Easy potentiometer

The Cl content in milk and cheese slurry was measured by potentiometric titration (Titroline Easy Potentiometer) with silver nitrate 0.1 N (VWR International, France)
according to NF EN ISO 5943:2007.
The citrate and lactate contents were measured by enzymatic bio analysis (Enzytec Citric acid, Enzytec Lactic acid, R-Biopharm AG, Darmstadt, Germany). Cheese samples (5 g) were homogenized in 50 mL perchloric acid (1M) using an Ultra-Turax homogenizer. The homogenate was then centrifuged at 18 000 x g for 10 min. The supernatant (20 mL) was adjusted to pH 8-10 with approximatively 4 mL KOH (5M) and placed for 15 min in the refrigerator for the quantitative precipitation of the formed potassium perchlorate, and then filtered. The amount of NADH oxidized in the reactions of the filtrate with the different enzymes was determined by means of its light absorbance at 340 nm and was stoichiometric to the amount of citrate and lactate. For each product the assay was performed in triplicate.

The Cl content in milk and cheese slurry was measured by potentiometric titration (Titroline Easy Potentiometer) with silver nitrate 0.1 N (VWR International) according to ISO (2007b) .
The citrate and lactate contents were measured by enzymatic bio analysis (Enzytec Citric acid, Enzytec Lactic acid, R-Biopharm AG, Darmstadt, Germany), as described in the instructions supplied with the kit. Cheese samples (5 g) were homogenized in 50 mL of perchloric acid (1 M; VWR International, France) using an Ultra-Turrax homogenizer (IKA Labortechnik, Staufen im Breisgau, Germany). The homogenate was then centrifuged at 18,000 × g for 10 min at 4°C. The supernatant (20 mL) was adjusted to pH 8 to 10 with approximatively 4 mL of KOH (5 M; VWR International, Leuven, Belgium) and placed for 15 min at 4°C for the quantitative precipitation of potassium perchlorate, and then filtered. The amount of NADH oxidized in the reactions of the filtrate with the different enzymes was determined by means of its light absorbance at 340 nm wavelength and was stoichiometric to the amount of citrate and lactate. For each product, the assay was performed in triplicate.