Abstract
Inulin can improve the nutritional quality of gluten free (GF) bread and have a prebiotic activity. However, breadmaking might frustrate the enrichments efforts due to inulin loss. In this study we aimed at studying the inulin enrichment of GF bread. Two different yeasts [having normal (Y1) or reduced (Y2) invertase activity] were used to leaven the breads enriched with five marketed inulins, which differed for the degree of polymerization (DP) and the manufacturer. Inulin replaced 10% of the rice flour and had low, intermediate or high DP, which ranged from 2 to 20; ≈20; ≥20, respectively. Fructan hydrolysis occurred during leavening of Y1-GF breads, reaching losses up to 40% after baking, depending on the diverse DP of the inulin-forming fructans. Inulin loss was less relevant in Y2-GF breads (up to 5% after baking) than Y1-GF breads. Crumb texture was not negatively influenced by inulin presence, even if this was high (e.g., Y2-GF breads). Information collected within this study may provide further insight to better optimize a GF bread formulation in view of inulin enrichment.
Highlights
Inulin-type fructans (ITFs) are plant-derived storage polysaccharides formed by multiple fructose units linked by β-(2–1) fructosyl-fructose linkages
The inulin manufacturer significantly influenced the amount of fructans after proofing and the simple sugar content of the gluten free (GF) breads
Inulin enrichment has been recommended for improving the healthiness of GF breads
Summary
Inulin-type fructans (ITFs) are plant-derived storage polysaccharides formed by multiple fructose units linked by β-(2–1) fructosyl-fructose linkages. These polysaccharides are mostly linear, a small number of branched units with β-(2–6) linkages may exist. The ITFs with an average DP lower than 10 units are named fructo-oligo saccharides (FOS), while above 10 they are named inulin (Drabińska et al, 2017). By applying separation techniques it is possible obtaining ITFs ingredients containing either a mixture of fructans with a specific DP or a certain share of fructans with a desired DP. Various inulin mixtures ranging from 10 to 60 DP are currently marketed as food ingredients (Roberfroid, 2007)
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