Nutritional value of broad bean seeds. Part 3: Changes of dietary fibre and starch in the production of commercial flours.

Abstract

We report on the impact of flour production from small- and large-seed varieties of broad bean on the quantitative and qualitative distribution of dietary fibre and starch. The experimental material consisted of the seeds of small-seed varieties of broad bean: Gobik and Goral, large-seed varieties of broad bean: Windsor Bialy and Bartom, and pea seeds of Albatros, Karat and Miko varieties (for comparison). The seeds were at full physiological maturity. Soaking and hydrothermal processing were shown to cause multidirectional, statistically significant changes in dietary fibre and starch, depending on both parameters of the process and type of the seeds. The flours of both small-seed broad bean varieties contained 20.15%-28.31%, flours of the large-seed broad bean 23.10%-27.50%, and those from pea seeds 20.13%-22.81% total dietary fibre. Attention should be paid to the considerable, approximately 2-fold increase in the soluble dietary fibre (SDF) content, compared to the raw material. The processing of seeds caused significant changes also with reference to starch. The most considerable changes were observed when the variant with the longest times of soaking (18 h) and heating (45 min) was applied. In the broad bean flours, the content of analytically available starch decreased by 22.94-30.60% and its digestibility was observed to decrease up to 30.25%. The pea flours, however, were characterised by an increased concentration of both forms of starch, especially significant for the digestible starch. The calculated content of resistant starch (RS) differentiated, to a high extent, the flours obtained. Under the same processing conditions, the flours of small-seed Gobik and Goral varieties of broad bean were characterised by a significantly higher RS content than those obtained from the large-seed varieties. A decrease in the starch digestibility rate index (SDRI) values, especially high for the small-seed varieties, should also be emphasised. The results obtained indicate that the nutritional value of flours can be determined by controlled processing parameters.