A study on fibre addition to gluten free bread: its effects on bread quality and in vitro digestibility.

The aim of this study was to assess the impact of fibre addition on gluten-free (GF) dough properties and bread technological quality, and on protein and starch in vitro digestibility. Soluble (Inulin, In) and insoluble fibres (oat fibre, OF, and type IV resistant starch, RSIV) were used at 5 and 10% substitution levels. Dough firmness increased when insoluble fibres were added, and decreased when In was used. Incorporation of insoluble fibres resulted into bread with a low specific volume (SBV) since firmer dough were more difficult to expand during proofing and baking. Staling rate was reduced after fibre addition, with the exception being OF 10%, as its lower SBV may have favoured molecule re-association. In general, protein and starch digestibility increased when fibres were added at 5%, and then decreased after further increasing the level. Fibres may have disrupted bread crumb structure, thus increasing digestibility, although the higher addition may have led to a physical and/or chemical impediment to digestion. Inulin has well-known physiological effects, while RS presented the most important effect on in vitro starch digestibility (GI). These results showed the possibility of adding different fibres to GF bread to decrease the GI and increase protein digestibility, while obtaining an overall high quality end-product.

Gluten-free breadmaking affected by the particle size and chemical composition of quinoa and buckwheat flour fractions.

This study aimed at assessing the effect of physicochemical properties and the particle size of different fractions of buckwheat and quinoa on the behaviour of gluten-free dough and bread quality. Quinoa and buckwheat grains were milled with a hammer mill and then separated in three fractions. These fractions where then re-milled with a cyclonic mill to obtain samples of similar sizes. Results showed that the chemical composition of these fractions was very different and played a major role on bread quality. Proteins, lipids and fibre negatively affected bread quality, whereas starch-rich fractions were more adequate for breadmaking. Re-milling quinoa and buckwheat fractions increased bread volume, although chemical composition still influenced bread properties. For hammer-milled fractions, both the finest fractions resulted in breads with higher technological quality, as well as a final product with more fibre, minerals and proteins.