ORGANIC ACIDS IN BREAD MAKING AFFECTING GLUTEN STRUCTURE AND DIGESTIBILITY

The importance of wheat in bakery product formulations is mainly due to the ability to form a viscoelastic gluten network, responsible for the technological and sensory quality of bread, pasta, cakes, cookies and other gluten-containing products. The stability of gluten proteins to gastrointestinal digestion is an important factor in inducing immune responses in susceptible individuals, such as celiac disease, wheat allergy and non-celiac gluten sensitivity. Technological processing during bread-making can affect gluten digestion and change how gluten is recognized by the immune system. Several additives, such as organic acids, are used to improve technological properties and conservation of products. Ascorbic acid is used to strengthen the gluten network structure, contributing to the formation of crosslinks between proteins through disulfide bonds. On the other hand, acetic acid contributes to the conservation of bread by reducing pH, although it can cause protein hydrolysis and weakening of the gluten network. The present study aimed to analyze the effect of adding ascorbic acid (at 100 ppm and 200 ppm) or acetic acid (by adding vinegar at 2% and 4% w/w) on rheological properties of the dough and on technological characteristics of the breads, which were submitted to in vitro digestion and analyzed by confocal microscopy, SDS-PAGE and ELISA. The addition of ascorbic acid increased resistance to extension (up to 63%) and storage modulus (G'), while reducing extensibility (up to 25%), indicating the formation of a dough more resistant to flow. Sulfhydryl content confirmed the increase in disulfide bonds promoted by ascorbic acid. Acetic acid, on the other hand, contributed to the reduction of dough development time (up to 44%), stability (up to 20%) and G', resulting in a weaker and less viscoelastic dough. These results were associated with the formation of a more open and less cohesive network, as observed in confocal microscopy. After in vitro digestion of the breads, SDS-PAGE and confocal microscopy indicated that protein degradation started in the gastric phase, with the generation of low molecular weight peptides (smaller than 15 kDa). However, the electrophoretic profile of proteins throughout the digestion process was similar for all treatments. Accordingly, ELISA immunoassay suggested a reduction in gliadin content from the oral to the gastric phase for wheat proteins. At the end of the intestinal phase, samples with ascorbic acid did not differ from the control, whereas acetic acid contributed to a reduction of about 44% in gliadin content. Therefore, the present work contributed to a better understanding of the effects of using organic acids on physicochemical structure, gluten digestibility and immunogenicity of gluten. This knowledge enables a better risk assessment and investigation of possible technological alternatives for bread making with a focus on reducing the immunogenicity of gluten-containing foods.