The Many Faces of Kefir Fermented Dairy Products: Quality Characteristics, Flavour Chemistry, Nutritional Value, Health Benefits, and Safety

Kefir milk alleviates benzene-induced immunotoxicity and hematotoxicity in rats

The adverse health effects of benzene occupational and circumstance pollution exposure are an increasing concern. It leads to damage to various human tissues including bone marrow and ovarian tissues and many vital physiological processes. Previous studies showed that kefir is a rich probiotic, having protective effect, thanks to its antioxidant, anti-inflammatory, and immunomodulatory capacity. The purpose of this study was to evaluate the potential efficacy of kefir to remediate benzene toxicity in rat. Thirty-two female rats were randomly allocated and administered orally with benzene and/or kefir during a period of 21 consecutive days. At the end of the experiment, hematological and bone marrow cell changes were estimated. The animals exposed to benzene exhibited anemia and a significant decrease in the levels of white blood cell. Moreover, benzene led to the activation of gene expression of the pro-inflammatory cytokines interleukin-1β (IL-1β) and interleukin-6 (IL-6), a myelotoxicity in bone marrow cells. Our data showed that kefir treatment alleviated benzene-associated weight loss and increased the number of whole blood cells in peripheral blood and nucleated cells in the bone marrow. Furthermore, these physiological results were observed with animals showing high concentrations of lactic acid bacteria (LAB) determined from fecal samples, which are considered an indicator of kefir-associated microorganisms. Our study suggests that kefir is a potential nutritional supplement target to attenuate hematotoxicity induced by benzene.

Microencapsulation of Bioactive Ingredients for Their Delivery into Fermented Milk Products: A Review

The popularity and consumption of fermented milk products are growing. On the other hand, consumers are interested in health-promoting and functional foods. Fermented milk products are an excellent matrix for the incorporation of bioactive ingredients, making them functional foods. To overcome the instability or low solubility of many bioactive ingredients under various environmental conditions, the encapsulation approach was developed. This review analyzes the fortification of three fermented milk products, i.e., yogurt, cheese, and kefir with bioactive ingredients. The encapsulation methods and techniques alongside the encapsulant materials for carotenoids, phenolic compounds, omega-3, probiotics, and other micronutrients are discussed. The effect of encapsulation on the properties of bioactive ingredients themselves and on textural and sensory properties of fermented milk products is also presented.

Effect of kefir beverage consumption on glycemic control: A systematic review and meta-analysis of randomized controlled clinical trials

Kefir is a fermented beverage obtained as a result of lactic-alcoholic fermentation of milk by using kefir grains or a starter culture. Kefir beverage has numerous health benefits owing to its antimicrobial, anti-inflammatory and anti-diabetic properties, while it could also regulate the gut microbiota. This beverage is recommended as a nutritional approach to glycemic control. This systematic review and meta-analysis of randomized controlled trials (RCTs) aimed to evaluate the effects of kefir beverage on the glycemic control. For this purpose, a literature search was conducted via databases such as PubMed, Scopus, ISI Web of Science, and Google Scholar for the articles published until July 2020 with no limitation. The indicators of glycemic control were fasting blood sugar (FBS), hemoglobin A1c (HbA1c), and insulin. In total, six RCTs on a total sample size of 323 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 HbA1c, FBG and insulin compared to baseline. Considering the clinical heterogeneity caused by the varied duration and dosage of kefir beverage treatment, a random effects model was used to estimate the pooled WMD. Findings indicated a more significant reduction in the FBS (WMD = -10.28; 95% CI: -16.53-4.02; P = 0.001) and insulin (WMD = -2.87; 95% CI: -3.96-1.78; P < 0.00001) in the kefir treatment group. Furthermore, kefir consumption could reduce HbA1c (HbA1c = -0.64 -1.36, 0.08), while this effect was not considered significant (-0.64; 95% CI: -1.36-0.08; P = 0.08). The results of our meta-analysis indicated that kefir beverage could reduce the FBS and insulin levels without a significant effect on HbA1c. In general, our findings showed that kefir beverages may have beneficial effects on glycemic control. However, more clinical data and research into the mechanism of probiotics are required to clarify the beneficial effects of probiotics on glycemic markers.

