Hubert Chiron

Effect of Puroindolines on the Breadmaking Properties of Wheat Flour

ABSTRACT The role of lipid-binding proteins from wheat seed (puroindolines) on the breadmaking properties of wheat flour was investigated by determining the relationship between breadmaking quality and puroindoline content in samples of 32 wheat cultivars. An inverse relationship was mainly explained by the link between hardness and puroindoline contents. This link is in agreement with previous results which have shown a close structural identity between basic friabilins and puroindolines. Next, the effect of puroindolines in breadmaking was investigated by performing reconstitution experiments with two puroindoline-free hard cultivars of opposite quality (Florence Aurore and Ecrin) as indicated in the screened wheat sample. Addition of 0.1% puroindolines to these flours drastically modified both the rheological properties of doughs and the structure of the bread crumb. Puroindolines are essential to the foaming properties of dough liquor, and a close relationship was found between the fine grain crumb pr...

In situ Fast X-ray Tomography Study of the Evolution of Cellular Structure in Bread Dough During Proving and Baking

The use of fast in-situ X-ray computed micro-tomography with careful 3D image analysis has allowed the development of gas cell structure during dough fermentation to be followed, within a volume close to 0.1 cm 3 with a resolution of 15 μm. Yeast and liquid (water +oil) contents were modified in the dough composition. The evolution of dough was followed until the void volume fraction reached 0.7, after an inflection point. The gas cell and cell wall size distributions were determined by granulometry and their initial values were respectively 180 and 240-300 μm. The evolution of the mean cell wall size displayed a minimum plateau (180-240 μm) in a time interval [ t 1 , t 2 ]. Before t 1 , bubbles grow freely and beyond t 2 , coalescence appears to prevail, as shown by the irregular structure depicted by the cell size distribution. The value of t 1 is found to increase by a factor of 2 when the concentration of yeast is reduced by 2, and replacing 5% water by 10% oil also increases t 1 . Both changes of composition lead to more irregular cellular structures. Similar analyses were performed during the baking step, which allowed the interval of temperature for crumb setting to be determined, and showed that little change of cellular structure occurred during baking.

Modelling Wheat Flour Dough Proofing Behaviour: Effects of Mixing Conditions on Porosity and Stability

Kinetics of porosity and stability of dough expansion during proofing have been fitted with Gompertz and exponential models, respectively, for 24 distinct mixing conditions and same dough composition. Data for 10 conditions were used to relate the parameters of the models to mixing variables, specific power, and texturing time, through power regression models. Interpretation of the relationships between the mixing variables and the parameters of the Gompertz and exponential models emphasises the influence of dough rheological properties on dough expansion during fermentation and likely on bubbles distribution. The prediction performances of these porosity and stability models were evaluated using the root mean square error and mean absolute percentage error, for time series of the remaining 14 mixing conditions. The results show that integrating the mixing variables into the models significantly improves the prediction accuracy compared to control models whose parameters values are arithmetic means. Finally, we present an application where the mixing variables are determined in order to obtain a dough exhibiting the desired features during proofing, such as high levels of porosity and stability. Intensive mixing yields the best result but a more interesting trade-off can be obtained with intermediary mixing processes.

A polyphasic approach to study the dynamics of microbial population of an organic wheat sourdough during its conversion to gluten-free sourdough.

To develop a method for organic gluten-free (GF) sourdough bread production, a long-term and original wheat sourdough was refreshed with GF flours. The dynamics of the sourdough microbiota during five months of back-slopping were analyzed by classical enumeration and molecular methods, including PCR-temporal temperature gel electrophoresis (PCR-TTGE), multiplex PCR, and pulsed field gel electrophoresis (PFGE). The results showed that the yeast counts remained constant, although Saccharomyces cerevisiae, present in the initial wheat sourdough, was no longer detected in the GF sourdough, while lactic acid bacteria (LAB) counts increased consistently. In the first phase, which was aimed at obtaining a GF sourdough from wheat sourdough, Lactobacillus sanfranciscensis, L. plantarum, and L. spicheri were the main LAB species detected. During the second phase, aimed at maintaining the GF sourdough, the L. plantarum and L. spicheri populations decreased whereas L. sanfranciscensis persisted and L. sakei became the predominant species. Multiplex PCRs also revealed the presence of several L. sakei strains in the GF sourdough. In a search for the origin of the LAB species, PCR-TTGE was performed on the flour samples but only L. sanfranciscensis was detected, suggesting a flour origin for this typical sourdough species. Thus, while replacement of the wheat flour by GF flour influenced the sourdough microbiota, some of the original sourdough LAB and yeast species remained in the GF sourdough.

