiterpenes (37 in total) were detected in the unfermented mixed juice and 33 compounds in the fermented juice after 4 weeks of cold storage. The sensorial properties (aroma, taste and overall acceptability) of the fermented mixed juice samples were positively influenced. Consequently, L. paracasei SP5 potential probiotic strain may be applied for the production of probiotic mixed juices, with satisfying viability, volatile profile and organoleptic results.

Effects of Kefir Consumption on Cardiometabolic Risk Factors: A Systematic Review and Meta-analysis of Randomized Controlled Trials.

Fermentation of lactose in milk by bacteria and yeasts naturally present in kefir grains produces a beverage that has been suggested to have cardiovascular benefits. This systematic review and meta-analysis of randomized controlled trials (RCTs) aimed to evaluate the effects of this kefir beverage on cardiometabolic risk factors. Literature search utilised PubMed, Scopus, ISI Web of Science, and Google Scholar for articles published from inception until June 2021. Cardiometabolic risk indices extracted included insulin and insulin resistance (HOMA_IR), total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), fasting blood sugar (FBS), haemoglobin A1c (HbA1c) and body weight (BW). In total, six RCTs (314 subjects) were selected for the meta-analysis. Inverse-variance weighted mean difference (WMD) with a 95% confidence interval (CI) was calculated for the mean changes in TC, TG, HDL-C, LDL-C, FBS, HbA1c and BW compared to baseline. A random effects model was used to estimate the pooled WMD. Kefir intake significantly reduced fasting insulin (WMD: -3.69 micro-IU/mL,95% CI: -6.30 to -1.07, p = 0.006, I2 = 0.0%) and HOMA-IR (WMD: -2.56, 95% CI: -3.82 to -1.30, p<0.001, I2 = 19.4%). No effect on TC (p = 0.088), TG (p = 0.824), HDL-C (p = 0.491), LDL-C (p = 0.910), FBS (p = 0.267), HbA1c (p = 0.339) or body weight (p = 0.439) were found for kefir treatment. Kefir has a beneficial effect in decreasing insulin resistance; however, no effect was seen on BW, FBS, HbA1C, and lipid profile.

EFEK WAKTU AGING DAN PENGERINGAN VAKUM PADA ANALISIS PROKSIMAT DAN TINGKAT ASAM AMINO DARI KEFIR SUSU KAMBING

Goat milk kefir has high nutritional value, especially in protein and calcium content and has a low lactose content. Vacuum drying is an alternative to remove the water content in kefir so that it can extend the shelf life because it inhibits bacterial growth. This study determines the effect of aging time and drying time using vacuum drying method on the characteristics and amino acid composition of goat milk kefir (kefir and powder kefir). Fermented goat milk (24 hours) use kefir grains without aging and with aging times of 1, 2, 3, 4 (week). The total titrated acid and fat content were significantly different in kefir, but it is not significantly different in powder kefir. The yield, moisture, ash, protein, fiber, and fat in both kefir and powder kefir did not show significant differences. The best treatment based on the exponential comparison method for both powder kefir and kefir was 3 weeks of aging time. Therefore, the amino acid components in powder kefir and kefir underwent changes. The highest total amino acids in kefir was kefir without aging. The highest amino acid of powder kefir was obtained after 2 weeks of aging time.

Physico-Chemical, Microbiological and Sensory Properties of Water Kefir Drinks Produced from Demineralized Whey and Dimrit and Shiraz Grape Varieties.

