Comparative study of microbiological, chemical and sensory properties of kefirs produced in Estonia, Latvia and Lithuania

In the current study the microbiological, sensory and chemical properties of 24 kefirs (12 producers) from Estonian, Latvian and Lithuanian retail market were determined using gas chromatography (GC), high performance liquid chromatography (HPLC-MS/MS-Q-TOF and LC-ion trap MS/MS), spectrophotometry and other methods. Antihypertensive, angiotensin-converting enzyme (ACE) inhibiting, antioxidant and antibacterial peptides were found in the kefir samples. According to the results of principal component analysis of 200 most abundant compounds obtained with HPLC-MS/MS-Q-TOF analysis, Estonian kefirs differed from the rest. Kefirs of Latvian and Lithuanian origin showed similarities in several characteristics, probably related to the starter cultures and technological processes. The fatty acids composition of all Baltic kefirs was uniform. The antioxidant capacity of the kefirs varied slightly, whereas intermediate positive correlation (r= 0·32,P< 0·05) was found between antioxidativity and total bacterial count. The lipid oxidation level, estimated as the content of linoleic and oleic acid primary oxidation products, oxylipins, was very low in all studied kefirs. Only one third of analysed kefirs met the requirements of the minimum sum of viable microorganisms, indicated in the Codex Standard for Fermented Milks.

Milk kefir: composition, microbial cultures, biological activities, and related products

In recent years, there has been a strong focus on beneficial foods with probiotic microorganisms and functional organic substances. In this context, there is an increasing interest in the commercial use of kefir, since it can be marketed as a natural beverage that has health promoting bacteria. There are numerous commercially available kefir based-products. Kefir may act as a matrix in the effective delivery of probiotic microorganisms in different types of products. Also, the presence of kefir's exopolysaccharides, known as kefiran, which has biological activity, certainly adds value to products. Kefiran can also be used separately in other food products and as a coating film for various food and pharmaceutical products. This article aims to update the information about kefir and its microbiological composition, biological activity of the kefir's microflora and the importance of kefiran as a beneficial health substance.

Saccharomyces unisporus: Biotechnological Potential and Present Status

 The yeast species of the Saccharomyces genus have a long history of traditional applications and beneficial effects. Among these presence of the Saccharomyces unisporus has been documented in various dairy products and has become a subject of interest and great importance. S. unisporus has shown a significant role in the ripening of cheese and production of fermented milk products such as kefir and koumiss. The absence of pseudohyphae during the life cycle of S. unisporus is an indication of nonpathogenicity. Significance has been laid on the presence of S. unisporus in food-grade products and a close proximity of S. unisporus to S. florentinus and both of these species are accepted by the International Dairy Federation and the European Food and Feed Cultures Association for food and feed applications. Since over the years, S. unisporus has already become a part of various dairy products, S. unisporus can be considered as a potential candidate for generally regarded as safe status. S. unisporus has the capacity to convert ketoisophorone to levodione, which is an important pharmaceutical precursor. S. unisporus are considered as the potential producers of farnesol which eventually controls filamentation of pathogenic microorganisms. Apart from that, S. unisporus produces certain omega unsaturated fatty acids which combat diseases. Henceforth, the areas which S. unisporus can be possibly exploited for its useful intermediates are the enzymes and fatty acids it produces. In this context, this review attempts to describe and discuss the ubiquity of S. unisporus in food products, cellular composition, regulatory pathways, and its synthesis of fatty acids and enzymes.

