Impact of malting process on the amino acid profile of buckwheat seeds

Buckwheat is a gluten-free pseudocereal recognised as an important source of protein. Malting is a form of processing that can improve the protein quality of food. The aim of this study is the optimization of malting conditions on protein content and its essential amino acids on buckwheat seeds. To achieve this goal, soaking time was optimised to a moisture content of 50% (2h) and the drying time to a moisture content below 10% (4h). Quantification of protein and amino acid (AA) profile was determined after different soaking and germination conditions. Design of experiments was applied to optimise the malting process, considering 2 factors and 3 levels: time (24, 48 and 72 h) and germination temperature (18, 23 and 28 ºC). The experiments were performed in 2 blocks considering the soaking temperature (20 ºC and 30 ºC). Moisture was determined by the AOAC method, 952.08. Total nitrogen content was assessed by the Kjeldahl method. AA profile was performed after acid hydrolysis by UPLC with a PDA detector. Concerning protein, soaking temperature increased significantly at 30 ºC, (13.7 ± 1.45 g/100g) when compared with soaking at 20 ºC (12.08 ± 1.43 g/100g). For all essential AA, at a soaking temperature of 20 ºC, germination time was the only significant factor with the best germination conditions at 48 h. The soaking temperature of 30 ºC, produces the best germination conditions at 72 h, with an exception on methionine where both factors, temperature and time, constitutes significant factors. For methionine, the best conditions were found at 23 ºC with 48 h of germination. In conclusion, results demonstrate that in the tested conditions, the levels that can be used to improve the quality protein of buckwheat seeds were: 30 ºC for soaking step and 18 ºC during 48 h for germination step. This work reveals a valuable tool that can be used in domestic or in controlled environments, as industries, for the improvement of protein quality of this gluten-free pseudocereal.

Este trabalho foi desenvolvido com o apoio da FCT.

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