Effect of Grain Tef (Eragrostis tef (Zucc.) Trotter) Flour Substitutions with Flaxseed on Mineral Content, Antioxidant Activity, Phytic Acid Content and Microbial Quality of Injera

Abstract

There is an increased global interest in the food industry to develop and market functional foods in which scientific investigations are limited in Ethiopia. Tef injera functional character can be further enhanced by substitution with flaxseed which is known to bear functional ingredients (α-linolenic acid an ω-3 fatty acid, secoisolariciresinol diglycoside lignans, dietary fibre and proteins). Two flaxseed forms (whole and flour) and three flaxseed substitution levels (3%, 6% and 9% flaxseed) arranged in a factorial experimental design in three replications were cofermented to find out whole or flour and at what substitution level injera with better nutrient and functional potential can be processed. Tef injera (100%) was used as a control. Tef injera substituted with flaxseed (whole and flour) at 3%, 6% and 9% showed a significant (P<0.05) effect on minerals (except P), ferric ion reducing antioxidant power (FRAP), phytic acid and microbial quality of injera. With 9% flaxseed substitution FRAP, Zn and Ca contents  percentage increase were: 102, 110 and 16; whereas phytic acid and Fe decreased by 76 and 19, respectively from the control. Between 2 to 6 injera storage days, yeast-mould (2.27 to 3.93 log cfug^-1) and total aerobic plate counts (ND to 3.77 log cfug^-1) were lowest for 9% flaxseed
substitution and highest for the control injera (2.85 to 4.08 log cfug-1 and 3.70 to 4.30 log cfug^-1, respectively). Coliforms were not detected. Whole flaxseed substituted injera had high minerals, antioxidant and microbial stability than flour flaxseed substituted injera. Injera with high minerals (except iron) and antioxidant of improved microbial stability, low phytic acid contents can be processed by 9% flaxseed substitution.