Kefir as a Functional Beverage Gaining Momentum towards Its Health Promoting Attributes

The consumption of fermented foods posing health-promoting attributes is a rising global trend. In this manner, fermented dairy products represent a significant subcategory of functional foods with established positive health benefits. Likewise, kefir—a fermented milk product manufactured from kefir grains—has been reported by many studies to be a probiotic drink with great potential in health promotion. Existing research data link regular kefir consumption with a wide range of health-promoting attributes, and more recent findings support the link between kefir’s probiotic strains and its bio-functional metabolites in the enhancement of the immune system, providing significant antiviral effects. Although it has been consumed for thousands of years, kefir has recently gained popularity in relation to novel biotechnological applications, with different fermentation substrates being tested as non-dairy functional beverages. The present review focuses on the microbiological composition of kefir and highlights novel applications associated with its fermentation capacity. Future prospects relating to kefir’s capacity for disease prevention are also addressed and discussed.

Core-shell PLA/Kef hybrid scaffolds for skin tissue engineering applications prepared by direct kefiran coating on PLA electrospun fibers optimized via air-plasma treatment

Over the recent years, there is a growing interest in electrospun hybrid scaffolds composed of synthetic and natural polymers that can support cell attachment and proliferation. In this work, the physical and biological properties of polylactic acid (PLA) electrospun mats coated with kefiran (Kef) were evaluated. Gravimetric, spectroscopic (FTIR-ATR) and morphological investigations via scanning electron microscopy confirmed the effective formation of a thin kefiran layer wrapped on the PLA fibers with an easy-tunable thickness. Air plasma pre-treatment carried out on PLA (P-PLA) affected both the morphology and the crystallinity of Kef coating as confirmed by differential scanning calorimetry and X-ray diffraction analyses. Scaffolds were mechanically characterized with tensile tests to evaluate the reinforcing action of the Kef coating. The water resistance of Kefiran coating in distilled water at 37 °C evaluated on both PLA/Kef and P-PLA/Kef was carried out by gravimetric and morphological analyses. Finally, cell culture assays with embryonic fibroblast cells were conducted on selected hybrid scaffolds to compare the cell proliferation, morphology, and collagen production with PLA and P-PLA electrospun scaffolds. Based on the results, we can demonstrate that direct coating of PLA from Kef/water solutions is an effective approach to prepare hybrid scaffolds with tunable properties and that the plasma pre-treatment enhances the affinity between PLA and Kefiran. In vitro tests demonstrated the great potential of PLA/Kef hybrid scaffolds for skin tissue engineering.

Kefir peptides exhibit antidepressant-like activity in mice through the BDNF/TrkB pathway

Depression is a prevalent, stress-related mental disorder that can lead to serious psychiatric diseases with morbidity and high mortality. Although some functional fermented dairy drinks have promising anxiolytic and antidepressant effects, the mechanism is still not clear. To determine the antidepressant-like effect and the potential molecule mechanism of kefir peptides (KP), various behavioral tests, including the elevated plus maze test, open field test, forced swimming test, and tail suspension test, were used. Administration of 150 mg/kg KP in mice reduced the duration of immobility in the forced swimming test and tail suspension test, elevated the time spent in the open arm and center zone in the elevated plus maze test, and increased the total distance traveled, average speed, and time spent in the center zone in the open field test compared with the mock group. These results indicated that KP dramatically ameliorated the depression-like behaviors. Kefir peptides were further isolated and identified using high-performance liquid chromatography and liquid chromatography-tandem mass spectrometry, from which 3 peptides were identified and designated KFP-1, KFP-3, and KFP-5. Among these peptides, administration of KFP-3 (15 AA residues) remarkably decreased immobility time in the forced swimming test and increased mobility time in the tail suspension test. Therefore, KFP-3 may be the major active peptide with antidepressant activity in KP. Overexpression of brain-derived neurotrophic factor, phosphorylated tropomyosin receptor kinase B, and phosphorylated ERK1/2 protein levels could be detected in the hippocampus under KP administration. Therefore, we suggest that KP improves depressive-like behaviors by activating the brain-derived neurotrophic factor-phosphorylated tropomyosin receptor kinase B signaling pathway. Kefir peptides may serve as a new type of antidepressant dairy product and may provide potent antidepressant effects for clinical use.

