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The goal of this work has been to assess the influence of a health-promoting hydrocolloid, such as kefiran,in oil-in-water emulsions (O/W: 50/50) containing whey protein isolate (1.0% wt.). Different kefiran concentration levels (0%, 0.25%, 0.5%, 1% wt.) were studied, observing a shift from a fluid-like to asolid-like behaviour and higher viscosities when kefiran content increased. A pseudoplastic behaviour was detected for all systems studied. The observed evolution is attributed to the thickening effect exerted by kefiran, which promoted stability, in spite of observing a certain flocculation degree within the emulsion systems, demonstrated through the addition of sodium dodecyl sulphate (1% wt.). Furthermore, shortterm stability of these pseudoplastic emulsions has been verified by laser-scattering techniques. Thus, a Sauter diameter around 1 μm remained unaltered up to 7 days since preparation. The addition of kefiran in the formulation would benefit from their well-known health-promoting effects. Fil: Piermaria, Judith Araceli. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; Argentina Fil: López Castejón, María Luisa. Universidad de Sevilla; España Fil: Bengoechea, Carlos. Universidad de Sevilla; España Fil: Guerrero, Antonio. Universidad de Sevilla; España Fil: Abraham, Analia Graciela. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; Argentina

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.

The main goal of this work was to characterise and quantify the exopolysaccharide kefiran and to discover an effective procedure for its isolation from kefir grains, originating from the Caucasian Mountains. Capillary electrophoresis was used for the characterisation and quantification of the d-glucose and d-galactose in our samples at a mass ratio of 1:0.7. The effect of fermentation time on growth of kefir grains and the content of kefiran within the grains were determined. The pH profiles were monitored dynamically. In addition, the influence of fermentation temperature on kefir grains mass concentration (γKG) and the content of kefiran within the grains (wKEF/KG) were studied. The highest values for both were obtained at 30 °C.

The tolerance of lactic acid bacteria (LAB) from kefir grains to gastrointestinal tract conditions was evaluated in vitro. The effects of pH values and bile salts on the viability of LAB were investigated. The results demonstrated that pH value showed a significant effect on the viability. The viable counts exhibited a reduction of 1.5 to 2 log cycles in 0.3% to 0.5% bile salts after 4 h. The viability of LAB exposure to sequential simulated gastric and intestinal juices was assessed by response surface model (RSM). RSM indicated that the gastric pH and gastric contact time significantly affected the viability (P < 0.05), while the effect of intestinal contact time was not significant. Moreover, RSM revealed the interactions of pH and gastric contact time, and of pH and intestinal contact time. The LAB cells, temporarily damaged by the low pH of gastric juice (pH < 2), could recover in the intestinal juice; and the longer the intestinal contact time, the higher the viability of LAB. RSM proved to be a useful and accurate method to predict the viability of LAB under certain laboratory conditions by the model validation. This study indicated that LAB from kefir grains exhibited excellent tolerance to sequential simulated gastrointestinal tract conditions, and that kefiran possessed a significant protective effect on LAB in hostile environments.

BACKGROUND: Kefiran is an exopolysaccharide that is widely used in the food and pharmaceutical industries. The aim of this study was to demonstrate that kefiran with different chemical structures can be obtained by changing the composition of the Lactobacillus kefiranofaciens fermentation medium. RESULTS: When using maltose as the sole carbon source: (1) the average molecular mass of kefiran was 1.5 × 105 Da, only 62.5% of that of the control (with lactose as the sole carbon source); (2) the glucose/galactose molar ratio of kefiran from the optimised medium was 1:10; (3) two variable-angle CH bonds existed in the structure of kefiran; (4) the maximum viscosity of kefiran was [η] = 73.86 ± 5.3 dL g−1 and its specific rotatory power was [α]D = + 68°. Increasing the proportion of maltose in a mixed carbon source (maltose and lactose) from 20 to 100 g L−1 decreased the average molecular mass and glucose/galactose molar ratio of kefiran by 35 and 60% respectively. CONCLUSION: Kefiran with different chemical structures was obtained by changing the composition of the fermentation medium. The results presented here will facilitate further study of the relationship between the chemical structure and biological role of kefiran. Copyright © 2008 Society of Chemical Industry

