Kefir Fermentation Research Articles

Investigation of Staphylococcus aureus growth and enterotoxin production during artisanal kefir fermentation

The behavior of two enterotoxigenic strains of Staphylococcus aureus (264 and 137) at two inoculation levels (ca. 2.3 and 4.2 log10 CFU/mL) was evaluated during artisanal kefir manufacture using three kefir grains (‘A’, ‘C’ and ‘K’) at two different grain-to-milk inoculation ratios [1 and 5% (w/v)]. Enumeration of S. aureus, lactic acid bacteria and yeasts was performed at different time points during milk fermentation at 25 °C, whereas enterotoxin production was evaluated at the end of fermentation (24 h post-inoculation). Enterotoxin was detected in four trials conducted using the 1% kefir grain-to-milk ratio and the higher S. aureus inoculum. Enterotoxin production was not detected in any of the trials conducted either with the lower S. aureus inoculum, the 5% grain-to-milk ratio, or kefir grain ‘C’. The results indicate that the growth and enterotoxin production of S. aureus during artisanal kefir-making can be influenced by all the factors studied, i.e. by the initial level of S. aureus contamination, the type of kefir grain used and the ratio of the kefir grain added to the milk. Artisanal kefir-makers should adhere to good hygiene practices and use the 5% grain-to-milk ratio scheme to minimize the risk of enterotoxin production.

Proteomic characterization of kefir milk by two-dimensional electrophoresis followed by mass spectrometry.

Kefir is a type of fermented milk obtained thanks to the introduction of "kefir grains" in mammalian milk. Kefir grains consist of lactic and acetic acid bacteria and yeasts in alternative proportions that are held together by a matrix of complex sugars known as "kefiran." Thanks to the fermentative process, the kefir milk is rich in nutraceutical substances such as amino acids, vitamins, and mineral salts. The most valuable compounds of kefir fermentation are mainly lactic acid, exopolysaccharides, and bioactive peptides, the resulting products of proteolytic release from milk proteins (caseins and whey proteins). Among the nutraceutical properties of kefir are antimicrobial and antitumor activity, immunomodulating effect, and cholesterol-lowering effect. Therefore, in light of these intriguing properties of kefir milk, in this work, a proteomic analysis, by two-dimensional electrophoresis followed by mass spectrometry, has been performed. As a result, milk-derived polypeptides were identified in commercial kefir milk from organic farming. In particular, polypeptides deriving from κ-, αs1 -, and αs2 -caseins that may have potentially beneficial effects on human health have been detected.

Effectof Fermented Kefir Consumption Mixed with Different Cereals Formula on Obese Rats تأثیر تناول الکفیر المخمر المخلوط بترکیبات مختلفة من الحبوب على الفئران البدینة

This study investigates the ant obesity effects of fermented Kefir and germinated cereals mixed with fermented Kefir on high fat diet induced obese rats. 25male rats each weighting 75±3 gram were apportioned to five groups. Group 1 is the negative group. The rest rats were received high saturated fats (34%) in diet for 56 days to become obese rats. Obesity was confirmed by elevation of serum lipid profile and body weight. Group 2 is control +ve group which fed on high fat diet, Kefir group which fed on high fat diet supplemented with kefir at dose of 4ml /rat/day orally, formula 1 group which fed on high fat diet with 20 % of formula 1(wheat, barley, maize and millet mixture powder melt in 200 ml kefir)and formula 2 group which fed on high fat diet with 20 % of formula 2(wheat, barley, maize and oat mixture powder melt in 200 ml kefir) for four weeks. This study resulted in a marked improvement of nutritional indicator as kefir Formula 1 and 2 group administration could lower nutritional indicators. However, the administration of kefir, formula1 and formula 2 could reduce lipids parameters.Consumption of kefir significantly reduced the serum leptin, glucose, insulin resistance and progesterone levels but increased insulin and testosterone levels while consumption of formula 1 and 2 could lower serum leptin and insulin resistance and elevate progesterone and testosterone levels compared to control (+ve) group .It is concluded that germinated cereals mixed with kefir could manage treat obesity.

A Non-yeast Kefir-like Fermented Milk Development with Lactobacillus acidophilus KCNU and Lactobacillus brevis Bmb6.

