Species-specific changes in protein and phenolic compounds during germination of ancient and modern wheat

Abstract This study evaluated the impact of germination on nutritional and bioactive compounds in seven wheat varieties bred in the Gene Bank of the Czech Agrifood Research Center representing five Triticum species (common, durum, emmer, einkorn, and spelt). Seeds were germinated for up to six days, and changes in crude protein content, total phenolic content, antioxidant activity, and phenolic acid profiles free and bound forms were assessed. Germination led to significant increases in crude protein content across all varieties. For example, in germinated seeds of spelt wheat variety Rubiota crude protein content increased from 19.42% to 21.97% and in emmer wheat variety Rudico from 16.84% to 20.78%. The largest increase of crude protein content was observed between days 4 and 6 of germination. Total phenolic content rose markedly, with emmer wheat variety Rudico and spelt wheat variety Ruth reaching ~ 5.4-fold increase at day 4). Antioxidant activity also increased, peaking at 13.81 ± 0.57 mmol TE/g dw in emmer wheat variety Tapiruz at day 5. Analysis of phenolic acids and phenolic aldehydes revealed that bound forms were predominant contributing 98.77% to total phenolic content. In spelt wheat variety Rubiota, the sum of bound phenolic acids increased from 867.5 ± 85.0 µg/g dw at day 0 to 1983.2 ± 130.6 µg/g dw at day 6. The most significant increases were observed in ferulic acid and p -coumaric acid. Multiple regression and correlation analyses revealed that total phenolic content is a significant independent predictor of antioxidant activity during germination. Specific bound phenolics, especially syringaldehyde and vanillin showed the strongest associations with AA, highlighting their central role in the antioxidant potential of sprouted grains. These results demonstrate that germination enhances the nutritional and functional properties of wheat grains, with ancient species such as a spelt variety Ruth, emmer variety Rudico, and einkorn variety Rumona showing the greatest increases. The predominance of bound phenolic acids highlights their key role in wheat’s antioxidant capacity and potential health benefits.