Processing & rheological properties of wheat flour dough and bread containing high levels of soluble dietary fibres blends

Wheat flour doughs were processed with soluble dietary fibres (DF) added up to 40% (w/w flour). DF were made of a ternary mixture of maltodextrins (MT, 3/5), pectins (PE, 1/5) and inulin (IN, 1/5). The addition of DF decreased the specific mechanical energy developed by the mixer, mainly because of water addition. It increased the ratio of storage moduli and the elongational viscosity of the dough, but decreased the strain hardening index. Energy input and rheological changes at mixing largely explained the decreases of porosity characteristic time and stability time during fermentation. It was possible to add up to 30% DF with a moderate increase of bread density, and 20%, with little change of crumb cellular structure. Hence, the changes of bread crumb texture were not mainly due to bread density, but rather likely to the changes of properties of the intrinsic material. Results obtained by addition of single fibre source, especially inulin, deviated from the main trends observed for texture and rheological properties. These results provide a good basis to design breads with increased dietary fibre content.

Information for decision-making is ubiquitous: Revisiting the reverse engineering mode in breadmaking technology

This paper deals with the process of decision making in the reverse engineering mode and highlights the need for polyvalent information. Three aspects are considered. 1) Reverse engineering implies a preliminary assumption: having defined a desired outcome of the decision process. Defining goals on the possible outcomes is a complex, multi-actor process based on ubiquitous information. Once identified at best, several alternative scenarios may lead to the desired outcome. The first issue consists in evaluating these alternative scenarios. 2) While taking into consideration the positive consequences that the different alternatives will generate, the decision process has to allow for possible negative impacts, which are not explicitly expressed in the defined goals. We thus consider the reverse engineering process has to be bipolar and take rejections into account. 3) Finally, the simultaneous achievement (respectively, avoidance) of several goals (respectively, rejections) is not always possible and depends, in particular, on whether the actions leading to each of these goals (respectively avoiding these rejections) are compatible or not. We thus seek the “best” compatible set of actions and propose to define it as optimizing the bipolar preferences expressed on the outcomes. The approach is both graphical and logical and is focused on a case study in breadmaking technology.

Basic Knowledge Models for the Processing of Bread as a Solid Foam

The breadmaking process can be defined by the succession of operations with operating conditions as input variables and dough properties as output ones, any output variable at step i being an input at step i+1. In this paper, we strive to show how the main properties of bread, density, porosity and alveolar structure (crumb), can be predicted from basic knowledge models (BKMs). So we have defined the variables of breadmaking, proposed BKMs for the two first operations, mixing and proofing, and underlined the needs to define them for shaping and baking, after a short review of existing models. The specific energy delivered during mixing is determined by a simple balance equation in order to predict gluten structuration and dough viscosity, the main output of mixing operation. Then an analysis of dough proofing at different structural scales, by rheology and imaging, allows to assess its alveolar structure, and to fit the kinetics of porosity and stability by phenomenological models. Finally we show how these BKMs could be integrated in order to help the design of baked products with target properties.

The effect of organic wheat flour by-products on sourdough performances assessed by a multi-criteria approach

In this study, we determined the effect of organic (i) flour ash content (1%-1.4%) and (ii) flour by-product addition (bran, shorts and germ) on sourdough performances. After five consecutive back-sloppings, sourdough was used for bread-making and its bread-related properties were assessed. No effect of flour composition factors (i & ii) on sourdough lactic acid bacteria and yeasts were highlighted. Nonetheless, they greatly altered lactic acid and acetic acid sourdough contents from 6.9 to 17.4 g/kg and from 0.9 to 2.2 g/kg, respectively. The flour ash content (i) had a significant and positive effect on sourdough acidity and CO2 production. Bread made with sourdough with a high ash content had a significantly higher acidity and specific volume. These physicochemical differences between breads were perceived by sensory evaluation in a significant way. Sourdough supplemented (ii) with germ had higher lactic acid and carbon dioxide contents than sourdough supplemented with bran and shorts. Hence, flour composition, combining ash content and flour by-products, appears to be an effective factor to obtain a better control of sourdough performances.