Application of ruthenium red and colloidal gold-labeled lectin for the visualization of bacterial exopolysaccharides in Cheddar cheese matrix using transmission electron microscopy

Dabour, Nassra; LaPointe, Gisèle; Benhamou, Nicole; Fliss, Ismaı̈l; Kheadr, Ehab

doi:10.1016/j.idairyj.2004.10.004

Cited by 15 publications

(16 citation statements)

References 48 publications

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“…The formation of an EPS network by the JRF1 strain in fermented milk was recently observed by Hassan, Frank, and El Soda (2003) using cryo-scanning electron microscopy. We have also observed the same network structure formed by the same strain in reduced-fat Cheddar cheese matrix using transmission electron microscopy (Dabour, LaPointe, Benhamou, Fliss, & Kheadr, 2004).…”

Section: Cheese Compositionsupporting

confidence: 63%

Impact of ropy and capsular exopolysaccharide-producing strains of Lactococcus lactis subsp. cremoris on reduced-fat Cheddar cheese production and whey composition

Dabour

Kheadr

Fliss

et al. 2005

International Dairy Journal

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Section: Cheese Compositionsupporting

confidence: 63%

Impact of ropy and capsular exopolysaccharide-producing strains of Lactococcus lactis subsp. cremoris on reduced-fat Cheddar cheese production and whey composition

Dabour

Kheadr

Fliss

et al. 2005

International Dairy Journal

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“…For microstructural studies, samples (0.8 to 1.0 mm 3 ) cut from cheese blocks were immersed overnight at 4°C in a fixative mixture containing 0.05% (vol/vol) glutaraldehyde (Marivac Ltd., Halifax, NS, Canada), 2.5% (wt/ vol) paraformaldehyde, 2 mM calcium chloride, 1% (wt/ vol) sucrose, and 0.15% (wt/vol) ruthenium red (Sigma) in 0.1 M sodium cacodylate buffer, pH 7.2 (Dabour et al, 2005b). After thorough washing in cacodylate buffer containing 0.15% ruthenium red, cheese samples were postfixed overnight with 1% (wt/vol) osmium tetroxide (JBS-CHEM, Dorval, PQ, Canada) in the same buffer at 4°C, dehydrated in a graded ethanol series, and embedded in Epon 812 (Polyscience Inc., Warrington, PA).…”

Section: Analysis Of Cheese Microstructure By Transmission Electron Mmentioning

confidence: 99%

“…thermophilus TAO61 (Petersen et al, 2000). Using transmission electron microscopy, we previously demonstrated that EPS released by the JRF-1 ropy strain into the Cheddar cheese matrix was arranged to form a network-like structure in the residual whey pockets at the fat/casein interface, and this structure may help retain more water molecules than capsule-attached EPS (Dabour et al, 2005b).…”

Section: Chemical Composition and Yieldmentioning

confidence: 99%

Improvement of Texture and Structure of Reduced-Fat Cheddar Cheese by Exopolysaccharide-Producing Lactococci

Dabour

Kheadr

Benhamou³

et al. 2006

Journal of Dairy Science

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The objective of this study was to evaluate the effect of capsular and ropy exopolysaccharide (EPS)-producing strains of Lactococcus lactis ssp. cremoris on textural and microstructural attributes during ripening of 50%-reduced-fat Cheddar cheese. Cheeses were manufactured with added capsule- or ropy-forming strains individually or in combination. For comparison, reduced-fat cheese with or without lecithin added at 0.2% (wt/vol) to cheese milk and full-fat cheeses were made using EPS-nonproducing starter, and all cheeses were ripened at 7 degrees C for 6 mo. Exopolysaccharide-producing strains increased cheese moisture retention by 3.6 to 4.8% and cheese yield by 0.28 to 1.19 kg/100 kg compared with control cheese, whereas lecithin-containing cheese retained 1.4% higher moisture and had 0.37 kg/100 kg higher yield over the control cheese. Texture profile analyses for 0-d-old cheeses revealed that cheeses with EPS-producing strains had less firm, springy, and cohesive texture but were more brittle than control cheeses. However, these effects became less pronounced after 6 mo of ripening. Using transmission electron microscopy, fresh and aged cheeses with added EPS-producing strains showed a less compact protein matrix through which larger whey pockets were dispersed compared with control cheese. The numerical analysis of transmission electron microscopy images showed that the area in the cheese matrix occupied by protein was smaller in cheeses with added EPS-producing strains than in control cheese. On the other hand, lecithin had little impact on both cheese texture and microstructure; after 6 mo, cheese containing lecithin showed a texture profile very close to that of control reduced-fat cheese. The protein-occupied area in the cheese matrix did not appear to be significantly affected by lecithin addition. Exopolysaccharide-producing strains could contribute to the modification of cheese texture and microstructure and thus modify the functional properties of reduced-fat Cheddar cheese.

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“…On the contrary, glucose (Glc) and/or mannose appeared to be the major constituents of the matrix. In general, a glucose to galactose molar ratio of 2:1 is found in the repeating units of EPS produced by LAB, with other sugars like rhamnose (Rha) also being possibly involved in the structure (Dabour et al, 2005;Kleerebezem et al, 1999). A quite similar ratio has recently been determined for the novel cell wall PS pellicle on the surface of L. lactis IL 1403 (Chapot-Chartier et al, 2010).…”

Section: Flow Field Structurementioning

confidence: 62%

A unique phenotypic modification of Lactococcus lactis cultivated in a couette bioreactor

Douaire¹,

Mercade²,

Morchain³

et al. 2010

Biotech & Bioengineering

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Batch cultures of Lactococcus lactis NCDO 2118 and IL 1403 were performed in a Couette bioreactor operated in the modulated wavy vortex flow and the turbulent regimes. This study provides an overall analysis taking into account both mechanical stress and mixing in a Couette bioreactor. A unique phenotypic aspect has been proved to occur only in the modulated wavy vortex flow regime for the two studied strains, namely that the cells become entrapped in a filamentous form. No change in the metabolic behavior of the cells has been observed. The polymeric matrix has been microscopically observed through FISH and fluorescent lectin binding, showing cells entrapped in a glycoconjugate matrix. All hypotheses regarding insufficient mixing as a cause of this phenotype have been discarded, leading to the conclusion that this particular phenotypic feature is essentially due a combined effect of mechanical stress and flow structure. Particle size measurement during the fermentation course indicates that formation of filamentous form results from a continuous aggregation started in the early stages of the cultivation. According to our results a minimum shear is required to induce the ability for cells to aggregate. Then, it appears that both flow structure and mechanical stress (shear) are responsible for the appearance of such a filamentous form. As far as the authors know, this is the first experimental evidence of a bio polymerization induced by the flow structure.

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Application of ruthenium red and colloidal gold-labeled lectin for the visualization of bacterial exopolysaccharides in Cheddar cheese matrix using transmission electron microscopy

Cited by 15 publications

References 48 publications

Impact of ropy and capsular exopolysaccharide-producing strains of Lactococcus lactis subsp. cremoris on reduced-fat Cheddar cheese production and whey composition

Impact of ropy and capsular exopolysaccharide-producing strains of Lactococcus lactis subsp. cremoris on reduced-fat Cheddar cheese production and whey composition

Improvement of Texture and Structure of Reduced-Fat Cheddar Cheese by Exopolysaccharide-Producing Lactococci

A unique phenotypic modification of Lactococcus lactis cultivated in a couette bioreactor

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