Processing effects on the total antioxidant activity and total phenolic contents of Saluyot (Corchorus olitorius L.) leaves

The effect of the length of exposure (0,5, 10, and 15 mins) of saluyot leaves containing varying amounts of salt (0, 2, 4 and 6 g/L of water) at different temperatures (room temperature (25 deg C), 50 deg C, 75 deg C, and 100 deg C) on the total antioxidant activity and total phenolic content were measured spectrophotometrically using the modified Ferric Thiocyanate Method and the Folin-Ciocalteau Micromethod, respectively. Specific antioxidant compounds were identified using High Performance Liquid Chromatography (HPLC). The identified antioxidant compounds in saluyot leaves were gallic acid, vanillic acid, ferulic acid,luteolin, quercetin, diadzein, and genistein. Large peaks in the chromatograms were not identified due to limited standards. Vanillic acid and gallic acid concentrations were the highest among the identified compounds. Room temperature had the significantly highest total antioxidant activity, total phenolic content and concentr ation levels of the antioxidant compounds. An increasing temperature, salt concentration and time of exposure had significantly decreased the antioxidant activity, total phenolic content and concentration levels of the antioxidant compounds. However, there was significantly higher total antioxidant activity and total phenolic content at 100 deg C compared to 75 deg C. Combined treatments of heat, salt and time of exposure on the total antioxidant activity, total phenolic content and concentration levels of the identified antioxidant compounds present in saluyot leaves were also studied. This study shows that the effect of time and salt were temperature dependent. No definite trend can be derived from the effect of different salt concentrations. With an increased in temperature and time of exposure on the total antioxidants activity and total phenolic content. The total antioxidant activity and the total phenolic content of saluyot leaves had a positive moderate linear correl ation. Vanillic acid, quercetin and luteolin were moderately correlated with both the total antioxidant activity and total phenolic content, whereas genistein and diadzein were moderately correlated with the total phenolic content.