Microbial Exopolysaccharides in Foods: New Aspects of the Interplay between Structure and Function, and Implications on Product Quality

A special issue of Foods (ISSN 2304-8158). This special issue belongs to the section "Food Physics and (Bio)Chemistry".

Deadline for manuscript submissions: closed (31 December 2019) | Viewed by 13377

Special Issue Editors

Chair of Food Engineering, Institute of Food Technology and Bioprocess Engineering, Technische Universität Dresden, Dresden, Germany
Interests: sustainability; food processing; by-products; rheology; physical properties
Special Issues, Collections and Topics in MDPI journals
Institute of Natural Materials Technology, Technische Universität Dresden, 01062 Dresden, Germany
Interests: fermented milks; cheese; starter cultures; rheology; milk proteins; cross-linking proteins
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

A significant amount of food is produced by using hydrocolloids to modify properties such as water binding capacity or viscosity. These hydrocolloids are either of plant or animal origin, or are the result of fermentation processes. The respective microbial metabolites are extracellular polysaccharides (EPS) that are synthesized during fermentation by a wide range of microorganisms. After synthesis, the polymers are either associated as cell envelope, or non-associated and released as slime into the environment. Several EPS have already found their way into industrial use after isolation and purification, including xanthan, curdlan, gellan, or dextran.

Many starter culture bacteria produce EPS in situ which also affect the microstructure of the respective products, and properties that are linked to microstructure such as rheology or water binding capacity. The aim of this Special Issue is to collect contributions deriving from complementary expertise concerning the interplay between the specific structural features of EPS and the related impact on foods. In addition, fermentation and production steps to control effects, and trends or current strategies to utilize microbial exopolysaccharides shall be addressed. Contributions dealing with specific effects of added microbial exopolysaccharides on food systems are also welcome.

Prof. Dr. Harald Rohm
Dr. Doris Jaros
Guest Editors

Manuscript Submission Information

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Keywords

  • food fermentation
  • exopolysaccharides
  • molecular structure
  • food microstructure
  • technofunctional properties

Published Papers (3 papers)

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Research

10 pages, 1916 KiB  
Article
Size-Dependent Variability in Flow and Viscoelastic Behavior of Levan Produced by Gluconobacter albidus TMW 2.1191
Foods 2020, 9(2), 192; https://doi.org/10.3390/foods9020192 - 14 Feb 2020
Cited by 14 | Viewed by 3184
Abstract
Levan is a fructan-type exopolysaccharide which is produced by many microbes from sucrose via extracellular levansucrases. The hydrocolloid properties of levan depend on its molecular weight, while it is unknown why and to what extent levan is functionally diverse depending on its size. [...] Read more.
Levan is a fructan-type exopolysaccharide which is produced by many microbes from sucrose via extracellular levansucrases. The hydrocolloid properties of levan depend on its molecular weight, while it is unknown why and to what extent levan is functionally diverse depending on its size. The aim of our study was to gain deeper insight into the size-dependent functional variability of levan. For this purpose, levans of different sizes were produced using the water kefir isolate Gluconobacter albidus TMW 2.1191 and subsequently rheologically characterized. Three levan types could be identified, which are similarly branched, but differ significantly in their molecular size and rheological properties. The smallest levan (<107 Da), produced without adjustment of the pH, exhibited Newton-like flow behavior up to a specific concentration of 25% (w/v). By contrast, larger levans (>108 Da) produced at pH ≥ 4.5 were shear-thinning, and the levan produced at pH 5.0 showed a gel-like behavior at 5% (w/v). A third (intermediate) levan variant was obtained through production in buffers at pH 4.0 and exhibited the properties of a viscoelastic fluid up to concentrations of 15% (w/v). Our study reveals that the rheological properties of levan are determined by its size and polydispersity, rather than by the amount of levan used or the structural composition. Full article
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11 pages, 922 KiB  
Article
Clustering of Streptococcus thermophilus Strains to Establish a Relation between Exopolysaccharide Characteristics and Gel Properties of Acidified Milk
Foods 2019, 8(5), 146; https://doi.org/10.3390/foods8050146 - 30 Apr 2019
Cited by 25 | Viewed by 3852
Abstract
In situ produced extracellular polysaccharides (EPS) from lactic acid bacteria are generally known to affect the texture of fermented dairy products; however, the interplay between EPS and product properties is still poorly understood. The aim of this study was to establish a relationship [...] Read more.
In situ produced extracellular polysaccharides (EPS) from lactic acid bacteria are generally known to affect the texture of fermented dairy products; however, the interplay between EPS and product properties is still poorly understood. The aim of this study was to establish a relationship between concentration and properties of EPS, and gel formation of milk analysed by noninvasive Multispeckle Diffusing Wave Spectroscopy. Twenty Streptococcus thermophilus strains were classified with respect to EPS concentration (8–126 mg GE/kg) and ropiness (thread length: 15–80 mm). Five groups identified by cluster analysis demonstrate the high strain-to-strain variability even within one species of lactic acid bacteria. Results from acidification and gelation experiments averaged per cluster indicate that fermentation time and gel stiffness is higher for strains that produce ropy EPS. A further increase in gel stiffness was detected for strains that also produced cell-bound EPS, which underlines the importance of both ropy and cell-bound EPS for improving acid gel properties. The results may be helpful for a proper selection of EPS-producing starter cultures. Full article
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12 pages, 5643 KiB  
Article
Characterization, Antimicrobial Properties and Coatings Application of Gellan Gum Oxidized with Hydrogen Peroxide
Foods 2019, 8(1), 31; https://doi.org/10.3390/foods8010031 - 17 Jan 2019
Cited by 33 | Viewed by 5816
Abstract
The effect of hydrogen peroxide (H2O2) oxidation on the physicochemical, gelation and antimicrobial properties of gellan gum was studied. The oxidized gellan gum (OGG) was characterized by measuring the carboxyl/carbonyl group contents, Fourier transform infrared spectroscopy (FTIR) and proton [...] Read more.
The effect of hydrogen peroxide (H2O2) oxidation on the physicochemical, gelation and antimicrobial properties of gellan gum was studied. The oxidized gellan gum (OGG) was characterized by measuring the carboxyl/carbonyl group contents, Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H-NMR) spectroscopy. The H2O2 oxidation resulted in a large increase in the carboxyl groups in gellan gum. The OGG lost gelation ability by oxidation even in the presence of metal ions. The antimicrobial activities of the OGG against Gram-positive bacteria (Staphylococcus aureus), Gram-negative bacteria (Escherichia coli), and fungal (Aspergillus niger) were tested. The OGG could inhibit the growth of both bacteria and fungal, and the activity was improved with an increase in the oxidation level. Finally, the application of the OGG as an active coatings material to extend the storage of apples was tested. Full article
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