The ascorbic acid (AA) present within the sample was extracted in 2% metaphosphoric acid solution in double distilled water. AA content was measured by the direct colorimetric method based on its ability to decolorize 2,6-dichlorophenol-indophenol dye solution as described by Ranganna (2007). Interference was avoided by rapid determination and the corresponding AA content was obtained from a standard curve drawn for pure l-ascorbic acid (Sigma-Aldrich) solution which varied within 0.2 to 1 g·L− 1 of AA. The relative loss in AA content (in %) of treated sample was calculated with respect to the untreated sample.