Characterization and stability of lactobacilli and yeast microbiota in kefir grains

Characterization and stability of lactobacilli and yeasts from kefir grains using culture-dependent and culture-independent methods were investigated in this study. Culture-dependent analysis, followed by sequencing of 16S ribosomal DNA for bacteria and 26S rRNA gene for yeasts, revealed 3 different species of lactobacilli and yeasts, respectively. The most frequently isolated bacterial species were Lactobacillus kefiranofaciens ssp. kefirgranum, Lb. parakefiri, and Lb. kefiri, whereas yeasts belonged to Kluyveromyces marxianus, Kazachstania exigua, and Rhodosporidium kratochvilovae. This study is the first to report on the presence of R. kratochvilovae in kefir grains. On the other hand, PCR-denaturing gradient gel electrophoresis in the culture-independent method showed that the dominant microorganisms were Lb. kefiranofaciens ssp. kefirgranum, Kl. marxianus and Ka. exigua, but did not reveal bands corresponding to Lb. parakefiri, Lb. kefiri, or R. kratochvilovae. Our results support the necessity of combining more techniques for detailed and reliable study of microbial communities in kefir grains. Another interesting finding confirmed that the detected dominant microbiota of kefir grains is very stable and did not change over experimental time. This finding is important to ensure consistent product quality.

Protective effects of the fermented milk Kefir on X-ray irradiation-induced intestinal damage in B6C3F1 mice

Gastrointestinal damage associated with radiation therapy is currently an inevitable outcome. The protective effect of Kefir was assessed for its usefulness against radiation-induced gastrointestinal damage. A Kefir supernatant was diluted by 2- or 10-fold and administered for 1 week prior to 8 Gray (Gy) X-ray irradiation at a dose rate of 2 Gy/min, with an additional 15 d of administration post-irradiation. The survival rate of control mice with normal drinking water dropped to 70% on days 4 through 9 post-irradiation. On the other hand, 100% of mice in the 10- and 2-fold-diluted Kefir groups survived up to day 9 post-irradiation (p<0.05 and p<0.01, respectively). Examinations for crypt regeneration against 8, 10 and 12 Gy irradiation at a dose rate of 4 Gy/min revealed that the crypt number was significantly increased in the mice administered both diluted Kefir solutions (p<0.01 for each). Histological and immunohistochemical examinations revealed that the diluted Kefir solutions protected the crypts from radiation, and promoted crypt regeneration. In addition, lyophilized Kefir powder was found to significantly recover the testis weights (p<0.05), but had no effects on the body and spleen weights, after 8 Gy irradiation. These findings suggest that Kefir could be a promising candidate as a radiation-protective agent.

In vitro assay of the antimicrobial activity of kephir against bacterial and fungal strains

Kephir is a fermented carbonated refreshing milk, with a slightly acidic aromatic taste and creamy foam composition which contains lactobacilli, leuconostocci, acetic acid bacteria, lactostreptococci and yeasts. Recent studies have demonstrated its antibacterial, immunostimulating, antitumoral and cholesterol-lowering activities.

PURPOSE

The purpose of this study was to investigate the antimicrobial activity of kephir against Bacillus subtilis spp. spizizenii ATCC 6633, Staphylococcus aureus ATCC 6538, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 8739, Salmonella enteritidis ATCC 13076, Pseudomonas aeruginosa ATCC 9027 and Candida albicans ATCC 10231. The kephir fermented for 24 h and 48 h, as well and after 7 days preservation at 4-8 °C was tested by in vitro disk diffusion method. The intensity of the antimicrobial activity was interpreted by comparison with two antibiotics, i.e. ampicillin and neomycin.

RESULTS

The antimicrobial activity of 24 h as well as 48 fermented kephir, fresh or after 7 days preservation at 4-8 °C was similar and observed against B. subtilis, S. aureus, E. coli, E. faecalis and S. enteritidis. For E. coli, E. faecalis and S. enteritidis the antimicrobial activity was superior to both tested antibiotics and for B. subtilis and S. aureus to one antibiotic. The tested products exhibited no activity against P. aeruginosa and C. albicans.

CONCLUSION

Kephir is exhibiting large spectrum and strong antibacterial activity probably due to the complex viable probiotic strains association producing antimicrobial substances.

