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  • 1
    In: Journal of Animal Science, 2016, Vol. 94(suppl5), pp.268-269
    Description: The objective is to present recent developments and insights on novel ways to operate dairy membrane operations at higher levels of efficiency and predictability. Boundary layer phenomena at the surfaces of membranes, in particular, adsorption, retention, and deposit formation are still not fully understood. Hence, adverse effects reducing flux and unpredictable permeation of components cannot reliably be prevented. Deposits reduce flux and in many cases dominate the system's retention characteristics. Deposit formation is dependent on the position along the membrane surface, which is a result of the pressure drop in crossflow situations. These aspects will be discussed with particular regard to whey concentration and milk protein fractionation by means of microfiltration as possibly the most challenging example. The related phenomena were investigated experimentally and theoretically in terms of assessing deposit properties (casein micelle multi-layers, in this case), such as thickness and porosity, as a function of position along the membrane. For this purpose, special membrane prototypes were constructed enabling the measurement of flux and convective transport of material through the membrane pores in four sections along a tubular, industrially sized ceramic membrane. Similarly, the effect of membrane length has been studied for spiral wound modules (SWM), which are the dominating membrane type in dairy installations. Deposit amounts and structures were assessed by means of chemical analysis and synchrotron-based X-ray analysis, using the novel GISAXS technique (grazing incidence small angle X-ray scattering). This way, casein micelle deformation was found to occur as a result of elongational flow of the filtrate stream toward the membrane surface. Further, a method for improved whey ultrafiltration performance as a result of a pre-microfiltration step is presented. The removal of protein aggregates in whey increases flux levels considerably, and a reduction of the microbial load is achieved. Novel cascade-like combinations of UF and RO/NF are discussed as a means to achieve high levels of concentration for whey and, for comparison, milk. The UF step removes the protein, such that the RO step has only to cope with osmotic pressure and remains unaffected by deposit formation. Thus, higher concentration levels and an increased flux can be achieved as well as concentration in shorter times at reduced energy levels. UF was assessed in the form of various processing concepts, namely conventional polymeric spiral-wound and ceramic crossflow systems as well as dynamic rotating ceramic membranes, which are able to produce and to cope with high protein concentration levels.
    Keywords: Membrane Technology ; Microfiltration ; Milk Protein Fractionation ; Milk Protein Concentration
    ISSN: 0021-8812
    E-ISSN: 1525-3163
    Source: Oxford University Press
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  • 2
    Language: English
    In: Journal of Membrane Science, Sept 1, 2015, Vol.489, p.20(8)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.memsci.2015.04.002 Byline: Tim Steinhauer, Melanie Marx, Kerstin Bogendorfer, Ulrich Kulozik Abstract: For the concentration of whey proteins from whey by ultrafiltration (UF) or fractionation by microfiltration (MF), mass transfer through the membrane is limited by deposit formation which is variable and not well understood, yet. There is little knowledge on the predominant molecular mechanism responsible for membrane fouling during whey micro- and ultrafiltration. Some works indicate that whey protein aggregates induce or enhance membrane fouling. The impact of whey protein aggregates as well as the interaction of native whey proteins and whey protein aggregates during membrane fouling was studied in both dead-end lab scale and cross-flow pilot scale. By means of targeted heat-treatment, a defined amount of protein aggregates was formed in [beta]-Lactoglobulin ([beta]-Lg) model suspensions as well as in sweet whey. [beta]-Lg aggregates were found to accelerate membrane fouling during MF and UF due to covalent thiol/disulfide reactions. For sweet whey cross-flow filtration, membrane fouling was accelerated by whey protein aggregates up to a certain degree of whey protein denaturation. Above a critical value of 30% protein denaturation, flux increased again. This effect is explained by an improved erosion of larger whey protein aggregates as well as a reduced reactivity of heat-aged whey protein aggregates. Author Affiliation: (a) Chair for Food Process Engineering and Dairy Technology, Technische Universitat Munchen, Germany (b) ZIEL Research Center for Nutrition and Food Sciences, Technische Universitat Munchen, Germany Article History: Received 19 January 2015; Revised 2 April 2015; Accepted 3 April 2015
    Keywords: Protein Denaturation – Environmental Aspects ; Protein Denaturation – Analysis ; Environmental Quality – Environmental Aspects ; Environmental Quality – Analysis ; Milk Proteins – Environmental Aspects ; Milk Proteins – Analysis
    ISSN: 0376-7388
    Source: Cengage Learning, Inc.
