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Background Ultrasound-assisted extraction of the intermediate product from the mechanical expression of hemp (Cannabis sativa L.) seed oil was investigated to improve the overall expression yield without compromising oil quality. Complementary ultrasound technology was used as an out-of-line treatment carried out at 20 kHz frequency and optimized with respect to amplitude (80 and 152 μm), sonication time (2, 10, 20 min) and to the hemp paste properties, in particular its particle size and hydration, which drive the compressibility of the press cake. Results Under the conditions evaluated, the optimal ultrasound treatment was found to be the one applied on the hydrated press cake for 2 min at 152 μm, which resulted in an oil yield of 13.4%, with an increase in extraction efficiency equal to 73% with respect to the control (untreated press cake). Sonication had a positive effect on the press cake texture and on the extracted oil antioxidant activity. Soaked samples treated for 2 min at 152 μm yielded the lowest hardness. Oil recovered from soaked samples treated at 80 μm and 152 μm ultrasound for 2 min had the highest antioxidant capacity. Conclusions The technological results gathered in the present investigation are preliminary to the design and engineering of scaled-up equipment that combines the mechanical screw expression and the in-line ultrasound unit. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

This study investigates the separate effect of sonication (US, carried out for 5 and 15 min) and thermal treatment (90 °C for 5 min) on nutritional and technological properties of tomato paste. US treatments did not affect the colour parameters and decreased the level of total acidity. Ascorbic acid content was slightly reduced after 5 min US but halved by pasteurization, while total carotenoids (TCC) and lycopene (LC) decreased in non-pasteurized samples after 15 min US. Neither the TCC nor the LC significantly changed in US-pasteurized samples if compared to controls. Microscopic analyses suggested a possible increased bioaccessibility of lycopene in US treated samples due to an enhancement of free lycopene clusters. Viscosity decreased as a consequence of thermal stress, although sonication contributed as well. The present findings suggest that 5 min sonication before pasteurization can enhance the nutritional characteristics of tomato paste, besides improving its texture.

A fundamental understanding of plant cell wall rheology is essential in view of the formulation engineering of plant-based foods/ingredients. In this paper, by means of oscillatory measurements, we study the rheological behavior of water suspensions of cell wall polysaccharidic supramolecular assemblies, which are extracted with selective solvents precipitation method from apple flesh. Once rehydrated with water, they behave as gel like materials, as it results from the mechanical spectra, with the elastic modulus Gʹ higher than Gʺ within the frequency range considered. Interestingly, amplitude and time sweep measurements show reversible stress softening and stress recovery after high shear strain. The observed behavior of the cell wall molecular assemblies resembles closely to that of colloidal gels, which also display shear-thinning rheological properties and a complex aging response. In this regard, creep measurements indicate history-dependent effects, which are interpreted in terms of aging phenomena, similar to those existing in glassy systems. The self-healing behavior and the non-equilibrium nature we observed allow customized modifications during processing and storage to obtain new structural states and rheology. Such changes in the microstructure might be relevant for product and process performance.

Cell walls in plants are polymeric composite systems, which determine the textural attributes of vegetal tissue. In this paper, results are presented on the investigation on the structural properties of cell wall materials (CWMs), intended for use as structuring materials in manufactured products. Specifically, CWMs were extracted from fresh and ripened minimally processed Valerianella locusta Laterr. At the tissue level, the structural resilience inferred by CWM varies with storage time, as it was evaluated both quantifying the membrane degradation and the mechanical characteristics of salads texture wilting. Mechanical spectra of the rehydrated CWM gel show the increase of the elastic character with the salad aging time. Stress relaxation spectra deduced from rheological study on water suspension of the extracted cell wall polysaccharides, showed fast and slow relaxation modes, whose ratio changed with the aging of the salad tissue. The use of unrefined cell wall materials (CWMs) in food formulations may infer naturalness to food offerings and this paper shows how CWM extraction from salad that underwent different time storage histories, can provide modulation of the functional properties of these structures in final manufactured products.

