Mixed κ/ι-carrageenan - LM pectin gels: Relating the rheological and mechanical properties with the capacity for probiotic encapsulation.

The rheological and mechanical properties of mixed κ/ι-carrageenan - LM pectin gels were determined, and the potential of these gels for the formation of beads using the extrusion method and for the encapsulation of Lacticaseibacillus rhamnosus ATCC 53103 (LGG) was evaluated. Self-standing gels were obtained with all formulations evaluated. Carrageenan-rich gels, with carrageenan fraction (XC) ≥ 0.75, exhibited the highest storage modulus, but they were also brittle, while pectin-rich gels (XC ≤ 0.25) presented the highest hardness and cohesiveness. Pectin-rich formulations formed beads with the smallest initial diameter (2.40-2.45 mm), and the addition of carrageenan produced significantly more spherical beads compared to pure-pectin ones. As pectin-rich beads were the formulations that resisted simulated gastrointestinal conditions, these were selected for the encapsulation of LGG. These beads showed high encapsulation yields (87-96 %), and the percentage reduction of CFU/g during storage and simulated gastrointestinal conditions was not significantly different among formulations, the latter being significantly lower for encapsulated cells (8.64-15.03 %) compared to free cells (71.20 %). These results indicate that carrageenan-pectin gel beads with XC ≤ 0.25 were successful in encapsulating probiotic bacteria, and this capacity was related to the rheological and mechanical properties of the gels.

Symbiotic pectin microparticles with native Jerusalem artichoke (Helianthus tuberosus L.) enhance Lactobadllus paracasei subsp. tolerans survival / La encapsulación de Lactobacillus paracasei subsp. toleraos en microgeles de pectina con inulina extraída de topinambur (Helianthus tuberosus L.) incrementa su supervivencia

Resumen El efecto sinérgico de la microencapsulación en geles de pectina e inulina extraída de cultivos nativos de topinambur se evaluó como una estrategia natural para aumentar la supervivencia de Lactobacillus paracasei subsp. toleraos F2, bacteria seleccionada por sus propiedades probióticas sobre la trucha arco iris (Oncorhynchus mykiss). La cepa fue capaz de crecer y fermentar la inulina de topinambur en caldo MRS modificado, lo que condujo al incremento del número de células (~+5 unidades logarítmicas) y la disminución neta del pH (6,2 ±0,2 a 4,0±0,5). La encapsulación de F2 en microgeles de pectina en presencia de inulina mejoró su supervivencia no solo a lo largo del almacenamiento sino también en condiciones donde se simuló el pasaje por el tracto gastrointestinal. Después de 56 días de almacenamiento a 4 °C, se registraron números significativamente mayores de células viables microencapsuladas en presencia del prebiótico (8,2-8,4 log UFC/g) que sin él (~7,00 log UFC/g). Estos resultados alientan la aplicación de estas técnicas para la formulación de alimentos funcionales utilizando fuentes alternativas naturales de inulina que incrementan la viabilidad del probiótico almacenado y su digestibilidad.

Symbiotic pectin microparticles with native Jerusalem artichoke (Helianthus tuberosus L.) enhance Lactobacillus paracasei subsp. tolerans survival.

The synergistic effect of microencapsulation in pectin microgels and inulin extracted from native crops of Jerusalem artichoke (JAI) was evaluated as a natural strategy to increase the survival of Lactobacillus paracasei subsp. tolerans F2 selected for its probiotic properties in Oncorhynchus mykiss. The strain was able to grow and ferment JAI in modified MRS broth, increasing cell population (∼+5 log units) with a net decrease in pH (6.2±0.2 to 4.0±0.5). Encapsulation of F2 in pectin microgels in the presence of JAI improved the survival of the strain not only during storage but also after exposure to simulated gastrointestinal conditions. Viable entrapped cells in the presence of the prebiotic were significantly higher (8.2-8.4log CFU/g) than without it (∼7.00log CFU/g) after 56 days at 4°C. These results encourage further implementation of these techniques for the formulation of functional feeds using natural alternative sources of inulin with greater viability on storage conditions and digestibility.

