For pH determination, 0.85% NaCl solution was poured into a
beaker containing 20 g of marc until a volume of 100 ml was
reached and stirred on a rotary shaker at 100 rpm/min for 15 min.
pH measurement was performed with a pH metre (Radiometer
Copenhagen PHM82, Cecchinato, Italy) by dipping the electrode
directly into each sample. Three independent measurements were
performed for each sample. Marc sugar content was determined by
the method of Fehling