To evaluate the storage stability of flours from Rhynchophorus phoenicis and Imbrasia truncata larvae obtained by freeze-drying, their moisture adsorption isotherms have been determined at 20, 30 and 40 °C and their thermal properties explored by differential scanning calorimetry (DSC). DSC evidenced reversible transitions attributed to lipid melting/crystallization between − 60 and 90 °C. The GAB model was chosen to model adsorption isotherms. It evidenced 2 and 3 water compartments in R. phoenicis and I. truncata flours, respectively. Adsorption isotherm of R. phoenicis is type III at 20 and 30 °C, while that of I. truncata is type II at 20, 30 and 40 °C. GAB model also allowed calculating flour monolayer moisture contents (Mo ≤ 5.6 g/100 g dry matter (DM)). Net isosteric heat (qst) was evaluated. qst decreases with increase of water content and was higher for the flour of I. truncata larvae (from 8571 to 503 J/mol; 2,5 to 20 g/100 g DM) than that of R. phoenicis larvae (from 1750 to 124 J/mol; 5 to 30 g/100 g DM). Finally, the maximum storage times of the insect flours under typical packaging and storage conditions were estimated according to the Heiss and Eichner model. Highest for the flour of I. truncata, qst remained however moderate indicating that the insects can be dried without important energy supply. The estimated storage time of R. phoenicis larvae and I. truncata flours (3 g/100 g DM), stored at 20 °C in polyethylene bags, could reach 263 (8 months and 19 days) and 116 days (3 months and 24 days), respectively. These results provide valuable insights into the stability and potential applications insect flour in the food processing industry. This information could help in determining suitable packaging methods and storage conditions to maintain the quality and shelf life of products containing these flours to set safety and quality standards for such products.

The aim is to replace mineral waxes with vegetable fats as an organogel for candle manufacturing while keeping the same texture. The physico-chemical characteristics of renewable vegetable raw materials differ from those of mineral waxes and consequently the structure of the blends in which they are used is modified. Their properties are measured at different scales using FT-IR analysis, polarized light microscopy, calorimetry and rheology. The addition of 12-hydroxystearic acid (12-HSA) promotes the creation of hydrogen bonds within the rapeseed oil that makes possible its incorporation to form an organogel. The addition of 12-HSA also results in a modification of the crystal microstructure of blends made of 90% vegetable raw materials. Hence, the crystal lattice is denser and the crystal size is reduced compared to blends including mineral waxes. At a macroscopic scale, the physical properties of blends with 12-HSA are modified compared to the reference one, mainly made of mineral waxes. A modification of crystallization and melting temperatures as measured by differential scanning calorimetry as well as the rheological behavior and the hardness assessed by penetrometer are observed. This results in a higher stability against exudation for blends with a high content of 12-HSA. Mineral waxes can thus be substituted in the formulation of candles by renewable materials for the use of organogel, via the incorporation of an organogelator, 12-HSA.

Manganese is a chemical element used as a colourizer in glass industry since antiquity. Combined with iron, manganese often plays the role of a decolourizer leading to uncoloured glasses used to represent hands and faces in medieval stained glass windows. A series of medieval-like glasses has been synthesized in order to relate the colouration of glasses with the conditions of synthesis (temperature, atmosphere, glass composition). Optical absorption spectra in the UV-Vis-NIR range have been measured to follow and characterize the changes in colouration. For a given temperature, the addition of Mn in a Fe-rich glass composition implies a decrease of the concentration in Fe(2+)and an increase of the concentration in Fe3+ as compared to the Mn-free glass composition. The uncoloured glass composition is obtained for different contents of Mn when melting temperature varies. These results might help deciphering the complexity of colour making in ancient times.

This study concerns the mixing under gas pressure of a cake batter free from baking powder. Mixing the batter under pressure has been considered as an alternative to baking powder with the aim of forcing the aeration of the batter and possibly the solubilization of gas in the liquid phase of the batter. A prototype mixer was used with air, CO2 and N2 applied with gauge pressures of 0.3 and 0.5 bar. CO2 pressure of 0.3 and 0.5 bar yielded the best results in terms of specific volume of cake with 2.5 mL/g which was 89% of the specific volume of control cake with baking powders. The improvement was attributed to the solubilization of CO2 in the liquid phase of the batter, which was evidenced by a decrease in the pH of the batter.