Water kefir grains cannot grow in milk. Therefore, the aim of this study was to investigate whether water kefir grains can show activity in demineralized whey, an environment containing lactose as a carbon source. The physicochemical, microbiological and sensory properties of water kefir prepared from demineralized whey containing 2% and 5% lactose and raisins or grape juice from two grape varieties (Dimrit and Shiraz) were investigated. It was found that the protein content of the water kefir increased significantly (p < 0.05), especially when grape juice was added. The total soluble solids and viscosity of the samples with grape addition increased significantly (p < 0.05). Total phenolic content and antioxidant capacity increased significantly with grape addition (p < 0.05), with the effect of Shiraz grape being more pronounced. In general, it was found that the content of K, P, Na, Ca and Mg was higher in the samples with grape addition. The sensory properties of water kefir made from dWhey with 2% lactose and grape juice were better. It was also confirmed that viability of water kefir microbiota is better in water kefir drink made from dWhey with 2% lactose due to higher pH value in comparison to dWhey with 5% lactose.

Optimization of Coconut Milk Kefir Beverage by RSM and Screening of Its Metabolites and Peptides

Probiotic foods such as kefir drinks help to improve the health and well-being of consumers. Since Salmonella resistance to current antibiotic drugs is rising at an alarming rate worldwide, especially in Africa and Asia, this has raised the need for alternative ways of preventing and treating infectious diseases in humans and animals. Thus, a dairy-free probiotic drink can be an alternative for people with milk allergies or for those who avoid dairy products as a lifestyle choice. This study aims to optimize the quality of the coconut milk kefir drink for its antioxidant and antimicrobial activities and to identify the peptides and metabolites present. The time, temperature, and inoculum size that resulted in the optimal antioxidant and antimicrobial activities using Response Surface Methodology (RSM) were found to be 13.4 h, 25 °C, and 5.4 g/100 mL, respectively. The metabolic changes of coconut milk kefir at the beginning and end of fermentation were identified using 1H-NMR-based metabolomics. Some of the metabolites that were identified in the optimized product are γ-Aminobutyric acid, Biotin, Riboflavin, Butyrate, Lactate, and Caprylate. Moreover, 10 peptide sequences were identified using LC-MS/MS. The findings of this study demonstrated a high potential for coconut milk fermented using kefir grains as a functional healthy drink.

The Evaluation of Activity of Selected Lactic Acid Bacteria for Bioconversion of Milk and Whey from Goat Milk to Release Biomolecules with Antibacterial Activity.

The aim of the study was to assess the antibacterial features of functional macromolecules released during the fermentation of goat milk and whey from goat milk by selected lactic acid bacteria strains that are components of kefir grain microflora. Two milk sources were used: goat milk and whey from goat milk. The lactic acid bacteria (LAB) and indicator microorganisms used were Lactobacillus plantarum PCM 1386, Lactobacillus fermentum PCM 491, Lactobacillus rhamnosus PCM 2677, Lactobacillus acidophilus PCM 2499, Escherichia coli PCM 2793, Salmonella enteritidis PCM 2548, Micrococcus luteus PCM 525, and Proteus mirabilis PCM 1361. The metabolic activity of LAB was described by the Gompertz model, and the parameters proposed for this experiment were the maximum rate of change of electrical impedance and potential biodegradability. Antibacterial activity was examined using the culture method in a liquid medium, determination of the reduction in indicator microorganisms, and optical density changes. Results show that the selective LAB produced certain active biomolecules with antibacterial activity from whey, a by-product that is sometimes troublesome for goat milk processors to manage. Lactobacillus acidophilus is a microorganism that is characterized by the highest metabolic activity in goat milk and whey from goat milk. It has the possibility to produce macromolecules with antibacterial activity.