The use of yeast assist kefir fermentation, but also can cause food spoilage if uncontrolled. Hence, in this study, the microbial composition of an existing commercial kefir starter was modified to produce a functional starter, where Lactobacillus acidophilus KCNU and Lactobacillus brevis Bmb6 were used to replace yeast in the original starter to produce non-yeast kefir-like fermented milk. The functional starter containing L. acidophilus KCNU and L. brevis Bmb6 demonstrated excellent stability with 1010 CFU/g of total viable cells throughout the 12 weeks low-temperature storage. The newly developed functional starter also displayed a similar fermentation efficacy as the yeast-containing control starter, by completing the milk fermentation within 12 h, with a comparable total number of viable cells (108 CFU/mL) in the final products, as in control. Sensory evaluation revealed that the functional starter-fermented milk highly resembled the flavor of the control kefir, with enhanced sourness. Furthermore, oral administration of functional starter-fermented milk significantly improved the disease activity index score by preventing drastic weight-loss and further deterioration of disease symptoms in DSS-induced mice. Altogether, L. acidophilus KCNU and L. brevis Bmb6 have successfully replaced yeast in a commercial starter pack to produce a kefir-like fermented milk beverage with additional health benefits. The outcome of this study provides an insight that the specific role of yeast in the fermentation process could be replaced with suitable probiotic candidates.

Influence of Conventional Fermentation on Antioxidant Activity and Phenolic Contents of Two Common Dairy Products: Yogurt and Kefir

During conventional fermentation of milk into yogurt and kefir, changes of antioxidant capacities (DPPH radical scavenging, ferrous chelating, reducing power, hydrogen peroxide/ H2O2 scavenging activity) and total phenolic content were investigated. Both products showed greater phenolic content, DPPH radical scavenging, and reducing power activities than was the case of their unfermented milk forms. But they were unable to scavenge H2O2. Chelating ability of milk increased by yogurt fermentation but decreased by kefir fermentation. In general, antioxidative capacity of milk improved throughout conventional yogurt and kefir fermentations and ripening periods (except chelating ability for kefir and H2O2 scavenging). This study is valuable since it evaluates the antioxidant power of yogurt and kefir produced by traditional fermentation with 5 different antioxidative approaches. In face of rapidly rising consumer demand for safe, healthy, functional but natural foods, revealed results might strengthen importance of conventional fermentation process and highlight the antioxidative contributions of mentioned products

Kefir in the Prevention and Treatment of Obesity and Metabolic Disorders.

This review summarizes recent animal and human trials examining the potential for kefir to improve obesity, type 2 diabetes, dyslipidemia, and non-alcoholic fatty liver disease (NAFLD). Evidence for pathways affected and suggestions of possible mechanisms of action are also considered. Human trials examining the ability of kefir to recapitulate metabolic health benefits previously observed in rodent models have found mixed results. Kefir has long been associated with improvements in health including obesity, diabetes, NAFLD, and dyslipidemia in preventative animal trials. While recent evidence from human trials supports a positive role of kefir in modulating diabetes-related markers, the impact of kefir consumption on markers of dyslipidemia, NAFLD, and body composition has been for the most part contradictory to animal findings. Variability in organisms for kefir fermentation poses a significant challenge in making meaningful comparisons. Recommendations for future well-controlled animal and human research are provided.

Symbiotic Effects of Kefir and Yacon Flour (Smallanthus sonchifolius) on Bone Remodeling in Rats

Abstract Objectives Kefir is a natural source of probiotics that confer benefits to the host's intestinal health. Yacon (Smallanthus sonchifolius) is a tuberous root originating in the Andes region, rich in prebiotic fructooligosaccharides (FOS), which increases the absorption of minerals. The objective of this study was to evaluate the prebiotic properties of yacon, the probiotic effect of kefir and the symbiotic action of the association between them in bone health in rats. Methods Adult Wistar rats were divided into 4 groups (n = 10): Group C (Control), Y (yacon flour, 51.34% FOS) K (kefir, 10⁷ UFC/mL), and YK (yacon flour + kefir). Group C received AIN-93 M + cow's milk (1 mL/day), group Y received AIN93 diet added by yacon flour to provide 5% FOS + cow's milk, group K received fermented kefir (1 mL/day), and group YK received yacon flour + fermented kefir. Feces and urine were collected for calcium balance in the last week of the experiment. At the end of 6 weeks, the animals were euthanized and the large intestine and blood sample were collected for analysis of intraluminal pH (pH meter Kasvi®) and biomarkers of bone remodeling, respectively. Calcium from diet, feces and urine was analyzed by atomic absorption. Osteocalcin (OC -- EL-R0243), C telopeptide of type I collagen (CTX – EL-R1456) and N telopeptide of type I collagen (NTX – EL-R0276) were analyzed by ELISA, according to manufacture's instructions (Elabscience, TX, USA). The results were analyzed by ANOVA, followed by the Tukey test (p < 0.05), using GENES®. Results No significant differences were observed between groups concerning calcium balance and cecal pH, although pH was slightly lower in the groups fed yacon (Y and YK). Biomarkers of bone formation (OC) and bone resorption (CTX and NTX) were significantly lower in group K (OC = 7.29; CTX = 4.04; NTX = 94.31 ng/mL), compared to the control (OC = 16.33; CTX = 5.68; NTX = 105.97 ng/mL). Groups Y (OC = 13.63; CTX = 5.13; NTX = 114.34 ng/mL) and YK (OC = 15.37; CTX = 5.17; NTX = 132.51 ng/mL) did not differ from the control. Conclusions Prebiotic (Y) and Symbiotic (YK) were more effective than kefir in bone remodeling in rats, although fermentation in the large gut did not reduce pH sufficiently to improve calcium absorption and retention. Funding Sources FAPES; CNPq and CAPES/Brazil.

