Investigating the impact of exopolysaccharides on yogurt network mechanics and syneresis through quantitative microstructural analysis

Exopolysaccharides produced by lactic acid bacteria are widely used to improve the sensory properties of yogurt. The relation between the physical properties of the microbial exopolysaccharides and the structural and rheological properties of the yogurt are incompletely understood to date. To address this knowledge gap, we studied how two distinct exopolysaccharides influence the microstructure, rheological properties, and syneresis of yogurt. The effect of a negatively charged, capsular exopolysaccharide produced by Streptococcus thermophilus and a neutral, non-capsular exopolysaccharide produced by Lactococcus lactis were investigated. Using quantitative microstructural analysis, we examined yogurt samples prepared with either the capsular or the non-capsular exopolysaccharide, and with mixtures of the two. Confocal laser scanning microscopy and stimulated emission depletion microscopy were employed to visualize the microstructures, revealing differences in pore size distribution, protein domain size, and casein interconnectivity that were not apparent through visual inspection alone. Additionally, variations in rheological properties were observed among the different yogurt types. In the yogurt fermented with both bacterial strains, we observed a combined impact of the two exopolysaccharide types on relevant microstructural and rheological properties. The negatively charged capsular exopolysaccharide enhanced casein interconnectivity and gel stiffness, while the neutral non-capsular exopolysaccharide led to thicker protein domains, an abundance of small pores, and a lower loss tangent. These factors collectively hindered syneresis, resulting in improved structural integrity. Our study not only provides valuable insights into the influence of different exopolysaccharides on yogurt properties, but also presents the first demonstration and quantification of the effect of multiple types of exopolysaccharides on casein interconnectivity. These findings offer guidance for the production of yogurts with customized microstructure, rheological properties, and resistance to syneresis.<br/

A nonsmooth frictional contact formulation for multibody system dynamics

We present a new node-to-face frictional contact element for the simulation of the nonsmooth dynamics of systems composed of rigid and flexible bodies connected by kinematic joints. The equations of motion are integrated using a nonsmooth generalized-α time integration scheme and the frictional contact problem is formulated using a mixed approach, based on an augmented Lagrangian technique and a Coulomb friction law. The numerical results are independent of any user-defined penalty parameter for the normal or tangential component of the forces and, the bilateral and the unilateral constraints are exactly fulfilled both at position and velocity levels. Finally, the robustness and the performance of the proposed algorithm are demonstrated by solving several numerical examples of nonsmooth mechanical systems involving frictional contact.Fil: Galvez, Javier. Université de Liège; BélgicaFil: Cavalieri, Federico José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones en Métodos Computacionales. Universidad Nacional del Litoral. Centro de Investigaciones en Métodos Computacionales; ArgentinaFil: Cosimo, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones en Métodos Computacionales. Universidad Nacional del Litoral. Centro de Investigaciones en Métodos Computacionales; Argentina. Université de Liège; BélgicaFil: Brüls, Olivier. Université de Liège; BélgicaFil: Cardona, Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones en Métodos Computacionales. Universidad Nacional del Litoral. Centro de Investigaciones en Métodos Computacionales; Argentin

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

multiphysics modelling of mechatronic multibody systems

Modeling mechatronic multibody systems requires the same type of methodology as for designing and prototyping mechatronic devices: a unified and integrated engineering approach. Various formulations are currently proposed to deal with multiphysics modeling, e.g. graph theories, equational approaches, cosimulation techniques. Recent works have pointed out their relative advantages and drawbacks, depending on the application to deal with: model size, model complexity, degree of coupling, frequency range, etc. This paper is the result of a close collaboration between three Belgian laboratories, and aims at showing that for"non-academic" mechatronic applications (i.e. issuing from real industrial issues), multibody dynamics formulations can be generalized to mechatronic applications, for the model generation as well as for the numerical analysis phases. Model portability being also an important aspect of the work, they must be easily interfaced with control design and optimization programs. A global"demonstrator", based on an industrial case, is discussed: multiphysics modeling, control design and mathematical optimization are carried out to illustrate the consistency and the efficiency of the proposed approaches. © (2006) by the Katholieke Universiteit Leuven Department of Mechanical Engineering All rights reserved.status: publishe

Spatial distribution of αs1-caseins and β-caseins in milk gels acidified with glucono-δ-lactone

Acid-induced destabilization of casein micelles leads to coagulation of milk which plays an important role in the formation of yogurt. The resulting protein network is formed by aggregation and reconfiguration of casein micelles, including the release of a portion of caseins from these micelles. It is so far unknown how individual αs1-and β-caseins are organized within this complex network, and how their distribution depends on yogurt composition and processing. Here, we imaged the spatial distribution of caseins using stimulated emission depletion (STED) microscopy and single-molecule localization microscopy (SMLM). We used fluorescently tagged antibodies against αs1-and β-caseins to localize them inside glucono-δ-lactone (GDL)-acidified milk gels. We conducted quantitative skeleton analysis of STED images and showed that αs1-and β-caseins contribute with different levels of connectivity to the acid induced milk network

Topology and generalized shape optimization: Why stress constraints are so important?

The paper continues along the work initiated by the authors in taking into account stress constraints in topology optimization of continuum structures. Revisiting some of their last developments in this field, the authors point out the importance of considering stress constraints as soon as the preliminary design phase, that is, to include stress constraints in the topology optimization problem in order to get the most appropriate structural layout. Numerical applications that can be solved using these new developments make possible to exhibit interesting results related to the specific nature of strength based structural layout for maximum strength compared to maximum stiffness. This particular character of stress design is clearly demonstrated in two kinds of situations: once several load cases are considered and when unequal stress limits in tension and compression are involved

Super resolution microscopy imaging of pH induced changes in the microstructure of casein micelles

Acidification of milk destabilizes casein micelles (CMs) and results in network formation. This process is fundamental during the manufacturing of dairy gels such as cheese and yoghurts. Understanding the structural alterations of CMs during this process aids to predict the physicochemical and sensory properties of dairy gels. Herein we utilize direct Stochastic Optical Reconstruction Microscopy (dSTORM) to visualize individual hydrated CMs and characterize pH-dependent changes in CM size distributions. CMs were immobilized, fixed, labelled with caseins-specific primary antibodies, and imaged by dSTORM using Alexa Fluor 647 conjugated secondary antibodies. While antibodies specific to κ- and β-casein were used to stain CMs, only β-casein antibodies enabled reproducible imaging of micelles across the entire chosen pH window. Furthermore, CM's structural evolution was studied at acidic pH values representing the conditions during acid milk gel formation and at three elevated pH values. dSTORM imaging of casein aggregates at pH 4.5, below the isoelectric point of caseins, showed that β-casein distribution throughout the protein network and resolved nano-sized pores within the structure. Moreover, automated and quantitative image analysis revealed that the average size of CMs increased upon alkalization to pH 7.5 and 8.3, whilst narrow size distributions were found upon acidification to pH 5.5