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Structures and phenomena occurring during the heat treatment of cornstarch. The structure of cornstarch and the modifications induced during the heat treatments are presented in this review. Current knowledge indicate that the starch granules are semi-crystalline entities composed mainly by amylose and amylopectin, undergoing deep reorganizations during the heat treatments. Gelatinization, glass transitions, relaxation phenomena, retrogradation and the formation of amylose-lipids complexes are the major phenomena involved in these reorganisations, and are the basis of changes of the techno-functional properties of cornstarch-based products during their heat treatment. La rhizosphère est le volume du sol situé au voisinage immédiat des racines des plantes et qui se caractérise par la présence d'exsudats racinaires (rhizodépôts). Ces exsudats sont utilisés par la microflore endémique en tant que signaux chimiques en plus d'être un substrat nutritif disponible pour la croissance et le développement de ces microorganismes dans la rhizosphère. Certaines de ces bactéries du sol, appelées PGPRs (Plant Growth Promoting Rhizobacteria), sont capables de coloniser les racines ou bien encore la rhizosphère, mais à la différence des autres bactéries rhizosphériques elles ont, en retour, un effet bénéfique sur la plante. Cet effet bénéfique peut être direct, ou indirect. La promotion directe de la croissance est le résultat du pouvoir d'acquisition des nutriments ou de la stimulation des hormones de la plante. D'autres mécanismes indirects, mais le plus souvent liés à la croissance des plantes, sont impliqués dans la réduction/suppression des pathogènes des plantes. Cet article décrit les différents mécanismes mis en jeu par les PGPRs dans leur environnement naturel pour influencer favorablement la croissance et la santé des plantes.

Comparison of two drying models applied to corn drying in fluidized bed. In this article, two predictive models of the temperature and water content of corn grains during their drying in a fluidized bed are compared. The first model is a simplified one, where the physical phenomena implied in the process are not described. It can be solved using freewares available on Internet. The second is a more complex model, based on the basic physical laws governing the phenomena of heat and mass transfer within the product. It requires the use of commercial finite element software to solve it. The two models are parameterized with four dryings where the temperature remains constant during the process, then validated on dryings with variable temperature and an intermittent drying. The two models are able to describe with an acceptable precision the evolutions of water content during continuous dryings, and to predict the evolutions of water content during dryings with variable temperature and the intermittent drying. The dynamic model is however not able to describe the evolution of the grains temperature during dryings at variable temperature with a precision lower than one degree Celsius. If this precision is sufficient, the use of the dynamic model will reduce considerably the costs in time and license of software for the modeling of the corn drying in a fluidized bed.

Prebiotic isomaltooligosaccharide (IMO) preparations contain α-D-glucooligosaccharides and their structure is the key factor for their prebiotic potential. The transglucosylation selectivity is known to depend on the enzyme specificity and moreover, maltose and α-glucooligosaccharides can actually act as both glucosyl donor and acceptor in the reaction. Thus, two commercial enzymes, a glucosyltransferase and an α-glucosidase, were tested alone and in combination on pure maltose to study their specificities and the IMO profile obtained. The reactions were monitored using a step-forward AEC-PAD analytical method which permitted to detect and resolve new unknown IMO. Structural determination of unknown IMO was attempted using their retention times and relative abundance. As a general rule, the α-glucosidase has a more expressed hydrolyzing activity leading to products containing less residual digestible α-(1-4) linkages such as isomaltose, isomaltotriose, isomaltotetraose, kojibiose and nigerose while the glucosyltransferase produces important amount of panose. Finally, the combination of the two enzymes leaded to an intermediate IMO profile. IMO syrups composition was thus proved to be dependant on the specificity of the transglucosylating enzyme so that products profiles can be designed using different enzymes and in different proportion.

Buttermilk, the by-product from butter manufacture, is low cost and available in large quantities but has been considered for many years as invaluable. However, over the last two decades it has gained considerable attention due to its specific composition in proteins and polar lipids from the milk fat globule membrane (MFGM). The aim of this review is to take stock of current buttermilk knowledge. Firstly, the milk fat globule membrane composition and structure are described. Secondly, buttermilk and its associated products are defined according to the milk fat making process. Structure and mean composition of these products are summarized from recent dairy research data and related to technological properties, especially the emulsifying properties provided by MFGM components. Finally, new applications are presented, leading to promising valorizations of buttermilk and its derivate products.

Enzymic hydrolysis of residual fat with a sn 1,3 specific lipase improves the emulsifying and foaming capacities of sweet whey and whey protein concentrate (WPC). Lipase-treated sweet whey and WPC show low equilibrium surface tension, high compressibility modulus of films at the water surface and a high adsorption rate to the air-water interface. Hydrolysis converts the triglycerides into strong surface-active mono- and diglycerides. This improves the capability and steadiness of the foam and the emulsion. These emulsions and foams are more shelf-stable than those of the native products.

The gelling properties of whey protein concentrate after residual fat hydrolysis are described.

In order to determine the importance of cis or trans unsaturations from a technological point of view, the study of the structural and thermal properties of monoacid triglycerides: tristearin (SSS), triolein (OOO) and trielaidin (EEE) has been undertaken. X-ray powder diffraction and differential scanning calorimetry are useful tools to elucidate the physicochemical properties of such compounds. In this work polymorphism, kinetics of polymorphism and intersolubility have been investigated. From a structural point of view, we have shown that, according to the polymorphic form, the conformational properties of EEE are similar to those of the corresponding saturated molecule SSS or to those of the cis unsaturated analogue OOO. The study of the intersolubility behavior of these three compounds has shown a different affinity of the cis and trans unsaturated molecules vs the completely saturated one. By the same method, we have observed that trans unsaturated hydrocarbon chains cocrystallize with both cis-unsaturated (OOO) and totally saturated hydrocarbon chains (SSS); the trans double bond of EEE can adapt to the two kinds of lattices. The study of the kinetics of polymorphism has shown that 5% of OOO or EEE accelerate the β′→β transition of SSS, while the reason for the two phenomena is quite different. The adaptation of EEE to cis-unsaturated and to saturated hydrocarbon chains shown in the structural and intersolubility behavior analyses also appears in the kinetic study, after adjunction of 5% of OOO into EEE. All the results confirm that, from structural and thermal points of view, EEE has an intermediate behavior between SSS and OOO. [ABSTRACT FROM AUTHOR]