Abstract
A protocol for determining the characteristic temperatures of thermomechanical transitions on gluten-free flour doughs is proposed. This protocol is based on the mathematical analysis of experimental curve of storage modulus (G′) vs temperature obtained by means of Dynamic Mechanical Thermal Analysis (DMTA) technique. Doughs at constant consistency of chestnut flour with different levels (3, 6 and 9% flour basis, f.b.) of brown seaweed (Bifurcaria bifurcata, Fucus vesiculosus and Ascophyllum nodosum) powders addition, 2% f.b. of guar gum and 1.8% f.b. of salt with different water absorption were used to test the proposed protocol. The ranges of temperatures corresponding to starch gelatinization (59–97 °C), amylopectin crystallites melting (82–101 °C), reversible dissociation of lipid-amylose complexes (107–128 °C) and amylose melting (133–171 °C) showed a strong dependence with water absorption of samples. Doughs with the same water absorption submitted to starch gelatinization during mixing were also analysed to corroborate the protocol suitability. Total polyphenols content and radical scavenging activity of extracts from chestnut flour-seaweed powder blends and seaweed-enriched chestnut cookies baked at 180 °C were determined. Extraction assisted with ultrasounds was carried out employing acetone-water (70:30 v/v) solution as solvent during 4 min with a liquid/solid ratio of 30 w/w. Seaweed powder addition had a positive effect on antioxidant properties of doughs before baking. However, the seaweed powder addition effect on baked products (cookies) is not clear due to antioxidant activity is overlapped by Maillard's products generated during baking.
Highlights
Dough can be defined as a blend of flour and water, obtained by involving mechanical energy to obtain a final mixed product
A protocol for the determination of characteristic temperatures of thermal transitions was satisfactorily tested employing Dynamic Mechanical Thermal Analysis (DMTA) on glutenfree flour doughs based on chestnut flours supplemented with brown seaweed powders (Ascophyllum nodosum, Bifurcaria bifurcata and Fucus vesiculosus)
Results show that characteristic temperatures of starch gelatinization (G), melting of amylopectin crystallites (M1), amyloselipid transition (M2) and amylose melting (M3) that take place in gluten-free flour doughs can be determined employing the proposed protocol of determination
Summary
Dough can be defined as a blend of flour and water, obtained by involving mechanical energy to obtain a final mixed product. Once a dough is obtained after kneading, the study on the transformations during thermal process promoted during baking is essential to estimate and control the final product properties. The starch gelatinization involving the swelling of the amorphous region and subsequent melting of crystallites, usually named as G transition, is well studied by its importance in starch processing for food and non-food purposes. At intermediate water content the melting of crystallites is partially postponed to higher temperatures in form of another peak known as M1 transition [4, 5]. At higher temperatures (>140 C) amylose melting transition can be observed [4] and is labelled as M3 transition [6] These transitions depend on water content of the sample
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