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  • 3
    Language: English
    In: Journal of Membrane Science, Oct 15, 2015, Vol.492, p.364(7)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.memsci.2015.05.053 Byline: Tim Steinhauer, Sabrina Hanely, Kerstin Bogendorfer, Ulrich Kulozik Abstract: Ultra- and microfiltrations are industrially applied for the concentration and fractionation of whey proteins. Thereby, either high (~50[degrees]C) or low (〈10[degrees]C) processing temperatures can be selected to avoid microbial spoilage of the product. Filtration performance at the two temperature ranges was found to be significantly different. For this reason, this study focusses on the impact of temperature on membrane fouling during both ultra- and microfiltration of whey and whey protein suspensions. We found significantly different deposit layer structures at the two pore sizes investigated. During microfiltration (full whey protein permeation), membrane fouling due to adsorption processes was facilitated at temperatures [less than or equal to]10[degrees]C and 〉35[degrees]C. For filtrations with fully retentive ultrafiltration membranes, an increase in processing temperature resulted in a decrease of specific fouling resistance, while deposit layer solid height increased. In cross-flow mode, fouling resistance was independent of temperature during acid whey microfiltration. A temperature increase during filtration of sweet whey resulted in a sharp increase of membrane fouling for temperatures above 40[degrees]C. When increasing temperature, the stronger fouling reaction in neutral pH-range could be attributed to both, the acceleration of thiol/disulfide reaction speed and calcium based protein cross-linking. Author Affiliation: (a) Chair for Food Process Engineering and Dairy Technology, Technische Universitat Munchen, Weihenstephaner Berg 1, Freising-Weihenstephan, Germany (b) ZIEL Research Center for Nutrition and Food Sciences, Technische Universitat Munchen, Weihenstephaner Berg 1, Freising-Weihenstephan, Germany Article History: Received 9 March 2015; Revised 8 May 2015; Accepted 26 May 2015
    Keywords: Adsorption ; Milk Proteins
    ISSN: 0376-7388
    Source: Cengage Learning, Inc.
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  • 4
    In: Journal of Applied Microbiology, March 2012, Vol.112(3), pp.493-501
    Description: To determine the influence of condensation as a function of the surface temperature of aseptic packaging, on the inactivation of spores [ (DSM 347), SA22, ] having different surface properties by means of vaporized HO. The packaging specimens inoculated with spores were tempered and subsequently exposed to HO‐vapour. During the exposure, surface temperature curves were measured and the spore survival was determined. Results showed that decreasing the initial surface temperature of the packaging specimens had a positive effect on the sporicidal activity of HO‐vapour, where the effect was less pronounced for less hydrophilic spores. The surfaces of spores were characterized by means of the water contact angle. For starting surface temperatures below the dew point temperature of the sterilant gas, the condensation of highly concentrated liquid HO on the packaging surface accelerates the killing of the spores, while the inferior wettability of more hydrophobic spores compared to more hydrophilic ones diminishes the effect. Regarding industrial packaging sterilization, a mixed microflora has to be inactivated. Promoting the condensation of HO improves in general the killing of different species of spores, however, at various degrees depending on the wettability of spores.
