We investigated the fractionation of casein micelles and the whey protein β-lactoglobulin (β-LG) of skim milk by crossflow microfiltration (0.1 μm) for the first time by a novel approach as a function of membrane length and membrane resistance. A special module was constructed with 4 sections and used to assess the effects of membrane length by measuring flux and β-LG permeation (or transmission) as a function of transmembrane pressure and membrane length. Depending on the position, the membranes were partly controlled by a deposit layer. A maximum for β-LG mass flow through the various membrane sections was found, depending on the position along the membrane. To study the effect of convective flow toward the membrane, membranes with 4 different intrinsic permeation resistances were assessed in terms of the permeation and fouling effects along the flow channel. From these findings, we derived a ratio between transmembrane pressure and membrane resistance, which was useful in reducing the effect of deposit formation and, thus, to optimize the protein permeation. In addition, the fouling effect was investigated in terms of reversible and irreversible fouling and, in addition, by differentiation between pressure-induced fouling and adsorption-induced (pressure-independent) fouling, again as a function of membrane length.

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Lactobacillus sanfranciscensis is a key organism of the lactic microflora in traditional and industrial sourdough fermentations. In this paper we provide evidence for the formation of heterooligosaccharides (HeOS) by L. sanfranciscensis during growth in sourdough. To identify the HeOS based on HPAEC-PAD analysis, HeOS standards were synthesized by enzymatic reactions with L. sanfranciscensis levansucrase in a chemically defined system in the presence of raffinose, maltotriose, maltose, xylose, or arabinose as acceptor carbohydrates. The oligosaccharides known to originate from the corresponding acceptor reactions, 1 F -β-fructosylraffinose, 1 F -β-fructofuranosylmaltotriose, erlose (1 F -β-fructofuranosylmaltose), xylsucrose, 1 F -β-fructosylxylsucrose, and arabsucrose, were identified by HPAEC-PAD. Evidence for the formation of further tri-, tetra-, and pentasaccharides was provided. Wheat doughs with sucrose were fermented with L. sanfranciscesis TMW 1.392 or the isogenic, levansucrase-negative strain TMW 1.392∆lev, and the analysis of dough extracts or invertase-treated dough extracts provided evidence for the formation of arabsucrose and erlose in sourdough in addition to 1-kestose and nystose.

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