Kefir and Its Biological Activities

Kefir is a fermented beverage with renowned probiotics that coexist in symbiotic association with other microorganisms in kefir grains. This beverage consumption is associated with a wide array of nutraceutical benefits, including anti-inflammatory, anti-oxidative, anti-cancer, anti-microbial, anti-diabetic, anti-hypertensive, and anti-hypercholesterolemic effects. Moreover, kefir can be adapted into different substrates which allow the production of new functional beverages to provide product diversification. Being safe and inexpensive, there is an immense global interest in kefir’s nutritional potential. Due to their promising benefits, kefir and kefir-like products have a great prospect for commercialization. This manuscript reviews the therapeutic aspects of kefir to date, and potential applications of kefir products in the health and food industries, along with the limitations. The literature reviewed here demonstrates that there is a growing demand for kefir as a functional food owing to a number of health-promoting properties.

Importance of Bioactive Substances in Sheep's Milk in Human Health

Sheep's milk is an important source of bioactive substances that have health-promoting functions for the body. The valuable composition of sheep's milk is due to the high content of fatty acids, immunoglobulins, proteins, hormones, vitamins and minerals. Many biopeptides found in milk have antibacterial, antiviral and anti-inflammatory properties. The bioactive substances of sheep's milk also show anticancer properties. Sheep's milk, thanks to its content of CLA and orotic acid, prevents the occurrence of type 2 diabetes, Alzheimer's disease and cancer. Sheep's milk, as a product rich in bioactive substances, can be used as a medical aid to support the body in the fight against neurological and cancer diseases.

Probiotic Lactobacilli Isolated from Kefir Promote Down-Regulation of Inflammatory Lamina Propria T Cells from Patients with Active IBD

Ulcerative colitis and Crohn’s disease, the two main forms of inflammatory bowel disease (IBD), are immunologically mediated disorders. Several therapies are focused on activated T cells as key targets. Although Lactobacillus kefiri has shown anti-inflammatory effects in animal models, few studies were done using human mucosal T cells. The aim of this work was to investigate the immunomodulatory effects of this bacterium on intestinal T cells from patients with active IBD. Mucosal biopsies and surgical samples from IBD adult patients (n = 19) or healthy donors (HC; n = 5) were used. Lamina propria mononuclear cells were isolated by enzymatic tissue digestion, and entero-adhesive Escherichia coli-specific lamina propria T cells (LPTC) were expanded. The immunomodulatory properties of L. kefiri CIDCA 8348 strain were evaluated on biopsies and on anti-CD3/CD28-activated LPTC. Secreted cytokines were quantified by ELISA, and cell proliferation and viability were assessed by flow cytometry. We found that L. kefiri reduced spontaneous release of IL-6 and IL-8 from inflamed biopsies ex vivo. Activated LPTC from IBD patients showed low proliferative rates and reduced secretion of TNF-α, IL-6, IFN-γ and IL-13 in the presence of L. kefiri. In addition, L. kefiri induced an increased frequency of CD4⁺FOXP3⁺ LPTC along with high levels of IL-10. This is the first report showing an immunomodulatory effect of L. kefiri CIDCA 8348 on human intestinal cells from IBD patients. Understanding the mechanisms of interaction between probiotics and immune mucosal cells may open new avenues for treatment and prevention of IBD.

