Changes in ACE inhibitory and antioxidant activities in alcalase treated idli batter and idli after fermentation

Idli is a cereal-legume fermented food consumed widely in India. Fermentation and addition of external enzymes have been suggested as methods for release of bioactive peptides from parent proteins. The present study was aimed at exploring the changes in angiotensin-I converting enzyme (ACE) inhibitory and antioxidant activity of 14 h fermented idli batter treated with alcalase in varied amounts (100-700 U/g batter) kept at 30 ± 2 °C. Various batter parameters along with sensory attributes of cooked idli were assessed. The viscosity (12170-7795 cP) and rise in volume (29-20 mL) of batter decreased with addition of alcalase in the batter when compared with control batter (14130 cP, 31 mL). The free amino nitrogen content and radical scavenging activity of alcalase treated batter exhibited an increase by 2-5 and 2-7 fold, respectively while ACE inhibitory activity showed a decrease in IC₅₀ value (lowest being 52.53 ± 1.12 mg/mL of batter containing 600 U alcalase/g batter) when compared with the control fermented set. The hardness and bulk density values of control cooked idli was 0.59 kg and 0.53 g/cm³, respectively while alcalase treated idlis showed a range of 0.71-1.68 kg and 0.53-0.69 g/cm³. The overall acceptance of idli prepared from alcalase treated batters till 600 U/g batter was judged as 'good' by semi-trained panellists. Moreover, the ACE inhibitory and radical scavenging activity of cooked idli prepared from 600 U alcalase/g batter showed enhancement over the control idli. Thus, alcalase treated idli shows potential to be used as a functional food.