Reference Number: 101
Year: 2009
Link: Link to original paper
Health: IBS
Nutrition: Arabinoxylan | Beta-glucans | Fibre
Intolerance & Sensitivity: FODMAPS
Summary
Introduction
Aim
In this study the content of dietary fiber and dietary fiber components in whole-grain rye (n=18) were analyzed.
Results
The average total content, when fructan was included, was for dietary fiber 19.9% (range of 18.7-22.2%) and for extractable dietary fiber 7.4% (range of 6.9-7.9%). Arabinoxylan was the main dietary fiber component, with an average total content of 8.6%, followed by fructan (4.1%). During baking of whole- grain rye bread, only small changes in total content of arabinoxylan, arabinogalactan, and -glucan occurred, while the content of resistant starch increased and the content of fructan decreased in a baking-method-dependent manner. The molecular-weight distribution of extractable arabinoxylan in the flour was analyzed with a new method and ranged from 4 × 104 to 9 × 106 g/mol, with a weight average molecular weight of about 2 × 106 g/mol. During crisp bread making, only a limited degradation of arabinoxylan molecular weight was detected, while a notable degradation was observed in sourdough bread. The molecular weight of extractable -glucan in the whole-grain rye flour ranged from 104 to 5 × 106 g/mol, with a weight average molecular weight of 0.97 × 106 g/mol.
SIGNIFICANCE OF THIS STUDY
The current study sheds light to the influence of sourdough processing on the structural changes of dietary fibre mainly beta glucans. The study found that the structure of beta glucans changed during the sourdough process, mainly in its molecular weight. Beta glucans had a lower molecular weight after the sourdough process which means that it might have been broken down to smaller units by specific enzymes. The study points to a useful hint to minimise this phenomenon by stating that the molecular-weight decrease was smallest when the dough was made with flour with a high falling number (i.e., lowest enzyme activity) which may indicate hat the endogenous beta glucan-degrading enzymes in the flour mixture were responsible for the decrease. Although the structure of beta glucans may be altered to some extent during the sourdough process, the reduced molecular weight beta glucan in the breads may still be of nutritional importance because it is well- known that the concentration, conformation, and molecular weight of polymers are related to viscosity and that gut viscosity is related to many nutritional effects, including both glucose regulation and cholesterol-lowering properties.