Kefiran Ekstraktının Bazı Bitki Patojeni Bakterilerine Karşı Antimikrobiyal Etkisinin Değerlendirilmesi

Kefir; laktik asit bakterileri, asetik asit bakterileri ve mayalar gibi çok çeşitli mikroorganizmaları barındıran granüller tarafından üretilen, pek çok ülkede geleneksel olarak tüketilen fermente bir süt içeceğidir. Granülleri çevreleyen ve ağırlıklı olarak kefiran molekülünden oluşan polisakkarit yapının sağlığı teşvik edici birçok etkisinin yanında çeşitli patojenlere karşı antimikrobiyal etkiye sahip olduğu bildirilmektedir. Bu çalışmada, biri ticari olarak satılan, diğeri yerel bir satıcıdan temin edilen granüller kullanılarak 24 saatlik fermantasyonla kefir üretimi yapılmıştır. Olgunlaşan kefir tanelerinden kefiran ekstraktı eldesi ve saflaştırılması etanol presipitasyon yötemi ile 80°C, 90°C ve 100°C olmak üzere üç farklı sıcaklıkta gerçekleştirilmiştir. Ayrıca elde edilen ekstrakt solüsyonlarının protein içerikleri Bradford yöntemiyle ile belirlenmiştir. Denemelerde kullanılan ekstrakt solüsyonlarının protein içeriği 0,001 g/mL olarak ölçülmüştür. Oluşturulan stok solüsyonlarından, 0,05, 0,1, 1 ve 2 mg ekstrakt içeren uygulamaların Pseudomonas, Xanthomonas, Erwinia ve Clavibacter cinslerine ait bazı bitki patojeni bakterilere karşı antibakteriyel etkisi in vitro koşullarda ilk defa incelenmiştir. Bu amaçla disk difüzyon metodu ve yayma yöntemi olmak üzere iki metot kullanılmıştır. Denemelerde pozitif kontrol olarak kullanılan AN kefir süpernatantı izolatlar üzerinde ortalama 13-17 mm inhibisyon zonu gösterirken, SD süpernatantı 10-14 mm zon üretmiş ancak kefiran ekstralarının antibakteriyel etkisi gözlemlenmemiştir.

Antibacterial activity of colostrum kefir against foodborne pathogen bacteria

Colostrum is the first fluid produced from the mammary gland 24 to 72 hours after the postpartum. Here, we have the psychochemical characteristics of fermented colostrum that fermented with kefir grain for 24 and 48 hours and its activity against eight foodborne pathogens. Bacillus cereus, Bacillus pumilus, Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, Salmonella Typhi, Pseudomonas aeruginosa, and Klebsiella pneumoniae were used as test strains, and antibacterial activity was investigated based on inhibitory zones using disc diffusion methods. Psychochemical characteristics and activity varied according to colostrum kefir type and fermentation time. The widest and the strongest antimicrobial activity is obtained after at least 48 hours of fermentation for all colostrum kefir, although the traditional kefir fermentation method is for 18-24 hours at 25 °C. For the type of colostrum kefir K1, K2, P1, and P2 after fermentation for 48 h, it shows that antimicrobial activity increase along with the increasing of titrable acidity and decrease in pH value.

