Enhancement of Gluten Quality and Rheology in Sunn Pest ( <i>Eurygaster</i> spp.)–Damaged Wheat Flour Using Plant Extracts

In this study, the potential to improve the technological quality of sunn pest (Eurygaster spp.)-damaged wheat (SPDW) flours using plant extracts rich in phenolic compounds (black tea, green tea, green coffee beans, sage, hibiscus, and blueberry) was investigated. Extracts obtained under optimal conditions were evaluated using a modified Zeleny sedimentation test, and it was determined that hibiscus and blueberry extracts considerably reduced sunn pest protease activity. Consequently, subsequent investigations utilized only these two promising extracts, which were incorporated into flour blends containing 0%, 10%, 20%, and 30% (w/w) SPDW flour. Evaluations consistently demonstrated that increased sunn pest damage negatively affected gluten quality and dough rheology. However, the addition of hibiscus and blueberry extracts, especially in delayed gluten analyses and at the high sunn pest blend ratio (30%), contributed to the preservation of the gluten network structure. Regarding dough resistance to extension and extensibility, both extracts showed a markedly improved effect compared with the control and the other plant extracts initially tested. Farinograph analyses further confirmed that these extracts, especially blueberry extract at a 10% blend ratio, significantly increased dough stability and farinograph quality number, while simultaneously decreasing the degree of softening (p < 0.05). PRACTICAL APPLICATIONS: These findings demonstrate that hibiscus and blueberry extracts have substantial potential to partially mitigate the quality deterioration observed in flours affected by varying degrees of sunn pest damage, thereby improving gluten functionality, overall dough performance, and bread-making quality. Moreover, unlike many chemical additives commonly used to date, these functional, natural remedial agents, together with the growing demand for "clean label" products, offer more reliable alternatives.