2.5. Vitamin C analyses
The concentration of ascorbic acid and total vitamin C (ascorbic plus dehydroascorbic acid) were measured, following the direct method developed by Romeu-Nadal, Morera-Pons, Castellote, and Lopez-Sabater (2006). Briefly, to determine the ascorbic acid con- tent, milk was mixed with metaphosphoric acid to precipitate the proteins and stabilize the ascorbic acid.