Changes in carbohydrate profile in kefir fermentation

The changes in microbial growth, pH and lactic acid content of traditional kefir were determined during fermentation (0-18 h) and cold storage (4°C for 1-7 days). A high-performance liquid chromatographic method was used to detect the carbohydrates and possible naturally occurring galactooligosaccharides (GOS) and their changes during fermentation and storage. The microbial content (Lactobacillus spp., Lactococcus spp., Lactobacillus acidophilus, Bifidobacterium spp., and yeasts) increased during fermentation and did not significantly change during seven-day cold storage. The highest content was observed for L. acidophilus (9 log CFU/mL) after 7 days of storage. The lactic acid gradually increased during the fermentation and stayed stable during the storage. The lactose content significantly reduced during the fermentation period. It was observed that possible GOSs detected in kefir samples remained stable during the storage. Because GOS are known as prebiotics to stimulate the resistance of probiotics, these results might help to estimate the changes of naturally occurring GOS content during fermentation and storage of traditional kefir.

Antibacterial Activity of Kefir Grain Levels on Fermented Goat Milk

The purpose of this study was to determine the antibacterial activity of the use of kefir grains in goat’s milk. Preliminary tests included the total lactic acid bacteria and yeast. The main research includes syneresis test, total plate count, Escherichia coli and Staphylococcus aureus inhibition test using the disc method. The study used a non-factorial randomized complete design with 3 treatments and 6 replications. Kefir grains presentation were 5%, 10%, and 15%. The results showed that the population of lactic acid and yeast bacteria was 9.3 × 109 and 1.2 × 107, respectively. The syneresis values were 5%, 10% and 15% by kefir grain addition 36.60%, 52.07% and 52.05%, respectively. The highest total number of microbes was obtained from the use of 5% yeast (7.67 log cfu.ml−1). The highest antibacterial ability was shown in the use of 5% yeast, each of which was 2.19 mm against Escherichia coli and 2.50 mm against Staphylococcus aureus. The results of the study concluded that kefir fermentation in goat milk has not been able to inhibit Escherichia coli and Staphylococcus aureus growth.

Development of a novel probiotic milk product with enhanced antioxidant properties using mango peel as a fermentation substrate

Abstract Mango peel is an agroindustrial waste with excellent nutritional value and a considerable content of bioactive compounds that can be used as a source of antioxidants. Additionally, biotransformation processes by kefir fermentation increase the interest in obtaining products from agroindustrial wastes with good biological properties. In this context, this work aimed to evaluate the effects of milk supplementation with mango peels on the growth rates of kefir microorganisms during fermentation as well as the antioxidant properties of the obtained fermented products. The results were comparatively evaluated between fermented samples in the presence of mango peels (KMP) and in their absence (KC). Significant increases (p ≤ 0.05) in antioxidant activities for KMP were observed for all methods, as follows: 113% for DPPH-radical scavenging (10 h of fermentation), 153% for the Ferric Reducing Antioxidant Power (FRAP) assay (8 h of fermentation), 21% for ABTS-radical scavenging (6 h of fermentation) and 43% for Total Reducing Capacity (Folin-Ciocalteu method) (8 h of fermentation) compared to those of KC fermented samples. According to microbiological analyses, the KMP samples allowed microbial growth of up to 3-fold higher than the growth of KC samples, reaching counts of up to 108 CFU/mL for lactic acid bacteria. According to the results, the products obtained from the fermentation process using milk combined with mango peels as the substrate presented improved antioxidant properties and a potential probiotic property.

Kefir fermentation as a bioprocess to improve lentils antioxidant properties: is it worthwhile?

Abstract Kefir, a consortium of acetic and lactic bacteria and yeasts, is versatile for biotransformation of vegetable substrates and may improve their bioactive properties. Lentil is a legume rich in vitamins, minerals, complex carbohydrates and proteins, making it an excellent substrate for fermentation and obtaining bioactive molecules. We report the effect of different process variables on antioxidant properties of lentil extracts obtained using kefir as a biotransformation agent and experimental design. The results showed that the factors agitation (rpm) and incubation temperature exerted significant effects. Incubation temperature of 28 °C and agitation of 75 rpm were the most suitable conditions for kefir fermentation and maximizing the antioxidant properties of the fermented lentils. The highest antioxidant activities for fermented products were 4128.39, 35.87 and 23.20 μmol of Trolox equivalents per gram of sample (μmoL TE g-1) measured by Total Antioxidant Capacity, FRAP and DPPH-radical scavenging methods, respectively. Additionally, we detected that the initial fermentation times (in the first six hours) were enough to positively affect the antioxidant properties of the lentil extracts, reaching a percentage increase of up to 270% in the antioxidant activity of the fermented products in relation to those non-fermented samples.

