Surface Layer Properties of Dough Liquor Components: Are They Key Parameters in Gas Retention in Bread Dough?
Gas cell stability during bread making is controlled by both surface and bulk properties. This paper is focused on studying the surface properties of the water-soluble phase of the dough, the dough liquor (with and without lipids), as well as the composition of the air/water interface. Using infrared reflection measurements, we showed that in lipid-poor liquor, proteins are the dominant species present at the air/water interface. With complete liquor (including the lipids), a mixed interface of protein and lipids is obtained. However, the presence of lipids in the surface layer did not significantly affect the surface pressure. We also added enzymes to the flour to evaluate in what way the surface-active properties of the liquor components can be affected. These results were compared to the effect of adding a surfactant [diacetyl tartaric esters of mono- and diglycerides (DATEM)]. Biobake 10804, a xylanase that increased the arabinoxylan content of the dough liquor, decreased the surface pressure and increased the dilational modulus in lipid-poor liquor. This effect was not observed with the liquor including the lipids. Lipopan 50 BG, a 1,3-specific lipase, increased the surface pressure of the liquor that included the lipids. Lipopan F BG, which converts polar lipids to their lyso form, strongly increased the surface pressure not only in the lipid-containing liquor but also in the lipid-poor liquor. DATEM, as expected, increased the surface pressure while strongly decreasing the dilational modulus. Results of these studies were used to help explain changes in loaf volume observed in a series of baking tests, using the same enzymes and additives. This led to the conclusion that the effect of surface-active components alone cannot account for the larger loaf volumes observed. Clearly, both the effect of bulk and interfacial rheological properties should be considered together when explaining gas cell stability.
Key wordsGas cell stability Surface activity Lipases Xylanase Dough liquor DATEM
The authors would like to thank Jolan de Groot for her experimental contribution. Also, Peter Wierenga is kindly acknowledged for his help with IRRAS measurements.
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