Kefir and Intestinal Microbiota Modulation: Implications in Human Health

In the last decades changes in the pattern of health and disease in Latin America and in the world has been observed, with an increase in cases of chronic non-communicable diseases. Changes in intestinal microbiota composition can contribute to the development of these diseases and be useful in their management. In this context, the consumption of fermented foods with probiotic properties, such as kefir, stands out due to its gut microbiota-modulating capacity. There is an increasing interest in the commercial use of kefir since it can be marketed as a natural beverage containing health-promoting bacteria and has been gaining international popularity in Latin America. Also the consumption of these drinks in Latin America seems to be even more relevant, given the socioeconomic situation of this population, which highlights the need for disease prevention at the expense of its treatment. In this narrative review, we discuss how kefir may work against obesity, diabetes mellitus, liver disease, cardiovascular disorders, immunity, and neurological disorders. Peptides, bioactive compounds and strains occurring in kefir, can modulate gut microbiota composition, low-grade inflammation and intestinal permeability, which consequently may generate health benefits. Kefir can also impact on the regulation of organism homeostasis, with a direct effect on the gut-brain axis, being a possible strategy for the prevention of metabolic diseases. Further studies are needed to standardize these bioactive compounds and better elucidate the mechanisms linking kefir and intestinal microbiota modulation. However, due to the benefits reported, low cost and ease of preparation, kefir seems to be a promising approach to prevent and manage microbiota-related diseases in Latin America and the rest of the world.

Can sucrose-substitutes increase the antagonistic activity against foodborne pathogens, and improve the technological and functional properties of sheep milk kefir?

The effect of different types of sugar (sucrose, demerara, brown, fructose, coconut sugar, and honey) on sheep milk kefir was evaluated. Microbial counts (Lactobacillus, Lactococcus, Leuconostoc, yeast), antagonistic activity against foodborne pathogens, microstructure (scanning electron microscopy), and antiproliferative activity of cancer cells were evaluated. Furthermore, the antioxidant activity (DPPH), inhibitory activity of angiotensin-converting enzyme (ACE), α-amylase, and α-glucosidase, lactose content, lactic and acetic acids and ethanol, fatty acid profile and volatile organic compounds were determined. The addition of sugars increased the Lactobacillus population (up to 2.24 log CFU/mL), metabolites concentration, antagonistic activity against pathogens, antioxidant activity (11.1 to 24.1%), ACE inhibitory activity (27.5 to 37.6%), α-amylase inhibition (18 to 37.4%), and anti-proliferative activity. Furthermore, it improved the fatty acid profile and volatile compounds. The results suggest that the replacement of sucrose with different types of sugar constitute an interesting option to be used in sheep milk kefir formulations.

The Effect of Fermentation with Kefir Grains on the Physicochemical and Antioxidant Properties of Beverages from Blue Lupin (Lupinus angustifolius L.) Seeds

Plant derived fermented beverages have recently gained consumers' interest, particularly due to their intrinsic functional properties and presence of beneficial microorganisms. Three variants containing 5%, 10%, and 15% (w/w) of sweet blue lupin (Lupinus angustifolius L. cv. "Boregine") seeds were inoculated with kefir grains and incubated at 25 °C for 24 h. After processing, beverages were stored in refrigerated conditions (6 °C) for 21 days. Changes in microbial population, pH, bioactive compounds (polyphenolics, flavonoids, ascorbic acid), reducing sugars, and free amino acids were estimated. Additionally, viscosity, firmness, color, and free radicals scavenging properties were determined. Results showed that lactic acid bacteria as well as yeast were capable of growing well in the lupin matrix without any supplementation. During the process of refrigeration, the viability of the microorganisms was over the recommended minimum level for kefir products. Hydrolysis of polysaccharides as well as increase of free amino acids was observed. As a result of fermentation, the beverages showed excellent DPPH, ABTS+·, ·OH, and O2- radicals scavenging activities with a potential when considering diseases associated with oxidative stress. This beverages could be used as a new, non-dairy vehicle for beneficial microflora consumption, especially by vegans and lactose-intolerant consumers.

