Biomedical subjects

J C Vuillemard

Publications and source records attributed to J C Vuillemard.

8 recordsLinked to original sources

PubMed2005

Microentrapment of probiotic bacteria in a Ca(2+)-induced whey protein gel and effects on their viability in a dynamic gastro-intestinal model.

Entrapping probiotic bacteria in gels with ionic cross-linking is typically achieved with polysaccharides (alginate, pectin, carraghenan). In this study, whey proteins were used for this purpose by carrying out the Ca(2+)-induced gelation of pre-heated whey protein isolate (WPI). A Lactobacillus rhamnosus cell suspension was added in a denatured WPI solution in a 30 : 70 volume ratio. Gelation was carried out by extrusion of the cell suspension in a CaCl(2) solution. Beads of approximately 3 mm diameter were formed. The population in the beads was 8.0 x 10(8) cells g(-1). Entrapment efficiency in gel beads was 96%, with a survival level of 23%. Scanning electron microscopy of beads before freeze-drying showed a tight protein network containing encapsulated Lb. rhamnosus cells homogeneously distributed throughout the matrix. The survival to freeze-drying of the bead-entrapped cells was 41%. Viability of microentrapped cells in a dynamic gastro-intestinal (GI) model was studied and the results were compared to free cells freeze-dried in a milk-based cryoprotective solution, as well as in a pre-denatured WPI solution. Results showed that protein gelation provided protection against acidic conditions in the stomach after 90 min, as well as against bile after 30, 60 and 90 min in the duodenum. Moreover, the milk-based cryoprotective solution was equally effective after 90 min in the duodenum. It is concluded that the gelation of whey proteins induced by Ca(2+) ions can protect the cells against adverse conditions of the GI system. However, certain stages in the entrapment process, particularly extrusion in the solution of CaCl(2), still need to be optimized in order to reduce the mortality of the cells during gelation.

Calcium↗

PubMed2004

Impact of autolytic, proteolytic, and nisin-producing adjunct cultures on biochemical and textural properties of cheddar cheese.

The effect of incorporating a highly autolytic strain (Lactobacillus delbrueckii subsp. bulgaricus UL12) a proteolytic strain (Lactobacillus casei subsp. casei L2A), or a nisin Z-producing strain (Lactococcus lactis, subsp. lactis biovar diacetylactis UL719) into Cheddar cheese starter culture (Lactococcus lactis KB and Lactococcus cremoris KB) on physicochemical and rheological properties of the resultant cheeses was examined. Cheeses were ripened at 7 degrees C and analyzed over a 6-mo period for viable lactococcal and lactobacilli counts, pH, titratable acidity (TA), lipolysis, proteolysis, and textural characteristics. The combination of the nisin-producing strain and autolytic adjuncts significantly increased the production of water-soluble nitrogen, free amino acids, and free fatty acids. The effect of Lc. diacetylactis UL719 alone or of Lb. casei L2A on water-soluble nitrogen and free amino acid contents were also significant, whereas their effect on free fatty acids was not. Viable counts of Lb. bulgaricus UL12 were significantly reduced in the presence of Lc. diacetylactis UL719. Lactobacilli-containing cheeses showed significantly lower values for hardness, fracturability, and springiness. It could be concluded that the addition of Lb. bulgaricus UL12 together with a nisin-producing strain produces a greater increase in cheese proteolysis and an improvement in Cheddar cheese texture.

Cheese↗

PubMed1999

Production of probiotic cheese (cheddar-like cheese) using enriched cream fermented by Bifidobacterium infantis.

Probiotic cheeses (Cheddar-like cheese) were produced with microfiltered milk standardized with cream enriched with native phosphocaseinate retentate and fermented by Bifidobacterium infantis. During the manufacture and storage of cheeses, viability of the bifidobacteria was determined. Biochemical changes such as proteolysis, sugar metabolism, and organic acids production were estimated. No bifidobacteria growth was observed during cheese-making steps. Bifidobacteria survived very well in cheeses packed in vacuum sealed bags kept at 4 degrees C for 84 d and remained above 3 x 10(6) cfu/g of cheese. No significant difference was observed between cheeses produced with or without bifidobacteria for fat, protein, moisture, salt, ash, or pH. After 12 wk of storage, more than 56% of the as1-CN was hydrolyzed in cheeses that were produced with bifidobacteria and inoculated at 10(8) cfu/g in the cream, and > 45% of hydrolysis was observed in the control cheese. However, no significant differences in the electrophoretic sodium dodecyl sulfate-PAGE patterns were observed in cheeses at any period of storage. At the first day after manufacture, lactose was completely hydrolyzed in cheeses made with bifidobacteria, which suggested high beta-galactosidase activity by B. infantis. Small quantities of acetic acid were detected in bifidus cheeses. The results indicated that B. infantis introduced into hard pressed cheese exhibited excellent viability during storage for 12 wk and could be metabolically active.

