0000000000095530
AUTHOR
Gaëlle Roudaut
Question on ipm: A case study on lemon juice
International audience; In food product development, using consumers to obtain ideal products is becoming more frequent inrecent years. Despite being an economical way of optimizing products, relying on consumers is,however, not yet widely accepted in the sensory community. The main objectives of this study were toevaluate (1) whether the stability of ideal intensities and ideal products could be improved byproviding a frame of references when consumers perform the Ideal Profile Method (IPM) and (2) theeffect of the order of the questions on consumers‘ responses.In the present study, sixty participants conducted two tasks: (1) rating the perceived and idealintensities of attributes and (2) …
Glass Transition and Food Technology: A Critical Appraisal
ABSTRACT: Most low water content or frozen food products are partly or fully amorphous. This review will discuss the extent to which it is possible to understand and predict their behavior during processing and storage, on the basis of glass transition temperature values (Tg) and phenomena related to glass transition. Two main conclusions are provisionally proposed. Firstly, glass transition cannot be considered as an absolute threshold for molecular mobility. Transport of water and other small molecules takes place even in the glassy state at a significant rate, resulting in effective exchange of water in multi-domains foods or sensitivity to oxidation of encapsulated materials. Texture pr…
Production of spray-dried proanthocyanidin-rich cinnamon (Cinnamomum zeylanicum) extract as a potential functional ingredient: Improvement of stability, sensory aspects and technological properties
International audience; Cinnamon proanthocyanidins present important biological properties. However, these molecules are unstable and possess an astringent taste, which can make their ingestion difficult. In this context, entrapment by spray-drying technology may be used to produce a concentrated extract with improved stability and reduced astringency. Thus, this work aimed to prepare spray-dried microparticles loaded with a proanthocyanidin-rich cinnamon (Cinnamomum zeylanicum) extract (PRCE), immobilized in a maltodextrin matrix. Freeze-dried samples of the extract (without the carrier) were also prepared for comparison. The particles were characterized for moisture content, water activit…
Influence of fat nature on flavour release
National audience
Positronium as a probe in natural polymers: decomposition in starch
Ortho-positronium (o-Ps) is used as a probe in positron annihilation lifetime spectroscopy (PALS) experiments, to characterise the behaviour of free volumes in natural starch samples, as a function of temperature (T). Up to about 540 K, the o-Ps intensity, I(3), remains constant at 26.2% while its lifetime, tau(3), is found to increase linearly. Both parameters undergo a decrease above this T, due to the onset of decomposition, which results in a shrinking of the sample pellets. The results indicate that the glass transition temperature should be above 501 K. Data from thermal gravimetry analysis (TGA) measurements are well described by supposing a first order process for the survival proba…
Water and temperature contribution to the structuration of starch matrices in the presence of flavour.
The effect of hydrothermal treatments and flavours addition on starch structure and its physical properties were studied. Native wheat starch was treated at 2 different hydrations (water-starch ratios: 50/50 and 80/20 g w/w) and temperatures (65 and 85 °C) in the presence of flavours (ethyl hexanoate and 2-hexanone). The freshly prepared samples were subjected to DSC and flavour analysis. Flavour inclusion complex could not be detected by DSC, however the result of flavour analysis proved that there were flavours interactions with starch. Both ethyl hexanoate and 2-hexanone interacted with starch at similar rates. The highest flavour loss was found in the samples at high hydration and heate…
Applications of spray-drying in microencapsulation of food ingredients: An overview
International audience; Spray-drying process has been used for decades to encapsulate food ingredients such as flavors, lipids, and carotenoids. During this drying process, the evaporation of solvent, that is most often water, is rapid and the entrapment of the interest compound occurs quasi-instantaneously. This required property imposes a strict screening of the encapsulating materials to be used in addition to an optimization of the operating conditions. Likewise, if the encapsulated compound is of hydrophobic nature, the stability of the feed emulsion before drying should also be considered. Thus, spray-drying microencapsulation process must rather be considered as an art than a science…
Characterization of a sucrose/starch matrix through positron annihilation lifetime spectroscopy: unravelling the decomposition and glass transition processes