Improving Kefir Bioactive Properties by Functional Enrichment with Plant and Agro-Food Waste Extracts

An increase in the number of novel fortified kefir-based beverages was observed in the last decades. Vegetables were often proposed as convenient resources of bioactive molecules able to improve nutraceutical benefits of these drinks and/or to confer them new significant features. These findings have been well accepted by the consumers, which generally reserve an important role to the quality of the assumed food and beverages. Specifically, functional fermented milk-based drinks enriched with vegetable extracts display significant biological properties, due to the presence of bioactive compounds exhibiting antimicrobial and antioxidant features. In addition, agro-industrial wastes have been also proposed as innovative resources of secondary metabolites to enrich kefir-based products. Eco-friendly extraction techniques were generally exploited to achieve the isolation of biomolecules and reducing, at the same time, economic and environmental loads. To this regard, this review deeply investigates the main findings to improve kefir bioactive properties by functional enrichment with plant and agro-food waste extracts. The nutraceutical characteristics related to the consumers’ health benefits, as well as their effects on the sensorial, chemical, and microbiological properties of the products were evaluated.

Antimicrobial Activity of Six International Artisanal Kefirs Against Bacillus cereus, Listeria monocytogenes, Salmonella enterica serovar Enteritidis, and Staphylococcus aureus

Kefir, a fermented dairy beverage, exhibits antimicrobial activity due to many metabolic products, including bacteriocins, generated by lactic acid bacteria. In this study, the antimicrobial activities of artisanal kefir products from Fusion Tea (A), Britain (B), Ireland (I), Lithuania (L), the Caucuses region (C), and South Korea (K) were investigated against select foodborne pathogens. Listeria monocytogenes CWD 1198, Salmonella enterica serovar Enteritidis ATCC 13076, Staphylococcus aureus ATCC 25923, and Bacillus cereus ATCC 14579 were inhibited by artisanal kefirs made with kefir grains from diverse origins. Kefirs A, B, and I inhibited all bacterial indicator strains examined at varying levels, except Escherichia coli ATCC 12435 (non-pathogenic, negative control). Kefirs K, L, and C inhibited all indicator strains, except S. aureus ATCC 25923 and E. coli ATCC 12435. Bacteriocins present in artisanal kefirs were determined to be the main antimicrobials in all kefirs examined. Kefir-based antimicrobials are being proposed as promising natural biopreservatives as per the results of the study.

Yeasts and Bacterial Consortia from Kefir Grains Are Effective Biocontrol Agents of Postharvest Diseases of Fruits

Fungal pathogens in fruits and vegetables cause significant losses during handling, transportation, and storage. Biological control with microbial antagonists replacing the use of chemical fungicides is a major approach in postharvest disease control, and several products based on single antagonists have been developed but have limitations related to reduced and inconsistent performance under commercial conditions. One possible approach to enhance the biocontrol efficacy is to broaden the spectrum of the antagonistic action by employing compatible microbial consortia. Here, we explore commercial kefir grains, a natural probiotic microbial consortium, by culture-dependent and metagenomic approaches and observed a rich diversity of co-existing yeasts and bacterial population. We report effective inhibition of the postharvest pathogen Penicillium expansum on apple by using the grains in its fresh commercial and milk-activated forms. We observed few candidate bacteria and yeasts from the kefir grains that grew together over successive enrichment cycles, and these mixed fermentation cultures showed enhanced biocontrol activities as compared to the fresh commercial or milk-activated grains. We also report several individual species of bacteria and yeasts with biocontrol activities against Penicillium rots on apple and grapefruit. These species with antagonistic properties could be further exploited to develop a synthetic consortium to achieve enhanced antagonistic effects against a wide range of postharvest pathogens.