High-throughput sequence-based analysis of the bacterial composition of kefir and an associated kefir grain

Lacticin 3147 is a two-peptide broad spectrum lantibiotic produced by Lactococcus lactis DPC3147 shown to inhibit a number of clinically relevant Gram-positive pathogens. Initially isolated from an Irish kefir grain, lacticin 3147 is one of the most extensively studied lantibiotics to date. In this study, the bacterial diversity of the Irish kefir grain from which L. lactis DPC3147 was originally isolated was for the first time investigated using a high-throughput parallel sequencing strategy. A total of 17 416 unique V4 variable regions of the 16S rRNA gene were analysed from both the kefir starter grain and its derivative kefir-fermented milk. Firmicutes (which includes the lactic acid bacteria) was the dominant phylum accounting for > 92% of sequences. Within the Firmicutes, dramatic differences in abundance were observed when the starter grain and kefir milk fermentate were compared. The kefir grain-associated bacterial community was largely composed of the Lactobacillaceae family while Streptococcaceae (primarily Lactococcus spp.) was the dominant family within the kefir milk fermentate. Sequencing data confirmed previous findings that the microbiota of kefir milk and the starter grain are quite different while at the same time, establishing that the microbial diversity of the starter grain is not uniform with a greater level of diversity associated with the interior kefir starter grain compared with the exterior.

Testing the corrosion resistance of stainless steels during the fermentation of probiotic drink

BACKGROUND

Over recent years, food producers have devoted much attention to the production of safe foods. Simultaneously, using advanced process technologies, it has been necessary to carefully select materials for use in process equipment. Milk and its products are exposed to metal surfaces from the time they are processed, through the various stages of handling and manufacture, to the packaging of the finished products for market. The selection of suitable materials for daily use in the dairy industry cannot be governed solely by their price and mechanical properties but must also take into consideration their influence on the quality of milk products.

RESULTS

This paper presents the results of testing the corrosion resistance of three stainless steels during the fermentation of a specific probiotic drink, kefir. Experiments were conducted using preliminarily activated kefir grains as a starter culture. Corrosion resistance was studied using a gravimetric and two electrochemical methods. The two steels showing the best corrosion performance differed mainly in their Mo and Nb contents.

CONCLUSION

The results indicated that Nb played the most protective role against corrosion during kefir fermentation, since the steel containing Nb but no Mo showed the lowest corrosion rate.

Codex recommendations on the scientific basis of health claims

BACKGROUND

Within the framework of Codex Alimentarius, attempts are being made at international level to establish guidelines for use of nutrition and health claims. An important issue that has to be addressed is the process of scientific substantiating of claims on foods.

OBJECTIVE

To provide an insight into the current step procedure of the proposed draft recommendations on the scientific basis of health claims. These Codex recommendations are intended to facilitate governments' own evaluation of health claims made by the industry.

METHODS

Review of comments of governments, observers and non-governmental organizations (NGOs) and relevant references to the proposed draft recommendations of the last sessions of the Codex Committee on Nutrition and Food for Special Dietary Uses (CCNFSDU). A literature search was performed using the PubMed database.

RESULTS/CONCLUSIONS

Several proposed draft recommendations on the scientific substantiation of health claims have been considered and amended by the CCNFSDU in recent years but the work is not yet complete. The current work draws on the work of FUFOSE and PASSCLAIM and also on that of WHO and FDA. Given the important role of Codex in food safety, the draft recommendations emphasize circumstances where additional evaluation of safety or nutritional safety needs to be considered. High quality human intervention studies are the prime evidence needed to substantiate claims but there is recognition that, in some cases, only observational studies may be available. Animal and in vitro studies will also be evaluated as part of the totality of the evidence. It has been suggested that the recommendations should include re-evaluation of claims after a certain time period, or if new evidence calls into question the scientific validity underpinning the claims. Setting out a common approach for the substantiation of health claims is an important step in the use of health claims around the world. There is a need to reflect emerging as well as consensus science. The substantiating evidence should be proportionate to the claim. Further progress in the elaboration of this relevant Codex text is needed to reach consensus.

