Influence of amylases on the rheological properties of wheat flour with partially damaged starch

G BARRERA; PD RIBOTTA; E PEREZ; GT PEREZ; AE LEON

Rosario, Argentina

Congreso; 1a ICC Latinoamerican Conference on Cereals and Cereal Products; 2007

ICC

Amylases hydrolyze starch molecules to give diverse products including dextrins and smaller polymers composed of glucose units, and they are used to prevent staling and improve the texture and flavor of baked goods. During wheat milling a portion of the starch granules sustains mechanical damage. Damaged starch causes higher water absorption capacity, which affects negatively dough physicochemical properties and rheological behaviour. The aim of this work was to study the impact of amylases on rheological behaviour of flours with different levels of damaged starch. Enzymes used were á-amylase (Fungamyl 2500SG), maltogenic amylase (Novamyl 10000BG) and amyloglucosidase (AMG 800BG), and mixtures of them, á-amylase+maltogenic amylase, á-amylase+amyloglucosidase and á-amylase+maltogenic amylase+amyloglucosidase. Unmodified wheat starch was milled in a disc mill in order to cause a greater rupture of starch granules. Two flours were prepared mixing partially damaged wheat starch and vital gluten (85:15 starch:gluten ratio). Flour 1 and flour 2 had 4.74% and 14.33% damaged starch content, respectively. Dough-mixing properties of flours were examined with a Brabender farinograph. Pasting properties of samples were determined using a Micro-Viscoamylograph (Brabender). Dough stickiness was determined using the SMS/Chen-Hoseney Dough Stickiness (TA.XT2i Texture Analyzer). Farinograph parameters changed significantly with the level of damaged starch and the addition of amylases.  Water absorption and development time incremented as damaged starch content increased. a-amylase and their mixtures decreased water absorption and development time in flour 2. Farinograph stability decreased as damaged starch content increased. Enzyme addition to both flour 1 and 2 decreased dough stability, except maltogenic amylase which increased stability when it was added to flour 1. Pasting profile, as measured by Viscoamylograph, was modified by damaged starch content and enzyme addition. Peak viscosity, viscosity at the end of cooling period and setback decreased as damaged starch content increased. In general, maltogenic amylase decreased dramatically peak viscosity. Pasting temperature did not change with the increment of damaged starch content and the addition of amylases. Stickiness was determined from dough mixed using water proportion based on farinograph absorption. Flour 2 showed higher stickiness than flour 1 due to their greater damaged starch content. Only addition of á-amylase to flour 1 and amyloglucosidase to flour 2 increased dough stickiness. It was shown that an increment in the damaged starch content changed dramatically dough-mixing properties, pasting profile and dough stickiness demonstrating the significance of damaged starch levels in determining flour properties. In general, addition of amylases and their mixtures modified dough-mixing properties and pasting profile of partially damage starch flour demonstrating amylase functionality in processing starch containing foods.