The metagenome-assembled genome of Candidatus Oenococcus aquikefiri from water kefir represents the species Oenococcus sicerae

Recently, a metagenomic study of a water kefir fermentation ecosystem enabled the reconstruction of a metagenome-assembled genome (MAG) of an Oenococcus species that was different from the three species of this genus known so far. Therefore, the name Candidatus Oenococcus aquikefiri was proposed for this novel Oenococcus species. In the meantime, however, a fourth member of the genus, Oenococcus sicerae, isolated from French cider, was reported. The comparison of its genome sequence with the Candidatus O. aquikefiri MAG showed an average nucleotide identity (ANI) value of 98.53%. In addition, the 16S rRNA and pheS genes of the two species were 99.4% and 99.9% identical, respectively. As the presence of O. sicerae in a water kefir metagenome was also revealed by metagenomic recruitment plotting, it can be stated that Candidatus O. aquikefiri and O. sicerae belong to the same species. Intraspecies variations include the presence or absence of a citrate lyase operon and components of various phosphotransferase (PTS) transport systems.

The Buffer Capacity and Calcium Concentration of Water Influence the Microbial Species Diversity, Grain Growth, and Metabolite Production During Water Kefir Fermentation.

Eight water kefir fermentation series differing in buffer capacity and calcium concentration of the water used for fermentation were studied during eight backslopping steps. High buffer capacities resulted in high pH values and high calcium concentrations resulted in low pH values at the end of each backslopping step. When the water buffer capacity and/or calcium concentration were below certain minima, the water kefir grain growth decreased gradually over multiple backsloppings. High water buffer capacities resulted in high concentrations of residual total carbohydrate concentrations and low metabolite concentrations. Further, high water buffer capacities resulted in high ratios of lactic acid bacteria to yeasts, which was reflected in high molar ratios of the concentrations of lactic acid to ethanol and acetic acid to ethanol. The most prevalent microorganisms of the water kefir grain inoculum and grains of all fermentation series at the end of the eighth backslopping step were Lactobacillus hilgardii, Lactobacillus nagelii, Lactobacillus paracasei, Bifidobacterium aquikefiri, Saccharomyces cerevisiae, and Dekkera bruxellensis. These microbial communities were influenced by the water buffer capacity and had an impact on the substrate consumption and metabolite production during water kefir fermentation.

Pengaruh Varietas dan Lama Fermentasi Terhadap Kualitas Kefir Susu Kacang Tanah (Arachis Hypogaea)

Kefir is one fermented product that has a taste, a yogurt-like consistency color and has a distinctive yeast aroma. Peanuts are economically ranked second after soybeans. As peanut food has important nutritional benefits in the human nutriency of high protein, minerals and essential fatty acids such as linoleic and oleic acids. Peanut milk contains a very high amino acid almost equivalent to the protein content of animal milk and the price is relatively cheap This study aims to determine the effect of varieties and length of fermentation on the quality of peanut milk kefir. The research design used was Completely Randomized Design (RAL) consisting of 2 factor V peanut varieties consisting of 2 levels (Hypoma 1 and Singa) and long L fermentation factor consisting of 3 levels (21, 24 and 27 hours), each of which was repeated 3 times. The observed observations were pH, total acid, alcohol content, protein content, fat content, Total Plate Count (TPC), Texture Profile Analysis (TPA). Treatment of varieties and duration of fermentation of peanut milk kefir have significant effect on pH value, total acid, fat content, Total Plate Count (TPC), significantly affect alcohol content and no significant effect on protein content, Texture Profile Analysis (TPA), organoleptic aroma, taste and texture. Quality of peanut milk kefir produced on lion varieties with 24 hours fermentation time of total acid 6.43%, alcohol content 2.84%, protein content 2.80%, Total Plate Count (TPC) 30.67 x 103 CFU and Adhesiveness 1.324 g/s.

Microbial composition of Korean kefir and antimicrobial activity of Acetobacter fabarum DH1801

AbstractKefir is a probiotic dairy product containing multiple species of lactic acid bacteria, acetic acid bacteria, and yeast, with varying microbial composition depending on geographical origin. In the present study, we characterized the acetic acid bacterial population in Korean kefir by next‐generation sequencing‐based community analysis and isolated a novel acetic acid bacterial strain, Acetobacter fabarum DH1801. To evaluate its potential application in the food industry, the antimicrobial activity of A. fabarum DH1801 against seven foodborne pathogens (Bacillus cereus, Staphylococcus aureus, Listeria monocytogenes, Cronobacter sakazakii, Salmonella Enteritidis, enterotoxigenic Escherichia coli, and Shigella flexneri) was analyzed by growth curve analysis. Remarkably, the culture filtrate of the novel isolate inhibited the growth of all seven pathogenic bacteria in a dose‐dependent manner, which was superior to acetic acid solution of same pH value. Our findings suggest that the A. fabarum DH1801 strain forms a protective barrier during kefir fermentation against contamination by foodborne pathogens.