Bifidobacterium↗

PubMed1998

Release of enzymes from liposomes during cheese ripening.

Changes in proteolysis and in residual enzymatic activity as a function of time were compared in model cheeses, made with either free enzymes or liposomes containing enzymes and in control model cheeses. Cheeses were ripened under different conditions of pH, fat content and temperature. The release of enzymes from liposomes was significantly stimulated by increasing the fat content from 0 to 20% and the pH from 4.9 to 5.5. Ripening temperature (6 degrees C or 13 degrees C) did not affect 2 months of ripening, proteolysis was 30% lower in liposome-than in free enzyme-treated cheeses, indicating a possible inhibition of released enzymes.

Calcium-Binding Proteins↗

PubMed1994

Food bioconversions and metabolite production using immobilized cell technology.

This review explores recent advances in the use of immobilized cells for the production of metabolites used in the food industry, such as enzymes, amino acids, organic acids, alcohols, aroma compounds, polysaccharides, and pigments. Some food bioconversions such as fermentation of soy sauce and various hydrolysis are also considered. Special emphasis was placed on existing or potential industrial processes. This article also reports the effects of the reactor (configuration and working conditions), the immobilized cell physiological status (growing, nongrowing, or permeabilized), and of the carrier type, configuration, and size on the performance of immobilized cell systems. Compared with free cell fermentation, the main advantage of using immobilized cells is an increase in productivity, particularly in the case of continuous fermentation. For monoenzymatic reactions, nongrowing immobilized cells are often reported to exhibit a higher stability than free or immobilized enzymes.

Fermentation↗

PubMed1992

Large-scale blood substitute production using a microfluidizer.

Microfluidization has been tested as a way to disperse phospholipids in aqueous hemoglobin solutions. Spherical and stable liposomes of 2 to 3 microns were obtained. Lipid incorporation (up to 85%) and hemoglobin encapsulation (up to 15%) in liposomes have been improved with respect to previous investigations. However, results show that a more efficient dispersion system using lower concentrations of lipid is required to obtain a high liposome hemoglobin concentration (limited actually to 150 g/l) and an economically and biologically suitable process for artificial blood production at large scale.

Blood Substitutes↗

PubMedDate not supplied

Recent advances in the large-scale production of lipid vesicles for use in food products: microfluidization.

The development of a method for the continuous mass production of liposomes is vital for the industrial use of liposomes in food products. The method should be mild enough to prevent denaturation of the encapsulated material, and the materials used for the preparation of the liposomes should be safe and edible. Among the methods available, microfluidization seems to be the most promising. Microfluidization consists of processing emulsions under high pressure through an apparatus called a Microfluidizer. This apparatus also allows the production of another type of lipid vesicle: milkfat-coated microcapsules composed of milkfat and emulsifiers. The main advantages of microfluidization include the continuous production of large quantities of lipid vesicles without dissolving the phospholipids in organic solvents. These vesicles could be used in various food products for a variety of objectives. The addition of encapsulated material in liposomes or in milkfat-coated microcapsules to cheese milk resulted in a retention of 80-90% of the vesicles in the cheese, compared to only 2-4% if the material was added directly to the milk in the unencapsulated form. Liposomes and milkfat-coated microcapsules could be used as enzyme carriers to accelerate cheese ripening, or as carriers for flavouring systems to improve the organoleptic properties of low-fat cheeses or to impart distinctive flavours to new speciality cheeses. These microcapsules could also be used in food products to avoid undesirable side-reactions during food processing, or to supplement food products with nutritious additives.

Animals↗

PubMedDate not supplied

Characterization of enzyme immobilization in liposomes prepared from proliposomes.

This study investigated the influence of ionic strength, liposome net charge and enzyme concentration on the immobilization of chymotrypsin in liposomes obtained from proliposomes. Depending on ionic strength and chymotrypsin concentration, immobilization efficiencies (IE) as high as 96 and 68% were obtained for liposomes prepared with Pro-lipo 3045 S and Pro-lipo 3080 S respectively. Increasing ionic strength and enzyme concentration resulted in a decrease in IE for both types of liposomes, and this was more pronounced for ionic strength. Relatively high amounts of chymotrypsin were found to be immobilized on the surface of the liposomes. Hydrophobic interactions between chymotrypsin and the hydrophobic tails of the phospholipids during liposome formation were probably responsible for this phenomenon.

Chymotrypsin↗