Titralab at1000 series

In the screening experiments with different inocula, the gas composition was analysed by gas chromatography according to Westerholm et al. (2012 (link)). Short-chain VFA (C2-C6) were quantified by ion-exclusion chromatography according to Westerholm et al. (2012 (link)). Process pH was measured with a Hanna instrument HI83141 (Woonsocket, Rhode Island, United States). Ammonium and sulphate were analysed with a spectrophotometer (Spectroquant® Nova 60A photometer; MilliporeSigma, Burlington, MA, USA) with reagent test kits from the series Supelco (Merck, Darmstadt, Germany). The total alkalinity was calculated as the amount of acid required to bring the sample to pH 4.4. Titration was carried out with an automatic titrator (TitraLab® AT1000 series; Hach, Düsseldorf, Germany).

Analyses of pH, titratable acidity (TA), and total soluble solids (TSS) were carried out following the methodology proposed by Nicolau-Lapeña et al. [27 (link)]. The pH and TA of the samples were determined using an automatic titrator (Titralab AT1000 Series, HACH, Vésenaz, Switzerland). The TA was determined by titration with 0.1 M of NaOH, previously diluting the experimental juices by half in distilled water (1:1, v/v). TA was expressed as g of malic acid/L. TSS content was determined using a digital refractometer (Atago Co., Ltd., Tokyo, Japan) with a range of 0–45% and expressed in °Brix.