    Keywords: Aseptic Packaging ; Bacillus Spores ; H 2 O 2 ‐Vapour ; Surface Temperature
    ISSN: 1364-5072
    E-ISSN: 1365-2672
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  • 5
    Language: English
    In: Blood, 02 December 2010, Vol.116(23), pp.4737-8
    Description: The concept of biologic unity and the feasibility of “one-fits-all” treatment strategies has become outdated for most malignancies and certainly for acute lymphoblastic leukemia (ALL) of childhood. Conventionally defined malignant diseases represent a collection of molecularly distinct entities with characteristic features that define their response to treatment as well as their prognosis. Clinically significant heterogeneity of childhood ALL became apparent when disparity in treatment responses and differences in the cytogenetic makeup of leukemia cells were identified. Even today, with molecular subtyping of leukemias, these seemingly archaic features remain important components of the individual risk stratification of modern treatment protocols that allow us to successfully individualize treatment according to risk.1
    Keywords: Medicine ; Biology ; Chemistry ; Anatomy & Physiology;
    ISSN: 00064971
    E-ISSN: 1528-0020
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  • 6
    Language: English
    In: Food Chemistry, 2011, Vol.125(1), pp.121-127
    Description: Proteins acquire conformation in aqueous media due to the influence of the buffer salt composition and concentration. Such influence may have impact on the enzyme–substrate interaction and somehow steer the enzyme attack properties, leading to release of dissimilar products. Our group has sought to investigate the influence of the hydrolysis environment on the trypsinolysis of a model protein, β-lactoglobulin (β-Lg). This work was aimed at investigating the effect of different buffers and their concentrations on the trypsinolysis patterns of β-Lg. The traditional NaOH-buffered water, in comparison to Tris–HCl and potassium-phosphate buffer at 62.5 mM–1.0 M were used at pH 8.5 for the pH drop and pH 7.8 for the hydrolysis. Bovine trypsin (EC 3.4.21.4) was used at an enzyme-to-substrate ratio of 1%. The samples were analysed for mass composition, using LC-ESI-TOF/MS and MALDI-TOF/MS for monitoring time-dependence of peptide evolution. In all buffer types and concentrations, peptides (1–8), (15–40, (125–138) and (142–148) were detected, implicating ease of hydrolysis of the terminal regions of β-Lg. A peptide from (9–14), with sequence Gly-Leu-Asp-Ile-Gln-Lys, was detected at 〉0.5 M Tris–HCl only, while peptide (71–75) was unique to 〈125 mM Tris–HCl and 〉250 mM potassium-phosphate buffer. Hydrolysis under buffer produced trypsin-specific peptides, numerous chymotrypsin-like non-specific peptides but no disulphide-linked peptides. Trypsinolysis shifted to the N-terminal region of lysine under some conditions. Hydrolysis under buffer holds potential for the avoidance of some peptides with undesirable characteristics while preserving a diversity of different peptides with possible bioactive properties.
    Keywords: Protein Hydrolysis ; Trypsin ; LC-Esi-Tof/MS ; Maldi-Tof/MS ; Β-Lactoglobulin ; Buffer Salt Concentration ; Chemistry ; Diet & Clinical Nutrition ; Economics
    ISSN: 0308-8146
    E-ISSN: 1873-7072
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  • 7
    Language: English
    In: Journal of Membrane Science, Nov 1, 2015, Vol.493, p.452(8)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.memsci.2015.06.007 Byline: Tim Steinhauer, Jonas Lonfat, Ilona Hager, Ronald Gebhardt, Ulrich Kulozik Abstract: Deposit layers arising during milk microfiltration have not yet been well described with regard to their structural build-up. Besides casein micelles forming the bulk of the deposit, whey proteins are integrated into the milk protein deposit. Both the deposited protein layer and the membrane are involved in the retention of both protein fractions. Therefore, this study focusses on the impact of whey proteins on casein micelle deposit compressibility and reversibility. Compressibility and specific fouling resistance of casein micelle deposits were reduced in the presence of whey proteins. In other words, the deposit layer becomes more open or more porous due to whey protein attachment to the casein micelle surface. Furthermore, diffusive removability of the deposit layers was affected by pH and whether or not whey proteins were present. Convective removal by fluid forces was found to be almost entirely independent of pH or the presence of whey proteins. This shows that deposit layers arising during milk microfiltration consist of three phases, a diffusively removable micro-porous deposit, a gel-like convectively removable layer and internal membrane fouling. Author Affiliation: (a) Chair for Food Process Engineering and Dairy Technology, Technische Universitat Munchen, Weihenstephaner Berg 1, Freising-Weihenstephan, Germany (b) ZIEL Research Center for Nutrition and Food Sciences, Technische Universitat Munchen, Weihenstephaner Berg 1, Freising-Weihenstephan, Germany Article History: Received 9 March 2015; Revised 6 June 2015; Accepted 8 June 2015
    Keywords: Ph – Analysis ; Casein – Analysis
    ISSN: 0376-7388
    Source: Cengage Learning, Inc.