Determining the safety of kefir grains for public health

In this study, kefir grains and kefir produced from contaminated grains were investigated in terms of food safety. For this aim, traditional kefir grains were collected from distinct parts of Turkey, and their pathogenicity was examined. Typical and non-typical colonies were isolated on Violet Red Bile Agar and identified for the first time at species level. Antibiotic resistance and hemolytic activity of the isolates were also determined. Coliform and pathogenic bacteria was found in 19 out of 30 kefir grains tested (63.33%). Although Hafnia paralvei was the predominant group, Klebsiella oxytoca, Citrobacter freundii, Serratia liquefaciens, and Escherichia coli were also identified among the 27 strains as the pathogenic bacteria. It was found that the bacterial count of kefir produced from two kefir grains containing pathogenic bacteria was 8.44 log CFU/mL and 8.20 log CFU/mL at the end of the 10th day. All isolates were sensitive to ciprofloxacin, nalidixic acid, meropenem, and ertapenem but resistant to ampicillin and vancomycin. Furthermore, all strains were found to be β-hemolytic in that study. As a result, it was determined that traditionally produced kefir can be risky in terms of food safety due to contaminated kefir grains and this risk continues throughout consumption.

Non-Conventional Sucrose-Based Substrates: Development of Non-Dairy Kefir Beverages with Probiotic Potential

There is a scarcity of studies evaluating the influence of different commonly marketed sugars in water kefir beverage production. Therefore, this study aimed to evaluate the fermentation of water kefir grains in different sugary solutions: brown, demerara, refined, coconut, and cane molasses. A total of 10% of each type of sugar was dissolved in sterile water to which 10% of kefir grains were then added and fermented for 48 h at room temperature. Analyses of pH/acidity, soluble solids, lactic/acetic acids, and lactic acid bacteria and yeast counts were performed, in addition to grain weighing at 0 h, 24 h, and 48 h. The microbial biodiversity was measured using PCR-DGGE and DNA sequencing at the species level. A sensory acceptance test was performed on all beverages. Lactobacillus, Lacticaseibacillus, Lentilactobacillus Lactococcus, Leuconostoc, Acetobacter, Saccharomyces, Kluyveromyces, Lachancea, and Kazachstania were present in the kefir grains and the beverages. Molasses showed a more intense fermentation, with greater production of organic acids and higher lactic/acetic acid bacteria and yeast counts (7.46 and 7.49 log CFU/mL, respectively). Refined sugar fermentation had a lower microbial yield of lactic/acetic acid bacteria (6.87 log CFU/mL). Smith’s salience index indicates that the brown-sugar kefir beverage was better accepted among the tasters. The results indicate that the use of alternative sources of sugar to produce water kefir beverages is satisfactory. This opens up new perspectives for the application of kefir microorganisms in the development of beverages with probiotic and functional properties.

Therapeutic and Dietary Support for Gastrointestinal Tract Using Kefir as a Nutraceutical Beverage: Dairy-Milk-Based or Plant-Sourced Kefir Probiotic Products for Vegan and Lactose-Intolerant Populations

Kefir is a fermented milk beverage different in consistency and taste from other popular milk-product yogurt. Unlike yogurt prepared using lactic acid bacteria in fermentation, milk is fermented for kefir production using preculture in the form of kefir grains. Therefore, the metabolic activities of a mixed culture, including strains of bacteria and yeast, contribute to the probiotic characteristics in kefir. This article is based on the review of published studies on the functionality and nutraceutical properties of kefir. The therapeutic and dietary properties of kefir beverage and its probiotic strains have been discussed for their several health benefits. Concise selected information mostly from recent reports has been presented for two categories of kefir products: milk used for the production of dairy-based traditional kefir beverages for the lactose-tolerant population, and the plant-sourced substrates used for the production of dairy-free kefir beverages for lactose-intolerant and vegan consumers.

Comparative Genomics Analysis of Habitat Adaptation by Lactobacillus kefiranofaciens.

