Staining methods for dough systems - Impact on microstructure and functionality

- Rhodamine B has no impact on the rheological functionality of dough.
- Solely the staining procedure affected dough functionality.
- Rapid freezing weakens dough rheology and microstructure.
- Drop technique affects dough rheology and microstructure due to a dilution effect.
- Bulk water technique does not influence dough functionality.

The staining of dough systems with fluorescent dyes is crucial for a specific visualization of structural components by the confocal laser scanning microscopy (CLSM). However, there is no comprehensive study published until now, if the staining method or the dye itself influences the microstructural formation, and if a realistic visualization can be ensured. Therefore, three common staining methods (drop-, bulk water- and rapid freezing technique) were analysed with varying concentrations of the dye Rhodamine B on their effect on protein microstructure and dough rheology. Rheological results showed significant differences (p < 0.001) to a standard, unstained dough when using drop- or rapid freezing technique resulting in a lower stiffness (loss of 12% and 17%, respectively). Protein network analysis revealed no significant differences in microstructure with increasing dye concentrations, but between the three staining methods. Thus, the dye itself did not affect dough microstructure or functionality by interactions on the structure. However, a change in micro- and macrostructure of dough was identified for drop- and rapid freezing technique. In contrast, the addition of dye by bulk water had no influence on dough microstructure and rheology. Concluding, microstructures of wheat dough can be analysed in a realistic, non-invasive way by bulk water technique.