Microencapsulation of Lactobacillus casei and Lactobacillus rhamnosus in pectin and pectin-inulin microgel particles: Effect on bacterial survival under storage conditions.

The main objective of the research was to evaluate the performance of synbiotic delivery systems using pectin microgels on the protection of two probiotic strains (Lactobacillus casei ATCC 393 and Lactobacillus rhamnosus strain GG [ATCC 53103]) to simulated gastrointestinal digestion (GD) and storage conditions (4 ± 1 °C) in a 42 days trial. Microgel particles were prepared by ionotropic gelation method and three variables were evaluated: incubation time (24 and 48 h), free vs encapsulated cells, and presence or absence of prebiotic (commercial and Jerusalem artichoke inulin). Results demonstrated an encapsulation efficiency of 96 ± 4% into particles with a mean diameter between 56 and 118 µm. The viability of encapsulated cells after 42 days storage stayed above 7 log units, being encapsulated cells in pectin-inulin microgels more resistant to GD compared to non-encapsulated cells or without prebiotics. In all cases incubation time influenced the strains' survival.

Structural and sensory analysis of compositionally optimized apple jellies enriched with dietary fibre compared to commercial apple jams.

The objective of this work was to optimize the formulation of apple jellies enriched with 3 g/100 g of dietary fibre and to compare them with commercial apple jams in terms of structural and organoleptic properties. With that aim, a fibre mix with one part of psyllium and three parts of other fibre variety (apple, bamboo or wheat) was added to apple jelly, and the rheological, mechanical and sensory properties, as well as colour and syneresis (water loss) of the samples at different storage times were studied, and compared to two commercial apple jams. Those properties did not suffer significant changes during 30 days of cold storage, meaning that the product was stable. The reduction of psyllium proportion in the fibre mix (from 1:1 to 1:3) reduced the gumminess of the fibre enriched jellies, keeping the syneresis at 0 g/100 g. The jelly enriched with apple and psyllium fibre was the most similar to commercial apple jams in terms of rheological and mechanical properties. Consumers acceptability of fibre enriched jellies was higher than 72%, being the jelly enriched with bamboo and psyllium fibre the closest to a commercial apple jam, which was the consumer's favourite.

Pectin Gels Enriched with Dietary Fibre forthe Development of Healthy Confectionery Jams.

The objective of this work is to evaluate the effect of the addition of dietary fibre from different sources (apple, bamboo, psyllium and wheat) and pectin mass fraction (0.4 and 0.5 g/100 g) on the physicochemical properties of pectin gels for the development of a novel, healthy product similar to a fruit confectionery jam. A mass fraction of 3 g/100 g fibre was added to each pectin gel in order to declare the final product as a source of fibre. It was evident that pectin content, type of fibre, and their interaction had a significant effect on the viscoelastic and mechanical properties, and syneresis (water loss) of the gels. Since syneresis of the gel with 0.4 g/100 g pectin was undesirably high, only studies of gels with 0.5 g/100 g pectin followed from this point forward. Fibre addition had a reinforcing effect on the viscoelastic properties of these gels (wheat>psyllium>bamboo>apple). Psyllium-enriched gels did not suffer any syneresis, although they showed an undesirable "gummy" property, caused by low fracturability, high cohesiveness and low hardness. Then, in order to improve the organoleptic properties of the gels, we combined fibre from different sources in pairs (1:1). In general, fibre combination decreased the viscoelastic properties of the gels. However, mixing psyllium with other fibre produced a desirable effect on the mechanical properties of the gels, keeping the syneresis at 0 g/100 g. This indicates that 0.5 g/100 g pectin and 1.5 g/100 g psyllium fibre with 1.5 g/100 g other fibre was the best formulation for the stability and texture of this product.

Inulin rich carbohydrates extraction from Jerusalem artichoke (Helianthus tuberosus L.) tubers and application of different drying methods.

