Fruit extracts for ascorbic acid analysis were obtained by
homogenizing 3 g of guava tissue (pulp and peel) in 20 mL
cold solution of 3% (w/v) oxalic acid plus 8% glacial acetic
acid (v/v) until uniform consistency, using an Ultra-Turrax
homogenizer (T25, Ika Works Inc., USA). The homogenates
were centrifuged at 15,000 rpm at 4 1C for 10 min.
The supernatants were recovered and ascorbic acid
immediately measured.