Tef and fonio-morphology, determination of amino acids, phenolic compounds and antioxidant capacity of two gluten-free grains

Abstract

Global demand for gluten-free products is rising, however, currently most lack protein and are nutritionally insufficient. Tef and fonio, two nutritious gluten-free cereals might provide a good alternative. To evaluate their composition, a detailed profiling of their free amino acid (AA) and phenolic composition was performed, using UPLC-QqQ-MS/MS, in addition to TPC and antioxidant activity. Grain morphology was also investigated. Our results reveal the presence of 18 AAs, including all essential, in both tef and fonio. l-asparagine and l-tryptophan were the most abundant, whereas cysteine and glutamine were absent. Levels of lysine were sufficient (4.39 and 6.72 mg g−1 DW for tef and fonio, respectively), but levels of methionine in fonio were low (0.45 mg g−1 DW). TPC was 0.87 and 0.38 mg GAE g−1 DW in tef and fonio, respectively. Eleven phenolic compounds were identified and quantified in both cereals, ranging from 2246 μg g−1 DW to trace levels, with higher levels observed in tef. ABTS Antioxidant activity was 0.25 and 0.15 mg TE g−1 DW for tef and fonio, respectively, typical for cereals and millets. Overall, our work implies that tef and fonio can make a healthful contribution to human nutrition, and specifically be incorporated into gluten-free diet to increase protein and polyphenol consumption.