S. Chevallier

Optimization of Gluten-Free Formulations for French-Style Breads

The formulation of gluten-free bread, which will be suitable for patients with coeliac disease, was optimized to provide bread similar to French bread. The effects of the presence of hydrocolloids and the substitution of the flour basis by flour or proteins from different sources were studied. The added ingredients were (1) hydrocolloids (carboxymethylcellulose [CMC], guar gum, hydroxypropylmethylcellulose [HPMC], and xanthan gum), and (2) substitutes (buckwheat flour, whole egg powder, and whey proteins). The bread quality parameters measured were specific volume, dry matter of bread, crust color, crumb hardness, and gas cell size distribution. Specific volume was increased by guar gum and HPMC. Breads with guar gum had color characteristics similar to French bread. Hardness decreased with the addition of hydrocolloids, especially HPMC and guar. Breads with guar gum had the most heterogeneous cell size distribution, and guar gum was therefore selected for further formulations. Bread prepared with buckwheat flour had improved quality: an increased specific volume, a softer texture, color characteristics, and gas-cell size distribution similar to French bread. Bread with 1.9% guar gum (w/w, total flour basis) and 5% buckwheat flour (of all flours and substitutes) mimicked French bread quality attributes.

Physicochemical behaviors of sugars, lipids, and gluten in short dough and biscuit

The structure of short dough and biscuit has been characterized at a macroscopic level (dimensions, bulk structure) and a microscopic level (starch damage, protein aggregates, microstructure) by physical and biochemical methods. The baking process of short dough induces a large decrease of the product bulk density from 1.26 to 0. 42 (+/-0.01) g.cm(-)(3) for final biscuit, leading to a cellular solid with a thin colored surface and a porous inner structure. Proteins appear aggregated in biscuit when compared to short dough, whereas starch granules remain almost intact in biscuits. The components which are involved in the cohesiveness of short dough and biscuit final structure have been identified. They suggest that short dough is a suspension of solid particles in a liquid phase being an emulsion of lipids in a concentrated sugar solution. The role of sugars in biscuit structure suggest that biscuit structure is a composite matrix of protein aggregates, lipids and sugars, embedding starch granules.

A 2D non-linear grey-box model dedicated to microwave thawing : Theoretical and experimental investigation

Abstract A grey-box model, based on a priori knowledge about heat transfer with phase change and on microwave effects approached by a continuous function, is proposed to simulate the thawing of food in a microwave guide in fundamental TE1,0 mode. The partial differential equation describing heat transfer with phase change is reduced into a lumped parameters system using a 2D finite volumes scheme. The heating due to the microwaves is considered in the heat equation as the spatial variation of the microwave power flux. Flux variation is approached by a continuous function of temperature and of the wave power, whose coefficients are estimated via reverse techniques. Finally, the model is validated during the thawing of a block of tylose filling the section of the wave guide.

Salt reduction in sheeted dough: A successful technological approach

The challenge of reducing the salt content while maintaining shelf life, stability and acceptability of the products is major for the food industry. In the present study, we implemented processing adjustments to reduce salt content while maintaining the machinability and the saltiness perception of sheeted dough: the homogeneous distribution of a layer of encapsulated salt grains on the dough during the laminating process. During sheeting, for an imposed deformation of 0.67, the final strain remained unchanged around 0.50 for salt reduction below 50%, and then, increased significantly up to 0.53 for a dough without salt. This increase is, in fine, positive regarding the rolling process since the decrease of salt content induces less shrinkage of dough downstream, which is the main feature to be controlled in the process. Moreover, the final strain was negatively correlated to the resistance to extension measured with a texture analyzer, therefore providing a method to evaluate the machinability of the dough. From these results, a salt reduction of 25% was achieved by holding 50% of the salt in the dough recipe to maintain the dough properties and saving 25% as salt grains to create high-salted areas that would enhance the saltiness perception of the dough. The distributor mounted above the rollers of the mill proved to be able to distribute evenly salt grains at a calculated step of the rolling out process. An innovative method based on RX micro-tomography allowed to follow the salt dissolving and to demonstrate the capability of the coatings to delay the salt dissolving and consequently the diffusion of salt within the dough piece. Finally, a ranking test on the salted perception of different samples having either an even distribution of encapsulated salt grains, a single layer of salt grains or a homogeneous distribution of salt, demonstrated that increasing the saltiness perception in salt-reduced food product could be achieved by a technological approach.

Potential of near-infrared hyperspectral imaging spectroscopy to quantify water content in biscuits

The aim of this work was to evaluate the suitability of Near-Infrared Hyperspectral Imaging Spectroscopy (NIR-HSI) for the quantification of water content in commercial biscuits. Ten biscuits from two commercial brands were conditioned for one week in desiccators with different water activities controlled by different saturated solutions of salts. Biscuits were analyzed by NIR-HSI and resulting images are analyzed by Principal Components Analysis (PCA). A regression model is also computed using a small number of variables in order to predict moisture values for each pixel and reconstruct prediction images in false color. These results obtained by PCA show that the water content of the two brands of biscuits can be easily monitored by NIR-HSI. The determination coefficient (R2) obtained by regression is higher than 0.925 and the Root Mean Square Error of Validation (RMSEV) less than 1.815. Prediction images are very relevant and can be used to study biscuits defects.

Study of (SSD) Biscuit Baking by Dynamic Thermal Analyses (DMTA, DSC, TGA)

The baking process of sheeted short dough (SSD) biscuits involves the transformation from a viscoelastic dough into a cellular solid, with a final texture. This process is induced by the expansion of the material submitted to the vaporization of water and gases from leavening powders. Meanwhile, rheological properties of the matrix, which are modified by water losses, thermal denaturation and melting of dough components, reduce the impact of the expansion phenomenon. The objective of this work is to relate the changes of rheological properties of biscuit dough during thermal treatment to structural modifications of the product from molecular level to macroscopic scale.