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  • 8
    Language: English
    In: Journal of Physics: Condensed Matter, 2011, Vol.23(44), p.444201 (7pp)
    Description: The objective of this study was to determine the effect of size-fractionation by centrifugation on the film structure of casein micelles. Fractionated casein micelles in solution were asymmetrically distributed with a small distribution width as measured by dynamic light scattering. Films prepared from the size-fractionated samples showed a smooth surface in optical microscopy images and a homogeneous microstructure in atomic force micrographs. The nano- and microstructure of casein films was probed by micro-beam grazing incidence small angle x-ray scattering (μGISAXS). Compared to the solution measurements, the sizes determined in the film were larger and broadly distributed. The measured GISAXS patterns clearly deviate from those simulated for a sphere and suggest a deformation of the casein micelles in the film.
    Keywords: Grazing Incidence ; Micelles ; Micrographs ; Light Scattering ; Condensed Matter ; Nanostructure ; Microstructure ; Casein ; Condensed Matter Physics (General) (So);
    ISSN: 0953-8984
    E-ISSN: 1361-648X
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  • 9
    Language: English
    In: Journal of Membrane Science, 15 October 2014, Vol.468, pp.126-132
    Description: Frontal microfiltration and grazing incidence small angle X-ray scattering (GISAXS) are used to investigate how β-lactoglobulin (β-Lg) influences the deposit structure of casein micelles (CM). Filtration experiments show that the mean specific deposit resistance decreases with increasing concentration of β-Lg in the suspensions of CM. GISAXS is used to probe surface-near structures of deposits on a nano-meter scale. A core–shell model used to compute the scattering from CM shows agreement with measurements on films prepared by spin-coating on silicon wafers. The core of CM becomes more compact as a result of preferential binding of β-Lg on the micellar surface. Scattering functions of deposits prepared by filtration on micro-sieves show power-law behavior characteristic for mass-fractal structure. This structure consists of dense packed CM with interconnected β-Lg molecules on the surface. The resulting network of CM is porous and explains the reduced mean specific deposit resistance, as well as the increased permeate flow, in the presence of β-Lg.
    Keywords: Casein Micelles ; Β-Lactoglobulin ; Deposit Layers on Membranes ; X-Ray Scattering ; Engineering
    ISSN: 0376-7388
    E-ISSN: 1873-3123
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  • 10
    Language: English
    In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, 05 March 2017, Vol.516, pp.286-295
    Description: Due to its structural versatility and remarkable surface activity, β-lactoglobulin (β-Lg) is a prominent food structuring agent in both its native state and in the form of heat-induced aggregates. In this study, we considered the properties of soluble aggregates of pure β-Lg having a median diameter of 50 nm. The behavior of the aggregates at the air/water interface has been probed as a function of pH, with the aim of evaluating the controversial role of surface charge in connection with the functionality of particle-stabilized foams. Based on these new experimental results, it would appear that charge shielding around the isoelectric point (pI) leads to significantly increased foam stability as compared to samples having a significant positive or negative zeta potential. Against expectations, however, maximum foam stability was not linked to minimum foam drainage. High foamability and foam stability have been found to correlate with maxima in the rates of initial surface pressure increase and with interfacial dilatational properties. Evidence for efficient stabilization of the air/water interface was also reflected in a small average bubble size and a low rate of mean bubble area increase for aggregates with pH ∼ pI. Information from additional comparative experiments on systems with native β-Lg enabled an evaluation of the significance of surface hydrophobicity and aggregate particle size in relation to the foaming properties.
    Keywords: Β-Lactoglobulin ; Heat-Induced Aggregation ; Foaming Properties ; Surface Properties ; Surface Charge ; Engineering ; Chemistry
    ISSN: 0927-7757
    E-ISSN: 1873-4359
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