Effect of fat replacers on kefir quality

The purpose of the study was to determine the effects of fat replacers on the quality of non-fat kefir. Skim milk fortified with Dairy Lo (DL) and inulin (INU) was fermented with kefir grains to manufacture kefir. The results of compositional, microbiological, rheological and sensorial analyses were compared with whole kefir (WK) and non-fat kefir (NFK) controls. Results for dry matter, pH and lactic acid ranged between 82.4 and 109.1 g kg(-1), 4.26 and 4.40, and 7.0 and 9.2 g L(-1), respectively. Acetaldehyde and ethanol contents of samples were between 2.89 and 7.28 mg L(-1), and 151.46 and 323.89 mg L(-1), respectively. In all samples, Lactobacillus spp., Streptococcus spp. and yeast counts were between 9.1 and 9.9, 9.3 and 9.9, and 5.2 and 5.6 log cfu mL(-1), respectively. Kefir samples had non-Newtonian behaviour and pseudoplastic fluid with thixotropy. At the first day, DL had the highest apparent viscosity (3.119 Pa s) while NFK had the lowest value (1.830 Pa s). In the sensory evaluation, odour and taste scores of samples were not different. Dairy Lo and inulin could be used without any adverse effect for the production of non-fat kefir.

The antiproliferative effect of kefir cell-free fraction on HuT-102 malignant T lymphocytes

Kefir is produced by adding kefir grains (a mass of proteins, polysaccharides, bacteria, and yeast) to pasteurized milk; it has been shown to control several cellular types of cancer, such as Sarcoma 180 in mice, Lewis lung carcinoma, and human mammary cancer. Human T-cell lymphotropic virus type 1 (HTLV-1) is the causative agent of adult T-cell leukemia, which is a fatal disease with no effective treatment. The current study aims at investigating the effect of a cell-free fraction of kefir on HuT-102 cells, which are HTLV-1-positive malignant T-lymphocytes. Cells were incubated with different kefir concentrations: the cytotoxicity of the compound was evaluated by determining the percentage viability of cells. The effect of all the noncytotoxic concentrations of kefir cell-free fraction on the proliferation of HuT-102 cells was then assessed. The levels of transforming growth factor (TGF)-alpha mRNA upon kefir treatment were then analyzed using reverse transcriptase polymerase chain reaction. Finally, the growth inhibitory effects of kefir on cell cycle progression and/or apoptosis were assessed by flow cytometry. The maximum cytotoxicity recorded at 80 microg/microL for 48 hours was only 43%. The percent reduction in proliferation was very significant, dose and time dependent, and reached 98% upon 60-microg/microL treatment for 24 hours. Kefir cell-free fraction caused the downregulation of TGF-alpha, which is a cytokine that induces the proliferation and replication of cells. Finally, a marked increase in cell cycle distribution was noted in the pre-G1 phase. In conclusion, kefir is effective in inhibiting proliferation and inducing apoptosis of HTLV-1-positive malignant T-lymphocytes. Therefore, further in vivo investigation is highly recommended.

The human microbiome and probiotics: implications for pediatrics

The “human super-organism” refers to the human body and the massive numbers of microbes which dwell within us and on the skin surface. Despite the large numbers of microbes co-existing within the human body, humans including infants and children achieve a physiologic state of equilibrium known as health in the context of this microbial world. These key concepts suggest that many individual members of the human microbiome, including bacterial and fungal species, confer different benefits on the human host. Probiotics, or beneficial microbes, may modulate immune responses, provide key nutrients, or suppress the proliferation and virulence of infectious agents. The human microbiome is in fact dynamic and often in flux, which may be indicative of the continuous interplay among commensal microbes, pathogens, and the human host. In this article we review the state-of-the-art regarding probiotics applications to prevent or treat diseases of the pediatric gastrointestinal and genitourinary systems. Additionally, probiotics may regulate local and systemic immunity, thereby reducing allergic disease severity and susceptibilities of infants and children to allergies and atopic diseases. In summary, beneficial microbes offer promising alternatives for new strategies in therapeutic microbiology with implications for different subspecialties within pediatrics. Instead of simply trying to counteract microbes with vaccines and antibiotics, a new field of medical microbiology is emerging that strives to translate human microbiome research into new probiotics strategies for promotion of health and prevention of disease in children.