Gelado comestível de kefir adicionado de polpa de jabuticaba e morango

A crescente busca dos consumidores por alimentos diferenciados, que além de exercer suas funções básicas, apresentem também benefícios à saúde de quem os consome, tem proporcionado o desenvolvimento de novos produtos alimentícios. Dessa forma, buscou-se desenvolver um gelado comestível inovador, utilizando leite fermentado de kefir. Este foi adicionado de polpa de jabuticaba e morango e avaliado quanto à qualidade físico-química e microbiológica após 60 dias de armazenamento a temperatura de -2 °C. O gelado comestível apresentou significativos teores de compostos fenólicos e atividade antioxidante e, ainda, valores consideráveis de bactérias láticas (1,0.108 UFC.g-1) e bolores e leveduras (7,6.107 UFC.g-1) durante o período de armazenamento. A análise sensorial do produto, realizada nos tempos 0, 30 e 60 dias de armazenamento, demonstrou que o produto apresenta aceitabilidade superior a 80%, nos atributos textura, odor, sabor e cor. Conclui-se que o produto pode ser uma alternativa promissora na oferta de alimentos com potencial funcional, apresentando qualidade sensorial e microbiológica durante os 60 dias de armazenamento.

Sugary Kefir: Microbial Identification and Biotechnological Properties

Background: The aim of the present study was to assess the microecosystem composition of three different fruit kefir grains used for the fermentation of apple juice (NAJ), cherry juice (SCN), and a solution of sugary water, enriched with plums (BSS). Methods: Yeast and bacterial populations were enumerated using classical microbiological techniques, clustered by RAPD-PCR genotyping, and identified by sequencing of the D1/D2 region of 26S-rRNA gene and the V1-V3 region of 16S-rRNA gene, respectively. The caseinolytic/lipolytic activities and the production of antimicrobial compounds were assessed by well diffusion assays. The proteolytic and lipolytic capacity were further assessed by SDS-PAGE and titrimetric assay, respectively. Results: Yeast and bacterial populations were enumerated at 6.28, 6.58, and 6.41 log CFU/g and at 4.32, 4.85, and 4.34 log CFU/g, regarding BSS, NAJ, and SCN, respectively. Saccharomyces cerevisiae dominated all three sugary kefir grains; Kluyveromyces marxianus formed a secondary microbiota in BSS and NAJ. Bacillus amyloliquefaciens dominated NAJ and SCN; Lactobacillus rhamnosus dominated BSS. Four bacteria and nine yeast isolates exhibited proteolytic activity. Forty bacteria and 45 yeast isolates possessed lipolytic activity. No antibacterial activity was detected. Conclusions: Prevalence of yeast over bacterial populations was evident in all samples assessed. Several bacterial and yeast strains exhibited proteolytic and lipolytic activities, making them suitable candidates for inclusion in starter cultures for milk and sugary kefir fermentation.

Survival of Escherichia coli O157:H7 and Staphylococcus aureus during the fermentation and storage of kefir

Abstract The survival of Escherichia coli O157: H7 and Staphylococcus aureus, which are foodborne pathogens was investigated during fermentation and storage of kefir. The kefir grains were inoculated with 5% of the whole fat UHT cow milk and the E. coli O157: H7 and S. aureus cultures were added separately to give 105 cfu mL-1 and left to incubate at 22 °C for 24 hours at first stage. During the incubation, the bacteria and yeast counts, pH and titratable acidity amounts were determined. In the second stage, E. coli O157: H7 and S. aureus cultures were separately added to produce 105 cfu mL -1 of kefir and was stocked at 5 °C for 3 days. Every day samples were taken and the same tests were done. During fermentation, in all samples the initial while TA was 0.14%, the fermentation was 1.0% and 1.01% at the end. The kefir samples were pH 4.5 at the end of the 3 day period of storage. S.aureus was significantly inhibited while E.coli was not inhibited during the fermentation process. During storage, E. coli O157: H7 and S. aureus were inhibited within 2 days. The kefir has the quality of being a healthy product during fermentation and storage.