This work is part of a study aiming to design a high-throughput foaming microsystem. The main focused field of application is the food industry. With the objective of improving the design of the microdevice, the effects of the geometry and the nature of the liquid base are presently investigated through visualizations of the flow typology of bubbles trains, aiming to expand the knowledge on key parameters that lead to an improved gas breakup. The tested set of conditions is not encountered in traditional microfluidics systems: i.e., throughputs up to 19 L·h−1 for the liquid phase, process velocities around 20 m·s−1 and flow of complex fluids. The behavior of solutions based on xanthan gum (XG) and whey proteins (WPI) is compared to that of solutions containing one of these ingredients or other ones (caseinates, glycerol). The structural and end-used properties of the final foams, namely the bubble diameter and rheological behavior, are evaluated. The incorporation of XG induces bubble shape stabilization even at the highest shear rates (~105 s−1) encountered in the mixing channel. “Controlled” interfacial breakup by tip-streaming or binary breakup are only observed with the WPI/XG biopolymers. This study indubitably highlights the essential role of the process/formulation interaction in the development of structural and functional properties of food foams when using microfluidics at high throughput.

AbstractThe viscosities of solutions formulated with xanthan gum and xanthan gum with whey protein isolates are experimentally characterized and modeled over a wide range of shear rates [10−3to 105s−1]. As shown by numerous studies [1, 2], the generation of vortices in the cone-plate geometry is making viscosity measurements beyond a certain shear rate unreliable. In the present work, an innovative technique, based on microfluidics and developed by the company Formulaction, has been employed to extend to high shear rates, the viscosity flow curve obtained with a rotational rheometer. The main highlights of this study are firstly, to propose a scaling law for the inertial transition in the cone-plate geometry for different diameters and angles through the determination of the maximum shear rate at which one can expect a true viscosity value. Secondly, the high shear rate measurements allow the determination of the second Newtonian plateau for these solutions thanks to the Williams-Carreau model. An attempt for the second plateau modeling is proposed following the concept of an intrinsic viscosity in the high shear equilibrium. In the same way, other fitted parameters from the Williams-Carreau law are modeled as a function of the polymer concentration. This procedure allows to provide a predictive model for the rheological behavior of xanthan gum-based solutions used in high shear processes like high pressure homogenization, emulsification, foaming, microfluidics, etc in food, pharmaceutical or cosmetics applications.

This work is focused on the development of a compact continuous process for the production of food foams with controlled properties. Cross-shaped channels of infra millimeter size are used and the two-phase flow pattern is analyzed in order to identify the mechanisms of bubble deformation and breakup at very high velocities [similar to 2-20 m s(-1)]. Two different microcrochannel designs are used, differing by the presence of an abrupt expansion in one of the devices. Similar breakup mechanisms are observed in both devices in the cross-shaped channels and an additional local elongational flow was identified in the expansion. The expansion was found to intensify bubble breakup. All the experiments are carried out with the same gas content and the same liquid mix prepared from biosourced molecules (xanthan gum and whey proteins). A dimensional analysis is proposed in order to model the diameter of bubbles at the moment of their formation. (C) 2019 Elsevier Ltd. All rights reserved.

The context of this work is to explore the possibility of making bio-sourced foams at high throughput in microsystems. A fundamental element for the development of new technologies based on biphasic flows in microchannels is a good characterization and knowledge of hydrodynamics. In this contribution, cross slot microsystems are tested as a promoter for the formation of train of bubbles in aqueous solutions of xanthan gum. A flow chart is proposed to present the conditions allowing a dispersed flow regime; i.e. the conditions guaranteeing the complete incorporation of the gas into the liquid phase (no gas pocket) and then the control of the void fraction. The foaming is studied under potential industrial conditions, i.e. operating with liquid flow rates up to 24 L/h. High speed imaging within the channels reveals that the mechanism of formation of bubbles is related to flow focusing. Bubbles are generated alternatively from each of the two opposite gas inlets. Using whey protein isolate to enhance foaming points out that the bubble size may be reduced along a long channel by tip streaming. The effect of the modulation of the viscosity of the liquid base (xanthan gum content) is also discussed.