In this study the operational extraction variables to obtain higher yields of inulin from Jerusalem artichoke tubers (JAT), as well as the optimal conditions to obtain a stable and dispersible powdered product by either spray or freeze drying, were studied. With this purpose, the powder yield, moisture content, water activity and flowability or products obtained by different experimental conditions were analyzed. Inulin rich carbohydrates (IRC) extraction was performed from lyophilized and ground tubers employing distilled hot water as solvent. It was proved that the solid:solvent ratio (S:S) was the critical variable in the extraction process, followed by temperature. Thus, the IRC extraction was optimal without ultrasound assistance, at 76°C, employing a S:S of 1:16, during 90min. In addition, the powder obtained by freeze-drying of the IRC extract showed advantages respect to powders obtained by spray-drying regarding the yield and considering that maltodextrin was not necessary as encapsulation agent. In another hand, spray drying process provided IRC powered materials with appropriate flow properties, and taking into account cost and time of production, this method should be considered as an alternative of freeze-drying.

In situ microstructure and rheological behavior of yeast biofilms from the juice processing industries.

The factors affecting the mechanical properties of biofilms formed by yeast species (Rhodotorula mucilaginosa, Candida krusei, C. kefyr and C. tropicalis) isolated from the juice processing industries have been investigated. Variables studied were: the food matrix (apple/pear juice), the sugar concentration (6/12 °Bx) and the hydrodynamic conditions (static/turbulent flow). A range of environmental cues were included as the mechanical properties of biofilms are complex. Yeast counts were significantly higher in turbulent flow compared with under static conditions. The thickness of the biofilm ranged from 38 to 148 µm, from static to turbulent flow. Yeast biofilms grown under turbulent flow conditions were viscoelastic with a predominant solid-like behavior and were structurally stronger than those grown under static conditions, indicating gel-type structures. Only the type of flow had a significant effect on [Formula: see text] and G*. Flow velocity and nutrient status modulated the biofilm thickness, the biomass and the mechanical properties. A better knowledge of the factors controlling biofilm formation will help in the development of control strategies.

In situ rheology of yeast biofilms.

The aim of the present work was to investigate the in situ rheological behavior of yeast biofilms growing on stainless steel under static and turbulent flow. The species used (Rhodototula mucilaginosa, Candida krusei, Candida kefyr and Candida tropicalis) were isolated from a clarified apple juice industry. The flow conditions impacted biofilm composition over time, with a predominance of C. krusei under static and turbulent flow. Likewise, structural variations occurred, with a tighter appearance under dynamic flow. Under turbulent flow there was an increase of 112 µm in biofilm thickness at 11 weeks (p < 0.001) and cell morphology was governed by hyphal structures and rounded cells. Using the in situ growth method introduced here, yeast biofilms were determined to be viscoelastic materials with a predominantly solid-like behavior, and neither this nor the G'0 values were significantly affected by the flow conditions or the growth time, and at large deformations their weak structure collapsed beyond a critical strain of about 1.5-5%. The present work could represent a starting point for developing in situ measurements of yeast rheology and contribute to a thin body of knowledge about fungal biofilm formation.

Pectin extraction from quince (Cydonia oblonga) pomace applying alternative methods: effect of process variables and preliminary optimization.

The objectives of this study were to introduce alternative methods in the process of pectin extraction from quince pomace, to determine the effect of selected process variables (factors) on the obtained pectin, and to perform a preliminary optimization of the process. A fractional factorial experimental design was applied, where the factors considered were six: quince pomace pretreatment (washing vs blanching), drying method (hot air vs LPSSD), acid extraction conditions (pH, temperature, and time), and pectin extract concentration method (vacuum evaporation vs ultrafiltration). The effects of these factors and their interactions on pectin yield (Y: 0.2-34.2 mg/g), GalA content (44.5-76.2%), and DM (47.5-90.9%), were determined. For these three responses, extraction pH was the main effect, but it was involved in two and three factors interactions. Regarding alternative methods, LPSSD was required for maximum Y and GalA, and ultrafiltration for maximum GalA and DM. Response models were used to predict optimum process conditions (quince blanching, pomace drying by LPSSD, acid extraction at pH 2.20, 80 , 3 h, and concentration under vacuum) to simultaneously maximize Y (25.2 mg/g), GalA (66.3%), and DM (66.4%).

