Microstructure and Rheology of Yogurt Made with Cultures Differing Only in Their Ability to Produce Exopolysaccharides

Hassan, A.N.; Ipsen, Richard; Janzen, Thomas; Qvist, K.B.

doi:10.3168/jds.s0022-0302(03)73748-5

Cited by 217 publications

(196 citation statements)

References 16 publications

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“…The size of the area enclosed between the upward and downward curves from hysteresis loop experiments can be considered as being proportional to structural breakdown (Folkenberg et al 2006;Hassan et al 2003). Figure 3 exemplary shows the response curves of the three stirred yoghurt products made with starter A which enclosed hysteresis areas of nearly the same size.…”

Section: Shear Stability Of Stirred Milk Gelsmentioning

confidence: 99%

Fermented milk products: effects of lactose hydrolysis and fermentation conditions on the rheological properties

Schmidt

Mende

Jaros

et al. 2015

Dairy Sci. & Technol.

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Lactose-free dairy products become increasingly important for lactoseintolerant consumers, but there are only few studies concerning the rheological properties of fermented dairy products from lactose-hydrolysed milk. Hydrolysation was performed with commercial β-galactosidase either before or during fermentation (cohydrolysis). In each trial, fermentation of the base milk was carried out simultaneously using the same starter cultures for (a) untreated milk (reference) (b) hydrolysed milk as substrate and (c) by performing lactose hydrolysis and fermentation simultaneously (co-hydrolysis). In total, five thermophilic starter cultures and two products (yoghurt and Greek-style yoghurt) were investigated. Results show that the influence of hydrolysis of lactose on the properties of the fermented dairy products strongly depends on starter culture and substrate. For starters C and D, apparent viscosity (extracted from flow curves at a shear rate of 75 s −1 ) of fermented milks was only marginally affected by lactose hydrolysis, ranging between approx. 0.34-0.31 and 0.37-0.31 Pa.s, respectively. Hydrolysed products from starters A and E exhibited significant lower apparent viscosity (0.16 and 0.24 Pa.s) compared with their respective references (0.29 and 0.35 Pa.s). Fermentation of both substrates (regular yoghurt, Greek-style yoghurt) with starter B resulted in a decrease of yield stress and apparent viscosity because of lactose hydrolysis only for Greek-style yoghurt. Furthermore, a trend towards higher EPS synthesis was found when using hydrolysed milk. The results clearly show that products made from lactose-hydrolysed milk with similar rheological properties as the reference product can be obtained but that there is a lack of information concerning the complex interactions between starter culture and milk substrate.

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Section: Shear Stability Of Stirred Milk Gelsmentioning

confidence: 99%

Fermented milk products: effects of lactose hydrolysis and fermentation conditions on the rheological properties

Schmidt

Mende

Jaros

et al. 2015

Dairy Sci. & Technol.

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“…These results indicate that the increased EPS production in TMB 6013 reduces the elasticity of the fermented milk but does not affect the viscosity of the product. The result might have been different if EPSs with other structures had been studied; however, lower values of the elastic modulus have been reported for yogurts made with EPS-producing strains than with yogurts made with non-EPS-producing strains (6).…”

Section: Fig 1 Schematic Representation Of Lactose Catabolism In Smentioning

confidence: 78%

“…Dairy strains of Streptococcus thermophilus that produce exopolysaccharides (EPSs) have attracted interest recently, since the EPSs act as in situ-produced natural biothickeners that improve the texture of fermented foods (5,6,10). Thus, a high EPS production in situ during the fermentation of milk to yogurt could be an advantage for the food industry.…”

mentioning

confidence: 99%

Metabolically Improved Exopolysaccharide Production by Streptococcus thermophilus and Its Influence on the Rheological Properties of Fermented Milk

