ABSTRACT
Thermal treatments such as baking, roasting, drying, microwaving, and extrusioncooking can affect the amount and composition of dietary fiber. The making of bread is not accompanied by great changes in TDF during the different stages of preparation such as dough processing or baking. The content of insoluble hemicelluloses decreases as the content of the soluble hemicellulose increases. The RS content starting from the doughmaking step results in higher dietary fiber values at the time of cooling. There is an elevated lignin content, especially in the crust, which increases with baking time. Baking of rye bread with sour dough or with lactic and acetic acid enhances the DF content by formation of RS and diminishes the non-starch polysaccharide fraction; the loss in the insoluble hemicelluloses starts with dough making. The cellulose is not degraded. The repeated heating of starch-rich foods like pasta, potatoes or rice shows the possibility of accumulation of RS. Cooking increases the DF content of potato by formation of RS. In vegetables and fruit the amount of pectic substances decreases with boiling. The greatest changes in the DF content is with extrusion cooking. The total amount of DF is nearly the same, as with most products. The content of soluble fiber increases with increased severity of treatment.
