Investigations on Dry Beans (Phaseolus Vulgaris L.): Microstructure, Processing, and Antinutrients (Phytic Acid, Tanning, Enzyme Inhibitors)
Deshpande, Sudhir Shahurao
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https://hdl.handle.net/2142/72221
Description
Title
Investigations on Dry Beans (Phaseolus Vulgaris L.): Microstructure, Processing, and Antinutrients (Phytic Acid, Tanning, Enzyme Inhibitors)
Author(s)
Deshpande, Sudhir Shahurao
Issue Date
1985
Department of Study
Food Science
Discipline
Food Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Food Science and Technology
Abstract
The role of microstructure in processing and effects of several processing methods on antinutrients of dry beans were investigated. Proximate composition of whole beans showed minor differences among the ten varieties investigated. Most correlations between selected chemical constituents and physical characteristics were relatively low. Dry beans had a well-organized ultrastructure with all the characteristic features of a typical legume. Initial water uptake rates during soaking were characteristic of each variety. The hilum and micropile along with a loosely arranged cell structure on the raphe-side of the hilum, a deeply-grooved hilar fissure, and a narrow tracheid bar were the most important structural features affecting the initial water uptake of beans. The seed coat played a dominant role only after its initial resistance to water uptake was ovecome.
Water uptake (W) during early stages of cooking was also characteristic of the variety. Although the optimal cooking times varied widely (52-85 min), all the beans absorbed similar amounts of water when cooked for their optimal times. All varieties absorbed nearly 1.5 times their weight of water and attained a moisture content of about 65% (wet basis) when cooked for their optimal times.
Excepting tannins, dehulling significantly increased phytic acid and enzyme inhibitory activity. Soaking in sodium bicarbonate or mixed salt solutions was more effective in removing these antinutrients than soaking in water. Cooking and germination followed by cooking were the most effective methods in the elimination of dry bean antinutrients. However, no single method could effectively remove or eliminate all the undesirable components of dry beans.
Since protein-bound tannins are usually not detected by the procedures routinely employed for their analyses, several parameters that might influence the commonly used vanillin, Folin-Ciocalteu and Prussian blue assays for tannins of dry beans were investigated.
Both phytate and tannins were potent inhibitors of digestive enzymes. The enzyme inhibitory fractions of legume tannins could be selectively removed by adsorption on starch. However, such tannin-starch association decreased the in vitro digestibility of several starches investigated. Considering their heat-stable nature and interactions with proteins and carbohydrates, the residual phytate and tannins in processed beans may lower the overall nutritional quality of legumes. (Abstract shortened with permission of author.)
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