Svensson

Waak²,

Svensson³

et al. 2005

Appl Environ Microbiol

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Altered levels of enzymes in the central carbon metabolism in Streptococcus thermophilus increased the exopolysaccharide (EPS) production 3.3 times over that of the parent strain. The influence of enhanced EPS production on the rheological properties of fermented milk is described for engineered strains of S. thermophilus which produce different levels of EPSs.Dairy strains of Streptococcus thermophilus that produce exopolysaccharides (EPSs) have attracted interest recently, since the EPSs act as in situ-produced natural biothickeners that improve the texture of fermented foods (5, 6, 10). Thus, a high EPS production in situ during the fermentation of milk to yogurt could be an advantage for the food industry. However, EPSs from S. thermophilus strains are produced at relatively low levels, i.e., 50 to 400 mg per liter (3).We have previously described the selection of a galactosefermenting (Gal ϩ ) mutant (TMB 6010) from the galactosenegative (Gal Ϫ ) strain S. thermophilus LY03 with enhanced activities of the Leloir enzymes ( Fig. 1), which generates an EPS yield 1.4 times higher than that of the parent strain (7). However, a drawback was the accumulation of glucose-1-phosphate (G1P), which was observed in this mutant. We have also reported on a successful metabolic engineering strategy to enhance EPS production in a Gal Ϫ strain of S. thermophilus by a factor of 2 by increasing the activities of ␣-phosphoglucomutase (PGM) and UDP-glucose pyrophosphorylase (GalU) (7), which are part of the central carbon metabolism (Fig. 1). The aims of this study were (i) to improve EPS production by S. thermophilus LY03 even further than in our previously constructed mutants (7) and (ii) to investigate the influence of EPSs on the rheological properties of fermented milk.To investigate the combined effect of increased activities of PGM, GalU, and the Leloir enzymes, S. thermophilus TMB 6010 was transformed with pFL46 (7) by electroporation as described previously (9), yielding TMB 6013. The strains S. thermophilus LY03 (commercial yogurt strain from Vrije University, Brussels, Belgium), TMB 6010, and TMB 6013 were cultivated in MST medium (8) at 42°C and a pH of 6.2 (Table 1), according to Levander et al. (7). In the late exponential phase, the EPS production by TMB 6013 was 3.3 times higher than that by LY03 and at least 1.5 times higher than that by our previously metabolically engineered strains (7). All these strains produced EPSs with identical structures (Andrew Laws, personal communication). To gain a better understanding of how the metabolism was affected by the altered activities of PGM, GalU, and the Leloir enzymes, the intracellular concentrations of G1P, glucose-6-phosphate (G6P), and UDPglucose (UDPglc) were measured in the late exponential phase (Table 2) as previously described (7). Higher levels of G1P and G6P were found in TMB 6010 than in LY03, in agreement with our previous observations (7). This result suggests an increased flux through the Leloir pathway in TMB 6010 compared with LY03. Interestingly, a hi...

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“…EPS prevent syneresis and improve product stability firstly by increasing the viscosity and elasticity of the final product, and secondly by binding hydration water. Hydrocolloids are mainly used to improve mouth-feel, texture, visual and taste perception, storage stability, mechanical protection and prevention of syneresis in the final food products (Broadbent et al 2003;Hassan et al 2003;Sikora et al 2003). CMC or cellulose gum is presently used in food science as a viscosity modifier or thickener, and to stabilize emulsions in various products including ice-cream.…”

Section: Molecular Weight and Polydispersity Index (Pdi) Of Eps By Himentioning

confidence: 99%

Molecular characterization of an exopolysaccharide from a probiotic Lactobacillus plantarum MTCC 9510 and its efficacy to improve the texture of starchy food

Ismail

Nampoothiri

2013

J Food Sci Technol

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The weight average molecular weight (Mw), number average molecular weight (Mn) and size average molecular weight (Mz) of an exopolysaccharide from probiotic Lactobacillus plantarum MTCC 9510 was found to be 2.68×10 5 Da, 2.55×10 5 Da and 2.83×10 5 Da, respectively by Gel permeation Chromatography employing the third order polynomial model. The polydispersity index (Mw/Mn) of the polysaccharide was obtained as 1.05. The exopolysaccharide and the starch-exopolysaccharide hydrocolloid exhibited a non-Newtonian and pseudo-plastic behaviour with improvement in the texture of starch containing food by preventing syneresis.

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Microstructure and Rheology of Yogurt Made with Cultures Differing Only in Their Ability to Produce Exopolysaccharides

Cited by 217 publications

References 16 publications

Fermented milk products: effects of lactose hydrolysis and fermentation conditions on the rheological properties

Fermented milk products: effects of lactose hydrolysis and fermentation conditions on the rheological properties

Metabolically Improved Exopolysaccharide Production by Streptococcus thermophilus and Its Influence on the Rheological Properties of Fermented Milk

Molecular characterization of an exopolysaccharide from a probiotic Lactobacillus plantarum MTCC 9510 and its efficacy to improve the texture of starchy food

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