Resistant starch formation in bread as influenced by choice of ingredients or baking conditions

The formation of resistant starch (RS) in bread products was evaluated in vitro in relation to the processing conditions. The impact of the particular baking conditions applied to pumpernickel bread was investigated as well as the presence of malt and sourdough acids, commonly present in such bread. Also studied was the potential effect of including wholemeal barley from a high-amylose genotype. In some bread, the rate of hydrolysis of the potentially available starch fraction was evaluated by an in vitro procedure. A low-temperature, long-time baked product (20 h at 120 °C) contained significantly higher amounts of RS (5.4%, starch basis) than a corresponding ordinary baked bread (40min at 200 °C) (3.0%, starch basis). Addition of lactic acid increased RS recovery further (6.6% starch basis), whereas malt had no impact on RS yield. The highest level of RS was noted in a long-time baked bread based on high-amylose barley flour (7.7%, starch basis). In contrast to all other products, this bread also displayed a lowered rate of amylolysis of the non-RS fraction (hydrolysis rate index = 68). It is concluded that exchanging ordinary baking conditions for pumpernickel baking, particularly in the presence of certain organic acids, may substantially increase the RS content.