Lactobacillus kefiranofaciens is often found in fermented dairy products. Many strains of this species have probiotic properties, contributing to the regulation of immune metabolism and intestinal flora. This species was added to the list of lactic acid bacteria that can be added to food in China, in 2020. However, research on the genomics of this species is scarce. In this study we undertook whole genome sequencing analysis of 82 strains of L. kefiranofaciens from different habitats, of which 9 strains were downloaded from the NCBI RefSeq (National Center for Biotechnology Information RefSeq). The mean genome size of the 82 strains was 2.05 ± 0.25 Mbp, and the mean DNA G + C content was 37.47 ± 0.42%. The phylogenetic evolutionary tree for the core genes showed that all strains belonged to five clades with clear aggregation in relation to the isolation habitat; this indicated that the genetic evolution of L. kefiranofaciens was correlated to the isolation habitat. Analysis of the annotation results identified differences in the functional genes, carbohydrate active enzymes (CAZy) and bacteriocins amongst different isolated strains, which were related to the environment. Isolates from kefir grains had more enzymes for cellulose metabolism and a better ability to use vegetative substrates for fermentation, which could be used in feed production. Isolates from kefir grains also had fewer kinds of bacteriocin than isolates from sour milk and koumiss; helveticin J and lanthipeptide class I were not found in the isolates from kefir grains. The genomic characteristics and evolutionary process of L. kefiranofaciens were analyzed by comparative genomics and this paper explored the differences in the functional genes amongst the strains, aiming to provide a theoretical basis for the research and development of L. kefiranofaciens.

Microbial Community Variations and Bioconversion Improvements during Soybean-Based Fermentation by Kefir Grains.

Soybeans possess unexpected flavors and are difficult to be absorbed by the gastrointestinal tract. Kefir grain fermentation provides diverse strains and bioactive compounds, which may enhance flavor and bioaccessibility. Third-generation sequencing was applied to analyze the microbial diversity in milk and soybean kefir grains in this study. In both types of kefir grains, the most common bacterial genus was Lactobacillus, and their fungal communities were dominated by Kazachstania. Lactobacillus kefiranofaciens was the most abundant species in kefir grains, while Lactobacillus kefiri showed a higher proportion in soybean kefir grains. In addition, the quantification of free amino acids and volatile flavor compounds in soybean solution and soybean kefir have shown the increased content of glutamic acid and a decreased amount of unpleasant beany flavor compounds, demonstrating that the nutritive value and sensory properties of soybean can be improved by kefir grain fermentation. Finally, the bioconversion of isoflavones during fermentation and in vitro digestion was evaluated, suggesting that fermentation is beneficial for aglycone formation and absorption. To conclude, kefir fermentation is proposed to change the microbial structure of kefir grains, promote the nutritional value of soybean-based fermented products, and provide possible solutions for the development of soybean products.

Chemical Evaluation and Probiotic Potential of Kefir Different Nutrient Media

Kefir is a gelatinous mass composed of bacteria and yeast. This study aims to develop beverages obtained from kefir grains’ fermentation in different nutrient media. Thus, kefir fermentation was performed in an aqueous solution of sucrose, whole milk, whole grape juice, and water-soluble coconut extract. The fermentation process was analyzed from grain growth, beverage yield, lactic acid determination, pH, total soluble solids, and microbiological analysis. The results showed the beverages had pH and lactic acid values following the legislation. Furthermore, it identified the probiotic potential of the coconut and milk water-soluble extract beverages.

STUDY OF THE KINETICS OF MILK KEFIR USING SOY GERM AS SUBSTRATE

The main objective of this study was to analyze the growth kinetics of milk kefir on bean sprouts (Glycine max) as a germinated substrate for 4 days by the glass jar method followed by extracts. Ratio 1:3 (soy: water). 3% kefir grains (activated) inoculated with soluble bud extracts. The soluble extract of bean sprouts has a total sugar content of 5.57% and a fermentable carbohydrate of 3.37 g / L (sucrose), which is a source of nutrition and energy reserves; 1.40% of lipids are used for catabolic grain activity, while protein increases the amount of soluble nitrogen by 6.66%. The pH is 6.67 and the acidity is 0.17%, inversely proportional to lactic acid. The number of microbial populations of soluble extracts of kefirada sprouts reached the logarithmic stage of development after 24 hours for lactic acid bacteria and 48 hours for acetic acid bacteria and yeast, consuming the nutrients of the beverage, influencing its metabolites on the pH of the medium; The period of decomposition of lactic acid bacteria, acetic acid and yeast is 72 hours, and the medium lacks nutrients. The symbiotic action of milk kefir using soluble sprouted extracts is mutual, as the microorganisms it contains grow synergistically and create favorable changes in pH and acidity, depletion of nutrients and the creation of an appropriate environment. To improve the texture it is recommended to combine with fruits or vegetables that contain a lot of sugar.

