Impact of Fermentation, Autoclaving and Phytase Treatment on the Antioxidant Properties and Quality of Teff Cookies.

Abstract

Teff [Eragrostis tef (Zucc.) Trotter] is an underutilised cereal crop grown mainly in Ethiopia and Eritrea. It is an excellent source of dietary fibre, vitamins, minerals and bioactive compounds. However, it also contains a high amount of phytic acid, which is an antinutrient and reduces the bioavailability of minerals and proteins. To improve the nutritional quality of teff, the phytic acid content should be reduced by an effective dephytinisation method. In this study, various dephytinisation methods (fermentation, autoclaving and phytase treatment) were used to dephytinise teff flour. Undephytinised and dephytinised teff flour was mixed into wheat flour (0-40 %) to improve the functional properties of cookies. Twenty different cookie formulations were prepared according to 4x5x2 factorial design. The physical, chemical, nutritional and sensory properties of the cookies were investigated. Among the dephytinisation methods, fermentation produced the most effective reduction in phytic acid mass fraction (181 mg/100 g), followed by phytase treatment (198 mg/100 g). The protein, fat, Fe and Zn content and antioxidant activity of cookies enriched with dephytinised teff flour were comparable to cookies fortified with undephytinised teff flour. Moreover, the dephytinised teff cookies had lower phytic acid mass fractions. The cookies containing 40 % teff flour had higher antioxidant activity and nutritional quality than the control wheat cookies. The use of dephytinised teff flour reduced the spread ratio and the a* and b* values of cookies compared to undephytinised flour. Cookies containing fermented and phytase-treated teff flour had a harder texture than cookies containing undephytinised flour. In addition, as the amount of teff flour increased, the spread ratio values of cookies gradually incrased while their hardness decreased. Overall acceptability scores of cookies containing 10-20 % teff flour were similar to the control. To the best of our knowledge, this is the first study to determine the quality of cookies containing dephytinised teff flour. The data highlight the potential of dephytinised (especially autoclaved and phytase-treated) teff flour (up to 20 %) as a functional ingredient to enrich the mineral content and antioxidant capacity of foods. Furthermore, this study shows that fermentation, autoclaving and phytase treatment can be used to improve the nutritional quality of grains.