Effect of blanching on the content of antinutritional factors in selected vegetables

The effect of blanching on the antinutritional content was studied in cabbage, turnip, collard, sweetpotato and peanut leaves. All the vegetables contained various amounts of phytic acid, tannic acid and/or oxalic acid. Tannic acid was found in largest amounts ranging from 1266.00 mg/100 g in cabbage to 491.00 mg/100 g in sweetpotato. Phytic acid content ranged from 0.31 mg/100 g in sweetpotato to 3.97 mg/100 g in collard. Oxalic acid was in trace amounts in cabbage and turnip; but high concentrations were found in sweetpotato (469.67 mg/100 g) and peanut greens (407.00 mg/100 g). Levels of both tannic acid and phytic acid were significantly (p < 0.05) reduced by conventional and microwave blanching methods while oxalic acid levels were not significantly (p < 0.05) reduced in most of the treatments by either of the blanching methods. In general, blanching is recommended as an effective method for reducing the antinutritional factors in green vegetables, however, further investigation on the heating times for both conventional and microwave blanching methods has been suggested.