Water mobility and microstructure of gluten network during dough mixing using TD NMR.

This work aimed to establish the relationships between flour components, dough behaviour and changes in water distribution at mixing. TD NMR was used to track water distribution in dough during mixing for different mixing times and hydration levels. Four commercial wheat flours with distinct characteristics were expressly selected to exhibit various dough behaviours at mixing. TD NMR measurements of mixed dough samples revealed four to five water mobility domains depending on the flour type and the mixing modality. A classification tree procedure was used to identify characteristic patterns of water mobility in dough, called hydration states (HS). The HS changes with experimental conditions are highly dependent on flour characteristics, and HS were assigned to physical/chemical changes in the gluten network during dough formation. This study proposes an interpretation of the water distribution in dough based on gluten network development. This will help to adapt the mixing process to the flour characteristics.

Extrusion Simulation for the Design of Cereal and Legume Foods.

A 1D global twin-screw extrusion model, implemented in numerical software, Ludovic®, was applied to predict extrusion variables and, therefore, to design various starchy products with targeted structure and properties. An experimental database was built with seven starchy food formulations for manufacturing dense and expanded foods made from starches, starch blends, breakfast cereals, pulse crop ingredients such as pea flour, fava bean flour, and fava bean starch concentrated, and wheat flour enriched with wheat bran. This database includes the thermal and physical properties of the formulations at solid and molten states, melt viscosity model, extruder configurations and operating parameters, and extruded foods properties. Using extrusion and viscosity models, melt temperature (T) and specific mechanical energy (SME) were satisfactorily predicted. A sensitivity analysis of variables at die exit was performed on formulation, extruder configuration, and operating parameters, generating the extruder operating charts. Results allowed the establishment of relationships between predicted variables (T, SME, melt viscosity) and product features such as starch and protein structural change, density and cellular structure, and functional properties. The extrusion operating conditions leading to targeted food properties can be assessed from these relationships and also the relationship between extrusion operating parameters and variables provided by simulation.

Guiding the formulation of soft cereal foods for the elderly population through food oral processing: Challenges and opportunities.

As the elderly population is growing steadily, more age-friendly food products that allow them to cover their nutritional needs and are enjoyable need to be designed. Since their oral physiology is considerably altered, the study of Food Oral Processing has become an essential discipline in food development, as it takes into consideration the complex interactions between food structure, oral processing, physiology and perception. Cereals are staple foods in many countries, and their consumption as bakery products is popular among the elderly population. In addition, when fortified with pulse proteins, they can help meet the protein needs of seniors and help fight against sarcopenia. For these reasons, this chapter presents an overview of the various aspects involved in the oral processing and formulation of soft cereal foods, translating them into challenges and opportunities that are of relevance to the design of realistic soft cereal foods targeted for the elderly that are nutritious and sensory appealing. This review focuses on the healthy elderly population and does not intend to cover the needs of the dependent elderly suffering from chronical diseases.

Modelling Processes and Products in the Cereal Chain.

In recent years, modelling techniques have become more frequently adopted in the field of food processing, especially for cereal-based products, which are among the most consumed foods in the world. Predictive models and simulations make it possible to explore new approaches and optimize proceedings, potentially helping companies reduce costs and limit carbon emissions. Nevertheless, as the different phases of the food processing chain are highly specialized, advances in modelling are often unknown outside of a single domain, and models rarely take into account more than one step. This paper introduces the first high-level overview of modelling techniques employed in different parts of the cereal supply chain, from farming to storage, from drying to milling, from processing to consumption. This review, issued from a networking project including researchers from over 30 different countries, aims at presenting the current state of the art in each domain, showing common trends and synergies, to finally suggest promising future venues for research.

Influence of ionic plasticizers on the processing and viscosity of starch melts.

Maize starch was plasticized by glycerol, choline chloride ([Chol][Cl]) and ionic liquids (Choline acetate ([Chol][Ace]), 1-Ethyl-3-methylimidazolium Chloride ([EMIM][Cl]) and 1-Ethyl-3-methylimidazolium acetate ([EMIM][Ace]). Melt rheology at 120 °C was assessed with a twin-screw micro-compounder used for processing small quantities (8-10 g), and with a capillary rheometer with pre-shearing (Rheoplast). Qualitative agreement was found between shear viscosities obtained by both rheometry devices, showing the interest of the micro-compounder for screening of plasticizers' influence. The lower shear viscosity values were obtained in presence of [EMIM][Ace] whereas [Chol][Cl] led to the largest ones. Rather than processing induced macromolecular degradation, the glass transition temperature depressing effect of the plasticizers was found to better explain viscosity differences. This underlines the strong influence of the nature of the plasticizers on starch melt rheology. Finally, results from extensional viscosity shows the specific influence of [EMIM][Ace], suggesting that this plasticizer could be particularly relevant for thermoplastic starch processing.

Role of the bolus degree of structure on the protein digestibility during in vitro digestion of a pea protein-fortified sponge cake chewed by elderly.