An innovative methodology based on non-destructive observation by using harmonic generation microscopy is proposed for detection and location of starch granules and oil in a fried starchy matrix and topography analysis of food products. Specific fluorescent probes were used to label the main biochemical components of the starchy fried matrix, namely starch and oil. Fluorescence of starch and oil respectively stained with Safranin O and Nile red was observed from non-linear microscopy. By using sequential scanning and specific emission filters, it was possible to merge fluorescence and harmonic generation signals. Second harmonic generation (SHG) generated by starch granules was superposed with safranin fluorescence, whereas third harmonic generation (THG), not restricted to the superposition with Nile red fluorescent signal, was used to investigate the topography of the fried product. By these experiments, starch granule mapping and topography of the starchy fried product were obtained without any destructive preparation of the sample. This label-free approach using harmonic generation microscopy is a very promising methodology for microstructure investigation of a large panel of starchy food products.

The impact of nanoparticulated whey protein aggregates on the texture of fat-free set-type yoghurts was investigated. Monodisperse (MFA) and polydisperse (PFA) fractal aggregates obtained from heated whey protein isolate (WPI) were added to skimmed milk for yoghurt manufacture at four different concentrations (0.2%–1.5%, w/w). The impact of the concentration and the polydispersity of the aggregates on fat-free set-type yoghurts were studied by instrumental measurements (rheology, penetrometry, syneresis and microscopy) and sensory analysis. Yoghurt gel strength and firmness increased with the concentration of WPI, MFA and PFA. However, yoghurts enriched with PFA clearly differed from the yoghurts enriched with WPI. Indeed, yoghurts enriched with PFA were characterised by a weak gel, a low firmness and a low-density of the protein network. Sensory analysis confirmed the results obtained by instrumental measurements. The whey protein aggregates studied are thus promising tools to modulate fat-free yoghurt texture while using milk-derived ingredients.

The work described in this paper investigates the behaviour of paraffin material under pressure. Compressibility has been widely described in the literature but the behaviour of paraffin materials under compression is not well known. This study intends to highlight the influence of particle size and shape of paraffin material on their compressibility. This is of major interest for the candle industry. Indeed, one of the main forming processes is pressing of paraffin powder. For this purpose, particle size and shape were characterized according to a digital image analysis approach and compressibility was measured by compressing the paraffin into a mould using a texture analyser. Results show that compression at low pressure (0.2 MPa) is governed by the average circularity and mean diameter of the paraffin particles while compression at higher pressure seems to be governed by the uniformity of the dispersion of particle size. It helps the selection of the particle size and shape category to be used to promote candles formation and production. This study also provides a tool to assess plasticity of paraffin by using the mean yield pressure.

The mechanical characteristics of a paraffin–vegetable oil material and the compressive behavior of the powder stemming from this material were used to estimate the resistance of the compressed samples. The compressive behavior of powders under the low pressure range (1–2MPa) applied in the candle industry was investigated in order to predict the tensile strength of the compressed samples. Compressive behavior was evaluated under lab conditions similar to those practiced in the candle industry. Compressive behavior of the powders, which represents the resistance of the particles to rearrangement during the packing step, Kp (30.98±1.20kPa of the mixture M1), was positively correlated to tensile strength of the compressed samples, σt (175.46±3.61kPa of mixture M1). Tensile strength of the compacts was also related to the mechanical properties of the raw material: high tensile strength was linked to low ductility (γMR), high mechanical strength (RMR) and high Young's modulus (E) of the material. Formulation—particularly the presence of a lubricant of mineral (0.52%) and vegetable (44.1%) origin in mixture M5—was found to strongly influence the mechanical properties of the compressed samples (σt=115.52±2.42kPa).

The changes in physicochemical properties of standard maize starch (SMS) by three hydrothermal treatments; DV-HMT (Direct Vapor-Heat Moisture Treatment), RP-HMT (Reduced Pressurized-Heat Moisture Treatment) and DIC (instantaneous controlled pressure drop) were investigated at different processing conditions; steam pressure (SP) varied from 1 to 3 bar during 20 min. Starch was steamed by direct contact, whose interest was to intensify the heat transfer phenomenon but also the water transfer. The physicochemical changes of SMS depended on process conditions and their extent followed this order: DIC > RP-HMT > DV-HMT. All treatments significantly increased gelatinization temperatures and decreased the enthalpies, confirmed by loss of granules birefringence. From 2 bar, the crystalline structure changed from A-type to Vh-type, revealing formation of amylose-lipid complexes during steaming. The results clearly showed that the particle size distribution depends on the melting extent of crystalline structure during treatment. At severe processing conditions the melted fraction increased and more complex aggregates of different sizes have been formed.