The triplet state of positronium, o-Ps, is used as a probe to characterize a starch-20% w/w sucrose matrix as a function of temperature (T). A two-step decomposition (of sucrose, and then starch) starts at 440 K as shown by a decrease in the o-Ps intensity (I(3)) and lifetime (τ(3)), the latter also disclosing the occurrence of a glass transition. Upon sucrose decomposition, the matrix acquires properties (reduced size and density of nanoholes) that are different from those of pure starch. A model is successfully established, describing the variations of both I(3) and τ(3) with T and yields a glass transition temperature, T(g) = (446 ± 2) K, in spite of the concomitant sucrose decomposition…
Crispness: a critical review on sensory and material science approaches
International audience; Many texture studies have been published on crispness because of the great interest of consumers towards crispy foods. This work reviews the existing literature on the topic, and especially the different approaches, instrumental and sensory, applied to study crispness. These studies result in a wide range of data but, because crispness is not a clearly defined sensory attribute, the conclusions that can be drawn from these studies should be carefully examined. The physical basis for crispness are discussed and the role of structure, hydration and ingredients on crispness and its stability are presented.
Water sorption isotherms of molecularly imprinted polymers. Relation between water binding and iprodione binding capacity
International audience; Molecularly imprinted polymers are often used in aqueous medium in order to recognize specifically a target molecule. The molecular recognition is usually based on hydrogen bonding. In this case, water molecule presents a serious competition towards the target molecule. In this study, the water sorption by molecularly imprinted polymers was studied in aqueous medium. The molecularly imprinted polymers were specific for iprodione fungicide and were prepared using a 24 full factorial experimental design. They were synthesized using EGDMA or TRIM as crosslinker, methacrylamide or styrene as functional monomer and using bulk or precipitation polymerization. The water sor…
Impact of sucrose and water contents on macroscopic structure and stability of cereal based products : Thermodynamic versus dynamic
No abstract
Influence of water, temperature and sucrose on dynamics in glassy starch-based products studied by low field 1H NMR
Abstract In this study, the influence of both water content and temperature on the mobility of glassy starch-based matrices (starch alone or mixed with sucrose at the ratio 0% to 20% db) were studied using time domain 1 H NMR. The 2nd moment M 2 , and transversal relaxation time T 2 ∗ were used to study the molecular mobility of the rigid and mobile fraction of the NMR signal, respectively. The molecular mobility of the protons constituting the samples increased with water content (up to 13% wb) at all temperatures. For a given water content, both rigid and mobile protons exhibited a lower mobility in the presence of sucrose. When mobility characteristic parameters, M 2 second moment values…
Relaxations Below Glass Transition Temperature in Bread and Its Components
ABSTRACT Dry glassy bread, cooked gluten, and gelatinized wheat starch-sucrose mixtures were prepared. Dielectric properties were studied as a function of temperature at different frequencies ranging from 100 to 1,000 kHz. Both bread and starch samples exhibited a tan δ peak at -53°C at 10 kHz, which is associated with a secondary relaxation characterized by an activation energy of 50 kJ/mol. The gluten sample did not show any relaxation in the temperature range studied. The magnitude of the relaxation peak was sensitive to the sucrose concentration of the starch sample. The higher the sucrose content, the greater the amplitude of the peak. Such an effect is attributed to a greater β-relaxa…
Characterization of palm sap harvested in Songkhla province, Southern Thailand
International audience; The purpose of this study was to characterise the quality of palm sap after harvested in Songkhla province, southern Thailand. Ten palm sap samples were analyzed. The results showed differed in physical and chemical quality among samples (P<0.05). The results showed range of L*, a* and b* values between 61.49 to 87.53, 1.46 to 3.52 and 12.41 to 19.31, respectively. The turbidity was ranged from 39.56% to 79.95%. The pH value was varied from 4.19 to 5.23, while total acidity was ranged from 0.27% to 0.93%. The total soluble solids ranged from 10.80 to 17.40OBrix. Total and reducing sugars were varied in a range of 10.36% to 16.94% and 0.88% to 3.56%, respectively. The…
Molecular Mobility in Glassy Bread: A Multispectroscopy Approach
ABSTRACT The molecular mobility in low-moisture (<9%, web) white bread was studied as a function of temperature using pulsed-proton nuclear magnetic resonance (NMR), and dielectric and dynamic mechanical spectroscopies. The water was mobile, even in glassy samples. Different processes below glass transition temperature (sub-Tg) were observed, and a relaxation map of the studied system was drawn. These results have been interpreted and extrapolated to suggest that the Tg is not a universal predictive parameter for the physical stability of glassy food.
