Increase in Tannin Content of Some Selected Nigerian Vegetables during Blanching and Juicing

Aims: This study was set to investigate the content of tannin in fresh, blanched vegetables and juiced extracts from the commonly consumed vegetables in South-Western Nigeria.
Place and Duration of Study: Chemical science department, Redeemers University, Nigeria. Research work was done between January and March, 2013.
Methodology: The vegetables were obtained from four different major markets in South West, Nigeria and grouped into three: fresh, blanched, and juiced, using standard laboratory procedures to analyze tannin content.
Results: The results from fresh vegetables showed that Amaranthus viridis has the highest tannin level (30.20±1.05 mg/100g dry weight) while lowest was in Veronia amygdalina (1.02±0.02 mg/100g dry weight). Also, in blanched vegetables Amaranthus viridis has the highest tannin level (46.81 mg/100g dry weight) and lowest was found in Corchorus oliterus (5.05 mg/100g dry weight). In the juiced extract however, Launea taraxacifolia has highest tannin level (735.77 mg/100g dry weight) while lowest was recorded in Celosia argentea (67.18 mg/100g dry weight).
Conclusion: It can be concluded from this study that juicing and blanching substantially increase tannin content in most vegetables.