Submitted to: Institute of Food Technology
Publication Type: Abstract Only
Publication Acceptance Date: 6/18/1997
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Cooking of beans induces cell wall crystallization and decreases starch bioavailability. Following cell wall crystallization, the cells are resistant to breakage even when finely milled with a Wiley mill or Udy Cyclone mill. The impact of mechanical disruption of crystallized cell wall on starch bioavailability in cooked beans was examined enzymatically. Presoaked beans were cooked for different times at 115.5C in cans. The cooked beans were freeze-dried and milled with a Udy Cyclone mill (1 mm screen) to produce precooked flour. Additional grinding of the flour at cryogenic temperature (-195C) with a 6700 SPEC Freezer/Mill was conducted in an attempt to disrupt the crystallized cell walls. An enzyamatic procedure using B-amylase and pullulanase was used to selectively digest gelatinized starch to estimate starch bioavailability. The rigidity of the cell walls was greater in Pinto verses Navy beans. The longer the cooking time, the greater the rigidity of cell walls in cooked beans. Microscopic observations revealed that cryogenic milling effectively disrupted the crystallized cell wall resulting in 7 to 12-fold increases in starch availability. Reheating (15 min) of cryogenically milled bean flour showed maximum starch bioavailability for all samples while reheated conventionally milled flour resulted in decreased available starch due to intact rigid cell walls. Heat-induced cell wall crystallization during bean cooking is a primary barrier to starch digestibility. Cryogenic milling was necessary to achieve complete starch digestibility.