The orange and guava juices (100 % fruit juice) of five different brands were purchased from supermarkets. For fresh fruit juices (orange and guava), one was purchased from a local market, where the juices were prepared daily and stored in the refrigerator (maximum storage time before use was 4 h), and another was prepared in the laboratory.
To prepare fresh fruit juices, 100 g of guava fruit was homogenized with 100 mL of 0.05 % EDTA and 1 % MPA, while 100 g of oranges was squeezed in order to obtain the juice.