Texture and mesostructure of packaged fresh-cut ‘Fuji’ apple slices were studied during 30 days storage at 4, 10 and 20 °C. Instrumental mechanical–acoustic texture evaluations were carried out, and cell wall materials were isolated from the flesh tissue by means of an ethanol and methanol–chloroform solvents extraction procedure. The emphasis was on relating the macroscopic loss of fresh texture characteristics to the changes in the rheological properties occurring to the structuring elements of the cell wall materials (CWMs). The rheology of the reconstituted CWM water dispersion was evaluated by means of oscillatory dynamic testing, and viscoelastic data were interpreted according to the ‘weak-gel model’ theory. The dynamics of the flowing components at the mesoscale structural level was related to the texture softening, which yields decrease in firmness and rigidity parameters, and an attenuation of the acoustic emission (fewer acoustic peaks and lower sound pressure level), as it was measured in the combined acoustic–mechanical test. The kinetic reaction rate values are presented. Softening of apple flesh is accompanied by slight cleavage of molecular assemblies and a loss in cell adhesion, mediated by the increase in assemblies’ water uptake. The ability to handle the relationship between the sounds produced during flesh crushing and the structure of the cellular tissue would assist breeders and geneticists in the selection and control of the apple crispness, or would support technologists in preventing postharvest softening during storage and retail.

The present paper describes preliminary results on the development of a batch lab-scale co-extrusion device for the production of alginate beads as carrier for hydrophilic compounds. A dual jet of liquid core (aqueous solution of glucose or vitamin B12 or olive oil) and liquid shell material (aqueous solution of alginates differing for guluronic to mannuronic ratio) was pumped through concentric extrusion nozzles and droplets were formed by means of a rotating fluid jet cutter. The shell of the bead was then hardened in the hardening bath containing a calcium chloride solution. Optimization of the co-extrusion plant accounts for the management of the operative conditions within the hardening unit (incubation time, molarity of the gelling agent), and for the control of the surface-tension-driven breakup of laminar jets which was managed by varying the jet cutter - hardening unit distance. Beads enriched in vitamin B12, that were formed according to the best plant set-up, were tested for the bioactive release when stressed under thermal conditions simulating typical dairy products processes. Cyanocobalamin was retained at all.

Surface aggregating soy protein-pectin solutions are used in the production of biodegradable films intended for food packaging applications. Structural properties of the surface biopolymer network influence the engineering properties of the films, such as permeability and mechanical strength. Soy protein isolates (SPI) – high methoxyl pectin (HMP) films that develop at the air–water interface were therefore investigated by a combined interface rheological and ellipsometric approach. The behavior of pure SPI interfacial layer is that of a light cross-linked polymer network with a small regime of linear viscoelasticity response. Since SPI progressively accumulate at the air–water interface, higher protein concentration in the solution does not lead automatically to higher surface coverage but due to restricted unfolding of the proteins to weaker and fluid-like films. The rheological behavior of composite SPI–HMP solutions at the air–water interface shows that the HMP addition increases the elastic interfacial modulus. The stabilizing effect in presence of the polysaccharide is attributed to a protein–polysaccharide complex formation at the interface.

The espresso coffee beverage is a polyphasic colloidal system, in which the liquid phase is topped by a wet foam of tiny sphere-shaped gas bubbles. Each sphere is surrounded by a liquid film (lamellae) that isolates it from its neighbours and that hosts biopolymers and natural surfactants. Foaming biopolymers of coffee (total fraction and its sub-fractions: proteins/melanoidins fraction and polysaccharides fraction) were extracted from defatted and raw, commercially roasted ground coffee. In order to study the viscoelastic behaviour of the surface-adsorbed layer, all the extracted fractions were analyzed using a commercial interfacial rheometer CIR 100 operating in time sweep mode. The growth of the interfacial elasticity of the lamella implicitly contains all the information about the molecular interaction at the foam air/liquid interface. These interactions are described to be responsible for the foam stabilization. Results indicate that the kinetics of the film formation is mediated by the polysaccharide component and that the protein/melanoidin component of the coffee foaming fraction exhibits the highest viscoelastic interfacial properties. Lipids play a major role in the interfacial film formation due to their interaction with protein-like macromolecules, the melanoidins. A correlation was established between air/water interface properties of the foaming systems and the respective foam volumes evaluated by means of the image analysis. A new mathematical description of surface viscoelastic phenomena, covering the terms of transport of surfactant biopolymers to the interface and describing the coagulation of particles here taking place, is proposed. The suggested equation overcomes the Warburton model, taking into account the complexity of real food systems as in the case of the espresso coffee beverage.

