Bottles of fruit
juices (three for each type of juice originating from two different
batches; n = 6) were stored after opening for 24 and 48 h in the
cold (4–6 C) to assess the effect of time on the concentration of
DHAA. Meta-phosphoric acid and AA (min 99.7%) were purchased
from Merck (Darmstadt, Germany), DL-dithiothreitol (DTT; min
99%) was from Sigma–Aldrich (Steinheim, Germany).