Anna-Sophie Hager

Investigation of product quality, sensory profile and ultrastructure of breads made from a range of commercial gluten-free flours compared to their wheat counterparts

Bread is a major staple food consumed daily in all parts of the world. A significant part of the human population cannot tolerate gluten, a storage protein found in wheat, rye and barley, and therefore, products made from alternative cereals are required. During this study, the bread-making potential of seven gluten-free flours, wheat and wholemeal wheat flour was compared. Fermentation potential of the different flours was determined, showing that dough development height of gluten-free and wholemeal wheat samples was lower than for wheat and oat flour. Apart from standard bread quality parameters such as loaf-specific volume and physical crumb texture, also water activity and shelf life have been determined. The shelf life of gluten-free breads was reduced compared to wheat bread. Aroma profiles were evaluated by a trained panel. Wheat, oat and wholemeal wheat breads were liked moderately, while the remaining samples had lower liking scores. Crumb grain characteristics were investigated using image analysis, and microstructure was observed by scanning electron microscopy. Overall, only breads produced from oat flour were of similar quality to wheat bread, and the utilization of buckwheat, rice, maize, quinoa, sorghum and teff flours resulted in breads of inferior quality.

Influence of Gallic Acid and Tannic Acid on the Mechanical and Barrier Properties of Wheat Gluten Films

Vital wheat gluten, a byproduct of wheat starch production, is a highly functional ingredient having a unique viscoelasticity that makes it ideal for the production of edible biodegradable films. However, its functional properties must be modified to ensure sufficient strength and elasticity, in addition to water vapor barrier properties. In this study, vital gluten was modified using tannic and gallic acid. It was found that the addition of tannic acid resulted in stiffer, more resistant, and less resilient and flexible films, having as well decreased water vapor permeability. Tannic acid containing films became reddish brown, whereas gallic acid addition did not have an influence on the film appearance. Films containing gallic acid became more elastic. Gallic acid was found to potentially act like a plasticizer. Scanning electron microscopy was used to investigate the ultrastructure of the produced films.

Influence of dextran-producing Weissella cibaria on baking properties and sensory profile of gluten-free and wheat breads.

Breads based on gluten-free buckwheat, quinoa, sorghum and teff flours were produced with addition of 20% sourdough fermented with exopolysaccharide (EPS) producing Weissella cibaria MG1. Wheat bread was baked as a reference. Dough rheology, bread quality parameters and sensory properties of the sourdough-containing breads were compared to sourdough non-containing control breads of the respective flour. The specific volume remained unaffected by sourdough application. In buckwheat, sorghum, teff and wheat sourdough breads acidification increased crumb porosity compared to control breads. Crumb hardness was significantly reduced in buckwheat (-122%), teff (-29%), quinoa (-21%) and wheat sourdough breads (-122%). The staling rate was significantly reduced in buckwheat, teff and wheat sourdough breads. Water activity of the sourdough containing bread crumb was not influenced by the presence of EPS. Due to the presence of exopolysaccharides (EPS) and influence of acidification, the dough strength, AF, as measured by oscillation tests decreased significantly in sourdough-containing buckwheat, sorghum and wheat dough, but increased in sourdough-containing quinoa and teff dough. Microbial shelf-life was significantly prolonged neither for gluten-free sourdough nor for wheat sourdough breads. Scanning electron microscopy of control and sourdough bread crumbs did not show differences concerning structural starch features. In addition, the aroma of most bread was not improved by sourdough addition.

Physical and molecular changes during the storage of gluten-free rice and oat bread.

Gluten-free bread crumb generally firms more rapidly than regular wheat bread crumb. We here combined differential scanning calorimetry (DSC), texture analysis, and time-domain proton nuclear magnetic resonance (TD (1)H NMR) to investigate the mechanisms underlying firming of gluten-free rice and oat bread. The molecular mobility of water and biopolymers in flour/water model systems and changes thereof after heating and subsequent cooling to room temperature were investigated as a basis for underpinning the interpretation of TD (1)H NMR profiles of fresh crumb. The proton distributions of wheat and rice flour/water model systems were comparable, while that of oat flour/water samples showed less resolved peaks and an additional population at higher T2 relaxation times representing lipid protons. No significant crumb moisture loss during storage was observed for the gluten-free bread loaves. Crumb firming was mainly caused by amylopectin retrogradation and water redistribution within bread crumb. DSC, texture, and TD (1)H NMR data correlated well and showed that starch retrogradation and crumb firming are much more pronounced in rice flour bread than in oat flour bread.

Development of gluten-free fresh egg pasta based on oat and teff flour

Due to increased awareness of consumers about the relationship between food and health as well as the requirements of people following a gluten-free diet, the production of cereal products from raw materials other than wheat is of interest. However, the elimination of the visco-elastic gluten protein represents a technological challenge. During this study, response surface methodology was applied to determine optimal formulations for the production of egg pasta from oat and teff flour. Wheat flour was used as a control. The resulting products were characterised regarding firmness and elasticity, stickiness and cooking loss. The results showed that the mechanical texture of oat and teff pasta was comparable to wheat pasta, however, elasticity was significantly reduced. Compositional analysis was carried out on flour raw materials as well as on the final pasta products, showing that regarding fibre and mineral content, oat and teff samples are nutritionally superior to wheat. In addition, the microstructure was investigated by means of scanning electron microscopy, allowing also the observation of structural changes occurring during cooking. Upon cooking, a distinct outer layer can be observed, resulting from protein denaturation and starch gelatinisation. This structural feature is clearly visible for cooked wheat pasta and but is less apparent for teff and oat pasta.

Formulating breads for specific dietary requirements

Abstract: The number of people following a certain diet, either prescribed by the doctor or voluntarily, is growing and the so-called diseases of civilization such as obesity, type-2-diabetes, coronary heart disease and colorectal cancer are increasing. Therefore, growing interest exists in the manufacture of breads for specific dietary requirements and breads with increased nutritional value. This chapter will discuss wheat allergy and coeliac disease and the formulation of wheat/gluten-free breads. The concept of glycaemic index and glycaemic load will be explained and an overview of the production of breads with low glycaemic index through incorporation of sourdough, whole grains and different dietary fibres will be given.