Behavior of the conversion of glucose, galactose and lactose to lactic acid by kefir grains

Few studies have been reported on lactic acid production by kefir grains. Kefir has been widely associated with probiotic use due to its cell growth in food matrices such as milks, juices and sugary solutions. However, from industrial scale there are no reports of its use in lactic acid production. In this work, we carried out experiments to test and understand how glucose, galactose and lactose, during lactic-acid fermentation, were converted in lactic acid by kefir grains. Given the microbial complexity in coexistence in kefir grains, it is likely that kinetic studies are not the most appropriate for the positive or negative definition of the kefir use as a starter in the lactic acid fermentative production on an industrial scale. It was concluded that, although with a higher Lag phase, lactose was the substrate that best presented a product and cell conversion rate, although glucose and galactose can also be used as a substrate in the production of this carboxylic acid.

Mathematical Modeling of Microwave-Assisted Foam-Mat Drying of Kefir

Kefir is a traditional drink produced by the fermentation of milk with kefir grain. In this study, foam-mat drying of kefir using a microwave oven was made, and drying kinetics was determined at various microwave power levels (100, 180, and 300 W). Values of D eff were calculated between 4.8394 × 10 − 10 and 1.8603 × 10 − 9 m2 s-1. Besides, E a was calculated as 5.28 W g-1. Furthermore, increased drying rates were obtained with increasing microwave powers. In addition, seven drying models were fitted to the moisture ratios obtained from experiments, and Midilli and others’ model was found to be the best-fitted model with the highest values (0.9983, 0.9983, and 0.9985 for 100, 180, and 300 W, respectively) of R 2 and the lowest values of χ 2 , RSS, and RMSE.

Lebanese fermented goat milk products: From tradition to meta-omics

Ambriss, Serdaleh and Labneh El Darff are traditional Lebanese products made from fermented goat’s milk. A questionnaire completed by 50 producers of these products showed that they are prepared by periodic percolation either by milk or by Laban in amphora or goat skins during the lactation season. Production is carried out on a small scale and in a limited number of production units, often by elderly people, resulting in a real risk of disappearance of these products and loss of the corresponding microbial resources. In this study, 34 samples from 18 producers were characterized by culture-dependent and -independent analyses. The results obtained from these two methods were radically different, the latter revealing in Ambriss and Serdaleh the co-dominance of Lactobacillus kefiranofaciens, a fastidious-growing species, and Lactococcus lactis in a viable but not culturable state. Overall, their composition is reminiscent of kefir grains. Phylogenomic and functional analyses of the genomes of the key species Lb. kefiranofaciens have revealed differences from those found in kefir, particularly in their polysaccharide genes, which may explain the absence of grains. However, Labneh El Darff displayed a dominance of Lactobacillus delbrueckii, probably due to the addition of Laban. In addition, the study identified several zoonotic pathogens, including Streptococcus parasuis, which dominated in one sample. Metagenome-Assembled Genome (MAG) analysis indicated that this pathogen acquired lactose utilization genes through horizontal gene transfer. The contamination of the herd with Mycoplasmopsis agalactiae in the Chouf region was also revealed by MAG analysis of the Serdaleh samples. Antibiotic resistance genes were detected in most of the samples, particularly in the Serdaleh ones, where the dominant L. lactis strains possessed a plasmid with a multi-resistance island. Finally, this study paves the way for further analyses to shed light on the resilience of these ecosystems established in amphora or in goatskins and to improve hygiene practices for milk production.