Titroline alpha

The total soluble solids (in °Brix) were analysed by digital refractometry (Abbemat, Dr. Kernchen, Seelze, Germany) and the density by densitometry (DMA 48, Paar, Ostfildern, Germany). The pH and the total titratable acidity (calculated as citric acid at pH 8.1) were measured potentiometrically (Titroline alpha, Schott, Mainz, Germany). The total phenols were assayed with the Folin-Ciocalteu-method based on a ( +)-catechin calibration using a Konelab 20 Xtr analyser (ThermoFisher, Dreieich, Germany).

Karl-Fischer titration was done with the use of TitroLine Alpha (Schott, Mainz, Germany) device. For each experiment approximately 1.5 g of cellulose sample and 30 mL of Hydranal Solvent E were taken.

After fermentation, the concentration of ethanol, the total extract, the sugar-free extract, the reducing sugars, the titratable and volatile acidity were determined according to standard methods [42 ]. Titratable acidity was calculated from the volume of NaOH used for the titration (TitroLine Alpha, Schott Instruments GmbH (Mainz, Germany)) and expressed as g/L of tartaric acid. The reducing and total sugars were measured using the 3,5-dinitrosalicylic acid method [43 (link)]. The glycerol content was determined according to the standard method [42 ].

Conventional apple pomace, which was enzymatically treated during juice processing, was received from J. Rettenmaier & Söhne GmbH + Co KG (Rosenberg, Germany). The residual moisture content was 2.8 ± 0.3% (w/w) (determined by Karl Fischer titration (Titroline alpha, Schott Instruments GmbH, Mainz, Germany). According to the supplier, the dietary fiber content was 57.2 and the protein content 4.0 g per 100 g dm (dry matter). Thermostable α-amylase Termamyl 120 L (EC 3.2.1.1, from Bacillus licheniformis, 120 KNU·g⁻¹), amyloglucosidase AMG 300 L (EC 3.2.1.3, from Aspergillus niger, 300 AGU·g⁻¹), and protease Alcalase 2.5 L (EC 3.4.21.62, from Bacillus licheniformis, 2.5 AU·g⁻¹ from Novozymes (Bagsværd, Denmark) were used to isolate dietary fiber on a preparative scale. Thermostable α-amylase (EC 3.2.11, from Bacillus licheniformis, 3000 U·mL⁻¹), amyloglucosidase (EC 3.2.1.3 from Aspergillus niger), and protease (EC 3.4.21.14 from Bacillus licheniformis) (used for the analytical dietary fiber approach; the first two enzymes were also used to analyze starch contents), as well as endo-galactanase (EC 3.2.1.89 from Aspergillus niger) and endo-arabinanase (EC 3.2.1.99 from Aspergillus niger) were from Megazymes (Bray, Ireland).

Fischer titration was carried out with the use of Hydranal Solvent E and Hydranal Titrant 5E supplied by Fluka^® (Mettler Toledo, Greifensee, Switzerland). For each experiment, approximately 1.5 g of cellulose sample and 50 mL of Hydranal Solvent E were taken. The water content in the natural filler was established. The measurement was taken using the TitroLine Alpha (Schott^®, Mainz, Germany) device. Cellulose fibers were dried for 24 h at 100 °C (Binder^® oven; crystallizer 70 mm × 40 mm) and, then, left in ambient conditions for 45 min before being investigated (it was impossible to carry out an accurate measurement immediately after taking the sample out of a dryer—too high water absorption rate).