Influence of pH and calcium concentration on milk protein fractionation by 0.1 μm microfiltration at low temperatures

2021 ◽  
Vol 118 ◽  
pp. 105048 ◽  
Author(s):  
Simon Schiffer ◽  
Lara Vannieuwenhuyse ◽  
Chrisanty Susianto ◽  
Martin Hartinger ◽  
Ulrich Kulozik
Foods ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 692
Author(s):  
Roland Schopf ◽  
Florian Schmidt ◽  
Johanna Linner ◽  
Ulrich Kulozik

The fractionation efficiency of hollow fiber membranes (HFM) for milk protein fractionation was compared to ceramic tubular membranes (CTM) and spiral wound membranes (SWM). HFM combine the features of high membrane packing density of SWM and the more defined flow conditions and better control of membrane fouling in the open flow channel cross-sections of CTM. The aim was to comparatively analyze the effect of variations in local pressure and flow conditions while using single industrially sized standard modules with similar dimensions and module footprints (module diameter and length). The comparative assessment with varied transmembrane pressure was first applied for a constant feed volume flow rate of 20 m3 h−1 and, secondly, with the same axial pressure drop along the modules of 1.3 bar m−1, similar to commonly applied crossflow velocity and wall shear stress conditions at the industrial level. Flux, transmission factor of proteins (whey proteins and serum caseins), and specific protein mass flow per area membrane and per volume of module installed were determined as the evaluation criteria. The casein-to-whey protein ratios were calculated as a measure for protein fractionation effect. Results obtained show that HFM, which so far are under-represented as standard module types in industrial dairy applications, appear to be a competitive alternative to SWM and CTM for milk protein fractionation.


2021 ◽  
Vol 259 ◽  
pp. 118050
Author(s):  
Simon Schiffer ◽  
Andreas Matyssek ◽  
Martin Hartinger ◽  
Peter Bolduan ◽  
Peter Mund ◽  
...  

1983 ◽  
Vol 38 (9-10) ◽  
pp. 845-847 ◽  
Author(s):  
Hector Barrabin ◽  
Leopoldo de Meis

ATP and GTP as substrate for phosphorylation of sarcoplasmic reticulum ATPase are compared. Maximal levels of phosphoenzyme are between 4.5 and 4.8 nmol per mg of protein when either substrate is used provided that phosphoenzyme hydrolysis are strongly inhibited by high calcium concentration (20 mм) and low temperatures ( 0 ° C ) . The maximal values obtained with GTP are lower than those previously reported. It is shown that this difference is due to underestimation of the specific activity of labeled nucleotides used in previous studies, as revealed by UV absorption and HPLC analysis. The dependence of the phosphoenzyme levels on calcium concentration, pH and temperature confirm previous findings indicating that ATP, but no GTP, accelerates the rate limiting step of the catalytic cycle.


2020 ◽  
Vol 605 ◽  
pp. 118110
Author(s):  
Martin Hartinger ◽  
Simon Schiffer ◽  
Hans-Jürgen Heidebrecht ◽  
Joseph Dumpler ◽  
Ulrich Kulozik

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