In this work, a novel injectable biocomposite hydrogel is produced by internal gelation, using pectin as organic matrix and hydroxyapatite either as crosslinking agent and inorganic reinforcement. Tunable gelling kinetics and rheological properties are obtained varying the hydrogels' composition, with the final aim of developing systems for cell immobilization. The reversibility by dissolution of pectin–hydroxyapatite hydrogels is achieved with saline solutions, to possibly accelerate the release of the cells or active agents immobilized. Texture analysis confirms the possibility of extruding the biocomposites from needles with diameters from 20 G to 30 G, indicating that they can be implanted with minimally-invasive approaches, minimizing the pain during injection and the side effects of the open surgery. L929 fibroblasts entrapped in the hydrogels survive to the immobilization procedure and exhibit high cell viability. On the overall, these systems result to be suitable supports for the immobilization of cells for tissue regeneration applications.

This paper validates a simultaneous heat and mass transfer model proposed to describe the discontinuous biscuit baking process. The mathematical model includes the moving evaporation front and the development of the crust observed during the baking process. The problem is solved over a two-dimensional geometry using the finite element method. Thermo-physical properties were computed by means of continuous functions. Variations in temperature and water content during baking were predicted with high to discrete accuracy using this model.

International audience; The rheological behaviour of biopolymer gels is commonly investigated by means of small amplitude oscillatory measurements. This consolidated approach was used in the present paper to characterize the influence of ionic strength and temperature on the gelation of commercial low-methoxyl pectin (LMP) (DE = 22.5%). The main results showed that the sol/gel transition is very sensitive to the ionic strength of the medium, while the viscoelastic properties of the gel structure, developed over 8 h cure test, were retained up to 60 degrees C. The soft material under study displays the typical theological behaviour of a solid-like material, in good agreement with results previously reported in the literature. It is known that the best time or frequency window useful to explore in dynamic mode the viscolelastic behaviour of complex materials such as a gel would range over several decades of frequency. The possibility to extend the frequency domain of the dynamic tests in the region o! f the lower frequencies (10(-5)-10(2) rad s(-1)) was therefore investigated by matching information coming from dynamic and transient theological tests and converting data from time domain into frequency domain throughout the discrete retardation spectrum of the material, as described by Kaschta [Kaschta, J., & Schwarzl, F. R. (1994). Calculation of discrete retardation spectra from creep data - I. Method. Rheologica Acta, 33, 517-529.]. Results show that around 10(-5) rad s(-1) the mechanical spectrum of LMP gel approaches the beginning of the terminal region, where the theological behaviour is mainly dominated by viscous flow, thus indicating a liquid-like character of a material and thus accounting for the large proportion of solvent (higher than 98%) contained in the network.

Alginate is a natural biopolymer that forms, in the presence of divalent cations, ionic-bound gels typifying a large class of biological gels stabilized by non-covalent cross-links, and displaying a consistent restructuring kinetics. We investigate the kinetics of formation and aging of alginate gels by slow permeation of a curing CaCl2 agent by means of photon correlation imaging, a novel optical technique that allows obtaining the microscopic dynamics of the sample, while retaining at the same time the spatial resolution of imaging techniques. Specifically, the gelling kinetics displays a peculiar non-diffusive behavior, and the subsequent restructuring of the gel structure shares several features in common with the aging of colloidal gels, in particular for what concerns the occurrence of heterogeneous dynamics effects. A comparative analysis of the gel macroscopic mechanical properties at different aging stages further highlights distinctive effects arising from the non-permanent nature of the bonds.