Effects of wettability and adhesion of solid-suspension and film-suspension systems on spouted bed coating performance

Orientador: Sandra Cristina dos Santos RochaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia QuímicaResumo: O recobrimento de partículas é uma operação presente em vários setores industriais e tem como objetivo modificar as propriedades de superfície influenciando diretamente na qualidade, estabilidade e proteção do produto final. O principal enfoque deste trabalho foi aprimorar o estudo de recobrimento em termos de tensão superficial do sólido e características de molhabilidade e adesão antes e após a formação da primeira camada de recobrimento sobre a partícula. Ensaios de recobrimento em leito de jorro foram conduzidos, empregando-se: cinco suspensões poliméricas aquosas que se diferenciaram quanto às propriedades físicas (concentração de sólidos, tensão superficial e reologia) e, como inertes, partículas arredondadas de vidro e ABS® (copolímero acrilonitrila butadieno estireno) com diferentes energias superficiais, gerando sistemas com distintas características de molhabilidade e adesão. Para caracterização do sistema filme-suspensão, duas metodologias (A e B) foram testadas recobrindo lâminas de vidro e de ABS® com uma fina camada de suspensão polimérica, e para os conjuntos sólido/película que produziram uma superfície lisa e homogênea, estes foram avaliados quanto ao ângulo de contato, assim como para o sistema sólido-suspensão. A eficiência do processo e a cinética de crescimento das partículas, para ambos os sólidos e as cinco formulações, foram determinadas em cada ensaio de recobrimento e, buscou-se relacionar os resultados às características de superfície. A alta energia superficial do vidro exerceu grande influência sobre os sistemas sólido-suspensão e filme-suspensão, resultando em baixos valores de ângulo de contato. Devido à menor energia superficial do ABS®, a receptividade do sólido pelas suspensões foi menor, resultando em maiores valores de ângulo de contato e menores valores de trabalho de adesão. As forças de adesão diminuíram com o aumento da espessura do filme, porém, todos os valores de ângulo de contato se mantiveram abaixo de 70º, indicando boa molhabilidade e condições para o recobrimento. Os valores de eficiência se mantiveram acima de 60 %, e todos os valores de desvio médio para as duplicatas, abaixo de 10 %, indicando boa eficiência e reprodutibilidade do processo. A cinética de crescimento das partículas não apresentou diferença de comportamento após a formação da primeira camada de recobrimento, como poderia ser previsto pela alteração na molhabilidade após a formação do filme sobre a partículaAbstract: Particle coating is an operation used in several industrial sectors and aims to modify the particle surface properties directly influencing the quality, stability and protection of the final product. The main focus of this work was to improve particle coating analyses in terms of the solid surface tension, wettability and adhesion characteristics before and after the formation of the first layer of coating on the particle. Testing of coating in spouted bed were conducted using five aqueous polymeric suspensions that differed in terms of physical properties (solids concentration, surface tension and rheology), and as nucleus, rounded particles of glass and ABS® with different energies surface, generating systems with different characteristics of wettability and adhesion. To characterize the film-suspension system, two methods (A and B) were tested covering blades of glass and ABS® with a thin layer of the polymer suspension. Contact angles were evaluated for the solid-suspension systems and for the solid/film sets where a smooth and homogeneous surface was produced. The process efficiency and growth kinetics of particles, for both solids and five formulations were determined in each coating test, and the results were related to surface characteristics. The high surface energy of the glass had a great influence on the solid-suspension and film-suspension systems, resulting in low values of contact angle. Due to the lower surface energy of ABS®, the receptivity of the suspension by the solid was lower, resulting in higher values of contact angle and lower values of work of adhesion. The adhesive forces decreased with increasing film thickness; however, all values of contact angle remained below 70 °, indicating good wettability and conditions for efficient coating. Coating efficiencies remained above 60%, and all values of mean deviation for duplicates, below 10%, indicating good efficiencies and reproducibility of the process. The growth kinetics of the particles showed no difference in behavior after the formation of the first covering layer, as could be predicted by the change in wettability after the film formation on the particleMestradoEngenharia de ProcessosMestre em Engenharia Químic

Bioaccessibility and antioxidant activity of anthocyanins from jaboticaba skins: the influence of OSA-modified starch concentration

In recent years, there has been a growing interest in clarifying the metabolism of bioactive compounds, particularly phenolics such as anthocyanins. The transformation of anthocyanins from jaboticaba throughout digestion has yet to be extensively investigated. Due to native-form anthocyanins' instability against environmental stress, bioactive compounds are not always as effective in improving human health as they could be. The microencapsulation of material with high levels of anthocyanins by freeze-drying usually results in products with greater stability during storage, preserving their antioxidant properties. Therefore, the main goal of the present study was to determine the bioaccessibility of anthocyanins in jaboticaba powder samples to evaluate the effects of the modified starch with octenyl succinic anhydride (OSA) concentration (10% of adjuvant (PA), jaboticaba powder with 15% of adjuvant (PB), jaboticaba powder with 20% of adjuvant (PC), jaboticaba powder with 25% of adjuvant (PD)) using a static in vitro model of digestion over the anthocyanin’s contents and their antioxidant activities. Based on the results, it is possible to observe a decrease in anthocyanin content after the simulated digestive process. Before the digestion, the anthocyanins concentration values ranged from 94.30e ± 4.1 to 257.95a ± 22.8 ug/mL of cyanidin 3-glucoside. The highest concentration was found on jabuticaba pulp (JP) and the lowest on jaboticaba powder with 25% OSA-modified starch (PD). However, after the in vitro digestion, the loss of anthocyanins was more accentuated in the samples JP, PC, and PD. The bioaccessible anthocyanins varied from 5.30 (PC) to 9.58 (PB). Therefore, the PB sample presented the best results among the studied in the present work. The interaction between adjuvant and bioactive compounds promoted the protection of bioactive compounds against adverse digestion conditions, considering the maintenance of antioxidant activity

Mixtures of Modified Starch and Rice and Pea Protein Concentrate as Wall Material in the Microencapsulation of Flaxseed Oil

Flaxseed oil is rich in polyunsaturated fatty acids, and its incorporation into food formulations is limited due to its hydrophobic nature and susceptibility to oxidation. The aim of this work was to analyze the effect of wall material mixtures (modified starch Capsul® and rice and pea protein concentrate) on the efficiency of flaxseed oil encapsulation by freeze-drying, physical characterization, and determining oxidative stability. For the preparation of powders, four emulsions with an oil–wall material ratio of 1:3 were produced and characterized. The mass ratio between rice and pea proteins was fixed at 50–50%. The mass ratio of the protein-Capsul® mixtures was varied by 0–100%, 10–90%, 20–80%, and 30–70%. Based on the creaming index results, all emulsions showed good stability after 24 h of analysis. The powders showed low moisture content (® ratio of 0–100%) to 18.26% (protein-Capsul® ratio of 30–70%). However, the best oxidative stability results (smaller increases in the peroxide index values at the end of the stability experiments) were obtained for the powders containing the highest levels of vegetable proteins (protein-Capsul® ratio of 20–80% and 30–70%, respectively)