Lactobacillus kefiranofaciens was reported to produce an exopolysaccharide named kefiran. In the present study, we developed a new medium, rice hydrolyzate (RH) medium, for the culture of L. kefiranofaciens. Structural analyses revealed that the exopolysaccharide produced by L. kefiranofaciens from RH medium was composed of a hexasaccharide repeating unit, and essentially identical to the kefiran reported in previous studies. A study on the effects of kefiran in animals demonstrated that kefiran significantly suppressed increase of blood pressure and reduced the serum cholesterol levels in SHRSP/Hos rats when subjects consumed excessive dietary cholesterol. Kefiran supplementation demonstrated the ability to significantly lower blood glucose in KKAy mice. In addition, the administration of kefiran in constipated SD rats caused an obvious improvement in the levels of fecal moisture and wet weights of feces. These results suggest that kefiran could be used as a functional food to prevent some commonly occurring diseases.

Summary The native bacteria and yeasts present in Portuguese keWr grains stored under fourdistinct sets of environmental conditions have been isolated and identi Wed on the basis ofmorphology and biochemical tests. The microbial population of the keWr grains as awhole has been characterized in terms of rates of biomass production and formation oflactic acid and ethanol. The rheological properties of the puri Wed polysaccharide (ke Wran)produced by the microXora of the grains and accumulated therein were studied in a lowwater activity solvent and as a component of a binary gel containing either k-carrageenanor xanthan gum. Keywords Biochemical parameter, dairy foods, gum blend behaviour, keWran, mechanical spectra, storage and lossmoduli. Introduction KeWr is a fermented beverage which has itsancient origins in the Caucasian mountains. Thislight alcoholic beverage is prepared by inocula-tion of raw milk with existing keWr grains (whichcan be stored in dried form). KeWr grains exhibitan irregular surface and they consist of a gelmatrix in which yeasts and bacteria are imbeddedand live symbiotically. The microXora of keWr grains, which dependson their origin (Ottogalli et al., 1973), storageconditions and handling pattern (Zourari A Kandler & Kunath, 1983), althoughseveral other varieties can be found, e.g. bacteri-al species of such genera as Streptococcus,Leuconostocand Acinetobacter(Rosi, 1978b; Rosi& Rossi, 1978), and mould species such asGeotrichum candidum(Kosikowski, 1977). Atleast one quarter of the dry matter of the keWrgrains consists of a capsular polysaccharideusually denominated keWran (La Reviere et al.,1967). KeWran is considered to be a result of the metabolism of such capsular bacteria as Lactobacillus kefis(La Reviere et al., 1967; Yokoi et al., 1990), a homofermentative, atypi-cal Streptobacterium (Rosi & Rossi, 1978),Lactobacillus kefiranofaciens(Toba et al., 1987;Fujisawa et al., 1988), and a new LAB strain ten-tatively named KPB-167B (Yokoi et al., 1991).KeWran consists of approximately equal propor-tions of galactose and glucose residues (Kooiman,1968). Rheological studies have shown thatkeWran itself has a very low viscosity in solutionand is unable to form rigid gels in the absence ofethanol (Mukai et al., 1990, 1991). Although thestructural characteristics and hydrodynamic prop

Carboxymethyl (CM-) kefiran was prepared with monochloroacetic acid in isopropyl alcohol at 30, 40 and 50°C for 4 and 24 hr. Resulting CM-kefiran varied in degree of substitution (0.73-0.89), molecular weight (5.0-7.0 × 105) and viscosity (4.5-14.5 cP in 0.5% aqueous solution) depending on the conditions. Carboxymethylation resulted in a maximum fourteenfold increase in viscosity. 13C-NMR spectra of CM-kefiran indicated C-6 of native kefiran was preferentially substituted with CM-groups.