Ana Carla Kawazoe Sato

Preparation, characterization and in vitro digestibility of gellan and chitosan–gellan microgels

Gellan microgels with potential application in delivery systems were obtained by physically cross-linked gellan gum. The microgels were produced by atomization followed by ionotropic gelation using CaCl2 (gellan/Ca) or KCl (gellan/K) as hardening agent and part of them were coated with chitosan in order to improve their resistance to gastric digestion. Size distribution, morphology and zeta potential of microgels were evaluated before and after in vitro digestion process. The long term stability was also evaluated. Spherical microparticles were obtained at gellan concentration above 0.6% w/w, showing average size among 70-120 μm. Most of the coated and uncoated microgels showed stability in aqueous media, except the uncoated gellan/K microgel. The in vitro digestion evaluation showed that all particles maintained their size and shape after the gastric digestion step. However, the enteric digestion caused disintegration of microgels indicating their potential application for enteric delivery systems. The chitosan-coated microgels showed lower degree of fragmentation when compared to the uncoated microgels, indicating that the coating process enable a better control of microgels releasing properties during the enteric digestion.

Cross-linking proteins by laccase: Effects on the droplet size and rheology of emulsions stabilized by sodium caseinate

The aim of this work was to evaluate the influence of laccase and ferulic acid on the characteristics of oil-in-water emulsions stabilized by sodium caseinate at different pH (3, 5 and 7). Emulsions were prepared by high pressure homogenization of soybean oil with sodium caseinate solution containing varied concentrations of laccase (0, 1 and 5mg/mL) and ferulic acid (5 and 10mM). Laccase treatment and pH exerted a strong influence on the properties with a consequent effect on stability, structure and rheology of emulsions stabilized by Na-caseinate. At pH7, O/W emulsions were kinetically stable due to the negative protein charge which enabled electrostatic repulsion between oil droplets resulting in an emulsion with small droplet size, low viscosity, pseudoplasticity and viscoelastic properties. The laccase treatment led to emulsions showing shear-thinning behavior as a result of a more structured system. O/W emulsions at pH5 and 3 showed phase separation due to the proximity to protein pI, but the laccase treatment improved their stability of emulsions especially at pH3. At pH3, the addition of ferulic acid and laccase produced emulsions with larger droplet size but with narrower droplet size distribution, increased viscosity, pseudoplasticity and viscoelastic properties (gel-like behavior). Comparing laccase treatments, the combined addition of laccase and ferulic acid generally produced emulsions with lower stability (pH5), larger droplet size (pH3, 5 and 7) and higher pseudoplasticity (pH5 and 7) than emulsion with only ferulic acid. The results suggested that the cross-linking of proteins by laccase and ferulic acid improved protein emulsifying properties by changing functional mechanisms of the protein on emulsion structure and rheology, showing that sodium caseinate can be successfully used in acid products when treated with laccase.

Effect of process variables on the osmotic dehydration of star-fruit slices

The objective of this work was to study the effect of blanching and the influence of temperature, solution concentration, and the initial fruit:solution ratio on the osmotic dehydration of star-fruit slices. For blanching, different concentrations of citric and ascorbic acids were studied. The samples immersed in 0.75% citric acid presented little variation in color in relation to the fresh star-fruit. Osmotic dehydration was carried out in an incubator with orbital shaking, controlled temperature, and constant shaking at 120 rpm. The influence of process variables was studied in trials defined by a complete 23 central composite design. In general, water loss and solids gain were positively influenced by temperature and by solution concentration. Nevertheless, lower temperatures reduced water loss throughout the osmotic dehydration process. An increase in the amount of dehydrating solution (initial fruit:solution ratio) slightly influenced the evaluated responses. The process carried out at 50 oC with a solution concentration of 50% resulted in a product with lower solids gain and greater water loss. Under these conditions, blanching minimized the effect of the osmotic treatment on star-fruit browning, and therefore the blanched fruits showed little variation in color in relation to the fresh fruit.

Avaliação das propriedades físicas, químicas e sensorial de preferência de goiabas em calda industrializadas

