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Enzymes are used in baking to improve dough handling properties and the quality of baked products. Glucose oxidase (GO) is an enzyme with oxidazing effect due to the hydrogen peroxide released from its catalytic reaction. In this study, the macroscopic effect of increasing glucose oxidase concentrations on wheat dough rheology, fresh bread characteristics and its shelf life during storage was determined. A reinforcement or strengthening of wheat dough and an improvement of bread quality can be obtained with the addition of GO, although inverse effects were obtained when excessive enzyme levels were added. The analysis of the gluten proteins at molecular level by high performance capillary electrophoresis and at supramolecular level by cryoscanning electron microscopy revealed that the GO treatment modified gluten proteins (gliadins and glutenins) through the formation of disulfide and nondisulfide crosslinks. The high molecular weight glutenin subunits showed to be the most susceptible glutenin fraction to the oxidation action of GO. Excessive addition of GO produced an excessive crosslinking in the gluten network, responsible of the negative effect on the breadmaking properties.

Enhancement of water transport and microstructural changes induced by 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 2 Abstract 25The main aim of this work was to evaluate the effect of high intensity ultrasound 26 on drying kinetics of orange peel as well as its influence on the microstructural 27 changes induced during drying. Convective drying kinetics of orange peel slabs 28were carried out at 40 °C and 1 m/s with (AIR+US) and without (AIR) ultrasound 29 application. Drying kinetics analysis was addressed by considering diffusion 30 theory in order to identify the influence of ultrasound on water transport. Fresh, 31 AIR and AIR+US dried samples were analyzed using Cryo-Scanning Electron 32Microscopy. Results showed that drying kinetics of orange peel were 33 significantly improved by the ultrasonic application, which involved a significant 34 (p<0.05) improvement of both mass transfer coefficient and effective moisture 35 diffusivity. The effects on mass transfer properties were confirmed from 36 microstructural observations. In the cuticle surface of flavedo, the pores were 37 obstructed by the spread of the waxy components, this fact evidencing the 38 ultrasonic effects on the interfaces. The cells of the albedo were degraded by 39 application of ultrasound as it brought about large intercellular air spaces 40 facilitating water transfer through the tissue. 41

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