Reference Number: 51
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.
SIGNIFICANCE OF THIS STUDY
Cereal products are the most important sources of starch in the diet and large amounts of starch escape digestion and absorption in the human small intestine and are fermented our gut microbes to release beneficial compounds called short chain fatty acids. Such starches that cannot be broken down by us humans but can only be broken down by our gut microbes is commonly referred to as resistant starch (RS). Resistant starches play an important role in bulking up faeces and acting as a source of food to our microbes. Owing to the formation of short chain fatty acids during the breakdown or fermentation of resistant starches and bulking up faeces, these starches may have an important role in preventing colon cancer. Cereal grains contribute to a large amount of these resistant starched to our diet. The current paper showed that a prolonged baking process enhanced the levels of resistant starch in baked breads and the addition of lactic acid bacteria (sourdough fermentation) increased the levels of resistant starches by 6%.