Quatro marcas de goiabas em calda foram submetidas a analises fisico-quimicas, de cor e textura instrumentais e teste sensorial de preferencia, a fim de avaliar as diferencas entre os produtos comerciais. As mesmas analises foram efetuadas em uma goiaba in natura madura, a fim de avaliar os possiveis efeitos do processamento na qualidade do produto. De maneira geral, observou-se grandes diferencas entre os produtos das diferentes marcas, e muitas vezes entre os frutos de um mesmo fabricante. As analises quimicas mostraram que o teor de acucares da maior parte dos produtos esta entre 22 e 30%, com excecao de uma amostra que mostrou um valor bem mais elevado (ao redor de 40%). A analise sensorial mostrou que esta amostra com maior teor de acucares foi a mais preferida em relacao a docura. Na analise de cor foram observados menores valores de a* em relacao a fruta in natura, possivelmente devido a degradacao dos carotenoides da goiaba. A luminosidade das goiabas em calda tambem e maior que da fruta in natura, devido a presenca dos acucares. Esta entrada de acucares na fruta junto com o processamento termico utilizado pode ter causado possivel gelificacao da pectina, aumentando a dureza, firmeza e elasticidade de algumas amostras processadas, quando comparadas a fruta fresca. No entanto, em alguns casos foi visivel o efeito de processamentos mais drasticos, que levaram a perda da estrutura celular, observada pelos baixos valores das propriedades mecânicas. Em relacao a textura e aparencia, a amostra mais dura foi a preferida.

Influence of Dispersing Media and Particle Characteristics on Rheological Behavior of Noncolloidal Suspensions

The effect of viscosity (high and low) and molecular characteristics (polar and nonpolar) of continuous matrix on the flow behavior of noncolloidal suspensions were evaluated using particles with different size and shape. The increase in solids volume fraction exerted higher influence for larger cellulose fibers and less viscous matrices, due to larger particle-particle interaction. Evaluation of matrix polarity allowed the assessment of particle-solvent interactions, indicating that higher swelling of particles dispersed in polar matrices led to more complex and viscous suspensions. Besides particle characteristics, suspending matrix properties influenced the rheological behavior of noncolloidal suspensions, despite of the prevailing hydrodynamics effects.

Utilization of Plant Dietary Fibers to Reinforce Low-Calorie Dairy Dessert Structure

Effect of plant fibers, carrageenan, and starch concentration on mechanical properties and syneresis measurements of low-calorie dairy desserts was studied simultaneously using the response surface methodology. Apple, bamboo, inulin, wheat, and psyllium fibers were tested individually, through five distinct experimental designs. Results were compared to a regular dairy dessert, formulated with sugar and whole milk, and a low-calorie formulation with no added fiber. Diet dessert with no added fiber presented higher syneresis and impaired mechanical properties as compared to regular formulation. Results showed that carrageenan, starch, and fibers played distinct roles in compensating the reduction observed on the syneresis test and mechanical properties of low-calorie desserts. While carrageenan and starch showed higher influence on reducing gel syneresis, fiber addition decreased the negative effect on mechanical properties resulting from the fat/sugar removal of the diet formulation.

Biopolymer gels containing fructooligosaccharides

The influence of the addition of fructooligosaccharide (FOS) in an external gelated alginate/gelatin biopolymer matrix, was evaluated in order to produce biopolymeric structures with functional effects. Solutions were characterized regarding their rheological properties, macrogels regarding their microstructure and mechanical properties and microgels were characterized in relation to their particle size distribution and morphology. Close relationship was found between the microstructure, rheological and mechanical properties of the biopolymeric systems. An increased viscosity and accentuated elastic and pseudoplastic behavior were associated to denser microstructures. The FOS addition caused changes in the evaluated properties, resulting in more cohesive structures, with smaller pores and higher viscosity, compared to alginate-gelatin gels. The addition of 3% FOS to biopolymeric system provided an optimal condition, allowing the formation of stronger gels, with smaller pores and beads with smaller sizes, indicating the potential use of these functional systems as texture modifiers or encapsulation systems.

Gelled Double-Layered Emulsions for Protection of Flaxseed Oil

Multilayer systems may present different functional properties according to the number of layers deposited, the type of biopolymers, the sequence of biopolymer layers, and the solution properties used during deposition. In this study, gelatin-stabilized emulsions were coated with alginate in order to produce double-layered emulsions. Concentrations of both primary emulsion and alginate in the outer layer were evaluated by a stability map. Results indicated the occurrence of depletion flocculation in emulsions with lower gelatin concentration due to excess of alginate. Stable emulsions were atomized in a calcium chloride solution for producing microgels, which resulted in semi-rounded monomodal particles. Emulsification process promoted a reduction in the content of the secondary oxidation products of flaxseed oil as compared to non-emulsified oil, while the gelation process was responsible for a considerable improvement on oxidative stability with significant reduction on both primary and secondary oxidation products during storage. These lipid-based microgels could be potentially used as delivery systems with improved oxidative stability.

Adding symbiotic microgels in dairy products: assessment of the stability and viability

The structure of the encapsulating matrices for bioactive incorporation as well as the environment in which these capsules are added are critical in the protection and release of the encapsulated compounds. This study investigated the stability and release of probiotics incorporated in a gelatin-alginate microbeads with and without prebiotic during shelf life and simulated in vitro digestion when incorporated into dairy foods with different rheological characteristics.