Effect of water on glass transition in starch/sucrose matrices investigated through positron annihilation lifetime spectroscopy: a new approach
Glass transition is studied through positron annihilation lifetime spectroscopy (PALS) in maize starch matrices containing 10 (batch STS10) and 20 (STS20) w/w% sucrose, as a function of temperature (T) and water content (c(w)). To circumvent important losses of water upon heating while recording the PALS spectra, a new method is developed: instead of a series of measurements of τ(3), the triplet positronium lifetime, at different T, the latter is kept constant and the series relates to c(w), which is left to decrease at a constant rate. Similarly to the changes in τ(3) with T, the τ(3)vs. c(w) plots obtained show a smooth linear increase until a break, denoting the occurrence of glass trans…
Properties of spray-dried food flavours microencapsulated with two-layered membranes: Roles of interfacial interactions and water
International audience; Engineering the interface of oil-in-water emulsion droplets with biopolymers that modify its permeability could provide a novel technique to improve flavour retention in dry powders. The objective of this study was to determine if volatile compounds were more retained in dry emulsions stabilized by pea protein isolate (PPI)/pectin complex than that stabilized by PPI alone. The retention of ethyl esters during spray-drying increased with decreasing volatility of the encapsulated compound and ranged from 28% to 40%. The addition of pectin to feed emulsions was quite effective in markedly improving the retention of the three studied flavour compounds. In our previous wo…
New insights on the thermal analysis of low moisture composite foods.
Abstract Low moisture baked products were investigated with a view to characterising the effect of both formulation and humidity on their physical stability. At the end of the baking process, the samples were in the amorphous state as a result of starch gelatinization and sugar melting. Their thermal properties were analyzed with differential scanning calorimetry and their glass transitions were studied. The DSC thermograms were thoroughly studied through a Gaussian deconvolution of the first derivative of their heat flow. This approach evidenced a multiple phase behavior with different glass transitions in composite systems. They were associated with either a polymer-rich phase and/or a pl…
Changes in properties of palm sugar syrup produced by an open pan and a vacuum evaporator during storage
International audience; The aim of this study was to monitor the changes in the properties of palm sugar syrup produced by an open pan and a vacuum evaporator at 70°C and 80°C during storage under 4°C and room temperature (30°C) for 12 months at monthly intervals. During storage, Maillard reaction took place in samples stored under 4°C lower than those stored under 30°C. This was shown by lower a* values, intermediate browning products (IBP), browning intensity (BI) and HMF content, and higher L* values, fructose, glucose and free amino group contents during storage for 12 months. HMF, a possible mutagen formed by nonenzymatic browning during the heating and storage of sugar based products,…
Water in Dairy Products | Analysis and Measurement of Water Activity
Water activity of a system (aw) is a thermodynamic concept used to characterize the contained water. It has been considered, in spite of some limitations, as the most important parameter in food technology for the past 50 years. It can be measured by the ratio (p/p0) of the water vapor pressure in the atmosphere at equilibrium with the material to the saturated vapor pressure of pure water at the same temperature, or by the physical properties related to it (freezing point depression, mechanical/electrical properties). Although the physical/chemical mechanisms responsible for the depression of aw as compared to that of pure water are more or less identified, the expressions describing the r…