Studies of pilocarpine:carbomer intermolecular interactions.

The interactions between pilocarpine (PIL) and the anionic polyelectrolyte carbomer (CBR) were investigated. The effects of the chemical interactions on the chemical stability of the drug also were evaluated. The binary system was characterized by nuclear magnetic resonance techniques, Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction, scanning electron microscopy (SEM) and thermal analysis. The experiments showed that the complex, prepared by freeze-drying, is a solid amorphous form different from its precursors, thereby offering an interesting alternative for the preparation of extended release matrices. The solution stability of PIL was studied at pH 7 and 8, at 70 °C. The PIL solution stability was evaluated alone and in the presence of CBR. Results indicated that the drug in the presence of the polymer is 3.3 and 3.5 times more stable, at pH 7 and pH 8, respectively, than the drug without CBR. The activation energy and the frequency factor, according to Arrhenius plot, were estimated to be 13.9 ± 0.4 and 14.8 ± 0.5 kcalmol(-1), and 6.1 ± 0.3 and 7.6 ± 0.3, with and without the polymer, respectively.

Shear rheology of hard-sphere, dispersed, and aggregated suspensions, and filler-matrix composites.

This paper reviews the shear rheology of suspensions of microscopic particles. The nature of interparticle forces determines the microstructure, and hence the deformation and flow behavior of suspensions. Consequently, suspensions were classified according to the resulting microstructure: hard-spheres, stabilized, or aggregated particles. This study begins with the most simple case: flowing suspensions of inert, rigid, monomodal spherical particles (called hard-spheres), at low shear rates. Even for inert particles, we reviewed the effect of several factors that produce deviations from this ideal case, namely: shear rate, particle shape, particle size distribution, and particle deformability. Then we moved to suspensions of colloidal particles, where interparticle forces play a significant role. First we studied the case of dispersed or stabilized suspensions (colloidal dispersions), where long range repulsive forces keep particles separated, leading to a crystalline order. Second we studied the more common case of aggregated or flocculated suspensions, where net attractive forces lead to the formation of fractal clusters. Above the gelation concentration (which depends on the magnitude of the attractive forces), clusters are interconnected into a network, forming a gel. We differentiate between weak and strong aggregation, which may lead to weak or strong gels, respectively. Finally, we reviewed the case of filler/matrix composite suspensions or gels, where rigid or viscoelastic particles (fillers) are dispersed in a continuous viscoelastic material (matrix), usually a gel. For each type of suspension, predictive curves of fundamental rheological properties (viscosity, yield stress, elastic and complex moduli) vs. particle volume fraction and shear rate were obtained from theoretical or empirical models and sound experimental data, covering ranges of practical interest.

Studies on trimethoprim:hydroxypropyl-ß-cyclodextrin: aggregate and complex formation.

The present study is focused on the characterization of the interaction between trimethoprim, a dihydropteroate synthesase inhibitor, and hydroxypropyl-ß-cyclodextrin (HP-ß-CD) in aqueous solution and solid state. The freeze-drying method was used to prepare solid complexes, while simple blending was employed to obtain physical mixtures. The phase solubility was AN type, and demonstrated that trimethoprim solubility was significantly increased upon complexation with HP-ß-CD. Conductivity experiments showed the presence of aggregates that explains the type profile for the solubility isotherm. The critical concentration for the aggregate formation was determined to be 69.3mg/ml for pure HP-ß-CD and 117.7 mg/ml in the presence of trimethoprim. Nuclear magnetic resonance spectroscopy provided evidence of trimethoprim:HP-ß-CD molecular interaction in solution. Moreover, the complex was characterized in solid stated using Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The use of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) showed that the thermal stability of the drug is enhanced in the presence of HP-ß-CD.