This study investigated the digestibility of proteins in a pea protein-fortified sponge cake, as well as the impact of the degree of structure of the bolus produced by elderly subjects on the digestibility of proteins by combining ex vivo and in vitro approaches via the standardized protocol INFOGEST. The sponge cakes were consumed by a group of 20 elderly subjects with contrasting physiology, their boli were recovered just before swallowing, and their apparent viscosity was measured to delineate the bolus degree of structure. According to this criterion, two pools were formed with boli from subjects selected at the extremes: low viscosity and high viscosity, with apparent viscosity values (at 120 s-1 ) of 124 ± 18 and 208 ± 19 Pa s, respectively. The sponge cakes and the two pools underwent in vitro digestion. Protein hydrolysis kinetics was followed by measuring the released primary amino groups (NH2 ) and by sodium-dodecyl-sulfate polyacrylamide gel electrophoresis at different time points. For all samples, the representative bands of pea proteins disappear gradually during digestion, accompanied by the appearance of bands indicating the presence of proteins with MW < 15 kDa. In addition, the NH2 concentrations increase over time and do not differ between sponge cake and pea protein isolate. Moreover, the degree of structure of the food bolus has no significant effect on the concentration of NH2 released. These results showed that pea proteins in a fortified sponge cake are bioaccessible under standardized conditions and that the degree of structure of the bolus did not influence protein digestibility for these foods.

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.

How does temperature govern mechanisms of starch changes during extrusion?

Potato and pea starches were processed on a twin-screw extruder under various moisture and thermomechanical conditions, chosen to keep material temperature Te close to starch melting temperature, Tm, whilst avoiding die expansion. Extruded rods were analysed by asymmetrical flow field flow fractionation coupled with light scattering, X-ray diffraction, DSC, and light microscopy with image analysis. Molar mass of extruded materials decreased more for potato than for pea starch, when specific mechanical energy SME increased, likely because of larger amylopectin sensitivity to shear. No crystallinity was detected when ΔT = (Tm-Te) ≤ 0. Residual gelatinization enthalpy ΔHg decreased with ΔT. As illustrated by larger ΔT values for ΔHg = 0, decreasing moisture favored melting, likely by increasing solid friction. The fraction of granular remnants of potato starch was inversely correlated to SME. These results could be explained by considering starch melting during extrusion as a suspension of solid particles embedded in a continuous amorphous matrix.

Thermomechanical characterization of an amylose-free starch extracted from cassava (Manihot esculenta, Crantz).

The aim of this study was to determine and compare the melting (Tm), glass transition (Tg) and mechanical relaxation (Tα) temperatures of a new waxy cassava starch. Thermal transitions measurements were obtained by Differential Scanning Calorimetry (DSC) and Dynamical Mechanical Thermal Analysis (DMTA). The experimental data showed a high correlation between water volume fraction and melting temperature (Tm) indicating that the Flory-Huggins theory can be used to describe the thermal behavior of this starch. The Tm of waxy cassava starch-water mixes were lower than a waxy corn starch-water reference system, but differences were not statistically significant. The mechanical relaxation temperatures taken at tan δ peaks were found 29-38°C larger than Tg. The Tα and Tg measured for waxy cassava starch exhibited similar properties to the ones of waxy corn starch, implying that waxy cassava starch can be used in food and materials industry.

Flow and foam properties of extruded maize flour and its biopolymer blends expanded by microwave.

Maize flour and blends from starch and zein biopolymers were processed as dense materials by extrusion (120°C, 300J·g-1) and press-molding (140°C, 10min) at a constant moisture content (26%wb), and then foamed by microwave heating. The mechanical properties of foams, determined by a 3-point bending test, were governed by density, in agreement with an open solid foam model. The density and 3D cellular structure of the foams were determined by X-ray tomography. In the same interval of density [0.15, 0.3g·cm-3], foams from microwaved materials had a finer cellular structure than directly expanded materials at extruder outlet. The study of melt rheological behavior with Rheoplast® (100-160°C, SME≤200J·g-1) showed that protein content (0-15%) did not affect shear viscosity but increased elongational viscosity. This trend, similar to the one reported for the storage modulus in a rubbery state, could be attributed to dissipative effects in a starch/protein interphase, explaining the difference of expansion between starch, blends and flour.

Predicting the quality of wheat flour dough at mixing using an expert system.

Modelling the links between the mixing process conditions of wheat flour dough and the properties of the dough is a challenge. This paper presents a systematic modelling approach based on qualitative algebra to represent human expertise in this domain. Qualitative models of wheat dough mixing have been implemented as an expert system, called Ascopain. The relations between the process conditions - flour specifications and kneading conditions - and the dough sensory properties, have been formalised by means of qualitative functions. An extensive evaluation of Ascopain is provided by comparing the simulation results, first to experts' predictions, and second, to experimental results of sensory evaluation of mixed dough properties. The good matching level proves the accuracy and the robustness of the expert-system and, overall, its ability to implement a reasoning on the influences of process conditions to predict actual dough properties, starting from ingredient characteristics.

Dynamic magnetic resonance microscopy of flour dough fermentation.

Magnetic resonance microscopy was carried out at 9.4 T with a voxel volume of 117 x 117 x 500 microm(3) and temporal resolution was adjusted to 8.5 min for a dynamic follow-up of bread dough fermentation during 2 h at a constant temperature of 30 degrees C. An image analysis procedure based on gray levels mathematical morphology routines was performed to assess bubble distribution and cell wall thickness inside the imaged bread dough. The evolution of the extracted curves allows one to characterize quantitatively the amount of bubbles and their growth. Using this procedure, different bread doughs were examined to determine the impact of dough composition on the structure modification during fermentation.