Mechanical, microstructure and permeability properties of a model bread crust: Effect of different food additives

The aim of this study was to understand the action of different additives on the crust properties using a layer crust as a model. Moisture content, water vapor barrier properties, water sorption isotherms and mechanical properties were evaluated. Crust model showed multilayer internal structure. Glycerol (10% and 20%) and HPMC-10% increased moisture content, whereas linolenic acid and beeswax, glycerol-1%, HPMC-0.5% and citric acid significantly decreased it. Water vapor permeability (WVP) decreased with lipids and citric acid, due to their hydrophobic nature and crosslinking action, respectively. Hydrophobic additives lowered the WVP of the crust and provided water barrier properties and brittle texture. Crust mechanical properties were greatly correlated with water present as well as with composition of crust layer. Barrier properties of the crust layer were greatly dependent on the hydrophilicity or hydrophobicity of the additives, which determined the internal interactions between starch and proteins and the microstructure and mechanical properties.The authors acknowledge the financial support of Spanish Scientific Research Council (CSIC), the Spanish Ministry of Economy and Sustainability (Project AGL2011-23802), and the Generalitat Valenciana (Project Prometeo 2012/064). R. Altamirano-Fortoul would like to thank her PhD Grant to CSIC.Altamirano Fortoul, RDC.; Hernández Muñoz, PA.; Hernando Hernando, MI.; Molina Rosell, MC. (2015). Mechanical, microstructure and permeability properties of a model bread crust: Effect of different food additives. Journal of Food Engineering. 163:25-31. https://doi.org/10.1016/j.jfoodeng.2015.04.019S253116

Influence of amyloglucosidase in bread crust properties

Enzymes are used in baking as a useful tool for improving the processing behavior or properties of baked products. A number of enzymes have been proposed for improving specific volume, imparting softness, or extend the shelf life of breads, but scarce studies have been focused on bread crust. The aim of this study was to determine the use of amyloglucosidase for modulating the properties of the bread crust and increase its crispness. Increasing levels of enzyme were applied onto the surface of two different partially bake breads (thin and thick crust bread). Amyloglucosidase treatment affected significantly (P<0.05) the color of the crust and decreased the moisture content and water activity of the crusts. Mechanical properties were modified by amyloglucosidase, namely increasing levels of enzyme promoted a decrease in the force (Fm) required for crust rupture and an increase in the number of fracture events (Nwr) related to crispy products. Crust microstructure analysis confirmed that enzymatic treatment caused changes in the bread crust structure, leading to a disruption of the structure, by removing the starchy layer that covered the granules and increasing the number of voids, which agree with the texture fragility.Authors acknowledge the financial support of Spanish Ministry of Economy and Sustainability (Project AGL2011-23802), the European Regional Development Fund (FEDER), Generalitat Valenciana (Project Prometeo 2012/064) and the Consejo Superior de Investigaciones Cientificas (CSIC). R. Altamirano-Fortoul would like to thank her grant to CSIC. The authors also thank Forns Valencians S. A. (Spain) for supplying commercial frozen partially baked breads.Altamirano Fortoul, RDC.; Hernando Hernando, MI.; Molina Rosell, MC. (2014). Influence of amyloglucosidase in bread crust properties. 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Moisture distribution and textural changes in stored model sandwiches

Moisture migration and instrumental and sensory texture changes were determined in model cheese sandwich structures in which bread water activity was varied by glycerol level. Sandwiches and components were evaluated both after assembly and 4-week ambient storage by uniaxial compression and mathematical description of stress-strain relationships, assessment of sensory characteristics by a trained panel, correspondence between predicted and actual stress-strain relationships, and mass-balance analysis of moisture migration between cheese, bread crumb and bread crust. Textural changes occurred as a result of both aging and moisture migration, and the accuracy of fitted “predicted” stress-strain relationships of the composites varied according to the extent of moisture migration. Sensory assessments of key textural attributes of sandwich composites and components, before and after storage, were significantly correlated with measured mechanical parameters

Use of multivariate analysis of MIR spectra to study bread staling

Different kinds of bread, stored at constant temperature and at controlled humidity conditions for a week since their manufacturing date, were analysed by Attenuated Total Reflectance-Fourier Transform InfraRed (ATR-FTIR) spectroscopy. The collected spectra were processed by Principal Component Analysis (PCA), in order to evaluate the changes occurring during bread ageing. For the sake of comparison, the 1060-950 cm(-1) spectral window has been also investigated by curve-fitting methods. It was observed that the first PC increases monotonically with ageing of samples. Furthermore, the more influential variables on PCl correspond to spectral regions where are located stretching and bending bands, which are mainly attributed to typical starch bonds vibrations